davila

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Author name code: davila
ADS astronomy entries on 2022-09-14
author:"Davila, Joseph"

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Title: Coordination within the remote sensing payload on the Solar
Orbiter mission
Authors: Auchère, F.; Andretta, V.; Antonucci, E.; Bach, N.;
Battaglia, M.; Bemporad, A.; Berghmans, D.; Buchlin, E.; Caminade,
S.; Carlsson, M.; Carlyle, J.; Cerullo, J. J.; Chamberlin, P. C.;
Colaninno, R. C.; Davila, J. M.; De Groof, A.; Etesi, L.; Fahmy,
S.; Fineschi, S.; Fludra, A.; Gilbert, H. R.; Giunta, A.; Grundy,
T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.;
Howard, R. A.; Hurford, G.; Kleint, L.; Kolleck, M.; Krucker, S.;
Lagg, A.; Landini, F.; Long, D. M.; Lefort, J.; Lodiot, S.; Mampaey,
B.; Maloney, S.; Marliani, F.; Martinez-Pillet, V.; McMullin, D. R.;
Müller, D.; Nicolini, G.; Orozco Suarez, D.; Pacros, A.; Pancrazzi,
M.; Parenti, S.; Peter, H.; Philippon, A.; Plunkett, S.; Rich, N.;
Rochus, P.; Rouillard, A.; Romoli, M.; Sanchez, L.; Schühle, U.;
Sidher, S.; Solanki, S. K.; Spadaro, D.; St Cyr, O. C.; Straus, T.;
Tanco, I.; Teriaca, L.; Thompson, W. T.; del Toro Iniesta, J. C.;
Verbeeck, C.; Vourlidas, A.; Watson, C.; Wiegelmann, T.; Williams,
D.; Woch, J.; Zhukov, A. N.; Zouganelis, I.
2020A&A...642A...6A Altcode:
Context. To meet the scientific objectives of the mission, the Solar
Orbiter spacecraft carries a suite of in-situ (IS) and remote sensing
(RS) instruments designed for joint operations with inter-instrument
communication capabilities. Indeed, previous missions have shown that
the Sun (imaged by the RS instruments) and the heliosphere (mainly
sampled by the IS instruments) should be considered as an integrated
system rather than separate entities. Many of the advances expected
from Solar Orbiter rely on this synergistic approach between IS and
RS measurements. Aims: Many aspects of hardware development,
integration, testing, and operations are common to two or more
RS instruments. In this paper, we describe the coordination effort
initiated from the early mission phases by the Remote Sensing Working
Group. We review the scientific goals and challenges, and give an
overview of the technical solutions devised to successfully operate
these instruments together. Methods: A major constraint for the
RS instruments is the limited telemetry (TM) bandwidth of the Solar
Orbiter deep-space mission compared to missions in Earth orbit. Hence,
many of the strategies developed to maximise the scientific return from
these instruments revolve around the optimisation of TM usage, relying
for example on onboard autonomy for data processing, compression,
and selection for downlink. The planning process itself has been
optimised to alleviate the dynamic nature of the targets, and an
inter-instrument communication scheme has been implemented which can
be used to autonomously alter the observing modes. We also outline the
plans for in-flight cross-calibration, which will be essential to the
joint data reduction and analysis. Results: The RS instrument
package on Solar Orbiter will carry out comprehensive measurements
from the solar interior to the inner heliosphere. Thanks to the close
coordination between the instrument teams and the European Space
Agency, several challenges specific to the RS suite were identified
and addressed in a timely manner.

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Title: Models and data analysis tools for the Solar Orbiter mission
Authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.;
Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.;
Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.;
Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi,
N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla,
T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.;
Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.;
Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.;
Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.;
Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot,
V.; Georgoulis, M. K.; Gilbert, H. R.; Giunta, A.; Gomez-Herrero, R.;
Guest, S.; Haberreiter, M.; Hassler, D.; Henney, C. J.; Howard, R. A.;
Horbury, T. S.; Janvier, M.; Jones, S. I.; Kozarev, K.; Kraaikamp,
E.; Kouloumvakos, A.; Krucker, S.; Lagg, A.; Linker, J.; Lavraud,
B.; Louarn, P.; Maksimovic, M.; Maloney, S.; Mann, G.; Masson, A.;
Müller, D.; Önel, H.; Osuna, P.; Orozco Suarez, D.; Owen, C. J.;
Papaioannou, A.; Pérez-Suárez, D.; Rodriguez-Pacheco, J.; Parenti,
S.; Pariat, E.; Peter, H.; Plunkett, S.; Pomoell, J.; Raines, J. M.;
Riethmüller, T. L.; Rich, N.; Rodriguez, L.; Romoli, M.; Sanchez,
L.; Solanki, S. K.; St Cyr, O. C.; Straus, T.; Susino, R.; Teriaca,
L.; del Toro Iniesta, J. C.; Ventura, R.; Verbeeck, C.; Vilmer, N.;
Warmuth, A.; Walsh, A. P.; Watson, C.; Williams, D.; Wu, Y.; Zhukov,
A. N.
2020A&A...642A...2R Altcode:
Context. The Solar Orbiter spacecraft will be equipped with a wide
range of remote-sensing (RS) and in situ (IS) instruments to record
novel and unprecedented measurements of the solar atmosphere and
the inner heliosphere. To take full advantage of these new datasets,
tools and techniques must be developed to ease multi-instrument and
multi-spacecraft studies. In particular the currently inaccessible
low solar corona below two solar radii can only be observed
remotely. Furthermore techniques must be used to retrieve coronal
plasma properties in time and in three dimensional (3D) space. Solar
Orbiter will run complex observation campaigns that provide interesting
opportunities to maximise the likelihood of linking IS data to their
source region near the Sun. Several RS instruments can be directed
to specific targets situated on the solar disk just days before
data acquisition. To compare IS and RS, data we must improve our
understanding of how heliospheric probes magnetically connect to the
solar disk. Aims: The aim of the present paper is to briefly
review how the current modelling of the Sun and its atmosphere
can support Solar Orbiter science. We describe the results of a
community-led effort by European Space Agency's Modelling and Data
Analysis Working Group (MADAWG) to develop different models, tools,
and techniques deemed necessary to test different theories for the
physical processes that may occur in the solar plasma. The focus here
is on the large scales and little is described with regards to kinetic
processes. To exploit future IS and RS data fully, many techniques have
been adapted to model the evolving 3D solar magneto-plasma from the
solar interior to the solar wind. A particular focus in the paper is
placed on techniques that can estimate how Solar Orbiter will connect
magnetically through the complex coronal magnetic fields to various
photospheric and coronal features in support of spacecraft operations
and future scientific studies. Methods: Recent missions such as
STEREO, provided great opportunities for RS, IS, and multi-spacecraft
studies. We summarise the achievements and highlight the challenges
faced during these investigations, many of which motivated the Solar
Orbiter mission. We present the new tools and techniques developed
by the MADAWG to support the science operations and the analysis of
the data from the many instruments on Solar Orbiter. Results:
This article reviews current modelling and tool developments that ease
the comparison of model results with RS and IS data made available
by current and upcoming missions. It also describes the modelling
strategy to support the science operations and subsequent exploitation
of Solar Orbiter data in order to maximise the scientific output
of the mission. Conclusions: The on-going community effort
presented in this paper has provided new models and tools necessary
to support mission operations as well as the science exploitation of
the Solar Orbiter data. The tools and techniques will no doubt evolve
significantly as we refine our procedure and methodology during the
first year of operations of this highly promising mission.

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Title: The Solar Orbiter SPICE instrument. An extreme UV imaging
spectrometer
Authors: SPICE Consortium; Anderson, M.; Appourchaux, T.; Auchère, F.;
Aznar Cuadrado, R.; Barbay, J.; Baudin, F.; Beardsley, S.; Bocchialini,
K.; Borgo, B.; Bruzzi, D.; Buchlin, E.; Burton, G.; Büchel, V.;
Caldwell, M.; Caminade, S.; Carlsson, M.; Curdt, W.; Davenne, J.;
Davila, J.; Deforest, C. E.; Del Zanna, G.; Drummond, D.; Dubau,
J.; Dumesnil, C.; Dunn, G.; Eccleston, P.; Fludra, A.; Fredvik, T.;
Gabriel, A.; Giunta, A.; Gottwald, A.; Griffin, D.; Grundy, T.; Guest,
S.; Gyo, M.; Haberreiter, M.; Hansteen, V.; Harrison, R.; Hassler,
D. M.; Haugan, S. V. H.; Howe, C.; Janvier, M.; Klein, R.; Koller,
S.; Kucera, T. A.; Kouliche, D.; Marsch, E.; Marshall, A.; Marshall,
G.; Matthews, S. A.; McQuirk, C.; Meining, S.; Mercier, C.; Morris,
N.; Morse, T.; Munro, G.; Parenti, S.; Pastor-Santos, C.; Peter, H.;
Pfiffner, D.; Phelan, P.; Philippon, A.; Richards, A.; Rogers, K.;
Sawyer, C.; Schlatter, P.; Schmutz, W.; Schühle, U.; Shaughnessy,
B.; Sidher, S.; Solanki, S. K.; Speight, R.; Spescha, M.; Szwec, N.;
Tamiatto, C.; Teriaca, L.; Thompson, W.; Tosh, I.; Tustain, S.; Vial,
J. -C.; Walls, B.; Waltham, N.; Wimmer-Schweingruber, R.; Woodward,
S.; Young, P.; de Groof, A.; Pacros, A.; Williams, D.; Müller, D.
2020A&A...642A..14S Altcode: 2019arXiv190901183A; 2019arXiv190901183S
 Aims: The Spectral Imaging of the Coronal Environment (SPICE)
instrument is a high-resolution imaging spectrometer operating at
extreme ultraviolet wavelengths. In this paper, we present the concept,
design, and pre-launch performance of this facility instrument on the
ESA/NASA Solar Orbiter mission. Methods: The goal of this paper
is to give prospective users a better understanding of the possible
types of observations, the data acquisition, and the sources that
contribute to the instrument's signal. Results: The paper
discusses the science objectives, with a focus on the SPICE-specific
aspects, before presenting the instrument's design, including optical,
mechanical, thermal, and electronics aspects. This is followed by a
characterisation and calibration of the instrument's performance. The
paper concludes with descriptions of the operations concept and data
processing. Conclusions: The performance measurements of the
various instrument parameters meet the requirements derived from the
mission's science objectives. The SPICE instrument is ready to perform
measurements that will provide vital contributions to the scientific
success of the Solar Orbiter mission.

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Title: Improving Coronal Magnetic Field Models Using Image
Optimization
Authors: Jones, Shaela I.; Uritsky, Vadim M.; Davila, Joseph M.;
Troyan, Vladimir N.
2020ApJ...896...57J Altcode:
We have reported previously on our development and testing of a
new method for using coronal images to improve coronal magnetic
field models. In this technique, which we call image-optimization,
coronal magnetic field models are extrapolated from synoptic
photospheric magnetograms. The resulting models are then compared to
morphological constraints derived from images of the solar corona,
and the photospheric magnetograms are perturbed iteratively via an
optimization algorithm to achieve optimal agreement with the image-based
constraints. Here we present results from the first application of
this technique using Mauna Loa Solar Observatory K-Coronagraph images
and Global Oscillation Network Group synoptic magnetograms to create
optimized models for two time periods, 2014 November 16-29 and 2016 May
16-29. We find that for both time periods the optimization algorithm
converges well and results in better agreement between the model and
the images, relatively small changes to the synoptic magnetogram,
and an overall increase in the amount of open magnetic flux.

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Title: Coronal Magnetic Field Model Selection Using Images of the
Middle Corona and Solar Wind Measurements
Authors: Jones, S. I.; Arge, C. N.; Uritsky, V. M.; Henney, C. J.;
Davila, J. M.; Staeben, J. H.
2019AGUFMSH13A..08J Altcode:
In order to understand the dynamic processes taking place in the middle
corona, we need a way of accurately modeling it. Numerous models are
available - as well as multiple sources of boundary conditions from
which to build those models - but limited measurements are available
with which to compare them. Available data on the middle corona
consist of images and spectroscopic measurements from a highly limited
number of vantage points, and these data can be difficult to compare
quantitatively with models. Recently we have developed a method
for such a quantitative image-model comparison using measurements from
the K-Cor and STEREO COR-1 coronagraphs. We have also devised a new
method for quantitative assessment of different synoptic map inputs
based on comparison between WSA solar wind predictions and in situ
data. Here we detail the two methods and compare their results.

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Title: Slitless Solar Imaging Spectroscopy
Authors: Davila, Joseph M.; Oktem, Figen S.; Kamalabadi, Farzad
2019ApJ...883....7D Altcode:
Spectrometers provide our most detailed diagnostics of the solar
coronal plasma, and spectral data is routinely used to measure the
temperature, density, and flow velocity in coronal features. However,
spectrographs suffer from a limited instantaneous field of view
(IFOV). Conversely, imaging instruments can provide a relatively large
IFOV, but extreme-ultraviolet (EUV) multilayer imaging offers very
limited spectral resolution. In this paper, we suggest an instrument
concept that combines the large IFOV of an imager with the diagnostic
capability of a spectrograph, develop a new parametric model to describe
the instrument, and evaluate a new method for “deconvolving” the
data from such an instrument. To demonstrate the operating principle of
this new slitless spectroscopy instrument, actual spectroscopic raster
data from the Hinode/EUV Imaging Spectrometer (EIS) spectrometer is
used. We assume that observations in multiple spectral orders are
obtained, and then use a new inverse problem method to infer the
spectral properties. Unlike previous methods, physical constraints
and regularization derived from prior knowledge can be naturally
incorporated as part of the solution process. We find that the fidelity
of the solution is vastly improved compared to previous methods. The
errors are typically only a few km s-1 over a large
IFOV, with a width of a few hundred pixels and an arbitrarily large
height. These errors are not much larger than the errors in current
slit spectroscopic instruments with limited IFOV. A further benefit
is that the performance of candidate instruments can be optimized
for specific scientific objectives. We demonstrate this by deriving
optimum values for the spectral dispersion and signal-to-noise ratio.

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Title: Effect of Transport Coefficients on Excitation of Flare-induced
Standing Slow-mode Waves in Coronal Loops
Authors: Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Solanki, Sami K.;
Davila, Joseph M.
2018ApJ...860..107W Altcode: 2018arXiv180503282W
Standing slow-mode waves have been recently observed in flaring loops by
the Atmospheric Imaging Assembly of the Solar Dynamics Observatory. By
means of the coronal seismology technique, transport coefficients in
hot (∼10 MK) plasma were determined by Wang et al., revealing that
thermal conductivity is nearly suppressed and compressive viscosity is
enhanced by more than an order of magnitude. In this study, we use 1D
nonlinear MHD simulations to validate the predicted results from the
linear theory and investigate the standing slow-mode wave excitation
mechanism. We first explore the wave trigger based on the magnetic
field extrapolation and flare emission features. Using a flow pulse
driven at one footpoint, we simulate the wave excitation in two types
of loop models: Model 1 with the classical transport coefficients and
Model 2 with the seismology-determined transport coefficients. We
find that Model 2 can form the standing wave pattern (within about
one period) from initial propagating disturbances much faster than
Model 1, in better agreement with the observations. Simulations of
the harmonic waves and the Fourier decomposition analysis show that
the scaling law between damping time (τ) and wave period (P) follows
τ ∝ P 2 in Model 2, while τ ∝ P in Model 1. This
indicates that the largely enhanced viscosity efficiently increases
the dissipation of higher harmonic components, favoring the quick
formation of the fundamental standing mode. Our study suggests that
observational constraints on the transport coefficients are important
in understanding both the wave excitation and damping mechanisms.

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Title: Evaluating Uncertainties in Coronal Electron Temperature
and Radial Speed Measurements Using a Simulation of the Bastille
Day Eruption
Authors: Reginald, Nelson; St. Cyr, Orville; Davila, Joseph;
Rastaetter, Lutz; Török, Tibor
2018SoPh..293...82R Altcode:
Obtaining reliable measurements of plasma parameters in the Sun's
corona remains an important challenge for solar physics. We previously
presented a method for producing maps of electron temperature and
speed of the solar corona using K-corona brightness measurements made
through four color filters in visible light, which were tested for
their accuracies using models of a structured, yet steady corona. In
this article we test the same technique using a coronal model of the
Bastille Day (14 July 2000) coronal mass ejection, which also contains
quiet areas and streamers. We use the coronal electron density,
temperature, and flow speed contained in the model to determine two
K-coronal brightness ratios at (410.3, 390.0 nm) and (423.3, 398.7
nm) along more than 4000 lines of sight. Now assuming that for real
observations, the only information we have for each line of sight are
these two K-coronal brightness ratios, we use a spherically symmetric
model of the corona that contains no structures to interpret these
two ratios for electron temperature and speed. We then compare the
interpreted (or measured) values for each line of sight with the
true values from the model at the plane of the sky for that same line
of sight to determine the magnitude of the errors. We show that the
measured values closely match the true values in quiet areas. However,
in locations of coronal structures, the measured values are predictably
underestimated or overestimated compared to the true values, but can
nevertheless be used to determine the positions of the structures
with respect to the plane of the sky, in front or behind. Based on our
results, we propose that future white-light coronagraphs be equipped
to image the corona using four color filters in order to routinely
create coronal maps of electron density, temperature, and flow speed.

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Title: Ultrahigh-Resolution Solar Imaging with Diffractive Optics
Authors: Rabin, Douglas; Davila, Joseph M.; Daw, Adrian Nigel; Denis,
Kevin; Shah, Neerav; Mason, Emily; Novo-Gradac, Anne-Marie; Widmyer,
Thomas
2018tess.conf40443R Altcode:
Extreme ultraviolet (EUV) and soft X-ray (SXR) telescopes rarely achieve
diffraction-limited performance because conventional reflective optics
of the required size typically cannot be manufactured to the requisite
figure accuracy. Diffractive optics can overcome the angular-resolution
limitations of EUV/SXR mirrors but present other design and performance
challenges. A diffractive telescope is well-suited for probing for the
first time the expected energy dissipation scales of the solar corona
(&lt;100 km). We have previously described the fabrication of photon
sieves and Fresnel zone plates as large as 80-mm clear aperture,
as well as laboratory measurements and vibration testing. Here we
report on the design of more efficient phase zone plates, the path
to larger apertures, and our approach to a virtual telescope based on
formation-flying smallsats.

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Title: Evaluating Uncertainties in Coronal Electron Temperature and
Radial Speed Measurements Using a Simulation of the Bastille-Day
Eruption
Authors: Reginald, Nelson Leslie; St Cyr, O. C.; Davila, Joseph M.;
Rastaetter, Lutz; Torok, Tibor
2018tess.conf10410R Altcode:
Obtaining reliable measurements of plasma parameters in the Sun's corona
remains an important challenge for solar physics. We have previously
conducted field experiments using MACS and ISCORE instruments to create
maps of electron temperature and speed in the plane of the sky of
the solar corona using K-corona brightness measurements made through
four color filters in visible light. These instrumental techniques
were tested for their accuracy by conducting synthetic observations
on models that contained streamers and quiet areas and results were
presented in (Reginald et al., 2014, Solar Phys., 289, 2021). Here,
we present similar results from conducting synthetic observations
on a coronal model of the Bastille-Day (July 14, 2000) coronal mass
ejection that also contains streamers and quiet regions. We use the
coronal electron density, temperature, and flow speed contained in
the Bastille-Day model to determine two K-coronal brightness ratios at
(410.0, 390.0 nm) and (423.3, 398.7 nm) along more than 4000 lines of
sight on eight select frames. Now assuming that, for real observations,
the only information we have for each line of sight are these two
K-coronal brightness ratios, we then use a spherically symmetric model
of the corona that contains no structures to interpret these two ratios
for electron temperature and speed in the plane of the sky. Finally,
for each line of sight, we compare the interpreted (or measured)
value with the true value from the Bastille-Day model in the plane
of the sky to determine the magnitude of the error. An example of the
three step process applied on one frame in the Bastille-Day model is
shown in the image. We show that the measured values closely match
the true values in quiet areas. However, in locations of coronal
structures the measured values are predictably underestimated or
overestimated over the true values, but can nevertheless be used to
determine the positions of the structures with respect to the plane
of the sky, in front or behind. Our results show the potential for
future white-light coronagraphs be equipped with four color filters
instead of the customary single filter to produce synoptic maps of
electron density, temperature and flow speed in the plane of the sky.

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Title: Excitation and Damping of Standing Slow-Mode Waves in Flaring
Coronal Loops
Authors: Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Solanki, Sami K.;
Davila, Joseph M.
2018tess.conf22204W Altcode:
We analyze and model a flare-induced longitudinal oscillation event
detected by SDO/AIA. The magnetic field extrapolation and flare emission
features suggest that the wave event is generated by slipping and
null-point-type reconnections in a closed fan-spine magnetic topology,
and the large spine loop appears to be heated impulsively to the flare
temperature before the wave disturbances travel along it. By means of
the seismology technique, we determined the transport coefficients
in hot (about 10 MK) plasma, and found that thermal conductivity is
nearly suppressed and compressive viscosity is enhanced by more than
an order of magnitude from the observed wave properties. Using a flow
pulse injected at the loop's footpoint constrained by the observation,
we simulate the excitation of slow-mode waves in two types of 1D loop
models. We find that the models with the seismology-determined transport
coefficients can excite the standing waves quickly as observed, while
the models with the classical transport coefficients excites basically
the reflecting propagating waves. Simulations of harmonic waves and
the Fourier decomposition analysis reveal a scaling between damping
time and wave period as Td ~ P in the former type of models,
while Td ~ P2 in the latter type. This suggests
that anomalously large viscosity can efficiently enhance the dissipation
of higher harmonic components, favoring quick setup of the fundamental
standing mode. Our study indicates that observational constraints on
the transport coefficients are crucial in understanding both the wave
excitation and damping mechanisms.

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Title: Relationship between the Coronal Activity and Magnetic Flux
over Solar Cycle 24
Authors: Wang, Tongjiang; Reginald, Nelson Leslie; Davila, Joseph M.;
St Cyr, O. C.
2018tess.conf10309W Altcode:
It is widely accepted that the variability of the solar white-light
corona is closely connected to the solar activity. Many previous
studies have revealed that the temporal variation of the total
radiance of the K-corona follows the solar cycle pattern (e.g.,
correlated with sunspot number). However, systematic studies on the
origin of the coronal mass and its variability are still rare. In
this study, by means of the spherically symmetric inversion (SSI)
method we reconstruct 3D coronal densities for Carrington Rotations
(CRs) 2079--2180 over 2009--2017 using polarized brightness (pB)
images observed with STEREO/COR1 and LASCO/C2. We calculate the total
coronal mass from these density reconstructions within certain radial
ranges, and compare its temporal evolution with the total magnetic flux
measured from SOHO/MDI and SDO/HMI. We find a high correlation between
the variations of total coronal mass and magnetic flux, and the former
appears to be lagged by a CR to the latter during the rising phase of
Cycle 24. To confirm this finding we also compare the observed coronal
masses with those calculated from global thermodynamic MHD models by
Predictive Science Inc (PSI), and compare the evolution of SDO/EVE
line emissions between the chromosphere and the corona. In addition,
we also explore the origin of the peaks in coronal mass and magnetic
flux variations during the rising phase of Cycle 24.

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Title: Solar Coronagraphs from the DSG
Authors: Newmark, J. S.; Davila, J. M.
2018LPICo2063.3079N Altcode:
A solar coronagraph mounted on the Deep Space Gateway will enable
unprecedented observations of the low solar corona; in particular
provide key observational constraints on the initiation of Coronal
Mass Ejections (CMEs).

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Title: Space Weather Diamond: A 10x Improvement in Real-Time
Forecasting
Authors: St Cyr, O. C.; Davila, J. M.; Newmark, J.
2018LPICo2063.3057S Altcode:
Space Weather Diamond is based on a constellation of four platforms that
are phased into eccentric heliocentric orbits but, from the perspective
of a fixed Sun-Earth line, the spacecraft appear to orbit Earth.

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Title: Progress on Using Image-Optimization to Improve Coronal
Magnetic Field Models
Authors: Jones, Shaela; Davila, Joseph M.; Uritsky, Vadim M.
2018AAS...23133803J Altcode:
Reliable measurements of the coronal magnetic field have proven to be
very elusive. Over several decades, solar physicists have developed
means of extrapolating photospheric magnetic field measurements into the
corona and ultimately into the heliosphere. However, these methods can
be very sensitive to the photospheric measurements, with a significant
range of heliospheric conditions possible within the uncertainty of
the photospheric magnetograms. Recently we have presented a method
to obtain morphological information about the coronal magnetic field
from coronagraph images, and to incorporate this information into
a PFSS coronal magnetic field model via optimization. Here we will
present details of the method and recent progress in its development,
including a significant speed-up of the optimization process that
allows the optimization of higher-resolution coronal models.

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Title: Image-based optimization of coronal magnetic field models
for improved space weather forecasting
Authors: Uritsky, V. M.; Davila, J. M.; Jones, S. I.; MacNeice, P. J.
2017AGUFMSH21A2643U Altcode:
The existing space weather forecasting frameworks show a significant
dependence on the accuracy of the photospheric magnetograms and the
extrapolation models used to reconstruct the magnetic filed in the
solar corona. Minor uncertainties in the magnetic field magnitude and
direction near the Sun, when propagated through the heliosphere, can
lead to unacceptible prediction errors at 1 AU. We argue that ground
based and satellite coronagraph images can provide valid geometric
constraints that could be used for improving coronal magnetic field
extrapolation results, enabling more reliable forecasts of extreme
space weather events such as major CMEs. In contrast to the previously
developed loop segmentation codes designed for detecting compact
closed-field structures above solar active regions, we focus on the
large-scale geometry of the open-field coronal regions up to 1-2 solar
radii above the photosphere. By applying the developed image processing
techniques to high-resolution Mauna Loa Solar Observatory images, we
perform an optimized 3D B-line tracing for a full Carrington rotation
using the magnetic field extrapolation code developed S. Jones at
al. (ApJ 2016, 2017). Our tracing results are shown to be in a good
qualitative agreement with the large-scale configuration of the optical
corona, and lead to a more consistent reconstruction of the large-scale
coronal magnetic field geometry, and potentially more accurate global
heliospheric simulation results. Several upcoming data products for
the space weather forecasting community will be also discussed.

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Title: The Image-Optimized Corona; Progress on Using Coronagraph
Images to Constrain Coronal Magnetic Field Models
Authors: Jones, S. I.; Uritsky, V. M.; Davila, J. M.
2017AGUFMSH11C..06J Altcode:
In absence of reliable coronal magnetic field measurements, solar
physicists have worked for several decades to develop techniques
for extrapolating photospheric magnetic field measurements into the
solar corona and/or heliosphere. The products of these efforts tend
to be very sensitive to variation in the photospheric measurements,
such that the uncertainty in the photospheric measurements introduces
significant uncertainty into the coronal and heliospheric models needed
to predict such things as solar wind speed, IMF polarity at Earth,
and CME propagation. Ultimately, the reason for the sensitivity of the
model to the boundary conditions is that the model is trying to extact a
great deal of information from a relatively small amout of data. We have
published in recent years about a new method we are developing to use
morphological information gleaned from coronagraph images to constrain
models of the global coronal magnetic field. In our approach, we treat
the photospheric measurements as approximations and use an optimization
algorithm to iteratively find a global coronal model that best matches
both the photospheric measurements and quasi-linear features observed
in polarization brightness coronagraph images. Here we will summarize
the approach we have developed and present recent progress in optimizing
PFSS models based on GONG magnetograms and MLSO K-Cor images.

---------------------------------------------------------
Title: Remote Sensing of the Solar Wind Density, Speed, and
Temperature in the Region between the Sun and Parker Solar Probe
Authors: Davila, J. M.; Reginald, N. L.
2017AGUFMSH23D2692D Altcode:
A coronagraph is the tool of choice to understand and observe the
structure of the corona from space. The novel coronagraph concept
presented her provides a new scientific capability that will allow the
measurement of density, temperature, and flow velocity in the solar
atmosphere. This instrument will provide the first remote sensing
measurement of the global solar wind temperature, density, and flow
speed in the regions between 3 and 8 Rsun. It is in this region that
the manority of the solar wind acceleration takes place, and where
the ion compsition of the solar wind is "frozen in". This is also the
region of the corona that links the surface of the Sun to the Parker
Solar Probe and to Solar Orbiter. The observations suggested here
would dramatically improve our understanding of solar wind formation
and evolution in this critical region.

---------------------------------------------------------
Title: Recent Advances in Atmospheric, Solar-Terrestrial Physics and
Space Weather From a North-South network of scientists [2006-2016]
PART B : Results and Capacity Building
Authors: Amory-Mazaudier, C.; Fleury, R.; Petitdidier, M.; Soula, S.;
Masson, F.; Davila, J.; Doherty, P.; Elias, A.; Gadimova, S.; Makela,
J.; Nava, B.; Radicella, S.; Richardson, J.; Touzani, A.; Girgea Team
2017SunGe..12S..21A Altcode:
This paper reviews scientific advances achieved by a North-South
network between 2006 and 2016. These scientific advances concern solar
terrestrial physics, atmospheric physics and space weather. This part B
is devoted to the results and capacity building. Our network began
in 1991, in solar terrestrial physics, by our participation in the two
projects: International Equatorial Electrojet Year IEEY [1992-1993]
and International Heliophysical Year IHY [2007-2009]. These two
projects were mainly focused on the equatorial ionosphere in Africa. In Atmospheric physics our research focused on gravity waves in the
framework of the African Multidisciplinary Monsoon Analysis project n°1
[2005-2009 ], on hydrology in the Congo river basin and on lightning
in Central Africa, the most lightning part of the world. In Vietnam
the study of a broad climate data base highlighted global warming. In space weather, our results essentially concern the impact of solar
events on global navigation satellite system GNSS and on the effects
of solar events on the circulation of electric currents in the earth
(GIC). This research began in the framework of the international
space weather initiative project ISWI [2010-2012]. Finally,
all these scientific projects have enabled young scientists from the
South to publish original results and to obtain positions in their
countries. These projects have also crossed disciplinary boundaries
and defined a more diversified education which led to the training of
specialists in a specific field with knowledge of related scientific
fields.

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Title: ASPIICS: a giant, white light and emission line coronagraph
for the ESA proba-3 formation flight mission
Authors: Lamy, P. L.; Vivès, S.; Curdt, W.; Damé, L.; Davila, J.;
Defise, J. -M.; Fineschi, S.; Heinzel, P.; Howard, Russel; Kuzin,
S.; Schmutz, W.; Tsinganos, K.; Zhukov, A.
2017SPIE10565E..0TL Altcode:
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observations of the white light corona inside typically 2-2.5
solar radii (Rsun). Formation flying offers and elegant solution to
these limitations and allows conceiving giant, externally-occulted
coronagraphs using a two-component space system with the external
occulter on one spacecraft and the optical instrument on the
other spacecraft at a distance of hundred meters [1, 2]. Such
an instrument ASPIICS (Association de Satellites Pour l'Imagerie
et l'Interférométrie de la Couronne Solaire) has been selected
by the European Space Agency (ESA) to fly on its PROBA-3 mission
of formation flying demonstration which is presently in phase B
(Fig. 1). The classical design of an externally-occulted coronagraph is
adapted to the formation flying configuration allowing the detection
of the very inner corona as close as 0.04 solar radii from the solar
limb. By tuning the position of the occulter spacecraft, it may even be
possible to reach the chromosphere and the upper part of the spicules
[3]. ASPIICS will perform (i) high spatial resolution imaging of the
continuum K+F corona in photometric and polarimetric modes, (ii) high
spatial resolution imaging of the E-corona in two coronal emission lines
(CEL): Fe XIV and He I D3, and (iii) two-dimensional spectrophotometry
of the Fe XIV emission line. ASPIICS will address the question of the
coronal heating and the role of waves by characterizing propagating
fluctuations (waves and turbulence) in the solar wind acceleration
region and by looking for oscillations in the intensity and Doppler
shift of spectral lines. The combined imaging and spectral diagnostics
capabilities available with ASPIICS will allow mapping the velocity
field of the corona both in the sky plane (directly on the images)
and along the line-of-sight by measuring the Doppler shifts of
emission lines in an effort to determine how the different components
of the solar wind, slow and fast are accelerated. With a possible
launch in 2014, ASPIICS will observe the corona during the maximum of
solar activity, insuring the detection of many Coronal Mass Ejections
(CMEs). By rapidly alternating high-resolution imaging and spectroscopy,
CMEs will be thoroughly characterized.

---------------------------------------------------------
Title: Weighing supermassive black holes with the UV photon sieve
space telescope
Authors: Airapetian, Vladimir; Upton, Robert S.; Davila, Joseph;
Marzouk, Marzouk; Carpenter, Kenneth G.; Weaver, Kimberly
2017SPIE10564E..3RA Altcode:
The Photon Sieve Space Telescope (PSST) is a space-based ultra
high-resolution (5 mas) narrow band (λ/Δλ ≃ 1000) spectral UV
imager providing spectral imaging of astronomical objects in Ly - ,
CIV and NV emission lines. Science obtained with this telescope will
revolutionize our understanding of a whole range of astrophysical
processes in the local and distant universe. There will be a dramatic
increase in the number of observed moderate and large SMBH masses as
well as extra-solar protoplanetary disks. The observations will also
enable tracing the star formation rates in active galaxies. We present
the optical design, the properties and the future implementation of
the proposed UV photon sieve space telescope.

---------------------------------------------------------
Title: Toward a Next Generation Solar Coronagraph: Development of
a Compact Diagnostic Coronagraph on the ISS
Authors: Cho, K. -S.; Bong, S. -C.; Choi, S.; Yang, H.; Kim, J.;
Baek, J. -H.; Park, J.; Lim, E. -K.; Kim, R. -S.; Kim, S.; Kim,
Y. -H.; Park, Y. -D.; Clarke, S. W.; Davila, J. M.; Gopalswamy, N.;
Nakariakov, V. M.; Li, B.; Pinto, R. F.
2017JKAS...50..139C Altcode:
The Korea Astronomy and Space Science Institute plans to develop
a coronagraph in collaboration with National Aeronautics and Space
Administration (NASA) and to install it on the International Space
Station (ISS). The coronagraph is an externally occulted one-stage
coronagraph with a field of view from 3 to 15 solar radii. The
observation wavelength is approximately 400 nm, where strong Fraunhofer
absorption lines from the photosphere experience thermal broadening and
Doppler shift through scattering by coronal electrons. Photometric
filter observations around this band enable the estimation of
2D electron temperature and electron velocity distribution in the
corona. Together with a high time cadence (&lt;12 min) of corona images
used to determine the geometric and kinematic parameters of coronal
mass ejections, the coronagraph will yield the spatial distribution
of electron density by measuring the polarized brightness. For the
purpose of technical demonstration, we intend to observe the total
solar eclipse in August 2017 with the filter system and to perform a
stratospheric balloon experiment in 2019 with the engineering model
of the coronagraph. The coronagraph is planned to be installed on the
ISS in 2021 for addressing a number of questions (e.g., coronal heating
and solar wind acceleration) that are both fundamental and practically
important in the physics of the solar corona and of the heliosphere.

---------------------------------------------------------
Title: Effects of transport coefficients on excitation of
flare-induced standing slow-mode waves
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph
2017SPD....48.0202W Altcode:
The flare-excited longitudinal intensity oscillations in hot flaring
loops have been recently detected by SDO/AIA, and interpreted as the
slow-mode standing waves. By means of the seismology technique we
have, for the first time, determined the transport coefficients in the
hot (&gt;9 MK) flare plasma, and found that thermal conductivity is
suppressed by at least 3 times and viscosity coefficient is enhanced
by a factor of 15 as the upper limit (Wang et al. 2015, ApJL, 811,
L13). In this presentation, we first discuss possible causes for
conduction suppression and viscosity enhancements. Then we use the
nonlinear MHD simulations to validate the seismology method that is
based on linear analytical analysis, and demonstrate the inversion
scheme for determining transport coefficients using numerical parametric
study. Finally, we show how the seismologically-determined transport
coefficients are crucial for understanding the excitation of the
observed standing slow-mode waves in coronal loops and the heating of
the loop plasma by a footpoint flare.

---------------------------------------------------------
Title: Mission Concepts for High-Resolution Solar Imaging with a
Photon Sieve
Authors: Rabin, Douglas M.; Davila, Joseph; Daw, Adrian N.; Denis,
Kevin L.; Novo-Gradac, Anne-Marie; Shah, Neerav; Widmyer, Thomas R.
2017SPD....4811006R Altcode:
The best EUV coronal imagers are unable to probe the expected
energy dissipation scales of the solar corona (&lt;100 km) because
conventional optics cannot be figured to near diffraction-limited
accuracy at these wavelengths. Davila (2011) has proposed that a
photon sieve, a diffractive imaging element similar to a Fresnel zone
plate, provides a technically feasible path to the required angular
resolution. We have produced photon sieves as large as 80 mm clear
aperture. We discuss laboratory measurements of these devices and the
path to larger apertures. The focal length of a sieve with high EUV
resolution is at least 10 m. Options for solar imaging with such a
sieve include a sounding rocket, a single spacecraft with a deployed
boom, and two spacecraft flying in precise formation.

---------------------------------------------------------
Title: Study of the global corona evolution from the minimum
to maximum of solar cycle 24 using 3D coronal electron density
reconstructions with STEREO/COR1
Authors: Wang, Tongjiang; Reginald, Nelson Leslie; Davila, Joseph;
St. Cyr, Orville Chris; Thompson, William T.
2017SPD....4830101W Altcode:
This study aims at understanding the global corona evolution of
the coronal activity during Solar Cycle 24 on both long-term and
short-term time scales. By using a spherically symmetric polynomial
approximation (SSPA) method described and validated in Wang and Davila
(2014), the 3D coronal electron density in the height range of 1.5 to
3.7 Rsun is reconstructed based on STEREO/COR1-A and -B pB data. The
reconstructions span a period from the Cycle 23/24 minimum to the
Cycle 24 maximum, covering Carrington rotations (CRs) 2054-2153, for
a total of 100 rotations. These 3D electron density distributions are
validated by comparing with similar density models derived using other
methods such as tomography and a MHD model as well as using data from
SOHO/LASCO-C2. Uncertainties in the density reconstruction and estimated
total coronal mass are analyzed. The cycle minimum-to-maximum modulation
factors (MFs) of the coronal average electron density (or the total
coronal mass) at different latitudinal ranges are quantified. Wavelet
analysis of the cycle-long detrended density data reveals the existence
of quasi-periodic short-term (7-8 months) variations during the rising
and maximum activity phases. For the total mass of streamers the MFs
depend on the changes in both their total area and average density,
but the short-term oscillations are mainly caused by the streamer
density fluctuations. A clear asymmetry is observed in the temporal
evolution of the northern and southern hemispheres, with the former
leading the latter by a lapse of 7-9 months, with a mild dependence
on the latitude range.

---------------------------------------------------------
Title: The VUV instrument SPICE for Solar Orbiter: performance
ground testing
Authors: Caldwell, Martin E.; Morris, Nigel; Griffin, Douglas K.;
Eccleston, Paul; Anderson, Mark; Pastor Santos, Carmen; Bruzzi,
Davide; Tustain, Samuel; Howe, Chris; Davenne, Jenny; Grundy, Timothy;
Speight, Roisin; Sidher, Sunil D.; Giunta, Alessandra; Fludra, Andrzej;
Philippon, Anne; Auchere, Frederic; Hassler, Don; Davila, Joseph M.;
Thompson, William T.; Schuehle, Udo H.; Meining, Stefan; Walls, Buddy;
Phelan, P.; Dunn, Greg; Klein, Roman M.; Reichel, Thomas; Gyo, Manfred;
Munro, Grant J.; Holmes, William; Doyle, Peter
2017SPIE10397E..08C Altcode:
SPICE is an imaging spectrometer operating at vacuum ultraviolet
(VUV) wavelengths, 70.4 - 79.0 nm and 97.3 - 104.9 nm. It is a
facility instrument on the Solar Orbiter mission, which carries
10 science instruments in all, to make observations of the Sun's
atmosphere and heliosphere, at close proximity to the Sun, i.e to
0.28 A.U. at perihelion. SPICE's role is to make VUV measurements
of plasma in the solar atmosphere. SPICE is designed to achieve
spectral imaging at spectral resolution &gt;1500, spatial resolution
of several arcsec, and two-dimensional FOV of 11 x16arcmins. The many
strong constraints on the instrument design imposed by the mission
requirements prevent the imaging performance from exceeding those of
previous instruments, but by being closer to the sun there is a gain in
spatial resolution. The price which is paid is the harsher environment,
particularly thermal. This leads to some novel features in the design,
which needed to be proven by ground test programs. These include a
dichroic solar-transmitting primary mirror to dump the solar heat, a
high in-flight temperature (60deg.C) and gradients in the optics box,
and a bespoke variable-line-spacing grating to minimise the number of
reflective components used. The tests culminate in the systemlevel test
of VUV imaging performance and pointing stability. We will describe how
our dedicated facility with heritage from previous solar instruments,
is used to make these tests, and show the results, firstly on the
Engineering Model of the optics unit, and more recently on the Flight
Model. For the keywords, select up to 8 key terms for a search on your
manuscript's subject.

---------------------------------------------------------
Title: Variation in Coronal Activity from Solar Cycle 24 Minimum
to Maximum Using Three-Dimensional Reconstructions of the Coronal
Electron Density from STEREO/COR1
Authors: Wang, Tongjiang; Reginald, Nelson L.; Davila, Joseph M.;
St. Cyr, O. Chris; Thompson, William T.
2017SoPh..292...97W Altcode:
Three-dimensional electron density distributions in the solar corona
are reconstructed for 100 Carrington rotations (CR 2054 - 2153) during
2007/03 - 2014/08 using the spherically symmetric method from polarized
white-light observations with the inner coronagraph (COR1) onboard
the twin Solar Terrestrial Relations Observatory (STEREO). These
three-dimensional electron density distributions are validated by
comparison with similar density models derived using other methods
such as tomography and a magnetohydrodynamics (MHD) model as well as
using data from the Solar and Heliospheric Observatory (SOHO)/Large
Angle and Spectrometric Coronagraph (LASCO)-C2. Uncertainties in
the estimated total mass of the global corona are analyzed based
on differences between the density distributions for COR1-A and
-B. Long-term variations of coronal activity in terms of the global
and hemispheric average electron densities (equivalent to the total
coronal mass) reveal a hemispheric asymmetry during the rising phase
of Solar Cycle 24, with the northern hemisphere leading the southern
hemisphere by a phase shift of 7 - 9 months. Using 14 CR (≈13 -month)
running averages, the amplitudes of the variation in average electron
density between Cycle 24 maximum and Cycle 23/24 minimum (called the
modulation factors) are found to be in the range of 1.6 - 4.3. These
modulation factors are latitudinally dependent, being largest in polar
regions and smallest in the equatorial region. These modulation factors
also show a hemispheric asymmetry: they are somewhat larger in the
southern hemisphere. The wavelet analysis shows that the short-term
quasi-periodic oscillations during the rising and maximum phases of
Cycle 24 have a dominant period of 7 - 8 months. In addition, it is
found that the radial distribution of the mean electron density for
streamers at Cycle 24 maximum is only slightly larger (by ≈30 % )
than at cycle minimum.

---------------------------------------------------------
Title: Image-optimized Coronal Magnetic Field Models
Authors: Jones, Shaela I.; Uritsky, Vadim; Davila, Joseph M.
2017ApJ...844...93J Altcode: 2017arXiv170607316J
We have reported previously on a new method we are developing for
using image-based information to improve global coronal magnetic field
models. In that work, we presented early tests of the method, which
proved its capability to improve global models based on flawed synoptic
magnetograms, given excellent constraints on the field in the model
volume. In this follow-up paper, we present the results of similar tests
given field constraints of a nature that could realistically be obtained
from quality white-light coronagraph images of the lower corona. We pay
particular attention to difficulties associated with the line-of-sight
projection of features outside of the assumed coronagraph image plane
and the effect on the outcome of the optimization of errors in the
localization of constraints. We find that substantial improvement in the
model field can be achieved with these types of constraints, even when
magnetic features in the images are located outside of the image plane.

---------------------------------------------------------
Title: Variation of Coronal Activity from the Minimum to Maximum
of Solar Cycle 24 using Three Dimensional Coronal Electron Density
Reconstructions from STEREO/COR1
Authors: Wang, Tongjiang; Reginald, Nelson L.; Davila, Joseph M.;
St. Cyr, O. Chris; Thompson, William T.
2017arXiv170605116W Altcode:
Three dimensional electron density distributions in the solar corona
are reconstructed for 100 Carrington Rotations (CR 2054$-$2153) during
2007/03$-$2014/08 using the spherically symmetric method from polarized
white-light observations with the STEREO/COR1. These three-dimensional
electron density distributions are validated by comparison with similar
density models derived using other methods such as tomography and
a MHD model as well as using data from SOHO/LASCO-C2. Uncertainties
in the estimated total mass of the global corona are analyzed based
on differences between the density distributions for COR1-A and
-B. Long-term variations of coronal activity in terms of the global
and hemispheric average electron densities (equivalent to the total
coronal mass) reveal a hemispheric asymmetry during the rising phase
of Solar Cycle 24, with the northern hemisphere leading the southern
hemisphere by a phase shift of 7$-$9 months. Using 14-CR (~13-month)
running averages, the amplitudes of the variation in average electron
density between Cycle 24 maximum and Cycle 23/24 minimum (called the
modulation factors) are found to be in the range of 1.6$-$4.3. These
modulation factors are latitudinally dependent, being largest in
polar regions and smallest in the equatorial region. These modulation
factors also show a hemispheric asymmetry, being somewhat larger in the
southern hemisphere. The wavelet analysis shows that the short-term
quasi-periodic oscillations during the rising and maximum phases
of Cycle 24 have a dominant period of 7$-$8 months. In addition,
it is found that the radial distribution of mean electron density
for streamers at Cycle 24 maximum is only slightly larger (by ~30%)
than at cycle minimum.

---------------------------------------------------------
Title: Electron temperature maps of the low solar corona: ISCORE
results from the total solar eclipse of 1 August 2008 in China
Authors: Reginald, Nelson L.; Davila, Joseph M.; St. Cyr, Orville C.;
Rabin, Douglas M.
2017JGRA..122.5856R Altcode:
We conducted an experiment in conjunction with the total solar eclipse
of 1 August 2008 in China to determine the thermal electron temperature
in the low solar corona close to the solar limb. The instrument, Imaging
Spectrograph of Coronal Electrons (ISCORE), consisted of an 8 inch f/10
Schmidt Cassegrain telescope with a thermoelectrically cooled CCD camera
at the focal plane. Results are electron temperatures of 1 MK at 1.08
R⊙ and 1.13 R⊙ from the Sun center in the
polar and equatorial regions, respectively. This experiment confirms
the results of an earlier experiment conducted in conjunction with
the total eclipse of 29 March 2006 in Libya, and results are that at
a given coronal height the electron temperature in the polar region
is larger than at the equatorial region. In this paper we show the
importance of using the correct photospheric spectrum pertinent to
the solar activity phase at the time of the experiment, which is a
required parameter for modeling the underlying theoretical concept
for temperature interpretation of the measured intensity ratios using
color filters.

---------------------------------------------------------
Title: Image-Optimized Coronal Magnetic Field Models
Authors: Jones, S. I.; Davila, J. M.; Uritsky, V. M.
2016AGUFMSH43A2555J Altcode:
Synoptic photospheric magnetograms suffer from a number of known issues;
the evolution of the magnetic field on the far side of the sun being
one of them. These issues are important because photospheric maps are
often used as boundary conditions for models of the coronal magnetic
field, and choices made during the construction of the maps can have
a large effect on the resulting model. We have developed a method for
quantifying the agreement between coronal magnetic field models and
coronagraph images, which we use to strategically perturb the underlying
magnetogram until an optimal agreement between the model and the images
is achieved. Here we present a theoretical test of our method, and
results of our first application of the method using MLSO K-Cor images.

---------------------------------------------------------
Title: Determination of transport coefficients from flare-excited
standing slow-mode waves observed by SDO/AIA
Authors: Wang; Tongjiang; Ofman, Leon; Davila, Joseph M.
2016usc..confE..36W Altcode:
The flare-excited longitudinal intensity oscillations in hot flaring
loops have been recently detected by SDO/AIA in 94 and 131 Angstrom
bandpasses. These oscillations show similar physical properties (such
as period, decay time, and trigger) as the Doppler shift oscillations
previously detected by the SOHO/SUMER spectrometer in flare lines formed
above 6 MK, which were mostly interpreted as the slow-mode standing
waves. By applying the coronal seismology method we have, for the first
time, found quantitative evidence of thermal conduction suppression in
a hot (&gt;9 MK) flare-heated loop with SDO/AIA (Wang et al. 2015, ApJL,
811, L13). This result has significant implications in two aspects. The
first aspect is that the conduction suppression suggests the need of
greatly enhanced compressive viscosity to interpret the observed strong
wave damping. The second aspect is that the conduction suppression
provides a reasonable mechanism for explaining the long-duration events
where the hot plasma detected in X-rays or EUV in many flares cools much
slower than expected from the classical Spitzer conductive cooling. In
this presentation, we first review the observational results of the
event, and then discuss possible causes for conduction suppression
and viscosity enhancements. In addition, we will use the nonlinear
MHD simulations to validate the seismology method that is based on
linear analytical analysis, and demonstrate the inversion scheme
for determining transport coefficients using numerical parametric
study. Finally, as an application of our analysis, we will demonstrate
how the observationally-constrained transport coefficients are crucial
in providing a self-consistent explanation for the rapid excitation
of standing slow-mode waves in a coronal loop by a footpoint flare.

---------------------------------------------------------
Title: Evolution of 3D electron density of the solar corona from
the minimum to maximum of Solar Cycle 24
Authors: Wang, Tongjiang; Reginald, Nelson L.; Davila, Joseph M.;
St Cyr, O. C.
2016usc..confE..53W Altcode:
The variability of the solar white-light corona and its connection to
the solar activity has been studied for more than a half century. It
is widely accepted that the temporal variation of the total radiance
of the K-corona follows the solar cycle pattern (e.g., correlated
with sunspot number). However, the origin of this variation and its
relationships with regard to coronal mass ejections and the solar wind
are yet to be clearly understood. COR1-A and -B instruments onboard
the STEREO spacecraft have continued to perform high-cadence (5 min)
polarized brightness (pB) measurements from two different vantage
points from the solar minimum to the solar maximum of Solar Cycle
24. With these pB observations we have reconstructed the 3D coronal
density between 1.5-4.0 solar radii for 100 Carrington rotations
(CRs) from 2007 to 2014 using the spherically symmetric inversion
(SSI) method. We validate these 3D density reconstructions by other
means such as tomography, MHD modeling, and pB inversion of LASCO/C2
data. We analyze the solar cycle variations of total coronal mass
(or average density) over the global Sun and in two hemispheres,
as well as the variations of the streamer area and mean density. We
find the short-term oscillations of 8-9 CRs during the ascending and
maximum phases through wavelet analysis. We explore the origin of these
oscillations based on evolution of the photospheric magnetic flux and
coronal structures.

---------------------------------------------------------
Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun
to the Heliosphere
Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial,
Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson,
William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere,
Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest,
Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho;
Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta,
Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander;
Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo
2016cosp...41E.607F Altcode:
The SPICE (Spectral Imaging of the Coronal Environment) instrument is
one of the key remote sensing instruments onboard the upcoming Solar
Orbiter Mission. SPICE has been designed to contribute to the science
goals of the mission by investigating the source regions of outflows
and ejection processes which link the solar surface and corona to the
heliosphere. In particular, SPICE will provide quantitative information
on the physical state and composition of the solar atmosphere
plasma. For example, SPICE will access relative abundances of ions to
study the origin and the spatial/temporal variations of the 'First
Ionization Potential effect', which are key signatures to trace the
solar wind and plasma ejections paths within the heliosphere. Here we
will present the instrument and its performance capability to attain the
scientific requirements. We will also discuss how different observation
modes can be chosen to obtain the best science results during the
different orbits of the mission. To maximize the scientific return of
the instrument, the SPICE team is working to optimize the instrument
operations, and to facilitate the data access and their exploitation.

---------------------------------------------------------
Title: Solar abundances with the SPICE spectral imager on Solar
Orbiter
Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi;
Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina;
Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William;
Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin;
Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.;
DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne;
Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin,
Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston,
Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy;
Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany
2016cosp...41E.681G Altcode:
Elemental composition of the solar atmosphere and in particular
abundance bias of low and high First Ionization Potential (FIP)
elements are a key tracer of the source regions of the solar wind. These
abundances and their spatio-temporal variations, as well as the other
plasma parameters , will be derived by the SPICE (Spectral Imaging
of the Coronal Environment) EUV spectral imager on the upcoming
Solar Orbiter mission. SPICE is designed to provide spectroheliograms
(spectral images) using a core set of emission lines arising from ions
of both low-FIP and high-FIP elements. These lines are formed over
a wide range of temperatures, enabling the analysis of the different
layers of the solar atmosphere. SPICE will use these spectroheliograms
to produce dynamic composition maps of the solar atmosphere to be
compared to in-situ measurements of the solar wind composition of
the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to
study the connectivity between the spacecraft (the Heliosphere) and
the Sun. We will discuss the SPICE capabilities for such composition
measurements.

---------------------------------------------------------
Title: Computational image formation with photon sieves for
milli-arcsecond solar imaging
Authors: Oktem, Figen S.; Kamalabadi, Farzad; Davila, Joseph
2016cosp...41E1465O Altcode:
A photon sieve is a modification of a Fresnel zone plate in which
open zones are replaced by a large number of circular holes. This
diffractive imaging element is specially suited to observations at
UV and x-ray wavelengths where refractive lenses are not available
due to strong absorption of materials, and reflective mirrors are
difficult to manufacture with sufficient surface figure accuracy to
achieve diffraction-limited resolution. On the other hand, photon
sieves enable diffraction-limited imaging with much more relaxed
tolerances than conventional imaging technology. In this presentation,
we present the capabilities of an instrument concept that is based
on computational image formation with photon sieves. The instrument
enables high-resolution spectral imaging by distributing the imaging
task between a photon sieve system and a computational method. A
photon sieve coupled with a moving detector provides measurements from
multiple planes. Then computational image formation, which involves
deconvolution, is performed in a Bayesian estimation framework to
reconstruct the multi-spectral images from these measurements. In
addition to diffraction-limited high spatial resolution enabled
by photon sieves, this instrument can also achieve higher spectral
resolution than the conventional spectral imagers, since the technique
offers the possibility of separating nearby spectral components that
would not otherwise be possible using wavelength filters. Here, the
promising capabilities and the imaging performance are shown for
imaging the solar corona at EUV wavelengths. The effectiveness of
various potential observing scenarios, the effects of interfering
emission lines, and the appropriate form of the cost function for
image deconvolution are examined.

---------------------------------------------------------
Title: Milli-Arcsecond Imaging of the Solar Corona
Authors: Davila, Joseph; Kamalabadi, Farzad; Oktem, Figen S.
2016cosp...41E.407D Altcode:
Dissipation in the solar corona is believed to occur in extremely
thin current sheets of order 1-100 km. Emission from these hot
but thin current sheets is visible in coronal EUV emission lines,
however, this spatial scale is unresolved in existing imaging
instruments. Conventional optics cannot be easily manufactured with
sufficient surface figure accuracy to obtain the required resolution. A
photon sieve, a diffractive imaging element similar to a Fresnel
zone plate, can be manufactured to provide a few milli-arcsec (mas)
resolution, with much more relaxed tolerances than conventional
imaging technology. Images from photon sieves will not only show the
structure of the corona at a resolution never before obtained, they
will also allow a study of the temperature structure in the dissipation
region. Several photon sieves have been designed, fabricated, and tested
by us at Goddard Space Flight Center. To fully exploit the potential
of these devices two new technologies, (1) formation flying and (2)
computational image deconvolution must be used. Recent progress on
photon sieve development as well as these issues will be discussed. A
simple design for a sounding rocket payload is presented that obtains
80 mas (0.080 arcsec) imaging with a 100 mm diameter photon sieve to
image Fe XIV 334 and Fe XVI 335 which would provide a demonstration
of this technology.

---------------------------------------------------------
Title: Coronal Seismology of Flare-Excited Standing Slow-Mode Waves
Observed by SDO/AIA
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.
2016SPD....47.0632W Altcode:
Flare-excited longitudinal intensity oscillations in hot flaring
loops have been recently detected by SDO/AIA in 94 and 131 Å
bandpasses. Based on the interpretation in terms of a slow-mode wave,
quantitative evidence of thermal conduction suppression in hot (&gt;9
MK) loops has been obtained for the first time from measurements
of the polytropic index and phase shift between the temperature and
density perturbations (Wang et al. 2015, ApJL, 811, L13). This result
has significant implications in two aspects. One is that the thermal
conduction suppression suggests the need of greatly enhanced compressive
viscosity to interpret the observed strong wave damping. The other
is that the conduction suppression provides a reasonable mechanism
for explaining the long-duration events where the thermal plasma is
sustained well beyond the duration of impulsive hard X-ray bursts in
many flares, for a time much longer than expected by the classical
Spitzer conductive cooling. In this study, we model the observed
standing slow-mode wave in Wang et al. (2015) using a 1D nonlinear MHD
code. With the seismology-derived transport coefficients for thermal
conduction and compressive viscosity, we successfully simulate the
oscillation period and damping time of the observed waves. Based on
the parametric study of the effect of thermal conduction suppression
and viscosity enhancement on the observables, we discuss the inversion
scheme for determining the energy transport coefficients by coronal
seismology.

---------------------------------------------------------
Title: Formation Flying Spacecraft Concept for Heliophysics
Applications
Authors: Novo-Gradac, Anne-Marie; Davila, Joseph; Yang, Guangning;
Lu, Wei; Shah, Neerav; Li, Steven X.
2016SPD....4720603N Altcode:
A number of space-based heliophysics instruments would benefit from
formation flying spacecraft. An occulter or a focusing optic such as a
photon sieve could be mounted on a separate spacecraft rather than at
the end of a boom. This would enable science measurements to be made
on smaller, less expensive spacecraft. To accomplish this goal, the
relative position of the spacecraft must be monitored and controlled to
high precision. We describe two separate optical sensing systems that
monitor relative position of the spacecraft to the level required for
a photon sieve mission concept wherein the photon sieve is mounted on
one spacecraft while the imaging detector is mounted on another. The
first system employs a novel time of flight measurement of a laser
beam that includes imbedded optical data packets. The contents of the
returning data packet can be compared to the departing data packet to
provide an extremely high resolution distance measurement. Employing
three such systems allows measurement of pitch and yaw in addition to
longitudinal separation. The second optical system monitors lateral
motion. A mildy divergent laser beam is transmitted from one spacecraft
to a sensor array on the second spacecraft. Monitoring the position
of the brightest portion of the beam on the sensor array provides
a direct measurement of lateral relative motion. Employing at least
two such systems enables monitoring roll of the spacecraft as well as
centration. We will also discuss low force thruster systems required
for high precision station keeping.

---------------------------------------------------------
Title: Milli-Arcsecond (MAS) Imaging of the Solar Corona
Authors: Davila, Joseph M.; Oktem, Figen S.; Kamalabadi, Farzad;
O'Neill, John; Novo-Gradac, Anne-Marie; Daw, Adrian N.; Rabin,
Douglas M.
2016SPD....47.0310D Altcode:
Dissipation in the solar corona is believed to occur in extremely
thin current sheets of order 1-100 km. Emission from these hot
but thin current sheets should be visible in coronal EUV emission
lines. However, this spatial scale is far below the resolution
of existing imaging instruments, so these dissipation sites have
never been observed individually. Conventional optics cannot be
manufactured with sufficient surface figure accuracy to obtain the
required spatial resolution in the extreme-ultraviolet where these
hot plasmas radiate. A photon sieve, a diffractive imaging element
similar to a Fresnel zone plate, can be manufactured to provide a
few milli-arcsec (MAS) resolution, with much more readily achievable
tolerances than with conventional imaging technology. Prototype photon
sieve elements have been fabricated and tested in the laboratory. A
full-scale ultra-high resolution instrument will require formation
flying and computational image deconvolution. Significant progress has
been made in overcoming these challenges, and some recent results in
these areas are discussed. A simple design for a sounding rocket concept
demonstration payload is presented that obtains 80 MAS (0.080 arcsec)
imaging with a 100 mm diameter photon sieve to image Fe XIV 334 and
Fe XVI 335. These images will show the structure of the corona at a
resolution never before obtained, and they will also allow a study of
the temperature structure in the dissipation region.

---------------------------------------------------------
Title: 3D Distribution of the Coronal Electron Density and its
Evolution with Solar Cycle
Authors: Wang, Tongjiang; Reginald, Nelson Leslie; Davila, Joseph M.;
St. Cyr, Orville Chris
2016SPD....47.0337W Altcode:
The variability of the solar white-light corona and its connection to
the solar activity has been studied for more than a half century. It is
widely accepted that the temporal variation of the total radiance of the
K-corona follows the solar cycle pattern (e.g., correlated with sunspot
number). However, the origin of this variation and its relationships
with regard to coronal mass ejections and the solar wind are yet to
be clearly understood. We know that the COR1-A and -B instruments
onboard the STEREO spacecraft have continued to perform high-cadence
(5 min) polarized brightness measurements from two different vantage
points over a long period of time that encompasses the solar minimum
of Solar Cycle 23 to the solar maximum of Solar Cycle 24. This
extended period of polarized brightness measurements can now be used
to reconstruct 3D electron density distributions of the corona between
the heliocentric heights of 1.5-4.0 solar radii. In this study we have
constructed the 3D coronal density models for 100 Carrington rotations
(CRs) from 2007 to 2014 using the spherically symmetric inversion
(SSI) method. The validity of these 3D density models is verified by
comparing with similar 3D density models created by other means such as
tomography, MHD modeling, and 2D density distributions inverted from
the polarized brightness images from LASCO/C2 instrument onboard the
SOHO spacecraft. When examining the causes for the temporal variation
of the global electron content we find that its increase from the
solar minimum to maximum depends on changes to both the total area
and mean density of coronal streamers. We also find that the global
and hemispheric electron contents show quasi-periodic variations with
a period of 8-9 CRs during the ascending and maximum phases of Solar
Cycle 24 through wavelet analysis. In addition, we also explore any
obvious relationships between temporal variation of the global electron
content with the photospheric magnetic flux, total mass of CMEs and
CME occurrence rate.

---------------------------------------------------------
Title: Optimizing Global Coronal Magnetic Field Models Using
Image-based Constraints
Authors: Jones, Shaela I.; Davila, Joseph M.; Uritsky, Vadim
2016ApJ...820..113J Altcode: 2015arXiv151103994J
The coronal magnetic field directly or indirectly affects a majority of
the phenomena studied in the heliosphere. It provides energy for coronal
heating, controls the release of coronal mass ejections, and drives
heliospheric and magnetospheric activity, yet the coronal magnetic
field itself has proven difficult to measure. This difficulty has
prompted a decades-long effort to develop accurate, timely, models of
the field—an effort that continues today. We have developed a method
for improving global coronal magnetic field models by incorporating the
type of morphological constraints that could be derived from coronal
images. Here we report promising initial tests of this approach on
two theoretical problems, and discuss opportunities for application.

---------------------------------------------------------
Title: Evidence of thermal conduction suppression in hot coronal
loops: supplementary results
Authors: Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Provornikova,
Elena; Davila, Joseph M.
2016IAUS..320..202W Altcode: 2015arXiv151002750W
Slow magnetoacoustic waves were first detected in hot (&gt;6 MK) flare
loops by the SOHO/SUMER spectrometer as Doppler shift oscillations in Fe
xix and Fe xxi lines. Recently, such longitudinal waves have been found
by SDO/AIA in the 94 and 131 Å channels. Wang et al. (2015) reported
the first AIA event revealing signatures in agreement with a fundamental
standing slow-mode wave, and found quantitative evidence for thermal
conduction suppression from the temperature and density perturbations in
the hot loop plasma of &gt;~ 9 MK. The present study extends the work of
Wang et al. (2015) by using an alternative approach. We determine the
polytropic index directly based on the polytropic assumption instead
of invoking the linear approximation. The same results are obtained as
in the linear approximation, indicating that the nonlinearity effect
is negligible. We find that the flare loop cools slower (by a factor
of 2-4) than expected from the classical Spitzer conductive cooling,
approximately consistent with the result of conduction suppression
obtained from the wave analysis. The modified Spitzer cooling timescales
based on the nonlocal conduction approximation are consistent with
the observed, suggesting that nonlocal conduction may account for
the observed conduction suppression in this event. In addition, the
conduction suppression mechanism predicts that larger flares may tend
to be hotter than expected by the EM-T relation derived by Shibata &amp;
Yokoyama (2002).

---------------------------------------------------------
Title: Performance Measurements of the Flight Detector for SPICE
on SolarOrbiter
Authors: Thompson, W. T.; Davila, J. M.; Caldwell, M.; Siegmund, O.
2015AGUFMSH31C2431T Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument for
theSolar Orbiter mission will make spectroscopic observations of the
Sun's lowcorona to characterize the plasma properties of the source
regions of the solarwind. The detector package for SPICE, provided by
the NASA Goddard SpaceFLight Center, consists of two microchannel-plate
(MCP) intensified ActivePixel Sensor (APS) detectors covering the
short (702-792 Angstroms) and long(972-1050 Angstroms) wavelength
bandpasses. The long wavelength detector willalso provide coverage
in second order between 485-525 Angstroms. We previouslyreported
on measurements of the engineering model detector. Here, we report
onmeasurements made on the flight SPICE detector in the same vacuum tank
facilityat the Rutherford Appleton Laboratory in Harwell, UK. These
measurementsinclude the detector flat field, sensitivity, resolution,
linearity, andstatistical noise. A krypton resonance lamp operating
at 1236 Angstroms wasused to stimulate the detector. Results at this
wavelength are combined withthe quantum efficiency measurements
of the individual MCPs at this and otherwavelengths covering the
entire wavelength range to provide a completecalibration curve for
the instrument. A calibrated NIST photodiode was used todetermine the
absolute brightness of the lamp.

---------------------------------------------------------
Title: Coronal seismology of flare-excited longitudinal slow
magnetoacoustic waves in hot coronal loops
Authors: Wang, T.; Ofman, L.; Sun, X.; Provornikova, E. A.; Davila,
J. M.
2015AGUFMSH13B2435W Altcode:
The flare-excited longitudinal intensity oscillations in hot
flaring loops have been recently detected by SDO/AIA in 94 and 131
bandpasses. These oscillations show similar physical properties (such
as period, decay time, and trigger) as those slow-mode standing waves
previously detected by the SOHO/SUMER spectrometer in Doppler shift of
flare lines formed above 6 MK. The multi-wavelength AIA observations
with high spatio-temporal resolution and wide temperature coverage
enable us to measure both thermal and wave properties of the oscillating
hot plasma with unprecedented accuracy. These new measurements can
be used to diagnose the complicated energy transport processes in
flare plasma by a technique called coronal seismology based on the
combination of observations and MHD wave theory. From a detailed case
study we have found evidence for thermal conduction suppression in
hot loops by measuring the polytropic index and analyzing the phase
relationship between the temperature and density wave signals. This
result is not only crucial for better understanding the wave dissipation
mechanism but also provides an alternative mechanism to explain the
puzzles of long-duration events and X-ray loop-top sources which show
much slower cooling than expected by the classical Spitzer conductive
cooling. This finding may also shed a light on the coronal heating
problem because weak thermal conductivity implies slower cooling of hot
plasma in nanoflares, so increasing the average coronal temperature
for the same heating rate. We will discuss the effects of thermal
conduction suppression on the wave damping and loop cooling based on
MHD simulations.

---------------------------------------------------------
Title: Improving Heliospheric Field Models with Optimized Coronal
Models
Authors: Jones, S. I.; Davila, J. M.; Uritsky, V. M.
2015AGUFMSH31C2443J Altcode:
The Solar Orbiter and Solar Probe Plus missions will travel closer
to the sun than any previous mission, collecting unprecedented in
situ data. This data can provide insight into coronal structure,
energy transport, and evolution in the inner heliosphere. However,
in order to take full advantage of this data, researchers need quality
models of the inner heliosphere to connect the in situ observations to
their coronal and photospheric sources. Developing quality models for
this region of space has proved difficult, in part because the only
part of the field that is accessible for routine measurement is the
photosphere. The photospheric field measurements, though somewhat
problematic, are used as boundary conditions for coronal models,
which often neglect or over-simplify chromospheric conditions, and
these coronal models are then used as boundary conditions to drive
heliospheric models. The result is a great deal of uncertainty about
the accuracy and reliability of the heliospheric models. Here we
present a technique we are developing for improving global coronal
magnetic field models by optimizing the models to conform to the
field morphology observed in coronal images. This agreement between
the coronal model and the basic morphology of the corona is essential
for creating accurate heliospheric models. We will present results
of early tests of two implementations of this idea, and its first
application to real-world data.

---------------------------------------------------------
Title: Measuring Physical Parameters of CMES
Authors: Reginald, N. L.; Davila, J. M.; St Cyr, O. C.
2015AGUFMSH21B2405R Altcode:
In earlier work using eclipse observations, we have demonstrated that
coronal electron density, electron temperature and their bulk flow speed
can be measured. We have recently extended the associated modeling
to include the passage of a CME, and we describe the preliminary
results. The electron temperature in the solar corona determines
the amount of Doppler broadening of the solar spectrum as it Thomson
scatters off the coronal electrons. The outward flow of the coronal
electrons from the solar surface causes the coronal electrons to
see a red-shifted Sun and determines the amount of red-shift in the
K-coronal spectrum. Thus, the intensity, smoothness and red-shift of
the K-coronal spectrum along any given line of sight provide a measure
of the electron density, electron temperature and electron bulk flow
speed, respectively, along that line of sight. Likewise, the passing
of a CME across a line of sight in the ambient corona will alter the
shape of the K-coronal spectrum with respect to the ambient background.

---------------------------------------------------------
Title: Constraining Large-Scale Solar Magnetic Field Models with
Optical Coronal Observations
Authors: Uritsky, V. M.; Davila, J. M.; Jones, S. I.
2015AGUFMSH31C2444U Altcode:
Scientific success of the Solar Probe Plus (SPP) and Solar Orbiter
(SO) missions will depend to a large extent on the accuracy of the
available coronal magnetic field models describing the connectivity
of plasma disturbances in the inner heliosphere with their source
regions. We argue that ground based and satellite coronagraph images
can provide robust geometric constraints for the next generation of
improved coronal magnetic field extrapolation models. In contrast to
the previously proposed loop segmentation codes designed for detecting
compact closed-field structures above solar active regions, we focus
on the large-scale geometry of the open-field coronal regions located
at significant radial distances from the solar surface. Details on the
new feature detection algorithms will be presented. By applying the
developed image processing methodology to high-resolution Mauna Loa
Solar Observatory images, we perform an optimized 3D B-line tracing
for a full Carrington rotation using the magnetic field extrapolation
code presented in a companion talk by S.Jones at al. Tracing results
are shown to be in a good qualitative agreement with the large-scalie
configuration of the optical corona. Subsequent phases of the project
and the related data products for SSP and SO missions as wwll as the
supporting global heliospheric simulations will be discussed.

---------------------------------------------------------
Title: Requirements for an Operational Coronagraph
Authors: Howard, R.; Vourlidas, A.; Harrison, R. A.; Bisi, M. M.;
Plunkett, S. P.; Socker, D. G.; Eyles, C. J.; Webb, D. F.; DeForest,
C. E.; Davies, J. A.; Howard, T. A.; de Koning, C. A.; Gopalswamy,
N.; Davila, J. M.; Tappin, J.; Jackson, B. V.
2015AGUFMSH14A..02H Altcode:
Coronal mass ejections (CMEs) have been shown to be the major driver
of the non-recurrent space weather events and geomagnetic storms. The
utility of continuously monitoring such events has been very effectively
demonstrated by the LASCO experiment on the SOHO mission. However SOHO
is aging, having been launched 20 years ago on Dec 2, 1995. The STEREO
mission, in which two spacecraft in orbits about the sun are drifting
away from earth, has shown the utility of multiple viewpoints off the
sun-earth line. Up to now the monitoring of CMES has been performed
by scientific instruments such as LASCO and SECCHI with capabilities
beyond those required to record the parameters that are needed to
forecast the impact at earth. However, there is great interest within
the US NOAA and the UK Met Office to launch operational coronagraphs
to L1 and L5. An ad-hoc group was formed to define the requirements
of the L5 coronagraph. In this paper we present some requirements that
must be met by operational coronagraphs. The Office of Naval Research
is gratefully acknowledged.

---------------------------------------------------------
Title: Evidence of Thermal Conduction Suppression in a Solar Flaring
Loop by Coronal Seismology of Slow-mode Waves
Authors: Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Provornikova,
Elena; Davila, Joseph M.
2015ApJ...811L..13W Altcode: 2015arXiv150900920W
Analysis of a longitudinal wave event observed by the Atmospheric
Imaging Assembly (AIA) onboard the Solar Dynamics Observatory is
presented. A time sequence of 131 Å images reveals that a C-class flare
occurred at one footpoint of a large loop and triggered an intensity
disturbance (enhancement) propagating along it. The spatial features
and temporal evolution suggest that a fundamental standing slow-mode
wave could be set up quickly after meeting of two initial disturbances
from the opposite footpoints. The oscillations have a period of ∼12
minutes and a decay time of ∼9 minutes. The measured phase speed of
500 ± 50 km s-1 matches the sound speed in the heated loop
of ∼10 MK, confirming that the observed waves are of slow mode. We
derive the time-dependent temperature and electron density wave signals
from six AIA extreme-ultraviolet channels, and find that they are nearly
in phase. The measured polytropic index from the temperature and density
perturbations is 1.64 ± 0.08 close to the adiabatic index of 5/3 for
an ideal monatomic gas. The interpretation based on a 1D linear MHD
model suggests that the thermal conductivity is suppressed by at least
a factor of 3 in the hot flare loop at 9 MK and above. The viscosity
coefficient is determined by coronal seismology from the observed wave
when only considering the compressive viscosity dissipation. We find
that to interpret the rapid wave damping, the classical compressive
viscosity coefficient needs to be enhanced by a factor of 15 as the
upper limit.

---------------------------------------------------------
Title: Evidence of thermal conduction depression in hot coronal loops
Authors: Wang, Tongjiang; Ofman, Leon; Sun, Xudong; Provornikova,
Elena; Davila, Joseph
2015IAUGA..2257766W Altcode:
Slow magnetoacoustic waves were first detected in hot (&gt;6 MK) flare
loops by the SOHO/SUMER spectrometer as Doppler shift oscillations in
Fe XIX and Fe XXI lines. These oscillations are identified as standing
slow-mode waves because the estimated phase speeds are close to the
sound speed in the loop and some cases show a quarter period phase
shift between velocity and intensity oscillations. The observed very
rapid excitation and damping of standing slow mode waves have been
studied by many authors using theories and numerical simulations,
however, the exact mechanisms remain not well understood. Recently,
flare-induced longitudinal intensity oscillations in hot post-flare
loops have been detected by SDO/AIA. These oscillations have the
similar physical properties as SUMER loop oscillations, and have
been interpreted as the slow-mode waves. The multi-wavelength AIA
observations with high spatio-temporal resolution and wide temperature
coverage allow us to explore the wave excitation and damping mechanisms
with an unprecedented detail to develope new coronal seismology. In this
paper, we present accurate measurements of the effective adiabatic index
(γeff) in the hot plasma from the electron temperature and
density wave signals of a flare-induced longitudinal wave event using
SDO/AIA data. Our results strikingly and clearly reveal that thermal
conduction is highly depressed in hot (∼10 MK) post-flare loops and
suggest that the compressive viscosity is the dominant wave damping
mechanism which allows determination of the viscosity coefficient from
the observables by coronal seismology. This new finding challenges our
current understanding of thermal energy transport in solar and stellar
flares, and may provide an alternative explanation of long-duration
events and enhance our understand of coronal heating mechanism. We will
discuss our results based on non-ideal MHD theory and simulations. We
will also discuss the flare trigger mechanism based on magnetic topology
derived from SDO/HMI vector magnetic fields using nonlinear force-free
field extrapolations and discuss the wave excitation mechanism based
on 3D MHD modeling of the active region.

---------------------------------------------------------
Title: Variations of the Electron Density of Coronal Streamers with
Solar Cycle Observed with STEREO/COR1
Authors: Wang, Tongjiang; Reginald, Nelson; Davila, Joseph M.
2015IAUGA..2258408W Altcode:
The temporal variations of the total or integrated radiance of the
K-corona of the Sun were found to be correlated with solar activity (or
sunspot) cycle in some previous studies. In this paper, we address the
question on how the global electron content of the corona varies with
the solar cycle, and relates to the evolution of photospheric magnetic
flux and CME mass during Solar Cycle 23/24. We reconstructed the 3D
coronal density from STEREO/COR1 pB images by using a spherically
symmetric polynomial approximation (SSPA) method. The comparisons
show that the SSPA 3D density is consistent well with that obtained
by tomography inversion or by the 3D MHD model. We find that the total
mass of the corona (mainly from streamers) within 1.5-3.7 solar radius
reached a minimum at solar minimum near 2009 and then stayed stable
until 2010 when the solar activity started to again increase. The
coronal mass increased by a factor of about 2 during 2010-2014, compared
to the minimum period and exhibited strong variations. We find that the
variations of total streamer mass are highly correlated with those of
total unsigned magnetic flux measured on the photosphere. In addition,
we also find there is a high correlation between the total coronal mass
and the average mass of CMEs as well as the CME occurrence rate. We will
compare the radial electron density distribution between the streamers
during the solar minimum and solar maximum periods, and discuss their
implication for origin of the slow solar winds. We will also discuss the
origin of coronal mass content in streamers based on 3D MHD modeling.

---------------------------------------------------------
Title: Optimization of Coronal Magnetic Field Extrapolations Using
Images
Authors: Jones, Shaela; Davila, Joseph M.; Uritsky, Vadim M.
2015TESS....120103J Altcode:
The coronal magnetic field plays a significant role in every major
question we have asked about the corona, as well as about other systems
and bodies throughout the heliosphere. Knowledge of the magnetic field
is essential for understanding and predicting many phenomena. Despite
its importance, the coronal magnetic field is not well measured,
due to the tenuous nature of the coronal plasma. In the absence of
reliable coronal measurements, solar physicists have developed many
methods for extrapolating the photospheric magnetic field out into
the corona. However, these extrapolation methods must incorporate
many assumptions, and it has been shown that they do not always
match observed coronal features well.Here we present a new method we
are developing for altering an extrapolated magnetic field to better
agree with features identified in coronal images. Our method proceeds
by iteratively altering the boundary condition (the photospheric
magnetogram) and comparing the extrapolated field to features observed
in coronal images until optimal agreement is reached. This technique
can be used in combination with any extrapolation method, depending
on computational capabilities. By comparing the extrapolations with
coronagraph images (see related submission by Uritsky et al.), it will
be possible to improve determination of sources of open flux in the
inner heliosphere.

---------------------------------------------------------
Title: Turbulent photospheric drivers of multiscale solar corona
Authors: Uritsky, Vadim M.; Ofman, Leon; Davila, Joseph M.
2015TESS....121305U Altcode:
We investigate the collective dynamics of transient photospheric and
coronal events detected using high-resolution solar magnetograms and
coronal emission images. We focus on statistical, ensemble-averaged
properties of the interacting solar regions [Uritsky et al., 2011,
2013, 2014; Uritsky and Davila, 2012], as opposed to case-oriented
methodologies recruited in some previous studies. The behavior
of solar events is studied in the three-dimensional space-time
enabling accurate representation of the event evolution. By applying
advanced data analysis methods including feature tracking algorithms,
multiscale correlation analysis and scaling analysis techniques,
we identify leading physical scenarios of the photosphere - corona
coupling in quiet and active solar regions, and strive to identify
new statistical precursors of coronal eruptions. We also discuss the
possibility of modeling multiscale photosphere - corona interactions
using idealized three-dimensional MHD models. The obtained results
shed a new light on the origin of multiscale dissipation in the
solar corona by enabling quantitative validation of several popular
statistical physical scenarios, such as e.g. intermittent turbulence,
self-organized criticality, and topological complexity.

---------------------------------------------------------
Title: Reconstructing the open-field magnetic geometry of solar
corona using coronagraph images
Authors: Uritsky, Vadim M.; Davila, Joseph M.; Jones, Shaela;
Burkepile, Joan
2015TESS....120106U Altcode:
The upcoming Solar Probe Plus and Solar Orbiter missions will provide an
new insight into the inner heliosphere magnetically connected with the
topologically complex and eruptive solar corona. Physical interpretation
of these observations will be dependent on the accurate reconstruction
of the large-scale coronal magnetic field. We argue that such
reconstruction can be performed using photospheric extrapolation codes
constrained by white-light coronagraph images. The field extrapolation
component of this project is featured in a related presentation by
S. Jones et al. Here, we focus on our image-processing algorithms
conducting an automated segmentation of coronal loop structures. In
contrast to the previously proposed segmentation codes designed for
detecting small-scale closed loops in the vicinity of active regions,
our technique focuses on the large-scale geometry of the open-field
coronal features observed at significant radial distances from the solar
surface. Coronagraph images are transformed into a polar coordinate
system and undergo radial detrending and initial noise reduction
followed by an adaptive angular differentiation. An adjustable threshold
is applied to identify candidate coronagraph features associated with
the large-scale coronal field. A blob detection algorithm is used
to identify valid features against a noisy background. The extracted
coronal features are used to derive empirical directional constraints
for magnetic field extrapolation procedures based on photospheric
magnetograms. Two versions of the method optimized for processing
ground-based (Mauna Loa Solar Observatory) and satellite-based (STEREO
Cor1 and Cor2) coronagraph images are being developed.

---------------------------------------------------------
Title: Spectroscopic Diagnosis of Propagating disturbances in coronal
loops: Waves or flows?
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.
2015arXiv150104082W Altcode:
The analysis of multiwavelength properties of propagating disturbances
(PDs) using Hinode/EIS observations is presented. Quasi-periodic
PDs were mostly interpreted as slow magnetoacoustic waves in early
studies, but recently suggested to be intermittent upflows of the
order of 50-150 km/s based on the Red-Blue (RB) asymmetry analysis of
spectral line profiles. Using the forward models, velocities of the
secondary component derived from the RB analysis are found significantly
overestimated due to the saturation effect when its offset velocities
are smaller than the Gaussian width. We developed a different method
to examine spectral features of the PDs. This method is assuming that
the excessive emission of the PD profile against the background (taken
as that prior to the PD) is caused by a hypothetic upflow. The derived
LOS velocities of the flow are on the order of 10-30 km/s from the warm
(1-1.5 MK) coronal lines, much smaller than those inferred from the
RB analysis. This result does not support the flow interpretation but
favors of the early wave interpretation.

---------------------------------------------------------
Title: New Approaches to Externally Occulted Coronagraphs
Authors: Rabin, D. M.; Chamberlin, P. C.; Davila, J. M.; Shah, N.
2014AGUFMSH53B4226R Altcode:
The rapidly advancing capabilities of low-cost space platforms
prompts us to reconsider concepts for externally occulted solar
coronagraphs. Placing the occulter on a separate platform offers
superior diffraction control but requires an analysis of alignment
and separation tolerances that is different from that applied to
conventional architectures. New forms of occulter (e.g., an inflatable
sphere or ellipsoid) have potential advantages such as low mass and
fabrication cost, simple deployment, and less stringent demands on
the relative alignment of the platforms. However, the diffraction
behavior of occulters that incorporate curved surfaces (Buffington
2000) is less explored than for edge-type occulters. We illustrate
the new possibilities by calculating the performance of some candidate
systems using an analytic framework adapted from radio wave propagation
(Vogler 1985) and alignment tolerances based on a recent concept for
a two-platform guidance, navigation, and control system.

---------------------------------------------------------
Title: Exploring the Photon Sieve: Mathematical Framework and
Experimental Categorization
Authors: O'Neill, J. F., Jr.; Davila, J. M.; Oktem, F.; Daw, A. N.
2014AGUFMSH53B4234O Altcode:
The photon sieve is a diffractive optical element similar to a
Fresnel zone plate, however instead of alternating rings of opaque and
transmissive material the sieve is made up of many holes arranged in
concentric circles. A sieve provides diffraction-limited resolution
where traditional reflective and refractive optics are unable to,
such as in the extreme ultraviolet. We present here recent results of
testing the photon sieve's properties and comparing them to theory. Such
results include multiple wavelengths, point spread function analysis,
and off axis imaging. We also investigate the case in which there are
multiple solar spectral lines near the sieve's depth of focus. The image
observed will be a combination of multiple distinct spectral lines with
different intrinsic blurs. Separating these lines is mathematically
similar to an inverse problem we developed for slitless spectroscopy
and is considered within this same framework.

---------------------------------------------------------
Title: Automated tracing of open-field coronal structures for an
optimized large-scale magnetic field reconstruction
Authors: Uritsky, V. M.; Davila, J. M.; Jones, S. I.
2014AGUFMSH21B4108U Altcode:
Solar Probe Plus and Solar Orbiter will provide detailed measurements
in the inner heliosphere magnetically connected with the topologically
complex and eruptive solar corona. Interpretation of these measurements
will require accurate reconstruction of the large-scale coronal magnetic
field. In a related presentation by S. Jones et al., we argue that such
reconstruction can be performed using photospheric extrapolation methods
constrained by white-light coronagraph images. Here, we present the
image-processing component of this project dealing with an automated
segmentation of fan-like coronal loop structures. In contrast to the
existing segmentation codes designed for detecting small-scale closed
loops in the vicinity of active regions, we focus on the large-scale
geometry of the open-field coronal features observed at significant
radial distances from the solar surface. The coronagraph images used for
the loop segmentation are transformed into a polar coordinate system and
undergo radial detrending and initial noise reduction. The preprocessed
images are subject to an adaptive second order differentiation combining
radial and azimuthal directions. An adjustable thresholding technique
is applied to identify candidate coronagraph features associated with
the large-scale coronal field. A blob detection algorithm is used to
extract valid features and discard noisy data pixels. The obtained
features are interpolated using higher-order polynomials which are
used to derive empirical directional constraints for magnetic field
extrapolation procedures based on photospheric magnetograms.

---------------------------------------------------------
Title: Slitless Spectroscopy: Inverse Solutions With Overlapping Lines
Authors: Davila, J. M.; O'Neill, J. F., Jr.
2014AGUFMSH53B4216D Altcode:
Spectrometers provide our most detailed diagnostics of the solar coronal
plasma, and spectral data is routinely used to measure the temperature,
density, and flow velocity in coronal features. However spectrographs
suffer from a limited instantaneous field-of-view (IFOV), and imaging
instruments, on the other hand, can provide a relatively large IFOV
but offer only very limited spectral resolution. In previous work,
synthetic data was produced which had spectral properties derived
from the observations of the Hinode/EIS spectrometer. We assumed
observations in multiple spectral orders, then used an inverse problem
method to infer the spectral properties of the solar source. Physical
constraints and regularization derived from prior knowledge were
incorporated as part of the solution process. However in previous work
a single emission line without overlapping from neighboring lines was
assumed. In this paper we present solutions of a more realistic case
solving for spectral line intensity, Doppler shift, and Gaussian width
in the case where overlapping lines are present.

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Title: High-Resolution Solar Imaging With Photon Sieves
Authors: Oktem, F. S.; Kamalabadi, F.; Davila, J. M.
2014AGUFMSH53B4219O Altcode:
A photon sieve is a modification of a Fresnel zone plate in which open
zones are replaced by a large number of circular holes. This lightweight
optical device offers a superior image forming capability compared with
the Fresnel zone plate, and is specially suited to observations at UV
and x-ray wavelengths where refractive lenses are not available due to
strong absorption of materials, and reflective mirrors are difficult
to manufacture to achieve near diffraction-limited resolution. At
these shorter wavelengths, photon sieves enable diffraction-limited
imaging performance with relaxed manufacturing tolerances, and simple
and low-cost fabrication. In this work, we present a new photon sieve
imaging modality that, unlike previous designs, takes advantage of
chromatic aberration. The fact that different wavelengths are focused
at different distances from photon sieve is exploited to develop a
novel multi-spectral imaging technique. The idea is to use a photon
sieve imaging system with a moving detector which records images at
different planes. Each measurement consists of superimposed images of
different wavelengths, with each individual image being either in focus
or out of focus. For spatially incoherent illumination, we study the
problem of recovering the individual images from these superimposed
measurements. We first formulate the discrete forward problem using
the closed-form Fresnel imaging formulas. The inverse problem is then
a multi-frame deconvolution problem involving multiple objects, and
is formulated as a maximum posterior estimation problem. The resulting
nonlinear optimization problem is solved using a fixed-point iterative
algorithm. In contrast to traditional spectral imagers employing a
series of wavelength filters, the proposed technique relies on a simple
optical system, but incorporates powerful image processing methods to
form spectral images computationally. In addition to diffraction-limited
high spatial resolution enabled by photon sieves, this technique can
also achieve higher spectral resolution than the conventional spectral
imagers, since the technique offers the possibility of separating
nearby spectral components that would not otherwise be possible using
wavelength filters. These promising aspects are illustrated for solar
EUV spectral imaging.

---------------------------------------------------------
Title: Image-Optimized Coronal Magnetic Field Reconstructions
Authors: Jones, S. I.; Davila, J. M.; Uritsky, V. M.
2014AGUFMSH21B4120J Altcode:
The magnetic field dominates many of the most important and puzzling
processes in the corona. In the absence of direct measurements, solar
physicists have struggled for decades to accurately reconstruct the
coronal magnetic field using photospheric magnetograms. Even with
today's excellent magnetographs, these reconstructions are plagued by
several problems, among them long computation time, and poor agreement
with the structures seen in EUV and coronagraph images. However no
method exists for systematically improving the agreement between
coronal images and magnetic reconstructions. Solar Orbiter and Solar
Probe Plus will bring us closer to the sun we have ever been before,
but taking full advantage of that opportunity requires accurate coronal
magnetic field reconstructions so that we can connect the in situ
observations offered by these unique missions to magnetic sources at
the surface of the Sun. In this study we propose a method to improve
coronal magnetic field reconstructions by optimizing agreement between
the reconstructed field and white-light coronagraph images.

---------------------------------------------------------
Title: Global Variation of the Coronal Electron Density with Solar
Cycle and its Comparison with 3D MHD Modeling
Authors: Reginald, N. L.; Wang, T.; Davila, J. M.
2014AGUFMSH33A4123R Altcode:
The temporal variations of the total or integrated radiance of the
K-corona were found to be correlated with solar activity (or sunspot)
cycle in some previous studies. In this study, we address the question
on how the global electron content of the corona varies with the solar
cycle by analyzing STEREO/COR1 pB images over a period from 2007 (near
solar minimum of Solar Cycle 23) to 2014 (near solar maximum of Solar
Cycle 24). We reconstruct the 3D coronal density by using a spherically
symmetric polynomial approximation (SSPA) method on the COR1-A and
-B data gathered over half a solar rotation. We find that the total
mass of the corona within 1.5-3.7 solar radius reaches a minimum at
solar minimum near 2009 and then stays stable until 2010 when the solar
activity starts to again increase. The coronal mass is seen to increase
by a factor ≈2 from solar minimum to solar maximum while exhibiting
strong variations. We explore the cause of this variation by exploring
its relationship with the temporal variation of total magnetic flux
of the close fields using PFSS extrapolations to SOHO/MDI and SDO/MHI
magnetic field data. In addition, for some selected solar rotations we
compare the reconstructed 3D density structures with density structures
predicted by the Corona Heliosphere (CORHEL) and Magnetohydrodynamics
Around the Sphere (MAS) models in the Community Coordinated Modeling
Center (CCMC) to understand the physical mechanism that determines
the distribution and evolution of the coronal densities.

---------------------------------------------------------
Title: Slitless Solar Spectroscopy
Authors: Kamalabadi, F.; Oktem, F. S.; Davila, J. M.
2014AGUFMSH53B4215K Altcode:
Spectrometers provide our most detailed diagnostics of the solar coronal
plasma, and spectral data is routinely used to measure the temperature,
density, and flow velocity of coronal features. However, spectrographs
suffer from a limited instantaneous field-of-view (FOV). Imaging
instruments can provide a large FOV but offer only very limited
spectral resolution. In this work, we present an instrument concept that
combines the strengths of these two instrument classes, i.e., a large
FOV and high spectral resolution. Our approach is based on computational
imaging, which involves distributing the spectral imaging task between
a physical and a computational system, and then digitally forming images
of interest from multiplexed measurements by means of solving an inverse
problem. In particular, a nonscanning spectral imaging technique is
developed to enable performing spectroscopy over a two-dimensional
instantaneous field-of-view. This technique combines a parametric
estimation approach with a slitless spectrometer configuration. The
associated inverse problem, which can be viewed as a multiframe image
deblurring problem, is formulated in a Bayesian estimation framework
and computationally efficient algorithms are designed to solve the
resulting nonlinear optimization problems. Furthermore, statistical
bounds are obtained to characterize the estimation uncertainties and
performance limits, and to explore the optimized system design for
specific observing requirements. We illustrate that such an instrument
concept will facilitate the investigation of highly dynamic solar
phenomena such as flares, CMEs, and transient brightening, with a
significant reduction in hardware cost and complexity, but at an
accuracy comparable with conventional designs.

---------------------------------------------------------
Title: 3D Coronal Density Reconstruction and Retrieving Coronal
Magnetic Field Structures during Solar Minimum and Maximum
Authors: Kramar, M.; Airapetian, V.; Davila, J. M.
2014AGUFMSH13A4068K Altcode:
Measurement of the coronal magnetic field is a crucial ingredient in
understanding the nature of solar coronal phenomena at all scales. We
employ STEREO/COR1 data obtained during minimum and maximum of solar
activity (Carrington rotations, CR, 2066 and 2131) to retrieve and
analyze the three-dimensional (3D) coronal electron density in the
range of heights from 1.5 to 4 Rsun using the tomography method and
qualitatively deduce structures of the coronal magnetic field. The
3D electron density analysis is complemented by the 3D STEREO/EUVI
emissivity in 195 A band obtained by tomography for the same CR
periods. A global 3D thermodynamic MHD model of the solar corona
was used to relate the reconstructed 3D density and emissivity to
open/closed magnetic field structures. We show that the locations of
density maximum can serve as an indicator of current sheet position,
while the locations of the maximum of the density gradient can be a
reliable indicator of closed-open magnetic field boundaries. We find
that the magnetic field configuration during CR 2066 has a tendency
to become radially open at heliocentric distances above 2.5 Rsun. We
also find that the potential field model with a fixed source surface
(PFSS) is not consistent with the positions of the boundaries between
the regions with open and closed magnetic field structures. This
indicates that the assumption of the potential nature of the coronal
global magnetic field is not satisfied even during the deep solar
minimum. Results of our 3D density reconstruction will help to constrain
solar coronal field models and test the accuracy of the magnetic field
approximations for coronal modeling.

---------------------------------------------------------
Title: SDO/AIA Observation and Modeling of Flare-excited Slow Waves
in Hot Coronal Loops
Authors: Wang, T.; Ofman, L.; Provornikova, E.; Sun, X.; Davila, J. M.
2014AGUFMSH13A4074W Altcode:
The flare-excited standing slow waves were first detected by SOHO/SUMER
as Doppler shift oscillations in hot (&gt;6 MK) coronal loops. It has
been suggested that they are excited by small or micro- flares at one
loop's footpoint. However, the detailed excitation mechanism remains
unclear. In this study, we report an oscillation event observed by
SDO/AIA in the 131 channel. The intensity disturbances excited by a
C-class flare propagated back and forth along a hot loop for about two
period with a strong damping. From the measured oscillation period
and loop length, we estimate the wave phase speed to be about 410
km/s. Using a regularized DEM analysis we determine the loop temperature
and electron density evolution and find that the loop plasma is heated
to a temperature of 8-12 MK with a mean about 9 MK. These measurements
support the interpretation as slow magnetoacousic waves. Magnetic
field extrapolation suggests that the flare is triggered by slipping
and null-point-type reconnections in a fan-spine magnetic topology, and
the injected (or impulsively evaporated) hot plasmas flowing along the
large spine field lines form the oscillating hot loops. To understand
why the propagating waves but not the standing waves as observed
previously are excited in this event, we preform simulations using a
3D MHD model based on the observed magnetic configuration including
full energy equation. Our simulations indicate that the nature of
loop temperature structure is critical for the excitation of whether
propagating or standing waves in a hot loop. Our result demonstrates
that the slow waves may be used for heating diagnostics of coronal
loops with coronal seismology. We also discuss the application of
coronal seismology for estimating the average magnetic field strength
in the hot loop based on the observed slow waves.

---------------------------------------------------------
Title: Spatiotemporal Organization of Energy Release Events in the
Quiet Solar Corona
Authors: Uritsky, Vadim M.; Davila, Joseph M.
2014ApJ...795...15U Altcode: 2014arXiv1404.1086U
Using data from the STEREO and SOHO spacecraft, we show that
temporal organization of energy release events in the quiet solar
corona is close to random, in contrast to the clustered behavior of
flaring times in solar active regions. The locations of the quiet-Sun
events follow the meso- and supergranulation pattern of the underling
photosphere. Together with earlier reports of the scale-free event size
statistics, our findings suggest that quiet solar regions responsible
for bulk coronal heating operate in a driven self-organized critical
state, possibly involving long-range Alfvénic interactions.

---------------------------------------------------------
Title: Validation of Spherically Symmetric Inversion by Use of a
Tomographically Reconstructed Three-Dimensional Electron Density of
the Solar Corona
Authors: Wang, Tongjiang; Davila, Joseph M.
2014SoPh..289.3723W Altcode: 2014arXiv1404.5925W; 2014SoPh..tmp...95W
Determining the coronal electron density by the inversion of white-light
polarized brightness (pB) measurements by coronagraphs is a classic
problem in solar physics. An inversion technique based on the
spherically symmetric geometry (spherically symmetric inversion,
SSI) was developed in the 1950s and has been widely applied to
interpret various observations. However, to date there is no study
of the uncertainty estimation of this method. We here present the
detailed assessment of this method using a three-dimensional (3D)
electron density in the corona from 1.5 to 4 R⊙ as a
model, which is reconstructed by a tomography method from STEREO/COR1
observations during the solar minimum in February 2008 (Carrington
Rotation, CR 2066). We first show in theory and observation that the
spherically symmetric polynomial approximation (SSPA) method and the
Van de Hulst inversion technique are equivalent. Then we assess the
SSPA method using synthesized pB images from the 3D density model,
and find that the SSPA density values are close to the model inputs
for the streamer core near the plane of the sky (POS) with differences
generally smaller than about a factor of two; the former has the lower
peak but extends more in both longitudinal and latitudinal directions
than the latter. We estimate that the SSPA method may resolve the
coronal density structure near the POS with angular resolution in
longitude of about 50°. Our results confirm the suggestion that
the SSI method is applicable to the solar minimum streamer (belt),
as stated in some previous studies. In addition, we demonstrate that
the SSPA method can be used to reconstruct the 3D coronal density,
roughly in agreement with the reconstruction by tomography for a period
of low solar activity (CR 2066). We suggest that the SSI method is
complementary to the 3D tomographic technique in some cases, given
that the development of the latter is still an ongoing research effort.

---------------------------------------------------------
Title: 3D Coronal Density Reconstruction and Retrieving the Magnetic
Field Structure during Solar Minimum
Authors: Kramar, M.; Airapetian, V.; Mikić, Z.; Davila, J.
2014SoPh..289.2927K Altcode: 2014SoPh..tmp...63K; 2014arXiv1405.0951K
Measurement of the coronal magnetic field is a crucial ingredient in
understanding the nature of solar coronal phenomena at all scales. We
employed STEREO/COR1 data obtained during a deep minimum of solar
activity in February 2008 (Carrington Rotation CR 2066) to retrieve
and analyze the three-dimensional (3D) coronal electron density in
the range of heights from 1.5 to 4 R⊙ using a tomography
method. With this, we qualitatively deduced structures of the coronal
magnetic field. The 3D electron-density analysis is complemented
by the 3D STEREO/EUVI emissivity in the 195 Å band obtained by
tomography for the same CR. A global 3D MHD model of the solar corona
was used to relate the reconstructed 3D density and emissivity to
open/closed magnetic-field structures. We show that the density-maximum
locations can serve as an indicator of current-sheet position, while the
locations of the density-gradient maximum can be a reliable indicator of
coronal-hole boundaries. We find that the magnetic-field configuration
during CR 2066 has a tendency to become radially open at heliocentric
distances greater than 2.5 R⊙. We also find that the
potential-field model with a fixed source surface is inconsistent with
the boundaries between the regions with open and closed magnetic-field
structures. This indicates that the assumption of the potential nature
of the coronal global magnetic field is not satisfied even during the
deep solar minimum. Results of our 3D density reconstruction will help
to constrain solar coronal-field models and test the accuracy of the
magnetic-field approximations for coronal modeling.

---------------------------------------------------------
Title: Ground Level Enhancement in the 2014 January 6 Solar Energetic
Particle Event
Authors: Thakur, N.; Gopalswamy, N.; Xie, H.; Mäkelä, P.; Yashiro,
S.; Akiyama, S.; Davila, J. M.
2014ApJ...790L..13T Altcode: 2014arXiv1406.7172T
We present a study of the 2014 January 6 solar energetic particle event
which produced a small ground level enhancement (GLE), making it the
second GLE of this unusual solar cycle 24. This event was primarily
observed by the South Pole neutron monitors (increase of ~2.5%) while a
few other neutron monitors recorded smaller increases. The associated
coronal mass ejection (CME) originated behind the western limb and
had a speed of 1960 km s-1. The height of the CME at the
start of the associated metric type II radio burst, which indicates
the formation of a strong shock, was measured to be 1.61 Rs using a
direct image from STEREO-A/EUVI. The CME height at the time of the GLE
particle release (determined using the South Pole neutron monitor data)
was directly measured as 2.96 Rs based on STEREO-A/COR1 white-light
observations. These CME heights are consistent with those obtained for
GLE71, the only other GLE of the current cycle, as well as cycle-23 GLEs
derived using back-extrapolation. GLE72 is of special interest because
it is one of only two GLEs of cycle 24, one of two behind-the-limb GLEs,
and one of the two smallest GLEs of cycles 23 and 24.

---------------------------------------------------------
Title: Performance Measurements of an Intensified APS Detector for
SPICE on Solar Orbiter
Authors: Thompson, William T.; Davila, Joseph M.; Woytko, Gregory;
Devlin, Thomas; Jordan, Patrick; Rosanova, Alberto; Chang, William;
Reginald, Nelson Leslie; Plummer, Thomas; Haas, Patrick; Caldwell,
Martin; Anderson, Mark; Eccleston, Paul; Griffin, Douglas; Siegmund,
Oswald
2014AAS...22412357T Altcode:
The Spectral Imaging of the Coronal Environment (SPICE) instrument for
the Solar Orbiter mission will make spectroscopic observations of the
Sun's low corona to characterize the plasma properties of the source
regions of the solar wind. The detector package for SPICE, provided by
the NASA Goddard Space FLight Center, consists of two microchannel-plate
(MCP) intensified Active Pixel Sensor (APS) detectors covering the
short (702-792 Angstroms) and long (972-1050 Angstroms) wavelength
bandpasses. The long wavelength detector will also provide coverage in
second order between 485-525 Angstroms. We report here on measurements
made on the engineering model of the SPICE detector in a vacuum tank
facility at the Rutherford Appleton Laboratory in Harwell, UK. These
measurements include the detector flat field, sensitivity, resolution,
linearity, and statistical noise. A krypton resonance lamp operating
at 1236 Angstroms was used to stimulate the detector. Results at this
wavelength are combined with the quantum efficiency measurements
of the individual MCPs at this and other wavelengths covering the
entire wavelength range to provide a complete calibration curve for
the instrument. A calibrated NIST photodiode was used to determine
the absolute brightness of the lamp.

---------------------------------------------------------
Title: Validation of Spherically Symmetric Inversion by Use of a
Tomographic Reconstructed Three-Dimensional Electron Density of the
Solar Corona
Authors: Wang, Tongjiang; Kramar, Maxim; Davila, Joseph M.
2014AAS...22432330W Altcode:
Determination of the coronal electron density by the inversion of
white-light polarized brightness (pB) measurements by coronagraphs is a
classic problem in solar physics. An inversion technique based on the
spherically symmetric geometry (Spherically Symmetric Inversion, SSI)
was developed in the 1950s, and has been widely applied to interpret
various observations. In this study we present the detailed assessment
of this method using a model in terms of three-dimensional (3D)
electron density in the corona from 1.5 to 4 solar radii reconstructed
by tomography method from STEREO/COR1 observations. We first show
in theory and observation that the spherically symmetric polynomial
approximation (SSPA) method and the Van de Hulst inversion technique
are equivalent. Then we assess the SSPA method using synthesized pB
images from the 3D density model, and find that the SSPA density values
for edge-on streamers are very close to the model inputs in the plane
of sky with differences generally less than a factor of two or so; the
SSPA density has the lower peak but more spread in latitudinal direction
than in the model. Our results confirm the previous suggestion that
the SSI method is very suitable to streamers in the solar minimum. In
addition, we demonstrate that the SSPA method can be used to reconstruct
the 3D coronal density, roughly in agreement with that by tomography
in a period of low solar activity. We suggest that the SSI method is
complementary to the 3D tomographic technique in some cases, given
that the development of the latter is still an ongoing research effort.

---------------------------------------------------------
Title: Evaluating the Uncertainties in the Electron Temperature
and Radial Speed Measurements Using White Light Corona Eclipse
Observations
Authors: Reginald, Nelson L.; Davila, Joseph M.; St. Cyr, O. C.;
Rastaetter, Lutz
2014SoPh..289.2021R Altcode: 2014SoPh..tmp....4R
We examine the uncertainties in two plasma parameters from their
true values in a simulated asymmetric corona. We use the Corona
Heliosphere (CORHEL) and Magnetohydrodynamics Around the Sphere
(MAS) models in the Community Coordinated Modeling Center (CCMC) to
investigate the differences between an assumed symmetric corona and a
more realistic, asymmetric one. We were able to predict the electron
temperatures and electron bulk flow speeds to within ± 0.5 MK and
± 100 km s−1, respectively, over coronal heights up to
5.0 R⊙ from Sun center. We believe that this technique
could be incorporated in next-generation white-light coronagraphs to
determine these electron plasma parameters in the low solar corona. We
have conducted experiments in the past during total solar eclipses
to measure the thermal electron temperature and the electron bulk
flow speed in the radial direction in the low solar corona. These
measurements were made at different altitudes and latitudes in the low
solar corona by measuring the shape of the K-coronal spectra between
350 nm and 450 nm and two brightness ratios through filters centered
at 385.0 nm/410.0 nm and 398.7 nm/423.3 nm with a bandwidth of ≈
4 nm. Based on symmetric coronal models used for these measurements,
the two measured plasma parameters were expected to represent those
values at the points where the lines of sight intersected the plane
of the solar limb.

---------------------------------------------------------
Title: SDO/AIA observations and model of standing waves in hot
coronal loops excited by a flare
Authors: Wang, Tongjiang; Ofman, Leon; Provornikova, Elena; Davila,
Joseph M.
2014AAS...22432354W Altcode:
The strongly damped Doppler shift oscillations in hot coronal loops
were first observed by SOHO/SUMER in flare lines formed at plasma
temperature more than 6 MK. They were mainly interpreted as the
standing slow magnetosonic waves excited by impulsive energy release
at the loop’s footpoint based on the measured properties and on MHD
modeling results. Longitudinal waves with similar properties have been
recently observed by SDO/AIA in active region loops. In this study,
we report a new event that exhibited the flare-excited intensity
disturbances propagating back and forth in a hot coronal loop imaged by
AIA in 131 bandpass. We measure the physical parameters of the wave and
loop plasma, determine the loop geometry, and explore the triggering
mechanism. We identify the wave modes (propagating or standing waves)
based on these measurements and on 3D MHD modeling. A loop model
is constructed with enhanced density in a hydrostatic equilibrium
following potential or force-free magnetic field lines extrapolated
from the photospheric magnetic field data observed by SDO/HMI. We also
discuss the applications of coronal seismology to this event.

---------------------------------------------------------
Title: Slitless Solar Spectroscopy
Authors: O'Neill, John Francis; Davila, Joseph M.; Oktem, Figen S
2014AAS...22412359O Altcode:
Spectrographs have traditionally suffered from the inability to obtain
line intensities, widths, and Doppler shifts over large spatial
regions of the Sun quickly because of their narrow instantaneous
field of view. This has limited the spectroscopic analysis of rapidly
varying solar features like, flares, CME eruptions, coronal jets,
and reconnection regions. Imagers, on the other hand, have provided
high time resolution images of the full Sun with limited spectral
resolution.In this paper we present recent advances in deconvolving
spectrally dispersed images obtained through broad slits. We use this
new theoretical formulation to examine the effectiveness of various
potential observing scenarios, spatial and spectral resolutions,
signal to noise ratio, and other instrument characteristics. We test
this method on two specific observing scenarios.With the original
method developed for the single spectral line case, we first analyze
the effect of overlapping spectral lines on the resulting spectral
parameters. Second, we determine how well the method performs when
given dispersed image input with either three orders (0, +1, -1),
or with two orders (0, +1). In both cases a more accurate Gauss
error function calculation is employed on the dispersed images. This
information will lay the foundation for a new generation of spectral
imagers optimized for slitless spectral operation, enabling us to
obtain spectral information in transient solar events.

---------------------------------------------------------
Title: Slitless Spectroscopy
Authors: Davila, J. M.; O'Neill, J. F.
2013AGUFMSM52A..05D Altcode:
Spectrographs provide a unique window into plasma parameters in the
solar atmosphere. In fact spectrographs provide the most accurate
measurements of plasma parameters such as density, temperature, and
flow speed. However, traditionally spectrographic instruments have
suffered from the inability to cover large spatial regions of the Sun
quickly. To cover an active region sized spatial region, the slit must
be rastered over the area of interest with an exposure taken at each
pointing location. Because of this long cycle time, the spectra of
dynamic events like flares, CME initiations, or transient brightening
are obtained only rarely. And even if spectra are obtained they are
either taken over an extremely small spatial region, or the spectra
are not co-temporal across the raster. Either of these complicates
the interpretation of the spectral raster results. Imagers are able
to provide high time and spatial resolution images of the full Sun
but with limited spectral resolution. The telescopes onboard the
Solar Dynamics Observatory (SDO) normally take a full disk solar image
every 10 seconds with roughly 1 arcsec spatial resolution. However the
spectral resolution of the multilayer imagers on SDO is of order 100
times less than a typical spectrograph. Because of this it is difficult
to interpret multilayer imaging data to accurately obtain plasma
parameters like temperature and density from these data, and there
is no direct measure of plasma flow velocity. SERTS and EIS partially
addressed this problem by using a wide slit to produce monochromatic
images with limited FOV to limit overlapping. However dispersion
within the wide slit image remained a problem which prevented the
determination of intensity, Doppler shift, and line width in the wide
slit. Kankelborg and Thomas introduced the idea of using multiple images
-1, 0, and +1 spectral orders of a single emission line. This scheme
provided three independent images to measure the three spectral line
parameters in each pixel with the Multi-Order Solar EUV Spectrograph
(MOSES) instrument. We suggest a reconstruction approach based on
tomographic methods with regularization. Preliminary results show
that the typical Doppler shift and line width error introduced by the
reconstruction method is of order a few km/s at 300 A. This is on the
order of the error obtained in narrow slit spectrographs but with data
obtained over a two-dimensional field of view.

---------------------------------------------------------
Title: Measuring Temperature-dependent Propagating Disturbances in
Coronal Fan Loops Using Multiple SDO/AIA Channels and the Surfing
Transform Technique
Authors: Uritsky, Vadim M.; Davila, Joseph M.; Viall, Nicholeen M.;
Ofman, Leon
2013ApJ...778...26U Altcode: 2013arXiv1308.6195U
A set of co-aligned high-resolution images from the Atmospheric
Imaging Assembly (AIA) on board the Solar Dynamics Observatory is
used to investigate propagating disturbances (PDs) in warm fan loops
at the periphery of a non-flaring active region NOAA AR 11082. To
measure PD speeds at multiple coronal temperatures, a new data
analysis methodology is proposed enabling a quantitative description
of subvisual coronal motions with low signal-to-noise ratios of the
order of 0.1%. The technique operates with a set of one-dimensional
"surfing" signals extracted from position-time plots of several AIA
channels through a modified version of Radon transform. The signals are
used to evaluate a two-dimensional power spectral density distribution
in the frequency-velocity space that exhibits a resonance in the
presence of quasi-periodic PDs. By applying this analysis to the same
fan loop structures observed in several AIA channels, we found that
the traveling velocity of PDs increases with the temperature of the
coronal plasma following the square-root dependence predicted for slow
mode magneto-acoustic waves which seem to be the dominating wave mode in
the loop structures studied. This result extends recent observations by
Kiddie et al. to a more general class of fan loop system not associated
with sunspots and demonstrating consistent slow mode activity in up
to four AIA channels.

---------------------------------------------------------
Title: Solar Eruptive Events (SEE) 2020 Mission Concept
Authors: Lin, R. P.; Caspi, A.; Krucker, S.; Hudson, H.; Hurford,
G.; Bandler, S.; Christe, S.; Davila, J.; Dennis, B.; Holman, G.;
Milligan, R.; Shih, A. Y.; Kahler, S.; Kontar, E.; Wiedenbeck, M.;
Cirtain, J.; Doschek, G.; Share, G. H.; Vourlidas, A.; Raymond, J.;
Smith, D. M.; McConnell, M.; Emslie, G.
2013arXiv1311.5243L Altcode:
Major solar eruptive events (SEEs), consisting of both a large flare and
a near simultaneous large fast coronal mass ejection (CME), are the most
powerful explosions and also the most powerful and energetic particle
accelerators in the solar system, producing solar energetic particles
(SEPs) up to tens of GeV for ions and hundreds of MeV for electrons. The
intense fluxes of escaping SEPs are a major hazard for humans in space
and for spacecraft. Furthermore, the solar plasma ejected at high speed
in the fast CME completely restructures the interplanetary medium
(IPM) - major SEEs therefore produce the most extreme space weather
in geospace, the interplanetary medium, and at other planets. Thus,
understanding the flare/CME energy release process(es) and the related
particle acceleration processes are major goals in Heliophysics. To
make the next major breakthroughs, we propose a new mission concept,
SEE 2020, a single spacecraft with a complement of advanced new
instruments that focus directly on the coronal energy release and
particle acceleration sites, and provide the detailed diagnostics of
the magnetic fields, plasmas, mass motions, and energetic particles
required to understand the fundamental physical processes involved.

---------------------------------------------------------
Title: Global Coronal Seismology in the Extended Solar Corona through
Fast Magnetosonic Waves Observed by STEREO SECCHI COR1
Authors: Kwon, Ryun-Young; Kramar, Maxim; Wang, Tongjiang; Ofman,
Leon; Davila, Joseph M.; Chae, Jongchul; Zhang, Jie
2013ApJ...776...55K Altcode:
We present global coronal seismology for the first time, which allows
us to determine inhomogeneous magnetic field strength in the extended
corona. From the measurements of the propagation speed of a fast
magnetosonic wave associated with a coronal mass ejection (CME)
and the coronal background density distribution derived from the
polarized radiances observed by the STEREO SECCHI COR1, we determined
the magnetic field strengths along the trajectories of the wave at
different heliocentric distances. We found that the results have an
uncertainty less than 40%, and are consistent with values determined
with a potential field model and reported in previous works. The
characteristics of the coronal medium we found are that (1) the density,
magnetic field strength, and plasma β are lower in the coronal hole
region than in streamers; (2) the magnetic field strength decreases
slowly with height but the electron density decreases rapidly so that
the local fast magnetosonic speed increases while plasma β falls off
with height; and (3) the variations of the local fast magnetosonic
speed and plasma β are dominated by variations in the electron
density rather than the magnetic field strength. These results imply
that Moreton and EIT waves are downward-reflected fast magnetosonic
waves from the upper solar corona, rather than freely propagating
fast magnetosonic waves in a certain atmospheric layer. In addition,
the azimuthal components of CMEs and the driven waves may play an
important role in various manifestations of shocks, such as type II
radio bursts and solar energetic particle events.

---------------------------------------------------------
Title: Vector Tomography for the Coronal Magnetic Field. II. Hanle
Effect Measurements
Authors: Kramar, M.; Inhester, B.; Lin, H.; Davila, J.
2013ApJ...775...25K Altcode:
In this paper, we investigate the feasibility of saturated coronal
Hanle effect vector tomography or the application of vector tomographic
inversion techniques to reconstruct the three-dimensional magnetic field
configuration of the solar corona using linear polarization measurements
of coronal emission lines. We applied Hanle effect vector tomographic
inversion to artificial data produced from analytical coronal magnetic
field models with equatorial and meridional currents and global coronal
magnetic field models constructed by extrapolation of real photospheric
magnetic field measurements. We tested tomographic inversion with
only Stokes Q, U, electron density, and temperature inputs to simulate
observations over large limb distances where the Stokes I parameters
are difficult to obtain with ground-based coronagraphs. We synthesized
the coronal linear polarization maps by inputting realistic noise
appropriate for ground-based observations over a period of two weeks
into the inversion algorithm. We found that our Hanle effect vector
tomographic inversion can partially recover the coronal field with a
poloidal field configuration, but that it is insensitive to a corona
with a toroidal field. This result demonstrates that Hanle effect
vector tomography is an effective tool for studying the solar corona
and that it is complementary to Zeeman effect vector tomography for
the reconstruction of the coronal magnetic field.

---------------------------------------------------------
Title: Three-dimensional Magnetohydrodynamic Modeling of Propagating
Disturbances in Fan-like Coronal Loops
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.
2013ApJ...775L..23W Altcode: 2013arXiv1308.0282W
Quasi-periodic propagating intensity disturbances (PDs) have been
observed in large coronal loops in EUV images over a decade, and are
widely accepted to be slow magnetosonic waves. However, spectroscopic
observations from Hinode/EIS revealed their association with persistent
coronal upflows, making this interpretation debatable. Motivated by the
scenario that the coronal upflows could be the cumulative result of
numerous individual flow pulses generated by sporadic heating events
(nanoflares) at the loop base, we construct a velocity driver with
repetitive tiny pulses, whose energy frequency distribution follows
the flare power-law scaling. We then perform three-dimensional MHD
modeling of an idealized bipolar active region by applying this
broadband velocity driver at the footpoints of large coronal loops
which appear open in the computational domain. Our model successfully
reproduces the PDs with similar features as the observed, and shows
that any upflow pulses inevitably excite slow magnetosonic wave
disturbances propagating along the loop. We find that the generated
PDs are dominated by the wave signature as their propagation speeds
are consistent with the wave speed in the presence of flows, and the
injected flows rapidly decelerate with height. Our simulation results
suggest that the observed PDs and associated persistent upflows may
be produced by small-scale impulsive heating events (nanoflares) at
the loop base in the corona, and that the flows and waves may both
contribute to the PDs at lower heights.

---------------------------------------------------------
Title: Fast Magnetosonic Waves and Global Coronal Seismology in the
Extended Solar Corona
Authors: Kwon, Ryun Young; Zhang, J.; Kramar, M.; Wang, T.; Ofman,
L.; Davila, J. M.
2013SPD....4410303K Altcode:
We present global coronal seismology, for the first time, that
allows us to determine inhomogeneous magnetic field strengths in
a wide range of the extended solar corona. We use observations of
propagating disturbance associated with a coronal mass ejection
observed on 2011 August 4 by the COR1 inner coronagraphs on board
the STEREO spacecraft. We establish that the disturbance is in fact
a fast magnetosonic wave as the upper coronal counterpart of the EIT
wave observed by STEREO EUVI and travels across magnetic field lines
with inhomogeneous speeds, passing through various coronal regions
such as quiet/active corona, coronal holes, and streamers. We derive
magnetic field strengths along the azimuthal trajectories of the fronts
at heliocentric distances 2.0, 2.5, and 3.0 Rs, using the varying
speeds and electron densities. The derived magnetic field strengths are
consistent with values determined with a potential field source surface
model and reported in previous works. The ranges of the magnetic field
strengths at these heliocentric distances are 0.44 ± 0.29, 0.23 ±
0.15, and 0.26 ± 0.14 G, respectively. The uncertainty in determining
magnetic field strengths is about 40 %. This work demonstrates that
observations of fast magnetosonic waves by white-light coronagraphs
can provide us with a unique way to diagnose magnetic field strength
of an inhomogeneous medium in a wide spatial range of the extended
solar corona.

---------------------------------------------------------
Title: Progress toward high resolution EUV spectroscopy
Authors: Korendyke, C.; Doschek, G. A.; Warren, H.; Young, P. R.;
Chua, D.; Hassler, D. M.; Landi, E.; Davila, J. M.; Klimchuck, J.;
Tun, S.; DeForest, C.; Mariska, J. T.; Solar C Spectroscopy Working
Group; LEMUR; EUVST Development Team
2013SPD....44..143K Altcode:
HIgh resolution EUV spectroscopy is a critical instrumental technique
to understand fundamental physical processes in the high temperature
solar atmosphere. Spectroscopic observations are used to measure
differential emission measure, line of sight and turbulent flows,
plasma densities and emission measures. Spatially resolved, spectra of
these emission lines with adequate cadence will provide the necessary
clues linking small scale structures with large scale, energetic
solar phenomena. The necessary observations to determine underlying
physical processes and to provide comprehensive temperature coverage
of the solar atmosphere above the chromosphere will be obtained by the
proposed EUVST instrument for Solar C. This instrument and its design
will be discussed in this paper. Progress on the VEry high Resolution
Imaging Spectrograph (VERIS) sounding rocket instrument presently under
development at the Naval Research Laboratory will also be discussed.

---------------------------------------------------------
Title: Modeling coronal loop oscillations in realistic magnetic and
density structures
Authors: Ofman, Leon; Wang, T.; Malanushenko, A.; Davila, J. M.
2013SPD....4410404O Altcode:
Recently, ubiquitous coronal loop oscillations were detected in
active region loops by SDO/AIA. Hinode/EIS observations indicate that
quasi-periodic flows are present at footpoints of loops in active
regions, and related propagating disturbances (PD's) were detected in
open and closed loop structures. Recent 3D MHD models in idealized
(bipolar) active regions (Ofman et al. 2012; Wang et al. 2013,
this meeting) have demonstrated that the flows can produce slow
magnetosonic waves in loops, as well as transverse oscillations. We
extend the idealized studies by considering more realistic magnetic
field structures modeled by including photospheric magnetic field
extrapolated to the corona as boundary and initial conditions for
the 3D MHD modeling. We use potential and nonlinear magnetic field
extrapolations combined with gravitationally stratified density and
introduce flows at the corona-transition region boundary in our 3D MHD
model. We apply coronal seismology to the resulting loop oscillations
and compare to oscillation events detected by SDO/AIA. We aim to
improve the accuracy of coronal seismology by modeling coronal loop
oscillations in realistic magnetic geometry and density structures.

---------------------------------------------------------
Title: Three-Dimensional MHD Modeling of Propagating Disturbances
in Fanlike AR Coronal Loops
Authors: Wang, Tongjiang; Ofman, L.; Davila, J. M.
2013SPD....44...36W Altcode:
Quasi-periodic propagating intensity disturbances (PDs) have been
observed in cool (about 1 MK) coronal loops in EUV images over a
decade. They are widely accepted to be slow magnetosonic waves
since their propagation velocity is close to the coronal sound
speed. However, recent spectroscopic observations from Hinode/EIS
revealed their association with persistent coronal upflows, making this
interpretation debatable. Motivated by the scenario that the observed
persistent upflows could be cumulative result of numerous individual
flow pulses generated by sporadic heating events (nanoflares) at the
loop base, we constructed a broadband velocity driver with repetative
tiny pulses, whose energy frequency distribution follows the flare
power-law scaling distribution. We then performed 3D MHD modeling
of an idealized bipolar active region by applying this broadband
velocity driver at the footpoints of coronal loops which appear open
in the computational domain. Our model successfully reproduced the
propagating disturbances with similar features as the observed. We
find, based on our simulations, that upflow pulses unavoidably excites
a slow magnetosonic wave fronts propagating along the loop with the
phase speed which is much larger than the local flow speed as the flow
velocity decreases with height. Our modeling results support that the
observed PDs are mainly the signature of waves above the footpoints of
the loops, and suggest that the observed PDs and associated persistent
upflows may be driven by the same mechanism such as impulsive heating
at the loop base.

---------------------------------------------------------
Title: Slow mode waves and quasi-periodic upflows in the
multi-temperature solar corona as seen by the SDO
Authors: Uritsky, Vadim; Davila, J. M.; Viall, N.; Ofman, L.
2013SPD....4410405U Altcode:
We report results the analysis of coronal fan loops in a non-flaring
solar active region exhibiting temperature-dependent propagating optical
disturbances. A 6-hour set of high resolution coronal observations
provided by the Atmospheric Imaging Assembly (AIA) on board the Solar
Dynamics Observatory (SDO) has been used for characterizing apparent
propagating patterns at multiple coronal temperatures (131A, 171A,
193A and 211A). A new data analysis methodology has been developed
enabling an identification of subvisual motions with low signal-to-noise
ratios not previously examined in this context. The technique involves
spatiotemporal tracking of fan loop filaments containing propagating
disturbances, construction of position - time plots for different
temperature channels, obtaining the waveforms of the propagating optical
features, and evaluation of Fourier spectral power of the waveforms
as a function of phase speed and frequency. Using this methodology,
we identified the parameters of propagating optical disturbances in
different magnetic geometries, and classified these events as waves
and/or plasma jets. We explored coronal conditions favoring wave-like
and jet-like traveling plasma density enhancements in fan loops and
the mechanisms of their generation, damping and interaction. The
results obtained are compared with the behavior of a resistive MHD
model exhibiting both types of propagating disturbances.

---------------------------------------------------------
Title: Structure of the Coronal Streamers During Solar Minimum
and Maximum
Authors: Kramar, Maxim; Davila, J.; Mikic, Z.
2013SPD....44...11K Altcode:
We analyze the meridional cross-section of the 3D coronal electron
density in the range from 1.5 to 4 R_⊙ obtained by the tomography
method during minimum and beginning of maximum of solar activity
corresponding to February 2008 and July 2011, respectively. The
importance of this coronal region is that it contains the transition
from closed to open magnetic coronal structures. At the moment,
only STEREO/COR1 provides observation that provides information
on the coronal structure in this region. Therefore, analysis of 3D
coronal density structure is critical for deriving the position where
transition from closed to open magnetic coronal structures occurs. The
3D coronal density in the region of interest has been obtained
by applying tomographic techniques to white light coronagraph data
obtained by STEREO/COR1 instrument. It is shown that enhanced density
structures associated with coronal streamers and pseudostreamers have
a tendency to become radially directed at heliocentric distances of
about 3 and 2 $R_\odot$ during minimum and maximum of solar activity,
respectively. Potential Field models (PFSS) with several different
values of the Source Surface position have been analyzed for consistency
with the obtained 3D coronal density structure.

---------------------------------------------------------
Title: Global Coronal Seismology in the Extended Solar Corona through
Fast Magnetosonic Waves Observed by STEREO SECCHI COR1
Authors: Kwon, Ryun Young; Zhang, Jie; Kramar, Maxim; Wang, Tongjiang;
Ofman, Leon; Davila, Joseph M.
2013shin.confE..75K Altcode:
We present global coronal seismology, for the first time, that allows us
to determine inhomogeneous magnetic field strengths in a wide range of
the extended solar corona. We use observations of a fast magnetosonic
wave associated with a coronal mass ejection observed on 2011 August
4 by the COR1 inner coronagraphs on board the STEREO spacecraft. In
order to estimate inhomogeneous magnetic field strength, we choose the
azimuthal trajectories of the wave front at heliocentric distances
2.0, 2.5, and 3.0 solar radii and determine the speeds of the wave
front and electron densities using polarized brightness images along
the trajectories. The magnetic field strengths are derived with an
uncertainty less than 40 % and consistent with values determined with a
potential field source surface model and reported in previous works. The
characteristics of the coronal medium revealed with our global coronal
seismology are that: (1) density, magnetic field strength, plasma beta
are lower in the coronal hole than in the streamers, (2) magnetic field
strength decreases slowly with height but electron density decreases
rapidly so that local fast magnetosonic speed increases while plasma
beta falls off with height, and (3) the variations of local fast
magnetosonic speed and plasma beta are in accordance with the electron
density rather than magnetic field strength. These characteristics of
the coronal medium imply that Moreton and EIT waves are downward shock
fronts of fast magnetosonic waves refracted from the upper solar corona,
rather than freely propagating fast magnetosonic waves in a certain
solar atmospheric layer. In addition, the azimuthal components of
CMEs may play an important role in various manifestations of shocks,
such as type II radio bursts and solar energetic particle events.

---------------------------------------------------------
Title: Coronal Magnetic Field Reconstruction based on HAO/CoMP
observations.
Authors: Kramar, Maxim; Lin, H.; Tomczyk, S.; Davila, J.
2013shin.confE..89K Altcode:
The magnetic field is the dominant force source in the solar coronal
plasma, the one that shapes its structure. Synoptic observations that
provide a direct information about the magnetic field have been recently
became available by High Altitude Observatory (HAO) Coronal Multichannel
Polarimeter (CoMP). The instrument provides linear polarization maps of
the Fe XIII 10747 A 'forbidden' line. The observed linear polarization
depends on magnetic field orientation through Hanle effect. These
observation, supplied with additional photospheric magnetic field
measurements and UV observations, are used for 3D reconstruction of
the coronal magnetic field by applying the vector tomography technique.

---------------------------------------------------------
Title: Stochastic Coupling of Solar Photosphere and Corona
Authors: Uritsky, Vadim M.; Davila, Joseph M.; Ofman, Leon; Coyner,
Aaron J.
2013ApJ...769...62U Altcode: 2012arXiv1212.5610U
The observed solar activity is believed to be driven by the dissipation
of nonpotential magnetic energy injected into the corona by dynamic
processes in the photosphere. The enormous range of scales involved
in the interaction makes it difficult to track down the photospheric
origin of each coronal dissipation event, especially in the presence of
complex magnetic topologies. In this paper, we propose an ensemble-based
approach for testing the photosphere-corona coupling in a quiet solar
region as represented by intermittent activity in Solar and Heliospheric
Observatory Michelson Doppler Imager and Solar TErrestrial RElations
Observatory Extreme Ultraviolet Imager image sets. For properly adjusted
detection thresholds corresponding to the same degree of intermittency
in the photosphere and corona, the dynamics of the two solar regions is
described by the same occurrence probability distributions of energy
release events but significantly different geometric properties. We
derive a set of scaling relations reconciling the two groups of
results and enabling statistical description of coronal dynamics based
on photospheric observations. Our analysis suggests that multiscale
intermittent dissipation in the corona at spatial scales &gt;3 Mm is
controlled by turbulent photospheric convection. Complex topology of
the photospheric network makes this coupling essentially nonlocal and
non-deterministic. Our results are in an agreement with the Parker's
coupling scenario in which random photospheric shuffling generates
marginally stable magnetic discontinuities at the coronal level,
but they are also consistent with an impulsive wave heating involving
multiscale Alfvénic wave packets and/or magnetohydrodynamic turbulent
cascade. A back-reaction on the photosphere due to coronal magnetic
reconfiguration can be a contributing factor.

---------------------------------------------------------
Title: The First Ground Level Enhancement Event of Solar Cycle 24:
Direct Observation of Shock Formation and Particle Release Heights
Authors: Gopalswamy, N.; Xie, H.; Akiyama, S.; Yashiro, S.; Usoskin,
I. G.; Davila, J. M.
2013ApJ...765L..30G Altcode: 2013arXiv1302.1474G
We report on the 2012 May 17 ground level enhancement (GLE) event,
which is the first of its kind in solar cycle 24. This is the first GLE
event to be fully observed close to the surface by the Solar Terrestrial
Relations Observatory (STEREO) mission. We determine the coronal mass
ejection (CME) height at the start of the associated metric type
II radio burst (i.e., shock formation height) as 1.38 Rs (from the
Sun center). The CME height at the time of GLE particle release was
directly measured from a STEREO image as 2.32 Rs, which agrees well
with the estimation from CME kinematics. These heights are consistent
with those obtained for cycle-23 GLEs using back-extrapolation. By
contrasting the 2012 May 17 GLE with six other non-GLE eruptions from
well-connected regions with similar or larger flare sizes and CME
speeds, we find that the latitudinal distance from the ecliptic is
rather large for the non-GLE events due to a combination of non-radial
CME motion and unfavorable solar B0 angle, making the connectivity
to Earth poorer. We also find that the coronal environment may play
a role in deciding the shock strength.

---------------------------------------------------------
Title: Vertical kink oscillations of coronal loops triggered by
recurrent jets
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.
2013enss.confE..99W Altcode:
Transverse coronal loop oscillations were first observed by TRACE
in EUV images, and have been interpreted as global standing kink
modes. These loop oscillations are thought to be excited by a blast
wave in the form of a shock or a fast-mode wave produced by a flare
or CME. In this presentation, we report simultaneous imaging and
spectroscopic observations with SDO/AIA and Hinode/EIS of a vertical
loop oscillations triggered by recurrent jets at the footpoints. These
oscillations start with a fast disturbance traveling along the loop
with the propagating speed more than 500 km/s, much faster than the
apparent EUV jets. The vertical loop oscillations are associated with
quasi-periodic outwardly propagating features with the speeds 30-300
km/s, suggestive of loop expansions. In addition, we perform 3D MHD
modeling of a typical such event to understand the excitation of kink
oscillations by impulsive flows.

---------------------------------------------------------
Title: STEREO Observations of Fast Magnetosonic Waves in the Extended
Solar Corona Associated with EIT/EUV Waves
Authors: Kwon, Ryun-Young; Ofman, Leon; Olmedo, Oscar; Kramar, Maxim;
Davila, Joseph M.; Thompson, Barbara J.; Cho, Kyung-Suk
2013ApJ...766...55K Altcode:
We report white-light observations of a fast magnetosonic wave
associated with a coronal mass ejection observed by STEREO/SECCHI/COR1
inner coronagraphs on 2011 August 4. The wave front is observed in the
form of density compression passing through various coronal regions such
as quiet/active corona, coronal holes, and streamers. Together with
measured electron densities determined with STEREO COR1 and Extreme
UltraViolet Imager (EUVI) data, we use our kinematic measurements of
the wave front to calculate coronal magnetic fields and find that the
measured speeds are consistent with characteristic fast magnetosonic
speeds in the corona. In addition, the wave front turns out to be
the upper coronal counterpart of the EIT wave observed by STEREO
EUVI traveling against the solar coronal disk; moreover, stationary
fronts of the EIT wave are found to be located at the footpoints of
deflected streamers and boundaries of coronal holes, after the wave
front in the upper solar corona passes through open magnetic field
lines in the streamers. Our findings suggest that the observed EIT
wave should be in fact a fast magnetosonic shock/wave traveling in
the inhomogeneous solar corona, as part of the fast magnetosonic wave
propagating in the extended solar corona.

---------------------------------------------------------
Title: Reconstruction of the 3D Coronal Magnetic Field by Vector
Tomography with Infrared Spectropolarimetric Observations from CoMP
Authors: Kramar, M.; Lin, H.; Tomczyk, S.; Davila, J. M.; Inhester, B.
2012AGUFMSH42A..06K Altcode:
Magnetic fields determine the static and dynamic properties of the solar
corona. A significant progress has been achieved in direct measurement
of the magnetically sensitive coronal emission with deployment of
the HAO Coronal Multichannel Polarimeter (CoMP). The instrument
provides polarization measurements of Fe XIII 10747 A forbidden line
emission. The observed polarization depends on magnetic field through
the Hanle and Zeeman effects. However, because the coronal measurements
are integrated over line-of-site (LOS), it is impossible to derive the
configuration of the coronal magnetic field from a single observation
(from a single viewing direction). The vector tomography techniques
based on the infrared polarimetric measurements from several viewing
directions has been developed in order to resolve the 3D coronal
magnetic field structure over LOS. Because of the non-linear character
of the Hanle effect, the reconstruction result based on such data
is not straightforward and depends on the particular coronal field
configuration. For several possible cases of coronal magnetic field
configuration, it has been found that even just Stokes-Q and -U data
(supplied with 3D coronal density and temperature) can be used in the
vector tomography to provide a realistic 3D coronal magnetic field. The
3D coronal density and temperature needed as an supplemental input are
reconstructed by the scalar field tomography method using ultraviolet
observations from EUVI/STEREO. We will present the reconstructed 3D
coronal density, temperature and magnetic field in the range of ∼
1.3 R⊙ obtained by the scalar and vector tomography.

---------------------------------------------------------
Title: A Space Weather Mission to the Earth's 5th Lagrangian Point
(L5)
Authors: Howard, R. A.; Vourlidas, A.; Ko, Y.; Biesecker, D. A.;
Krucker, S.; Murphy, N.; Bogdan, T. J.; St Cyr, O. C.; Davila, J. M.;
Doschek, G. A.; Gopalswamy, N.; Korendyke, C. M.; Laming, J. M.;
Liewer, P. C.; Lin, R. P.; Plunkett, S. P.; Socker, D. G.; Tomczyk,
S.; Webb, D. F.
2012AGUFMSA13D..07H Altcode:
The highly successful STEREO mission, launched by NASA in 2006,
consisted of two spacecraft in heliocentric orbit, one leading and
one trailing the Earth and each separating from Earth at the rate
of about 22.5 degrees per year. Thus the two spacecraft have been
probing different probe/Sun/Earth angles. The utility of having remote
sensing and in-situ instrumentation away from the Sun-Earth line was
well demonstrated by STEREO. Here we propose the concept of a mission
at the 5th Lagrangian "point" in the Earth/Sun system, located behind
Earth about 60 degrees to the East of the Sun-Earth line. Such a mission
would enable many aspects affecting space weather to be well determined
and thus improving the prediction of the conditions of the solar wind
as it impinges on geospace. For example, Coronal Mass Ejections can
tracked for a significant distance toward Earth, new active regions
can be observed before they become visible to the Earth observer, the
solar wind can be measured before it rotates to Earth. The advantages
of such a mission will be discussed in this presentation.

---------------------------------------------------------
Title: Hot Precursor Ejecta and Other Peculiarities of the 2012 May
17 Ground Level Enhancement Event
Authors: Gopalswamy, N.; Xie, H.; Nitta, N. V.; Usoskin, I.; Davila,
J. M.
2012AGUFMSH21A2180G Altcode:
We report on the first Ground Level Enhancement (GLE) event of Solar
Cycle 24, which occurred on May 17, 2012 from a well-connected region
(NOAA AR 11476, N11W76) on the Sun. There has been a real dearth
of GLE events during cycle 24: even though the Sun has reached its
solar maximum phase, it has produced only this one GLE event. Over the
first 4.5 years of solar cycle 23, there were 5 GLE events, which is
roughly a third of all the events of that cycle. The recent GLE event
was associated with a moderate flare with an X-ray size of only M5.1,
well below the median flare size (X3.8) of cycle 23 GLE events. On
the other hand, the associated CME was very fast (~2000 km/s),
typical of GLE events. During cycle 23, the CME speeds in GLE events
ranged from 1203 km/s to 3675 km/s with an average value of 2083 km/s
(Gopalswamy et al., 2012). The speed of the cycle 24 GLE was measured
accurately because it was a limb event in the SOHO coronagraphic field
of view. The CME was also observed by the STEREO coronagraphs, which
helped derive the initial acceleration as 1.5 km/s/s, which is also
typical of GLE-producing CMEs. We were also able to directly determine
the heliocentric distance of the CME (2.3 solar radii (Rs)) at the
time of the release of GLE particles because there was a STEREO/COR1
image precisely at the time of the particle release. This result
is consistent with what was obtained for the cycle 23 GLE events,
including the distance of the CME at the time of metric type II burst
onset (1.3 Rs), indicating shock formation very close to the Sun
( ~0.3 Rs above the solar surface). We infer that the shock had to
travel an additional 1 Rs before the GLE particles were released. The
CME had a precursor in the form of a hot ejecta some tens of minutes
before the main eruption. The preceding ejecta is termed hot because
it was observed only in the 94 A images obtained by the Solar Dynamics
Observatory (SDO). The 94 A images correspond to coronal a temperature
of ~6MK. The lower temperature images such as at 193 A did not show
the ejecta. The hot ejecta was accelerating and attained a speed
of ~70 km/s before it was blasted by the big GLE-producing CMEs. We
suggest that the hot material of the precursor ejecta might have been
further accelerated by the CME-driven shock resulting in the GLE
event. Reference Gopalswamy, N.,Xie, H., Yashiro, S., Akiyama, S.,
Mäkelä, P., Usoskin, I. G., Properties of Ground Level Enhancement
Events and the Associated Solar Eruptions During Solar Cycle 23,
Space Science reviews, DOI: 10.1007/s11214-012-9890-4

---------------------------------------------------------
Title: Exploring Small Spatial Scales in the Transition Region
and Solar Corona with the Very High Angular Resolution Imaging
Spectrometer (VERIS)
Authors: Chua, D. H.; Korendyke, C. M.; Vourlidas, A.; Brown, C. M.;
Tun-Beltran, S.; Klimchuk, J. A.; Landi, E.; Seely, J.; Davila, J. M.;
Hagood, R.; Roberts, D.; Shepler, E.; Feldman, R.; Moser, J.; Shea, J.
2012AGUFMSH33A2217C Altcode:
Theoretical and experimental investigations of the transition region
and coronal loops point to the importance of processes occurring on
small spatial scales in governing the strong dynamics and impulsive
energy release in these regions. As a consequence, high spatial,
temporal, and temperature resolution over a broad temperature range,
and accuracy in velocity and density determinations are all critical
observational parameters. Current instruments lack one or more of these
properties. These observational deficiencies have created a wide array
of opposing descriptions of coronal loop heating and questions such
as whether or not the plasma within coronal loops is multi-thermal or
isothermal. High spectral and spatial resolution spectroscopic data
are absolutely required to resolve these controversies and to advance
our understanding of the dynamics within the solar atmosphere. We
will achieve this with the Very High Angular Resolution Imaging
Spectrometer (VERIS) sounding rocket payload. VERIS consists of an
off-axis paraboloid telescope feeding a very high angular resolution,
extreme ultraviolet (EUV) imaging spectrometer that will provide
the first ever, simultaneous sub-arcsecond (0.16 arcsecond/pixel)
spectra in bright lines needed to study plasma structures in the
transition region, quiet corona, and active region core. It will do
so with a spectral resolution of &gt;5000 to allow Doppler velocity
determinations to better than 3 km/s. VERIS uses a novel two-element,
normal incidence optical design with highly reflective, broad wavelength
coverage EUV coatings to access a spectral range with broad temperature
coverage (0.03-15 MK) and density-sensitive line ratios. Combined with
Hinode Solar Optical Telescope (SOT) and ground based observatories,
VERIS will deliver simultaneous observations of the entire solar
atmosphere from the photosphere to the multi-million degree corona
at sub-arcsecond resolution for the first time ever, allowing us to
understand the missing link between chromospheric structures and the
corona. VERIS will be launched from White Sands Missile Range in early
2013. This paper presents a progress report on the VERIS payload and
a summary of observations planned to further our understanding of
the fine-scale structure of individual coronal loops and the heating
mechanisms operating within them.

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Title: Three-dimensional Structure and Evolution of
Extreme-ultraviolet Bright Points Observed by STEREO/SECCHI/EUVI
Authors: Kwon, Ryun-Young; Chae, Jongchul; Davila, Joseph M.; Zhang,
Jie; Moon, Yong-Jae; Poomvises, Watanachak; Jones, Shaela I.
2012ApJ...757..167K Altcode:
We unveil the three-dimensional structure of quiet-Sun EUV bright
points and their temporal evolution by applying a triangulation method
to time series of images taken by SECCHI/EUVI on board the STEREO twin
spacecraft. For this study we examine the heights and lengths as the
components of the three-dimensional structure of EUV bright points
and their temporal evolutions. Among them we present three bright
points which show three distinct changes in the height and length:
decreasing, increasing, and steady. We show that the three distinct
changes are consistent with the motions (converging, diverging,
and shearing, respectively) of their photospheric magnetic flux
concentrations. Both growth and shrinkage of the magnetic fluxes
occur during their lifetimes and they are dominant in the initial
and later phases, respectively. They are all multi-temperature
loop systems which have hot loops (~106.2 K) overlying
cooler ones (~106.0 K) with cool legs (~104.9
K) during their whole evolutionary histories. Our results imply that
the multi-thermal loop system is a general character of EUV bright
points. We conclude that EUV bright points are flaring loops formed by
magnetic reconnection and their geometry may represent the reconnected
magnetic field lines rather than the separator field lines.

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Title: LEMUR: Large European module for solar Ultraviolet
Research. European contribution to JAXA's Solar-C mission
Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric;
Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len;
Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George
A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green,
Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem,
Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet,
Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto,
Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu,
Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele;
Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas;
Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann,
Thomas; Winter, Berend; Young, Peter
2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T
The solar outer atmosphere is an extremely dynamic environment
characterized by the continuous interplay between the plasma and the
magnetic field that generates and permeates it. Such interactions play a
fundamental role in hugely diverse astrophysical systems, but occur at
scales that cannot be studied outside the solar system. Understanding
this complex system requires concerted, simultaneous solar observations
from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at
high spatial resolution (between 0.1” and 0.3”), at high temporal
resolution (on the order of 10 s, i.e., the time scale of chromospheric
dynamics), with a wide temperature coverage (0.01 MK to 20 MK,
from the chromosphere to the flaring corona), and the capability of
measuring magnetic fields through spectropolarimetry at visible and
near-infrared wavelengths. Simultaneous spectroscopic measurements
sampling the entire temperature range are particularly important. These
requirements are fulfilled by the Japanese Solar-C mission (Plan B),
composed of a spacecraft in a geosynchronous orbit with a payload
providing a significant improvement of imaging and spectropolarimetric
capabilities in the UV, visible, and near-infrared with respect to
what is available today and foreseen in the near future. The Large
European Module for solar Ultraviolet Research (LEMUR), described
in this paper, is a large VUV telescope feeding a scientific payload
of high-resolution imaging spectrographs and cameras. LEMUR consists
of two major components: a VUV solar telescope with a 30 cm diameter
mirror and a focal length of 3.6 m, and a focal-plane package composed
of VUV spectrometers covering six carefully chosen wavelength ranges
between 170 Å and 1270 Å. The LEMUR slit covers 280” on the Sun with
0.14” per pixel sampling. In addition, LEMUR is capable of measuring
mass flows velocities (line shifts) down to 2 km s - 1 or
better. LEMUR has been proposed to ESA as the European contribution
to the Solar C mission.

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Title: The Relationship Between the Expansion Speed and Radial Speed
of CMEs Confirmed Using Quadrature Observations of the 2011 February
15 CME
Authors: Gopalswamy, N.; Makela, P.; Yashiro, S.; Davila, J. M.
2012SunGe...7....7G Altcode: 2012arXiv1205.0744G
It is difficult to measure the true speed of Earth-directed CMEs
from a coronagraph along the Sun-Earth line because of the occulting
disk. However, the expansion speed (the speed with which the CME appears
to spread in the sky plane) can be measured by such coronagraph. In
order to convert the expansion speed to radial speed (which is
important for space weather applications) one can use empirical
relationship between the two that assumes an average width for all
CMEs. If we have the width information from quadrature observations,
we can confirm the relationship between expansion and radial speeds
derived by Gopalswamy et al. (2009a). The STEREO spacecraft were in
qudrature with SOHO (STEREO-A ahead of Earth by 87oand
STEREO-B 94obehind Earth) on 2011 February 15, when a fast
Earth-directed CME occurred. The CME was observed as a halo by the
Large-Angle and Spectrometric Coronagraph (LASCO) on board SOHO. The
sky-plane speed was measured by SOHO/LASCO as the expansion speed,
while the radial speed was measured by STEREO-A and STEREO-B. In
addition, STEREO-A and STEREO-B images measured the width of the
CME, which is unknown from Earth view. From the SOHO and STEREO
measurements, we confirm the relationship between the expansion
speed (Vexp) and radial speed (Vrad) derived
previously from geometrical considerations (Gopalswamy et al. 2009a):
Vrad=1/2 (1 + cot w)Vexp, where w is the half
width of the CME. STEREO-B images of the CME, we found that CME
had a full width of 7 6o, so w=3 8o. This
gives the relation as Vrad=1.1 4 Vexp. From
LASCO observations, we measured Vexp=897 km/s, so we get
the radial speed as 10 2 3 km/s. Direct measurement of radial speed
yields 945 km/s (STEREO-A) and 105 8 km/s (STEREO-B). These numbers
are different only by 7.6 % and 3.4 % (for STEREO-A and STEREO-B,
respectively) from the computed value.

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Title: Slow Magnetosonic Waves and Fast Flows in Active Region Loops
Authors: Ofman, L.; Wang, T. J.; Davila, J. M.
2012ApJ...754..111O Altcode: 2012arXiv1205.5732O
Recent extreme ultraviolet spectroscopic observations indicate
that slow magnetosonic waves are present in active region (AR)
loops. Some of the spectral data were also interpreted as evidence
of fast (~100-300 km s-1) quasi-periodic flows. We have
performed three-dimensional magnetohydrodynamic (3D MHD) modeling of
a bipolar AR that contains impulsively generated waves and flows in
coronal loops. The model AR is initiated with a dipole magnetic field
and gravitationally stratified density, with an upflow-driven steadily
or periodically in localized regions at the footpoints of magnetic
loops. The resulting flows along the magnetic field lines of the AR
produce higher density loops compared to the surrounding plasma by
injection of material into the flux tubes and the establishment of
siphon flow. We find that the impulsive onset of flows with subsonic
speeds result in the excitation of damped slow magnetosonic waves that
propagate along the loops and coupled nonlinearly driven fast-mode
waves. The phase speed of the slow magnetosonic waves is close to
the coronal sound speed. When the amplitude of the driving pulses is
increased we find that slow shock-like wave trains are produced. When
the upflows are driven periodically, undamped oscillations are produced
with periods determined by the periodicity of the upflows. Based on
the results of the 3D MHD model we suggest that the observed slow
magnetosonic waves and persistent upflows may be produced by the same
impulsive events at the bases of ARs.

---------------------------------------------------------
Title: Global Cooperation in the Capacity Building Activities on
Sun-Earth Connection Studies
Authors: Gopalswamy, Nat; Davila, Joseph; Luebken, Franz-Josef;
Shepherd, Marianna; Tsuda, Toshitaka
2012cosp...39..650G Altcode: 2012cosp.meet..650G
The importance of global cooperation in Sun-Earth connection studies
can be readily seen in the formation of a number of international
collaborative programs such as the Climate and Weather of the
Sun Earth System (CAWSES) by SCOSTEP* and the International Space
Weather Initiative (ISWI). ISWI is the continuation of the successful
International Heliophysical Year (IHY) program. These programs have
brought scientists together to tackle issues of solar-terrestrial
phenomena. An important element of these organizations is capacity
building activities, which include deployment of low-cost ground
based instruments for Sun-Earth connection studies and training young
people (scientists and graduate students) from developing countries
to operate these instruments and become members of the international
solar-terrestrial scientific community. The training also helps young
people to make use of data from the vast array of space and ground based
instruments currently available for Sun-Earth connection studies. This
paper presents a summary of CAWSES and ISWI activities that promote
space Sun-Earth connection studies via complementary approaches in
international scientific collaborations, capacity building, and public
outreach. *Scientific Committee on Solar Terrestrial Physics (SCOSTEP)
is an Interdisciplinary Body of the International Council for Science
with representations from COSPAR, IAU, IUGG/IAGA, IUPAP, IAMAS, SCAR,
and URSI (http://www.yorku.ca/scostep)

---------------------------------------------------------
Title: A Global View of the Energetic Solar Eruptions during 2012
January 19-27
Authors: Gopalswamy, Nat; Davila, Joseph; Kaiser, Michael; Macdowall,
Robert; Cyr, Chris; Xie, Hong; Makela, Pertti; Yashiro, Seiji;
Poomvises, Watanachak
2012cosp...39..652G Altcode: 2012cosp.meet..652G
The rise phase of solar cycle was generally unremarkable and subdued in
terms of large solar eruptive events that had significant heliospheric
consequences. Towards the end of the rise phase, a series of three
coronal mass ejections (CMEs) originated from NOAA active region
11402 that were accompanied by M or X-class flares, significant solar
energetic particle events (including the largest event as of this
writing), interplanetary type II radio bursts, and shocks. While
the particle radiation was very intense in two events, the plasma
impact on the magnetosphere was moderate. This paper provides an
overview of the eruptive events, focusing on the kinematic evolution
of the CMEs in relation to the interplanetary type II radio bursts
and shocks. In particular we compare the drift rate variation of
the interplanetary type II bursts with the speed variation of the
CMEs obtained from heliospheric imaging. We make use of data from the
Solar and Heliospheric Observatory (SOHO), Solar Terrestrial Relations
Observatory (STEREO), Solar Dynamics Observatory (SDO), Wind, GOES,
and ground based observatories for this investigation.

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Title: 3D Coronal Magnetic Field reconstructed by Vector Tomography
Method using CoMP data
Authors: Kramar, Maxim; Lin, H.; Tomczyk, S.; Inhester, B.; Davila, J.
2012shin.confE.141K Altcode:
Magnetic fields in the solar corona dominates the gas pressure
and therefore determine the static and dynamic properties of the
corona. Direct measurement of the coronal magnetic field is one of
the most challenging problems in observational solar astronomy and
recently a significant progress has been achieved here with deployment
of the HAO Coronal Multichannel Polarimeter (CoMP). The instrument
provides polarization measurements of Fe XIII 10747 A forbidden line
emission. The observed polarization depends on magnetic field through
the Hanle and Zeeman effects. However, because the coronal measurements
are integrated over line-of-site (LOS), it is impossible to derive the
configuration of the coronal magnetic field from a single observation
(from a single viewing direction). The vector tomography techniques
based on measurements from several viewing directions has the potential
to resolve the 3D coronal magnetic field structure over LOS. Because
of the non-linear character of the Hanle effect, the reconstruction
result based on such data is not straightforward and depends on the
particular coronal field configuration. Therefore, previously we also
studied what is the sensitivity of the vector tomographic inversion to
various coronal magnetic field models. For several possible cases of
coronal magnetic field configuration, it has been found that even just
Stokes-Q and -U data (supplied with 3D coronal density and temperature)
can be used in vector tomography to provide a realistic 3D coronal
magnetic field configuration. The 3D coronal density and temperature
needed as an supplemental input are reconstructed by the scalar field
tomography method using ultraviolet observations from EUVI/STEREO. We
will present the reconstructed 3D coronal magnetic field in the range
of ∼1.3 R_⊙ obtained by the vector tomographic technique that has
been applied to the CoMP data.

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Title: Growing Transverse Oscillations of a Multistranded Loop
Observed by SDO/AIA
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.; Su, Yang
2012ApJ...751L..27W Altcode: 2012arXiv1204.1376W
The first evidence of transverse oscillations of a multistranded
loop with growing amplitudes and internal coupling observed by the
Atmospheric Imaging Assembly on board the Solar Dynamics Observatory
is presented. The loop oscillation event occurred on 2011 March 8,
triggered by a coronal mass ejection (CME). The multiwavelength analysis
reveals the presence of multithermal strands in the oscillating loop,
whose dynamic behaviors are temperature-dependent, showing differences
in their oscillation amplitudes, phases, and emission evolution. The
physical parameters of growing oscillations of two strands in 171 Å
are measured and the three-dimensional loop geometry is determined
using STEREO-A/EUVI data. These strands have very similar frequencies,
and between two 193 Å strands a quarter-period phase delay sets
up. These features suggest the coupling between kink oscillations of
neighboring strands and the interpretation by the collective kink mode
as predicted by some models. However, the temperature dependence of
the multistranded loop oscillations was not studied previously and
needs further investigation. The transverse loop oscillations are
associated with intensity and loop width variations. We suggest that
the amplitude-growing kink oscillations may be a result of continuous
non-periodic driving by magnetic deformation of the CME, which deposits
energy into the loop system at a rate faster than its loss.

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Title: Slow-Mode Oscillations of Hot Loops Excited at Flaring
Footpoints
Authors: Wang, T.; Liu, W.; Ofman, L.; Davila, J.
2012ASPC..456..127W Altcode: 2017arXiv170605427W
The analysis of a hot loop oscillation event using SOHO/SUMER,
GOES SXI, and RHESSI observations is presented. Damped Doppler shift
oscillations were detected in the Fe xix line by SUMER, and interpreted
as a fundamental standing slow mode. The evolution of soft X-ray
emission from GOES/SXI and hard X-ray sources from RHESSI suggests
that the oscillations of a large loop are triggered by a small flare,
which may be produced by interaction (local reconnection) of this
large loop with a small loop at its footpoint. This study provides
clear evidence supporting our early conjecture that the slow-mode
standing waves in hot coronal loops are excited by impulsive heating
(small or microflares) at the loop's footpoint.

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Title: Slitless Solar Spectroscopy
Authors: Davila, Joseph M.
2012AAS...22020617D Altcode:
Spectrographs provide a unique window into plasma parameters in the
solar atmosphere. In the corona and elsewhere spectral line profiles
have been used to infer microturbulence velocities, Doppler shifts
have been used to measure flows, and line ratios have been used to
measure temperatures. In fact spectrographs provide the most accurate
measurements of plasma parameters such as density, temperature, and
flow speed. However, traditionally spectrographic instruments have
suffered from the inability to cover large spatial regions of the Sun
quickly. To cover an active region sized spatial region, the slit must
be rastered over the area of interest with an exposure taken at each
pointing location. The raster process can easily take several minutes
or longer to cover an active region sized area on the Sun. Because of
this long cycle time, the spectra of dynamic events like flares, CME
initiations, or transient brightening are obtained only rarely. And
even if spectra are obtained they are either taken over an extremely
small spatial region, or the spectra are not co-temporal across
the raster. Either of these complicates the interpretation of the
spectral raster results. Imagers are able to provide high time and
spatial resolution images of the full Sun but with limited spectral
resolution. The telescopes onboard the Solar Dynamics Observatory (SDO)
normally take a full disk solar image every 10 seconds with roughly
1 arcsec spatial resolution. However the spectral resolution of the
multilayer imagers on SDO is of order 100 times less than a typical
spectrograph. We suggest an alternate reconstruction approach based on
tomographic methods with regularization. Results show that the typical
Doppler shift and line width error introduced by the reconstruction
method is of order a few km/s at 300 A.

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Title: Propagating Intensity Disturbances in Fan-like Coronal Loops:
Flows or Waves?
Authors: Wang, T.; Ofman, L.; Davila, J. M.
2012ASPC..455..227W Altcode: 2011arXiv1101.6017W
Quasi-periodic intensity disturbances propagating upward along the
coronal structure have been extensively studied using EUV imaging
observations from SOHO/EIT and TRACE. They were interpreted as either
slow mode magnetoacoustic waves or intermittent upflows. In this study
we aim at demonstrating that time series of spectroscopic observations
are critical to solve this puzzle. Propagating intensity and Doppler
shift disturbances in fanlike coronal loops are analyzed in multiple
wavelengths using sit-and-stare observations from Hinode/EIS. We find
that the disturbances did not cause the blue-wing asymmetry of spectral
profiles in the warm (∼1.5 MK) coronal lines. The estimated small
line-of-sight velocities also did not support the intermittent upflow
interpretation. In the hot (∼2 MK) coronal lines the disturbances
did cause the blue-wing asymmetry, but the double fits revealed that
a high-velocity minor component is steady and persistent, while the
propagating intensity and Doppler shift disturbances are mainly due
to variations of the core component, therefore, supporting the slow
wave interpretation. However, the cause for blueward line asymmetries
remains unclear.

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Title: High-resolution Solar Imaging with a Photon Sieve
Authors: Davila, Joseph M.
2012AAS...22020102D Altcode:
Dissipation in the solar corona is expected to occur in extremely thin
current sheets of order 1-100 km. Emission from these current
sheets should be visible in coronal EUV emission lines. However,
this spatial scale is far below the resolution of existing imaging
instruments. Conventional optics cannot be easily manufactured with
sufficient surface figure accuracy to obtain the required &lt; 0.1
arcsec resolution. A photon sieve, a diffractive imaging element
similar to a Fresnel zone plate, can be manufactured to provide a
few 0.001 arcsec resolution, with much more relaxed tolerances than
conventional imaging technology. A simple design for a sounding rocket
payload is presented that obtains 80 mas (0.080 arcsec) imaging with a
100 mm diameter photon sieve to image Fe XIV 334 and Fe XVI 335. These
images will not only show the structure of the corona at a resolution
never before obtained, they will also allow a study of the temperature
structure in the dissipation region.

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Title: SDO / AIA Observations of Slow Mode Waves in Coronal Fan Loops
Authors: Uritsky, Vadim; Davila, J. M.; Viall, N. M.
2012AAS...22032205U Altcode:
We investigate slow mode waves in fan coronal loops observed by
the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory spacecraft ( 12 sec cadence, 0.6 arcsec pixels). The warm
fan structure studied here was located at the periphery of quiescent
active region NOAA AR 11082. A specialized software package has been
developed for extracting subvisual modulations of SDO AIA intensity
propagating along dynamic loop segments changing their shape and
position during the observation. The processing steps include manual
tracking of the segment location in time sequences of co-aligned
multispectral AIA images, extracting wave-carrying filamentary
segments from the surrounding background, constructing position -
time diagrams representing temporal evolution of optical brightness
along the filaments, and analysis of the obtained wave signatures. The
results reveal a persistent wave activity in many fan loop segments
characterized by a well-defined frequency and phase speed, with the best
signal-to-noise ratio in 171Å and 193Å channels. For some filamentary
segments, the wave parameters remained almost constant over the entire
observing interval ( 6 hours). The wave parameters varied across
the studied structures. The fastest wave fronts exhibited strictly
outward propagation while the slower waves could travel both inward
and outward. The estimated phase velocity (80-100 km/s) and period
(3-4 min) of the most stable outward wave mode are in a good agreement
with earlier SOHO EIT and TRACE observations of slow magnetosonic waves
in fan loops. The newly observed features include (1) the remarkable
coherency of the wave pattern over a course of several hours, and (2)
the detailed wave form of the process enabling quantitative analysis
of nonlinear propagation and damping effects. No consistent dependence
of the wave speed on the distance from the hot core region of AR 11082
was identified, which challenges the traditional picture of traveling
magnetoacoustic oscillations in fan loops.

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Title: Stereo Observations Of Fast Magnetosonic Waves In The
Extended Corona
Authors: Kwon, Ryun Young; Davila, J. M.; Ofman, L.
2012AAS...22052106K Altcode:
Here, we present fast magnetosonic waves propagating across solar
radial magnetic fields. STEREO COR1 and EUVI observations showed
coronal disturbances associated with flares/CMEs and they propagate
in the low solar corona in the form of EIT waves and in the high
solar corona (above 1.5 Rs) in the form of density compressions
along radial magnetic field lines above EIT wave fronts. It turns out
that the coronal disturbances pass through streamers which contain
a magnetic separatrix. The wave energy appears to be trapped by the
streamers and this leads to stationary fronts at the footpoints of the
streamers. Our results suggest that the coronal disturbances associated
with flares/CMEs are fast magnetosonic waves propagating with local fast
magnetosonic speeds and passing through magnetic separatrices. Moreover,
we conclude that EIT waves are ‘real’ fast magnetosonic waves. The
speeds of the coronal disturbances are 475 ± 14, 926 ± 19, 1217 ±
24, 1734 ± 48, and 1928 ± 42 km/s at 1.0, 1.6, 2.0, 2.5, and 3.0 Rs,
respectively. Using coronal seismology, we estimated magnetic field
strengths corresponding to these speeds at the heights and they are
1.81 ± 0.06, 0.98 ± 0.02, 0.70 ± 0.01, 0.55 ± 0.02, and 0.39 ±
0.01 G, respectively.

---------------------------------------------------------
Title: Growing Transverse Oscillations of a Multistranded Loop
Observed by SDO/AIA
Authors: Wang, Tongjiang; Ofman, L.; Davila, J. M.; Su, Y.
2012AAS...22020717W Altcode:
The flare-excited transverse loop oscillations previously observed by
TRACE have been mainly interpreted as the global fast kink modes. These
oscillations typically have a rapid decay, and their damping mechanism
has been a major topic of theoretical studies. In this presentation,
we report an unusual case of transverse loop oscillations with growing
amplitudes observed by SDO/AIA for the first time. This oscillation
event was triggered by a flare associated with a CME above the limb. The
multiwavelength analysis reveals that the loop consists of multithermal
strands and their dynamical behaviors are temperature-dependent. These
strands have very similar oscillation frequencies and appear to
oscillate in-phase or in a quarter-period phase delay. These features
suggest the coupling between kink oscillations of neighboring strands
and the interpretation by the collective kink mode as predicted by
some models. The transverse loop oscillations are also associated with
intensity and loop width variations. We determine the trigger of the
oscillation and measure the 3-D loop geometry using STEREO/EUVI-A
data. The possible mechanisms that can excite the growing kink
oscillations will be discussed.

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Title: Impulsively Driven Waves And Flows In Coronal Active Regions
Authors: Ofman, Leon; Wang, T.; Davila, J. M.; Liu, W.
2012AAS...22032204O Altcode:
Recent SDO/AIA and Hinode EIS observations indicate that both (super)
fast and slow magnetosonic waves are present in active region (AR)
magnetic structures. Evidence for fast (100-300 km/s) impulsive flows
is found in spectroscopic and imaging observations of AR loops. The
super-fast waves were observed in magnetic funnels of ARs. The
observations suggest that waves and flow are produced by impulsive
events, such as (micro) flares. We have performed three-dimensional
magnetohydrodynamic (3D MHD) simulations of impulsively generated
flows and waves in coronal loops of a model bi-polar active region
(AR). The model AR is initiated with a dipole magnetic field and
gravitationally stratified density, with impulsively driven flow at
the coronal base of the AR in localized magnetic field structures. We
model the excitation of the flows in hot (6MK) and cold (1MK) active
region plasma, and find slow and fast magnetosonic waves produced by
these events. We also find that high-density (compared to surrounding
corona) loops are produced as a result of the upflows. We investigate
the parametric dependence between the properties of the impulsive
flows and the waves. The results of the 3D MHD modeling study supports
the conjecture that slow magnetosonic waves are often produced by
impulsive upflows along the magnetic field, and fast magnetosonic
waves can result from impulsive transverse field line perturbations
associated with reconnection events. The waves and flows can be used
for diagnostic of AR structure and dynamics.

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Title: Multiscale Dynamics of Interacting Solar Structures
Authors: Uritsky, Vadim; Davila, J. M.
2012AAS...22020113U Altcode:
Sun is an inherently complex and multiscale system which continues to
challenge theorists and experimentalists alike. Coronal holes with
scales typically on the order of a solar radius are the sources of
high speed solar wind streams, and coronal active region magnetic
loops, with typical scales of 10,000 km, exhibit somewhat steady
heating. Direct heating of the coronal plasma, unresolved in current
instruments, takes place at a typical ohmic dissipation scale in the
corona, which is likely to be as small as 100 km. The Sun also exhibits
a broad range of temporal scales. The largest features are observed
to last for months. Coronal holes and coronal streamers can persist
for several 27-day solar rotations with little change, while solar
flares release a vast amount of energy essentially doubling the solar
luminosity for a brief period of a few minutes. It is widely believed
that the ultimate power source for all energy release processes in the
upper solar atmosphere is convection at the solar surface mediated by
magnetic field. Multiscale and nonlocal nature of this process often
prevents its direct identification. Here, we present a new data analysis
framework capable of identifying multiscale spatiotemporal causality
between the photospheric magnetic field and coronal dissipation. The
method involves spatiotemporal tracking of photospheric magnetic
structures and coronal heating events, and their cross-correlation
analysis based on a generalized correlation integral algorithm. The
algorithms use no a priori assumptions regarding the intrinsic spatial
and temporal interaction scales. The performance of the developed
approach in identifying unstable magnetic configurations controlling
coronal dissipation and heating is demonstrated on a variety of solar
conditions, including quiet Sun and a solar active region in flaring
and quiescent states.

---------------------------------------------------------
Title: Spectroscopic Diagnosis of Propagating Disturbances in Coronal
Loops: Waves or flows?
Authors: Wang, T.; Ofman, L.; Davila, J. M.
2012ASPC..456...91W Altcode:
The analysis of multiwavelength properties of propagating disturbances
(PDs) using Hinode/EIS observations is presented. Quasi-periodic PDs
were mostly interpreted as slow magnetoacoustic waves in early studies,
but recently suggested to be intermittent upflows of the order of
50-150 km s-1 based on the Red-Blue (RB) asymmetry analysis
of spectral line profiles. Using the forward models, velocities of the
secondary component derived from the RB analysis are found significantly
overestimated due to the saturation effect when its offset velocities
are smaller than the Gaussian width. We developed a different method
to examine spectral features of the PDs. This method is assuming that
the excessive emission of the PD profile against the background (taken
as that prior to the PD) is caused by a hypothetic upflow. The derived
LOS velocities of the flow are on the order of 10-30 km s-1
from the warm (1-1.5 MK) coronal lines, much smaller than those
inferred from the RB analysis. This result does not support the flow
interpretation but favors of the early wave interpretation.

---------------------------------------------------------
Title: Understanding Solar Energetic Events Using the Next Generation
Coronagraph: High-resolution Imaging with Diagnostic Capability
Authors: Davila, Joseph M.
2012AAS...22042401D Altcode:
What is the mechanism for CME initiation? Soon for the first time
coronagraphs will image and resolve the magnetic field structural
changes in the Corona that lead to the onset of Coronal Mass
Ejections (CMEs). The data provided by these instruments will for the
first time provide a time sequence of high-resolution images showing
the looptop regions where reconnection leading to flares and the
acceleration of energetic particles takes place. These data will enable
the determination of the CME initiation mechanism, without which it is
impossible to understand the physics of the triggering of energetic
events on the Sun. The determination of the cause of flare onset would
be major step toward advance forecasting of CME’s that drive the
radiation environment in near Earth space, and the solar system
in general. These data will also show the magnetic connectivity of
the low corona out to the orbit of Solar Probe Plus and Solar Orbiter.

---------------------------------------------------------
Title: Erratum to: Relation Between Type II Bursts and CMEs Inferred
from STEREO Observations
Authors: Gopalswamy, N.; Thompson, W. T.; Davila, J. M.; Kaiser,
M. L.; Yashiro, S.; Mäkelä, P.; Michalek, G.; Bougeret, J. -L.;
Howard, R. A.
2012SoPh..277..459G Altcode: 2011SoPh..tmp..421G; 2011SoPh..tmp..425G
No abstract at ADS

---------------------------------------------------------
Title: Solar magnetism eXplorer (SolmeX). Exploring the magnetic
field in the upper atmosphere of our closest star
Authors: Peter, Hardi; Abbo, L.; Andretta, V.; Auchère, F.; Bemporad,
A.; Berrilli, F.; Bommier, V.; Braukhane, A.; Casini, R.; Curdt,
W.; Davila, J.; Dittus, H.; Fineschi, S.; Fludra, A.; Gandorfer, A.;
Griffin, D.; Inhester, B.; Lagg, A.; Landi Degl'Innocenti, E.; Maiwald,
V.; Sainz, R. Manso; Martínez Pillet, V; Matthews, S.; Moses, D.;
Parenti, S.; Pietarila, A.; Quantius, D.; Raouafi, N. -E.; Raymond, J.;
Rochus, P.; Romberg, O.; Schlotterer, M.; Schühle, U.; Solanki, S.;
Spadaro, D.; Teriaca, L.; Tomczyk, S.; Trujillo Bueno, J.; Vial, J. -C.
2012ExA....33..271P Altcode: 2011arXiv1108.5304P; 2011ExA...tmp..134P
The magnetic field plays a pivotal role in many fields of
Astrophysics. This is especially true for the physics of the solar
atmosphere. Measuring the magnetic field in the upper solar atmosphere
is crucial to understand the nature of the underlying physical
processes that drive the violent dynamics of the solar corona—that
can also affect life on Earth. SolmeX, a fully equipped solar space
observatory for remote-sensing observations, will provide the first
comprehensive measurements of the strength and direction of the
magnetic field in the upper solar atmosphere. The mission consists
of two spacecraft, one carrying the instruments, and another one in
formation flight at a distance of about 200 m carrying the occulter to
provide an artificial total solar eclipse. This will ensure high-quality
coronagraphic observations above the solar limb. SolmeX integrates two
spectro-polarimetric coronagraphs for off-limb observations, one in
the EUV and one in the IR, and three instruments for observations on
the disk. The latter comprises one imaging polarimeter in the EUV for
coronal studies, a spectro-polarimeter in the EUV to investigate the low
corona, and an imaging spectro-polarimeter in the UV for chromospheric
studies. SOHO and other existing missions have investigated the emission
of the upper atmosphere in detail (not considering polarization),
and as this will be the case also for missions planned for the near
future. Therefore it is timely that SolmeX provides the final piece of
the observational quest by measuring the magnetic field in the upper
atmosphere through polarimetric observations.

---------------------------------------------------------
Title: Growing and coupled transverse oscillations of a multistranded
loop observed by SDO/AIA
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph M.; Su, Yang
2012decs.confE..51W Altcode:
We report the first evidence of transverse oscillations of a
multistranded loop with growing amplitudes and internal coupling
observed by SDO/AIA. The loop oscillations were triggered by a
flare-CME event occurring in an active region visible at the limb. The
multiwavelength analysis reveals the temperature dependence of multiple
strands, which show differences in their oscillation amplitudes,
phases and emission evolution. The physical parameters of growing
transverse oscillations in 171A band are measured and the 3-D loop
geometry is determined using STEREO/EUVI-A data. The strands have very
similar oscillation frequencies and appear to oscillate in-phase or in
a quarter-period phase delay. The observed oscillation properties of
the loop strands agree with theoretically expected coupling between
neighboring strands of a loop that undergoes a global kink mode
oscillation. The transverse loop oscillations are also associated with
intensity and loop width variations. We discuss the possible mechanisms
that can excite the kink oscillations with growing amplitudes, and
their associations with intensity and loop width variations.

---------------------------------------------------------
Title: Modeling waves, flows, and instabilities produced by impulsive
events in coronal active regions
Authors: Ofman, L.; Liu, W.; Wang, T. J.; Davila, J. M.; Thompson,
B. J.
2012decs.confE..73O Altcode:
Recent high-resolution observations by SDO/AIA combined with spectral
data from Hinode provide insights into the properties of MHD waves,
flows, and instabilities in coronal active region plasma and
their connection with impulsive energy release. Shear flow driven
instabilities, such as the Kelvin-Helmholtz (KH) instability were
only recently detected in detail in the corona. I will present recent
results of 3D MHD models of slow and fast magnetosonic waves in active
regions excited by jets and quasi-periodic flows driven by micro-flares
at loops' footpoints. I will discuss models of super-fast magnetosonic
waves detected recently by SDO/AIA. I will also discuss models of global
(EIT) waves, and KH instabilities driven by CMEs. The relations between
waves, flows, instabilities, and impulsive events such as flares and
CMEs are becoming apparent thanks to the combination of observational
data analysis and the 3D MHD modeling. Understanding these relations
is useful for coronal seismology and for tracing the flow of energy
from the transition region to the corona.

---------------------------------------------------------
Title: White Light Coronal Velocity and Temperature Diagnostics
Authors: Davila, Joseph M.; Reginald, Nelson; St. Cyr, O. C.
2012decs.confE..55D Altcode:
During the March 2006 total solar eclipse we conducted an imaging
experiment using the Imaging Spectrograph of Coronal Electrons (ISCORE)
to determine the coronal electron temperature and its radial flow
speed in the low solar corona. This technique required taking images
of the solar eclipse through four broadband filters centered at 385.0,
398.7, 410.0 and 423.3 nm. The K-coronal temperature is determined
from intensity ratios from the 385.0 and 410.0 nm filters, and the
K-coronal radial flow speed is determined from intensity ratios from the
398.7 and 423.3 nm filters. The theoretical model for this technique
assumes a symmetric corona devoid of any features like streamers
that might alter the coronal symmetry. The model also requires an
isothermal temperature and a uniform outflow speed all along the line
of sight. We will call this the Constant Parameter Thomson Scattering
Model (CPTSM). The latter assumption may sound unreasonable but in the
symmetric corona with rapid fall of the electron density with height in
the solar corona, the major contributions to the K-coronal intensity
along a given line of sight comes from the plasma properties in the
vicinity of the plane of the sky. But the pressing question is how is
the derived plasma properties by ISCORE compare with the nature of the
true corona. For this we turn to the CORHEL model by Predictive Science
Inc. which used magnetogram data to create a realistic model of the
solar corona that are made available through the Community Coordinated
Modeling Center (CCMC) at GSFC. That team has consistently produced
the expected coronal image days prior to many total eclipses where
the major coronal features from their model matched actual coronal
image on the day of the eclipse. Using the CORHEL model data we
have calculated the K-coronal intensities at 385.0, 398.7, 410.0 and
423.3 nm using the electron density, plasma temperature (assumed to
be electron temperature) and the flow speeds of the plasma along the
line of sight in the CORHEL model and have calculated the temperature
and radial flow speed sensitive intensity ratios. Next we identify the
isothermal electron temperature and the radial flow speed in the CPTSM
model that would match the temperature sensitive and radial flow speed
sensitive intensity ratios from the CORHEL model and compare the CPTSM
temperature and flow speed values with the corresponding values in
the CORHEL model in the plane of the sky. These comparisons were made
for Carrington Rotation 1977 with the CORHEL model of the solar corona
rotated in intervals of 45 degrees with respect to the observer located
at 1 AU. The average of the difference between the electron temperatures
and the radial flow speed at 5 solar radii in the East-West direction
were (underestimated by 0.02 MK or an error of 1.7%) and (overestimated
by 22.km/sec or an error of 18%), respectively and in the South-North
direction were (underestimated by 0.04 MK or an error of 3.2%) and
(overestimated by 42 km/sec or an error of 21%), respectively.

---------------------------------------------------------
Title: Multiscale Dynamics of Solar Magnetic Structures
Authors: Uritsky, Vadim M.; Davila, Joseph M.
2012ApJ...748...60U Altcode: 2011arXiv1111.5053U
Multiscale topological complexity of the solar magnetic field is
among the primary factors controlling energy release in the corona,
including associated processes in the photospheric and chromospheric
boundaries. We present a new approach for analyzing multiscale behavior
of the photospheric magnetic flux underlying these dynamics as depicted
by a sequence of high-resolution solar magnetograms. The approach
involves two basic processing steps: (1) identification of timing
and location of magnetic flux origin and demise events (as defined
by DeForest et al.) by tracking spatiotemporal evolution of unipolar
and bipolar photospheric regions, and (2) analysis of collective
behavior of the detected magnetic events using a generalized version
of the Grassberger-Procaccia correlation integral algorithm. The
scale-free nature of the developed algorithms makes it possible to
characterize the dynamics of the photospheric network across a wide
range of distances and relaxation times. Three types of photospheric
conditions are considered to test the method: a quiet photosphere, a
solar active region (NOAA 10365) in a quiescent non-flaring state, and
the same active region during a period of M-class flares. The results
obtained show (1) the presence of a topologically complex asymmetrically
fragmented magnetic network in the quiet photosphere driven by meso- and
supergranulation, (2) the formation of non-potential magnetic structures
with complex polarity separation lines inside the active region, and
(3) statistical signatures of canceling bipolar magnetic structures
coinciding with flaring activity in the active region. Each of these
effects can represent an unstable magnetic configuration acting as an
energy source for coronal dissipation and heating.

---------------------------------------------------------
Title: Three-Dimensional MHD Models of Waves and Flows in Coronal
Active Region Loops
Authors: Ofman, L.; Wang, T.; Davila, J. M.
2011AGUFMSH34B..02O Altcode:
Recent observations show that slow magnetosonic waves are present in
active region loops, and are often associated with subsonic up-flows
of coronal material. In order to study the relation between up-flows
and waves we develop a 3D MHD model of an idealized bi-polar active
region with flows in coronal loops. The model is initiated with a
dipole magnetic field and gravitationally stratified isothermal
atmosphere. To model the effects of flares, coronal material is
injected in small-scale regions at the base of the model active
region. The up-flows have sub-sonic speeds of ∼100 km/s and are
steady or periodic, producing higher density loops by filling magnetic
flux-tubes with injected material. We find that the up-flows produce
fast and slow magnetosonic waves that propagate in the coronal loops. We
perform a parametric study of up-flow magnitude and periodicity, and the
relation with the resulting waves. As expected, we find that the up-flow
speed decreases with loop height due to the diverge of the flux tubes,
while the slow magnetosonic speed is independent of height. When the
amplitude of the driving pulses is increased above the sound speed,
we find that slow shocks are produced in the loops. Using the results
of the 3D MHD model we show that observed slow magnetosonic waves in
active region loops can be driven by impulsive flare-produced up-flows
at the transition region/corona interface of active regions.

---------------------------------------------------------
Title: Propagating low-frequency waves in coronal streamers observed
by STEREO COR1
Authors: Kwon, R.; Davila, J. M.; Ofman, L.
2011AGUFMSH43C1981K Altcode:
Compressional and transverse propagating waves high above the solar
surface may play an important role in heating and accelerating the solar
wind. Waves with periods of about an hour were detected in streamers
in the past using SOHO/LASCO observations. STEREO COR1 provides us
with the coronagraph (~4 solar radius) with high temporal resolution
(5 min time cadence) so that it allows us to study low frequency waves
systematically and address line-of-sight ambiguity. We present a method
to detect the periodic oscillations along coronal streamers observed
by STEREO COR1 and to determine the wavelength, period and phase speed
with wavelet analysis. Further, we discuss physical implications of
our results and the possible origin of the waves we found.

---------------------------------------------------------
Title: Underflight Calibration of SOHO/CDS and Hinode/EIS with
EUNIS-07
Authors: Wang, Tongjiang; Thomas, Roger J.; Brosius, Jeffrey W.; Young,
Peter R.; Rabin, Douglas M.; Davila, Joseph M.; Del Zanna, Giulio
2011ApJS..197...32W Altcode: 2011arXiv1109.6598W
Flights of Goddard Space Flight Center's Extreme Ultraviolet
Normal Incidence Spectrograph (EUNIS) sounding rocket in 2006
and 2007 provided updated radiometric calibrations for Solar and
Heliospheric Observatory/Coronal Diagnostic Spectrometer (SOHO/CDS)
and Hinode/Extreme Ultraviolet Imaging Spectrometer (Hinode/EIS). EUNIS
carried two independent imaging spectrographs covering wavebands of
300-370 Å in first order and 170-205 Å in second order. After each
flight, end-to-end radiometric calibrations of the rocket payload were
carried out in the same facility used for pre-launch calibrations of
CDS and EIS. During the 2007 flight, EUNIS, SOHO/CDS, and Hinode/EIS
observed the same solar locations, allowing the EUNIS calibrations to
be directly applied to both CDS and EIS. The measured CDS NIS 1 line
intensities calibrated with the standard (version 4) responsivities with
the standard long-term corrections are found to be too low by a factor
of 1.5 due to the decrease in responsivity. The EIS calibration update
is performed in two ways. One uses the direct calibration transfer of
the calibrated EUNIS-07 short wavelength (SW) channel. The other uses
the insensitive line pairs, in which one member was observed by the
EUNIS-07 long wavelength (LW) channel and the other by EIS in either the
LW or SW waveband. Measurements from both methods are in good agreement,
and confirm (within the measurement uncertainties) the EIS responsivity
measured directly before the instrument's launch. The measurements also
suggest that the EIS responsivity decreased by a factor of about 1.2
after the first year of operation (although the size of the measurement
uncertainties is comparable to this decrease). The shape of the EIS SW
response curve obtained by EUNIS-07 is consistent with the one measured
in laboratory prior to launch. The absolute value of the quiet-Sun
He II 304 Å intensity measured by EUNIS-07 is consistent with the
radiance measured by CDS NIS in quiet regions near the disk center
and the solar minimum irradiance recently obtained by CDS NIS and the
Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment.

---------------------------------------------------------
Title: Determination of Non-thermal Velocity Distributions from
SERTS Linewidth Observations
Authors: Coyner, Aaron J.; Davila, Joseph M.
2011ApJ...742..115C Altcode:
Non-thermal velocities obtained from the measurement of coronal Extreme
Ultraviolet (EUV) linewidths have been consistently observed in solar
EUV spectral observations and have been theorized to result from many
plausible scenarios including wave motions, turbulence, or magnetic
reconnection. Constraining these velocities can provide a physical
limit for the available energy resulting from unresolved motions in
the corona. We statistically determine a series of non-thermal velocity
distributions from linewidth measurements of 390 emission lines from a
wide array of elements and ionization states observed during the Solar
Extreme Ultraviolet Research Telescope and Spectrograph 1991-1997
flights covering the spectral range 174-418 Å and a temperature
range from 80,000 K to 12.6 MK. This sample includes 248 lines from
active regions, 101 lines from quiet-Sun regions, and 41 lines were
observed from plasma off the solar limb. We find a strongly peaked
distribution corresponding to a non-thermal velocity of 19-22 km
s-1 in all three of the quiet-Sun, active region, and
off-limb distributions. For the possibility of Alfvén wave resonance
heating, we find that velocities in the core of these distributions do
not provide sufficient energy, given typical densities and magnetic
field strengths for the coronal plasma, to overcome the estimated
coronal energy losses required to maintain the corona at the typical
temperatures working as the sole mechanism. We find that at perfect
efficiency 50%-60% of the needed energy flux can be produced from the
non-thermal velocities measured.

---------------------------------------------------------
Title: High-resolution solar imaging with a photon sieve
Authors: Davila, J. M.
2011AGUFMSH33B2053D Altcode:
Dissipation in the solar corona is expected to occur in extremely
thin current sheets of order 1-100 km. Emission from these current
sheets should be visible in coronal EUV emission lines. However,
this spatial scale is far below the resolution of existing imaging
instruments, because conventional optics cannot be easily manufactured
with sufficient surface figure accuracy to obtain the required &lt;
0.1 arcsec resolution. A photon sieve, a diffractive imaging element,
can be manufactured to provide a few 10-3 arcsec resolution, with
much more relaxed tolerances than conventional imaging technology. A
simple design for a sounding rocket payload is presented that obtain
80 mArcsec imaging with a 100 mm diameter photon sieve to image Fe XIV
334 and Fe XVI 335. These images will not only show the structure of
the corona at a resolution never before obtained, they will also allow
a study of the temperature structure.

---------------------------------------------------------
Title: Technique to Measure the Coronal Electron Temperature and
Radial Flow Speed
Authors: Reginald, N. L.; Davila, J. M.; St Cyr, O. C.
2011AGUFMSH43F..02R Altcode:
During the March 2006 total solar eclipse we conducted an imaging
experiment using the Imaging Spectrograph of Coronal Electrons (ISCORE)
to determine the coronal electron temperature and its radial flow
speed in the low solar corona. This technique required taking images
of the solar eclipse through four broadband filters centered at 385.0,
398.7, 410.0 and 423.3 nm. The K-coronal temperature is determined
from intensity ratios from the 385.0 and 410.0 nm filters, and the
K-coronal radial flow speed is determined from intensity ratios from the
398.7 and 423.3 nm filters. The theoretical model for this technique
assumes a symmetric corona devoid of any features like streamers
that might alter the coronal symmetry. The model also requires an
isothermal temperature and a uniform outflow speed all along the line
of sight. We will call this the Constant Parameter Thomson Scattering
Model (CPTSM). The latter assumption may sound unreasonable but in the
symmetric corona with rapid fall of the electron density with height in
the solar corona, the major contributions to the K-coronal intensity
along a given line of sight comes from the plasma properties in the
vicinity of the plane of the sky. But the pressing question is how is
the derived plasma properties by ISCORE compare with the nature of the
true corona. For this we turn to the CORHEL model by Predictive Science
Inc. which used magnetogram data to create a realistic model of the
solar corona that are made available through the Community Coordinated
Modeling Center (CCMC) at GSFC. That team has consistently produced
the expected coronal image days prior to many total eclipses where
the major coronal features from their model matched actual coronal
image on the day of the eclipse. Using the CORHEL model data we
have calculated the K-coronal intensities at 385.0, 398.7, 410.0 and
423.3 nm using the electron density, plasma temperature (assumed to
be electron temperature) and the flow speeds of the plasma along the
line of sight in the CORHEL model and have calculated the temperature
and radial flow speed sensitive intensity ratios. Next we identify the
isothermal electron temperature and the radial flow speed in the CPTSM
model that would match the temperature sensitive and radial flow speed
sensitive intensity ratios from the CORHEL model and compare the CPTSM
temperature and flow speed values with the corresponding values in
the CORHEL model in the plane of the sky. These comparisons were made
for Carrington Rotation 1977 with the CORHEL model of the solar corona
rotated in intervals of 45 degrees with respect to the observer located
at 1 AU. The average of the difference between the electron temperatures
and the radial flow speed at 5 solar radii in the East-West direction
were (underestimated by 0.02 MK or an error of 1.7%) and (overestimated
by 22.km/sec or an error of 18%), respectively and in the South-North
direction were (underestimated by 0.04 MK or an error of 3.2%) and
(overestimated by 42 km/sec or an error of 21%), respectively.

---------------------------------------------------------
Title: Multi-scale Energy Dissipation on the Sun
Authors: Davila, J. M.; Uritsky, V. M.
2011AGUFMSH51C2021D Altcode:
The outer atmosphere of the Sun is powered by the release of energy
over a broad range of spatial and temporal scales. Coronal holes with
scales typically on the order of a solar radius (6.95 x 10^5 km) are
the sources of high speed solar wind streams, and coronal active region
magnetic loops, with typical scales of 10,000 km, exhibit somewhat
steady heating. Direct heating of the coronal plasma, unresolved in
current instruments, takes place at a typical ohmic dissipation scale
in the corona, which is likely to be as small as 100 km. The Sun also
exhibits a broad range of temporal scales. The largest features are
observed to last for months. Coronal holes and coronal streamers can
persist for several 27-day solar rotations with little change. Solar
flares release a vast amount of energy essentially doubling the
solar luminosity for a brief period of a few minutes. Within these
events time variability is observed down to a few milli-seconds. It
is widely believed that the ultimate power source for all energy
release processes in the upper solar atmosphere is convection at the
solar surface. Convective flows (1) generate the magnetic field in
the convection zone of the Sun, and (2) stress the field generating
electrical currents allowing the buildup of energy in localized regions
over time. How is the broad range of scales observed on the Sun coupled
together? How is energy converted from local dissipation sites into
the diffuse corona observed? How are the upper atmospheric layers,
the corona and chromospheres, coupled to convective motions in the
photosphere, the presumed energy source? How do these processes drive
hazardous space weather events which exhibit power-law statistics
characteristic of dynamical systems at criticality, and how good are
our chances to predict such events considering their inherent multiscale
origin? These are significant open questions that remain to be answered.

---------------------------------------------------------
Title: Vector Tomography Inversion for the 3D Coronal Magnetic Field
Based on CoMP data
Authors: Kramar, M.; Lin, H.; Tomczyk, S.; Inhester, B.; Davila, J. M.
2011AGUFMSH43B1948K Altcode:
Magnetic fields in the solar corona dominates the gas pressure
and therefore determine the static and dynamic properties of the
corona. Direct measurement of the coronal magnetic field is one of
the most challenging problems in observational solar astronomy and
recently a significant progress has been achieved here with deployment
of the HAO Coronal Multichannel Polarimeter (CoMP). The instrument
provides polarization measurements of Fe XIII 10747 A forbidden line
emission. The observed polarization depends on magnetic field through
the Hanle and Zeeman effects. However, because the coronal measurements
are integrated over line-of-site (LOS), it is impossible to derive the
configuration of the coronal magnetic field from a single observation
(from a single viewing direction). The vector tomography techniques
based on measurements from several viewing directions has the potential
to resolve the 3D coronal magnetic field structure over LOS. Because
of the non-linear character of the Hanle effect, the reconstruction
result based on such data is not straightforward and depends on the
particular coronal field configuration. Therefore we study here what is
the sensitivity of the vector tomographic inversion to sophisticated
(MHD) coronal magnetic field models. For several important cases of
magnetic field configuration, it has been found that even just Stokes-Q
and -U data (supplied with 3D coronal density and temperature) can be
used in vector tomography to provide a realistic 3D coronal magnetic
field configuration. This vector tomograpic technique is applied to
CoMP data.

---------------------------------------------------------
Title: United Nations Basic Space Science Initiative: 2010 Status
Report on the International Space Weather Initiative
Authors: Gadimova, S.; Haubold, H. J.; Danov, D.; Georgieva, K.;
Maeda, G.; Yumoto, K.; Davila, J. M.; Gopalswamy, N.
2011SunGe...6....7G Altcode: 2011arXiv1108.2247G
The UNBSSI is a long-term effort for the development of astronomy
and space science through regional and international cooperation in
this field on a worldwide basis. A series of workshops on BSS was
held from 1991 to 2004 (India 1991, Costa Rica and Colombia 1992,
Nigeria 1993, Egypt 1994, Sri Lanka 1995, Germany 1996, Honduras
1997, Jordan 1999, France 2000, Mauritius 2001, Argentina 2002, and
China 2004) Pursuant to resolutions of the United Nations Committee
on the Peaceful Uses of Outer Space (UNCOPUOS) and its Scientific
and Technical Subcommittee, since 2005, these workshops focused on
the International Heliophysical Year 2007 (UAE 2005, India 2006,
Japan 2007, Bulgaria 2008, Ro Korea 2009) Starting in 2010, the
workshops focus on the International Space Weather Initiative (ISWI)
as recommended in a three-year-work plan as part of the deliberations
of UNCOPUOS (www.iswi-secretariat.org/). Workshops on the ISWI have
been scheduled to be hosted by Egypt in 2010 for Western Asia, Nigeria
in 2011 for Africa, and Ecuador in 2012 for Latin America and the
Caribbean. Currently, fourteen IHY/ISWI instrument arrays with more
than five hundred instruments are operational in ninety countries.

---------------------------------------------------------
Title: Earth-Affecting Solar Causes Observatory (EASCO): a mission
at the Sun-Earth L5
Authors: Gopalswamy, Nat; Davila, Joseph M.; Auchère, Frédéric;
Schou, Jesper; Korendyke, Clarence M.; Shih, Albert; Johnston, Janet
C.; MacDowall, Robert J.; Maksimovic, Milan; Sittler, Edward; Szabo,
Adam; Wesenberg, Richard; Vennerstrom, Suzanne; Heber, Bernd
2011SPIE.8148E..0ZG Altcode: 2011SPIE.8148E..30G; 2011arXiv1109.2929G
Coronal mass ejections (CMEs) and corotating interaction regions
(CIRs) as well as their source regions are important because of
their space weather consequences. The current understanding of CMEs
primarily comes from the Solar and Heliospheric Observatory (SOHO)
and the Solar Terrestrial Relations Observatory (STEREO) missions,
but these missions lacked some key measurements: STEREO did not have a
magnetograph; SOHO did not have in-situ magnetometer. SOHO and other
imagers such as the Solar Mass Ejection Imager (SMEI) located on the
Sun-Earth line are also not well-suited to measure Earth-directed
CMEs. The Earth-Affecting Solar Causes Observatory (EASCO) is a
proposed mission to be located at the Sun-Earth L5 that overcomes
these deficiencies. The mission concept was recently studied at the
Mission Design Laboratory (MDL), NASA Goddard Space Flight Center,
to see how the mission can be implemented. The study found that the
scientific payload (seven remote-sensing and three in-situ instruments)
can be readily accommodated and can be launched using an intermediate
size vehicle; a hybrid propulsion system consisting of a Xenon ion
thruster and hydrazine has been found to be adequate to place the
payload at L5. Following a 2-year transfer time, a 4-year operation
is considered around the next solar maximum in 2025.

---------------------------------------------------------
Title: High-resolution solar imaging with a photon sieve
Authors: Davila, Joseph M.
2011SPIE.8148E..0OD Altcode: 2011SPIE.8148E..22D
Dissipation in the solar corona is expected to occur in extremely
thin current sheets of order 1-100 km. Emission from these current
sheets should be visible in coronal EUV emission lines. However,
this spatial scale is far below the resolution of existing imaging
instruments. Conventional optics cannot be easily manufactured with
sufficient surface figure accuracy to obtain the required &lt; 0.1
arcsec resolution. A photon sieve, a diffractive imaging element
similar to a Fresnel zone plate, can be manufactured to provide a
few 0.001 arcsec resolution, with much more relaxed tolerances than
conventional imaging technology. A simple design for a sounding rocket
payload is presented that obtains 80 mas (0.080 arcsec) imaging with a
100 mm diameter photon sieve to image Fe XIV 334 and Fe XVI 335. These
images will not only show the structure of the corona at a resolution
never before obtained, they will also allow a study of the temperature
structure in the dissipation region.

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Title: New GPS constraints on active deformation along the
Africa-Iberia plate boundary
Authors: Koulali, A.; Ouazar, D.; Tahayt, A.; King, R. W.; Vernant,
P.; Reilinger, R. E.; McClusky, S.; Mourabit, T.; Davila, J. M.;
Amraoui, N.
2011E&PSL.308..211K Altcode:
We use velocities from 65 continuous stations and 31 survey-mode
GPS sites as well as kinematic modeling to investigate present day
deformation along the Africa-Iberia plate boundary zone in the western
Mediterranean region. The GPS velocity field shows southwestward motion
of the central part of the Rif Mountains in northern Morocco with
respect to Africa varying between 3.5 and 4.0 mm/yr, consistent with
prior published results. Stations in the southwestern part of the Betic
Mountains of southern Spain move west-southwest with respect to Eurasia
(∼ 2-3 mm/yr). The western component of Betics motion is consistent
with partial transfer of Nubia-Eurasia plate motion into the southern
Betics. The southward component of Betics motion with respect to Iberia
is kinematically consistent with south to southwest motion of the Rif
Mountains with respect to Africa. We use block modeling, constrained by
mapped surface faults and seismicity to estimate the geometry and rates
of strain accumulation on plate boundary structures. Our preferred plate
boundary geometry includes one block between Iberia and Africa including
the SW Betics, Alboran Sea, and central Rif. This geometry provides
a good fit to the observed motions, suggesting a wide transpressive
boundary in the westernmost Mediterranean, with deformation mainly
accommodated by the Gloria-Azores fault system to the West and the
Rif-Tell lineament to the East. Block boundaries encompass aspects
of earlier interpretations suggesting three main deformation styles:
(i) extension along the NE-SW trending Trans-Alboran shear zone, (ii)
dextral strike-slip in the Betics corresponding to a well defined E-W
seismic lineament, and (iii) right lateral strike-slip motion extending
West to the Azores and right-lateral motion with compression extending
East along the Algerian Tell. We interpret differential motion in the
Rif-Alboran-Betic system to be driven both by surface processes related
the Africa-Eurasia oblique convergence and sub-crustal dynamic processes
associated with the long history of subduction of the Neotethys ocean
lithosphere. The dextral slip identified in the Betic Mountains in
Southern Spain may be related to the offshore fault that produced the
Great 1755 Lisbon Earthquake, and as such may represent a significant
seismic hazard for the West Mediterranean region.

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Title: STEREO SECCHI COR1-A/B Intercalibration at 180° Separation
Authors: Thompson, W. T.; Davila, J. M.; St. Cyr, O. C.; Reginald,
N. L.
2011SoPh..272..215T Altcode: 2011SoPh..tmp..204T; 2011SoPh..tmp..324T; 2011SoPh..tmp..273T;
2011SoPh..tmp..299T
The twin Solar Terrestrial Relations Observatory (STEREO) spacecraft
reached a separation angle of 180° on 6 February 2011. This provided a
unique opportunity to test the intercalibration between the Sun-Earth
Connection Coronal and Heliospheric Investigation (SECCHI) telescopes
on both spacecraft for areas above the limb. So long as the corona
is optically thin, at 180° separation each spacecraft sees the same
corona from opposite directions. Thus, the data should appear as mirror
images of each other. We report here on the results of the comparison
of the images taken by the inner coronagraph (COR1) on the STEREO-Ahead
and -Behind spacecraft in the hours when the separation was close to
180°. We find that the intensity values seen by the two telescopes
agree with each other to a high degree of accuracy. This validates both
the radiometric intercalibration between the COR1 telescopes, and the
method used to remove instrumental background from the images. The
relative error between COR1-A and COR1-B is found to be less than
10−9B/B⊙ over most of the field-of-view,
growing to a few ×10−9B/B⊙ for the brighter
pixels near the edge of the occulter. The primary source of error is
the background determination. We also report on the analysis of star
observations which show that the absolute radiometric calibration of
either COR1 telescope has not changed significantly since launch.

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Title: Analysis and study of the in situ observation of the June
1st 2008 CME by STEREO
Authors: Nieves-Chinchilla, T.; Gómez-Herrero, R.; Viñas, A. F.;
Malandraki, O.; Dresing, N.; Hidalgo, M. A.; Opitz, A.; Sauvaud,
J. -A.; Lavraud, B.; Davila, J. M.
2011JASTP..73.1348N Altcode:
In this work we present a combined study of the counterpart of the
coronal mass ejection (CME) of June 1st of 2008 in the interplanetary
medium. This event has been largely studied because of its peculiar
initiation and its possible forecasting consequences for space
weather. We show an in situ analysis (on days June 6th-7th of 2008)
of the CME in the interplanetary medium in order to shed some light
on the propagation and evolution mechanisms of the interplanetary CME
(ICME). The goals of this work are twofold: gathering the whole in situ
data from PLASTIC and IMPACT onboard STEREO B in order to provide a
complete characterization of the ICME, and to present a model where the
thermal plasma pressure is included. The isolated ICME features show a
clear forward shock which we identify as an oblique forward fast shock
accelerating ions to a few-hundred keV during its passage. Following
the shock, a flux rope is easily defined as a magnetic cloud (MC)
by the magnetic field components and magnitude, and the low proton
plasma-β. During the spacecraft passage through the MC, the energetic
ion intensity shows a pronounced decrease, suggesting a closed magnetic
topology, and the suprathermal electron population shows a density and
temperature increase, demonstrating the importance of the electrons
in the MC description. The in situ evidence suggests that there is
no direct magnetic connection between the forward shock and the MC,
and the characteristics of the reverse shock determined suggest that
the shock pair is a consequence of the propagation of the ICME in
the interplanetary medium. The energetic ions measured by the SEPT
instrument suggest that their enhancement is not related to any solar
event, but is solely due to the interplanetary shock consistent with
the fact that no flares are observed on the Sun. The changes in the
polarity of the interplanetary magnetic field in the vicinity of the
ICME observed by electron PADs from SWEA are in accordance with the
idea that the CME originated along a neutral line over the quiet Sun.The
magnetic cloud model presented in this work provides the plasma pressure
as a new factor to consider in the study of the expansion and evolution
of CMEs in the interplanetary medium. This model could provide a new
understanding of the Sun-Earth connection because of the important role
that the plasma plays in the eruption of the CME in the solar corona
and the reconnection process carried out with the Earth's magnetosphere.

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Title: Electron Temperatures and Flow Speeds of the Low Solar Corona:
MACS Results from the Total Solar Eclipse of 29 March 2006 in Libya
Authors: Reginald, Nelson L.; Davila, Joseph M.; St. Cyr, O. C.; Rabin,
Douglas M.; Guhathakurta, Madhulika; Hassler, Donald M.; Gashut, Hadi
2011SoPh..270..235R Altcode: 2011SoPh..tmp...68R; 2011SoPh..tmp...48R
An experiment was conducted in conjunction with the total solar eclipse
on 29 March 2006 in Libya to measure both the electron temperature
and its flow speed simultaneously at multiple locations in the low
solar corona by measuring the visible K-coronal spectrum. Coronal model
spectra incorporating the effects of electron temperature and its flow
speed were matched with the measured K-coronal spectra to interpret
the observations. Results show electron temperatures of (1.10±0.05)
MK, (0.70±0.08) MK, and (0.98±0.12) MK, at 1.1 R⊙
from Sun center in the solar north, east and west, respectively, and
(0.93±0.12) MK, at 1.2 R⊙ from Sun center in the solar
west. The corresponding outflow speeds obtained from the spectral
fit are (103±92) km s−1, (0+10) km s−1,
(0+10) km s−1, and (0+10) km s−1. Since
the observations were taken only at 1.1 R⊙ and 1.2
R⊙ from Sun center, these speeds, consistent with zero
outflow, are in agreement with expectations and provide additional
confirmation that the spectral fitting method is working. The electron
temperature at 1.1 R⊙ from Sun center is larger at the
north (polar region) than the east and west (equatorial region).

---------------------------------------------------------
Title: Statistical Determination and Comparison of Non-thermal
Velocity Distributions from EIS Full-CCD Linewidth Measurements
Authors: Coyner, Aaron J.; Davila, J. M.; Kilper, G. K.
2011SPD....42.1816C Altcode: 2011BAAS..43S.1816C
Excess broadening in the emission line spectra from non-thermal
motions provide an unresolved energy input into the coronal
plasma. The driving mechanism for and significance of the energy
contributions of this non-thermal component has been a subject of much
discussion. Observationally constraining the non-thermal contributions
to line broadening in the coronal emission spectra provides valuable
limitations which coronal physics models must take into account. Using
full-CCD raster observations from EIS, we determine a distribution
of non-thermal velocities for all lines in each full-CCD raster
observation for both spatially-averaged and spatially-resolved EIS
spectra. We present here composite non-thermal velocity distributions
incorporating a multiple elements, ionization states and temperatures
for a variety of EIS observations including both active region
and quiet sun emission. We determine an expectation value for the
velocity of the non-thermal component from this composite statistical
approach. Initial spatially-averaged results from 7 independent EIS
rasters show a strong Gaussian peak at approximately 20 km/s per
second.. We address the implications of this consistent velocity and
energy peak in the spatially-averaged results as well as present and
compare our analysis from spatially-resolved spectra for each EIS
raster included in the spatially-averaged study.

---------------------------------------------------------
Title: Evidence For Forced Kink-mode Loop Oscillations Observed
By Sdo/aia
Authors: Wang, Tongjiang; Ofman, L.; Davila, J. M.; Su, Y.
2011SPD....42.2113W Altcode: 2011BAAS..43S.2113W
Transverse loop oscillations were first discovered by TRACE in EUV
wavelength and interpreted as global fast kink modes. These oscillations
are impulsively excited by flares or filament eruptions and often show
a strong damping within few oscillation periods. The oscillations and
the damping mechanism have been intensively studied in observation
and theory, leading to great advance in coronal seismology. However,
measurements of the damping rate remains difficult, often limited
by the short length of the detectable oscillation sequence in one
single filter. SDO/AIA with multiple wavebands of unprecedentedly high
sensitivity and wide temperature coverage provides a good opportunity
in improving the accuracy of these measurements. Here we present an
example of long-lasting oscillation events observed using SDO/AIA. In
this event, kink oscillations of a slowly evolving coronal loop seen
in 171, 193 and 211 A bands are excited by several flow ejections. The
oscillations last over one and a half hours with periods of 3-4 min
and no evident decay. In particular, the amplitudes of the oscillations
show increase during the period of a large flow ejection with speeds of
200-300 km/s which lasts for about a half hour, and then falls down at
speeds of 60-70 km/s measured in 304 A band. We interpret the growing
oscillations as driven fast magnetosonic waves by impacting flows. We
perform preliminary 3D MHD study of the event using an idealized
bipolar active region model.

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Title: 3D Structure and the Evolution of EUV Bright Points Observed
by STEREO/SECCHI/EUVI: Evidence for Coronal Magnetic Reconnection
Driven by Emerging Magnetic Flux?
Authors: Kwon, Ryun Young; Davila, J. M.; Ofman, L.
2011SPD....42.1808K Altcode: 2011BAAS..43S.1808K
The 3D structure of EUV bright points and its physical relation
with the underlying magnetic flux concentrations are unveiled here
observationally for the first time. The heights of EUV bright points
have been measured within their lifetimes by 3D reconstruction method
developed by Kwon, Chae, &amp; Zhang (2010) using data sets taken from
STEREO/SECCHI/EUVI. We found three distinct changes in the heights which
were decreasing, increasing, and constant. In general, EUV bright points
are multi-temperature loop system whose hot loops (T 106.2K)
with an average height of 8.9Mm are overlying cooler loops (T &lt;
106.0K) with an average height of 6.7Mm. This loop system has
cool legs which have the peak temperature of T 104.9K and
an average height of 5.2Mm. The heights were found to have remarkable
correlations with lengths and distances of two opposite magnetic
flux concentrations, indicating that the 3D structures of bright
points were determined by the geometry of associated photospheric
magnetic fluxes. Accordingly, the three types of bright points we
found were associated with three distinct types of their underlying
magnetic fragments: converging, diverging, and shearing. In all cases,
both flux emergences and flux cancellations were observed during the
lifetimes of the bright points. The flux emergences were dominant in
the initial phase and the flux cancellations were significant after
the intensities reached their maxima. Our results suggest that EUV
bright points may be the flaring loop systems (Masuda et al. 1994)
formed by coroanl magnetic reconnection and the flux emergence appears
to be important to driving the coronal magnetic reconnection.

---------------------------------------------------------
Title: Deconvolution of Spatial and Spectral Information in Slitless
Spectrometer Images
Authors: Jones, Shaela I.; Davila, J. M.
2011SPD....42.1508J Altcode: 2011BAAS..43S.1508J
Observation of coronal emission has greatly enhanced our understanding
of the solar corona. However, to date solar scientists have been
forced to choose between the large fields of view offered by imaging
telescopes and the detailed spectral information offered by imaging
spectrometers. In order to measure spectral characteristics over large
portions of the corona, imaging spectrometers must raster over the area,
a time-consuming process that lowers the effective time cadence of the
resulting observations and causes confusion between spatial and temporal
variation. Slitless spectrometers, which produce images with convolved
spatial and spectral information from a relatively large field of view,
offer the opportunity to study the emission line profiles of large
regions of the corona without rastering, if the spatial and spectral
information can be reliably deconvolved. Here we present a study of
the potential capabilities of such an instrument, including examples
showing deconvolution of artificial slitless spectrometer images
based on Hinode EIS spectral measurements. We compare the expected
accuracy of intensities, linewidths, and doppler shifts measured
using our deconvolution technique to those derived from fitting of
EIS spectral data.

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Title: Solar Eruptive Events (SEE) Mission for the Next Solar Maximum
Authors: Lin, Robert P.; Krucker, S.; Caspi, A.; Hurford, G.; Dennis,
B.; Holman, G.; Christe, S.; Shih, A. Y.; Bandler, S.; Davila, J.;
Milligan, R.; Kahler, S.; Weidenbeck, M.; Doschek, G.; Vourlidas,
A.; Share, G.; Raymond, J.; McConnell, M.; Emslie, G.
2011SPD....42.2204L Altcode: 2011BAAS..43S.2204L
Major solar eruptive events consisting of both a large flare and a
near simultaneous large fast coronal mass ejection (CME), are the most
powerful explosions and also the most powerful and energetic particle
accelerators in the solar system, producing solar energetic particles
(SEPs) up to tens of GeV for ions and 10s-100s of MeV for electrons. The
intense fluxes of escaping SEPs are a major hazard for humans in space
and for spacecraft. Furthermore, the solar plasma ejected at high speed
in the fast CME completely restructures the interplanetary medium,
producing the most extreme space weather in geospace, at other planets,
and in the heliosphere. Thus, the understanding of the flare/CME
energy release process and of the related particle acceleration
processes in SEEs is a major goal in Heliophysics. Here we present
a concept for a Solar Eruptive Events (SEE) mission, consisting of a
comprehensive set of advanced new instruments on the single spacecraft
in low Earth orbit, that focus directly on the coronal energy release
and particle acceleration in flares and CMEs. SEE will provide new
focussing hard X-ray imaging spectroscopy of energetic electrons in the
flare acceleration region, new energetic neutral atom (ENA) imaging
spectroscopy of SEPs being accelerated by the CME at altitudes above
2 solar radii, gamma-ray imaging spectroscopy of flare-accelerated
energetic ions, plus detailed EUV/UV/Soft X-ray diagnostics of the
plasmas density, temperature, and mass motions in the energy release and
particle acceleration regions. Together with ground-based measurements
of coronal magnetic fields from ATST, FASR, and COSMO, SEE will enable
major breakthroughs in our understanding of the fundamental physical
processes involved in major solar eruptive events.

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Title: Investigations to Determine the Origin of the Solar Wind with
SPICE and SolarOrbiter
Authors: Hassler, Donald M.; DeForest, C.; Wilkinson, E.; Davila,
J.; SPICE Team
2011SPD....42.2402H Altcode: 2011BAAS..43S.2402H
At large spatial scales, the structure of the solar wind and it's
mapping back to the solar corona, is thought to be reasonably well
understood. However, the detailed structure of the various source
regions at chromospheric and transition region heights is extremely
complex, and less well understood. Determining this connection
between heliospheric structures and their source regions at the Sun
is one of the overarching objective of the Solar Orbiter mission. During perihelion segments of its orbit, when the spacecraft is
in quasi-corotation with the Sun, Solar Orbiter will determine the
plasma parameters and compositional signatures of the solar wind,
which can be compared directly with the spectroscopic signatures of
coronal ions with differing charge-to-mass ratios and FIP. One of the
key instruments on the Solar Orbiter mission to make these remote
sensing measurements is the SPICE (Spectral Imaging of the Coronal
Environment) imaging spectrograph. SPICE will provide the images and
plasma diagnostics needed to characterize the plasma state in different
source regions, from active regions to quiet Sun to coronal holes. By
comparing composition, plasma parameters, and low/high FIP ratios of
structures remotely, with those measured directly at the Solar Orbiter
spacecraft, Solar Orbiter will provide the first direct link between
solar wind structures and their source regions at the Sun. This
talk will provide a background of previous compositional correlation
measurements and an outline of the method to be used for comparing
the spectroscopic and in-situ plasma parameters to be measured with
Solar Orbiter.

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Title: Slitless Solar Spectroscopy
Authors: Davila, Joseph M.
2011SPD....42.1520D Altcode: 2011BAAS..43S.1520D
Spectrographs have traditionally suffered from the inability to
obtain line intensities, widths, and Doppler shifts over large spatial
regions of the Sun quickly because of the narrow instantaneous field
of view. This has limited the spectroscopic analysis of rapidly
varying solar features like, flares, CME eruptions, coronal jets,
and reconnection regions. Imagers have provided high time resolution
images of the full Sun with limited spectral resolution. In this
paper we present recent advances in deconvolving spectrally dispersed
images obtained through broad slits. We use this new theoretical
formulation to examine the effectiveness of various potential observing
scenarios, spatial and spectral resolutions, signal to noise ratio,
and other instrument characteristics. This information will lay
the foundation for a new generation of spectral imagers optimized for
slitless spectral operation, while retaining the ability to obtain
spectral information in transient solar events.

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Title: Modeling Waves And Flows In Active Region Loops
Authors: Ofman, Leon; Wang, T.; Davila, J. M.
2011SPD....42.1815O Altcode: 2011BAAS..43S.1815O
Recent Hinode/EIS observations indicated that slow magnetosonic
waves are present in active region loops. Some of the spectral data
were also interpreted as evidence of quasi-periodic flows. We perform
three dimensional MHD model of an active region with waves and flows in
coronal loops. The model is initiated with a dipole magnetic field and
gravitationally stratified density, and velocity pulses are driven
periodically in localized regions at the footpoints of magnetic
loops. The resulting flows produce higher density loops compared to
the surrounding plasma by injecting material along the field. We find
that the excitation of periodic flows with subsonic speeds result in
the excitation of slow magnetosonic waves that propagate along the
loops. The phase speed of the waves is 100 km/s, close to coronal sound
speed. When the amplitude of the driving pulses is increased we find
that slow shock trains are produced. Using the results of the 3D MHD
model we suggest that the observed slow magnetosonic waves and quasi
periodic-flows are driven by the same quasi-periodic impulsive events
at the bases of active regions.

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Title: New Capabilities of the EUNIS Sounding Rocket Instrument
Authors: Daw, Adrian N.; Brosius, J.; Criscuolo, E.; Davila, J.;
Haas, J. P.; Hilton, G.; Linard, D.; Plummer, T.; Rabin, D.; Thomas,
R.; Varney, D.; Wang, T.
2011SPD....42.1502D Altcode: 2011BAAS..43S.1502D
The upcoming flight of the Extreme Ultraviolet Normal Incidence
Spectrograph (EUNIS) sounding rocket instrument, a two-channel imaging
spectrograph that observes the solar corona and transition region
with high spectral resolution and a rapid cadence made possible by
unprecedented sensitivity, will incorporate a new wavelength channel
and cooling of the active pixel sensor (APS) arrays. The new 52.4-63.0
nm channel incorporates a Toroidal Varied Line Space (TVLS) grating
coated with B4C/Ir, providing broad spectral coverage and
a wide temperature range of 0.025 to 10 MK. The APS arrays for both
the 52-63 nm and 30-37 nm channels will be cooled to -20 C to reduce
dark current noise. With the resulting read-noise limited performance,
over a dozen new diagnostic line pairs become available in the two
wavelength channels. To our knowledge, this will be the first flight
demonstration of cooled APS arrays. EUNIS will co-observe dynamic
coronal phenomena with SDO/AIA and Hinode/EIS and will contribute to
the absolute radiometric calibrations of these instruments. EUNIS
is supported by NASA through the Low Cost Access to Space Program in
Solar and Heliospheric Physics.

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Title: Slow-Mode Oscillations of Hot Coronal Loops Excited at
Flaring Footpoints
Authors: Wang, Tongjiang; Liu, W.; Ofman, L.; Davila, J. M.
2011SPD....42.2214W Altcode: 2011BAAS..43S.2214W
A large number of strongly damped oscillations in hot coronal loops
have been observed by SOHO/SUMER in the past decade in Doppler shifts
of flaring (&gt;6 MK) lines (Fe XIX and Fe XXI). These oscillations
with periods on the order of 10-30 min were interpreted as fundamental
standing slow modes. They often manifest features such as recurrence
and association with a flow (100-300 km/s) pulse preceding to the
oscillation, which suggests that they are likely driven by microflares
at the footpoints. With coordinated RHESSI observations, we have found
a dozen such events supporting this conjecture. A typical event is
presetned here. By analyzing RHESSI hard X-ray and GOES/SXI soft
X-ray emissions as well as SUMER Doppler shifts, we identify the
flare that triggers the loop oscillations. From RHESSI spectra, we
measure physical parameters such as temperature, emission measure,
and thermal/non-thermal energy contents as functions of time. We
discuss the wave excitation mechanism based on these observations. Our
results provide important observational constraints that can be used
for improving theoretical models of magnetosonic wave excitation,
and for coronal seismology.

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Title: Earth-Affecting Solar Causes Observatory (EASCO): A potential
International Living with a Star Mission from Sun-Earth L5
Authors: Gopalswamy, N.; Davila, J. M.; St. Cyr, O. C.; Sittler,
E. C.; Auchère, F.; Duvall, T. L.; Hoeksema, J. T.; Maksimovic, M.;
MacDowall, R. J.; Szabo, A.; Collier, M. R.
2011JASTP..73..658G Altcode:
This paper describes the scientific rationale for an L5 mission
and a partial list of key scientific instruments the mission should
carry. The L5 vantage point provides an unprecedented view of the
solar disturbances and their solar sources that can greatly advance
the science behind space weather. A coronagraph and a heliospheric
imager at L5 will be able to view CMEs broadsided, so space speed
of the Earth-directed CMEs can be measured accurately and their
radial structure discerned. In addition, an inner coronal imager
and a magnetograph from L5 can give advance information on active
regions and coronal holes that will soon rotate on to the solar
disk. Radio remote sensing at low frequencies can provide information
on shock-driving CMEs, the most dangerous of all CMEs. Coordinated
helioseismic measurements from the Sun-Earth line and L5 provide
information on the physical conditions at the base of the convection
zone, where solar magnetism originates. Finally, in situ measurements
at L5 can provide information on the large-scale solar wind structures
(corotating interaction regions (CIRs)) heading towards Earth that
potentially result in adverse space weather.

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Title: The International Space Weather Initiative (ISWI)
Authors: Davila, Joseph M.; Gopalswamy, Nat; Thompson, Barbara J.;
Bogdan, Tom; Hapgood, Mike
2011sswh.book..375D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Tracking the Topology of the Photospheric Magnetic Network
in Multiscale Space-time: Towards New Precursors of Transient
Coronal Events
Authors: Coyner, A. J.; Uritsky, V. M.; Davila, J. M.
2010AGUFMSH43B1823C Altcode:
We present a new approach to exploring magnetic flux dynamics in
the solar photosphere as depicted by high-resolution spacecraft
observations, and provide statistical evidence for the correlated
cancellation behavior of bipolar magnetic structures over a range
of scales associated with meso- and supergranulation suggesting the
involvement of these unstable structures in the coronal heating and
flaring activity. Our methodology is based on spatio-temporal tracking
of magnetic elements allowing us to rigorously identify timing and
positions of magnetic emergence and submergence events. The causal
relationship between these events is investigated further using the
cross-correlation integral algorithm (Uritsky et al., 2010). We apply
this two-step approach to an extensive set of SOHO MDI and Hinode
SOT V/I magnetograms exhibiting various types of unipolar and bipolar
magnetic structures observed in active and quiet regions of the solar
photosphere. The results show a significant difference in the behavior
of unipolar and bipolar magnetic elements, confirming previously
found asymmetry in the emergence and cancellation dynamics of the
photospheric magnetic flux. Our analysis also reveals characteristic
spatial scales of mesogranular structures of the same and opposing
magnetic polarity. Finally, we identify a distinct subset of positively
correlated submergence events detected under active photospheric
conditions. We argue that these events may represent the reconnection
dynamics of the closed magnetic flux, and therefore be responsible
for the local coronal dissipation. This possibility is tested using
conjugate sets of STEREO EUVI and SOHO MDI images.

---------------------------------------------------------
Title: International Space Weather Initiative (ISWI)
Authors: Gopalswamy, N.; Davila, J. M.
2010nspm.conf..160G Altcode:
The International Space Weather Initiative (ISWI) is an international
scientific program to understand the external drivers of space
weather. The science and applications of space weather has been
brought to prominence because of the rapid development of space based
technology that is useful for all human beings. The ISWI program has
its roots in the successful International Heliophysical Year (IHY)
program that ran during 2007 - 2009. The primary objective of the ISWI
program is to advance the science space weather by a combination of
instrument deployment, analysis and interpretation of space weather
data from the instruments deployed in conjunction with space data,
and communicate the results to the public and students. Like the IHY,
the ISWI will be a grass roots organization with key participation
from national coordinators with cooperation in an international
steering committee. This talk outlines the ISWI program including its
organization and proposed activities.

---------------------------------------------------------
Title: Opportunities for Ionospheric Science as Part of the
International Space Weather Initiative (ISWI) (Invited)
Authors: Davila, J. M.; Gopalswamy, N.; Haubold, H.
2010AGUFMSA43C..01D Altcode:
The International Heliophysical Year (IHY), which lasted for
approximately two years and involved the effort of thousands of
scientists from over 70 countries, ended in February 2009. The
major objectives of the IHY included over 60 collaborative studies
of universal physical processes in the solar system, the deployment
of arrays of small instruments to observe heliophysical processes, a
unique program of educational and public outreach, and the preservation
of the history of the IGY. The International Space Weather Initiative
(ISWI), an international effort fully supported by the United Nations,
is designed to build on the momentum developed during the IHY to
develop the capability to observe, understand, and predict space
weather phenomena, and provide the opportunity for the deployment
of new instrumentation in Africa and other regions. In this talk the
basic elements of the ISWI will be discussed, and the opportunities
for the deployment of new instrument will be discussed.

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Title: Connecting CME expansion from Sun to 1 AU
Authors: Nieves-Chinchilla, T.; Colaninno, R. C.; Vourlidas, A.;
Szabo, A.; Vinas, A. F.; Davila, J. M.
2010AGUFMSH23B1841N Altcode:
EUV disk imagers and white light coronagraphs have provided for many
years information on the early formation and evolution of coronal
mass ejections (CMEs). More recently, the novel heliospheric imaging
instruments aboard the STEREO mission are providing crucial remote
sensing information on the interplanetary evolution of these events
while in situ instruments complete the overall characterization of the
interplanetary CMEs. In this work, we present an analysis of CMEs from
the Sun to the interplanetary medium using combined data from SDO, SOHO,
STEREO, WIND, and ACE spacecraft. From the remote sensing analysis,
the most notable feature of a CME observed in the SECCHI suite of
instruments field of view is its elliptic cross section. However, most
of the models for in situ modeling impose the circular cross-section
geometry. In this work, we link the remote sensing observations with
the in situ data through an analytical in situ model which incorporates
the distortion in the cross-section. In this study, different aspects
such as the ambient solar wind, magnetic field configurations, plasma
parameters, etc, have been taken into account in order to cover the
widest spectrum of possible scenarios.

---------------------------------------------------------
Title: The Future of IHY Campaigns: Transition to the International
Space Weather Initiative
Authors: Raulin, Jean-Pierre; Davila, Joseph M.; Bogdan, Thomas;
Yumoto, Kiyohumi; Leibacher, John
2010HiA....15..501R Altcode:
We will present the relevant activities performed during the
International Heliophysical Year (IHY) program during the 5 year
period 2004 - 2008. The IHY was a major international effort that
involved the deployment of new instrumentation, new observations from
the ground and in space, and a strong education component. Under the
United Nations Office for Outer Space program called Basic Space
Science Initiative (UNBSSI), instrument arrays have been deployed
to provide global measurements of heliophysical phenomena. As
a result, significant scientific and educational collaborations
emerged between the organizing groups and the host country teams. In
view of the great successes achieved by the IHY during these years,
we propose to continue the highly successful collaboration with the
UN program to study the universal processes in the solar system
that affect the interplanetary and terrestrial environments, and
to continue to coordinate the deployment and operation of new and
existing instrumentation arrays aimed at understanding the impacts of
Space Weather on Earth and the near-Earth environment. To this end,
we propose a new program, the International Space Weather Initiative
(ISWI). The ISWI strongly complements the International Living With a
Star (ILWS) program, providing more attention nationally, regionally,
and internationally for the ILWS program. Based on a three-year program
activity, the ISWI would provide the opportunity for scientists around
the world to participate in this exciting quest to understand the
effect of space disturbances on our Earth environment.

---------------------------------------------------------
Title: Multi-day Precursors to Prominence Eruptions
Authors: Kilper, Gary; Davila, Joseph
2010shin.confE.103K Altcode:
Prominence eruptions are highly correlated to CMEs, and a better
understanding of them would enhance the ability to forecast hazardous
space weather. Increases in absorption, strong flows, cavity expansion,
low-level heating, and photospheric flux cancellation have all been
found prior to eruptions. Our recent research has analyzed most of
these properties simultaneously and found that they are related, and
they collectively start a day or more prior to eruption onset. These
findings can be used to predict extended windows in which a prominence
eruption is unlikely to occur.

---------------------------------------------------------
Title: Towards a New Formation Flying Solar Coronagraph
Authors: Lamy, P.; Vives, S.; Curdt, W.; Dame, L.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Kuzin, S.; Schmutz, W.; Tsinganos,
K.; Turck-Chieze, S.; Zhukov, A.
2010ASPC..424...15L Altcode:
We briefly describe an investigation aiming at the development of a
giant solar coronagraph instrument onboard of two satellites, separated
by about 150 m in formation flight for the detailed observation of the
solar coronal plasma. The European Space Agency (ESA) has selected this
instrument as the only payload onboard the Proba 3 satellites which
will be launched in 2013. The Greek team is developing the command
control board of the coronagraph.

---------------------------------------------------------
Title: A Complete Observational Picture of Quiet Sun Prominence
Eruptions
Authors: Kilper, Gary; Davila, J.
2010AAS...21640302K Altcode: 2010BAAS...41..878K
A relation between prominence eruptions and coronal mass ejections
is well established, and several possible eruption models have been
formulated. However, the observational side had lacked the necessary
statistical studies to permit any decisive conclusions. Recently,
large databases of observations have allowed detailed and thorough
analyses of the prominence plasma, surrounding cavity, and the
magnetic field below. This presentation will highlight these recent
results, and describe findings from our new study, which combines
simultaneous observations from MLSO, SOHO-MDI and EIT, STEREO-EUVI,
and Hinode-XRT. This research was supported by an appointment to the
NASA Postdoctoral Program at Goddard Space Flight Center, which is
administered by Oak Ridge Associated Universities through a contract
with NASA.

---------------------------------------------------------
Title: Absolute Radiometric Calibration Of EUNIS, And Calibration
Updates For Hinode/EIS And SOHO/CDS
Authors: Wang, Tongjiang; Thomas, R. J.; Brosius, J. W.; Young, P. R.;
Rabin, D. M.; Davila, J. M.
2010AAS...21640704W Altcode: 2010BAAS...41..860W
The Extreme-Ultraviolet Normal-Incidence Spectrograph sounding rocket
payload was flown in 2006 (EUNIS-06) and 2007 (EUNIS-07), each time
carrying two independent imaging spectrographs covering wave bands
of 300-370 Angstrom in first order and 170-205 Angstrom in second
order. For each flight, the absolute radiometric response of the EUNIS
long-wavelength (LW) channel was directly measured in the same facility
used for pre-flight calibrations of SOHO/CDS and Hinode/EIS. The
wavelength range of the EUNIS LW channel overlaps that of CDS/NIS-1,
and so can provide a direct calibration update for it. The EUNIS-06
observation shows that the efficiency of CDS/NIS-1 has decreased by
a factor about 1.7 compared to that of the previously implemented
calibration. Here we present an update to the absolute calibration for
Hinode/EIS derived with a technique that combines a direct comparison
of line intensities observed in cospatial EUNIS-07 and EIS spectra,
along with density- and temperature-insensitive line intensity ratios.

---------------------------------------------------------
Title: On the Vector Tomographic Reconstruction for the pre-CME
Coronal Magnetic Field from Fe XIII 10747 A Emission Line Observations
Authors: Kramar, Maxim; Lin, H.; Inhester, B.; Davila, J.
2010AAS...21630203K Altcode:
Magnetic fields are the dominant fields that determine the static and
dynamic properties of the solar corona. The coronal mass ejections
(CMEs) involve the release of the magnetic energy stored in the
magnetic field. Therefore, analyzing the magnetic field could help
to understand the nature of CMEs. One of the more promising coronal
magnetic field measurement methods that have been successfully
demonstrated is the spectropolarimetric observations of the Fe XIII
10747 A forbidden emission line (Lin, Penn &amp; Tomczyk 2000; Lin, Kuhn
&amp; Coulter 2004; Tomczyk et al. 2007) formed due to Hanle and Zeeman
effects. However, these measurements are integrated over line-of-sight
(LOS). Therefore it is impossible to determine the configuration of
the coronal magnetic field from a single observation (single viewing
direction). Vector tomography based on polarimetric observations
of the forbidden coronal emission lines can reconstruct the coronal
magnetic field when the observations are obtained from several viewing
directions. As the tomography method requires observations from many
directions, a rigid rotation of the coronal structures during a half of
solar rotation is assumed. However, many pre-CME magnetic configurations
evolve more rapidly causing significant reduce in the number of
available observing directions. Here we study the sensitivity of the
vector tomographic inversion to possible pre-CME coronal magnetic field
configurations and the number of available observing directions. We
show that the vector tomography techniques has the potential to resolve
the 3D coronal non-potential magnetic field structure.

---------------------------------------------------------
Title: The 3D Coronal Electron Density Based on STEREO/COR1
Observations for the Year of 2008
Authors: Kramar, Maxim; Davila, J.; Xie, H.; Lamb, D.; Inhester, B.
2010AAS...21640501K Altcode: 2010BAAS...41..889K
We present a three dimensional reconstructions of the electron density
in the corona at the distances from 1.5 to 4 R⊙ for the
whole year of 2008, i.e. during solar minimum. The reconstructions is
based on STEREO/COR1 data and performed using a regularized tomography
inversion method. The reconstructed streamer belt structure
is generally consistent with the neutral magnetic line derived
from a potential field extrapolation method (PFSS) for the most of
the time. However for some pre-CME events this consistency is less
clear. This inconsistency could indicates the non-potentiality of the
pre-CME magnetic field configuration. Also it is seen a significant
density decrease in the streamer belt after some CME events. This
clearly indicates the streamer blow out effect. As we have 3D
reconstructed density, the streamer belt mass lost due to that CMEs
is estimated.

---------------------------------------------------------
Title: The June 1st 2008 CME in the Interplanetary Medium
Authors: Nieves-Chinchilla, T.; F. -Vinas, A.; Gomez-Herrero, R.;
Malandraki, O. E.; Dresing, N.; Hidalgo, M. A.; Davila, J.
2010EGUGA..1215133N Altcode:
In this work we present a combined study/analysis of the counterpart
of the CME of June 1st of 2008 in the interplanetary medium. This
event has been largely studied because of its peculiar initiation and
its possible forecasting consequences for space weather. We show an in
situ analysis of the CME in the interplanetary medium in order to shed
some light on the propagation and evolution mechanisms of the ICME. The
energetic particles play an important role in order to understand the
overall event, the source on the Sun and the effect over the Earth. The
typical shock associated characteristics with the counterpart of the
CMEs in the interplanetary medium has been determined, in order to
understand the propagation properties. The magnetic cloud has been
studied and analyzed using non force-free models as start point to
incorporate expansion. To accomplish this analysis the IMPACT/STEREO
B in-situ measurement have been considered in order to characterize
the Interplanetary CME.

---------------------------------------------------------
Title: Propagating Intensity Disturbances In Coronal Loops: Waves
Or Flows?
Authors: Wang, Tongjiang; Ofman, L.; Davila, J. M.
2010AAS...21640715W Altcode: 2010BAAS...41..862W
Quasi-periodic propagating intensity disturbances were found by
SOHO/EIT and TRACE imaging observations in fanlike coronal loops
10 year ago. The 3 min and 5 min oscillations have been interpreted
as propagating slow magnetoacoustic waves which originate from the
photospheric p-mode oscillations due to the wave leakage. However,
some cases show oscillations with periodicities of more than 10 min,
which are hard to explain by wave leakage, and so were argued in some
studies that they may be periodic flows. In this presentation, we report
the first observation of multiple-periodic (12 and 25 min) propagating
disturbances along a fan-like coronal structure simultaneously
detected in both intensity and Doppler shift in the Fe XII line with
EIS onboard Hinode. We measured Doppler shift amplitude of 1-2 km/s,
relative intensity amplitude of (3-5)% and the apparent propagation
speed of 100-120 km/s. The amplitude relationship between intensity
and Doppler shift oscillations provides convincing evidence that these
propagating features are a manifestation of slow magnetoacoustic waves
but not flows. The feature of symmetric line profiles also confirms
that the measured small Doppler-shift amplitudes are not due to the
line wing enhancement caused by high-speed flows. A new application
of coronal seismology is provided based on these observations, with
which we determine the inclination angle of the magnetic field and
the temperature of a coronal loop. We will also show the result of
multi-temperature line analysis to explore the temperature-dependent
behavior of this phenomenon.

---------------------------------------------------------
Title: Determination Of Non-thermal Velocity Distributions From
Spatially-averaged EUV Spectra Observed With SERTS And Hinode/EIS
Authors: Coyner, Aaron J.; Davila, J. M.
2010AAS...21640710C Altcode: 2010BAAS...41..861C
Unresolved non-thermal broadenings have been reported in observations
of solar EUV spectra for decades. These unresolved broadenings are
generally attributed to non-thermal motions within coronal plasma loops
and have been shown to provide a limitation on the maximum available
energy in the coronal plasma to facilitate coronal heating. Therefore,
determining an average non-thermal velocity component of the broadening
in observed EUV line profiles provides a significant observational
constraint for all coronal heating models to address. We have analyzed
spatially-averaged spectra from both the Solar EUV Research Telescope
and Spectrograph (SERTS) over the EUV bandpass from 170-420 angstroms
in a variety of solar conditions, from quiet sun to active region
to off-limb data. For each instrument, we construct a non-thermal
velocity, &lt;Vnth2&gt;, distributions for
active region and quiet sun emission lines respectively. We then fit
each distribution with a Gaussian to determine the typical unresolved
non-thermal velocities observed in both quiet sun and active region
distributions. Ideally, if no non-thermal component exists the
distributions would all peak at zero, but in the case of the SERTS
observations, we find the distributions peak at velocities between 21-25
km/s regardless of solar activity. Building off of the SERTS analysis,
we create similar distributions using spatially-averaged line profiles
from Hinode/EIS observations to use the increased spectral resolution
of EIS to refine the non-thermal velocity constraints determined
with SERTS.

---------------------------------------------------------
Title: Emission lines of FeXI in the 257-407Å wavelength region
observed in solar spectra from EIS/Hinode and SERTS
Authors: Keenan, F. P.; Milligan, R. O.; Jess, D. B.; Aggarwal, K. M.;
Mathioudakis, M.; Thomas, R. J.; Brosius, J. W.; Davila, J. M.
2010MNRAS.404.1617K Altcode: 2010MNRAS.tmp..299K; 2010arXiv1001.3627K
Theoretical emission-line ratios involving FeXI transitions in the
257-407Å wavelength range are derived using fully relativistic
calculations of radiative rates and electron impact excitation
cross-sections. These are subsequently compared with both long
wavelength channel Extreme-Ultraviolet Imaging Spectrometer (EIS)
spectra from the Hinode satellite (covering 245-291Å) and first-order
observations (~235-449Å) obtained by the Solar Extreme-ultraviolet
Research Telescope and Spectrograph (SERTS). The 266.39, 266.60 and
276.36Å lines of FeXI are detected in two EIS spectra, confirming
earlier identifications of these features, and 276.36Å is found to
provide an electron density (Ne) diagnostic when ratioed
against the 257.55Å transition. Agreement between theory and
observation is found to be generally good for the SERTS data sets,
with discrepancies normally being due to known line blends, while the
257.55Å feature is detected for the first time in SERTS spectra. The
most useful FeXI electron density diagnostic is found to be the
308.54/352.67 intensity ratio, which varies by a factor of 8.4 between
Ne = 108 and 1011cm-3,
while showing little temperature sensitivity. However, the
349.04/352.67 ratio potentially provides a superior diagnostic,
as it involves lines which are closer in wavelength, and varies
by a factor of 14.7 between Ne = 108 and
1011cm-3. Unfortunately, the 349.04Å line is
relatively weak, and also blended with the second-order FeX 174.52Å
feature, unless the first-order instrument response is enhanced.

---------------------------------------------------------
Title: Three-Dimensional Polarimetric Coronal Mass Ejection
Localization Tested Through Triangulation
Authors: Moran, Thomas G.; Davila, Joseph M.; Thompson, William T.
2010ApJ...712..453M Altcode:
We have tested the validity of the coronal mass ejection (CME)
polarimetric reconstruction technique for the first time using
triangulation and demonstrated that it can provide the angle and
distance of CMEs to the plane of the sky. In this study, we determined
the three-dimensional orientation of the CMEs that occurred on 2007
August 21 and 2007 December 31 using polarimetric observations obtained
simultaneously with the Solar Terrestrial Relations Observatory/Sun
Earth Connection Coronal and Heliospheric Investigation spacecraft
COR1-A and COR1-B coronagraphs. We obtained the CME orientations using
both the triangulation and polarimetric techniques and found that angles
to the sky plane yielded by the two methods agree to within ≈ 5°,
validating the polarimetric reconstruction technique used to analyze
CMEs observed with the Solar and Heliospheric Observatory/Large Angle
Spectrometric Coronagraph. In addition, we located the CME source
regions using EUV and magnetic field measurements and found that the
corresponding mean angles to the sky plane of those regions agreed
with those yielded by the geometric and polarimetric methods within
uncertainties. Furthermore, we compared the locations provided by
polarimetric COR1 analysis with those determined from other analyses
using COR2 observations combined with geometric techniques and
forward modeling. We found good agreement with those studies relying
on geometric techniques but obtained results contradictory to those
provided by forward modeling.

---------------------------------------------------------
Title: Background Subtraction for the SECCHI/COR1 Telescope Aboard
STEREO
Authors: Thompson, W. T.; Wei, K.; Burkepile, J. T.; Davila, J. M.;
St. Cyr, O. C.
2010SoPh..262..213T Altcode: 2010SoPh..tmp...26T
COR1 is an internally occulted Lyot coronagraph, part of the Sun Earth
Connection Coronal and Heliospheric Investigation (SECCHI) instrument
suite aboard the twin Solar Terrestrial Relations Observatory (STEREO)
spacecraft. Because the front objective lens is subjected to a full
solar flux, the images are dominated by instrumental scattered light
which has to be removed to uncover the underlying K corona data. We
describe a procedure for removing the instrumental background from
COR1 images. F coronal emission is subtracted at the same time. The
resulting images are compared with simultaneous data from the Mauna
Loa Solar Observatory Mk4 coronagraph. We find that the background
subtraction technique is successful in coronal streamers, while
the baseline emission in coronal holes (i.e. between plumes) is
suppressed. This is an expected behavior of the background subtraction
technique. The COR1 radiometric calibration is found to be either 10 -
15% lower, or 5 - 10% higher than that of the Mk4, depending on what
value is used for the Mk4 plate scale, while an earlier study found
the COR1 radiometric response to be ∼ 20% higher than that of the
Large Angle Spectroscopic Coronagraph (LASCO) C2 telescope. Thus,
the COR1 calibration is solidly within the range of other operating
coronagraphs. The background levels in both COR1 telescopes have been
quite steady in time, with the exception of a single contamination
event on 30 January 2009. Barring too many additional events of this
kind, there is every reason to believe that both COR1 telescopes will
maintain usable levels of scattered light for the remainder of the
STEREO mission.

---------------------------------------------------------
Title: Absolute Radiometric Calibration of the EUNIS-06 170-205
Å Channel and Calibration Update for Coronal Diagnostic
Spectrometer/Normal-Incidence Spectrometer
Authors: Wang, Tongjiang; Brosius, Jeffrey W.; Thomas, Roger J.;
Rabin, Douglas M.; Davila, Joseph M.
2010ApJS..186..222W Altcode: 2009arXiv0912.2328W
The Extreme-Ultraviolet Normal-Incidence Spectrograph sounding-rocket
payload was flown on 2006 April 12 (EUNIS-06), carrying two independent
imaging spectrographs covering wavebands of 300-370 Å in first order
and 170-205 Å in second order, respectively. The absolute radiometric
response of the EUNIS-06 long-wavelength (LW) channel was directly
measured in the same facility used to calibrate Coronal Diagnostic
Spectrometer (CDS) prior to the Solar and Heliospheric Observatory
(SOHO) launch. Because the absolute calibration of the short-wavelength
(SW) channel could not be obtained from the same lab configuration,
we here present a technique to derive it using a combination of solar
LW spectra and density- and temperature-insensitive line intensity
ratios. The first step in this procedure is to use the coordinated,
cospatial EUNIS and SOHO/CDS spectra to carry out an intensity
calibration update for the CDS NIS-1 waveband, which shows that its
efficiency has decreased by a factor about 1.7 compared to that of the
previously implemented calibration. Then, theoretical insensitive line
ratios obtained from CHIANTI allow us to determine absolute intensities
of emission lines within the EUNIS SW bandpass from those of cospatial
CDS/NIS-1 spectra after the EUNIS LW calibration correction. A total
of 12 ratios derived from intensities of 5 CDS and 12 SW emission
lines from Fe X to Fe XIII yield an instrumental response curve for
the EUNIS-06 SW channel that matches well to a relative calibration
which relied on combining measurements of individual optical
components. Taking into account all potential sources of error, we
estimate that the EUNIS-06 SW absolute calibration is accurate to ±20%.

---------------------------------------------------------
Title: Propagating intensity disturbances in coronal loops: Waves
or flows?
Authors: Wang, Tongjiang; Ofman, Leon; Davila, Joseph
2010cosp...38.2924W Altcode: 2010cosp.meet.2924W
Quasi-periodic propagating intensity disturbances were found by
SOHO/EIT and TRACE imaging observations in fanlike coronal loops
10 year ago. The 3 min and 5 min oscillations have been interpreted
as propagating slow magnetoacoustic waves which originate from the
photospheric p-mode oscillations due to the wave leakage. However,
some cases show oscil-lations with periodicities of more than 10 min,
which are hard to explain by wave leakage, and so were argued in
some studies that they may be periodic flows. In this presentation,
we report the first observation of multiple-periodic (12 and 25
min) propagating disturbances along a fan-like coronal structure
simultaneously detected in both intensity and Doppler shift in
the Fe xii line with EIS onboard Hinode. We measured Doppler shift
amplitude of 1-2 km/s, relative intensity amplitude of (3-5)% and the
apparent propagation speed of 100-120 km/s. The amplitude relationship
between intensity and Doppler shift oscillations provides convinc-ing
evidence that these propagating features are a manifestation of slow
magnetoacoustic waves but not flows. The feature of symmetric line
profiles also confirms that the measured small Doppler-shift amplitudes
are not due to the line wing enhancement caused by high-speed flows. A
new application of coronal seismology is provided based on these
observations, with which we determine the inclination angle of the
magnetic field and the temperature of a coronal loop. We will also show
the result of multi-temperature spectral line analysis to explore the
temperature-dependent behavior of this phenomenon.

---------------------------------------------------------
Title: ASPIICS / PROBA-3: a formation flying externally-occulted
giant coronagraph mission
Authors: Lamy, Philippe; Damé, Luc; Curdt, W.; Davila, J.; Defise,
J. M.; Fineschi, S.; Heinzel, P.; Howard, R.; Kuzin, S.; Schmutz,
W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.2858L Altcode: 2010cosp.meet.2858L
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are detailed.

---------------------------------------------------------
Title: Estimation of coronal magnetic field using the type II radio
burst associated with a fast CME
Authors: Gopalswamy, Nat; Yashiro, Seiji; Akiyama, Sachiko; Freeland,
Samuel; Davila, Joseph; Howard, Russell; Bougeret, J. -L.
2010cosp...38.1808G Altcode: 2010cosp.meet.1808G
The 2008 March 25 coronal mass ejection (CME) was the second
fastest among the 10 type II producing CMEs in the STEREO era. The
CME was accompanied by a EUV wave and a shock discernible in the
white-light data. The type II burst was observed in the metric and
decameter-hectometer (DH) wavelength domains. The type II burst ended in
the DH domain when the CME speed started declining at a heliocentric
distance where the Alfven speed reached its peak value. Under the
scenario that the type II burst was caused by a CME-driven shock,
we see that the end of the type II burst corresponds to a significant
weakening of the shock, making it subcritical. The standoff distance
between the flux rope structure and the shock significantly increased at
the time of the shock weakening. From the observed standoff distance,
we estimated the upstream Alfvenic Mach number and hence the coronal
magnetic field. The magnetic field derived (0.04 G) is consistent with
typical quiet solar atmosphere at 7 solar radii.

---------------------------------------------------------
Title: Multi-spacecraft observation of a magnetic cloud
Authors: de Lucas, Aline; Dal Lago, Alisson; Schwenn, Rainer; Clúa de
Gonzalez, Alicia L.; Marsch, Eckart; Lamy, Philippe; Damé, Luc; Curdt,
W.; Davila, J.; Defise, J. M.; Fineschi, S.; Heinzel, P.; Howard, R.;
Kuzin, S.; Schmutz, W.; Tsinganos, K.; Turck-Chièze, S.; Zhukov, A.
2010cosp...38.1921D Altcode: 2010cosp.meet.1921D
Classical externally-occulted coronagraphs are presently limited in
their performances by the distance between the external occulter and
the front objective. The diffraction fringe from the occulter and
the vignetted pupil which degrades the spatial resolution prevent
useful observa-tions of the white light corona inside typically 2-2.5
Rsun. Formation flying offers an elegant solution to these limitations
and allows conceiving giant, externally-occulted coronagraphs
us-ing a two-component space system with the external occulter on
one spacecraft and the optical instrument on the other spacecraft
at distances of hundred meters. Such an instrument has just been
selected by ESA to fly (by the end of 2013) on its PROBA-3 mission,
presently in phase B, to demonstrate formation flying. It will perform
both high spatial resolution imaging of the solar corona as well as
2-dimensional spectroscopy of several emission lines (in partic-ular
the forbidden line of FeXIV at 530.285 nm) from the coronal base out
to 3 Rsun using a Fabry-Perot interferometer. The classical design of
an externally-occulted coronagraph is adapted to the formation flying
configuration allowing the detection of the very inner corona as close
as 0.05 Rsun from the solar limb. By tuning the position of the occulter
spacecraft, it may even be possible to try reaching the chromosphere
and the upper part of the spicules. ASPIICS/PROBA-3 mission, payload
and scientific objectives are presented.

---------------------------------------------------------
Title: Vector tomographic reconstruction for the coronal magnetic
field from Fe XIII 10747 A emission line observations
Authors: Kramar, Maxim; Lin, Haosheng; Inhester, Bernd; Davila, Joseph
2010cosp...38.1862K Altcode: 2010cosp.meet.1862K
Magnetic fields in the solar corona are the dominant fields that
determine the static and dy-namic properties of this outermost region
of the solar atmosphere. It is within this tenuous region that the
magnetic force dominates the gas pressure. Direct measurement of
the coronal magnetic field is one of the most challenging problems
in observational solar astronomy. To date, one of the promising
measurement methods that have been successfully demonstrated is
the spectropolarimetric measurement of the Fe XIII 10747 A forbidden
emission line (Lin, Penn Tomczyk 2000; Lin, Kuhn Coulter 2004; Tomczyk
et al. 2007) formed due to Hanle and Zeeman effects. However, because
coronal measurements are integrated over line-of-site (LOS), it is
impossible to derive the configuration of the coronal magnetic field
from a single obser-vation (from a single viewing direction). In this
paper, we study the sensitivity of the vector tomographic inversion to
possible pre-CME coronal magnetic field configurations and number of
available observations. We show that the vector tomography techniques
based on Hanle and/or Zeeman effect observations has the potential to
resolve the 3D coronal non-potential magnetic field structure.

---------------------------------------------------------
Title: The 3D reconstructions of the coronal electron density in
the range 1.5-4 Rsun for the whole year of 2008
Authors: Kramar, Maxim; Davila, Joseph; Lamb, Derek; Xie, Hong
2010cosp...38.1920K Altcode: 2010cosp.meet.1920K
We present a three dimensional reconstructions of the electron
density in the corona at the distances from 1.5 to 4R for the whole
year of 2008, i.e. during solar minimum. The recon-structions is
based on STEREO/COR1 data and performed using a regularized tomography
inversion method. The reconstructed streamer belt structure is generally
consistent with the neutral magnetic line derived from a potential
field extrapolation method (PFSS) for the most of the time. However for
some pre-CME events this consistency is less clear. This inconsistency
could indicates the non-potentiality of the pre-CME magnetic field
configuration. Also it is seen a significant density decrease in
the streamer belt after some CME events. This clearly indicates the
streamer blow out effect. As we have 3D reconstructed density, the
streamer belt mass lost due to that CMEs is estimated.

---------------------------------------------------------
Title: The International Space Weather Initiative
Authors: Davila, Joseph; Gopalswamy, Nat
2010cosp...38.4192D Altcode: 2010cosp.meet.4192D
The International Space Weather Initiative (ISWI) is an international
program of scientific collaboration to understand the external drivers
of space weather. One of the major thrusts of the ISWI is to deploy
arrays of small instruments such as magnetometers, radio antennas, GPS
receivers, all-sky cameras, particle detectors, etc. around the world to
provide global measurements of heliospheric phenomena. Scientists from
approximately 70 countries now participate in the instrument operation,
data collection, analysis, and publication of scientific results,
working at the forefront of science research. The purpose of the ISWI is
to continue the scientific study of universal processes in the solar
system that affect space weather and the terrestrial environment,
and to continue to coordinate the deployment and operation of new and
existing instrument arrays aimed at understanding the impacts of Space
Weather on Earth and the near-Earth environment. This project provides
an excellent opportunity for potential instrument providers to engage
collaborators from specific geographical locations, and to broaden
the coverage of existing instrument arrays. By deploying instruments
in strategically chosen locations new science and a more global view
of heliophysical processes is obtained. These data will also provide
new inputs for global ionospheric models in the future.

---------------------------------------------------------
Title: On the 3-D reconstruction of Coronal Mass Ejections using
coronagraph data
Authors: Mierla, M.; Inhester, B.; Antunes, A.; Boursier, Y.; Byrne,
J. P.; Colaninno, R.; Davila, J.; de Koning, C. A.; Gallagher, P. T.;
Gissot, S.; Howard, R. A.; Howard, T. A.; Kramar, M.; Lamy, P.;
Liewer, P. C.; Maloney, S.; Marqué, C.; McAteer, R. T. J.; Moran, T.;
Rodriguez, L.; Srivastava, N.; St. Cyr, O. C.; Stenborg, G.; Temmer,
M.; Thernisien, A.; Vourlidas, A.; West, M. J.; Wood, B. E.; Zhukov,
A. N.
2010AnGeo..28..203M Altcode:
Coronal Mass ejections (CMEs) are enormous eruptions of magnetized
plasma expelled from the Sun into the interplanetary space, over the
course of hours to days. They can create major disturbances in the
interplanetary medium and trigger severe magnetic storms when they
collide with the Earth's magnetosphere. It is important to know their
real speed, propagation direction and 3-D configuration in order to
accurately predict their arrival time at the Earth. Using data from
the SECCHI coronagraphs onboard the STEREO mission, which was launched
in October 2006, we can infer the propagation direction and the 3-D
structure of such events. In this review, we first describe different
techniques that were used to model the 3-D configuration of CMEs in
the coronagraph field of view (up to 15 R⊙). Then, we apply these
techniques to different CMEs observed by various coronagraphs. A
comparison of results obtained from the application of different
reconstruction algorithms is presented and discussed.

---------------------------------------------------------
Title: Hinode/EIS Observations of Propagating Slow Magnetoacoustic
Waves in a Coronal Loop
Authors: Wang, T. J.; Ofman, L.; Davila, J. M.
2009ASPC..415...28W Altcode:
We present the first Hinode/EIS observations of 5 min quasi-periodic
oscillations detected in the transition region and corona at the
footpoint of a coronal loop. The oscillations are characterized by a
series of wave packets with nearly constant period, typically persisting
for 4--6 cycles. There is an in-phase relation between Doppler shift
and intensity oscillations, indicating upwardly propagating slow
magnetoacoustic waves in the loop. We find that the oscillations
detected in the five coronal lines are highly correlated, and the
amplitude decreases with increasing temperature. These oscillations
may be caused by the leakage of the photospheric p-modes through the
chromosphere and transition region into the corona, which has been
suggested as the source for intensity oscillations previously observed
by TRACE. The temperature dependence of the oscillation amplitudes
can be explained by damping of the waves traveling along the loop with
multithread structure near the footpoint.

---------------------------------------------------------
Title: Recent STEREO Observations of Coronal Mass Ejections
Authors: St Cyr, O. C.; Xie, H.; Mays, M. L.; Davila, J. M.; Gilbert,
H. R.; Jones, S. I.; Pesnell, W. D.; Gopalswamy, N.; Gurman, J. B.;
Yashiro, S.; Wuelser, J.; Howard, R. A.; Thompson, B. J.; Thompson,
W. T.
2009AGUFMSH11A1491S Altcode:
Over 400 CMEs have been observed by STEREO SECCHI COR1 during
the mission's three year duration (2006-2009). Many of the solar
activity indicators have been at minimal values over this period,
and the Carrington rotation-averaged CME rate has been comparable to
that measured during the minima between Cycle 21-22 (SMM C/P) and
Cycle 22-23 (SOHO LASCO). That rate is about 0.5 CMEs/day. During
the current solar minimum (leading to Cycle 24), there have been
entire Carrington rotations where no sunspots were detected and the
daily values of the 2800 MHz solar flux remained below 70 sfu. CMEs
continued to be detected during these exceptionally quiet periods,
indicating that active regions are not necessary to the generation of
at least a portion of the CME population. In the past, researchers were
limited to a single view of the Sun and could conclude that activity
on the unseen portion of the disk might be associated with CMEs. But
as the STEREO mission has progressed we have been able to observe an
increasing fraction of the Sun's corona with STEREO SECCHI EUVI and
were able to eliminate this possibility. Here we report on the nature
of CMEs detected during these exceptionally-quiet periods, and we
speculate on how the corona remains dynamic during such conditions.

---------------------------------------------------------
Title: Electron-Temperature Maps of the Low Solar Corona: ISCORE
Results from the Total Solar Eclipse of 29 March 2006 in Libya
Authors: Reginald, Nelson L.; St. Cyr, O. C.; Davila, Joseph M.;
Rabin, Douglas M.; Guhathakurta, Madhulika; Hassler, Donald M.
2009SoPh..260..347R Altcode:
We conducted an experiment in conjunction with the total solar
eclipse of 29 March 2006 in Libya that measured the coronal
intensity through two filters centered at 3850 Å and 4100 Å with
bandwidths of ≈ 40 Å. The purpose of these measurements was to
obtain the intensity ratio through these two filters to determine
the electron temperature. The instrument, Imaging Spectrograph of
Coronal Electrons (ISCORE), consisted of an eight inch, f/10 Schmidt
Cassegrain telescope with a thermoelectrically-cooled CCD camera at
the focal plane. Results show electron temperatures of 105
K close to the limb to 3×106 K at 1.3R⊙. We
describe this novel technique, and we compare our results to other
relevant measurements. This technique could be easily implemented on
a space-based platform using a coronagraph to produce global maps of
the electron temperature of the solar corona.

---------------------------------------------------------
Title: Coronal Rotation Between 1.5 and 3.5 Solar Radii at Solar
Minimum
Authors: Jones, S. I.; Davila, J. M.
2009AGUFMSH41B1655J Altcode:
Here we report on coronal rotation measurements using STEREO
COR1. Multiple studies have confirmed that rotation rates in the outer
corona differ markedly from those of the photosphere, where a steady
decline in rotation rate with latitude is observed. Emission line
observations of low-lying coronal magnetic features typically correspond
well with photospheric rotation rates, while white-light measurements
in the upper corona indicate very rigid rotation. Some studies have
reported a sudden jump in the rotation rate in the 2.3-2.5 R_sun range,
indicating a transition from differentially rotating features to rigidly
rotating ones. It has been suggested that the rotation rates measured
in a given study may be related to the lifetimes of features observed,
which should make the simultaneous observation of features rotating
at different rates difficult. Using autocorrelation measurements of
COR1 data we have studied rotation rates between 1.5 and 3.5 solar
radii for features with lifetimes longer than one full rotation. We
observe latitudinally and radially rigid rotation during 2007 and 2008,
and no transition from differentially rotating to rigidly rotating
features. This is consistent with the idea that longer-lived features
rotate more rigidly, or with a transition from differential to rigid
rotation below 1.5 R_sun.

---------------------------------------------------------
Title: Observational Constraints of Coronal Non-Thermal Velocities
from Statistical Analysis of SERTS 1991-1997 Linewidth Observations
Authors: Coyner, A. J.; Davila, J. M.
2009AGUFMSH41B1659C Altcode:
The determination of non-thermal line broadening and velocities from
the spectral linewidth measurements in the EUV provide an observational
limits to available energy from unresolved sources within the observed
coronal structures. These non-thermal velocity components can result
from a number of sources including wave motions , turbulence, and
electron beam interactions among others each of which has been suggested
as a possible means of generating the required energy for the coronal
heating process. .This study presents the determination and statistical
analysis of the non-thermal velocity components of 397 identified EUV
spectral lines from the combined observations of the SERTS 1991-1997
flights covering the wavelength range from 174-418Å. Similar analysis
is also presented for the distributions of active region, quiet sun, and
off-limb emission lines respectively which combine to form the composite
distribution. We find, for all four of these velocity distributions,
a strong non-thermal velocity peak corresponding to a velocity of 20-24
km/s regardless of location or activity level. These velocities suggest
the majority of SERTS observed lines do not produce sufficient energy
within their non-thermal components to contribute significantly to the
heating process and are likely instead to observed motions of plasma
cooling into the SERTS temperature range, peaked near 1.4 MK. The
active region velocity distribution, however, exhibits evidence of a
multi-component distribution through the existence of a high velocity
shoulder which can be fit with a secondary distribution peaking near
47 km/s. This higher velocity component, does possess enough energy
to overcome typical energy losses and potentially contribute to the
available energy of the observed coronal plasma.

---------------------------------------------------------
Title: Streamer belt - CME interactions: A case study for 2008
Authors: Lamb, D. A.; Kramar, M.; Davila, J. M.
2009AGUFMSH41B1668L Altcode:
We investigate the origin of mass and influence of solar coronal mass
ejections (CMEs) on the coronal streamer belt. The pre- and post-CME
streamer belt structure from ~1.5 to 4 R⊙ are found by a tomographic
reconstruction technique from STEREO B/COR1 data for the entire year
2008. These reconstructions allow us to make a case study for several
CMEs during 2008. We find that the streamer belt frequently becomes
notched at the time and location of a CME, indicating significant
streamer mass loss. The notched structures are present for several
days after some CME eruptions. A comparison of the mass lost by the
streamer to the mass of a CME observed in the COR1 field of view can
give a clue to the origin of the majority of the CME mass.

---------------------------------------------------------
Title: Solar Prominence Dynamics Prior to Eruption
Authors: Kilper, G. K.; Davila, J. M.
2009AGUFMSH23B1542K Altcode:
Solar prominence eruptions are extremely important phenomena due to
their association with coronal mass ejections and their effects on space
weather near Earth and throughout the solar system. Some insights into
the eruption mechanism have been made via MHD modeling and observational
studies, but comparisons between the models and observations have
been inconclusive thus far. A coordinated observational study of
prominence eruptions is being carried out to measure and compare
various precursors to eruption that have been found in previous studies,
including: heating of the material, emerging or canceling magnetic flux,
increase in cavity size, and changes in the prominence mass and its
composition. Our analysis examines the timing and the relative degree
of these observational trends prior to eruption, and utilizes a wide
range of observatories and instruments.

---------------------------------------------------------
Title: PROPAGATION AND EVOLUTION OF THE JUNE 1st 2008 CME IN THE
INTERPLANETARY MEDIUM
Authors: Nieves-Chinchilla, T.; Lamb, D. A.; Davila, J. M.; Vinas,
A. F.; Moestl, C.; Hidalgo, M. A.; Farrugia, C. J.; Malandraki, O.;
Dresing, N.; Gómez-Herrero, R.
2009AGUFMSH41A1626N Altcode:
In this work we present a study of the coronal mass ejection (CME)
of June 1st of 2008 in the interplanetary medium. This event has been
extensively studied by others because of its favorable geometry and
the possible consequences of its peculiar initiation for space weather
forecasting. We show an analysis of the evolution of the CME in the
interplanetary medium in order to shed some light on the propagation
mechanism of the ICME. We have determined the typical shock associated
characteristics of the ICME in order to understand the propagation
properties. Using two different non force-free models of the magnetic
cloud allows us to incorporate expansion of the cloud. We use in-situ
measurements from STEREO B/IMPACT to characterize the ICME. In addition,
we use images from STEREO A/SECCHI-HI to analyze the propagation and
visual evolution of the associated flux rope in the interplanetary
medium. We compare and contrast these observations with the results
of the analytical models.

---------------------------------------------------------
Title: On the Origin, 3D Structure and Dynamic Evolution of CMEs
Near Solar Minimum
Authors: Xie, H.; St. Cyr, O. C.; Gopalswamy, N.; Yashiro, S.; Krall,
J.; Kramar, M.; Davila, J.
2009SoPh..259..143X Altcode:
We have conducted a statistical study 27 coronal mass ejections
(CMEs) from January 2007 - June 2008, using the stereoscopic views
of STEREO SECCHI A and B combined with SOHO LASCO observations. A
flux-rope model, in conjunction with 3D triangulations, has been used
to reconstruct the 3D structures and determine the actual speeds of
CMEs. The origin and the dynamic evolution of the CMEs are investigated
using COR1, COR2 and EUVI images. We have identified four types of
solar surface activities associated with CMEs: i) total eruptive
prominence (totEP), ii) partially eruptive prominence (PEP), iii)
X-ray flare, and iv) X-type magnetic structure (X-line). Among the
27 CMEs, 18.5% (5 of 27) are associated with totEPs, 29.6% (8 of 27)
are associated with PEPs, 26% (7 of 27) are flare related, and 26%
(7 of 27) are associated with X-line structures, and 43% (3 of 7)
are associated with both X-line structures and PEPs. Three (11%)
could not be associated with any detectable activity. The mean actual
speeds for totEP-CMEs, PEP-CMEs, flare-CMEs, and X-line-CMEs are 404
km s−1,247 km s−1,909 km s−1,
and 276 km s−1, respectively; the average mean values of
edge-on and broadside widths for the 27 CMEs are 52 and 85 degrees,
respectively. We found that slow CMEs (V≤400 km s−1) tend
to deflect towards and propagate along the streamer belts due to the
deflections by the strong polar magnetic fields of corona holes, while
some faster CMEs show opposite deflections away from the streamer belts.

---------------------------------------------------------
Title: On the Tomographic Reconstruction of the 3D Electron Density
for the Solar Corona from STEREO COR1 Data
Authors: Kramar, M.; Jones, S.; Davila, J.; Inhester, B.; Mierla, M.
2009SoPh..259..109K Altcode:
We present for the first time a three-dimensional reconstruction of
the electron density in the corona at distances from 1.5R⊙
to 4R⊙ using COR1 STEREO observations. The reconstruction
is performed using a regularized tomography inversion method for
two biweekly periods corresponding to Carrington Rotations 2058
and 2066. Images from the two STEREO spacecraft are used to compare
the reconstructed density structures with coronal features located
by triangulation. We find that the location of a bright tip of a
helmet streamer obtained from the tomographic reconstruction is
in good agreement with the location obtained by triangulation. The
reconstructed density structure of the equatorial streamer belt is
largely consistent with the variation of the current sheet derived from
a potential magnetic field extrapolation for most of the equatorial
region and for an MHD model of the corona. A zero-value density region
in the reconstruction is identified with a low-density region seen in
an EUVI image below the reconstruction domain.

---------------------------------------------------------
Title: On 3D Reconstruction of Coronal Mass Ejections: I. Method
Description and Application to SECCHI-COR Data
Authors: Mierla, M.; Inhester, B.; Marqué, C.; Rodriguez, L.; Gissot,
S.; Zhukov, A. N.; Berghmans, D.; Davila, J.
2009SoPh..259..123M Altcode:
The data from SECCHI-COR1 and SECCHI-COR2 coronagraphs onboard the
STEREO mission, which was launched in October 2006, provide us with the
first-ever stereoscopic images of the Sun's corona. These observations
were found to be useful in inferring the three-dimensional structure
of coronal mass ejections (CMEs) and their propagation direction in
space. We apply four methods for reconstructing CMEs: i) Forward
modeling technique; ii) Local correlation tracking (to identify
the same feature in COR Ahead and COR Behind images) plus tie-point
reconstruction technique; iii) Center of mass of the structures in
a given epipolar plane plus tie-point reconstruction technique; iv)
Polarization ratio technique. The four techniques are applied to three
structured CMEs observed by COR1 and COR2 instruments, respectively,
on 15 May 2007, 31 August 2007, and 25 March 2008. A comparison of
the results obtained from the application of the four reconstruction
algorithms is presented and discussed.

---------------------------------------------------------
Title: Relation Between Type II Bursts and CMEs Inferred from STEREO
Observations
Authors: Gopalswamy, N.; Thompson, W. T.; Davila, J. M.; Kaiser,
M. L.; Yashiro, S.; Mäkelä, P.; Michalek, G.; Bougeret, J. -L.;
Howard, R. A.
2009SoPh..259..227G Altcode:
The inner coronagraph (COR1) of the Solar Terrestrial Relations
Observatory (STEREO) mission has made it possible to observe CMEs in
the spatial domain overlapping with that of the metric type II radio
bursts. The type II bursts were associated with generally weak flares
(mostly B and C class soft X-ray flares), but the CMEs were quite
energetic. Using CME data for a set of type II bursts during the
declining phase of solar cycle 23, we determine the CME height when
the type II bursts start, thus giving an estimate of the heliocentric
distance at which CME-driven shocks form. This distance has been
determined to be ∼1.5Rs (solar radii), which coincides
with the distance at which the Alfvén speed profile has a minimum
value. We also use type II radio observations from STEREO/WAVES and
Wind/WAVES observations to show that CMEs with moderate speed drive
either weak shocks or no shock at all when they attain a height where
the Alfvén speed peaks (∼3Rs - 4Rs). Thus
the shocks seem to be most efficient in accelerating electrons in the
heliocentric distance range of 1.5Rs to 4Rs. By
combining the radial variation of the CME speed in the inner corona
(CME speed increase) and interplanetary medium (speed decrease) we
were able to correctly account for the deviations from the universal
drift-rate spectrum of type II bursts, thus confirming the close
physical connection between type II bursts and CMEs. The average height
(∼1.5Rs) of STEREO CMEs at the time of type II bursts
is smaller than that (2.2Rs) obtained for SOHO (Solar and
Heliospheric Observatory) CMEs. We suggest that this may indicate,
at least partly, the density reduction in the corona between the
maximum and declining phases, so a given plasma level occurs closer
to the Sun in the latter phase. In two cases, there was a diffuse
shock-like feature ahead of the main body of the CME, indicating a
standoff distance of 1Rs - 2Rs by the time the
CME left the LASCO field of view.

---------------------------------------------------------
Title: Hinode/EIS observations of propagating low-frequency slow
magnetoacoustic waves in fan-like coronal loops
Authors: Wang, T. J.; Ofman, L.; Davila, J. M.; Mariska, J. T.
2009A&A...503L..25W Altcode: 2009arXiv0908.0310W
Aims: We report the first observation of multiple-periodic propagating
disturbances along a fan-like coronal structure simultaneously detected
in both intensity and Doppler shift in the Fe xii 195 Å line with the
EUV Imaging Spectrometer (EIS) onboard Hinode. A new application of
coronal seismology is provided based on this observation. Methods:
We analyzed the EIS sit-and-stare mode observation of oscillations
using the running difference and wavelet techniques. Results:
Two harmonics with periods of 12 and 25 min are detected. We measured
the Doppler shift amplitude of 1-2 km s-1, the relative
intensity amplitude of 3%-5% and the apparent propagation speed of
100-120 km s-1. Conclusions: The amplitude relationship
between intensity and Doppler shift oscillations provides convincing
evidence that these propagating features are a manifestation of slow
magnetoacoustic waves. Detection lengths (over which the waves are
visible) of the 25 min wave are about 70-90 Mm, much longer than those
of the 5 min wave previously detected by TRACE. This difference may
be explained by the dependence of damping length on the wave period
for thermal conduction. Based on a linear wave theory, we derive an
inclination of the magnetic field to the line-of-sight about 59 ±
8°, a true propagation speed of 128 ± 25 km s-1 and
a temperature of 0.7 ± 0.3 MK near the loop's footpoint from our
measurements. Appendix is only available in electronic form at
http://www.aanda.org

---------------------------------------------------------
Title: Localized Plasma Density Enhancements Observed in STEREO COR1
Authors: Jones, Shaela I.; Davila, Joseph M.
2009ApJ...701.1906J Altcode:
Measurements of solar wind speed in the solar corona, where it is
primarily accelerated, have proven elusive. One of the more successful
attempts has been the tracking of outward-moving density inhomogeneities
in white-light coronagraph images. These inhomogeneities, or "blobs,"
have been treated as passive tracers of the ambient solar wind. Here
we report on the extension of these observations to lower altitudes
using the STEREO COR1 coronagraph, and discuss the implications of
these measurements for theories about the origin of these features.

---------------------------------------------------------
Title: Uritsky, Davila, and Jones Reply:
Authors: Uritsky, Vadim M.; Davila, Joseph M.; Jones, Shaela I.
2009PhRvL.103c9502U Altcode:
A Reply to the Comment by N. W. Watkins, S. C. Chapman, and
S. Rosenberg.

---------------------------------------------------------
Title: Electron Temperature Maps of Low Solar Corona: Results from
the Total Solar Eclipse of 29 March 2006 in Libya
Authors: Reginald, Nelson Leslie; Davila, J.; St. Cyr, C.
2009SPD....40.1403R Altcode:
We conducted an experiment in conjunction with the total solar eclipse
of 29 March 2006 in Libya that measured the coronal intensity through
two filters centered at 3850 and 4100 Angstroms with bandwidths of
40 Angstroms. The purpose of these measurements was to obtain the
intensity ratio through these two filters to determine the electron
temperature. The instrument, Imaging Spectrograph of Coronal Electrons
(ISCORE), consisted of an 8-inch f/10 Schmidt Cassegrain telescope with
a thermoelectrically cooled CCD camera at the focal plane. Results show
temperatures of 105 K close to the limb to 3 MK at 1.3 solar
radii. In the poster we describe this novel technique, and we compare
our results to other relevant measurements. This technique could be
easily implemented on a space-based platform using a coronagraph to
produce global maps of the electron temperature of the solar corona.

---------------------------------------------------------
Title: Analysis of Active Region and Quiet Sun Spectra from SERTS-99
Observations
Authors: Coyner, Aaron J.; Davila, J. M.; Brosius, J. W.; Ofman, L.
2009SPD....40.1216C Altcode:
The Solar EUV Research Telescope and Spectrograph is a rocket-based
instrument that uses high resolution extreme ultraviolet spectra to
investigate features in the solar corona and transition region. The 1999
flight occurred on 24 June 1999 and obtained spectra from both active
regions and quiet sun regions on the solar disk covering a spectral
bandpass 300-355 angstroms We report here the calibrated intensities
and measured linewidths determined from the spatially-averaged spectra
of both active regions and quiet sun regions respectively. In addition,
we determine a distribution of non-thermal velocity components from the
measured linewidths of the identified lines. This distribution provides
a quantitative constraint on the available energy of non-thermal origin
in the observed regions which is available for coronal heating.

---------------------------------------------------------
Title: Propagating Slow Magnetoacoustic Waves in Coronal Loops
Observed by Hinode/EIS
Authors: Wang, T. J.; Ofman, L.; Davila, J. M.
2009ApJ...696.1448W Altcode: 2009arXiv0902.4480W
We present the first Hinode/EUV Imaging Spectrometer observations of
5 minute quasi-periodic oscillations detected in a transition-region
line (He II) and five coronal lines (Fe X, Fe XII, Fe XIII, Fe XIV,
and Fe XV) at the footpoint of a coronal loop. The oscillations
exist throughout the whole observation, characterized by a series of
wave packets with nearly constant period, typically persisting for
4-6 cycles with a lifetime of 20-30 minutes. There is an approximate
in-phase relation between Doppler shift and intensity oscillations. This
provides evidence for slow magnetoacoustic waves propagating upward from
the transition region into the corona. We find that the oscillations
detected in the five coronal lines are highly correlated, and the
amplitude decreases with increasing temperature. The amplitude of
Doppler shift oscillations decrease by a factor of about 3, while
that of relative intensity decreases by a factor of about 4 from Fe
X to Fe XV. These oscillations may be caused by the leakage of the
photospheric p-modes through the chromosphere and transition region
into the corona, which has been suggested as the source for intensity
oscillations previously observed by Transition Region and Coronal
Explorer. The temperature dependence of the oscillation amplitudes
can be explained by damping of the waves traveling along the loop with
multithread structure near the footpoint. Thus, this property may have
potential value for coronal seismology in diagnostic of temperature
structure in a coronal loop.

---------------------------------------------------------
Title: Propagating Slow Magnetoacoustic Waves in Coronal Loops
Observed by Hinode/EIS
Authors: Wang, Tongjiang; Ofman, L.; Davila, J.
2009SPD....40.3003W Altcode:
We present two cases of propagating slow magnetoacoustic waves in
coronal loops observed by Hinode/EIS. In the first case, the 5-min
waves were detected in a transition-region line (He II) and five coronal
lines (Fe X - Fe XV) at a plage region. We find that the oscillations
detected in coronal lines are highly correlated, and the amplitude
decreases with increasing temperature. These waves may be caused by
the leakage of the p-modes through the chromosphere and transition
region into the corona. The temperature dependence of the oscillation
amplitudes can be explained by damping of the waves traveling along
the loop with multithermal fine structure near the footpoint. In
the second case, outwardly propagating (on the order of 100 km/s)
quasi-periodic disturbances along a fan-like coronal structure were
for the first time detected simultaneously in intensity and Doppler
shift. The measured amplitudes for the oscillations are consistent
with the interpretation in terms of slow magnetoacoustic waves rather
than high-speed outflows. The waves contain multiple harmonics of the
periods of 12 min and 25 min. Their origin is not clear. The damping
length of these low-frequency waves is distinctly longer than that of 5
min waves previously detected by TRACE in the similar structure. A new
application of coronal seismology is given based on this observation,
with which the true sound speed and temperature near the loop's
footpoint are estimated. The work of LO and TJW was supported by NRL
grant N00173-06-1-G033. LO was also supported by NASA grant NNG06GI55G.

---------------------------------------------------------
Title: Constraints On Coronal Non-thermal Velocities From SERTS
1991-1997 Observations
Authors: Coyner, Aaron J.; Davila, J. M.; Ofman, L.
2009SPD....40.1302C Altcode:
The determination of non-thermal velocities from spectral line
observations provide insight into the availability of additional energy
sources within the observed regions of the corona. These non-thermal
velocities can be attributed to waves, electron beams, turbulent
motions among other potential sources. Observationally constraining
these velocities directly limits the available energy for heating
within the observed coronal regions. We present the determination
of non-thermal velocity distributions from the 397 identified lines
from the SERTS 1991-1997 flights covering the spectral range 171-355
angstroms along with the distributions for the 253 lines identified
in active regions, the 102 lines from quiet sun regions, and 42 lines
from off limb observations respectively. We find that for all four
the velocity distributions peak at non-thermal velocities between
23-30 km/s independent of activity level suggesting that many of these
non-thermal velocities are likely the result of non-thermal motions
of cooling plasma visible in both active and quiet regions; however
the active region distribution does exhibit a more pronounced high
velocity tail with a secondary bump which could .be the result of a
component resulting from heating of the coronal plasma.

---------------------------------------------------------
Title: On The 3D Structure of the Pre- and After CME Coronal
Streamer Belt
Authors: Kramar, Maxim; Davila, J.; Xie, H.; Antiochos, S.
2009SPD....40.2211K Altcode:
We select several CME events and reconstruct the 3D coronal streamer
belt configurations for the periods of time before and after the
corresponded CMEs. The reconstructions are based on STEREO COR1
observations and made by using a regularized tomography technique
(Kramar et al. 2009). For some CME we found noticeable changes in the
streamer belt structure. Particularly, for a slow CME on June 1, 2008
(Robbrecht et al. 2009) we found that for a longitudinal range of about
10 degrees in Carrington longitude centered at the CME location, the
height of the overlying streamer belt was significantly reduced. This
reduction in height persisted for at least 14 days. The reconstruction
of the streamer belt before and after the CME allows direct estimate
of the mass lost. Also it was found that positions of this and some
others CME correspond to regions in the streamer belt where the latter
has a double structure (i.e. splitted into two parts).

---------------------------------------------------------
Title: STEREO Observations of Slow Coronal Mass Ejections
Authors: Lamb, Derek; Davila, J. M.
2009SPD....40.2103L Altcode:
We have studied the STEREO/COR1 coronal mass ejection (CME) catalog for
the period January-September 2008. Many of the observed CMEs exhibit
slow liftoff speeds, commonly taking over 24 hours for the entire CME
to exit the COR1 field of view. We will present a detailed overview
of these slowly rising CMEs and trace their evolution from the on-disk
source region, where possible, through the field of view of both STEREO
coronagraphs. This is a first step towards studying the evolution of
these CMEs in interplanetary space.

---------------------------------------------------------
Title: On 3D Reconstruction of Coronal Mass Ejections using
SECCHI-COR Data
Authors: Mierla, M.; Inhester, B.; Marque, C.; Rodriguez, L.; Gissot,
S.; Zhukov, A.; Berghmans, D.; Davila, J.
2009EGUGA..11.1145M Altcode:
The data from SECCHI-COR1 and SECCHI-COR2 coronagraphs onboard STEREO
mission which was launched in October 2006 provided us with the
first-ever stereoscopic images of the Sun's corona. These observations
were found to be extremely useful in reconstructing the 3D structure of
coronal mass ejections (CMEs). We apply four methods for reconstructing
the CMEs: 1) Local correlation tracking (to identify the same feature
in COR Ahead and COR Behind images) plus tie-point reconstruction
technique; 2) Center of mass of the structures along the line of
sight (i.e. along each epipolar lines) plus tie-point reconstruction
technique; 3) Polarization ratio technique (see for e.g. Moran and
Davila 2004); 4) Forward modelling technique (see Thernisien et
al. 2006). The four techniques are applied on three structured CMEs
observed by COR1 and COR2 instruments on 15 May 2007, 31 August 2007
and 25 March 2008. A comparison of results obtained from the application
of the four reconstruction algorithms is presented and discussed.

---------------------------------------------------------
Title: Universal processes in heliophysics
Authors: Davila, Joseph M.; Gopalswamy, Nat; Thompson, Barbara J.
2009IAUS..257...11D Altcode:
The structure of the Universe is determined primarily by the interplay
of gravity which is dominant in condensed objects, and the magnetic
force which is dominant in the rarefied medium between condensed
objects. Each of these forces orders the matter into a set of
characteristic structures each with the ability to store and release
energy in response to changes in the external environment. For the
most part, the storage and release of energy proceeds through a number
of Universal Processes. The coordinated study of these processes in
different settings provides a deeper understanding of the underlying
physics governing Universal Processes in astrophysics.

---------------------------------------------------------
Title: EUV Wave Reflection from a Coronal Hole
Authors: Gopalswamy, N.; Yashiro, S.; Temmer, M.; Davila, J.; Thompson,
W. T.; Jones, S.; McAteer, R. T. J.; Wuelser, J. -P.; Freeland, S.;
Howard, R. A.
2009ApJ...691L.123G Altcode:
We report on the detection of EUV wave reflection from a coronal
hole, as observed by the Solar Terrestrial Relations Observatory
mission. The EUV wave was associated with a coronal mass ejection
(CME) erupting near the disk center. It was possible to measure the
kinematics of the reflected waves for the first time. The reflected
waves were generally slower than the direct wave. One of the important
implications of the wave reflection is that the EUV transients are
truly a wave phenomenon. The EUV wave reflection has implications for
CME propagation, especially during the declining phase of the solar
cycle when there are many low-latitude coronal holes.

---------------------------------------------------------
Title: Putting the "I" in IHY: The United Nations Report for the
International Heliophysical Year 2007
Authors: Thompson, Barbara J.; Gopalswamy, Natchimuthuk; Davila,
Joseph M.; Haubold, Hans J.
2009piih.rept.....T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Relation between Coronal Mass Ejection, Type II Radio Burst,
and EUV Wave during the 2008 March 25 STEREO Event
Authors: Gopalswamy, N.; Yashiro, S.; Akiyama, S.; Freeland, S.;
Thompson, W. T.; Davila, J. M.; Howard, R. A.; Kaiser, M. L.; Bougeret,
J. -
2008AGUFMSH12A..02G Altcode:
STEREO and SOHO observations of the March 25, 2008 coronal mass ejection
(CME) provide an excellent opportunity to study its early evolution
from multiple view points. The CME was fast (980 km/s) and wide (112
degrees) from the east limb of the Sun as viewed by SOHO. The STEREO
spacecraft were separated by about 50 degrees, so the CME was a disk
event for the STEREO-behind spacecraft and a behind-the-limb event
for STEREO-ahead. The CME was associated with a well defined EUV wave
as observed by the STEREO/EUVI instrument, a metric type II burst,
and a multi-component type II burst observed by the STEREO/WAVES and
Wind/WAVES instruments. One of the important aspect of this CME is
that it was well observed by STEREO/SECCHI inner coronagraph (COR1)
when the metric type II burst was in progress, so we are able to obtain
the shock height with respect t the CME. This enabled us to infer the
connection the coronal shock driven by the CME (inferred from type II
burst) and the EUV wave. It appears that the EUV wave steepened into
a shock and produced the type II burst. The multiple components of
the type II burst were not harmonically related, so we examined the
circumstances of the eruption. CME was ejected in the region between
two streamers, so the CME-driven shock is likely to simultaneously
encounter high and low- density regions of the corona, thus producing
type II bursts at widely separated frequencies. This paper summarizes
these observations and explains how the CME, type II radio burst,
and EUV waves all fit together.

---------------------------------------------------------
Title: Outreach activities during the 2006 total solar eclipse
sponsored by the International Heliophysical Year
Authors: Rabello Soares, M. C.; Rabiu, A. B.; Gopalswamy, N.; Thompson,
B. J.; Davila, J. M.; Sobrinho, A. A.
2008AdSpR..42.1792R Altcode:
The International Heliophysical Year (IHY) is an international program
of scientific research to advance our understanding of the physical
processes that govern the Sun, Earth and heliosphere. It has a strong
educational component, linking research and education. Here, we describe
the outreach activities during the 2006 total solar eclipse sponsored
by IHY.

---------------------------------------------------------
Title: Electron temperatures and its bulk flow speeds in the low
solar corona measured during the total solar eclipse on 29 March
2006 in Libya
Authors: Reginald, N. L.; Davila, J. M.; St. Cyr, O. C.; Guhathakurta,
M.; Hassler, D. M.
2008AGUFMSH13B1535R Altcode:
We conducted an experiment that measured the K-coronal spectra in the
visible wavelength region, simultaneously at multiple locations in
the low solar corona in conjunction with the total solar eclipse on
29 March 2006 in Libya. The shapes of these measured K-coronal spectra
were then matched with K-coronal models with different combinations of
electron temperatures and electron bulk flow speeds to obtain the best
fit. Results show electron temperatures and bulk flow speeds of 1.10
± 0.05 MK, 103.0 ± 92.0 kms-1; 0.98 ± 0.12 MK, 0.0 + 10.0 kms-1;
0.70 ± 0.08 MK, 0.0 + 10.0 kms-1 at 1.1 R⊙ in the solar north, east
and west, respectively, and 0.93 ± 0.12 MK, 0.0 + 10.0 kms-1 at 1.2R⊙
in the solar east, in agreement with expectations. The instrument used
in this experiment, (MACS)for Multi Aperture Coronal Spectrograph,
used fiber optics in the focal plane of a 12 inch Schmidt Cassegrain
telescope that were positioned at the locations where the above results
were obtained. The light from these fibers were then simulteously fed
in to a spectrograph that contained only reflective optics for the
purpose of enhancing the transmission of light in the blue end of the
spectrum. This was important because steep intensity gradients occurred
in this region, which distinguished between different K-coronal models.

---------------------------------------------------------
Title: Measuring Electron Temperature and Flow Speed using Thomson
Scattered Emission from the Corona Observed with the Solar-C
Coronagraph
Authors: Davila, J. M.; Reginald, N.; St. Cyr, O. C.; Kuhn, J.
2008AGUFMSH11A..05D Altcode:
A method for measuring the density, temperature, and velocity of
coronal electrons was proposed by Reginald and Davila (2000) based on
an extension the Thomson scattering theory of Cram (1976) to include
flows. In this method the electron density is measured in the usual
way (e.g. in LASCO or MkIV coronagraph images) by observing the total
coronal intensity. The electron temperature and flow speed are obtained
by obtaining ratios of spectral intensity measured in 50 A passbands
or by fitting a portion of the spectrum to coronal models. Observations
during the total solar eclipse of 2000 near Lusaka, Zambia demonstrated
the feasibility of the method (Reginald et. al., 2003) using the first
generation Multi-Aperture Coronal Spectrometer (MACS-1) instrument, and
with the second-generation MACS in Libya in 2006 reasonable temperature
and flow speeds were obtained. In this paper we continue this work by
reporting on the results of new observations taken from the ground at
the Solar-C coronagraph. Although eclipse measurements provide the best
observation (nearly free of scattered light but with limited duration),
the Solar-C coronagraph observations allowed several days of nearly
continuous observation from which the repeatability and accuracy of the
measurement could be determined. To deal with the increased atmospheric
scatter, observations at Solar-C were done in polarized brightness
(pB). Results will be reported in this talk.

---------------------------------------------------------
Title: Reconstruction of the solar corona from STEREO COR1
observations
Authors: Kramar, M.; Davila, J.; Inhester, B.
2008AGUFMSH13B1534K Altcode:
The COR1 instruments provide white light observations of the solar
corona from 1.5 to 4 Rsun where the transition from closed to open
coronal structures takes a place. The reconstruction is performed by
the regularized tomography inversion method and gives a 3D distribution
of the electron density in the corona from 1.5 to 4 Rsun. The method
allows to reconstruct only structures which are stationary during an
observation period, i.e. from quarter to half a solar rotation.

---------------------------------------------------------
Title: A Quick Method for Estimating the Propagation Direction of
Coronal Mass Ejections Using STEREO-COR1 Images
Authors: Mierla, M.; Davila, J.; Thompson, W.; Inhester, B.;
Srivastava, N.; Kramar, M.; St. Cyr, O. C.; Stenborg, G.; Howard, R. A.
2008SoPh..252..385M Altcode: 2008SoPh..tmp..170M
We describe here a method to obtain the position of a coronal moving
feature in a three-dimensional coordinate system based on height -
time measurements applied to STEREO data. By using the height -
time diagrams from the two SECCHI-COR1 coronagraphs onboard STEREO,
one can easily determine the direction of propagation of a coronal
mass ejection (i.e., if the moving plasma is oriented toward or away
from the Earth). This method may prove to be a useful tool for space
weather forecasting by easily identifying the direction of propagation
as well as the real speed of the coronal mass ejections.

---------------------------------------------------------
Title: STEREO and RHESSI Observations of Electron Acceleration in
a Partially Disk-Occulted Solar Flare
Authors: Krucker, S.; Wuelser, J. -P.; Vourlidas, A.; Davila, J.;
Thompson, W. T.; White, S.; Lin, R. P.
2008ESPM...12.2.84K Altcode:
RHESSI hard X-ray observations of partially-disk occulted solar flares
provide crucial information on faint coronal hard X-ray sources in the
absence of generally much brighter emissions from footpoints of flare
loops. Coronal hard X-ray sources can differ fundamentally from the
classical footpoint sources of the flare impulsive phase and provide
unique information about the supra-thermal electrons closest to the
site in the corona where their acceleration is believed to occur. The
different view-angles provided by the STEREO spacecraft allow us to put
the partially occulted hard X-ray sources observed by RHESSI in context
with the EUV flare ribbons and the EUV emission from CME observed by
STEREO/EUVI. In this presentation we report on the GOES C8 flare
observed on December 31, 2007 peaking around 01:11UT. From Earth-view
(RHESSI), the flare occurs about 12 degrees behind the eastern limb
giving an occultation height of 16 Mm. From STEREO B, the flare
ribbons are seen on the disk (about 10 degrees from the limb), while
the flare is highly occulted (130 Mm) for STEREO A observations so
that emissions related to the associated CME are seen. Despite the
occultation, RHESSI observes strong non-thermal emissions up to 100
keV that entirely originate from the corona. Initially, the coronal
hard X-ray emission is seen from above the EUV flare ribbons similar
to what is reported in the Masuda flare. Later on, emissions from a
radially extended (approximately 20 Mm) source is seen. The radial
extension is in the same direction as the current sheet of the outward
moving CME suggesting that the HXR emission might be a direct signature
of electrons accelerated in the reconnection process.

---------------------------------------------------------
Title: Emission lines of FeX in active region spectra obtained with
the Solar Extreme-ultraviolet Research Telescope and Spectrograph
Authors: Keenan, F. P.; Jess, D. B.; Aggarwal, K. M.; Thomas, R. J.;
Brosius, J. W.; Davila, J. M.
2008MNRAS.389..939K Altcode: 2008MNRAS.tmp..860K; 2008arXiv0806.3354K
Fully relativistic calculations of radiative rates and electron
impact excitation cross-sections for FeX are used to derive
theoretical emission-line ratios involving transitions in
the 174-366Å wavelength range. A comparison of these with
solar active region observations obtained during the 1989
and 1995 flights of the Solar Extreme-ultraviolet Research
Telescope and Spectrograph (SERTS) reveals generally very good
agreement between theory and experiment. Several FeX emission
features are detected for the first time in SERTS spectra, while the
3s23p52P3/2-3s23p4(1S)3d
2D3/2 transition at 195.32Å is identified for
the first time (to our knowledge) in an astronomical source. The most
useful FeX electron density (Ne) diagnostic line ratios are
assessed to be 175.27/174.53 and 175.27/177.24, which both involve lines
close in wavelength and free from blends, vary by factors of 13 between
Ne = 108 and 1011cm-3,
and yet show little temperature sensitivity. Should these lines
not be available, then the 257.25/345.74 ratio may be employed
to determine Ne, although this requires an accurate
evaluation of the instrument intensity calibration over a relatively
large wavelength range. However, if the weak 324.73Å line of FeX
is reliably detected, the use of 324.73/345.74 or 257.25/324.73
is recommended over 257.25/345.74. Electron densities deduced from
175.27/174.53 and 175.27/177.24 for the stars Procyon and α Cen,
using observations from the Extreme-Ultraviolet Explorer (EUVE)
satellite, are found to be consistent and in agreement with the values
of Ne determined from other diagnostic ratios in the EUVE
spectra. A comparison of several theoretical extreme-ultraviolet
FeX line ratios with experimental values for a θ-pinch, for which
the plasma parameters have been independently determined, reveals
reasonable agreement between theory and observation, providing some
independent support for the accuracy of the adopted atomic data.

---------------------------------------------------------
Title: Reconstruction of the coronal electron density at heights
from 1.5 to 4 Rsun
Authors: Kramar, M.; Jones, S.; Davila, J.; Inhester, B.; Mierla, M.
2008AGUSMSP31D..01K Altcode:
We present a reconstruction of the electron density structure in the
solar corona from 1.5 to 4 Rsun. The reconstruction is performed by the
regularized tomography inversion method and based on the STEREO COR1
pB-images. The reconstruction is made for the period of relatively
quite Sun. The reconstructed density structure of the equatorial
streamer belt in a most of the reconstructed domain is consistent with
the variation of the current sheet derived from a potential magnetic
field model. However, there are also regions where this correlation
is less clear.

---------------------------------------------------------
Title: The STEREO Mission: An Introduction
Authors: Kaiser, M. L.; Kucera, T. A.; Davila, J. M.; St. Cyr, O. C.;
Guhathakurta, M.; Christian, E.
2008SSRv..136....5K Altcode: 2007SSRv..tmp..198K
The twin STEREO spacecraft were launched on October 26, 2006, at 00:52
UT from Kennedy Space Center aboard a Delta 7925 launch vehicle. After
a series of highly eccentric Earth orbits with apogees beyond the moon,
each spacecraft used close flybys of the moon to escape into orbits
about the Sun near 1 AU. Once in heliospheric orbit, one spacecraft
trails Earth while the other leads. As viewed from the Sun, the two
spacecraft separate at approximately 44 to 45 degrees per year. The
purposes of the STEREO Mission are to understand the causes and
mechanisms of coronal mass ejection (CME) initiation and to follow the
propagation of CMEs through the inner heliosphere to Earth. Researchers
will use STEREO measurements to study the mechanisms and sites of
energetic particle acceleration and to develop three-dimensional
(3-D) time-dependent models of the magnetic topology, temperature,
density and velocity of the solar wind between the Sun and Earth. To
accomplish these goals, each STEREO spacecraft is equipped with an
almost identical set of optical, radio and in situ particles and
fields instruments provided by U.S. and European investigators. The
SECCHI suite of instruments includes two white light coronagraphs,
an extreme ultraviolet imager and two heliospheric white light imagers
which track CMEs out to 1 AU. The IMPACT suite of instruments measures
in situ solar wind electrons, energetic electrons, protons and heavier
ions. IMPACT also includes a magnetometer to measure the in situ
magnetic field strength and direction. The PLASTIC instrument measures
the composition of heavy ions in the ambient plasma as well as protons
and alpha particles. The S/WAVES instrument uses radio waves to track
the location of CME-driven shocks and the 3-D topology of open field
lines along which flow particles produced by solar flares. Each of the
four instrument packages produce a small real-time stream of selected
data for purposes of predicting space weather events at Earth. NOAA
forecasters at the Space Environment Center and others will use these
data in their space weather forecasting and their resultant products
will be widely used throughout the world. In addition to the four
instrument teams, there is substantial participation by modeling and
theory oriented teams. All STEREO data are freely available through
individual Web sites at the four Principal Investigator institutions
as well as at the STEREO Science Center located at NASA Goddard Space
Flight Center.

---------------------------------------------------------
Title: Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI)
Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Cook, J. W.; Hurley,
A.; Davila, J. M.; Thompson, W. T.; St Cyr, O. C.; Mentzell, E.;
Mehalick, K.; Lemen, J. R.; Wuelser, J. P.; Duncan, D. W.; Tarbell,
T. D.; Wolfson, C. J.; Moore, A.; Harrison, R. A.; Waltham, N. R.;
Lang, J.; Davis, C. J.; Eyles, C. J.; Mapson-Menard, H.; Simnett,
G. M.; Halain, J. P.; Defise, J. M.; Mazy, E.; Rochus, P.; Mercier,
R.; Ravet, M. F.; Delmotte, F.; Auchere, F.; Delaboudiniere, J. P.;
Bothmer, V.; Deutsch, W.; Wang, D.; Rich, N.; Cooper, S.; Stephens,
V.; Maahs, G.; Baugh, R.; McMullin, D.; Carter, T.
2008SSRv..136...67H Altcode: 2008SSRv..tmp...64H
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) is a five telescope package, which has been developed for
the Solar Terrestrial Relation Observatory (STEREO) mission by the
Naval Research Laboratory (USA), the Lockheed Solar and Astrophysics
Laboratory (USA), the Goddard Space Flight Center (USA), the University
of Birmingham (UK), the Rutherford Appleton Laboratory (UK), the
Max Planck Institute for Solar System Research (Germany), the Centre
Spatiale de Leige (Belgium), the Institut d’Optique (France) and the
Institut d’Astrophysique Spatiale (France). SECCHI comprises five
telescopes, which together image the solar corona from the solar disk to
beyond 1 AU. These telescopes are: an extreme ultraviolet imager (EUVI:
1 1.7 R⊙), two traditional Lyot coronagraphs (COR1: 1.5 4
R⊙ and COR2: 2.5 15 R⊙) and two new designs
of heliospheric imagers (HI-1: 15 84 R⊙ and HI-2: 66 318
R⊙). All the instruments use 2048×2048 pixel CCD arrays
in a backside-in mode. The EUVI backside surface has been specially
processed for EUV sensitivity, while the others have an anti-reflection
coating applied. A multi-tasking operating system, running on a PowerPC
CPU, receives commands from the spacecraft, controls the instrument
operations, acquires the images and compresses them for downlink
through the main science channel (at compression factors typically
up to 20×) and also through a low bandwidth channel to be used for
space weather forecasting (at compression factors up to 200×). An
image compression factor of about 10× enable the collection of images
at the rate of about one every 2 3 minutes. Identical instruments,
except for different sizes of occulters, are included on the STEREO-A
and STEREO-B spacecraft.

---------------------------------------------------------
Title: Heliospheric Images of the Solar Wind at Earth
Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang,
Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.;
Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.;
Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.;
Battams, K.; Esfandiari, E.; Stenborg, G.
2008ApJ...675..853S Altcode:
During relatively quiet solar conditions throughout the spring and
summer of 2007, the SECCHI HI2 white-light telescope on the STEREO
B solar-orbiting spacecraft observed a succession of wave fronts
sweeping past Earth. We have compared these heliospheric images with
in situ plasma and magnetic field measurements obtained by near-Earth
spacecraft, and we have found a near perfect association between the
occurrence of these waves and the arrival of density enhancements
at the leading edges of high-speed solar wind streams. Virtually
all of the strong corotating interaction regions are accompanied by
large-scale waves, and the low-density regions between them lack such
waves. Because the Sun was dominated by long-lived coronal holes and
recurrent solar wind streams during this interval, there is little
doubt that we have been observing the compression regions that are
formed at low latitude as solar rotation causes the high-speed wind
from coronal holes to run into lower speed wind ahead of it.

---------------------------------------------------------
Title: SECCHI Observations of the Sun's Garden-Hose Density Spiral
Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang,
Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.;
Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.;
Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.;
Battams, K.; Esfandiari, E.; Stenborg, G.
2008ApJ...674L.109S Altcode:
The SECCHI HI2 white-light imagers on the STEREO A and B spacecraft
show systematically different proper motions of material moving outward
from the Sun in front of high-speed solar wind streams from coronal
holes. As a group of ejections enters the eastern (A) field of view,
the elements at the rear of the group appear to overrun the elements
at the front. (This is a projection effect and does not mean that the
different elements actually merge.) The opposite is true in the western
(B) field; the elements at the front of the group appear to run away
from the elements at the rear. Elongation/time maps show this effect
as a characteristic grouping of the tracks of motion into convergent
patterns in the east and divergent patterns in the west, consistent
with ejections from a single longitude on the rotating Sun. Evidently,
we are observing segments of the "garden-hose" spiral made visible
when fast wind from a low-latitude coronal hole compresses blobs of
streamer material being shed at the leading edge of the hole.

---------------------------------------------------------
Title: Study of a coronal mass ejection using STEREO/SECCHI and
SOHO/LASCO observations
Authors: Dal Lago, Alisson; Inhester, Bernd; Davila, Joseph; Antunes
Vieira, Luis Eduardo
2008cosp...37..634D Altcode: 2008cosp.meet..634D
The Solar Terrestrial Relations Observatory - STEREO was launched
on October 25th, 2006 and is composed of two nearly identical
spacecrafts, one ahead of Earth in its orbit, the other trailing
behind. Its objective is to study the Sun and the nature of its
coronal mass ejections, or CMEs. Each spacecraft has, among others, an
instrument package called Sun Earth Connection Coronal and Heliospheric
Investigation (SECCHI), which is composed by 4 sets of instruments:
SECCHI EUVI: Extreme UltraViolet Imager; SECCHI COR1: Inner Coronagraph;
SECCHI COR2: Outer Coronagraph; SECCHI HI: Heliospheric Imager. These
instruments are able to study the evolution of CMEs from birth at
the Sun's surface through the corona and interplanetary medium to its
eventual impact at Earth. Since 1996, the Large Angle and Spectrometric
Coronagraph (LASCO), abord the Solar and Heliospheric Observatory
(SOHO), is able to observe the solar corona from 1.1 to 32 solar radii
(LASCO C1, C2 and C3 field of view). This observation capability has
improved substantialy since STEREO SECCHI package is able to observe
from 1.4 solar radii up to 1 AU (earth orbit). In this work, we study
the evolution of a CMEs occurred on January 8th 2007 from 1.4 to beyond
32 solar radii, usind observations from the SECCHI package. Since the
SOHO is still in operation, and since STEREO was very close proximity
of the earth during this event, we were able to compare measurements
from both SECCHI and LASCO instruments for this same CME.

---------------------------------------------------------
Title: Science Eclipses Politics During 2006 U.S. Eclipse Expedition
to Libya
Authors: St. Cyr, O. C.; Davila, Joseph M.; Guhathakurta, Madhulika;
Senseney, Robert S.
2007EOSTr..88..539S Altcode:
A total eclipse of the Sun is one of the most spectacular phenomena of
nature, and it provides a unique venue to gather valuable measurements
of the Sun's corona that cannot otherwise be obtained. Since the time
of the first American expedition to observe the 1780 eclipse during the
American Revolutionary War-with the British granting the observation
vessel safe passage to Maine's Penobscot Bay-the U.S. government has
had a history of supporting scientific expeditions to remote eclipse
sites under difficult conditions. A recent expedition to Libya to
observe and study the 29 March 2006 eclipse continues that tradition.

---------------------------------------------------------
Title: Acquisition and Preparation of Data from Libya 2006 Total
Solar Eclipse
Authors: Nickerson, N. S.; St Cyr, O.; Reginald, N.; Davila, J.
2007AGUFMSH21A0284N Altcode:
Global temperature and wind speed of free electrons in the solar
corona can be measured using light from the visible portion of the
electromagnetic spectrum. Davila et al (SH06, Fall 2007 AGU) describe
the results of a spectrometric investigation using this technique. In
this report we describe a second technique based on filtergrams,
which permit the entire inner corona to be imaged using ratios of
individual exposures. The data gathered during the total eclipse
in Libya March 29, 2006 has provided an opportunity to make such a
measurement. Preparation of the data as well as calibration of the
instrument played a critical role in eliminating uncertainty and
obtaining useful results. In this presentation we will discuss the
details of this preparation and present preliminary results.

---------------------------------------------------------
Title: Remote Sensing of the Electron Temperature and the Solar Wind
Speed Near the Sun
Authors: Davila, J. M.; Reginald, N.; St. Cyr, O. C.
2007AGUFMSH22B..04D Altcode:
In-situ observations provide detailed information on the state of
the solar wind at a particular observation site. But observation of
the global state of the solar wind would require many observation
points strategically placed throughout the heliosphere. In this paper
we report the results of a new optical experiment (the Multi-Aperture
Coronal Spectrograph, MACS) to obtain the electron temperature and flow
speed in the solar corona by observing the visible K-coronal spectrum
during the total solar eclipse on 29 March 2006 in Libya. Results show
electron temperatures of 1.10 ± 0.05, 0.98 ± 0.12, and 0.70 ± 0.08
MK, at 1.1 R\odot in the solar north, east and west, respectively, and
0.93 ± 0.12 MK, at 1.2 R\odot in the solar east. The corresponding
speeds obtained are 103.0 ± 92.0, 0.0 + 10.0, 0.0 + 10.0, and 0.0 +
10.0 km-s-1. The outer corona, where the solar wind speed is high,
is too faint to observe during an eclipse from the ground but it is
easily observed from space. Using the technique demonstrated by MACS,
the next generation of solar coronagraphs will be able to provide not
just density, but also the temperature and flow speed of the solar
wind in the inner corona. This information will improve our models of
the heliosphere, and significantly increase our understanding of the
solar wind.

---------------------------------------------------------
Title: Extraction of Faint Features From STEREO COR1 Data
Authors: Jones, S. I.; Davila, J. M.; Mierla, M.
2007AGUFMSH32A0776J Altcode:
In white light coronagraph data, many kinematic properties of coronal
features are measured by eye. These kinds of measurements can be
difficult or impossible for features whose brightness is comparable
to the noise level of the images. This could present a particular
problem for those attempting to study future events coincident in the
two STEREO COR1 coronagraphs. As their angular separation increases
it will be increasingly difficult to see events in both instruments,
since brightness falls off quickly with distance from the plane of the
sky. In this work we seek to extend the intensity range of features that
can be studied in COR1 data to previously intractable signal levels,
using an unusual image differencing method and an angular integration
technique presented by Dal Lago et al (2004). Challenges inherent to
using this scheme with COR1 data will be discussed and examples of
such faint features in original and enhanced versions will be presented.

---------------------------------------------------------
Title: 3D Reconstruction of the Electron Density in the Corona from
COR1 STEREO Observations
Authors: Kramar, M.; Jones, S.; Davila, J.; Inhester, B.
2007AGUFMSH42A..07K Altcode:
We present 3D reconstruction for the electron density in the
corona based on the COR1 STEREO observations. The reconstruction is
performed by using regularized tomography inversion method. Since the
solar corona is optically thin, coronal observations are essentially
integrated over the line-of-sight (LOS). It is therefore impossible to
resolve the structure of the corona along the LOS if observations are
provided from a single view direction. Observations from different
view positions are necessary to reconstruct 3D coronal structure
and is the essence of the tomography inversion method. When having
observations only from a single view direction, a rigid rotation of
the coronal density structures with the Sun about the ecliptic must be
assumed in order to apply the tomography technique. As a consequence,
only structures which are stationary over half a solar rotation can
be reconstructed. The STEREO observations allow us to reduce this
stationarity assumption. For reconstruction we choose a period when
the Sun is relatively quite. However some active events occurred,
and we need to skip the data for these events. Therefore, in order
to stabilize the reconstruction, the smoothness factor was used as
regularization constraint during the inversion.

---------------------------------------------------------
Title: Wavelength Determination for Solar Features Observed by the
EUV Imaging Spectrometer on Hinode
Authors: Brown, Charles M.; Hara, Hirohisa; Kamio, Suguru; Feldman,
Uri; Seely, John F.; Doschek, George A.; Mariska, John T.; Korendyke,
Clarence M.; Lang, James; Dere, Kenneth P.; Culhane, Len; Thomas,
Roger J.; Davila, Joseph M.
2007PASJ...59S.865B Altcode:
A wavelength calibration of solar lines observed by the high
resolution EUV Imaging Spectrometer (EIS) on the Hinode satellite
is reported. Spectral features of the quiet sun and of two mildly
active areas were measured and calibrated. A listing of the stronger
observed lines with identification of the leading contributor ions
is presented. 41 lines are reported, with 90% identified. Wavelength
precisions (2σ) of ±0.0031Å for the EIS short band and ±0.0029Å
for the EIS long band are obtained. These lines, typical of 1-2
×106 K plasmas, are recommended as standards for the
establishment of EIS wavelength scales. The temperature of EIS varies
by about 1D.5 C around the orbit and also with spacecraft pointing. The
correlation of these temperature changes with wavelength versus pixel
number scale changes is reported.

---------------------------------------------------------
Title: Coexistence of Self-Organized Criticality and Intermittent
Turbulence in the Solar Corona
Authors: Uritsky, Vadim M.; Paczuski, Maya; Davila, Joseph M.; Jones,
Shaela I.
2007PhRvL..99b5001U Altcode: 2006astro.ph.10130U
An extended data set of extreme ultraviolet images of the solar corona
provided by the SOHO spacecraft is analyzed using statistical methods
common to studies of self-organized criticality (SOC) and intermittent
turbulence (IT). The data exhibit simultaneous hallmarks of both
regimes: namely, power-law avalanche statistics as well as multiscaling
of structure functions for spatial activity. This implies that both
SOC and IT may be manifestations of a single complex dynamical process
entangling avalanches of magnetic energy dissipation with turbulent
particle flows.

---------------------------------------------------------
Title: The Early Life Of A Coronal Mass Ejection From SECCHI And
SOHO Observations
Authors: Gopalswamy, N.; Yashiro, S.; Davila, J. M.; Howard, R. A.;
SECCHI/COR1 Team
2007AAS...210.2813G Altcode: 2007BAAS...39..324G
One of the key advantages of STEREO/SECCHI is the inner coronagraph
(COR1), which can observe CMEs in the coronal region where CMEs
attain their maximum acceleration. The first CME observed by COR1
was on 2006 December 30. The CME was also observed by the C2 and C3
coronagraphs of SOHO. We compare the morphological and height-time
histories between COR1 and SOHO/LASCO data. We find that the flux
rope structure evolves significantly between the COR1 and LASCO/C2
FOVs, although we can track features to get a continuous height-time
history of the CME. We find excellent agreement between the two sets
of data which could be combined to obtain the kinematic properties
of the CME. We also superposed a STEREO/COR1 image of the CME on a
STEREO/EUVI image and SOHO/C2 image to compare the solar origin and
morphology. The CME originated from the southwest quadrant of the Sun
and was of flux-rope type moving with an average speed of 200 km/s and
an acceleration of 6 m/s/s, with a characteristic two-ribbon structure
and an extended post-eruption arcade. In addition to the similarity in
CME features, there was excellent correspondence between the outlying
streamers in the two coronagraph images.

---------------------------------------------------------
Title: The EUV Imaging Spectrometer for Hinode
Authors: Culhane, J. L.; Harra, L. K.; James, A. M.; Al-Janabi, K.;
Bradley, L. J.; Chaudry, R. A.; Rees, K.; Tandy, J. A.; Thomas, P.;
Whillock, M. C. R.; Winter, B.; Doschek, G. A.; Korendyke, C. M.;
Brown, C. M.; Myers, S.; Mariska, J.; Seely, J.; Lang, J.; Kent,
B. J.; Shaughnessy, B. M.; Young, P. R.; Simnett, G. M.; Castelli,
C. M.; Mahmoud, S.; Mapson-Menard, H.; Probyn, B. J.; Thomas, R. J.;
Davila, J.; Dere, K.; Windt, D.; Shea, J.; Hagood, R.; Moye, R.; Hara,
H.; Watanabe, T.; Matsuzaki, K.; Kosugi, T.; Hansteen, V.; Wikstol, Ø.
2007SoPh..243...19C Altcode:
The EUV Imaging Spectrometer (EIS) on Hinode will observe solar corona
and upper transition region emission lines in the wavelength ranges
170 - 210 Å and 250 - 290 Å. The line centroid positions and profile
widths will allow plasma velocities and turbulent or non-thermal line
broadenings to be measured. We will derive local plasma temperatures and
densities from the line intensities. The spectra will allow accurate
determination of differential emission measure and element abundances
within a variety of corona and transition region structures. These
powerful spectroscopic diagnostics will allow identification
and characterization of magnetic reconnection and wave propagation
processes in the upper solar atmosphere. We will also directly study
the detailed evolution and heating of coronal loops. The EIS instrument
incorporates a unique two element, normal incidence design. The optics
are coated with optimized multilayer coatings. We have selected highly
efficient, backside-illuminated, thinned CCDs. These design features
result in an instrument that has significantly greater effective area
than previous orbiting EUV spectrographs with typical active region
2 - 5 s exposure times in the brightest lines. EIS can scan a field
of 6×8.5 arc min with spatial and velocity scales of 1 arc sec and
25 km s−1 per pixel. The instrument design, its absolute
calibration, and performance are described in detail in this paper. EIS
will be used along with the Solar Optical Telescope (SOT) and the X-ray
Telescope (XRT) for a wide range of studies of the solar atmosphere.

---------------------------------------------------------
Title: Advances in Solar Coronagraphy
Authors: Rabin, D.; St. Cyr, O. C.; Davila, J. M.
2007lyot.confE..18R Altcode:
Could Bernard Lyot have imagined the protean forms in which his most
notable invention, the coronagraph, would appear 75 years later? Could
he have foreseen that the most widely used solar coronagraphs would be
based in space, or that coronagraphs would seek to image planets and
disks around other stars? Perhaps so - he was far more than a builder
of creative instruments. I will discuss advances in solar coronagraphy
since Lyot's time, in both the science that drives the observations
and the technology that sustains them.

---------------------------------------------------------
Title: Results From Observations Taken During The Total Solar Eclipse
of 2006
Authors: Davila, Joseph M.; Reginald, N.; St. Cyr, O. C.; Guhathakurta,
M.; Hassler, D.
2007AAS...21010504D Altcode: 2007BAAS...39..231D
Using the Multi-Aperture Coronal Spectrometer (MACS) we measured the
K-coronal spectrum in the visible wavelength range at multiple locations
in the low solar corona during the total solar eclipse, which occured
on 29 March 2006 In Libya. The purpose of these measurements was to
obtain the thermal electron temperature, and its flow speed at those
locations. The observed K-coronal spectrum was matched with models to
obtain the best fit to the data. These observations could be easily
performed from a space-based platform to produce global maps of the
electron density, temperature, and flow speed at the base of the
solar wind.

---------------------------------------------------------
Title: Early Results from STEREO SECCHI COR1
Authors: St. Cyr, Orville C.; Davila, J. M.; Thompson, W.; Thompson,
B. J.; Gurman, J. B.; Burkepile, J. T.; de Toma, G.
2007AAS...21011903S Altcode: 2007BAAS...39..243S
With the successful launch and commissioning of STEREO, routine
observations of the Sun's corona by the payload began in early 2007. The
COR1 internally-occulted coronagraphs, which are classically-designed
Lyot instruments covering 1.4-4.0 Rsun, are performing extremely
well. More than two dozen coronal mass ejections (CMEs) were detected
by COR1 in the first month of observations. As the STEREO spacecraft
separate away from Earth, the MK4 coronameter at MLSO will provide
a third vantage point for observations of the low corona. In this
presentation we will show CME observations from COR1 and MK4, and we
will describe the context of these new observations.

---------------------------------------------------------
Title: The Sun To The Earth, A Panoramic View From SECCHI: Overview
Authors: Moses, John Daniel; Newmark, J.; Howard, R. A.; Plunkett,
S.; Socker, D.; Wang, D.; Vourlidas, A.; Halain, J.; Harrison, R. A.;
Eyles, C. J.; Davila, J.; Lemen, J.; Wuelser, J.
2007AAS...21011904M Altcode: 2007BAAS...39..244M
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) is the remote sensing component of the STEREO mission
to explore the source, initiation, and propagation through the
heliosphere of Coronal Mass Ejections (CMEs). To achieve this goal,
SECCHI must continuously observe CMEs from two different perspectives
beginning with the pre-event coronal configuration and ending with the
propagation of the event out of the inner heliosphere. Thus, each of
the two STEREO observatories carries a suite of SECCHI telescopes with
5 different fields of view providing an uninterrupted view of coronal
and Heliospheric phenomena from the solar chromosphere to 1 AU. This
is the first panoramic view of the inner heliosphere dedicated to
observing the spatial and temporal scales characteristic of CMEs at
elongation angles from 0 to almost 90 degrees. We present first
results from the SECCHI imaging suite with emphasis on the unprecedented
panoramic views of the heliosphere. We show direct observations of
CMEs and the solar wind from initiation on the Sun throughout the inner
heliosphere to 1 AU. The SECCHI suite performance exceeds that necessary
to achieve the Level 1 STEREO science objectives. Thus, as the STEREO
spacecraft separate to provide views from different directions we can
anticipate breakthrough observations for issues currently unresolved
by plane-of-sky projections through optically thin structures. The most current information on SECCHI can be obtained from the
STEREO mission website at http://stereo.gsfc.nasa.gov and the SECCHI
website at http://secchi.nrl.navy.mil. The NRL participation in the
STEREO mission is supported by NASA under S-13631-Y, and by the Office
of Naval Research.

---------------------------------------------------------
Title: IHY - An International Cooperative Program
Authors: Rabello-Soares, M. Cristina; Davila, J.; Gopalswamy, N.;
Thompson, B.
2007AAS...210.5701R Altcode: 2007BAAS...39..167R
The International Heliophysical Year (IHY) in 2007/2008 involves
thousands of scientists representing over 70 nations. It consists
of four distinct elements that will be described here. Taking
advantage of the large amount of heliophysical data acquired routinely
by a vast number of sophisticated instruments aboard space missions and
at ground-based observatories, IHY aims to develop the basic science of
heliophysics through cross-disciplinary studies of universal processes
by means of Coordinated Investigation Programs (CIPs). The second
component is in collaboration with the United Nations Basic Space
Science Initiative (UNBSSI) and consists of the deployment of arrays of
small, inexpensive instruments such as magnetometers, radio antennas,
GPS receivers, etc. around the world to provide global measurements. An
important aspect of this partnership is to foster the participation
of developing nations in heliophysics research. IHY coincides
with the commemoration of 50 years of the space age that started with
launch of Sputnik on October 4, 1957 and it is on the brink of a new
age of space exploration where the Moon, Mars and the outer planets
will be the focus of the space programs in the next years. As a result,
it presents an excellent opportunity to create interest for science
among young people with the excitement of discovery of space. The
education and outreach program forms another cornerstone of IHY. Last but not least, an important part of the IHY activities, its
forth component, is to preserve the history and memory of IGY 1957.

---------------------------------------------------------
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.;
Socker, D. G.; Wang, D.; Plunkett, S. P.; Baugh, R.; McMullin, D. R.;
Davila, J. M.; Thompson, W. T.; Lemen, J. R.; Wuelser, J.; Harrison,
R. A.; Waltham, N. R.; Davis, C. J.; Eyles, C. J.; Defise, J.; Halain,
J.; Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet,
M. F.
2007AGUSMSH33A..01H Altcode:
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs, and
two telescopes that comprise the heliospheric imager. SECCHI will
observe coronal mass ejections (CMEs) from their birth at the sun,
through the corona and into the heliosphere. A complete instrument
suite is being carried on each of the two STEREO spacecraft, which
will provide the first sampling of a CME from two vantage points. The
spacecraft, launched 25 October 2006, are orbiting the Sun, one Ahead
of the Earth and the other Behind, each separating from Earth at about
22 degrees per year. The varying separation means that we will have
different observational capabilities as the spacecraft separate and
therefore differing science goals. The primary science objectives
all are focused on understanding the physics of the CME process
their initiation, 3D morphology, propagation, interaction with the
interplanetary medium and space weather effects. By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time, answers to some
of the outstanding questions will be obtained. We will show some of
the initial results.

---------------------------------------------------------
Title: Reducing The Effects Of Spacecraft Jitter In Stereo Cor1 Images
Authors: Jones, Shaela I.; Davila, J.; Cremades, H.; Kramar, M.
2007AAS...210.2809J Altcode: 2007BAAS...39..136J
The STEREO mission was launched in Oct 2006, and has currently completed
lunar swingbys. The instrument is operating normally, however spacecraft
jitter causes an increase in scattered light on one side of the image
and a decrease on the opposite side. Because it changes from one image
to the next, this scattered light requires special processing on the
ground. We present a method for reducing this effect using data from
the Guide Telescope.

---------------------------------------------------------
Title: On the Regularized Tomography for the Solar Corona
Authors: Kramar, Maxim; Jones, S.; Davila, J.; Inhester, B.
2007AAS...210.2802K Altcode: 2007BAAS...39..135K
Since the solar corona is optically thin, coronal observations are
essentially integrated over the line-of-sight (LOS). It is therefore
impossible to resolve the structure of the corona along the LOS if
observations are provided from a single view direction. Observations
from different view positions are necessary to reconstruct 3D coronal
structure and is the essence of the tomography inversion method. When
having observations only from a single view direction, a rigid rotation
of the coronal density structures with the Sun about the ecliptic
must be assumed in order to apply the tomography technique. As a
consequence, only structures which are stationary over half a solar
rotation can be reconstructed. The STEREO observations allow us to
reduce this stationarity assumption. Depending on the size of the
reconstructing domain, the number of the observations, data noise, etc,
the reconstruction usually is not unique. To stabilize the solution,
we introduce regularization into the inversion which is essentially
a smoothness factor for the density reconstruction. The introduced
regularization is not isotropic in order to prevent smoothing the radial
structures often observed in the corona. Unlike usual scalar field
tomography, which is essentially two-dimensional, our regularization
concept and also the tilt of the Sun's axis with respect to the ecliptic
requires to perform operations over the entire 3D domain during every
iteration, which increases the computational resources needed for
the inversion. To increase computational performance and resolution
of the reconstructing domain, we apply a MPI-parallelization for the
inversion code. The code is going to be used with STEREO COR1 data.

---------------------------------------------------------
Title: Stereo Observations Of The Solar Corona Using The Secchi
Experiment
Authors: Plunkett, Simon P.; Howard, R. A.; Moses, J. D.; Vourlidas,
A.; Socker, D.; Newmark, J.; Wang, D.; Baugh, R.; Davila, J.;
Thompson, W.; St. Cyr, O. C.; Lemen, J.; Wuelser, J. P.; Harrison,
R. A.; Waltham, N.; Davis, C. J.; Eyles, C. J.; Defise, J. M.; Halain,
J. P.; Bothmer, V.; Delaboudiniere, J. P.; Auchere, F.; Mercier, R.;
Ravet, M. F.
2007AAS...21011901P Altcode: 2007BAAS...39..243P
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs,
and two telescopes that comprise the heliospheric imager. The main
objective of SECCHI is to observe coronal mass ejections (CMEs) from
their birth at the sun, through the corona and into the heliosphere. A
complete instrument suite is being carried on each of the two STEREO
spacecraft, which will provide the first sampling of a CME from two
vantage points as the spacecraft separate from each other at the rate
of about 45 degrees per year. We will show examples of some of the
data and some of the initial stereo results.

---------------------------------------------------------
Title: The Sun To The Earth, A Panoramic View From SECCHI: CME
Observations Through The Inner Heliosphere
Authors: Newmark, Jeffrey; Moses, J. D.; Howard, R. A.; Plunkett, S.;
Socker, D.; Wang, D.; Vourlidas, A.; Halain, J. P.; Harrison, R. A.;
Eyles, C. J.; Davila, J.; Lemen, J.; Wuelser, J. P.
2007AAS...21011905N Altcode: 2007BAAS...39..244N
The STEREO SECCHI telescope suite is returning unprecedented viewsvof
the Sun and inner heliosphere. The SECCHI instruments on each of the two
STEREO spacecraft are observing Coronal Mass Ejections (CMEs) from their
initiation, through the corona, and into interplanetary space beyond the
Earth's orbit. We present a first analysis of a CME throughout the inner
heliosphere. We focus on the propagation characteristics of the CME
and the morphological properties of the CME as viewed from STEREO. This first glimpse of a CME in the heliosphere clearly demonstrates
the anticipated scientific returns that future STEREO observations
(at larger angular separations) of CMEs in interplanetary space will
provide. The most current information can be obtained on the STEREO
mission website at http://stereo.gsfc.nasa.gov and the SECCHI website
at http://secchi.nrl.navy.mil. The NRL participation on SECCHI is
supported by NASA under S-13631-Y, and by the Office of Naval Research.

---------------------------------------------------------
Title: Fe XIII emission lines in active region spectra obtained with
the Solar Extreme-Ultraviolet Research Telescope and Spectrograph
Authors: Keenan, F. P.; Jess, D. B.; Aggarwal, K. M.; Thomas, R. J.;
Brosius, J. W.; Davila, J. M.
2007MNRAS.376..205K Altcode: 2006astro.ph.12493K; 2007MNRAS.tmp...38K
Recent fully relativistic calculations of radiative
rates and electron impact excitation cross-sections
for Fe XIII are used to generate emission-line ratios
involving 3s23p2-3s3p3 and
3s23p2-3s23p3d transitions in
the 170-225 and 235-450 Å wavelength ranges covered by the Solar
Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS). A
comparison of these line ratios with SERTS active region observations
from rocket flights in 1989 and 1995 reveals generally very good
agreement between theory and experiment. Several new Fe XIII emission
features are identified, at wavelengths of 203.79, 259.94, 288.56 and
290.81 Å. However, major discrepancies between theory and observation
remain for several Fe XIII transitions, as previously found by Landi
and others, which cannot be explained by blending. Errors in the adopted
atomic data appear to be the most likely explanation, in particular for
transitions which have 3s23p3d 1D2
as their upper level. The most useful Fe XIII electron-density
diagnostics in the SERTS spectral regions are assessed, in terms of
the line pairs involved being (i) apparently free of atomic physics
problems and blends, (ii) close in wavelength to reduce the effects
of possible errors in the instrumental intensity calibration, and
(iii) very sensitive to changes in Ne over the range
108-1011 cm-3. It is concluded that
the ratios which best satisfy these conditions are 200.03/202.04 and
203.17/202.04 for the 170-225 Å wavelength region, and 348.18/320.80,
348.18/368.16, 359.64/348.18 and 359.83/368.16 for 235-450 Å.

---------------------------------------------------------
Title: The United Nations Basic Space Science Initiative for IHY 2007
Authors: Gopalswamy, Nat; Davila, Joseph; Thompson, Barbara; Haubold,
Hans
2007IAUSS...5..295G Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The United Nations Basic Space Science Initiative: the
TRIPOD concept
Authors: Kitamura, Masatoshi; Wentzel, Don; Henden, Arne; Bennett,
Jeffrey; Al-Naimiy, H. M. K.; Mathai, A. M.; Gopalswamy, Nat; Davila,
Joseph; Thompson, Barbara; Webb, David; Haubold, Hans
2007IAUSS...5..277K Altcode: 2006physics..10149K
Since 1990, the United Nations is annually holding a workshop on
basic space science for the benefit of the worldwide development of
astronomy. Additional to the scientific benefits of the workshops and
the strengthening of international cooperation, the workshops lead to
the establishment of astronomical telescope facilities through the
Official Development Assistance (ODA) of Japan. Teaching material,
hands-on astrophysics material, and variable star observing programmes
had been developed for the operation of such astronomical telescope
facilities in an university environment. This approach to astronomical
telescope facility, observing programme, and teaching astronomy has
become known as the basic space science TRIPOD concept. Currently,
a similar TRIPOD concept is being developed for the International
Heliophysical Year 2007, consisting of an instrument array, data taking
and analysis, and teaching space science.

---------------------------------------------------------
Title: The International Heliophysical Year
Authors: Davila, Joseph M.; Gopalswamy, Nat; Thompson, Barbara J.
2007RoAJ...17....3D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Investigating the state of the Sun-Earth system during extreme
events: First science results of a worldwide online conference series
Authors: Kozyra, J. U.; Shibata, K.; Fox, N. J.; Basu, S.; Coster,
A. J.; Davila, J. M.; Gopalswamy, N.; Liou, K.; Lu, G.; Mann, I. R.;
Pallamraju, D.; Paxton, L. J.; Peterson, W. K.; Talaat, E. R.;
Weatherwax, A. T.; Young, C. A.; Zanetti, L. J.
2006AGUFMSA43A..01K Altcode:
This presentation reports on new science results from an online
conference entitled "Return to the Auroral Oval for the Anniversary
of the IGY" designed to bring together researchers worldwide: (1)
to investigate newly reported features in the auroral oval during
substorms that occur in the main phase of superstorms and how these
features map throughout geospace, (2) to explore implications for the
state of the geospace system, (3) to identify signatures associated
with this geospace state from equatorial to polar latitudes,
(4) to investigate the unusual aspects of the solar sources, and
(5) to understand how propagation from Sun to Earth modified the
observed solar drivers. The main focus of the first conference is on
worldwide data exchange, the construction of global data products and
assimilative global views, and identifying coupled chains of events
from sun-to-Earth. The collaborative conference data products and
enhanced understanding of the observed features of the events will
form the basis for a follow-on conference in 2007 focused primarily
on theoretical studies and collaborative simulation efforts between
modeling groups, observers and data analysts. This conference is the
first in a series of sun-Earth connection online conferences, sponsored
by CAWSES, IHY, eGY, ICESTAR, NASA/LWS, and NSF Atmospheric Science
Programs, and designed to bring interdisciplinary researchers together
with the vast developing cyber-infrastructure of large international
data sets, high performance computing and advanced visualizations to
address grand challenge science issues in a way not previously possible.

---------------------------------------------------------
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R. A.; Moses, D.; Vourlidas, A.; Newmark, J.; Socker,
D. G.; Plunkett, S.; Wang, D.; Baugh, R.; McMullin, D.; Davila, J.;
St. Cyr, C.; Thompson, W. T.; Lemen, J.; Wuelser, J.; Harrison, R. A.;
Waltham, N. R.; Davis, C.; Eyles, C. J.; Defise, J.; Halain, J.;
Bothmer, V.; Delaboudiniere, J.; Auchere, F.; Mercier, R.; Ravet, M.
2006AGUFMSM12A..02H Altcode:
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of an
extreme ultraviolet (EUV) imager, two white light coronagraphs, and
two telescopes that comprise the heliospheric imager. SECCHI will
observe coronal mass ejections (CMEs) from their birth at the sun,
through the corona and into the heliosphere. A complete instrument
suite is being carried on each of the two STEREO spacecraft, which
will provide the first sampling of a CME from two vantage points. The
spacecraft will orbit the Sun, one Ahead of the Earth and the other
Behind, each separating from Earth at about 22 degrees per year. The
varying separation means that we will have different observational
capabilities as the spacecraft separate and therefore differing science
goals. The primary science objectives all are focused on understanding
the physics of the CME process their initiation, 3D morphology,
propagation, interaction with the interplanetary medium and space
weather effects. By observing the CME from multiple viewpoints with UV
and coronagraphic telescopes and by combining these observations with
radio and in-situ observations from the other instruments on STEREO as
well as from other satellites and ground based observatories operating
at the same time, answers to some of the outstanding questions will
be obtained. STEREO follows the very successful SOHO mission. SOHO's
success was primarily due to the highly complementary nature of the
instruments, but it was partly due to the very stable platform. The
L1 orbit enables an extremely stable thermal environment and thus
very stable pointing, as well as uninterrupted solar viewing. The
STEREO will have both of these characteristics, but in addition will
have multi-viewpoint viewing of CMEs, which will greatly enhance the
many discoveries that SOHO data have produced. We have been developing
techniques to interpret the observations from multiple viewpoints and
to perform 3-dimensional deconvolution of the CME observations using
forward modeling and inversion techniques. A continuous downlink of
STEREO data will provide a low-resolution, real- time view from all
of the instruments. The full data are downlinked once a day and will
be available about 24 hours later. We will present some preliminary
results from the instrument, which is expected to be launched in
October/November, 2006

---------------------------------------------------------
Title: Optics and mechanisms for the Extreme-Ultraviolet Imaging
Spectrometer on the Solar-B satellite
Authors: Korendyke, Clarence M.; Brown, Charles M.; Thomas, Roger J.;
Keyser, Christian; Davila, Joseph; Hagood, Robert; Hara, Hirohisa;
Heidemann, Klaus; James, Adrian M.; Lang, James; Mariska, John T.;
Moser, John; Moye, Robert; Myers, Steven; Probyn, Brian J.; Seely,
John F.; Shea, John; Shepler, Ed; Tandy, Jason
2006ApOpt..45.8674K Altcode:
The Extreme-Ultraviolet Imaging Spectrometer (EIS) is the first of a
new generation of normal-incidence, two-optical-element spectroscopic
instruments developed for space solar extreme-ultraviolet astronomy. The
instrument is currently mounted on the Solar-B satellite for a planned
launch in late 2006. The instrument observes in two spectral bands,
170-210 Å and 250-290 Å. The spectrograph geometry and grating
prescription were optimized to obtain excellent imaging while still
maintaining readily achievable physical and fabrication tolerances. A
refined technique using low ruling density surrogate gratings and
optical metrology was developed to align the instrument with visible
light. Slit rasters of the solar surface are obtained by mechanically
tilting the mirror. A slit exchange mechanism allows selection among
four slits at the telescope focal plane. Each slit is precisely located
at the focal plane. The spectrograph imaging performance was optically
characterized in the laboratory. The resolution was measured using
the Mg iii and Ne iii lines in the range of 171-200 Å. The He ii line
at 256 Å and Ne iii lines were used in the range of 251-284 Å. The
measurements demonstrate an equivalent resolution of ∼2 arc sec⁡ on
the solar surface, in good agreement with the predicted performance. We
describe the EIS optics, mechanisms, and measured performance.

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Title: Co-existence of self-organized criticality and intermittent
turbulence in the solar corona
Authors: Uritsky, V.; Paczuski, M.; Davila, J. M.; Jones, S.
2006AGUFMSH13A0397U Altcode:
Turbulence and self-organized criticality (SOC) represent two
major paths of dynamical complexity in driven, extended nonlinear
systems. We present direct observational evidence for co-existence of
these phenomena in the magnetized plasma of the solar corona. Using
an extended collection of SOHO EIT images, we apply two alternative
numerical analysis methods - one for analyzing avalanche statistics
of bursty dissipation events and the other for studying spatial
intermittency in the coronal emission field. We find that the energy
and lifetime statistics of bursty dissipation in the corona obey
robust scaling laws over the entire range of the observed scales. In
contrast to previous studies of flare statistics, this observation is
made using a spatiotemporal event detection algorithm compatible with
the definition of avalanches in SOC simulations. Next, by applying
statistical tools developed in fluid turbulence, we show that the same
time series of emission patterns exhibits multiscaling and extended
self-similarity of higher order structure functions characteristic of
intermittent turbulence. The observed scaling behaviors show only weak
dependence on average solar activity level and have been identified
under both solar minimum and maximum conditions.

---------------------------------------------------------
Title: IHY-CAWSES Data base
Authors: Young, C. A.; Thompson, B. J.; Davila, J.; Gopalswamy, N.
2006ihy..workE..90Y Altcode:
In partnership with the CAWSES (Climate And Weather of the Sun-Earth
System) program, IHY is sponsoring a series of Virtual Workshops
and a special IHY/CAWSES database to provide virtual access of data
collected for IHY and CAWSES campaigns. The first of the virtual
workshops occurred November 13-17, 2006, and had more than 200 online
participants. Online presentation and discussion tools are being
refined for future workshops. The IHY/CAWSES database provides a means
of entering data into the Virtual Solar Observatory (to provide the
maximum and easiest possible access to the data) while still maintaining
a close connection to the other data sets used in IHY/CAWSES activities.

---------------------------------------------------------
Title: International Heliophysical Year (IHY) Overview: Science,
Observatory Development, Outreach and History
Authors: Davila, J. M.
2006ihy..workE..13D Altcode:
In 1957 a program of international research, inspired by the
International Polar Years of 1882-83 and 1932-33, was organized as
the International Geophysical Year (IGY) to study global phenomena of
the Earth and geospace. The IGY involved about 60,000 scientists from
66 nations, working at thousands of stations, from pole to pole to
obtain simultaneous, global observations on Earth and in space. There
had never been anything like it before. On the fiftieth anniversary
of the International Geophysical Year an international program of
scientific collaboration will be conducted called the International
Heliophysical Year (IHY). Like it predecessors, the IHY will focus on
fundamental global questions of Earth and space science. The goals of
the IHY are to: 1. Develop the basic science of heliophysics through
cross- disciplinary studies of universal processes. 2. Determine the
response of terrestrial and planetary magnetospheres and atmospheres
to external drivers. 3. Promote research on the Sun-heliosphere system
outward to the local interstellar medium - the new frontier. 4. Foster
international scientific cooperation in the study of heliophysical
phenomena now and in the future. 5. Preserve the history and legacy
of the IGY on its 50th Anniversary. 6. Communicate unique IHY results
to the scientific community and the general public. The IHY will help
us develop a deeper understanding of physical processes in the solar
system through a program of comparative study of universal processes
that affect the interplanetary and terrestrial environment. The study
of energetic events in the solar system will pave the way for safe
human space travel to the Moon and planets in the future, and it will
serve to inspire the next generation of space physicists.

---------------------------------------------------------
Title: IHY/UNBSS Program: Success Stories
Authors: Gopalswamy, N.; Davila, J.; Thompson, B. J.; Haubold, H. J.
2006ihy..workE..15G Altcode:
The United Nations Office for Outer Space Affairs, through the IHY
secretariat and the United Nations Basic Space Science Initiative
(UNBSSI) is assisting scientists and engineers from all over the world
in participating in the International Heliophysical Year (IHY) 2007. A
major thrust of the IHY/UNBSSI program is to deploy arrays of small,
inexpensive instruments such as magnetometers, radio telescopes, GPS
receivers, etc. around the world to provide global measurements of
ionospheric and heliospheric phenomena. The small instrument program
is a partnership between instrument providers, and instrument hosts in
developing countries. The lead scientist will provide the instruments
(or fabrication plans for instruments) in the array; the host country
will provide manpower, facilities, and operational support to obtain
data with the instrument typically at a local university. Existing data
bases and relevant software tools can be identified to promote space
science activities in developing countries. Extensive data on space
science have been accumulated by a number of space missions. Similarly,
long-term data bases are available from ground based observations. These
data can be utilized in ways different from originally intended for
understanding the heliophysical processes. This paper provides an
overview of the IHY/UNBSS program, its achievements and future plans.

---------------------------------------------------------
Title: Solar and Heliospheric Observatory/Large Angle Spectrometric
Coronagraph Polarimetric Calibration
Authors: Moran, Thomas G.; Davila, Joseph M.; Morrill, Jeff S.; Wang,
Dennis; Howard, Russel
2006SoPh..237..211M Altcode: 2006SoPh..tmp...13M
We present a polarimetric characterization and correction for the Solar
and Heliospheric Observatory/Large Angle Spectrometric Coronagraph
(SOHO/LASCO) C2 and C3 white light coronagraphs. By measuring the
uncorrected polarization angles in solar minimum C2 coronal images,
we have determined that the coronagraph acts as an optical phase
retarder which converts a small fraction of the incoming radiation
polarization from linear to circular. In addition, from the measurements
of polarization angle in C3 coronal images we have determined that
a component of the instrumentally scattered light in that instrument
is polarized. We infer the retardation angle for C2 and compute the
corresponding Mueller matrix, and determine the polarized stray light
spatial profile in C3. The C2 Mueller matrix and C3 polarized stray
light profiles are used to correct for instrumental effects in solar
minimum coronal observations to obtain polarized brightness between
two and thirty-two solar radii, which show deep polar coronal holes
extending to the limit of the field of view.

---------------------------------------------------------
Title: The United Nations Basic Space Science Initiative for IHY 2007
Authors: Gopalswamy, N.; Davila, J. M.; Thompson, B. J.; Haubold, H.
2006IAUSS...5E..47G Altcode:
The United Nations, in cooperation with national and international
space-related agencies and organizations, has been organizing annual
workshops since 1990 on basic space science, particularly for the
benefit of scientists and engineers from developing nations. The United
Nations Office for Outer Space Affairs, through the IHY Secretariat and
the United Nations Basic Space Science Initiative (UNBSSI) will assist
scientists and engineers from all over the world in participating in
the International Heliophysical Year (IHY) 2007. A major thrust of the
IHY/UNBSSI program is to deploy arrays of small, inexpensive instruments
such as magnetometers, radio telescopes, GPS receivers, all-sky cameras,
etc. around the world to provide global measurements of ionospheric
and heliospheric phenomena. The small instrument program is envisioned
as a partnership between instrument providers, and instrument hosts in
developing countries. The lead scientist will provide the instruments
(or fabrication plans for instruments) in the array; the host country
will provide manpower, facilities, and operational support to obtain
data with the instrument typically at a local university. Funds
are not available through the IHY to build the instruments; these
must be obtained through the normal proposal channels. However all
instrument operational support for local scientists, facilities, data
acquisition, etc will be provided by the host nation. It is our hope
that the IHY/UNBSSI program can facilitate the deployment of several of
these networks world wide. Existing data bases and relevant software
tools that can will be identified to promote space science activities
in developing countries. Extensive data on space science have been
accumulated by a number of space missions. Similarly, long-term data
bases are available from ground based observations. These data can be
utilized in ways different from originally intended for understanding
the heliophysical processes. This paper provides an overview of the
IHY/UNBSS program, its achievements and future plans.

---------------------------------------------------------
Title: A Kopp-Pneuman-like Picture of Coronal Mass Ejections
Authors: Spicer, D. S.; Sibeck, D.; Thompson, B. J.; Davila, J. M.
2006ApJ...643.1304S Altcode:
A new coronal mass ejection (CME) picture is described that utilizes
a number of attributes commonly found operating during magnetotail
reconnection events. We first present key observational constraints any
final model of CMEs must explain. We then describe how three-dimensional
reconnection occurs in the magnetotail and how magnetotail reconnection
helps explain a variety of observed CME attributes. We then argue why
reconnection, as usually described in the literature, cannot explain
the particle acceleration process that occurs during the CME/flare
process. Instead we argue that it is the flow fields that are driven
by the relaxation of the magnetic stresses due to reconnection that
are ultimately the cause of particle acceleration. In particular, it
is the electrons that make up the discharging field-aligned currents,
which connect flow field-driven cross field inertial currents in the
high corona with the chromosphere, that are in fact the high-energy
electrons needed to explain flare ribbons and other high-energy
emissions. We compute the expected electron fluxes from these current
systems and find that they are of order those required. In addition,
we discuss betatron acceleration during the dipolarization process
that occurs when the flux rope/CME is ejected and how the hot particles
generated during the dipolarization process can lead to traps in solar
loops, thereby helping to explain long-duration events. Further, we
examine whether particle acceleration by shocks can contribute to the
mix. We also note that our new picture eliminates a number of paradoxes,
specifically elimination of magnetic flux from the Sun and how the Aly
conjecture is not of consequence in our picture. Finally, we examine
what will be needed to numerically simulate our picture of a CME.

---------------------------------------------------------
Title: First Results from EUNIS-06
Authors: Rabin, Douglas M.; Thomas, R. J.; Davila, J. M.
2006SPD....37.0106R Altcode: 2006BAAS...38..216R
The Extreme Ultraviolet Normal-Incidence Spectrograph (EUNIS) sounding
rocket experiment successfully completed its first flight on 12
April 2006 from White Sands Missile Range, obtaining 145 science
images in each of two wavelength channels. EUNIS is designed to
investigate the energetics of the solar corona and hotter transition
region through high-resolution imaging spectroscopy with a rapid
(2-3 second) cadence. The two independent optical systems of EUNIS
simultaneously record spectra over two passbands (170-205 Å and
300-370 Å), each spatially resolved along slit lengths of about
660 arcsec. The longwave channel includes He II 304 Å and strong
lines from Fe XI-XVI. The shortwave passband has a sequence of very
strong Fe IX-XIII lines. Together, the EUNIS telescopes furnish a wide
range of temperature and density diagnostics and enables underflight
calibration of instrumental passbands on the SOHO, TRACE, Solar-B,
and STEREO missions. We present an overview of the science images
from the first flight with emphasis on transient phenomena. The target
was active region NOAA 10871 and adjacent quiet areas. Spectra were
recorded with exposure times as short as 0.1 s, demonstrating that EUNIS
is the most sensitive solar EUV spectrograph in operation, with over 100
times the throughput of its predecessor, the Solar Extreme ultraviolet
Research Telescope and Spectrograph (SERTS). EUNIS is supported
by the NASA Heliophysics Division's Solar &amp; Heliospheric Physics
Supporting Research and Technology and Low Cost Access to Space Program.

---------------------------------------------------------
Title: Ground-Based Low Coronal Electron Temperature And Its Flow
Measurements During The Total Solar Eclipse On 29 March 2006 In Libya
Authors: Reginald, Nelson L.; Davila, J. M.; St. Cyr, C.
2006SPD....37.0611R Altcode: 2006BAAS...38..227R
We have developed ground based instruments that can simultaneously and
globally measure the temperature and the flow speeds of the low coronal
electrons during a total solar eclipse. These two instruments were
successfully operated during the total solar eclipse on 29 March 2006 in
Libya. In one instrument, MACS for Multi Aperture Coronal Spectrometer,
fiber optics at the focal plane of a telescope carried visible coronal
light from different latitudes and heights in the low solar corona to
produce simultaneous spectra. The K-coronal spectra derived from these
spectra can be used to derive the coronal electron temperature and its
flow speed. In the other instrument, ISCORE for Imaging Spectroscopy
of Coronal Electrons, images of the corona were produced through four
filters centered at four wavelength positions in the visible region
each with a bandpass of 50 Angstroms. Here the ratio of intensities of
the K-coronal light from two of the filters would provide information
on the coronal temperature, while the intensities through the other
two filters would yield information on the flow speeds of the coronal
electrons. While these two techniques compliment each other, together
they can produce a global map of the coronal electron temperature and
its flow speed in the low solar corona. Additionally it would also
yield information on the electron acceleration. We are in the process
of integrating this technique using the SolarC coronagraph located at
the Mees Solar Observatory in Haleakala, Hawaii. If this proves to be
successful then these techniques would yield these important coronal
properties on demand.

---------------------------------------------------------
Title: A Sun-to-Earth Campaign Joining Observations from the Great
Observatory with Worldwide Satellite and Ground-Based Resources to
Investigate System Science Frontiers
Authors: Kozyra, J. U.; Shibata, K.; Barnes, R. J.; Basu, S.; Davila,
J. M.; Fox, N. J.; Gopalswamy, N.; Kuznetsova, M. M.; Pallamraju,
D.; Paxton, L. J.; Ridley, A.; Weiss, M.; Young, C. A.; Zanetti, L. J.
2006AGUSMSM23A..03K Altcode:
An Internet-based cross-disciplinary analysis campaign that will
make heavy use of Great Observatory missions as well as international
satellite and ground-based assets is being undertaken with joint support
from the CAWSES, IHY, LWS, and ICESTAR programs planned for late
April or early May 2006. An evolving list of open science questions
that serve as sun-to-Earth focus areas for the worldwide campaign
were identified during a small interdisciplinary CAWSES workshop
at Stanford University in December 2005 as well as during a joint
CAWSES/ICESTAR session at the CEDAR meeting in Boulder the preceding
summer. The analysis campaign will take place over the Internet in the
form of virtual poster sessions with message boards and monitors that
summarize the important science issues and new results daily. Poster
authors will be asked to closely monitor their message boards during
the day of their poster session as well as the following day. Outreach
to other disciplines and international students will take the form of
tutorial talks that place campaign science issues into the context of
the current state of knowledge in each discipline area. Global models
and data sets (TEC, magnetometer maps, ULF wave maps, assimilative
models, MHD model outputs, continuous solar images) will be available
to provide context for local and regional observations. The Community
Coordinated Data Center (CCMC) is developing a small number of new data
display formats that extract data from global models and place it in
the same format as the observations either for ground-based stations
or along satellite tracks. Other ideas being explored include real
time upload of additional posters in response to issues raised during
the poster session, library of related articles, reference archive of
observations, etc. A summary of which aspects and/or tools worked and
which were less useful will be presented.

---------------------------------------------------------
Title: Science Plans for the International Heliophysical Year
Authors: Davila, J. M.; Gopalswamy, N.; Harrison, R. A.; Stamper,
R.; Briand, C.; Potgieter, M. S.
2006AGUSM.U34A..04D Altcode:
On October 4, 1957, only 53 years after the beginning of flight in Kitty
Hawk, the launch of Sputnik 1 marked the beginning of the space age;
as mankind took the first steps to leaving the protected environment of
Earth's atmosphere. Discovery of the radiation belts, the solar wind,
and the structure of Earth's magnetosphere prepared the way for the
inevitable human exploration to follow. Soon, Cosmonauts and Astronauts
orbited Earth, and then in 1969, Astronauts landed on the Moon. Today
a similar story is unfolding, the spacecraft Voyager has crossed the
termination shock, and will soon leave the heliosphere. For the first
time, man will begin to explore the local interstellar medium. It is
inevitable that, during the next 50 years, exploration of the solar
system including the Moon, Mars and the outer planets will be the
focus of the space program, and like 50 years ago, unmanned probes
will lead the way, followed by human exploration. The International
Geophysical Year (IGY) of 1957, a broad-based and all-encompassing
effort to push the frontiers of geophysics, resulted in a tremendous
increase of knowledge in space physics, Sun-Earth Connection, planetary
science and the heliosphere in general. Now, 50 years later, we have
the unique opportunity to further advance our knowledge of the global
heliosphere and its interaction with the interstellar medium through
the International Heliophysical Year (IHY) in 2007, and to raise
public awareness of space physics. This presentation will focus on
global science planning efforts and campaigns for all participating
IHY nations.

---------------------------------------------------------
Title: Planning the International Heliophysical Year (IHY)
Authors: Davila, Joseph M.; Thompson, Barbara J.; Gopalswamy, Nat
2006UNPSA..17...37D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The SECCHI Experiment on the STEREO Mission
Authors: Howard, R.; Moses, D.; Vourlidas, A.; Davila, J.; Lemen, J.;
Harrison, R.; Eyles, C.; Defise, J. -M.; Bothmer, V.; Ravet, M. -F.;
Secchi Team
2006cosp...36..870H Altcode: 2006cosp.meet..870H
The Sun Earth Connection Coronal and Heliospheric Investigation SECCHI
on the NASA Solar Terrestrial Relations Observatory STEREO mission
is a suite of remote sensing instruments consisting of an extreme
ultraviolet EUV imager two white light coronagraphs and two telescopes
that comprise the heliospheric imager SECCHI will observe coronal mass
ejections CMEs from their birth at the sun through the corona and into
the heliosphere A complete instrument suite is being carried on each
of the two STEREO spacecraft which will provide the first sampling of
a CME from two vantage points The spacecraft will orbit the Sun one
Ahead of the Earth and the other Behind each separating from Earth at
about 22 degrees per year The varying separation means that we will
have different observational capabilities as the spacecraft separate
and therefore differing science goals The primary science objectives
all are focused on understanding the physics of the CME process -
their initiation 3D morphology propagation interaction with the
interplanetary medium and space weather effects By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time answers to some
of the outstanding questions will be obtained STEREO follows the very
successful SOHO mission SOHO s success was primarily due to the highly
complementary nature of the instruments but it was

---------------------------------------------------------
Title: Preparing for the International Heliophysical Year (IHY) 2007
Authors: Davila, J. M.; Gopalswamy, N.; Thompson, B. J.
2006ilws.conf..231D Altcode:
The International Geophysical Year (IGY) of 1957, a broad-based and
all-encompassing effort to push the frontiers of geophysics, resulted
in a tremendous increase of knowledge in space physics, Sun-Earth
Connection, planetary science and the heliosphere in general. Now, 50
years later, we have the unique opportunity to advance our knowledge of
the global heliosphere and its interaction with planetary bodies and
the interstellar medium through the International Heliophysical Year
(IHY) in 2007. This will be an international effort, which will raise
public awareness of space physics.

---------------------------------------------------------
Title: The IHY/United Nations Distributed Observatory Development
Program
Authors: Haubold, H.; Thompson, B. J.; Al-Naimiy, H.; Davila, J. M.;
Gopalswamy, N.; Groves, K.; Scherrer, D.
2006cosp...36.3304H Altcode: 2006cosp.meet.3304H
A major thrust of the International Heliophysical Year IHY is to
deploy arrays of small inexpensive instruments such as magnetometers
radio antennas GPS receivers all-sky cameras etc around the world
to provide global measurements of ionospheric magnetospheric and
heliospheric phenomena This program is a collaboration between the IHY
and the United Nations Basic Space Science Initiative UNBSSI which has
been dedicated to the IHY through 2009 The small instrument program
consists of a partnership between instrument providers and instrument
host countries The lead scientist provides the instrumentation or
fabrication plans for instruments in the array the host country
provides manpower facilities and operational support to obtain data
with the instrument typically at a local university This program has
been active in deploying instrumentation developing plans for new
instrumentation and identifying educational opportunities for the host
nations in association with this program We will discuss the program
s status significant deployment activities and plans for 2007-2009

---------------------------------------------------------
Title: International coordinated efforts for IHY 2007
Authors: Gopalswamy, N.; Davila, J.; Thompson, B.
2006cosp...36.2743G Altcode: 2006cosp.meet.2743G
The International Heliophysical Year IHY in 2007 marks the enormous
progress made since the International Geophysical Year IGY in 1957
The philosophy behind IHY is similar to that of IGY in studying the
environment of our habitat except that the scope has increased to the
physical space extending to the interstellar medium This paper describes
the international organization of the IHY and planning for a successful
program in 2007 In particular we describe the national regional and
global efforts in pooling the resources to address the universal
processes that govern the solar system and its interaction with the
surrounding medium The efforts include identifying science questions of
immediate concern and the data sets needed to address these questions
The data will be acquired using a truly distributed observatory
consisting of all the ground and space-based instruments that exist
today and those to be constructed before 2007 The international planning
also involves coordinating with the United Nations which through its
Basic Space Science Initiative is facilitating the participation of the
developing nations in the IHY program An update of the current status
of the planning activities at the international level will be presented

---------------------------------------------------------
Title: The International Heliophysical Year (IHY) 2007
Authors: Davila, J. M.; Thompson, B. J.; Gopalswamy, N.
2006AfrSk..10....4D Altcode:
The International Geophysical Year (IGY) of 1957, a broad-based
and all-encompassing effort to push the frontiers of geophysics,
resulted in a tremendous increase of knowledge in space physics,
the Sun-Earth connection, planetary science, and the heliosphere in
general. Now, fifty years later, we have the unique opportunity to
advance our knowledge of the global heliosphere and its interaction with
planetary bodies and the interstellar medium through the International
Heliophysical Year (IHY) in 2007. This will be an international effort
which will raise public awareness of space physics. Because of its
unique geographic position, Africa is well-positioned to play a
critical role.

---------------------------------------------------------
Title: A 3D Numerical Toolkit for Modeling the Heliosphere
Authors: Spicer, D. S.; Davila, J. M.; Ofman, L.
2005AGUFMSH11A0258S Altcode:
We present results from a numerical toolkit that can be used by
observers, analysts, and modelers to study solar activity and its effect
on the heliosphere. The core of the toolkit is a 3D AMR unstructured
mesh high order Godunov code that was orginally designed to model the
magnetospheric-ionospheric system. We plan to make the code available
in portable code form through the CCMC.

---------------------------------------------------------
Title: First Results From EUNIS 2005
Authors: Rabin, D. M.; Thomas, R. J.; Davila, J. M.; Brosius, J. W.;
Swartz, M.; Jordan, S. D.
2005AGUFMSH41B1122R Altcode:
The Extreme Ultraviolet Normal-Incidence Spectrograph (EUNIS) is
a sounding rocket experiment to investigate the energetics of the
solar corona and hotter transition region through high-resolution
imaging spectroscopy with a rapid (2 second) cadence. Pre-flight
characterization of throughput has demonstrated that EUNIS is the
most sensitive solar EUV spectrograph in existence, having over
100 times the throughput of its predecessor, the Solar Extreme
ultraviolet Research Telescope and Spectrograph (SERTS). We report
initial results from the first flight in November 2005 from White
Sands Missile Range. The main scientific goal of the first EUNIS
flight is to extend the investigation of transient phenomena, such as
nanoflares and blinkers, to shorter timescales than has been possible
with previous EUV spectrographs. The two independent optical systems
of EUNIS record spatially co-aligned spectra over two passbands
(170--205 Å and 300--370 Å) simultaneously with spectral resolution
of 60 mÅ or 120 mÅ, respectively. The longwave passband includes
He II 304 Å and strong lines from Fe XI--XVI. The shortwave passband
has a sequence of very strong Fe IX--XIII lines. Together, the EUNIS
telescopes furnish a wide range of temperature and density diagnostics
and enable underflight calibration of instrumental passbands on the
SOHO, TRACE, Solar-B, and STEREO missions.

---------------------------------------------------------
Title: Multi Aperture Coronal Spectrographic Technique for
Simultaneous and Global Measurements of the Coronal Electron
Temperature and its Bulk Flow Speed in the Low Solar Corona
Authors: Reginald, N. L.; Davila, J. M.; St. Cyr, C. C.
2005AGUFMSH41B1123R Altcode:
We describe a spectrographic technique that allows for the simultaneous
and global measurements of the coronal electron temperature and its
bulk flow speed in the low solar corona. This information is obtained
through the measurement of the K-coronal spectrum in the 3900-4400
Angstrom region, whose shape is determined by the electron temperature
and its bulk flow speed. The Multi Aperture Coronal Spectrograph
allows for the simultaneous measurement of the K-coronal spectra all
around the low solar corona (less than 2 solar radii). Since most
of the coronal temperature and solar wind speed measurements in the
literature are due to ion-based techniques, it is very important to
verify that the electron-based measurements compliment the ion-based
measurements. This is particularly important owing to the fact that
electrons are almost 2000 times lighter than the protons. And if
the electron-based measurement do not compliment the proton-based
measurement then it is reasonable to explore the possibilities of these
two oppositely charged particles being subject to different physical
mechanisms in the solar corona.

---------------------------------------------------------
Title: Distributed Instrumentation Deployment During the IHY
Authors: Davila, J. M.; Thompson, B. J.; Gopalswamy, N.
2005AGUFMSM21A0347D Altcode:
A major thrust of the International Heliophysical Year (IHY) is to
deploy arrays of small, inexpensive instruments such as magnetometers,
radio antennas, GPS receivers, all-sky cameras, etc. around the
world to provide global measurements of ionospheric and heliospheric
phenomena. This program is a collaboration between the IHY and the
United Nations Basic Space Science (UNBSS) program, which has been
dedicated to the IHY through 2009. The small instrument program is
envisioned as a partnership between instrument providers, and instrument
host countries. The lead scientist will provide the instruments (or
fabrication plans for instruments) in the array; the host country
will provide manpower, facilities, and operational support to obtain
data with the instrument typically at a local university. Instrument
operational support for local scientists, facilities, data acquisition,
etc will be provided by the host nation.

---------------------------------------------------------
Title: High-frequency Alfvén waves in multi-ion coronal plasma:
Observational implications
Authors: Ofman, L.; Davila, J. M.; Nakariakov, V. M.; ViñAs, A. -F.
2005JGRA..110.9102O Altcode: 2005JGRA..11009102O
We investigate the effects of high-frequency (of order ion
gyrofrequency) Alfvén and ion-cyclotron waves on ion emission lines
by studying the dispersion of these waves in a multi-ion coronal
plasma. For this purpose we solve the dispersion relation of the
linearized multifluid and Vlasov equations in a magnetized multi-ion
plasma with coronal abundances of heavy ions. We also calculate the
dispersion relation using nonlinear one-dimensional hybrid kinetic
simulations of the multi-ion plasma. When heavy ions are present the
dispersion relation of parallel propagating Alfvén cyclotron waves
exhibits the following branches (in the positive Ω - k quadrant):
right-hand polarized nonresonant and left-hand polarized resonant
branch for protons and each ion. We calculate the ratio of ion to
proton velocities perpendicular to the direction of the magnetic field
for each wave modes for typical coronal parameters and find strong
enhancement of the heavy ion perpendicular fluid velocity compared
with proton perpendicular fluid velocity. The linear multifluid cold
plasma results agree with linear warm plasma Vlasov results and with
the nonlinear hybrid simulation model results. In view of our findings
we discuss how the observed nonthermal line broadening of minor ions
in coronal holes may relate to the high-frequency wave motions.

---------------------------------------------------------
Title: Coronal electron velocity and temperature from Thomson
scattered visible light
Authors: Davila, Joseph M.; Reginald, Nelson L.; St. Cyr, O. C.
2005SPIE.5901...67D Altcode:
The measurements of velocity and temperature of coronal electrons are of
immense importance to the study of coronal dynamics, especially in the
low solar corona. In this lies interesting physics yet to fully explain
the theoretical reasoning for the million degree hot coronal plasma and
the cause for the initial acceleration of this coronal plasma. In this
regard it would be equally important if both of these coronal electron
parameters, namely the velocity and the temperature of these coronal
electrons, could be determined simultaneously and globally all around
the low solar corona. The purpose of this paper is twin fold. First,
to lay out an instrumental procedure that allows for the measurement
of a coronal signature that could measure all around the low solar
corona simultaneously. Second, to describe a theoretical procedure
that allows for deriving both the coronal electron temperature and
its bulk flow velocity from the measured coronal signature.

---------------------------------------------------------
Title: Fe XI Emission Lines in a High-Resolution Extreme-Ultraviolet
Active Region Spectrum Obtained by the Solar Extreme Ultraviolet
Research Telescope and Spectrograph
Authors: Keenan, F. P.; Aggarwal, K. M.; Ryans, R. S. I.; Milligan,
R. O.; Bloomfield, D. S.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2005ApJ...624..428K Altcode: 2005astro.ph..4106K
New calculations of radiative rates and electron impact excitation cross
sections for Fe XI are used to derive emission-line intensity ratios
involving 3s23p4-3s23p33d
transitions in the 180-223 Å wavelength range. These ratios are
subsequently compared with observations of a solar active region
obtained during the 1995 flight of the Solar Extreme Ultraviolet
Research Telescope and Spectrograph (SERTS). The version of SERTS flown
in 1995 incorporated a multilayer grating that enhanced the instrumental
sensitivity for features in the ~170-225 Å wavelength range, observed
in second order between 340 and 450 Å. This enhancement led to the
detection of many emission lines not seen on previous SERTS flights,
which were measured with the highest spectral resolution (0.03 Å)
ever achieved for spatially resolved active region spectra in this
wavelength range. However, even at this high spectral resolution,
several of the Fe XI lines are found to be blended, although the sources
of the blends are identified in the majority of cases. The most useful
Fe XI electron density diagnostic line intensity ratio is I(184.80
Å)/I(188.21 Å). This ratio involves lines close in wavelength
and free from blends, and it varies by a factor of 11.7 between
Ne=109 and 1011 cm-3
yet shows little temperature sensitivity. An unknown line in the
SERTS spectrum at 189.00 Å is found to be due to Fe XI, the first
time (to our knowledge) this feature has been identified in the solar
spectrum. Similarly, there are new identifications of the Fe XI 192.88,
198.56, and 202.42 Å features, although the latter two are blended
with S VIII/Fe XII and Fe XIII, respectively.

---------------------------------------------------------
Title: STEREO's Interactions With the Virtual Solar and Heliospheric
Observatories
Authors: Thompson, W. T.; Kaiser, M. L.; Kucera, T. A.; Davila, J. M.;
Hourcle, J.; Schroeder, P.
2005AGUSMSH43B..06T Altcode:
STEREO (Solar TErrestrial RElations Observatory) will observe
the Sun and solar storms with two nearly identical spacecraft in
heliocentric orbits, one ahead of Earth, the other trailing behind. This
multi-spacecraft approach provides both stereoscopic views of the solar
corona with the imaging telescopes, and multipoint observations of the
heliosphere with the in-situ and radio experiments. Combined analysis
with other viewpoints will be essential to STEREO science. Data archived
at the NASA/GSFC STEREO Science Center will be completely integrated
into the Virtual Solar Observatory (VSO), with shared resources and
personnel. The in-situ and radio data will also be directly available
through the Virtual Heliospheric Observatory (VHO). This dual system
will ensure the maximum visibility of STEREO data to both the imaging
and particle/field communities. Linkages between the VSO and VHO will
allow all the STEREO data to be available through either system. Event
lists will enhance the data set, and ease the data selection process.

---------------------------------------------------------
Title: Putting the Rubber to the Road: The Whos, Whys and Hows of
the International Heliophysical Year 2007
Authors: Thompson, B. J.; Davila, J. M.; Drobnes, E.; Gopalswamy,
N.; Wesenberg, R. P.
2005AGUSM.U23A..07T Altcode:
In 1957 a program of international research, inspired by the
International Polar Years of 1882 and 1932, was organized as the
International Geophysical Year (IGY) to study global phenomena
of the Earth and geospace. Fifty years later, the world's science
community will again come together for international programs of
scientific collaboration: the International Heliophysical Year
(IHY), the electronic Geophysical Year (eGY), and the International
Polar Year (IPY) 2007. This time, research will extend out into the
heliosphere to focus on solar-terrestrial-planetary interactions. The
ambitious plans for the IHY, eGY and IPY incorporate the activities
of scientists in 191 nations, the "IGY Gold" Historical Preservation
initiative, a series of coordinated campaigns involving more than
100 instruments and models, education and public outreach programs,
a developing nations instrument development program, and opportunities
for supported research worldwide. The presentation will focus on the
efforts and operations which will make these activities possible.

---------------------------------------------------------
Title: Scientific Studies Using MACS: Coronal Reconnection
Measurements and Solar Wind Acceleration Diagnostics
Authors: St. Cyr, O. C.; Davila, J. M.; Reginald, N. L.; Brosius,
J.; Moran, T.
2005AGUSMSP51B..03S Altcode:
We have developed an instrument and an observational technique that
exploits the shape of the K-coronal visible spectrum, 380-450 nm,
to determine simultaneously both the thermal electron temperature and
its bulk flow speed (see Reginald et al poster, this conference). For
a given electron density along the line of sight, the shape of the
K-coronal visible spectrum is influenced by the thermal electron
temperature and its bulk flow speed. The bulk flow speed of the coronal
electrons in the solar wind causes a Doppler-shift in the shape of
the K-coronal spectrum depending on the magnitude of the speed. The
simple reason for the red shift is that the wavelength-independent
Thomson scattered coronal electrons observe a red-shifted photosphere
as they move away from the Sun at the bulk flow speed. In addition,
recent models have shown that identical streamers could be distinguished
through their influence on the shape of the K-coronal visible spectrum
in different wavelength regions. Modeling efforts have expanded to
include a scenario where the observing line of sight passes through
a coronal reconnection area. Using realistic parameters for the
reconnection, and assuming that it produces bulk electron flows both
toward and away from the Sun, our preliminary results indicate that the
resulting red and blue-shifted K-coronal spectrum should be detectable
with the MACS instrument.

---------------------------------------------------------
Title: MACS for global measurements of the thermal electron
temperature and its bulk flow speed in the low solar corona through
ground based experiments
Authors: Reginald, N. L.; Davila, J. M.; St. Cyr, C.; Brosius, J. W.;
Moran, T.; Thomas, R.
2005AGUSMSP51B..04R Altcode:
The determination of the radial and latitudinal temperature and wind
profiles of the solar corona is of immense importance in understanding
the coronal heating mechanism and the dynamics of the coronal
features. We have built MACS-1 (Multi Aperture Coronal Spectrometer);
a fiber optic based spectrograph, to study the coronal properties
during the total solar eclipses of August 1999 in Elazig, Turkey and
June 2001 in Lusaka, Zambia, through the measurement of the K-coronal
spectrum. In these experiments we have successfully demonstrated the
feasibility of simultaneously measuring both the thermal electron
temperature and its bulk flow speed at multiple locations on the solar
corona. Measurement of these properties radially in the solar corona
could provide valuable information on the solar wind acceleration in the
low corona. We are now in the process of conducting a similar experiment
on the low solar corona with an advanced spectrograph MACS-2 interfaced
with the SolarC coronagraph at the Mees Solar Observatory in Haleakala,
Hawaii. This if proven successful would provide an ability to measure
simultaneously and globally the above coronal properties on demand.

---------------------------------------------------------
Title: Emission lines of FeXV in spectra obtained with the Solar
Extreme-Ultraviolet Research Telescope and Spectrograph
Authors: Keenan, F. P.; Aggarwal, K. M.; Milligan, R. O.; Ryans,
R. S. I.; Bloomfield, D. S.; Srigengan, V.; O'Mullane, M. G.; Lawson,
K. D.; Msezane, A. Z.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2005MNRAS.356.1592K Altcode: 2004MNRAS.tmp..752K
Recent R-matrix calculations of electron impact excitation rates
in Mg-like FeXV are used to derive theoretical emission-line ratios
involving transitions in the 243-418 Åwavelength range. A comparison
of these with a data set of solar active region, subflare and off-limb
spectra, obtained during rocket flights by the Solar Extreme-Ultraviolet
Research Telescope and Spectrograph (SERTS), reveals generally
very good agreement between theory and observation, indicating that
most of the FeXV emission lines may be employed with confidence as
electron density diagnostics. In particular, the 312.55-Åline of
FeXV is not significantly blended with a CoXVII transition in active
region spectra, as suggested previously, although the latter does
make a major contribution in the subflare observations. Most of the
FeXV transitions which are blended have had the species responsible
clearly identified, although there remain a few instances where
this has not been possible. We briefly address the long-standing
discrepancy between theory and experiment for the intensity ratio of
the 3s21S-3s3p 3P1 intercombination
line at 417.25 Åto the 3s21S-3s3p 1P resonance
transition at 284.16 Å.

---------------------------------------------------------
Title: Calibration Results for the COR-1 Coronagraph on STEREO/SECCHI
Authors: Thompson, W. T.; Davila, J. M.; Mentzell, E.; Korendyke, C.
2004AGUFMSH21B0408T Altcode:
COR-1 is the inner coronagraph of the Sun Earth Connection Coronal
and Heliospheric Investigation (SECCHI) instrument suite aboard the
two STEREO spacecraft. COR-1 is a classic Lyot internally occulting
coronagraph, observing the solar corona in broadband red light around
656 nm, from 1.35 to 4 solar radii. A linear polarizer is used to
suppress scattered light, and to extract the polarized brightness
signal from the solar corona. Calibration was performed in the Naval
Research Laboratory vacuum tunnel facility previously used for the LASCO
experiment aboard SOHO. We report on the results for scattered light,
photometric calibration, resolution, and polarization. All performance
requirements are met or exceeded. Based on these results, we demonstrate
that COR-1 will be able to carry out its scientific mission.

---------------------------------------------------------
Title: The Effects of Streamers on the Shape of the K-Coronal Spectrum
Authors: Reginald, Nelson L.; Davila, Joseph M.; Cyr, O. C. St.
2004SoPh..225..249R Altcode:
We conducted an experiment in conjunction with the total solar eclipse
of 21 June 2001 in Lusaka, Zambia, to obtain the K-coronal spectrum
simultaneously from multiple locations on the solar corona. Then we
matched the observed K-coronal spectra with the modeled K-coronal
spectra to determine the coronal electron temperature and its bulk
flow speed. Here the models assumed a symmetric and isothermal corona
with the coronal electron flowing away from the Sun at a constant flow
speed. We were able to make remarkable matches between the observations
and the models. In this paper we will try to explain how the anomalies
in the matches could be accounted for with the introduction of streamers
in the K-coronal spectral models.

---------------------------------------------------------
Title: Three-Dimensional Polarimetric Imaging of Coronal Mass
Ejections
Authors: Moran, Thomas G.; Davila, Joseph M.
2004Sci...305...66M Altcode:
We present three-dimensional reconstructions of coronal mass ejections
(CMEs), which were obtained through polarization analysis of single-view
images recorded with the use of the Large Angle and Spectrometric
Coronagraph (LASCO) C2 coronagraph on board the Solar and Heliospheric
Observatory (SOHO) spacecraft. Analysis of a loop-like CME shows a
complex three-dimensional structure centered at 40° from the plane
of the sky, moving radially at 250 kilometers/second. Reconstruction
of two halo CMEs suggests that these events are expanding loop arcades.

---------------------------------------------------------
Title: Development of MHD Wave Diagnostic and Models of Coronal
Active Regions
Authors: Ofman, L.; Thompson, B. J.; Davila, J. M.
2004AAS...204.9504O Altcode: 2004BAAS...36..826O
We investigate the generation, propagation, and damping of MHD waves in
active regions, with the goal to develop a diagnostic tool of active
region structure, dynamics, and stability. We used 3D MHD model to
study the generation and the propagation of EIT waves in a simple
model of an active regions, and the interaction of EIT waves with
the active region magnetic field. We model the oscillation of active
region loops numerically using the 3D MHD model active regions. Such
oscillations have been recently observed by TRACE. We use photospheric
magnetograms as the boundary conditions for the magnetic field model,
and construct an initial field using force-free extrapolation. Finite
plasma temperature, density, and gravity are included in the model. We
construct loop density structures in the model, guided by TRACE and EIT
observations in the EUV. We demonstrate that by comparing the results
of the MHD models of waves in an active region to observations we will
be able to construct a diagnostic tool for the physical properties of
the active regions, such as magnetic field and density structure.

---------------------------------------------------------
Title: Polarimetric Three-Dimensional Imaging of Coronal Mass
Ejections
Authors: Moran, T.; Davila, J.
2004AAS...204.1808M Altcode: 2004BAAS...36..683M
We present the first three-dimensional reconstructions of coronal mass
ejections (CMEs), which were obtained through polarization analysis
of images recorded using the LASCO C2 coronagaph on board the SOHO
spacecraft. The ratio of polarized-to-unpolarized electron-scattered
emission is primarily a function of the angle between a radial through
the scattering point and the plane-of-the-sky. Since the projected
distance from sun center to the scattering point can be obtained from
total brightness images, the brightness ratio measurement determines
the point's distance from sun center and from the plane-of-the-sky. A
topographical map is computed from the brightness ratio, from which
'top' and 'side' views of the CME are constructed. Three dimensional
structure, position and velocity are computed for two CMEs, moving at
45 degrees and at 7 degrees from the Earth-Sun line. Analysis of the
Earth-directed, or 'Halo' CME, shows a bilateral symmetry, indicating
a loop arcade structure. The central loops are oriented vertically,
while those at the ends tilt away from the arcade midplane. This work
was funded by the NASA SR &amp; T program.

---------------------------------------------------------
Title: Technique for simultaneous and global measurements of coronal
electron temperature and solar wind speed in the lower corona
Authors: Reginald, N. L.; Davila, J. M.; St. Cyr, O. C.; Brosius, J. W.
2004AAS...204.7302R Altcode: 2004BAAS...36..800R
We have successfully demonstrated the feasibility of measuring both the
coronal electron temperature and its radial flow speed simultaneously at
multiple locations in the lower solar corona. This experiment was
conducted in conjunction with the total solar eclipse of 21 June 2001
using multiple fiber optic spectroscopic technique. Here one end of
the multiple fibers was located at fixed radii at different latitudes
in the focal plane of the telescope. The coronal light gathered by
these fibers was then simultaneously fed to a spectroscope. The
required results were obtained by isolating the K-coronal spectrum in
the 350-450 nm regions. Our future plans are to locate fibers along
radii to measure the acceleration of the electron flow speed in the
lower corona. For this we intend to use this methodology in conjunction
with the SolarC coronagraph at the Mees Solar Observatory in Haleakala,
Hawaii. This would enable us to overcome the time constraints associated
with eclipse observations. The new design for the spectrograph
envisages all reflective optics to minimize scattering, specialized
chemical coatings to maximize capture of signal in the 350-450 nm
regions and to pass the beam through a polarizer to account for the
F-coronal component.

---------------------------------------------------------
Title: A Comparison of Theoretical Si &lt;Emphasis
Type="SmallCaps"&gt;VIII&lt;/Emphasis&gt; Emission Line Ratios with
Observations from Serts
Authors: Keenan, F. P.; Katsiyannis, A. C.; Ramsbottom, C. A.; Bell,
K. L.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2004SoPh..219..251K Altcode:
Recent R-matrix calculations of electron impact excitation rates in
N-like Si VIII are used to derive theoretical emission line intensity
ratios involving 2s22p3-2s2p4
transitions in the 216-320 Å wavelength range. A comparison of these
with an extensive dataset of solar active region, quiet-Sun, sub-flare
and off-limb observations, obtained during rocket flights of the Solar
EUV Research Telescope and Spectrograph (SERTS), indicates that the
ratio R1= I(216.94 Å)/I(319.84 Å) may provide a usable
electron density diagnostic for coronal plasmas. The ratio involves
two lines of comparable intensity, and varies by a factor of about
5 over the useful density range of 108-1011
cm−3. However R2= I(276.85 Å)/I(319.84 Å)
and R3=I(277.05 Å)/I(319.84 Å) show very poor agreement
between theory and observation, due to the severe blending of the 276.85
and 277.05 Å lines with Si VII and Mg VII transitions, respectively,
making the ratios unsuitable as density diagnostics. The 314.35 Å
feature of Si VIII also appears to be blended, with the other species
contributing around 20% to the total line flux.

---------------------------------------------------------
Title: International heliophysical year: a program of global research
continuing the tradition of previous international years
Authors: Davila, Joseph M.; Poland, Arthur I.; Harrison, Richard A.
2004AdSpR..34.2453D Altcode:
In 1957 a program of international research, inspired by the
International Polar Years of 1882-1883 and 1932-1933, was organized
as the International Geophysical Year (IGY) to study global phenomena
of the Earth and geospace. The IGY involved about 60,000 scientists
from 66 nations, working at thousands of stations from pole to pole,
in an effort to obtain simultaneous, global observations on Earth
and in space. There had never been anything like it before. The 50th
anniversary of the International Geophysical Year will occur in 2007. We
propose to organize an international program of scientific collaboration
for this time period called the International Heliophysical Year
(IHY). Like its predecessors, the IHY will focus on fundamental global
questions of Earth science.

---------------------------------------------------------
Title: The Secchi Experiment on the Stereo Mission
Authors: Howard, R.; Moses, D.; Socker, D.; Cook, J.; Davila, J.;
Lemen, J.; Harrison, R.; Eyles, C.; Waltham, N.; Defise, J. -M.
2004cosp...35.3893H Altcode: 2004cosp.meet.3893H
The Sun Earth Connection Coronal and Heliospheric Investigation
(SECCHI) on the NASA Solar Terrestrial Relations Observatory (STEREO)
mission is a suite of remote sensing instruments consisting of two
white light coronagraphs, an extreme ultraviolet (EUV) imager, and
a heliospheric imager. SECCHI will observe coronal mass ejections
(CMEs) from their birth at the sun, through the corona and into the
heliosphere. A complete instrument suite is being carried on each
of the two STEREO spacecraft, which will provide the first sampling
of a CME from two vantage points. The spacecraft will orbit the Sun,
one ahead of the Earth and the other behind, separating from Earth at
about 22 degrees per year. The varying separation means that we will
have different observational capabilities as the spacecraft separate
and therefore differing science goals. The primary science objectives
all are focused on understanding the physics of the CME process -
their initiation, 3D morphology, propagation, interaction with the
interplanetary medium and space weather effects. By observing the CME
from multiple viewpoints with UV and coronagraphic telescopes and by
combining these observations with radio and in-situ observations from
the other instruments on STEREO as well as from other satellites and
ground based observatories operating at the same time, answers to some
of the outstanding questions will be obtained.

---------------------------------------------------------
Title: Alfvén Waves in Multi-ion Coronal Plasma: Observational
Implications
Authors: Ofman, L.; Nakariakov, V. M.; Davila, J. M.
2003AGUFMSH11D1129O Altcode:
We investigate low-frequency Alfvén waves in a multi-ion coronal plasma
by deriving the dispersion relation of the linearized three-fluid
equations in magnetized plasma with coronal parameters. We study
the effect of collisions on the velocity amplitude of minor ions due
to the Alfvén waves compared to the proton wave amplitude. We find
that in the collisionless plasma the minor ion velocity is reduced
by the factor Z/A compared to protons, where Z is the ion charge,
and A is mass in units of proton mass. When the collision frequency
is much larger then the Alfvén wave frequency the velocity amplitude
of the minor ions is equal to the proton velocity amplitude. We show
the effects of minor ions and collisions on the dispersion relation
of Alfvén waves in the three fluid plasma. In view of our results we
show how the observed nonthermal line broadening of minor ions relates
to the wave motions of protons as a function of heliocentric distance,
and the plasma physical parameters.

---------------------------------------------------------
Title: Electron Temperature and Speed Measurements in the Low Solar
Corona: Results From the 2001 June Eclipse
Authors: Reginald, Nelson L.; Cyr, O. C. St.; Davila, Joseph M.;
Brosius, Jeffrey W.
2003ApJ...599..596R Altcode:
We present measurements of electron temperature and bulk flow speed
low in the solar corona derived from white-light spectra obtained
during the total solar eclipse of 2001 June 21. Observations were
obtained at two locations in the solar corona, one within a helmet
streamer at the east limb and the second in a streamer cluster
in the southwest. Both points were at an altitude of about 1.1
Rsolar from the solar center. The east limb and southwest
locations yielded electron temperatures of 0.96+/-0.05 and 1.2+/-0.2
MK and bulk flow speeds of 72.0+281.0-72.0
and 257.0+443.0-257.0 km s-1,
respectively. These measurements are unique in that they simultaneously
provide both the electron temperature and its bulk flow speed;
few previous measurements of electron parameters in the corona are
available. The results presented here demonstrate the potential for
this technique: if the instrument were used with a coronagraph, it
would provide routine synoptic maps of electron temperature and bulk
flow speed.

---------------------------------------------------------
Title: Development of 2D MHD Self-Consistent Empirical Model of the
Corona and Solar Wind
Authors: Sittler, E. C.; Ofman, L.; Gibson, S.; Holzer, T.; Davila,
J.; Guhathakurta, M.
2003AGUFMSH42D..07S Altcode:
We are developing a 2D MHD self-consistent empirical model of
the solar corona and solar wind. We constrain the solution using
empirically determined estimates of the effective pressure for the
momentum equation and effective heat flux for the energy equation
provided from coronagraph data and Ulysses plasma and magnetic field
data. Our solutions are steady state and do not use a polytrope which
we know is not valid in the solar corona. We have been able to achieve
preliminary convergence. We will present the results of an error
analysis. Our results are presently only valid during solar minimum,
but are generalizing so it can be used during the transition toward
solar maximum (i.e., three current sheets). We will also present some
preliminary results which will allow us to apply our solutions to
solar maximum conditions.

---------------------------------------------------------
Title: Development of Multidimensional MHD Model for the Solar Corona
and Solar Wind
Authors: Sittler, E. C.; Ofman, L.; Gibson, S.; Guhathakurta, M.;
Davila, J.; Skoug, R.; Fludra, A.; Holzer, T.
2003AIPC..679..113S Altcode:
We are developing a time stationary self-consistent 2D MHD model of
the solar corona and solar wind that explicitly solves the energy
equation, using a semi-empirical 2D MHD model of the corona to provide
an empirically determined effective heat flux qeff (i.e., the term
effective means the possible presence of wave contributions). But,
as our preliminary results indicate, in order to achieve high
speed winds over the poles we also need to include the empirically
determined effective pressure Peff as a constraint in the momentum
equation, which means that momentum addition by waves above 2 RS are
required to produce high speed winds. At present our calculations do
not include the Peff constraint. The estimates of Peff and qeff come
from the semi-empirical 2D MHD model of the solar corona by Sittler
and Guhathakurta (1999a,2002) which is based on Mk-III, Skylab and
Ulysses observations. For future model development we plan to use SOHO
LASCO, CDS, EIT, UVCS and Ulysses data as constraints for our model
calculations. The model by Sittler and Guhathakurta (1999a, 2002) is
not a self-consistent calculation. The calculations presented here is
the first attempt at providing a self-consistent calculation based on
empirical constraints.

---------------------------------------------------------
Title: Emission lines of Na-like ions in spectra obtained with the
Solar EUV Research Telescope and Spectrograph (SERTS)
Authors: Keenan, F. P.; Katsiyannis, A. C.; Brosius, J. W.; Davila,
J. M.; Thomas, R. J.
2003MNRAS.342..513K Altcode:
Theoretical emission-line ratios involving transitions in the 236-412
Å wavelength range are presented for the Na-like ions ArVIII, CrXIV,
MnXV, FeXVI, CoXVII, NiXVIII and ZnXX. A comparison of these with an
extensive data set of the solar active region, quiet-Sun, subflare and
off-limb observations, obtained during rocket flights by the Solar
EUV Research Telescope and Spectrograph (SERTS), reveals generally
very good agreement between theory and experiment. This indicates
that most of the Na-like ion lines are reliably detected in the
SERTS observations, and hence may be employed with confidence in
solar spectral analyses. However, the features in the SERTS spectra
at 236.34 and 300.25 Å, originally identified as the NiXVIII 3p
2P3/2-3d 2D3/2 and
CrXIV 3p 2P3/2-3d 2D5/2
transitions, respectively, are found to be due to emission lines of
ArXIII (236.34 Å) and possibly SV or NiVI (300.25 Å). The CoXVII
3s 2S-3p 2P3/2 line at 312.55 Å is
always badly blended with an FeXV feature at the same wavelength, but
MnXV 3s 2S-3p 2P1/2 at 384.75 Å may
not always be as affected by second-order emission from FeXII 192.37
Å as previously thought. On the other hand, we find that the ZnXX 3s
2S-3p 2P3/2 transition can sometimes
make a significant contribution to the ZnXX/FeXIII 256.43-Å blend, and
hence care must be taken when using this feature as an FeXIII electron
density diagnostic. A line in the SERTS-89 active region spectrum at
265.00 Å has been re-assessed, and we confirm its identification as
the FeXVI 3p 2P3/2-3d 2D3/2
transition.

---------------------------------------------------------
Title: Electron Temperature and Speed Measurements in the Lower
Solar Corona: Results from the June 2001 Eclipse
Authors: Reginald, N. L.; St. Cyr, O. C.; Davila, J. M.; Brosius, J. W.
2003SPD....34.0408R Altcode: 2003BAAS...35..811R
The determination of the radial and latitudinal temperature and solar
wind speed profiles of the solar corona is of immense importance
in understanding the coronal heating mechanism and the dynamics of
the coronal features. Cram (Sol. Phys, 48, 3, 1976) provided the
theory for the formation of the K-coronal spectrum and a method for
determining the radial profile of the coronal temperature. We
have modified Cram's theory to incorporate the role of the solar wind
in the formation of the K-corona and have identified both temperature
and speed sensitive intensity ratios. We built MACS (Multi Aperture
Coronal Spectrometer); a fiber optic based spectrograph to study
the total solar eclipse of June 2001 in Lusaka, Zambia. In this
instrument one end of the five fiber-optic tips at the focal plane of
the telescope were positioned to see different latitudes at the same
radii on the solar corona. The other ends of the fibers were vertically
aligned and placed at the primary focus of the collimating lens of
the spectrograph. We have succeeded in isolating the K-corona
from the spectral observations made through two different fibers
in MACS to match the theoretical K-coronal profiles for different
temperatures and wind speeds. Results were obtained at two locations
in the solar corona, one within a helmet streamer at the east limb
and the second in a streamer cluster in the southwest. Both points
were at an altitude of about 0.1-0.2 Rsun above the solar
limb. The east limb location at the edge of a helmet streamer and the
southwest location yielded electron temperatures of 0.94 +/- 0.01 MK
and 1.28 +/- 0.02 MK and bulk flow speeds of 124.0 +/- 48.0 km/sec
and 149.0 +/- 59.0 km/sec, respectively. This mechanism provides for
simultaneous measurement of both the temperature and wind speed in the
field of view of an exposed fiber to the corona. We will also present
the details of this experiment.

---------------------------------------------------------
Title: The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS)
Authors: Rabin, D.; Davila, J.; Thomas, R. J.; Engler, C.; Irish,
S.; Keski-Kuha, R.; Novello, J.; Nowak, M.; Payne, L.; Rodriguez, I.;
Saha, T.; Scott, R.; Swartz, M.; Trimble, M.; White, L.; Seshadri, S.
2003SPD....34.2007R Altcode: 2003BAAS...35..845R
EUNIS is a high-efficiency extreme ultraviolet spectrometer that
is expected to fly for the first time in 2004 as a sounding rocket
payload. Using two independent optical systems, EUNIS will probe
the structure and dynamics of the inner solar corona high spectral
resolution in two wavelength regions: 17-21 nm with 3.5 pm resolution
and 30-37 nm with 7 pm resolution. The long wavelength channel includes
He II 30.4 nm and strong lines from Fe XI-XVI; the short wavelength
channel includes strong lines of Fe IX-XIII. Angular resolution of
2 arcsec is maintained along a slit covering a full solar radius. EUNIS will have 100 times the throughput of the highly successful
SERTS payloads that have preceded it. There are only two reflections in
each optical channel, from the superpolished, off-axis paraboloidal
primary and the toroidal grating. Each optical element is coated
with a high-efficiency multilayer coating optimized for its spectral
bandpass. The detector in each channel is a microchannel plate image
intensifier fiber-coupled to three 1K x 1K active pixel sensors. EUNIS will obtain spectra with a cadence as short as 1 sec, allowing
unprecedented studies of the physical properties of evolving and
transient structures. Diagnostics of wave heating and reconnection wil
be studied at heights above 2 solar radii, in the wind acceleration
region. The broad spectral coverage and high spectral resolution will
provide superior temperature and density diagnostics and will enable
underflight calibration of several orbital instruments, including
SOHO/CDS and EIT, TRACE, Solar-B/EIS, and STEREO/EUVI. EUNIS
is supported by NASA through the Low Cost Access to Space Program in
Solar and Heliospheric Physics.

---------------------------------------------------------
Title: Nanoflare Frequency Distribution Scaling from Wave Heating:
Results of Nonlinear Loop Modeling
Authors: Davila, J. M.; Ofman, L.; Davila, J. M.; Ofman, L.
2003SPD....34.1601D Altcode: 2003BAAS...35..832D
The statistics of nanoflare events observed by TRACE in the EUV and
Yohkoh in soft X-rays exhibits a power law relation between the peak
thermal energy and the number of events per energy interval. Using
1D coronal loop model with nonlinear coupling to the chromosphere
(Ofman, Klimchuk, and Davila 1998) we calculate the distribution of
heating events due to the dissipation of waves driven by a random
Alfven wave source. Initial results show that the number of heating
events per energy bin scale with energy with the power of 2+/-
0.4. The scaling is consistent with the observed value of 1.86+/-0.07
at 171Å and 1.81+/-0.10 at 195Å found with TRACE (Aschwanden and
Parnell 2002). Thus, we conclude that in the nanonflare energy range
(E&lt;1028 erg) the observed frequency distribution of peak
energy is consistent with wave heating.

---------------------------------------------------------
Title: Electron Temperature and Speed Measurements In the Low Solar
Corona: Results from the June 2001 Eclipse
Authors: Reginald, N. L.; St. Cyr, O. C.; Davila, J. M.; Brosius, J. W.
2003EAEJA....11383R Altcode:
The determination of the radial and latitudinal temperature and solar
wind speed profiles of the solar corona is of immense importance in
understanding the coronal heating mechanism and the dynamics of the
coronal features. Cram (Sol. Phys, 48,3, 1976) provided the theory for
the formation of the K-coronal spectrum and a method for determining the
radial profile of the coronal temperature. A slit-based spectroscopic
study was performed by Ichimoto et.al (PASJ, 48, 545, 1996) on the solar
corona in conjunction with the total solar eclipse of 1994 to evaluate
the temperature profiles of the solar corona. We have modified Cram's
theory to incorporate the role of the solar wind in the formation of
the K-corona and have identified both temperature and speed sensitive
intensity ratios. We built MACS (Multi Aperture Coronal Spectrometer);
a fiber optic based spectrograph to study the total solar eclipse of
June 2001 in Lusaka, Zambia. In this instrument one end of the five
fiber-optic tips at the focal plane of the telescope were positioned to
see different latitudes at the same radii on the solar corona. The other
ends of the fibers were vertically aligned and placed at the primary
focus of the collimating lens of the spectrograph. We have succeeded in
isolating the K-corona from the spectral observations made through two
different fibers in MACS to match the theoretical K-coronal profiles
for different temperatures and wind speeds. Results were obtained at
two locations in the solar corona, one within a helmet streamer at the
east limb and the second in a streamer cluster in the southwest. Both
points were at an altitude of about 0.1-0.2 RSun above the
solar limb. The east limb location at the edge of a helmet streamer and
the southwest location yielded electron temperatures of 0.94 ± 0.01
MK and 1.28 ± 0.02 MK and bulk flow speeds of 124.0 ± 48.0 km/sec
and 149.0 ± 59.0 km/sec, respectively. This mechanism provides for
simultaneous measurement of both the temperature and wind speed in the
field of view of an exposed fiber to the corona. We will also present
the details of this experiment.

---------------------------------------------------------
Title: RHESSI and non-thermal solar physics in the IHY
Authors: Hudson, H.; Davila, J.; Dennis, B.; Emslie, G.; Lin, R.;
Ryan, J.; Share, G.
2003EAEJA.....7939H Altcode:
The signatures of non-thermal activity on the Sun - X-rays, gamma-rays,
and high-energy particles - present us with the closest possible view
of the essential physics underlying solar activity and its heliospheric
consequences. During the International Heliophysical Year (2007) we
will have a rich harvest of measurements from current sunspot maximum
from an unprecedented array of observations from space. This poster
will present the most recent observations from the newest spacecraft,
RHESSI (the Reuven Ramaty High-Energy Solar Spectroscopic Imager) in
the context of the IHY and possible future programs. The RHESSI data
discussed emphasize the gamma-ray line flare of July 23, 2002 as well
as discoveries made in the April 21, 2002 and other events.

---------------------------------------------------------
Title: COR1 inner coronagraph for STEREO-SECCHI
Authors: Thompson, William T.; Davila, Joseph M.; Fisher, Richard R.;
Orwig, Larry E.; Mentzell, John E.; Hetherington, Samuel E.; Derro,
Rebecca J.; Federline, Robert E.; Clark, David C.; Chen, Philip T. C.;
Tveekrem, June L.; Martino, Anthony J.; Novello, Joseph; Wesenberg,
Richard P.; StCyr, Orville C.; Reginald, Nelson L.; Howard, Russell A.;
Mehalick, Kimberly I.; Hersh, Michael J.; Newman, Miles D.; Thomas,
Debbie L.; Card, Gregory L.; Elmore, David F.
2003SPIE.4853....1T Altcode:
The Solar Terrestrial Relations Observatory (STEREO) is a pair of
identical satellites that will orbit the Sun so as to drift ahead of and
behind Earth respectively, to give a stereo view of the Sun. STEREO is
currently scheduled for launch in November 2005. One of the instrument
packages that will be flown on each of the STEREO spacecrafts is the
Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI),
which consists of an extreme ultraviolet imager, two coronagraphs,
and two side-viewing heliospheric imagers to observe solar coronal
mass ejections all the way from the Sun to Earth. We report here on
the inner coronagraph, labeled COR1. COR1 is a classic Lyot internally
occulting refractive coronagraph, adapted for the first time to be
used in space. The field of view is from 1.3 to 4 solar radii. A
linear polarizer is used to suppress scattered light, and to extract
the polarized brightness signal from the solar corona. The optical
scattering performance of the coronagraph was first modeled using both
the ASAP and APART numerical modeling codes, and then tested at the
Vacuum Tunnel Facility at the National Center for Atmospheric Research
in Boulder, Colorado. In this report, we will focus on the COR1 optical
design, the predicted optical performance, and the observed performance
in the lab. We will also discuss the mechanical and thermal design, and
the cleanliness requirements needed to achieve the optical performance.

---------------------------------------------------------
Title: Advanced spectroscopic and coronographic explorer: science
payload design concept
Authors: Gardner, Larry D.; Kohl, John L.; Daigneau, Peter S.; Smith,
Peter L.; Strachan, Leonard, Jr.; Howard, Russell A.; Socker, Dennis
G.; Davila, Joseph M.; Noci, Giancarlo C.; Romoli, Marco; Fineschi,
Silvano
2003SPIE.4843....1G Altcode:
The Advanced Spectroscopic and Coronagraphic Explorer (ASCE) was
proposed in 2001 to NASA's Medium-Class Explorer (MIDEX) program
by the Smithsonian Astrophysical Observatory in collaboration with
the Naval Research Laboratory, Goddard Space Flight Center and the
Italian Space Agency. It is one of four missions selected for Phase A
study in 2002. ASCE is composed of three instrument units: an Advanced
Ultraviolet Coronagraph Spectrometer (AUVCS), an Advanced Large Aperture
visible light Spectroscopic Coronagraph (ALASCO), and an Advanced Solar
Disk Spectrometer (ASDS). ASCE makes use of a 13 m long boom that is
extended on orbit and positions the external occulters of AUVCS and
ALASCO nearly 15 m in front of their respective telescope mirrors. The
optical design concepts for the instruments will be discussed.

---------------------------------------------------------
Title: Si IX Emission Lines in Spectra Obtained with the Solar euv
Research Telescope and Spectrograph (Serts)
Authors: Keenan, F. P.; Katsiyannis, A. C.; Aggarwal, K. M.;
Mathioudakis, M.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.
2003SoPh..212...65K Altcode:
Theoretical electron-density-sensitive emission line ratios involving
2s22p2-2s2p3 transitions in Si ix
between 223 and 350 Å are presented. A comparison of these with
an extensive dataset of solar-active-region, quiet-Sun, subflare
and off-limb observations, obtained during rocket flights by the
Solar EUV Research Telescope and Spectrograph (SERTS), reveals
generally very good agreement between theory and experiment. This
provides support for the accuracy of the line-ratio diagnostics,
and hence the atomic data on which they are based. In particular,
the density-sensitive intensity ratio I(258.10 Å)/I(349.87 Å)
offers an especially promising diagnostic for studies of coronal
plasmas, as it involves two reasonably strong emission lines and
varies by more than an order of magnitude over the useful density
range of 109-1011 cm−3. The
2s22p2 1S0-2s2p3
1P1 transition at 259.77 Å is very marginally
identified for the first time in the SERTS database, although it has
previously been detected in solar flare observations.

---------------------------------------------------------
Title: Empirically Constrained Multidimensional MHD Model for the
Solar Corona and Solar Wind
Authors: Sittler, E. C.; Ofman, L.; Gibson, S.; Guthathakurta, M.;
Skoug, R.; Fludra, A.; Davila, J.; Holzer, T.
2002AGUFMSH21A0502S Altcode:
We are developing a time stationary self-consistent 2D MHD model of
the solar corona and solar wind that explicitly solves the energy
equation, using a semi-empirical 2D MHD model of the corona to provide
an empirically determined effective heat flux qeff (i.e.,
the term effective means the possible presence of wave contributions)
for the energy equation and effective pressure Peff
for the momentum equation. Preliminary results indicated that in
order to achieve high speed winds over the poles we not only needed
to use qeff in the energy equation, but also needed to
include the empirically determined effective pressure Peff
as a constraint in the momentum equation, which means that momentum
addition by waves above 2 RS are required to produce high
speed winds. A solution which only included qeff showed high
acceleration over the poles below 2 RS, but then drooped
above that radial distance indicating we needed momentum addition above
that height to get high speed flows over the poles. We will show new
results which include the added constraint of Peff in the
momentum equation. This method will allows us to estimate the momentum
addition term due to waves as a function of height and latitude within
the corona. The estimates of Peff and qeff come
from the semi-empirical 2D MHD model of the solar corona by Sittler and
Guhathakurta (1999, 2002) which is based on Mk-III, Skylab and Ulysses
observations. For future model development we plan to use SOHO LASCO,
CDS, EIT, UVCS, Spartan 201-05 and Ulysses data as constraints for
our model calculations. The model by Sittler and Guhathakurta (1999,
2002) is not a self-consistent calculation. The calculations presented
here are a continuing effort to provide a self-consistent calculation
based on empirical constraints.

---------------------------------------------------------
Title: The Advanced Spectroscopic and Coronagraphic Explorer (ASCE)
Mission Concept Study
Authors: Kohl, J.; Howard, R.; Davila, J.; Noci, G.; Gardner, L.;
Socker, D.; Romoli, M.; Strachan, L.; Floyd, L.; Cranmer, S.; Raymond,
J.; van Ballegooijen, A.
2002AGUFMSH52A0463K Altcode:
The ASCE Mission is currently in a Phase A feasibility study as a
candidate for the upcoming MIDEX selection. The ASCE science payload
provides next generation spectroscopic and polarimetric instrumentation
aimed at identifying the physical processes governing solar wind
generation and coronal mass ejections (CMEs). During the current phase,
engineering design and analyses have demonstrated the feasibility of
accomplishing the original mission objectives within the MIDEX mission
constraints. The launch is planned for early 2007 and the operations
and analyses are expected to continue for 5 years. ASCE data along with
data analysis software and calibration data will be unrestricted and
available to the scientific community via an automated web site. A
Guest Investigator program is planned with an average of 15 grants
running concurrently during 2008 to 2012. Grants would be awarded in
response to proposals submitted during the first and subsequent years
of the mission.

---------------------------------------------------------
Title: The International Heliophysical Year (IHY)
Authors: Davila, J. M.; Harrison, R.; Poland, A.; Thompson, B.;
Gopalswamy, N.
2002AGUFMSH21A0518D Altcode:
In 1957 a program of international research, inspired by the
International Polar Years of 1882-83 and 1932-33, was organized as
the International Geophysical Year (IGY) to study global phenomena of
the Earth and geospace. The IGY involved about 60,000 scientists from
66 nations, working at thousands of stations, from pole to pole to
obtain simultaneous, global observations on Earth and in space. There
had never been anything like it before. The fiftieth anniversary of
the International Geophysical Year will occur in 2007. We propose to
organize an international program of scientific collaboration for this
time period called the International Heliophysical Year (IHY). Like
it predecessors, the IHY will focus on fundamental global questions
of Earth science.

---------------------------------------------------------
Title: SHARPI: Solar High Angular Resolution Photometric Imager
Authors: Rabin, D.; Davila, J.; Content, D.; Keski-Kuha, R.;
Michael, S.
2002AAS...200.5606R Altcode: 2002BAAS...34..735R
Observing the lower solar atmosphere with enough linear resolution (&lt;
100 km) to study individual magnetic flux tubes and other features on
scales comparable to the photon mean free path remains a challenging and
elusive goal. Space-borne instruments based on conventional heavy optics
proved to be too expensive, and adaptive optics on the ground made slow
progress for many years. Yet, the scientific case for high-resolution
imaging and magnetography has only become more compelling over the last
ten years. Today, ground-based adaptive optics is a promising approach
for small fields of view at visible wavelengths. Space experiments
will need to employ lightweight optics and low-cost platforms. The
Sunrise balloon experiment is one example. We describe a concept for
a sounding rocket experiment that will achieve 0.1-arcsecond imaging
using a lightweight, ultraprecise 55-cm mirror in the far ultraviolet
(160 nm continuum, Lyman alpha, and possibly C IV 155 nm). The f/1.2
parabolic primary mirror is entering the final stages of production. The
mirror is a ULE honeycomb design with front and back face sheets. The
front sheet will be figured to 6.3 nm rms with microroughness 1 nm
or better. For the initial proof of concept, we describe a no-frills,
high-cadence imager aboard a Black Brant sounding rocket. Development
of lightweight UV/EUV optics at Goddard Space Flight Center has been
supported by the GSFC Internal Research and Development program.

---------------------------------------------------------
Title: A New Diagnostic Technique for the Solar Corona
Authors: Davila, J. M.; Nelson, R.; St. Cyr, O. C.
2002AAS...200.5607D Altcode: 2002BAAS...34..735D
Over the last 30-40 years spectroscopic observation of the EUV line
emission has proved invaluable as a diagnostic of the solar coronal
plasma state. Line ratios have been used to determine electron
density, electron temperature and ion flow velocity. In this paper,
we present results obtained with a new measurement technique that
uses spectroscopic observations of the white light corona to obtain
the electron density, temperature, and flow velocity. A prototype
instrument has been designed and built to obtain visible light spectra
(3800-4300 A) with modest resolution. This instrument was used to
obtain coronal observations during the June 2001 eclipse in Zambia. The
data were corrected for sky and instrument transmission to derive the
electron temperature and flow speed. Results from these measurements
will be discussed.

---------------------------------------------------------
Title: Science Prospects for the STEREO Mission
Authors: Davila, J.; St-Cyr, O.
2002cosp...34E.478D Altcode: 2002cosp.meetE.478D
The solar magnetic field is constantly generated beneath the surface
of the Sun by the solar dynamo. To balance this flux generation,
there is constant dissipation of magnetic flux at and above the solar
surface. The largest phenomenon associated with this dissipation is
the Coronal Mass Ejection (CME). The Solar and Heliospheric Observatory
(SOHO) has provided remarkable views of the corona and CMEs, and served
to highlight how these large interplanetary disturbances can have
terrestrial consequences. STEREO is the next logical step to study
the physics of CME origin, propagation, and terrestrial effects. Two
spacecraft with identical instrument complements will be launched on a
single launch vehicle in November 2007. One spacecraft will drift ahead
and the second behind the Earth at a separation rate of 22 degrees per
year. Observation from these two vantage points will for the first time
allow the observation of the threedimensional structure of CMEs and the
coronal structures where they originate Each STEREO spacecraft carries
a complement of 10 instruments, which include (for the first time)
an extensive set of BOTH remote sensing and in-situ instruments. The
remote sensing suite is capable of imaging CMEs from the solar surface
out to beyond EarthSs orbit (1 AU), and in-situ instruments are able to
measure distribution functions for electrons, protons, and ions over a
broad energy range, from the normal thermal solar wind plasma to the
most energetic solar particles. It is anticipated that these studies
will ultimately lead to an increased understanding of the CME process
and eventually to the ability to predict CME occurrence and thereby -
SforecastS the condition of the near-Earth environment.

---------------------------------------------------------
Title: The International Heliophysical Year Concept
Authors: Davila, J.; Harrison, R.; Poland, A.; St-Cyr, O.; Thompson, B.
2002cosp...34E.529D Altcode: 2002cosp.meetE.529D
In 1957 a program of international research, inspired by the
International Polar Years of 1882-83 and 1932-33, was organized as
the International Geophysical Year (IGY) to study global phenomena of
the Earth and geospace. The IGY involved about 60,000 scientists from
66 nations, working at thousands of stations, from pole to pole to
obtain simultaneous, global observations on Earth and in space. There
had never been anything like it before. The fiftieth anniversary of
the International Geophysical Year will occur in 2007. We propose to
organize an international program of scientific collaboration for this
time period called the International Heliophysical Year (IHY). Like
its predecessors, the IHY will focus on fundamental global questions
of Earth science.

---------------------------------------------------------
Title: International Polar Year 2007: An Integrated Heliospheric
and Oceanographic Program?
Authors: Johnson, G.; Davila, J.
2002cosp...34E1194J Altcode: 2002cosp.meetE1194J
An international symposium SPerspectives of Modern Polar ResearchT
was convened - in Bad Durkeim, Germany 2001 to celebrated the 175the
anniversary of the birth of Georg von Neumayer. At that symposium the
Nermayer Declaration was adopted to commemorate the 125th anniversary
of the IPY in 2007. SA 125th year IPY program be initiated using
new and present technologies to determine: 1 . Causes and effects
of climatic variability-air/sea/ice interactins, and 2. Lithosphere
dynamicsUevolution and history of crust and sedimentary cover. The po
lar regions would be the focus.T Polar oceanographic contributions
to global climate change are still a matter of conjecture, and to a
large extent so are the extraterrestrial contributions. The proposed
IPY would focus on these issues. As part of the global heat engine,
the polar regions hav a major role in the worldSs transfer of energy,
and the ocean/stmosphere system is known to be both an indicator
and a componenet of climate change. It is clear that acomplex suite
of significant, interrelated, atmospheric, oceanic and terrestrial
changes has occurred in the the polsar regions in recent decades. These
events are affecting every part of the polar environment and are
having repercussions on society. In a similar vein an International
Heliophysical Year (IHY) has been proposed to obtain a coordinated
set of observations to study at the largest scale the solar genergated
events that affect life and climate on Earth as has been documented in
the Holocene sedimentary recofd. A modeling capability is the ultimate
goal so the physical process can be tracked throughout the entire
Sun-Earth system. This program will require an integrated, holistic
system approach encompassing a side range of disciplines with new
and improved technologies for long term measurements on the seabed,
in the water column and in space over all seasons. Coordination,
collaboration and documentation of an interated science plan with
international scientific organizations/scientists via joint workshops
are the next steps.

---------------------------------------------------------
Title: New Observations of Oscillating Coronal Loops
Authors: Reeves, K. K.; Shoer, J.; Deluca, E. E.; Winebarger, A. R.;
Ofman, L.; Davila, J. M.
2001AGUFMSH11A0704R Altcode:
One of the most promising discoveries of the TRACE mission is the first
observations of transverse oscillations in coronal loops (Aschwanden
et al 1999, Nakariakov et al 1999). Loops are set into motion from
nearby flares, oscillate with a well defined frequency and decay
on a time scale of 10 minutes. While the theoretical study of MHD
waves in the corona has a long history, observational support has
dramatically increased over the past 10 years as coronal instruments
have improved. The transverse oscillations have been identified as
standing kink modes for the 14-July-1998 observations cited above. In
this paper we present clear evidence for a decaying global kink modes
observed by TRACE on 15-Apr-2001. Six different loops have been observed
to oscillate with a frequency in the range: 15-20 mHz (compared with
4 mHz for 14-July-1998) and a decay time in the range: 8-23 minutes
(compared with 11 minutes for the earlier event). The implications
for these results for coronal diagnostics and solar coronal seismology
will be discussed.

---------------------------------------------------------
Title: EUNIS: a solar EUV normal-incidence spectrometer
Authors: Thomas, Roger J.; Davila, Joseph M.
2001SPIE.4498..161T Altcode:
GSFC is in the process of assembling a solar EUV Normal-Incidence
Spectrometer called EUNIS, to be flown as a sounding rocket
payload. This instrument builds on the many technical innovations
pioneered by our highly successful SERTS experiment over its past ten
flights. The new design has improved spatial and spectral resolutions,
as well as 100 times greater sensitivity, permitting EUV spectroscopy
with a temporal resolution near 1 second for the first time ever. To
achieve such high time cadence, a novel Active-Pixel-Sensor detector is
being developed as a key component of our design. The high sensitivity
of EUNIS allows entirely new studies of transient coronal phenomena,
such as the rapid loop dynamics seen by TRACE, and searches for
non-thermal motions indicative of magnetic reconnection or wave
heating. The increased sensitivity also permits useful EUV spectra
at heights of 2-3 solar radii above the limb, where the transition
between the static corona and the solar wind might occur. In addition,
the new design features two independent optical systems, more than
doubling the spectral bandwidth covered on each flight. Its 300-370A
bandpass includes He II 304A and strong lines from Fe XI-XVI, extending
the current SERTS range of 300-355A to further improve our ongoing
series of calibration under-flights for SOHO/CDS and EIT. The second
bandpass of 170-205A has a sequence of very strong Fe IX-XIII lines,
and allows under-flight support for two more channels on SOHO/EIT,
two channels on TRACE, one on Solar-B/EIS, and all four channels on
the STEREO/EUVI instrument. First flight of the new EUNIS payload is
presently scheduled for 2002 October.

---------------------------------------------------------
Title: The Advanced Spectroscopic and Coronagraphic Explorer Mission
Authors: Kohl, J. L.; Howard, R.; Davila, J.; Noci, G.; Esser, R.;
Ciaravella, A.; Cranmer, S.; Fineschi, S.; Gardner, L.; Raymond, J.;
Romoli, M.; Smith, P.; Socker, D.; Strachan, L.; Van Ballegooijen, A.
2001AGUFMSH31B0711K Altcode:
SOHO has provided profound insights into the physics of solar wind
acceleration and coronal mass ejections. Although significant
progress has been made, most of the dominant physical processes
controlling these phenomena are still not identified. The Advanced
Spectroscopic and Coronagraphic Explorer Mission provides next
generation spectroscopic and polarimetric instrumentation aimed at
identifying these processes. The launch is planned for March 2007 with
mission operations and data analysis continuing for 5 years. The data
will be unrestricted and available to the community. The envisioned
program includes a Guest Investigator Program with an average of 15
grants to be awarded in response to proposals submitted during the
first year of the mission. Information about the proposed scientific
goals and instrumentation will be presented.

---------------------------------------------------------
Title: Three-Fluid 2.5-dimensional Magnetohydrodynamic Model of the
Effective Temperature in Coronal Holes
Authors: Ofman, L.; Davila, J. M.
2001ApJ...553..935O Altcode:
Recent SOHO Ultraviolet Coronagraph Spectrometer (UVCS)
observations show that protons and minor ions are hot
(Tp&gt;106 K, Ti&gt;107
K) and anisotropic in coronal holes. A possible cause of the large
perpendicular motions is unresolved Alfvénic fluctuations in
the solar wind. Using the three-fluid 2.5-dimensional MHD model,
we have shown that the unresolved Alfvénic fluctuations lead to
apparent proton temperature and anisotropy consistent with UVCS
observations. However, Alfvén waves with realistic amplitudes cannot
reproduce the O5+ perpendicular temperature and anisotropy
deduced from UVCS observations. This suggests that the minor ions are
heated by a different mechanism than protons.

---------------------------------------------------------
Title: Spectroscopy of Coronal Electrons -- White-light Measurements
Authors: Reginald, N.; Davila, J. M.; St. Cyr, O. C.
2001AGUSM..SH32B03R Altcode:
We report on our continuing efforts to refine the technique described
by Reginald and Davila (2000) where white-light spectroscopy is used to
measure the solar wind velocity and electron temperature globally. This
method is complementary to those that have been used to date (e.g.,
UV and EUV spectral measurements; visible line ratios; interplanetary
radio scintillation, and semi-empirical modeling). This paper will
concentrate on instrumentation issues, and modeling efforts relevant
to the technique are reported elsewhere in this volume. Results from
the 1999 total eclipse in Turkey will be shown, and preparations
for the 2001 eclipse in Africa will be discussed. A second related
technique using passband filters will also be deployed in 2001
for direct comparison to the spectroscopic method. A groundbased
coronagraph is under development to extend this technique beyond
eclipse opportunities. But the low stray light levels available
on a spacebased platform, along with the heritage of coronagraphic
techniques, should make this technique a strong candidate for future
spaceflight opportunities.

---------------------------------------------------------
Title: Modeling the Spectrum of the K-corona with Embedded Streamers
Authors: Reginald, N.; Davila, J. M.
2001AGUSM..SH41B23R Altcode:
The white light emission from the corona is generated by the Thomson
scattering of photospheric emission by electrons. Recently Reginald
and Davila (Solar Phys, 2000) have developed models, assuming a
radially symmetric coronal electron density, that suggest that
spectral measurements of the K-coronal emission can be used to
determine the electron temperature, and the radial outflow velocity
of electrons in the low corona. These measurements could provide for
continuous remote-sensing observation of the solar wind speed from a
spacecraft located at say L1. Recently these models have been extended
to include the effect of streamers. Streamers are modeled simply
as localized density enhancements along the line of sight. During
this paper, the results of these models will be discussed, and the
effect on the measurement of electron temperature and velocity will
be assesed. Experimental efforts to verify these model predictions
will be discussed in a separate paper also presented at this meeting.

---------------------------------------------------------
Title: Multifluid and Hybrid Modeling of Waves in Coronal Holes:
Implications for Heating Theories
Authors: Ofman, L.; Davila, J. M.
2001AGUSM..SH22E01O Altcode:
Recent SOHO Ultraviolet Coronagraph Spectrometer (UVCS)
observations show that protons and minor ions are hot
(Tp&gt;106 K, Ti&gt;107
K) and anisotropic in coronal holes. A possible cause of the large
perpendicular motions is unresolved Alfvénic fluctuations in the
solar wind. Using the three-fluid 2.5D MHD model we have shown
that the unresolved Alfvénic fluctuations lead to apparent proton
temperature and anisotropy consistent with UVCS observations. However,
\Alfven waves with realistic amplitudes can not reproduce the
O5+ perpendicular temperature and anisotropy deduced from
UVCS observations. We use the hybrid model to investigate constrains
on the anisotropy of the minor ions. Our results suggests that
the minor ions are heated and accelerated by high-frequency waves (
~103 Hz), while proton heating occurs by low frequency waves
( ~10-3 Hz).

---------------------------------------------------------
Title: EUNIS: Extreme-Ultraviolet Normal-Incidence Spectrometer
Authors: Thomas, R. J.; Davila, J. M.
2001AGUSM..SP21B05T Altcode:
GSFC is in the process of assembling an Extreme-Ultraviolet
Normal-Incidence Spectrometer called EUNIS, to be flown as a sounding
rocket payload. This instrument builds on the many technical innovations
pioneered by our highly successful SERTS experiment, which has now flown
a total of ten times, most recently last summer. The new design will
have somewhat improved spatial and spectral resolutions, as well as two
orders of magnitude greater sensitivity, permitting high signal/noise
EUV spectroscopy with a temporal resolution near 1~second for the first
time ever. In order to achieve such high time cadence, a novel detector
system is being developed, based on Active-Pixel-Sensor electronics,
a key component of our design. The high sensitivity of EUNIS will
allow entirely new studies of transient coronal phenomena, such as the
rapid loop dynamics seen by TRACE, and searches for non-thermal motions
indicative of magnetic reconnection or wave heating. Another observing
mode will be to raster a two dimensional region on the disk, giving
data on much larger solar areas than could be covered with SERTS. The
increased sensitivity will also permit useful EUV spectra at heights
of 2--3~Rsun above the limb, where the transition between
the static corona and the solar wind might occur. In addition, the new
design features two independent optical systems, which more than double
the spectral bandwidth covered on each flight. Its 300--370Å bandpass
includes He~II 304Å and strong lines from Fe~XI--XVI, extending
the current SERTS range of 300--355Å to further improve our ongoing
series of calibration under-flights for SOHO/CDS and EIT. The second
bandpass of 170--230Å has a sequence of very strong Fe~IX--XIV lines,
and will allow under-flight support for two more channels on SOHO/EIT,
two channels on TRACE, one on Solar-B/EIS, and all four channels on
the STEREO/EUVI instrument. First flight of the new EUNIS payload
is scheduled for 2002 October from White Sands Missile Range, New
Mexico. This work is supported under NASA RTOP 344-17-38.

---------------------------------------------------------
Title: Huge Coronal Structure and Heating Constraints Determined
from SERTS Observations
Authors: Falconer, D. A.; Davila, J. M.
2001ApJ...547.1109F Altcode:
Intensities of the extreme-ultraviolet (EUV) spectral lines were
measured as a function of radius off the solar limb by two flights
of the Goddard's Solar Extreme-Ultraviolet Rocket Telescope and
Spectrograph (SERTS) for three quiet-Sun regions. Density scale
heights were determined for the different spectral lines. Limits on the
filling factor were determined. In the one case where an upper limit
was determined it was much less than unity. Coronal heating above 1.15
solar radii is required for all three regions studied. For reasonable
filling factors, local heating is needed.

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Title: Overview of the Solar Ultraviolet Magnetograph Investigation
Authors: West, Edward A.; Porter, Jason G.; Davis, John M.; Gary,
G. Allen; Rabin, Douglas M.; Thomas, Roger J.; Davila, Joseph M.
2000SPIE.4139..350W Altcode:
Traditional magnetographs measure the solar magnetic field at the
visible 'surface' of the Sun, the photosphere. The Solar Ultraviolet
Magnetograph Investigation (SUMI) is a hardware development study
for an instrument to measure the solar magnetic field higher in the
atmosphere, in the upper chromosphere and in the transition region at
the base of the corona. The magnetic pressure at these levels is much
stronger than the gas pressure (in contrast to the situation at the
photosphere), so the field controls the structure and dynamics of the
atmosphere. Rapid changes in the magnetic structure of the atmosphere
become possible at this height, with the release of energy. Measurements
of the vector magnetic field in this region will significantly improve
our understanding of the physical processes heating the Sun's upper
atmosphere and driving transient phenomena such as flares and coronal
mass ejections. The instrument will incorporate new technologies to
achieve the polarization efficiencies required to measure the magnetic
splitting of lines in the VUV an UV (CIV at 1550 angstrom and
MgII at 2800 angstrom). We describe the scientific goals,
the optical components that are being developed for a sounding rocket
program, and the SUMI baseline design.

---------------------------------------------------------
Title: Analysis of a Solar Active Region Extreme-Ultraviolet Spectrum
from SERTS-97
Authors: Brosius, Jeffrey W.; Thomas, Roger J.; Davila, Joseph M.;
Landi, Enrico
2000ApJ...543.1016B Altcode:
Goddard Space Flight Center's Solar EUV Research Telescope and
Spectrograph was flown on 1997 November 18, carrying an intensified
CCD detector and a multilayer-coated toroidal diffraction grating
with enhanced sensitivity over that of a standard gold-coated grating
throughout the instrument's 299-353 Å spectral bandpass. Spectra
and spectroheliograms of NOAA Active Region 8108 (N21°, E18°)
were obtained with a spectral resolution (instrumental FWHM) of
115 mÅ. Nearly 100 emission lines were observed in the spatially
averaged active region spectrum. Spectra and spectroheliograms of
quiet areas south of the region were also obtained. An end-to-end
radiometric calibration of the rocket instrument was carried out at
the Rutherford-Appleton Laboratory in the same facility that was used
to calibrate the Coronal Diagnostic Spectrometer experiment on SOHO
and using the same EUV light source. The accuracy of this calibration
is confirmed by the excellent agreement between the measured and
theoretical values of density- and temperature-insensitive line
intensity ratios. Nine emission lines of Fe XV are identified in
our spectrum; however, large differences between wavelengths in the
CHIANTI database and some of the measured solar wavelengths, as well
as inconsistencies of various theoretical intensity ratios, suggest
a need for improvement in the Fe XV atomic physics parameters and/or
the presence of unidentified blending lines. Density-sensitive line
intensity ratios of Fe XI λλ308.55/352.67, Fe XII λλ338.27/352.11,
Fe XIII λλ320.80/312.17, and Fe XV λλ321.78/327.03 yield logarithmic
electron densities (in cm-3) of 9.92+/-0.28, 9.74+/-0.28,
9.52+/-0.30, and 9.62+/-0.26, respectively. Using the strongest emission
line observed for each ionization stage of Fe from X through XVI and Ni
XVIII, we find that all of the measured nonthermal line widths yield
velocities consistent with 35 km s-1. The differential
emission measure curve derived from the observed line intensities
exhibits a relative minimum at logT~5.7, a broad maximum centered
around logT~6.3, and a rapid decline for temperatures above logT~6.6.

---------------------------------------------------------
Title: The Solar Terrestrial Relations Observatory - Mission Overview
Authors: Davila, J. M.; Rust, D. M.; Sharer, P. J.
2000SPD....31R0293D Altcode: 2000BAAS...32.1291D
Starting in 2004, the two identical STEREO spacecraft will drift slowly
off the Sun-Earth line, providing a series of differing perspectives
on CMEs and other solar and heliospheric structures. At the end
of the prime science (2-year) mission, the spacecraft will each be
about 45 degrees from Earth, one leading Earth and one trailing. Each
spacecraft will carry a cluster of telescopes, including coronagraphs,
EUV imagers, and particle detectors. When the images are combined with
solar magnetograms and other data from observatories on the ground or
in low Earth orbit, both the buildup of magnetic energy and the lift
off and trajectory of CMEs can be studied. Interpreting the STEREO
data will pose a new challenge to the solar community. We discuss
the STEREO mission design, instrument complement and the development
of the trajectory design that, we believe, maximizes the scientific
potential of the mission.

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Title: Space Weather Diamond: a four spacecraft monitoring system
Authors: Cyr, O. C. S.; Mesarch, M. A.; Maldonado, H. M.; Folta,
D. C.; Harper, A. D.; Davila, J. M.; Fisher, R. R.
2000JASTP..62.1251C Altcode: 2000JATP...62.1251C
We report here preliminary results of a mission analysis for a space
weather monitoring system that provides continuous transmission of solar
wind conditions 0.10 A.U. upstream from Earth. The system is based on
four platforms that are phased into eccentric heliocentric orbits but,
from the perspective of a fixed Sun-Earth line, the spacecraft appear to
orbit Earth. This system offers a /10× improvement in reporting solar
wind plasma and magnetic field characteristics beyond similar platforms
located at the Lagrangian /L-1 point. We describe launch and energy
considerations, along with a preliminary analysis of communication
requirements. The Space Weather Diamond offers significant potential
for scientific insight into problems requiring coordinated observations
from multiple vantage points by providing the ability to separate
spatial from temporal variations. We discuss examples for payloads
including both in situ and remote sensing instrumentation.

---------------------------------------------------------
Title: MACS for Global measurement of the Solar wind velocity and
the Thermal electron temperature during the Total solar eclipse on
11 August 1999
Authors: Reginald, Nelson L.; Davila, Joseph M.
2000SoPh..195..111R Altcode:
MACS for Multi-Aperture Coronal Spectrometer is a fiber-optic-based
spectrograph designed and used to perform global measurement of the
solar wind velocity and the thermal electron temperature of the solar
corona during the total solar eclipse on 11 August 1999. The motivation
for the construction of MACS was provided by the theory formulated by
Cram (1976) for the formation of the K-coronal spectrum and a method
for determining the radial profile of the thermal electron temperature
of the solar corona. Based on this theory a subsequent application was
carried out by Ichimoto et al. (1996) using a slit-based spectroscopic
study during the total solar eclipse on 3 November 1994. We have
modified Cram's theory to incorporate the role of the solar wind
velocity in the formation of the K-corona and have identified wind
and temperature sensitive intensity ratios. Instead of a slit-based
spectrograph MACS consists of twenty fiber optic tips placed at the
focal plane of the telescope and positioned to see different radii and
latitudes of the solar corona. Another fiber is placed at the center
of the frame and uses the lunar shadow for a measure of the background
signal. The other ends of the fibers are vertically aligned and placed
at the primary focus of the collimating lens of the spectrograph thus
providing simultaneous spectra from all of the fibers. In this first
paper (Paper I) we describe our instrument and the obtained coronal
spectra. The final and complete results will be presented in Paper II
(Reginald and Davila, 2000).

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Title: Three-dimensional MHD modeling of an impulsive excitation of
a coronal loop motivated by TRACE observations
Authors: Ofman, L.; Davila, J. M.
2000SPD....31.0604O Altcode: 2000BAAS...32..838O
Recently, decaying transversal oscillations of bright coronal loops
in the 171 Angstroms and 195 Angstroms emission lines were observed
with the imaging telescope on-board the TRACE satellite. The loop
oscillations were excited impulsively by a solar flare in the adjacent
active region. Using 3D MHD model of the loop the period and the decay
rate of the oscillations, together with the loop geometry, density,
and temperature can be used to determine the average magnetic field of
the loop, and the magnetic or viscous Reynolds number (R). Recently,
Nakariakov et al. (1999) used the R1/5 heating time scaling
to determine the range of the dissipation coefficients in the loop
observed with TRACE. Using the linearized 3D MHD model we investigate
the coupling of the decaying transverse mode and the internal Alfvén
mode, and examine the relation between the decay time of the transverse
oscillations and the heating time of the loop for a range of Reynolds
numbers, and wavenumbers. We use the nonlinear 3D MHD model with more
realistic loop geometry, boundary conditions, and mode coupling to study
the relaxation of the impulsively excited coronal loop oscillation. We
find that when the Reynolds number is large (R=104) the
nonlinear effects become important at the resonant dissipation layer,
and the heating time decreases compared to the linear case. We plan
to expand the nonlinear 3D model to include the effects of gravity,
and loop curvature to better model the loop oscillations observed
by TRACE. LO would like to acknowledge support by the NASA SR&amp;T,
and the HPCC programs.

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Title: Re-Calibration of SOHO by SERTS-99
Authors: Thomas, R. J.; Davila, J. M.; Thompson, W. T.; Kent, B. J.;
Hollandt, J.
2000SPD....31.0215T Altcode: 2000BAAS...32..813T
GSFC's Solar EUV Research Telescope and Spectrograph (SERTS) is
a rocket instrument that obtains imaged high-resolution spectra of
individual solar features to study the Sun's corona and upper transition
region. As with SERTS-97, an additional goal of the SERTS-99 flight on
1999 June 24 was to provide radiometric and wavelength calibrations for
several experiments on the SOHO satellite mission. For that purpose,
a second end-to-end radiometric calibration of SERTS was carried out
last fall at RAL in the same facility used to characterize the SOHO/CDS
experiment, using the same EUV light source specially re-calibrated by
PTB against the synchrotron radiation standard of the BESSY-I electron
storage ring. Measurements at a single SERTS aperture position were
made to determine the instrument's absolute response within 25% at
12 wavelengths covering its bandpass of 300 -- 365 Angstroms. These
were converted into full-aperture values through relative response
measurements over a complete range of radial aperture positions. Also,
post-flight wavelength calibrations were done at GSFC using well
known laboratory lines of He II and Ne II. SERTS-99 again carried
an EUV solar flux monitor kindly provided by USC; its readings were
used to validate our calculations of atmospheric EUV transmission
over the rocket's trajectory, and to provide an updated calibration
for one of the SOHO/CELIAS channels. During the flight, SERTS-99 and
CDS observed the same solar locations, as demonstrated by subsequent
data co-registration with simultaneous SOHO/EIT images, allowing the
SERTS calibrations to be directly applied to both CDS and EIT. Since it
clearly resolves the strong Si XI and He II lines blended in EIT's 304
Angstroms channel, SERTS gives information on the spectral composition
of those images as well. Examples of various cross-calibrations will be
compared with results from November 1997, prior to SOHO's temporary loss
of pointing control. This work is supported under NASA RTOP 344-17-38.

---------------------------------------------------------
Title: The Role of Velocity Redistribution in Enhancing the Intensity
of the HE II 304 Å Line in the Quiet-Sun Spectrum
Authors: Andretta, Vincenzo; Jordan, Stuart D.; Brosius, Jeffrey W.;
Davila, Joseph M.; Thomas, Roger J.; Behring, William E.; Thompson,
William T.; Garcia, Adriana
2000ApJ...535..438A Altcode:
We present observational evidence of the effect of small-scale
(“microturbulent”) velocities in enhancing the intensity of the
He II λ304 line with respect to other transition region emission
lines, a process we call “velocity redistribution,”. We first show
results from the 1991 and 1993 flights of SERTS (Solar EUV Rocket
Telescope and Spectrograph). The spectral resolution of the SERTS
instrument was sufficient to infer that, at the spatial resolution
of 5", the line profile is nearly Gaussian both in the quiet Sun and
in active regions. We were then able to determine, for the quiet Sun,
a lower limit for the amplitude of nonthermal motions in the region of
formation of the 304 Å line of the order of 10 km s-1. We
estimated that, in the presence of the steep temperature gradients
of the solar transition region (TR), velocities of this magnitude
can significantly enhance the intensity of that line, thus at least
helping to bridge the gap between calculated and observed values. We
also estimated the functional dependence of such an enhancement on
the relevant parameters (nonthermal velocities, temperature gradient,
and pressure). We then present results from a coordinated campaign,
using SOHO/CDS and Hα spectroheliograms from Coimbra Observatory,
aimed at determining the relationship between regions of enhanced
helium emission and chromospheric velocity fields and transition region
emission in the quiescent atmosphere. Using these data, we examined
the behavior of the He II λ304 line in the quiet-Sun supergranular
network and compared it with other TR lines, in particular with O III
λ600. We also examined the association of 304 Å emission with the
so-called coarse dark mottle, chromospheric structures seen in Hα
red-wing images and associated with spicules. We found that all these
observations are consistent with the velocity redistribution picture.

---------------------------------------------------------
Title: Coronal seismology: using oscillations to understand coronal
structure.
Authors: Davila, J. M.
2000BAAS...32R.837D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: MACS for global measurements of the thermal electron
temperature and the solar wind velocity in the solar corona during
the total solar eclipse of 11 August 1999
Authors: Reginald, N. L.; Davila, J. M.
2000SPD....31.1605R Altcode: 2000BAAS...32..849R
The determination of the radial and latitudinal temperature and wind
profiles of the solar corona is of immense importance in understanding
the coronal heating mechanism and the dynamics of the coronal
features. Cram (1976) provides the theory for the formation of the
K-coronal spectrum and a method for determining the radial profile of
the coronal temperature. A slit-based spectroscopic study was performed
by Ichimoto et.al (1996) on the solar corona in conjunction with the
total solar eclipse of 1994 to evaluate the temperature profiles of the
solar corona. We have modified Cram's theory to incorporate the role of
the solar wind in the formation of the K-corona and have identified both
temperature and wind sensitive intensity ratios. We built MACS (Multi
Aperture Coronal Spectrometer); a fiber optic based spectrograph to
study the total solar eclipse of August 1999 in Elazig, Turkey. In this
instrument one end of the twenty fiber optic tips at the focal plane
of the telescope were positioned to see different radii and latitudes
of the solar corona. The other ends of the fibers were vertically
aligned and placed at the primary focus of the collimating lens of
the spectrograph. By isolating the K-coronal spectrum and calculating
the temperature and the wind sensitive intensity ratios we have
simultaneously measured both the thermal electron temperatures and the
solar wind velocities at some discrete locations on the solar corona.

---------------------------------------------------------
Title: Analysis of an Active Region EUV Spectrum from SERTS-97
Authors: Brosius, J. W.; Thomas, R. J.; Davila, J. M.; Landi, E.
2000SPD....31.0214B Altcode: 2000BAAS...32..813B
Goddard Space Flight Center's Solar EUV Research Telescope and
Spectrograph (SERTS) was flown on 1997 November 18, carrying
a CCD-intensified detector and a multilayer-coated toroidal
diffraction grating that enhanced the sensitivity over that of a
standard gold-coated grating throughout the instrument's first-order
waveband (299 -- 353 Angstroms). Spectra and spectroheliograms of NOAA
active region 8108 (N21 E18) were obtained with a spectral resolution
(instrumental FWHM) ~ 118 m Angstroms. Spectra and spectroheliograms
of quiet areas southeast of the active region were also obtained. An
end-to-end radiometric calibration of the rocket instrument was
carried out at Rutherford-Appleton Laboratory in the same facility
used to calibrate the Coronal Diagnostic Spectrometer (CDS) on the
Solar and Heliospheric Observatory (SOHO) satellite, using the same
EUV light source. The accuracy of this calibration is confirmed by
the excellent agreement between measured and theoretical values of
density- and temperature-insensitive line intensity ratios among some
of the nearly 100 spectral lines observed in the spatially averaged
active region spectrum. We present the spectrum itself, and discuss
measurements of the plasma density, non-thermal mass motions, relative
wavelength shifts, and the differential emission measure. This work
is supported by NASA through RTOP grants and contract NAS5-99145.

---------------------------------------------------------
Title: Coronal Seismology: Using Oscillations to Understand Coronal
Structure
Authors: Davila, J. M.
2000SPD....31.0602D Altcode: 2000BAAS...32Q.838D
Recent high resolution observations from TRACE have demonstrated
that oscillations in the corona can be observed from space. In this
paper we consider the following question. What is the nature of these
motions, and how can they be used to understand something about the
corona? We briefly review some of the observational results, and
discuss the interpretation of these results within the framework of
MHD wave propagation and damping in coronal loops, open flux tubes,
and loops with cusp structures. The prospect for future improvements
in the theory and observations will be discussed.

---------------------------------------------------------
Title: New Diagnostics of Coronal Heating and Solar Wind Acceleration
Processes Achievable With The Advanced Solar Coronal Explorer (ASCE)
Authors: Cranmer, S. R.; Kohl, J. L.; Gardner, L. D.; Raymond, J. C.;
Strachan, L.; Smith, P. L.; Howard, R. A.; Davila, J. M.; Fisher,
R. R.; Noci, G.; Tondello, G.; Socker, D. G.; Moses, D.
2000SPD....31.0297C Altcode: 2000BAAS...32..828C
The Advanced Solar Coronal Explorer (ASCE) is a proposed NASA
Medium-class Explorer (MIDEX) mission that underwent a detailed
Concept Study in 1999. The science payload includes large aperture EUV
and visible light coronagraphs. ASCE's unprecedented spectral range,
spatial resolution, and sensitivity (30 to 100 times the EUV sensitivity
of UVCS/SOHO) provide measurements needed to investigate the role of
high-frequency and low-frequency waves in heating and accelerating
the fast and slow speed solar wind. This presentation will outline
the advanced capabilities of ASCE for obtaining detailed empirical
descriptions of solar wind acceleration regions, specifying coronal
temperatures, flow speeds, densities, and elemental abundances. Velocity
distributions for electrons and more than 10 to 20 ion species with
mass-to-charge ratios from 4 to 1 (including singly ionized helium) can
be measured by ASCE in coronal holes and streamers. This information
is sufficient to derive the wavenumber power spectrum of magnetic
fluctuations that affect the primary electron/proton plasma. The main
goal is to identify the physical processes responsible for heating
and acceleration of the primary particles and minor ions in the fast
and slow speed solar wind.

---------------------------------------------------------
Title: SUMI: The Solar Ultraviolet Magnetograph
Authors: Davis, J. M.; Porter, J. G.; Gary, G. A.; West, E. A.; Rabin,
D. M.; Thomas, R. J.; Davila, J. M.
2000SPD....31.0299D Altcode: 2000BAAS...32..828D
A major focus of solar physics is the measurement of the temporal
and spatial variability of solar magnetic fields from the photosphere
into the lower corona, together with the study of how their behavior
produces the dynamic phenomena in this region such as flares and
CMEs. Considerable success has been achieved in the characterization of
the full vector field in the photosphere, where β , the ratio of the
gas pressure to the magnetic pressure, is gtrsim1. At higher levels
in the atmosphere where β &lt;&lt;1, the magnetic field (through
the Lorentz force) controls the structure and dynamics of the solar
atmosphere, and rapid changes in structure with release of energy
become possible. However, observations of the field at these higher
levels have proven to be difficult, placing a serious limitation on our
understanding of the physical processes occurring there. This poster
will discuss the Solar Ultraviolet Magnetograph Investigation (SUMI),
a hardware development study for an instrument capable of measuring
the polarization in ultraviolet lines of C IV and Mg II formed in the
transition region and upper chromosphere. We are currently developing
optical technologies necessary to build an instrument that will
achieve a major advance in performance over that of earlier attempts
(e.g., SMM/UVSP). Initially configured as a sounding rocket payload,
such a UV magnetograph would allow us to make exploratory measurements
extending the observation of solar magnetic fields into new and dynamic
regimes. This work is supported by NASA through the SEC Program in
Solar Physics and the program for Technology Development for Explorer
Missions and Sofia.

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Title: Mission to Provide First Stereo Views of Solar Eruptions
Authors: Guhathakurta, M.; Davila, J. M.
2000SPD....31.1603G Altcode: 2000BAAS...32..849G
STEREO mission will for the first time unveil the Sun in three
dimensions. Its objective is to address the origin, evolution and
interplanetary consequences of one the most massive disturbances in
our solar system called the coronal mass ejection (CME). This will
be achieved by sending two identically instrumented spacecraft, both
at 1 AU orbit around the Sun, but one flying well ahead of the Earth
and one behind. The instrument suite for STEREO will characterize
the CME plasma all the way from the solar surface to the orbit of
the Earth. These instruments will measure physical characteristics
of CME's with remote sensing and local sensing instruments, allowing
scientists to determine solar origins of CME's, their propagation into
the interplanetary medium and ultimately their consequences on Earth's
magnetic field. By viewing CME's from two different vantage points,
STEREO will be able to pinpoint their speed and distance from Earth,
and thus more accurately time the arrival of the plasma cloud. The
planned 2004 launch date will enable STEREO to make observations during
the simpler, declining phase of the current activity cycle, which is
expected to reach solar maximum around the year 2000. The STEREO mission
is a multilateral international collaboration involving participants
from France, Germany, the United States, and United Kingdom. STEREO is
the third mission within NASA's Solar-Terrestrial Probe (STP) Program,
under the Agency's Sun-Earth Connections Theme.

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Title: SERTS-97 Measurements Of Relative Wavelength Shifts In Coronal
Emission Lines Across A Solar Active Region
Authors: Brosius, J. W.; Thomas, R. J.; Davila, J. M.; Thompson, W. T.
2000SoPh..193..117B Altcode:
We used slit spectra from the 18 November 1997 flight of Goddard Space
Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-97)
to measure relative wavelength shifts of coronal emission lines as a
function of position across NOAA active region 8108. The shifts are
measured relative to reference wavelengths derived from spectra of the
region's nearby quiet surroundings (not necessarily at rest) because
laboratory rest wavelengths for the coronal EUV lines have not been
measured to sufficient accuracy for this work. An additional benefit
to this approach is that any systematic uncertainties in the wavelength
measurements are eliminated from the relative shifts by subtraction. We
find statistically significant wavelength shifts between the spatially
resolved active region slit spectra and the reference spectrum. For
He ii 303.78 Å the maximum measured relative red shift corresponds
to a Doppler velocity ∼+13 km s−1, and the maximum
relative blue shift corresponds to a Doppler velocity ∼−3 km
s−1. For Si x 347.40 Å, Si xi 303.32 Å, Fe xiv 334.17
Å, and Fe xvi 335.40 Å the corresponding maximum relative Doppler
velocities are ∼+19 and ∼−14, ∼+23 and ∼−7, ∼+10 and
∼−10, and ∼+13 and ∼−5 km s−1, respectively. The
active region appears to be divided into two different flow areas;
hot coronal lines are predominantly red-shifted in the northern half
and either blue-shifted or nearly un-shifted in the southern half. This
may be evidence that material flows up from the southern part of the
region, and down into the northern part. Qualitatively similar relative
wavelength shifts and flow patterns are obtained with SOHO/CDS spectra.

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Title: Winds from Luminous Late-Type Stars. I. The Effects of
Nonlinear Alfvén Waves
Authors: Airapetian, V. S.; Ofman, L.; Robinson, R. D.; Carpenter,
K.; Davila, J.
2000ApJ...528..965A Altcode:
We present the results of magnetohydrodynamic (MHD) modeling of winds
from luminous late-type stars using a 2.5-dimensional, nonlinear MHD
computer code. We assume that the wind is generated within an initially
hydrostatic atmosphere and is driven by torsional Alfvén waves
generated at the stellar surface. Two cases of atmospheric topology
are considered: case I has longitudinally uniform density distribution
and isotropic radial magnetic field over the stellar surface, and case
II has an isotropic, radial magnetic field with a transverse density
gradient, which we refer to as an “atmospheric hole.” We use the
same set of boundary conditions for both models.The calculations
are designed to model a cool luminous star, for which we assume an
initial hydrostatic pressure scale height of 0.072 R*,
an Alfvén wave speed of 92 km s-1 at the surface, and a
wave period of 76 days, which roughly corresponds with the convective
turnover time. For case I the calculations produce a wind with terminal
velocity of ~22 km s-1 and a mass loss rate comparable to the
expected value of 10-6 Msolar yr-1. For
case II we predict a two-component wind: a fast (25 km s-1)
and relatively dense wind outside of the atmospheric hole and a slow
(15 km s-1), rarefied wind inside of the hole.

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Title: SERTS-95 Measurements of Wavelength Shifts in Coronal Emission
Lines Across a Solar Active Region
Authors: Brosius, Jeffrey W.; Thomas, Roger J.; Davila, Joseph M.
1999ApJ...526..494B Altcode:
We used slit spectra from the 1995 flight of Goddard Space Flight
Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-95) to
measure wavelength shifts of coronal emission lines in the core of
NOAA active region 7870 relative to its immediate surroundings (its
“edge”). This method circumvents the unavailability of reliable
laboratory rest wavelengths for the observed lines by using wavelengths
from the edge spectrum as references. We derived the SERTS-95
wavelength calibration from measurements of a post-flight laboratory
spectrum containing 28 He II and Ne II EUV standard wavelengths known
to high accuracy. Wavelength measurements for lines of He I, Ne III,
and additional lines of Ne II in the laboratory calibration spectrum
provide more accurate values than were previously available, enabling
these lines also to serve as future calibration standards. Six solar
lines were chosen for this study, namely, He II at 303.78 Å, Fe XII at
193.51 Å, Fe XIII at 202.05 Å, Fe XIV at 211.33 Å, Fe XV at 284.15
Å, and Fe XVI at 335.41 Å. Because these lines are free from known
blends in the SERTS-95 spectra and are either intrinsically strong or
near the SERTS-95 peak sensitivity, they are our most reliable lines
for measuring relative wavelength shifts in the spatially resolved
active-region core spectra. The iron ions are the hottest ions ever
used for this type of analysis. All six lines reveal statistically
significant spatial variations in their measured relative wavelength
shifts in the active-region core, including mixtures of blueshifts and
redshifts (each with maximum values corresponding to relative Doppler
velocities ~15 km s-1), indicating a dynamic, turbulent
corona. For each of these lines we calculated weighted-average relative
Doppler velocities from the wavelength shifts in the spatially resolved
core spectra by weighting the shifts in the individual spatial pixels
with their respective measurement uncertainties. This yields velocities
of 3.3+/-1.1 km s-1 for He II, 5.2+/-1.6 km s-1
for Fe XII, 0.7+/-1.5 km s-1 for Fe XIII, -2.1+/-1.4 km
s-1 for Fe XIV, 1.0+/-1.1 km s-1 for Fe XV,
and -1.1+/-0.8 km s-1 for Fe XVI. We also calculated
intensity-weighted relative Doppler velocities from the wavelength
shifts in the spatially averaged core spectrum, obtaining corresponding
values of 5.8+/-0.6 km s-1, 5.7+/-0.9 km s-1,
0.4+/-0.7 km s-1, -2.1+/-1.0 km s-1, 0.8+/-0.8
km s-1, and -1.1+/-0.5 km s-1. Combining the
above six lines with several additional ones that are strong enough
in both the edge and average core spectra to provide reliable centroid
measurements, we find statistically significant net relative redshifts
for lines of He II, Fe X, Fe XI, and Fe XII; lines of Fe XIII and Fe XV
show no significant shift while lines of Si XI, Fe XIV, and Fe XVI show
a small net relative blueshift. Where multiple lines are available for
a given ion, the directions (red or blue) and magnitudes (except for Fe
XI) of the relative shifts are mutually consistent. The net relative
blueshift observed in the hottest active-region coronal lines in our
sample, combined with the net relative redshift observed in the cooler
active-region coronal lines, suggests a net upflow of heated material
cospatially and cotemporally with a net downflow of cooler material.

---------------------------------------------------------
Title: Concept Study Report: Extreme-Ultraviolet Imaging Spectrometer
Solar-B
Authors: Doschek, George A.; Brown, Charles M.; Davila, Joseph M.;
Dere, Kenneth P.; Korendyke, Clarence M.; Mariska, John T.; Seely,
John F.
1999STIN...0011153D Altcode:
We propose a next generation Extreme-ultraviolet Imaging Spectrometer
(EIS) that for the first time combines high spectral, spatial, and
temporal resolution in a single solar spectroscopic instrument. The
instrument consists of a multilayer-coated off-axis telescope mirror
and a multilayer-coated grating spectrometer. The telescope mirror
forms solar images on the spectrometer entrance slit assembly. The
spectrometer forms stigmatic spectra of the solar region located
at the slit. This region is selected by the articulated telescope
mirror. Monochromatic images are obtained either by rastering the solar
region across a narrow entrance slit, or by using a very wide slit
(called a slot) in place of the slit. Monochromatic images of the
region centered on the slot are obtained in a single exposure. Half
of each optic is coated to maximize reflectance at 195 Angstroms; the
other half to maximize reflectance at 270 Angstroms. The two Extreme
Ultraviolet (EUV) wavelength bands have been selected to maximize
spectral and dynamical and plasma diagnostic capabilities. Spectral
lines are observed that are formed over a temperature range from about
0.1 MK to about 20 MK. The main EIS instrument characteristics are:
wavelength bands - 180 to 204 Angstroms; 250 to 290 Angstroms; spectral
resolution - 0.0223 Angstroms/pixel (34.3km/s at 195 Angstroms and
23.6 km/s at 284 Angstroms); slit dimensions - 4 slits, two currently
specified dimensions are 1" x 1024" and 50" x 1024" (the slot);
largest spatial field of view in a single exposure - 50" x 1024";
highest time resolution for active region velocity studies - 4.4 s.

---------------------------------------------------------
Title: The Role of Velocity Redistribution in Enhancing the Intensity
of the He II 304 A Line in the Quiet Sun Spectrum
Authors: Andretta, Vincenzo; Jordan, Stuart D.; Brosius, Jeffrey W.;
Davila, Joseph M.; Thomas, Roger J.; Behring, William E.; Thompson,
William T.; Garcia, Adriana
1999STIN...9909151A Altcode:
We present observational evidence of the effect of small scale
("microturbulent") velocities in enhancing the intensity of the He
II lambda304 line with respect to other transition region emission
lines, a process we call "velocity redistribution". We first show
results from the 1991 and 1993 flights of SERTS (Solar EUV Rocket
Telescope and Spectrograph). The spectral resolution of the SERTS
instrument was sufficient to infer that, at the spatial resolution
of 5", the line profile is nearly gaussian both in the quiet Sun and
in active regions. We were then able to determine, for the quiet Sun,
a lower limit for the amplitude of non-thermal motions in the region
of formation of the 304 A line of the order of 10 km/s. We estimated
that, in the presence of the steep temperature gradients of the solar
Transition Region (TR), velocities of this magnitude can significantly
enhance the intensity of that line, thus at least helping to bridge
the gap between calculated and observed values. We also estimated the
functional dependence of such an enhancement on the relevant parameters
(non-thermal velocities, temperature gradient, and pressure). We then
present results from a coordinated campaign, using SOHO/CDS and H-alpha
spectroheliograms from Coimbra Observatory, aimed at determining
the relationship between regions of enhanced helium emission and
chromospheric velocity fields and transition region emission in the
quiescent atmosphere. Using these data, we examined the behavior of
the He II lambda304 line in the quiet Sun supergranular network and
compared it with other TR lines, in particular with O III lambda600. We
also examined the association of 304 A emission with the so-called
"coarse dark mottle", chromospheric structures seen in H-alpha red
wing images and associated with spicules. We found that all these
observations are consistent with the velocity redistribution picture.

---------------------------------------------------------
Title: Spectroscopic study of the solar eclipse of August 1999 to
understand the radial and latitudinal profiles of wind and temperature
Authors: Reginald, N. L.; Davila, J. M.
1999AAS...19410802R Altcode:
The determination of the radial temperature and the wind profiles of
the solar corona is of immense importance in understanding the coronal
heating mechanism and the dynamics of the coronal features. Cram (1976)
provides the theory for the formation of the K-coronal spectrum and a
method for determining the radial profile of the coronal temperature. A
slit-based spectroscopic study has been performed by Ichimoto et.al
(1996) on the solar corona in conjunction with a solar eclipse to
evaluate the radial temeperature profiles of the solar corona. We
have modified Cram's theory to incorporate the role of the solar
wind in the formation of the K-corona. We are building a fiber optic
based spectrograph to study the solar eclipse of August 1999. In this
instrument one end of the twenty-five fiber tips at the focal plane
of the telescope are positioned to see different radii and latitudes
of the solar corona. The other ends of the fibers are vertically
aligned and placed at the primary focus of the collimating lens of
the spectrograph. By calculating the intensity ratios at wind and
temperature sensitive wavelengths we believe that both the temperature
and wind profiles could be determined at different radii and latitudes.

---------------------------------------------------------
Title: TRACE observation of damped coronal loop oscillations:
Implications for coronal heating
Authors: Nakariakov, V. M.; Ofman, L.; Deluca, E. E.; Roberts, B.;
Davila, J. M.
1999Sci...285..862N Altcode:
The imaging telescope on board the Transition Region and Coronal
Explorer (TRACE) spacecraft observed the decaying transversal
oscillations of a long [(130 ± 6) × 106 meters], thin
[diameter (2.0 ± 0.36) × 106 meters], bright coronal
loop in the 171 angstrom FeIX emission line. The oscillations were
excited by a solar flare in the adjacent active region. The decay
time of the oscillations is 14.5 ± 2.7 minutes for an oscillation
with a frequency 3.90 ± 0.13 millihertz. The coronal dissipation
coefficient is estimated to be eight to nine orders of magnitude
larger than the theoretically predicted classical value. The larger
dissipation coefficient may solve existing difficulties with wave
heating and reconnection theories.

---------------------------------------------------------
Title: Two-fluid 2.5D MHD model of the fast solar wind and the
effective proton temperature
Authors: Ofman, L.; Davila, J. M.
1999AIPC..471..405O Altcode: 1999sowi.conf..405O
Recent SOHO/UVCS observations indicate that the perpendicular proton
and ion temperatures are much larger than electron temperatures (Kohl et
al. 1997). In the present study we simulate numerically the solar wind
flow in a coronal hole with the two-fluid approach. For simplicity,
we neglect electron inertia. We investigate the effects of electron
and proton temperatures on the solar wind acceleration by nonlinear
waves. In the model the nonlinear waves are generated by Alfvén waves
with frequencies in the 10-3 Hz range, driven at the base
of the coronal hole. The resulting electron and proton flow profile
exhibits density and velocity fluctuations. The fluctuations may steepen
into shocks as they propagate away from the sun. We construct the proton
velocity distribution and a synthetic Ly-α line profile by including
the combined effects of temperature and velocity fluctuations in the
model, and compare them to the UVCS observations.

---------------------------------------------------------
Title: The SERTS-97 Cross-Calibration of CDS &amp; EIT on SOHO
Authors: Thomas, R. J.; Davila, J. M.; Thompson, W. T.; Kent, B. J.;
Hollandt, J.
1999AAS...194.1606T Altcode: 1999BAAS...31Q.850T
GSFC's Solar EUV Rocket Telescope and Spectrograph (SERTS) obtains
imaged high-resolution spectra of individual solar features, giving
information about the Sun's corona and upper transition region. Its
flight on 1997 November 18 had the additional goal of providing
radiometric and wavelength calibrations for several experiments on the
Solar and Heliospheric Observatory (SOHO) satellite mission. For that
purpose, an end-to-end radiometric calibration of the rocket instrument
was carried out at RAL in the same facility used to characterize the
CDS experiment on SOHO, and using the same EUV light source specially
re-calibrated by PTB against the synchrotron radiation of the electron
storage ring BESSY, which is a primary EUV radiometric standard. Scans
of the SERTS aperture over a range of pitch and yaw angles were made to
determine the instrument's absolute spectral sensitivity to &lt;= 25%
at 12 wavelengths covering its range of 300 -- 365 Angstroms. Also, pre-
and post-flight wavelength calibrations were done at GSFC using well
known lines of He II and Ne II within the SERTS bandpass. For the first
time, SERTS-97 carried an EUV solar flux monitor kindly provided by USC;
its readings were used to validate our calculations of atmospheric
EUV transmission over the rocket's trajectory. During the flight,
SERTS-97 and CDS observed the same solar locations, as demonstrated by
subsequent data co-registration with EIT images, allowing the SERTS
calibrations to be directly applied to both CDS and EIT. Since SERTS
clearly resolves the strong Si XI and He II lines blended in EIT's
304 Angstroms channel, SERTS measurements give information on the
spectral composition of these images as well. Examples of the various
cross-calibrations will be shown. This work has been supported through
RTOP grants for the SERTS and SOHO programs from the Solar Physics
Office of NASA's Space Physics Division.

---------------------------------------------------------
Title: Determination of the Reynolds number from TRACE Observation
of Damped Coronal Loop Oscillations Induced by a Flare
Authors: Ofman, L.; Nakariakov, V. M.; Deluca, E.; Roberts, B.;
Davila, J. M.
1999AAS...194.7909O Altcode: 1999BAAS...31..964O
The Transition Region and Coronal Expolorer (TRACE) observes the solar
corona with unprecedented spatial and temporal resolution. We analyzed
active region loop observation in the 171 Angstroms Fe IX emission line,
and report the direct observations of damped transverse oscillations
of a long (130+/-6 Mm) thin (diameter 2+/-0.36 Mm) bright active region
loop. The oscillations were detected following a flare in the adjacent
active region. We determined the oscillation frequency and the decay
time by the least-square fit of an exponentially decaying sinusoidal
function. Using the dispersion relation for the transverse oscillations,
and the observed loop geometry we estimated the Alfven crossing time
in the loop. The Alfven time can be used to determine the magnetic
field strength in the loop if the density is known. All parts of the
loop were observed to oscillate transversly in-phase, implying that the
ocillation is a global mode of the loop. Using dissipative MHD model for
resonant absorption of global mode oscillations for the coronal loop
we determined the Reynolds number that produces the observed damping
rate of the observed global mode. The value of the Reynolds number is
in the 10(5-10^6) range, which is eight to nine orders of magnitude
smaller than the classical coronal value. We discuss the important
implication of the small Reynolds number on coronal heating theories.

---------------------------------------------------------
Title: The Advanced Solar Coronal Explorer Mission (ASCE)
Authors: Kohl, J.; Cranmer, S.; Gardner, L.; Golub, L.; Raymond, J.;
Smith, P. L.; Strachan, L.; Howard, R.; Moses, D.; Socker, D.; Wang,
D.; Fisher, R. R.; Davila, J.; St. Cyr, C.; Noci, G.; Tondello, G.
1999AAS...194.6506K Altcode: 1999BAAS...31Q.928K
The Advanced Solar Coronal Explorer (ASCE) mission was selected
for a Phase A Concept Study in the current round of proposed MIDEX
missions. It addresses three fundamental problems: 1) What physical
processes heat coronal holes and drive the fast solar wind? 2) What
physical processes heat streamers and drive the slow solar wind? and 3)
How are coronal mass ejections (CMEs) heated and accelerated, and what
role to they play in the evolution of the solar magnetic field. ASCE
has two instruments, the Spectroscopic and Polarimetric Coronagraph
(SPC) and the Extreme Ultraviolet Imager (EUVI). A deployable boom
supports a distant external occulter that allows large aperture optics
for the SPC coronagraphic channels. SPC's EUV channels will provide
spectroscopy of the extended solar corona with 30 - 200 times the
sensitivity of UVCS/SOHO and the first He II 30.4 nm spectroscopy of
the extended corona. SPC's Large Aperture Spectroscopic Coronagraph
channel will provide two orders of magnitude improvement in stray
light suppression for wide field visible spectroscopy and 2 arcsec
resolution elements for imaging and polarimetry. EUVI provides full
disk imaging with 0.9 arcsec resolution elements and extremely high
cadence. ASCE is designed to determine the thermal, kinetic, and
wave energy densities in coronal structures, determine the rates of
transformation among these forms of energy, their flow in space, and
their loss to radiation, and determine the composition and ionization
state of the corona in static and transient conditions.

---------------------------------------------------------
Title: The SERTS-97 rocket experiment to study activity on the Sun:
flight 36.167-GS on 1997 November 18.
Authors: Swartz, Marvin; Condor, Charles E.; Davila, Joseph M.; Haas,
J. Patrick; Jordan, Stuart D.; Linard, David L.; Miko, Joseph J.;
Nash, I. Carol; Novello, Joseph; Payne, Leslie J.; Plummer, Thomas
B.; Thomas, Roger J.; White, Larry A.; Brosius, Jeffrey W.; Thompson,
William T.
1999sret.book.....S Altcode:
This paper describes mainly the 1997 version of the Solar EUV Rocket
Telescope and Spectrograph (SERTS-97), a scientific experiment that
operated on NASA's suborbital rocket flight 36.167-GS. Its function
was to study activity on the Sun and to provide a cross calibration
for the CDS instrument on the SOHO satellite.

---------------------------------------------------------
Title: Two-fluid 2.5D MHD Simulations of the Fast Solar Wind in
Coronal Holes and the Relation to UVCS Observations
Authors: Davila, J. M.; Ofman, L.
1999SSRv...87..165D Altcode:
Recent SOHO/UVCS observations indicate that the perpendicular proton
and ion temperatures are much larger than electron temperatures. In
the present study we simulate numerically the solar wind flow in a
coronal hole with the two-fluid approach. We investigate the effects
of electron and proton temperatures on the solar wind acceleration
by nonlinear waves. In the model the nonlinear waves are generated
by Alfvén waves with frequencies in the 10-3 Hz range,
driven at the base of the coronal hole. The resulting electron and
proton flow profile exhibits density and velocity fluctuations. The
fluctuations may steepen into shocks as they propagate away from
the sun. We calculate the effective proton temperature by combining
the thermal and wave velocity of the protons, and find qualitative
agreement with the proton kinetic temperature increase with height
deduced from the UVCS Ly-α observations by Kohl et al. (1998).

---------------------------------------------------------
Title: Solar Active Region and Quiet-Sun Extreme-Ultraviolet Spectra
from SERTS-95
Authors: Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.
1998ApJS..119..255B Altcode:
Goddard Space Flight Center's Solar EUV Rocket Telescope and
Spectrograph was flown on 1995 May 15 (SERTS-95), carrying a
multilayer-coated toroidal diffraction grating that enhanced the
instrumental sensitivity in its second-order wave band (171-225
Å). Spectra and spectroheliograms of NOAA active region 7870 (N09 W22)
were obtained in this wave band with a spectral resolution (instrumental
FWHM) ~30 mÅ and in the first-order wave band (235-335 Å) with a
spectral resolution ~55 mÅ. Spectra and spectroheliograms of quiet-Sun
areas northeast of the active region were also obtained. We derived
the SERTS-95 relative radiometric calibration directly from flight
data by means of density- and temperature-insensitive line intensity
ratios. Most theoretical values for such ratios were obtained from the
CHIANTI database. A total of 44 different lines were used to derive
the relative radiometric calibration in the two spectral orders,
most of them coming from seven (Fe X-Fe XVI) of the nine (Fe IX-Fe
XVII) observed ionization stages of iron. The resulting relatively
calibrated line intensities agree well with their corresponding
normalized theoretical values. This supports the overall accuracy
of the atomic physics parameters and demonstrates the power of the
technique. The present work extends earlier work by Brosius, Davila,
&amp; Thomas, who determined the SERTS-95 second-order response
using this technique. Many of the ratios employed here can be used to
carry out a similar calibration exercise on spectra from the Coronal
Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric
Observatory (SOHO). We placed the line intensities onto an absolute
scale by forcing our quiet-Sun He II λ303.8 + Si XI λ303.3 intensity
to match that from previous observations. The resulting active region
and quietSun absolutely calibrated line lists contain 127 and 20 lines,
respectively. Active region densities derived from density-sensitive
line intensity ratios of Fe X, XI, XIII, and XIV are mutually consistent
with log ne ~ 9.4 +/- 0.2; densities derived from Fe XII
are significantly greater (log ne ~ 10).

---------------------------------------------------------
Title: The SERTS-97 Cross-Calibration of CDS &amp; EIT on SOHO
Authors: Thomas, R. J.; Davila, J. M.; Thompson, W. T.; Kent, B. J.;
Hollandt, J.
1998AAS...19310006T Altcode: 1998BAAS...30Q1398T
GSFC's Solar EUV Rocket Telescope and Spectrograph (SERTS) obtains
imaged high-resolution spectra of individual solar features, giving
information about the Sun's corona and upper transition region. Its
flight on 1997 November 18 had the additional goal of providing
radiometric and wavelength calibrations for several experiments on the
Solar and Heliospheric Observatory (SOHO) satellite mission. For that
purpose, an end-to-end radiometric calibration of the rocket instrument
was carried out at RAL in the same facility used to characterize
the CDS experiment on SOHO, and using the same EUV light source
specially re-calibrated by PTB against the primary standard BESSY
synchrotron. Scans of the SERTS aperture over a range of pitch and
yaw angles were made to determine the instrument's absolute spectral
sensitivity to &lt;= 25% at 12 wavelengths covering its range of 300
-- 365 Angstroms. Also, pre- and post-flight wavelength calibrations
were done at GSFC using well known lines of He II and Ne II within the
SERTS bandpass. For the first time, SERTS-97 carried an EUV solar flux
monitor kindly provided by USC; its readings were used to validate
our calculations of atmospheric EUV transmission over the rocket's
trajectory. During the flight, SERTS-97 and CDS observed the same solar
locations, as demonstrated by subsequent data co-registration with
EIT images, allowing the SERTS calibrations to be directly applied to
both CDS and EIT. Since SERTS clearly resolves the strong Si XI and He
II lines blended in EIT's 304 Angstroms channel, SERTS measurements
give information on the spectral composition of these images as
well. Examples of the various cross-calibrations will be shown.

---------------------------------------------------------
Title: Solar wind acceleration by large-amplitude nonlinear waves:
Parametric study
Authors: Ofman, L.; Davila, J. M.
1998JGR...10323677O Altcode:
We investigate the parametric dependence of the solar wind acceleration
by large-amplitude nonlinear (LAN) magnetohydrodynamic waves. For
this purpose we model numerically the self-consistent problem of
the solar wind with waves by solving time-dependent, nonlinear,
resistive 2.5-dimensional (three-dimensional with azimuthal symmetry)
MHD equations driven by Alfvén waves. We find that when the Alfvén
wave amplitude is above a parameter-dependent threshold, LAN waves are
generated in the model coronal hole. For typical coronal parameters the
solar wind speed and density fluctuate considerably on a timescale of
~10-40 min and with an amplitude of up to several hundred kmilometers
per second near the Sun (r&lt;~10RS) in agreement with
recent interplanetary scintillation observations. The solar wind speed
is inversely dependent on the driving frequency in the range 0.35-3
mHz. The amplitude of the velocity fluctuations increases with the
amplitude of the magnetic field and the driving Alfvén waves at the
base of the corona and decreases with the coronal temperature. We found
that for the same typical solar wind and Alfvén wave parameters and an
isothermal initial atmosphere, the WKB model predicts 30% higher flow
velocities far from the Sun (32RS) than our self-consistent
wave model with high-frequency Alfvén waves (f=2.78mHz), conforming
to the WKB approximation. However, our model predicts significantly
higher average flow speed near the Sun. When low-frequency non-WKB
waves drive the wind, our model predicts 25% higher solar wind speed
than the WKB model far from the Sun. This result of our model is in
agreement with linear studies of solar wind acceleration by Alfvén
waves that take into account Alfvén wave reflection.

---------------------------------------------------------
Title: Using Strong Solar Coronal Emission Lines as Coronal Flux
Proxies
Authors: Falconer, David A.; Jordan, Stuart D.; Brosius, Jeffrey W.;
Davila, Joseph M.; Thomas, Roger J.; Andreatta, Vicenzo; Hara, Hirohisa
1998SoPh..180..179F Altcode:
We investigate the possibility that strong EUV lines observed with the
Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) provide
good proxies for estimating the total coronal flux over shorter
wavelength ranges. We use coordinated SERTS and Yohkoh observations
to obtain both polynomial and power-law fits relating the broad-band
soft X-ray fluxes to the intensities of Fexvi 335 Ú and 361 Ú, Fexv
284 Ú and 417 Ú, and Mgix 368 Ú measured with SERTS. We found that
the power-law fits best cover the full range of solar conditions from
quiet Sun through active region, though not surprisingly the `cooler'
Mgix 368 Ú line proves to be a poor proxy. The quadratic polynomial
fits yield fair agreement over a large range for all but the Mgix
line. However, the linear fits fail conspicuously when extrapolated
into the quiet-Sun regime. The implications of this work for the Heii
304 Ú line formation problem are also briefly considered.

---------------------------------------------------------
Title: Calibration of the SERTS-95 Spectrograph from Iron Line
Intensity Ratios
Authors: Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.
1998ApJ...497L.113B Altcode:
Goddard Space Flight Center's Solar EUV Rocket Telescope and
Spectrograph was flown on 1995 May 15 (SERTS-95), carrying a
multilayer-coated toroidal diffraction grating which enhanced the
instrumental sensitivity within its second-order wave band (170-225
Å). Spectra and spectroheliograms of NOAA Active Region 7870 (N09/W22)
were obtained in this wave band with a spectral resolution (instrumental
FWHM) ~30 mÅ. We developed and applied a technique for deriving the
relative radiometric calibration independent of laboratory calibration
measurements by employing a method proposed by Neupert &amp; Kastner for
monitoring variations in the sensitivities of orbiting EUV spectrometers
by means of density- and temperature-insensitive line intensity
ratios. Numerous ratios of emission lines from Fe X-XIV are mutually
consistent and yield an instrumental response curve that matches the
design characteristics of the multilayer coating. This supports the
accuracy of the atomic physics parameters and demonstrates the power
of the technique. Many of the ratios employed here can be used to
carry out a similar calibration exercise on spectra from the Coronal
Diagnostic Spectrometer's Grazing Incidence Spectrograph (CDS/GIS)
aboard the Solar and Heliospheric Observatory. Because they are
relatively free from blending with nearby strong lines, the following
density-sensitive ratios are particularly well suited for analysis
with the GIS: Fe X λ175.265/λ174.526, Fe X λ175.265/λ184.534,
Fe XII λ186.867/λ195.117, Fe XIII λ203.820/λ202.042, Fe XIII
λ200.017/λ202.042, and Fe XIV λ219.121/λ211.317. Densities derived
from Fe X, XIII, and XIV yield log ne~9.4+/-0.2.

---------------------------------------------------------
Title: The Magnetic Reconnection Explorer (MAGREX)
Authors: Schühle, U.; Antionchos, S. K.; Barbee, T. W., Jr.; Bixler,
J. V.; Brown, C. M.; Carter, P. H., II; Curdt, W.; Davila, J. M.;
Doschek, G.; Feldman, U.; Goldstein, W. H.; Kordas, J.; Lemaire, P.;
Mariska, J. T.; Marsch, E.; Moses, J. D.; Seely, J. F.; Wilhelm, K.;
Woods, T. N.
1998ESASP.417..289S Altcode: 1998cesh.conf..289S
No abstract at ADS

---------------------------------------------------------
Title: Observing the inner heliosphere from new perspectives
Authors: Davila, Joseph M.
1998AdSpR..21..319D Altcode:
In the solar corona, the density scale height is large, a considerable
fraction of a solar radius. Because of this, observations of the Sun
from a single vantage point produce images which show an unavoidable
overlapping of many structures along the line of sight. This makes it
difficult, and sometimes impossible, to determine the true nature of the
feature being observed. This difficulty can be overcome by obtaining
simultaneous observations from multiple vantage points. Using these
observations, and a reconstructions process similar to that used in
medical imaging applications, the true three-dimensional nature of the
solar corona can be deduced. The same process can be used to follow
the formation of coronal mass ejections (CME's) in the low corona and
the propagation of CME's through interplanetary space.

---------------------------------------------------------
Title: A Self-consistent Model for the Resonant Heating of Coronal
Loops: The Effects of Coupling with the Chromosphere
Authors: Ofman, L.; Klimchuk, J. A.; Davila, J. M.
1998ApJ...493..474O Altcode:
We present the first model of resonant heating of coronal loops that
incorporates the dependence of the loop density on the heating rate. By
adopting the quasi-static equilibrium scaling law ρ ~ Q5/7,
where ρ is the density and Q is the volumetric heating rate, we
are able to approximate the well-known phenomena of chromospheric
evaporation and chromospheric condensation, which regulate the coronal
density. We combine this scaling law with a quasi-nonlinear MHD model
for the resonant absorption of Alfvén waves in order to study the
spatial and temporal dependence of the heating. We find that the heating
is concentrated in multiple resonance layers, rather than in the single
layer of previous models, and that these layers drift throughout the
loop to heat the entire volume. These newfound properties are in much
better agreement with coronal observations.

---------------------------------------------------------
Title: European Plans for the Solar/Heliospheric Stereo Mission
Authors: Bothmer, V.; Bougeret, J. -L.; Cargill, P.; Davila, J.;
Delaboudiniere, J. -P.; Harrison, R.; Koutchmy, S.; Liewer, P.;
Maltby, P.; Rust, D.; Schwenn, R.
1998ESASP.417..145B Altcode: 1998cesh.conf..145B
No abstract at ADS

---------------------------------------------------------
Title: Two-Component Winds from Luminous Late-Type Stars
Authors: Airapetian, V. S.; Offman, L.; Robinson, R.; Carpenter, K.;
Davila, J.
1998BAAS...30..760A Altcode:
We present the results of a magnetohydrodynamic (MHD) simulation
of winds from luminous late-type stars using a 2.5D, non-linear MHD
computer code. In this simulation we assume that the wind is generated
within a hydrostatic atmosphere with an initial isothermal pressure
scale height of 0.072 Rstar and a radial magnetic field. We
also assume a transverse density gradient which we we refer to as a
“chromospheric hole”. Tortional Alfven waves are generated at the
stellar surface by a forcing function having a single frequency, which
is comparable to the turn-over frequency of convective cells in giant
stars. To ensure that we are accurately assessing the terminal velocity
of the wind, we carried out the calculations to a height of 20 stellar
radii and a time period of more than 180 Alfven transit times, which
ensures that a steady state has been reached. In the higher density
(low Alfven velocity) regions outside of the “chromospheric hole” the
Alfven waves are freely propagating. Ponderomotive forces associated
with these waves drive radial, compressive motions and contribute to
stellar wind acceleration. The compressive motions then excite slow
magnetosonic waves which non-linearly steepen into solitary waves that
propagate on top of a background flow similar to the case of solar
coronal holes. This produces a fast (40-80 km/s) and relatively dense
component of the wind. In the lower density “chromospheric hole”
region the Alfven waves are strongly reflected and produce an outflow
with both radial and azimuthal velocities which are ~ 10% of the local
Alfven speed. This component of the wind is slow ( ~ 10-30 km/s) and
less dense than the wind initiated outside of the hole. Depending on
the magnetic topology in the atmosphere of a luminous late - type
star, we may therefore expect either one (fast) or two components
to the wind. Our results are consistent with recent observations of
two discrete components to the wind in the K5 III hybrid star gamma
Dra. These components were detected in the Mg II h and k resonance lines
and had velocities of 67 and 30 km/s, with the higher velocity component
having a mass loss rate which is 10 times that of the slower speed wind.

---------------------------------------------------------
Title: Atmospheric Dynamics of Luminous Late-Type Stars
Authors: Airapetian, V. S.; Ofman, L.; Robinson, R. D.; Carpenter,
K.; Davila, J.
1998ASPC..154.1569A Altcode: 1998csss...10.1569A
We present first results of magnetohydrodynamic (MHD) calculations of
winds from luminous late-type stars using an existing, 2.5D, non-linear
MHD code recently developed by Ofman &amp; Davila (e.g., Ofman &amp;
Davila 1997). We assume that the wind is initiated in a hydrostatic
atmosphere with an isothermal pressure scale height of 0.072 R* and a
“chromospheric hole” modeled by a transverse density structure and
a radial magnetic field. To ensure that we are accurately assessing
the terminal velocity of the wind, we carried out the calculations
to a height of 20 stellar radii. We find that in the higher density
(low Alfven velocity) regions outside of the “chromospheric hole” the
Alfven waves are freely propagating. Ponderomotive forces associated
with these waves drive radial, compressive motions and contribute to
stellar wind acceleration. The compressive motions then excite slow
magnetosonic waves which non-linearly steepen into solitary waves that
propagate on top of a background flow. This situation is similar to
solar coronal hole models. In the lower density “chromospheric hole”
region the Alfven wave are strongly reflected, and produce a substantial
outflow, with both radial and azimuthal velocities approaching the
local Alfven speed. Our results are in qualitative agreement with
observational signatures of winds in cool, luminous late-type stars.

---------------------------------------------------------
Title: Coordinated Observations with SOHO/CDS and SERTS
Authors: Thompson, W. T.; Thomas, R. J.; Davila, J. M.; Jordan, S. D.;
Brosius, J. W.
1998AAS...191.7316T Altcode: 1998BAAS...30..758T
On November 18, 1997, coordinated observations were made between the
Coronal Diagnostic Spectrometer (CDS) aboard the Solar and Heliospheric
Observatory (SOHO), and with the Solar Extreme-ultraviolet Rocket
Telescope and Spectrograph (SERTS). One of the primary goals of this
sounding rocket flight was to serve as a calibration underflight
for SOHO. SERTS observes resolved spectra over most of the short
wavelength channel of the CDS Normal Incidence Spectrograph, as well
as the He II 304 Angstroms line which is observed by CDS in second
order in the long wavelength channel. Observations were also made of
the full sun with the SOHO Extreme ultraviolet Imaging Telescope (EIT)
in its 304 Angstroms channel, allowing coalignment between all three
instruments. EIT also serves as a transfer standard of the alignment
to other full-sun observations. We will report on the status of the
data analysis from the SERTS-97 flight, and its comparison to CDS.

---------------------------------------------------------
Title: IPS Observations of the Solar Wind Velocity and the
Acceleration Mechanism
Authors: Ofman, L.; Davila, J. M.; Coles, W. A.; Grall, R. R.;
Klinglesmith, M. T.
1997ESASP.415..361O Altcode: 1997cpsh.conf..361O
No abstract at ADS

---------------------------------------------------------
Title: The Measurement of Solar Active Region Properties with EUV
Spectra and Spectroheliograms from SERTS
Authors: Brosius, J. W.; Davila, J. M.; Thomas, R. J.; White, S. M.
1997AAS...191.7315B Altcode: 1997BAAS...29.1323B
The Goddard Space Flight Center's Solar EUV Rocket Telescope and
Spectrograph (SERTS) was successfully flown on six different occasions,
and results from several of those flights are presented here. For the
flight of 1995 May 15, SERTS included a multilayer coated toroidal
diffraction grating which enhanced the throughput above that of a
standard gold coated grating for wavelengths between about 170 and
220 Angstroms, with a peak response around 192 Angstroms. Emission
lines in this wavelength range are seen in second order. First order
lines between about 235 and 335 Angstroms are also detected. A total
of nearly 140 lines are identifiable in the combined first and second
order wavebands. These include lines from several ionization stages of
Ca, Mg, Ni, S, and Si, as well as lines from at least nine ionization
stages of Fe (IX -- XVII). Many of the lines are useful for calibration
verification, plasma diagnostics, or both. Results from analyses
of the high spectral resolution (30 m Angstroms in second order,
and 55 m Angstroms in first), spatially resolved (4.4 arcsec spatial
resolution) active region spectra are presented. For the flight of 1993
August 17, SERTS included a multilayer coated grating which enhanced
the instrumental sensitivity within the first order waveband. For
this flight we also obtained coordinated Very Large Array (VLA) radio
observations at 20 and 6 cm wavelengths. Because the radio emission is
sensitive to the coronal magnetic field while the EUV emission is not,
we were able to derive solar coronal magnetograms from the combined
SERTS and VLA observations. (This work was supported by NASA grants
NASW-96006 and NASW-4933.)

---------------------------------------------------------
Title: Fast Solar Wind Acceleration by Nonlinear Waves in Coronal
Holes
Authors: Ofman, L.; Davila, J. M.
1997AAS...191.7414O Altcode: 1997BAAS...29.1326O
We use the 2.5D (3D with azimuthal symmetry) MHD equations to model
numerically the solar wind acceleration in a nonhomogeneous coronal
hole. We investigate the parametric dependence of the solar wind
acceleration by nonlinear MHD waves with a monochromatic and a broad
band driving source. We find that when the Alfven wave amplitude is
above a parameter dependent threshold , large amplitude nonlinear
longitudinal waves are generated and contribute to the radial
acceleration. The calculated solar wind speed and density fluctuates
considerably on a time scale of tens of minutes with an amplitude of
up to several hundred km/s near the sun (4R_sun&lt;r&lt;10R_sun). The
amplitude of the fluctuations decreases with the distance from the
sun. Using the monochromatic driver we find that the solar wind speed
and the amplitude of the nonlinear waves is inversely dependent on
the driving frequency in the range 0.3-3 mHz. The acceleration due to
the broad band driver depends on the power spectrum of the driver. The
amplitude of the nonlinear waves and the acceleration increases with
the magnitude of the magnetic field and decreases with the temperature
of the coronal hole.

---------------------------------------------------------
Title: Results from the November 1997 Flight of the Solar
Extreme-ultraviolet Rocket Telescope and Spectrograph (SERTS)
Authors: Davila, J. M.; Thomas, R. J.; Swartz, M.; Condor, C.; Linard,
D., II; Haas, P.; Miko, J.; Payne, L.
1997AAS...191.7312D Altcode: 1997BAAS...29.1322D
The SERTS current instrument obtains spatially resolved spectra of the
Sun in the wavelength range of 300-350 Angstroms. These spectra provide
information on the density and temperature of the solar corona in the
temperature range of 50,000 K to 5,000,000 K. The SERTS instrument has
been flown before, however the unique aspect of the most recent flight
is the opportunity to obtain fully calibrated spectral data. (See
companion paper on the calibration procedure by R. Thomas, et al.) In
additon during this flight co-observation with SOHO as well as Yohkoh
and the VLA will be obtained. The first look at these results will be
presented and discussed.

---------------------------------------------------------
Title: Coronal Magnetography of a Solar Active Region Using
Coordinated SERTS and VLA Observations
Authors: Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.;
White, Stephen M.
1997ApJ...488..488B Altcode:
We observed NOAA region 7563 simultaneously with Goddard Space Flight
Center's Solar EUV Rocket Telescope and Spectrogaph (SERTS) and with
the Very Large Array (VLA) on 1993 August 17. SERTS obtained spectra
in the 280-420 Å wavelength range, and images in the lines of Mg IX
λ368.1, Fe XV λ284.1, and Fe XVI λ335.4. The VLA obtained microwave
images at 20 and 6 cm wavelengths. The microwave emission depends upon
the coronal temperature, density, column emission measure, and magnetic
field; therefore, the coronal magnetic field can be derived when all of
these other quantities are measured. Here we demonstrate this approach
by using the SERTS data to derive all the relevant plasma parameters and
then fitting the radio observations to a magnetic field model in order
to determine the magnetic field structure. We used the method of
Monsignori-Fossi &amp; Landini and the coronal elemental abundances of
Feldman et al. to derive the differential emission measure (DEM) curve
for region 7563 from numerous EUV emission lines in spatially averaged
SERTS spectra. A similar curve was estimated for each point (i.e.,
each pixel or each spatial location) in the two-dimensional region by
scaling the average DEM curve with corresponding pixel intensities
in the Mg IX, Fe XV, and Fe XVI images. We integrated each such DEM
over narrow temperature ranges to obtain the column emission measure
(CEM) as a function of temperature, CEM(T). We also obtained electron
density measurements from EUV line intensity ratios in the spatially
averaged spectrum for several ionization stages of iron. These were
used to derive a functional relation between density and temperature,
ne(T). We derived the temperature dependence of the
coronal magnetic field [B(T)] at each point in the two-dimensional
region by incorporating CEM(T) and ne(T) into expressions for
the thermal bremsstrahlung and the gyroresonance opacities, and varying
B(T) so as to minimize the difference between the calculated and the
observed microwave intensities. The resulting calculated 20 and 6 cm
microwave intensity images reproduce the observed images very well. We
found that thermal bremsstrahlung alone is not sufficient to produce
the observed microwave intensities: gyroemission is required. Further,
contrary to several earlier studies, we found no evidence for cool,
absorbing plasma in the solar corona above the active region. The
coronal magnetic fields derived with our method typically exceed the
coronal fields extrapolated with a simple potential model, suggesting
the presence of coronal electric currents. However, in the diminutive
sunspot which dominates the 6 cm emission this difference is relatively
small, suggesting that the sunspot magnetic field itself is nearly
potential. Although we cannot firmly establish the uniqueness of our
solution in this particular case, the method is quite powerful and
should be repeated with other similar data sets. Variations in the
coronal elemental abundances could affect the determination of the
microwave emission mechanism(s), introduce evidence for the presence
of cool coronal plasma, and alter the strengths of the derived coronal
magnetic fields.

---------------------------------------------------------
Title: Obtaining the 3D Structure of Coronal Magnetic Loops from
Stereo Observations
Authors: Davila, Joseph M.
1997BAAS...29Q1119D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Solar-B Mission
Authors: Antiochos, Spiro; Acton, Loren; Canfield, Richard; Davila,
Joseph; Davis, John; Dere, Kenneth; Doschek, George; Golub, Leon;
Harvey, John; Hathaway, David; Hudson, Hugh; Moore, Ronald; Lites,
Bruce; Rust, David; Strong, Keith; Title, Alan
1997STIN...9721329A Altcode:
Solar-B, the next ISAS mission (with major NASA participation), is
designed to address the fundamental question of how magnetic fields
interact with plasma to produce solar variability. The mission has
a number of unique capabilities that will enable it to answer the
outstanding questions of solar magnetism. First, by escaping atmospheric
seeing, it will deliver continuous observations of the solar surface
with unprecedented spatial resolution. Second, Solar-B will deliver the
first accurate measurements of all three components of the photospheric
magnetic field. Solar-B will measure both the magnetic energy driving
the photosphere and simultaneously its effects in the corona. Solar-B
offers unique programmatic opportunities to NASA. It will continue an
effective collaboration with our most reliable international partner. It
will deliver images and data that will have strong public outreach
potential. Finally, the science of Solar-B is clearly related to the
themes of origins and plasma astrophysics, and contributes directly
to the national space weather and global change programs.

---------------------------------------------------------
Title: Relative Elemental Abundances of the Quiet Solar Corona as
Determined by SERTS
Authors: Falconer, D. A.; Davila, J. M.; Thomas, R. J.
1997ApJ...482.1050F Altcode:
Intensities of extreme-ultraviolet (EUV) spectral lines were
measured as a function of radius off the solar limb by two flights
(1989 May 5 and 1991 May 7) of the Solar Extreme-ultraviolet Rocket
Telescope and Spectrograph (SERTS) for three quiet solar regions. The
line-ratio density, line-ratio temperature, and emission measure were
determined. The relative abundances of silicon, aluminum, and chromium
to iron were determined. Results agreed with standard coronal relative
elemental abundances for one observation, but did not agree for the
other, in which aluminum was overabundant.

---------------------------------------------------------
Title: A Self-Consistent Model for the Resonant Heating of Coronal
Loops: the Effects of Coupling with the Chromosphere
Authors: Klimchuk, J. A.; Ofman, L.; Davila, J. M.
1997SPD....28.0504K Altcode: 1997BAAS...29..909K
The physical nature of coronal heating remains one of the great problems
of solar physics. One of the several theories that are being pursued
is the resonant absorption of MHD waves. While promising in several
respects, this theory has suffered from a glaring deficiency: the
computed heating is incompatible with both the assumed density and
the observed structure of coronal loops. We present the first model
of resonant heating of coronal loops that incorporates the dependence
of the loop density on the heating rate. By adopting the quasi-static
equilibrium scaling law rho ~ Q(5/7) , where rho is the density and Q is
the volumetric heating rate, we are able to approximate the well-known
phenomena of chromospheric evaporation and chromospheric condensation,
which regulate the coronal density. We combine this scaling law with
a linearized MHD model for the resonant absorption of Alfven waves
to study the spatial and temporal dependence of the heating. We find
that the heating is concentrated in multiple resonance layers, rather
than the single layer of previous models, and that these layers drift
throughout the loop to heat the entire volume. These new properties
are in much better agreement with coronal observations, including
recent observations from the CDS and EIT instruments on SOHO, as well
as earlier observations from the SXT instrument on Yohkoh.

---------------------------------------------------------
Title: The Structure and Properties of Solar Active Regions and
Quiet-Sun Areas Observed in Soft X-Rays with Yohkoh/SXT and in the
Extreme-Ultraviolet with SERTS
Authors: Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.;
Saba, Julia L. R.; Hara, Hirohisa; Monsignori-Fossi, Brunella C.
1997ApJ...477..969B Altcode:
We observed two solar active regions (NOAA regions 7563 and 7565),
quiet-Sun areas, and a coronal hole region simultaneously with Goddard
Space Flight Center's Solar EUV Rocket Telescope and Spectrograph
(SERTS) and with the Yohkoh Soft X-ray Telescope (SXT) on 1993 August
17. SERTS provided spatially resolved active region and quiet-Sun slit
spectra in the 280 to 420 Å wavelength range, and images in the lines
of He II λ303.8, Mg IX λ368.1, Fe XV λ284.1, and Fe XVI λλ335.4
and 360.8 SXT provided images through multiple broadband filters in both
the full-frame imaging mode and the partial-frame imaging mode. The
SERTS images in Fe XV (log Tmax = 6.33, where Tmax
is the temperature which maximizes the fractional ion abundance in
the available ionization equilibrium calculations, i.e., the formation
temperature) and Fe XVI (log Tmax = 6.43) exhibit remarkable
morphological similarity to the SXT images. Whereas the Fe XV and XVI
images outline the loop structures seen with SXT, the cooler He II
(log Tmax = 4.67) and Mg IX (log Tmax = 5.98)
images outline loop footpoints. In addition, the Mg IX emission
outlines other structures not necessarily associated with the hot
loops; these may be cool (T &lt;~ 1 × 106 K) loops. From the spatially resolved slit spectra, we obtained emission-line
profiles for lines of He II λ303.8, Mg IX λ368.1, Fe XIII λ348.2,
Si XI λ303.3, Fe XIV λ334.2, Fe XV λ284.1, and Fe XVI λ335.4
for each spatial position. Based upon the spatial variations of the
line intensities, active region 7563 systematically narrows when
viewed with successively hotter lines, and appears narrowest in the
broadband soft X-ray emission. The active region width (full width at
half-maximum intensity) diminishes linearly with log Tmax;
the linear fit yields an extrapolated effective log Tmax
of 6.51 +/- 0.01 for the X-ray emission. The most intense, central core
straddles the magnetic neutral line. Active region and quiet-Sun
one-dimensional temperature scans were derived from intensity ratios
of spatially resolved SERTS slit spectral lines, and from coregistered
SXT filter ratios. The highest plasma temperatures were measured in the
most intense, central core of region 7563. The temperatures derived
from Fe XVI λ335.4/Fe XV λ284.1 and Fe XVI λ335.4/Fe XIV λ334.2
vary significantly (based upon the measurement uncertainties) but not
greatly (factors of less than 1.5) across the slit. The average log
T values derived from the above two ratios for region 7563 are 6.39
+/- 0.04 and 6.32 +/- 0.02, respectively. Somewhat larger systematic
variations were obtained from all available SXT filter ratios. The
average active region log T values derived from the SXT AlMgMn/thin
Al, thick Al/thin Al, and thick Al/AlMgMn filter ratios are 6.33 +/-
0.03, 6.45 +/- 0.02, and 6.49 +/- 0.03, respectively. Active
region and quiet-Sun one-dimensional density scans were derived from
intensity ratios of spatially resolved SERTS slit spectral lines of
Fe XIII and Fe XIV. The derived densities show neither systematic nor
significant variations along the slit in either the active region or
the quiet-Sun, despite the fact that the intensities themselves vary
substantially. This indicates that the product of the volume filling
factor and the path length (fΔl) must be greater by factors of 3-5 in
the active region core than in the outskirts. Furthermore, the derived
active region densities are ~2 times the quiet-Sun densities. This
density difference is adequate to explain the factor of ~4 intensity
difference in Fe XII and Fe XIII between the active and quiet areas,
but it is not adequate to explain the factor of ~8 intensity difference
in Fe XIV between the active and quiet areas. We attribute the latter
to a greater fΔl in the active regions. Statistically significant
Doppler shifts are not detected in region 7563 or in the quiet-Sun
with any of the EUV lines.

---------------------------------------------------------
Title: Do First Results from SOHO UVCS Indicate That the Solar Wind
Is Accelerated by Solitary Waves?
Authors: Ofman, L.; Davila, J. M.
1997ApJ...476L..51O Altcode:
The Ultraviolet Coronagraph Spectrometer (UVCS) on board the recently
launched US-European Solar and Heliospheric Observatory (SOHO) satellite
has found O VI and H I emission lines with a broad component that
corresponds to ~300 km s-1 unresolved motions at about
0.7 solar radii above the photosphere. These motions appear to be
independent of ion mass. We suggest that the large Doppler broadening of
the ion emission lines observed by the UVCS are signatures of solitary
waves in the solar wind plasma. According to our recent 2.5-dimensional
(i.e., three-dimensional with azimuthal symmetry) MHD simulations,
these waves may contribute significantly to the solar wind acceleration
and may generate velocity fluctuations with a magnitude that agrees
with the above observations.

---------------------------------------------------------
Title: Solar Wind Acceleration by Solitary Waves in Coronal Holes
Authors: Ofman, L.; Davila, J. M.
1997ApJ...476..357O Altcode:
Coronal holes are well-known sources of the high-speed solar wind;
however, the exact acceleration mechanism of the fast wind is still
unknown. We solve numerically the time-dependent, nonlinear, resistive
2.5-dimensional MHD equations and find that solitary waves are generated
in coronal holes nonlinearly by torsional Alfvén waves. The solitary
wave phase velocity was found to be slightly above the sound speed
in the coronal hole; for example, with the driving Alfvén wave
amplitude vd ~ 36 km s-1 and plasma β = 5%,
the solitary wave phase speed is ~185 km s-1. We show with a
more simplified analytical model of the coronal hole that sound waves
are generated nonlinearly by Alfvén waves. We find numerically that
these waves steepen nonlinearly into solitary waves. In addition,
ohmic heating takes place in the coronal hole inhomogeneities owing
to phase-mixing of the torsional Alfvén waves. When solitary
waves are present, the solar wind speed and density fluctuate
considerably on timescales of ~20-40 minutes in addition to the
Alfvénic fluctuations. The solitary wave-driven wind might be in
better qualitative agreement with observations than the thermally
driven and WKB Alfvén wave solar wind models.

---------------------------------------------------------
Title: Possible Signatures of Nonlinear MHD Waves in the Solar Wind:
UVCS Observatio ns and Models
Authors: Ofman, L.; Romoli, M.; Davila, J. M.; Poletto, G.; Kohl,
J.; Noci, G.
1997ESASP.404..571O Altcode: 1997cswn.conf..571O
No abstract at ADS

---------------------------------------------------------
Title: Solitary waves in coronal holes-predicted signatures close
to the sun
Authors: Ofman, L.; Davila, J. M.
1997AIPC..385..227O Altcode: 1997recs.conf..227O
Coronal holes are well known sources of the high speed solar wind,
however, the exact acceleration mechanism of the wind is still
unknown. We find that solitary waves may be generated in coronal
holes nonlinearly by Alfvén waves. The solitary waves may efficiently
accelerate the fast solar wind in addition to thermal conduction. We
solve numerically the time-dependent, nonlinear, resistive 2.5-D MHD
equations in spherical geometry with azimuthal symmetry to model solar
wind acceleration by waves in coronal holes. Torsional Alfvén waves
are driven at the base of the model coronal hole and propagate into the
corona. Ohmic heating layers are found to occur at the coronal hole
boundaries due to phase-mixing of the torsional Alfvén waves. The
nonlinear coupling of the perpendicular (to the background magnetic
field) components of the velocity and the magnetic field to the radial
component of the momentum equation leads to the acceleration of the
solar wind in the radial direction and to the generation of solitary
waves. The solitary wave phase velocity was found to be above the sound
speed in the coronal hole, with the driving Alfvén wave amplitude
vd~25 km s-1, and plasma β=2.5%. We discuss
the implication of our results to the proposed in-situ observations
in the region r&lt;10Rs with the future solar probe mission.

---------------------------------------------------------
Title: A New Mechanism for Solar Wind Acceleration
Authors: Ofman, L.; Davila, J. M.
1997IAUJD..19E..34O Altcode:
We investigate the parametric dependence of a new solar wind
acceleration mechanism by nonlinear magneto-hydrodynamic waves, by
solving numerically the time-dependent, nonlinear, resistive 2.5-D
MHD equations. We find that large amplitude nonlinear longitudinal
waves are generated in coronal holes by torsional Alfven waves for
a broad range of parameters in the 10^6 K magnetized plasma. The
structure and the dependence of the phase speed on the amplitude of
these waves are similar to solitary waves. We find that the solar wind
speed and density fluctuate considerably on a time scales of ~20-40
min with an amplitude of several hundred km s^{-1}. The amplitude
of the radial velocity fluctuations increases with the amplitude of
the driving torsional Alfven waves at the base of the corona and the
magnetic field strength, decreases with the temperature, and nearly
independent of the driving frequency. The typical driving frequency
of the Alfven waves is in the mHz range, determined by wave reflection
in the radially stratified coronal hole, with an amplitude of 30-60 km
s^{-1}. For typical coronal hole parameters the nonlinear wave driven
wind accelerates to more than twice the Parker's solar wind speed and
is in qualitative agreement with recent SOHO observations.

---------------------------------------------------------
Title: The structure of the solar corona as observed by the Solar
Extreme Ultraviolet Rocket Telescope and Spectrograph
Authors: Davila, Joseph M.; Thomas, Roger J.; Brosius, Jeffrey;
Poland, Arthur
1997AdSpR..20.2293D Altcode:
Data from the Solar Extreme-ultraviolet Rocket Telescope and
Spectrograph (SERTS) have been used to address a number of important
scientific problems. The primary strength of the SERTS data is the
fact that this spectral range is rich with emission lines. Over 270
lines are seen in the SERTS active Sun spectrum, from 57 different
ions. For example, multiple (&gt;= 4) lines are observed for all
ionization states of iron from Fe IX to Fe XVII. Temperatures and
densities have been derived for a number of active and quiet Sun
regions, the coronal magnetic field strength has been estimated for
both a plage region and an active region.

---------------------------------------------------------
Title: STEREO: a solar terrestrial event observer mission concept
Authors: Socker, Dennis G.; Antiochos, S. K.; Brueckner, Guenter E.;
Cook, John W.; Dere, Kenneth P.; Howard, Russell A.; Karpen, J. T.;
Klimchuk, J. A.; Korendyke, Clarence M.; Michels, Donald J.; Moses,
J. Daniel; Prinz, Dianne K.; Sheely, N. R.; Wu, Shi T.; Buffington,
Andrew; Jackson, Bernard V.; Labonte, Barry; Lamy, Philippe L.;
Rosenbauer, H.; Schwenn, Rainer; Burlaga, L.; Davila, Joseph M.; Davis,
John M.; Goldstein, Barry; Harris, H.; Liewer, Paulett C.; Neugebauer,
Marcia; Hildner, E.; Pizzo, Victor J.; Moulton, Norman E.; Linker,
J. A.; Mikic, Z.
1996SPIE.2804...50S Altcode:
A STEREO mission concept requiring only a single new spacecraft has been
proposed. The mission would place the new spacecraft in a heliocentric
orbit and well off the Sun- Earth line, where it can simultaneously view
both the solar source of heliospheric disturbances and their propagation
through the heliosphere all the way to the earth. Joint observations,
utilizing the new spacecraft and existing solar spacecraft in earth
orbit or L1 orbit would provide a stereographic data set. The new
and unique aspect of this mission lies in the vantage point of the
new spacecraft, which is far enough from Sun-Earth line to allow an
entirely new way of studying the structure of the solar corona, the
heliosphere and solar-terrestrial interactions. The mission science
objectives have been selected to take maximum advantage of this new
vantage point. They fall into two classes: those possible with the
new spacecraft alone and those possible with joint measurements using
the new and existing spacecraft. The instrument complement on the new
spacecraft supporting the mission science objectives includes a soft
x-ray imager, a coronagraph and a sun-earth imager. Telemetry rate
appears to be the main performance determinant. The spacecraft could
be launched with the new Med-Lite system.

---------------------------------------------------------
Title: Tomography of the solar corona and the inner heliosphere:
the solar imaging of coronal extended structures (SLICES)
Authors: Davila, Joseph M.
1996SPIE.2804...62D Altcode:
In the solar corona, the density scale height is large, a considerably
fraction of a solar radius. Because of this, observations of the Sun
from a single vantage point produce images which show an unavoidable
overlapping of many structures along the line of sight. This makes it
difficult, and sometimes impossible, to determine the true nature of the
feature being observed. This difficulty can be overcome by obtaining
simultaneous observations from multiple vantage points. Using these
observations, and a reconstructions process similar to that used in
medical imaging applications, the true 3D nature of the solar corona
can be deduced. The same process can be used to follow the formation
of coronal mass ejections (CME's) in the low corona and the propagation
of CME's through interplanetary space.

---------------------------------------------------------
Title: Conceptual design for a solar instrument on the proposed
SPARTAN Lite spacecraft
Authors: Amato, Michael; Thomas, Roger J.; Davila, Joseph M.; Polidan,
Ronald S.
1996SPIE.2804..206A Altcode:
Spartan Lite is a proposed series of very low-cost spacecraft
missions which offer potential flight opportunities for pointed solar
experiments. Early versions will be launched as Space Shuttle attached
payloads with the capability of being released for free flight. They
would not be recovered, allowing useful lifetimes of six months to
one year. An expendable launch vehicle option will be added later. The
spacecraft is 3-axis stabilized with a cylindrical instrument cavity 100
cm long and 36 cm in diameter. If approved, the program would provide
multiple launch opportunities during the upcoming solar maximum. A
conceptual instrument design for a solar pointed mission on Spartan
Lite is shown and discussed. The Extreme-Ultraviolet Normal Incidence
Spectrograph will observe the solar spectrum between 290 and 466 A
with high spatial and spectral resolutions. The large bandpass is due
to the compact design, fitting two optical systems into the instrument
cavity, each observing a different, but overlapping, wavelength range.

---------------------------------------------------------
Title: Solar Terrestrial Relations Observatory (STEREO)
Authors: Davila, Joseph M.; Rust, David M.; Pizzo, Victor J.; Liewer,
Paulett C.
1996SPIE.2804...34D Altcode:
The solar output changes on a variety of timescales, from minutes,
to years, to tens of years and even to hundreds of years. The
dominant timescale of variation is, of course, the 11-year solar
cycle. Observational evidence shows that the physics of solar output
variation is strongly tied to changes in the magnetic field, and perhaps
the most dramatic manifestation of a constantly changing magnetic
field is the Coronal Mass Ejection (CME). On August 5 - 6, 1996 the
Second Workshop to discuss missions to observe these phenomena from
new vantage points, organized by the authors, was held in Boulder,
Colorado at the NOAA Space Environmental Center. The workshop was
attended by approximately 20 scientists representing 13 institutions
from the United States and Europe. The purpose of the Workshop was
to discuss the different concepts for multi- spacecraft observation
of the Sun which have been proposed, to develop a list of scientific
objectives, and to arrive at a consensus description of a mission to
observe the Sun from new vantage points. The fundamental goal of STEREO
is to discover how coronal mass ejections start at the Sun and propagate
in interplanetary space. The workshop started with the propositions
that coronal mass ejections are fundamental manifestations of rapid
large-scale change in the global magnetic structure of the Sun, that
CME's are a major driver of coronal evolution, and that they may play
a major role in the solar dynamo. Workshop participants developed a
mission concept that will lead to a comprehensive characterization of
CME disturbances through build-up, initiation, launch, and propagation
to Earth. It will also build a clear picture of long-term evolution
of the corona. Participants in the workshop recommended that STEREO
be a joint mission with the European scientific community and that
it consist of four spacecraft: `East' at 1 AU near L4, 60 deg from
EArth to detect active regions 5 days before they can be seen by
terrestrial telescopes. `West' at L5 views the sources of energetic
particle events reaching Earth. `Earth Orbiter' to view the Sun, solar
plasma and Earth's magnetosphere, and `North-South' in a 1 AU orbit
tilted 30 deg from the ecliptic plane to provide measurements of polar
fields and high-latitude activity. All spacecraft will carry solar
activity imagers (e.g., EUV telescope and white-light coronagraph)
and radio burst detectors to support a tomography program. All will
carry sensitive polarimeters that will image CME's from 40 solar radii
to 1 AU, and all will carry instruments for situ plasma and energetic
particle sampling. East and North-South have solar vector magnetographs.

---------------------------------------------------------
Title: Coronal Temperature, Density and Nonthermal Velocity Derived
from SERTS EUV Spectra
Authors: Moon, Yong-Jae; Yun, Hong Sik; Davila, J. M.; Park, Young Deuk
1996JKAS...29..207M Altcode:
To derive coronal temperature, electron density and nonthermal velocity,
we have analyzed high resolution spectra (e.g., Fe XII 338.3, Fe XII
352.1, Fe XIV 334.2, Fe XIV 353.8, Fe XV 284.2, Fe XV 321.8, Fe XV
327.0, Fe XVI 335.4, and Fe XVI 360.8) taken from AR 6615 by SERTS
(Solar Extreme Ultraviolet Rocket Telescope and Spectrograph). Important
findings emerging from the present study are as follows: (1) Temperature
estimated from Fe XVI 335.4 and Fe XIV 334.2 is about 2.4 times 10E6
K and no systematic difference in temperature is found between the
active region and its adjacent quiet region; (2) Mean electron density
estimated from Fe XV is about 3*10E9/cm3 and about 10E10/cm3 from Fe
XII and Fe XIV; (3) Mean density of the active region is found to be
higher than that of the quiet region by a factor of 2; (4) Nonthermal
velocity estimated from Fe XV and Fe XVI is 20-25 km/s which decreases
with increasing ionization temperatures. This supports the notion that
the nonthermal velocity declines outwards above the transition region.

---------------------------------------------------------
Title: Measuring Active and Quiet-Sun Coronal Plasma Properties with
Extreme-Ultraviolet Spectra from SERTS
Authors: Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.;
Monsignori-Fossi, Brunella C.
1996ApJS..106..143B Altcode:
We obtained high-resolution extreme-ultraviolet (EUV) spectra of solar
active regions, quiet-Sun areas, and off-limb areas during 1991 May
7 and 1993 August 17 flights of NASA/Goddard Space Flight Center's
Solar EUV Rocket Telescope and Spectrograph (SERTS). The 1991 flight
was the first time a multilayer coated diffraction grating was ever
used in space. Emission lines from the eight ionization stages of iron
between Fe+9 (Fe x) and Fe+16 (Fe XVII) were
observed. Values of numerous density- and temperature-insensitive line
intensity ratios agree with their corresponding theoretical values. Intensity ratios among various lines originating in a common stage of
ionization provide measurements of coronal electron density. Numerous
density-sensitive ratios are available for Fe xiii, and they yield
active region density (cm-3) logarithms of 9.66±0.49
and 9.60±0.54 for the 1993 and 1991 flights, respectively, and a
quiet-Sun density of 9.03±0.28 for the 1993 flight. Filling factors,
calculated from the derived densities assuming a path length of 1 ×
109 cm, range from several thousandths to nearly unity. Intensity ratios among lines originating in different ionization
stages of iron yield measurements of coronal electron temperature in the
isothermal approximation. The line ratios yield temperatures ranging
from 1.1 × 106 to 5.2 × 106 K for the active regions,
and 1.0 × 106 to 2.1 × 106 K for the quiet Sun, depending
upon the ionization stages used. The derived temperature diminishes
with decreasing ionization stages. Fe XVII emission, detected in the
active regions but not in the quiet areas, accounts for the higher
maximum active region temperature. Derived active region temperatures
are greater than their quiet-Sun counterparts for ratios that include
lines from Fe xiv through Fe XVI; however, the derived active region and
quiet-Sun temperatures are not statistically significantly different for
line intensity ratios that involve only Fe x through Fe xiii. The latter
similarity in derived temperatures suggests the presence of similar
thermal structures in all the areas observed, although the active
regions also harbor hotter material. Differential emission measure
(DEM) distributions were constructed for the active region and quiet-
Sun observations obtained during both flights. The two quiet-Sun DEM
curves and the 1993 active region DEM curve all show peaks between log
T = 6.1 and 6.2. The 1993 active region DEM has a second peak between
log T = 6.6 and 6.7, and the 1991 active region DEM has only one peak,
between log T = 6.5 and 6.6. Thus, the 1993 active region DEM curve
appears, in some sense, to be a composite of the quiet-Sun DEM curve
and the 1991 active region DEM curve. The 1991 active region exhibited
flaring activity, yielded higher line ratio temperatures, and contained
greater photo spheric magnetic fields than the 1993 active region.

---------------------------------------------------------
Title: Heating of coronal holes by the resonant absorption and
dissipation of Alfvén waves
Authors: Ofman, L.; Davila, J. M.
1996AIPC..382..149O Altcode:
Coronal hole regions are well known sources of high-speed solar
wind, however to account for the observed properties of the solar
wind a source of energy must be included in addition to heat
conduction. Alfvén waves were suggested as the possible source
of heating that accelerates the solar wind. We investigate the
heating and propagation of Alfvén waves in coronal holes via 2-D
MHD simulation in slab geometry. Resonance heating layers are found
to occur when shear Alfvén waves are driven at the coronal boundary
and a continuous density profile is assumed for the coronal hole. The
heating is enhanced by phase mixing when coronal hole inhomogeneities
(i.e., plumes) are included. We investigate the dependence of the
heating rate on the driver frequency and the Lundquist number S and
find a good agreement with the analytical S1/3 scaling
of the dissipation length for uniform background magnetic field. We
find that when S=104 the low frequency Alfvén waves
can be a significant source of heating of coronal holes at several
solar radii. At larger values of S nonlinear effects may reduce the
effective dissipation length. We also find that the radial dependence
of the heating rate has the same form as the observed scale height
temperature radial profiles observed by SPARTAN 201-01.

---------------------------------------------------------
Title: Long-period oscillations of the sun's interior
Authors: Davila, Joseph M.; Chitre, S. M.
1996BASI...24..309D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Structure and Properties of Solar Active Regions and
Quiet Sun Areas Observed With SERTS and YOHKOH
Authors: Brosius, J. W.; Davila, J. M.; Thomas, R. J.; Hara, H.
1996AAS...188.3715B Altcode: 1996BAAS...28..880B
We observed solar active regions, quiet sun areas, and a coronal hole
simultaneously with Goddard Space Flight Center's Solar EUV Rocket
Telescope and Spectrograph (SERTS), and with the Yohkoh Soft X-Ray
Telescope (SXT) on 1993 August 17. SERTS provided spatially resolved
active region and quiet sun spectra in the 280 to 420 Angstroms
wavelength range, and images in the lines of He II 304 Angstroms,
Mg IX 368 Angstroms, Fe XV 284 Angstroms, and Fe XVI 335 Angstroms
and 360 Angstroms. The SERTS waveband is accessible to CDS, SUMER,
and EIT on SOHO. SXT provided images through multiple broadband
filters. The SERTS images in Fe XV (T=2 MK) and XVI (T=2.5 MK) exhibit
remarkable morphological similarity to the SXT images. Whereas the
Fe XV and XVI images outline the loop structures seen with SXT, the
cooler He II (T=0.1 MK) and Mg IX (T=1 MK) images seem to outline loop
footpoints. From the spatially resolved spectra, we obtained emission
line profiles for lines of Fe X (1 MK) through Fe XVI, and Mg IX and
Ni XVIII (3.2 MK) for each spatial position. Based upon the spatial
variations of the line intensities, the active region systematically
narrows as it is viewed with successively hotter lines. The active
region appears narrowest in the X-ray emission, which is consistent
with our understanding that Yohkoh is most sensitive to the hottest
plasma in its line of sight. EUV emission from Fe XVII (T=5 MK) is weak
but detectable in the active region core. The most intense, central
core straddles the magnetic neutral line. Temperature maps obtained
with SERTS image ratios and with SXT filter ratios are compared. Line
intensity ratios indicate that the active region temperature is greatest
in the central core, but that the density varies very little across the
region. Significant Doppler shifts are not detected in the EUV lines.

---------------------------------------------------------
Title: Acceleration of the Solar Wind by Solitary Waves in Coronal
Holes
Authors: Ofman, L.; Davila, J. M.
1996AAS...188.8602O Altcode: 1996BAAS...28..963O
Coronal holes are well known sources of the high speed solar wind,
however, the exact acceleration mechanism of the wind is still
unknown. We solve numerically the time-dependent, nonlinear, resistive
2(1)/(2)-D MHD equations and find that solitons are generated in
coronal holes nonlinearly by torsional Alfven waves. Initially,
the ponderomotive force due to Alfven waves excites longitudinal
magnetosonic waves by coupling to the radial component of the momentum
equation. Next, these waves steepen into solitons that accelerate
the solar wind to supersonic speed in the radial direction even in
a low-beta plasma. The solitary wave phase velocity was found to be
slightly above the sound speed in the coronal hole; for example, with
the driving Alfven wave amplitude v_d~40 km s(-1) , and plasma beta =5%
the soliton phase speed ~ 200 km s(-1) . We investigate the parametric
dependence of the soliton wavelength and frequency on the plasma beta ,
and on the driving Alfven wave amplitude and frequency. More simplified
analytical model of the coronal hole leads to the Benjamin-Ono equation
that predicts the generation of solitons analytically. The compressive
dissipation of solitary waves may contribute significantly to coronal
hole heating. In addition, Ohmic heating takes place near the coronal
hole boundaries due to phase-mixing of the torsional Alfven waves in
the inhomogeneous regions. When solitary waves are present the solar
wind fluctuates considerably on long time scales and on small spatial
scales in addition to the Alfvenic fluctuations. This is in better
qualitative agreement with observations than the thermally driven and
WKB Alfven wave solar wind models.

---------------------------------------------------------
Title: Signatures of Global Mode Alfven Resonance Heating in
Coronal Loops
Authors: Ofman, L.; Davila, J. M.; Shimizu, T.
1996ApJ...459L..39O Altcode:
The Yohkoh Soft X-Ray Telescope (SXT) observations of active region
coronal loops transient brightening is analyzed, and the scaling of
the thermal energy release with loop lengths is found to be Eth ~
L1.60+/-0.09. The numerically determined scaling of the global
mode heating rate for the resonant absorption of Alfven waves,
H ~ L, is found to agree with the heating rate deduced from the
observed thermal energy scaling, provided that the magnetic field
scales as B ~ L-0.70+/-0.05 and the waves are driven with a omega -1
spectrum. Previous analytical and numerical studies have shown that the
heating due to resonant absorption of Alfven waves is most efficient at
the global mode frequency. In agreement with these studies, we suggest
that coronal loop transient X-ray brightenings occur when a given
length coronal loop is perturbed at its global mode frequency by random
footpoint motions, which results in more efficient heating of the loop.

---------------------------------------------------------
Title: X-Ray Pulsar Two-Line Spectra from a Two-Component Accretion
Column
Authors: Alexander, S. G.; Davila, J.; Dimattio, D. J.
1996ApJ...459..666A Altcode:
Several X-ray pulsars exhibit line structure in their spectra that
has been interpreted as originating from cyclotron processes in the
accreting plasma. A few of these objects also show evidence of a second
spectral feature that, traditionally, has been thought to be the second
cyclotron harmonic. Detailed calculations of the emitted flux spectra
are presented that incorporate a simple two-component model of the
accretion cap. The two components are modeled as slabs separated by a
shock wave, where the postshock slab is the thermalized high-density
and -temperature plasma that creates the radiation via bremsstrahlung
processes and the preshock material is represented by a relatively cool,
low-density plasma that is moving near the free-fall velocity. Results
show that two spectral features are easily produced, one representing
the fundamental cyclotron harmonic of the postshock plasma, and another
that is a Doppler-shifted line produced by scattering in the preshock
plasma.

---------------------------------------------------------
Title: Measurements of Active and Quiet Sun Coronal Plasma Properties
with SERTS EUV Spectra
Authors: Brosius, J. W.; Davila, J. M.; Thomas, R. J.;
Monsignori-Fossi, B. C.; Saba, J. L. R.
1996mpsa.conf..421B Altcode: 1996IAUCo.153..421B
No abstract at ADS

---------------------------------------------------------
Title: Solar EUV spectroscopy with serts: measurements of active
and quiet Sun properties.
Authors: Brosius, J. W.; Davila, J. M.; Thomas, R. J.; Jordan, S. D.;
Monsignori-Fossi, B. C.
1996uxsa.conf...83B Altcode: 1996uxsa.coll...83B
The Solar EUV Rocket Telescope and Spectrograph (SERTS) was developed
by the Laboratory for Astronomy and Solar Physics at NASA/Goddard
Space Flight Center. It was successfully flown in 1989, 1991, 1993, and
(very recently) 1995, providing spectra and images of a variety of solar
features on each occasion. SERTS data have been used to address numerous
problems in solar physics, of which the following are discussed below:
(1) measurement of coronal temperature and density, (2) derivation
of differential emission measure distribution, (3) verification of
atomic physics parameters, (4) determination of relative elemental
abundances, (5) formation of the He II 304 Å line, (6) mass flows,
and (7) coronal magnetography.

---------------------------------------------------------
Title: Nonlinear Excitation of Global Modes and Heating in Randomly
Driven Coronal Loops
Authors: Ofman, L.; Davila, J. M.
1996ApJ...456L.123O Altcode:
We solve the nonlinear three-dimensional MHD equations for fully
compressible, low- beta , resistive plasma to model resonant Alfven
wave heating of a coronal loop. Alfven waves are driven in the loop by
a (pseudo)random time-dependent forcing with a bounded amplitude. We
find that global modes are excited and resonantly heat the loop in
the nonlinear regime in three dimensions. Resonant heating occurs in
several narrow layers accompanied by high velocity and magnetic field
shear. The narrow dissipation layers are affected by the self-consistent
velocity shear and are carried around by the flow. Consequently, the
topology of the perpendicular magnetic field and the ohmic heating
regions differs significantly from the linear or single-frequency
driver regimes, and the heating is spread more uniformly inside the
loop. The heating rate varies significantly on a timescale of one to
several global mode periods. We conclude that, in solar active regions,
random field-line motions can excite global mode oscillations and
resonantly heat the loops with a time-varying heating rate.

---------------------------------------------------------
Title: Alfvén wave heating of coronal holes and the relation to
the high-speed solar wind
Authors: Ofman, L.; Davila, J. M.
1995JGR...10023413O Altcode:
Coronal hole regions are well-known sources of high-speed solar
wind; however, to account for the observed properties of the solar
wind, a source of energy must be included in addition to heat
conduction. Alfvén waves were suggested as the possible source of
heating that accelerates the solar wind. We investigate the heating
and propagation of the fast and shear Alfvén waves in coronal holes
via numerical solution of the time-dependent, linearized, resistive,
low-β, two-dimensional MHD equations in slab geometry. The waves are
driven at the lower boundary of the coronal hole and propagate into the
corona. We find that fast waves are partially reflected at the coronal
hole boundary and significant part of the wave energy leaks out of the
coronal hole. We compare the calculated wavelengths and the attenuation
rate of the fast waves in the leaky waveguide formed by the coronal
hole with the analytical ideal MHD solutions for ky=0, where
ky is the perpendicular wavenumber, and find an excellent
agreement. When ky≠0 the fast waves couple to the shear
Alfvén waves and transfer energy across field lines. Resonance
heating layers are found to occur when shear Alfvén waves are driven
and a continuous density profile is assumed for the coronal hole. When
resonance absorption is considered, the leakage is small compared to
the heating rate. The heating is enhanced by phase mixing when coronal
hole inhomogeneities (i.e., plumes) are included. We investigate the
dependence of the heating rate on the driver frequency and the Lundquist
number S and find a good agreement with the analytical S1/3
scaling of the dissipation length. We find that when S=104
the low-frequency Alfvén waves can be a significant source of heating
of coronal holes at several solar radii. At larger values of S,
nonlinear effects might reduce the effective dissipation length. We
discuss the relation of our results to the observed properties of
high-speed solar wind and coronal holes.

---------------------------------------------------------
Title: Nonlinear resonant absorption of Alfvén waves in three
dimensions, scaling laws, and coronal heating
Authors: Ofman, L.; Davila, J. M.
1995JGR...10023427O Altcode:
The nonlinear evolution of the resonant absorption of standing and
propagating Alfvén waves in an inhomogeneous plasma is studied via
solution of the time-dependent, three-dimensional, low-β, resistive
MHD equations over a wide parameter range. When the nonlinear effects
become important, the velocities at the dissipation layer were found to
be lower than the linear scaling of S1/3 would predict, where
S is the Lundquist number. Highly sheared velocities that are subject
to the Kelvin-Helmholtz-like instability were found at the narrow
dissipation layers. Three-dimensional Kelvin-Helmholtz-like vortices
appear at and near the dissipation layers and propagate along the slab
of plasma when traveling Alfvén wave solution are considered. The
narrow resonant heating layers are deformed by the self-consistent
shear flow. In the solar active regions where the resonant absorption
of Alfvén waves is believed to occur, the instability may lead to
turbulent enhancement of the dissipation parameters and account for the
observed turbulent velocities inferred from the nonthermal broadening
of x-ray and EUV emission lines. The self consistent J×B force changes
significantly the density structure of the loop that leads to a shift
in the global mode frequency response of the loop and a subsequent
drop in the heating rate. In the solar corona the density evolution
of the loop is likely to be dominated by evaporation of material from
the transition region.

---------------------------------------------------------
Title: Performance comparison of two Wolter type II telescopes in
the far ultraviolet
Authors: Leviton, Douglas B.; Wright, Geraldine A.; Thomas, Roger J.;
Davila, Joseph M.; Epstein, Gabriel L.
1995ApOpt..34.6459L Altcode:
Experimental results for image quality and scatter in far-UV
light are used to choose between the conventionally polished Solar
Extreme-Ultraviolet Rocket Telescope and Spectrograph (SERTS-A)
and computer-controlled polished SERTS-C Wolter type II solar rocket
telescopes for an extreme-UV flight instrument. In 124-nm light the
SERTS-C telescope image had a 0.67-arcsec full width at half-maximum
(FWHM), compared with a 1.25-arcsec FWHM for the SERTS-A telescope. In
addition SERTS-C had twice the peak irradiance of SERTS-A and an order
of magnitude lower near-angle scatter. The inflight performance of
the telescopes is consistent with laboratory findings.

---------------------------------------------------------
Title: Reply to “Comment on nonlinear studies of coronal heating
by the resonant absorption of Alfvén waves” by J. V. Hollweg
Authors: Ofman, L.; Davila, J. M.; Steinolfson, R. S.
1995GeoRL..22.2679O Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Heating of coronal holes by the resonant absorption
and dissipation of Alfven waves and its relation to solar wind
acceleration
Authors: Ofman, L.; Davila, J. M.
1995sowi.confQ..66O Altcode:
Coronal hole regions are well known sources of high-speed solar wind,
however to account for the observed properties of the solar wind
a source of momentum and heat must be included. Alfven waves were
suggested as the possible source of heating that accelerates the solar
wind. We investigate the propagation of the Alfven waves in coronal
holes via numerical solution of the linearized 2-D resistive MHD
equations in slab geometry. The Alfven waves are driven at the lower
boundary of the coronal hole and propagate into the corona. The waves
are reflected at the coronal hole boundary and part of the wave energy
leaks out of the coronal hole. We compare the calculated wavelengths
and the attenuation rate of the fast mode Alfven waves in the leaky
waveguide formed by the coronal hole with the analytical ideal MHD
solutions. The formation of resonance heating layers is found to occur
when shear Alfven waves propagate in an inhomogeneous coronal hole. The
heating is enhanced when fast mode waves couple to the shear Alfven
waves. The narrow heating layers are formed near the location of the
ideal resonance, which might occur near the coronal hole boundary for
a nearly constant density coronal hole, surrounded by a higher density
plasma. We investigate the dependence of the heating on the driver
frequency, the Lundquist number, and on the heliocentric distance. and
find that the low frequency Alfven waves can be an efficient source
of heating at large distances from the Sun. We discuss the relation
of our results to the observed properties of high-speed solar wind
and coronal holes.

---------------------------------------------------------
Title: Coronal Heating by the Resonant Absorption of Alfven Waves:
Wavenumber Scaling Laws
Authors: Ofman, L.; Davila, J. M.; Steinolfson, R. S.
1995ApJ...444..471O Altcode:
The importance of global modes in coronal loop heating is well
established. In the present work the scaling of the global-mode resonant
heating rate with the perturbation wavenumbers is studied with the
numerical solution of the linearized time-dependent MHD equations for
a full compressible, low-beta, resistive plasma using an implicit
integration scheme. The numerical simulations demonstrate that the
dissipation on inhomogeneities in the background Alfven speed occurs in
narrow resonant layer with the highest heating rate at the global-mode
frequency. The global-mode heating rate H r was found to
scale as H (Sub r) approximately k y 1.03 when k
z = 0.1, and as H r approximately k y
-1.93 when k z = 0.75, where k y and
k z are the wavenumbers in the perpendicular and parallel to
the magnetic field directions, respectively, while the dependence of H
r on k z is more complex. The quality factor Q
of the MHD resonance cavity scales as Q approximately k y
-1.8 for k z = 0.75 and as Q approximately k
y -1.46 for k z = 0.1. The numerically
determined heating rate scaling, the global-mode fequency, and the
quality factor are in good agreement with the analytical linear
theory. The magnitude of the perturbed velocities was found to
decrease with k y. Assuming typical coronal loop parameters
(B 0 = 100-200 G, upsilon A = 2000-4000 km/s),
the Alfven waves can supply the required heating to a low-Q loops.

---------------------------------------------------------
Title: Heating of Coronal Holes by the Resonant Absorption and
Dissipation of Alfvén Waves
Authors: Ofman, L.; Davila, J. M.
1995SPD....26..907O Altcode: 1995BAAS...27..974O
No abstract at ADS

---------------------------------------------------------
Title: Measurements of Active and Quiet Sun Coronal Plasma Properties
with SERTS EUV Spectra
Authors: Brosius, J. W.; Davila, J. M.; Thomas, R. J.;
Monsignori-Fossi, B. C.
1995SPD....26..607B Altcode: 1995BAAS...27..962B
No abstract at ADS

---------------------------------------------------------
Title: Are Spicules Evidence for Small-scale Motions that Redistribute
HE II Ions to Produce Enhanced 304A Line Emission?
Authors: Jordan, S. D.; Davila, J. M.; Thomas, R. J.; Garcia, A.
1995SPD....26..508J Altcode: 1995BAAS...27..958J
No abstract at ADS

---------------------------------------------------------
Title: Nonlinear studies of coronal heating by the resonant absorption
of Alfvén waves
Authors: Ofman, L.; Davila, J. M.; Steinolfson, R. S.
1994GeoRL..21.2259O Altcode:
The first nonlinear study of the instability of the resonant
absorption is presented in this paper. The nonlinear evolution of the
resonant absorption of Alfvén waves in an inhomogeneous plasma is
studied via solution of the time-dependent 3-D, low-β, resistive
MHD equations. Highly sheared velocities that are subject to the
Kelvin-Helmholtz like instability are found at the narrow dissipation
layers. Three dimensional Kelvin-Helmholtz like vortices appear at and
near the dissipation layers and propagate along the slab of plasma. The
narrow resonant heating layers are deformed by the self-consistent
shear flow. In the solar active regions where the resonant absorption of
Alfvén waves is believed to occur the instability may lead to turbulent
enhancement of the dissipation parameters and account for the observed
turbulent velocities inferred from the non-thermal broadening of x-ray
and EUV emission lines.

---------------------------------------------------------
Title: Solar Coronal Temperature Diagnostics Using Emission Lines
from Multiple Stages of Ionization of Iron
Authors: Brosius, Jeffrey W.; Davila, Joseph M.; Thomas, Roger J.;
Thompson, William T.
1994ApJ...425..343B Altcode:
We obtained spatially resolved extreme-ultraviolet (EUV) spectra
of AR 6615 on 1991 May 7 with NASA/ Goddard Space Flight Center's
Solar EUV Rocket Telescope and Spectrograph (SERTS). Included are
emission lines from four different stages of ionization of iron:
Fe(+15) lambda 335 A, Fe(+14) lambda 327 A, Fe(+13) lambda 334 A,
and Fe(+12) lambda 348 A. Using intensity ratios from among these
lines, we have calculated the active region coronal temperature along
the Solar Extreme Ultraviolet Telescope and Spectrograph (SERTS)
slit. Temperatures derived from line ratios which incorporate adjacent
stages of ionization are most sensitive to measurement uncertainties
and yield the largest scatter. Temperatures derived from line ratios
which incorporate nonadjacent stages of ionization are less sensitive to
measurement uncertainties and yield little scatter. The active region
temperature derived from these latter ratios has an average value of
2.54 x 106 K, with a standard deviation approximately 0.12
x 106 K, and shows no significant variation with position
along the slit.

---------------------------------------------------------
Title: Solar Tomography
Authors: Davila, Joseph M.
1994ApJ...423..871D Altcode:
Tomographic imaging has provided the medical profession with
unprecedented three-dimensional views of the internal structure
of the human body. Similar techniques can provide solar physicists
with an equally spectacular view of the three-dimensional structure
of the solar corona, providing a new tool for addressing the
problems of coronal structure, energy balance, and evolution. For
the reconstruction process, images of the solar corona observed
from different angular positions within the ecliptic are needed,
and these are not yet available. The purpose is to demonstrate the
utility and the practicality of solar tomography with a series of
computer simulations of the process, while exploring the sensitivity
of the results to some of the parameters of the observing process,
e.g., the number of observations, angular spacing, and signal to
noise. The results show that tomography can be a powerful technique
for determining the three-dimensional nature of active region magnetic
fields, coronal loops, helmet streamers, coronal holes, and other
structures in the corona.

---------------------------------------------------------
Title: Coronal Heating by the Resonant Absorption of Alfven Waves
Authors: Ofman, L.; Davila, J. M.; Steinolfson, R. S.
1994scs..conf..473O Altcode: 1994IAUCo.144..473O
Nonlinear evolution and stability of the resonant absorption layer
is considered by solving the time-dependent 3D, low-β, resistive MHD
equations with the Lax-Wendroff explicit method. The narrow resonant
heating layers are deformed by the self-consistent shear flow. When
the driver amplitude is small compared to the average Alfvén speed the
dissipation layer appears to be stable and the driver-period-averaged
ohmic heating rate saturates at a slightly higher than the linear
rate. When the driver amplitude is large (Fd ≍ 1) the
resonant heating may become unstable.

---------------------------------------------------------
Title: Coronal Heating by the Resonant Absorption of Alfven Waves:
The Effect of Viscous Stress Tensor
Authors: Ofman, L.; Davila, J. M.; Steinolfson, R. S.
1994ApJ...421..360O Altcode:
The time-dependent linearized magnetohydrodynamics (MHD) equations
for a fully compressible, low-beta, viscoresistive plasma are
solved numerically using an implicit integration scheme. The full
viscosity stress tensor (Braginskii 1965) is included with the five
parameters etai i = 0 to 4. In agreement with previous
studies, the numerical simulations demonstrate that the dissipation
on inhomogeneities in the background Alfven speed occurs in a
narrow resonant layer. For an active region in the solar corona
the values of etai are etao = 0.65 g/cm/s,
eta1 = 3.7 x 10-12 g/cm/s, eta2 =
4 eta1, eta3 = 1.4 x 10-6 g/cm/s,
eta4 = 2 eta3, with n = 1010/cu
cm, T = 2 x 106 K, and B = 100 G. When the Lundquist
number S = 104 and R1 much greater than S
(where R1 is the dimensionless shear viscous number)
the width of the resistive dissipation layer dr is 0.22a
(where a is the density gradient length scale) and dr
approximately S-1/3. When S much greater than R1
the shear viscous dissipation layer width dr scales as
R1-1/3. The shear viscous and the resistive
dissipation occurs in an overlapping narrow region, and the total
heating rate is independent of the value of the dissipation parameters
in agreement with previous studies. Consequently, the maximum values
of the perpendicular velocity and perpendicular magnetic field scale
as R1-1/3. It is evident from the simulations
that for solar parameters the heating due to the compressive viscosity
(R0 = 560) is negligible compared to the resistive and the
shear viscous (R1) dissipation and it occurs in a broad layer
of order a in width. In the solar corona with S approximately equals
104 and R1 approximately equals 1014
(as calculated from the Braginskii expressions), the shear viscous
resonant heating is of comparable magnitude to the resistive resonant
heating.

---------------------------------------------------------
Title: The Effects of Kelvin-Helmholtz Instability on Resonance
Absorption Layers in Coronal Loops
Authors: Karpen, Judith T.; Dahlburg, Russell B.; Davila, Joseph M.
1994ApJ...421..372K Altcode:
One of the long-standing uncertainties in the wave-resonance theory
of coronal heating is the stability of the resonance layer. The wave
motions in the resonance layer produce highly localized shear flows
which vary sinusoidally in time with the resonance period. This
configuration is potentially susceptible to the Kelvin-Helmholtz
instability (KHI), which can enhance small-scale structure and turbulent
broadening of shear layers on relatively rapid ideal timescales. We
have investigated numerically the response of a characteristic velocity
profile, derived from resonance absorption models, to finite fluid
perturbations comparable to photospheric fluctuations. We find that
the KHI primarily should affect long (approximately greater than 6 x
104 km) loops where higher velocity flows (M approximately
greater than 0.2) exist in resonance layers of order 100 km wide. There,
the Kelvin-Helmholtz growth time is comparable to or less than the
resonance quarter-period, and the potentially stabilizing magnetic
effects are not felt until the instability is well past the linear
growth stage. Not only is the resonance layer broadened by the KHI,
but also the convective energy transport out of the resonance layer
is increased, thus adding to the efficiency of the wave-resonance
heating process. In shorter loops, e.g., those in bright points and
compact flares, the stabilization due to the magnetic field and the
high resonance frequency inhibit the growth of the Kelvin-Helmholtz
instability beyond a minimal level.

---------------------------------------------------------
Title: Potential IR Observations of the Solar Corona
Authors: Kumar, C. K.; Davila, J.
1994IAUS..154...81K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar Tomography
Authors: Davila, J. M.
1993AAS...183.5907D Altcode: 1993BAAS...25.1387D
Images obtained by observing the solar corona from a single
spacecraft typically measure the line-of-sight integral of the
volumetric emissivity through the source. The resulting two-dimensional
observations have an unavoidable ambiguity along the line of sight that
can be removed only by making assumptions about the three dimensional
nature of the emission. These ambiguities can be removed by observing
the Sun from different vantage points, at the same time, i.e. solar
tomography. The basic concept of tomographic is fairly simple. For an
optically thin emission source, like the solar corona, each pixel in
an image represents the line of sight integration of the volumetric
emissivity of the plasma at the wavelength of observation. By obtaining
several of these observations, from various angles, the underlying three
dimensional structure of the emission can be deduced. This principle
has been used extensively in the Medical community for the imaging of
internal structure of the body with such techniques as Computer Aided
Tomography (CAT) scanners and Magnetic Resonance Imaging (MRI). The
purpose of this paper is to take an intial look at the following two
questions: (1) Is tomography feasible with a few spacecraft?; and (2)
What scientific objectives can be addressed?

---------------------------------------------------------
Title: A High-Resolution Solar Spectrum in the EUVE Bandpass
Authors: Thomas, Roger J.; Davila, Joseph M.
1993AAS...183.0804T Altcode: 1993BAAS...25.1301T
The Solar EUV Rocket Telescope and Spectrograph (SERTS) obtains imaged
spectra of solar features with resolution around 0.04 Angstroms
and high sensitivity. Its spectral range of 170 -- 450 Angstroms
overlaps large portions of the Medium Wavelength and Long Wavelength
Spectrographs on EUVE, and so may provide help in interpreting the
lower resolution EUVE spectra of late-type stellar sources. As an
example, we compare SERTS observations averaged over a typical solar
active region with EUVE calibration spectra of Capella, a G6 + G2
binary. The Capella spectra include prominent spectral features at
256.5, 284.7, 304.2, 335.4, and 360.3 Angstroms. The SERTS spectrum
indicates that, although these features are generally dominated by a
single emission line, they may also be contaminated to some degree by
blends of other lines at the resolutions of the EUVE spectrographs,
which are approximately 1.0 and 2.0 Angstroms. This high-resolution
solar active region spectrum from SERTS is now available electronically
by request to thomas@jet.gsfc.nasa.gov, as are emission line catalogs
derived from it. This work was supported under NASA RTOP 170-38-52.

---------------------------------------------------------
Title: Nonlinear Evolution of Coronal Heating by the Resonant
Absorption of Alfven Waves
Authors: Ofman, L.; Davila, J. M.; Steinolfson, R. S.
1993AAS...183.5904O Altcode: 1993BAAS...25.1386O
The nonlinear 3-D MHD equations for a fully compressible, low-beta,
visco-resistive plasma are solved numerically using the Lax-Wendroff
integration scheme (the explicit integration scheme was found to
converge considerably faster in terms of physical time per CPU time
than the Alternating Direction Implicit method). The calculations
are initiated with the solutions of the linearized version of the MHD
equations (Ofman, Davila, and Steinolfson 1994, Ap.J., in press), with
inhomogeneous background density, and a constant magnetic field. The
numerical simulations demonstrate that the narrow dissipation layer
is affected by the self-consistent velocity shear: i.e., the regions
of high ohmic heating are carried around by the flow. Consequently,
the topology of the perpendicular magnetic field and the ohmic heating
regions differs significantly from the linear case. Additional harmonics
of the driver frequency appear in the temporal oscillations with the
dominant frequency of double the driver frequency. When the Lundquist
number is S=10(3) the average width of the resistive dissipation layer
is 0.4a (where a is the density gradient length scale) and consistent
with the linear results. When the driver amplitude is small compared
to the average Alfven speed the dissipation layer appears to be
stable and the ohmic heating rate is enhanced by about 15% over the
linear heating rate. When the driver amplitude is comparable to the
average Alfven speed the nonlinear effects dominate the evolution and
the resonant heating layer may become unstable. A parametric study
of the instability is presented. The effect of the self-consistent
velocity on the instability is considered by generalizing the linear
theory (Davila 1987) to include shear flow and solving the linearized
dispersion relation of the resonant absorption with the background
shear flow. (*) NRC-NAS Resident Research Associate.

---------------------------------------------------------
Title: Heating Constraints on the Solar Corona Determined from
SERTS Observations
Authors: Falconer, D. A.; Davila, J. M.; Thomas, R. J.; Thompson, W. T.
1993AAS...183.5905F Altcode: 1993BAAS...25.1386F
EUV emission above the quiet solar limb up to 1.2Rsun
was studied using observations made from two different flights of the
Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) covering
three different spatial locations. The spectral line intensities
from a number of EUV spectral lines as a function of height were
analyzed. Ratio of iron line intensities from Fe XIII, Fe XIV, Fe XV
and Fe XVI were used to determine the electron temperature. The emission
measure was determined from the iron line intensities and the electron
temperature. Since in all three cases the line ratio temperature
increased with height, a source of heating is required at some location
above the maximum observed height, which was 1.15Rsun
for two locations and 1.2Rsun for the third location. The
maximum divergence of heat flux was determined from the variation of
temperature versus radius. The total radiatiative power was obtained
from the emission measure and temperature. By comparing the divergence
of heat flux and the total radiatiative power, heating was also shown
to be necessary for two of the three cases throughout the region below
1.15Rsun. (*) ARC

---------------------------------------------------------
Title: Coronal Heating by the Resonant Absorption of Alfven Waves:
Importance of the Global Mode and Scaling Laws
Authors: Steinolfson, Richard S.; Davila, Joseph M.
1993ApJ...415..354S Altcode:
Numerical simulations of the MHD equations for a fully compressible,
low-beta, resistive plasma are used to study the resonance absorption
process for the heating of coronal active region loops. Comparisons with
more approximate analytic models show that the major predictions of the
analytic theories are, to a large extent, confirmed by the numerical
computations. The simulations demonstrate that the dissipation occurs
primarily in a thin resonance layer. Some of the analytically predicted
features verified by the simulations are (a) the position of the
resonance layer within the initial inhomogeneity; (b) the importance of
the global mode for a large range of loop densities; (c) the dependence
of the resonance layer thickness and the steady-state heating rate on
the dissipation coefficient; and (d) the time required for the resonance
layer to form. In contrast with some previous analytic and simulation
results, the time for the loop to reach a steady state is found to be
the phase-mixing time rather than a dissipation time. This disagreement
is shown to result from neglect of the existence of the global mode
in some of the earlier analyses. The resonant absorption process is
also shown to behave similar to a classical driven harmonic oscillator.

---------------------------------------------------------
Title: Simultaneous Observations of Solar Plage with the Solar
Extreme Ultraviolet Rocket Telescope and Spectrograph (SERTS),
the VLA, and the Kitt Peak Magnetograph
Authors: Brosius, Jeffrey W.; Davila, Joseph M.; Thompson, William T.;
Thomas, Roger J.; Holman, Gordon D.; Gopalswamy, N.; White, Stephen
M.; Kundu, Mukul R.; Jones, Harrison P.
1993ApJ...411..410B Altcode:
We obtained simultaneous images of solar plage on 1991, May 7
with SERTS, the VLA,4 and the NASA/National Solar Observatory
spectromagnetograph at the NSO/Kitt Peak Vacuum Telescope. Using
intensity ratios of Fe XVI to Fe XV emission lines, we find that the
coronal plasma temperature is (2.3-2.9) x 10 exp 6 K throughout the
region. The column emission measure ranges from 2.5 x 10 exp 27 to
l.3 x 10 exp 28 cm exp -5. The calculated structure and intensity
of the 20 cm wavelength thermal bremsstrahlung emission from the hot
plasma observed by SERTS is quite similar to the observed structure and
intensity of the 20 cm microwave emission observed by the VLA. Using
the Meyer (1991, 1992) revised coronal iron abundance, we find no
evidence either for cool absorbing plasma or for contributions from
thermal gyroemission. Using the observed microwave polarization and the
SERTS plasma parameters, we calculate a map of the coronal longitudinal
magnetic field. The resulting values, about 30-60 G, are comparable
to extrapolated values of the potential field at heights of 5000 and
10,000 km.

---------------------------------------------------------
Title: Tomography of the Solar Corona
Authors: Davila, J. M.
1993BAAS...25.1191D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Solar Coronal Plasma and Magnetic Field Diagnostics Using
SERTS and Coordinated VLA Observations
Authors: Brosius, J. W.; Davila, J. M.; Thompson, W. T.; Thomas, R. J.;
Holman, G. D.; Gopalswamy, N.; White, S. M.; Kundu, M. R.; Jones, H. P.
1993BAAS...25.1224B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Properties of the Quiet Solar Corona up to 1. 2 Solar Radii
Derived from SERTS Observations
Authors: Falconer, D. A.; Davila, J. M.; Thomas, R. J.
1993BAAS...25.1200F Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flows Observed in the Solar Corona with SERTS
Authors: Davila, J. M.
1993BAAS...25.1210D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coronal Heating by the Resonant Absorption of Alfven Waves:
The Effects of Viscous Stress Tensor
Authors: Ofman, L.; Davila, J. M.; Steinolfson, R. S.
1993BAAS...25.1202O Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analysis of EUV, Microwave and Magnetic Field Observations
of Solar Plage
Authors: Brosius, J. W.; Davila, J. M.; Jones, H. P.; Thompson, W. T.;
Thomas, R. J.; Holman, G. D.; White, S. W.; Gopalswamy, N.; Kundu,
M. R.
1993ASPC...46..291B Altcode: 1993mvfs.conf..291B; 1993IAUCo.141..291B
No abstract at ADS

---------------------------------------------------------
Title: First flight of an extreme-ultraviolet spectrometer with a
multilayer grating.
Authors: Davila, J. M.; Thomas, R. J.; Thompson, W. T.; Keski-Kuha,
R. A. M.; Neupert, W. M.
1993uxrs.conf..301D Altcode: 1993uxsa.conf..301D
The authors report the first space flight of an extreme-ultraviolet
(EUV) spectrograph incorporating a multilayer coated normal incidence
grating in the Solar Extreme-ultraviolet Rocket Telescope and
Spectrograph (SERTS). Pre-flight performance evaluation showed that
the application of a 10-layer Ir/Si multilayer coating to the 3600
l/mm, blazed, toroidal replica grating produced a factor of nine
enhancement in peak efficiency near the design wavelength around
30 nm in first order over the standard gold coating used in earlier
flights. In addition, a spectral resolution of better than 5000 was
maintained. This technology, now proven in space flight, is applicable
to most normal incidence spectrographs used for astronomical observation
in the ultraviolet, far and extreme ultraviolet and soft X-ray regions
of the spectrum.

---------------------------------------------------------
Title: Underneath coronal loops: MSDP observations coordinated with
SERTS 4 and NIXT flights.
Authors: Schmieder, B.; Mein, N.; Golub, L.; Davila, J. M.; Thomas,
R.; Brosius, J.
1992ESASP.348..257S Altcode: 1992cscl.work..257S
Ground-based coordinated observations with the multichannel subtractive
double pass spectrograph (MSDP) allowed to portray the chromospheric
intensity and velocity fields below coronal structures during recent
launchs of sounding rockets. During SERTS 4 observations (May 7,
1991), two different active regions presenting flare and filament have
been coaligned with UV structures. In July 11, 1991 (eclipse day)
large Hα ejection material in AR 6713 was detected during the NIXT
flight. Preliminary results are displayed.

---------------------------------------------------------
Title: Analysis of EUV, Microwave, and Magnetic Field Observations
of a Solar Active Region
Authors: Brosius, J. W.; Davila, J. M.; Jones, H. P.; Thompson, W. T.;
White, S. M.; Gopalswamy, N.; Kundu, M. R.
1992AAS...180.4002B Altcode: 1992BAAS...24R.792B
No abstract at ADS

---------------------------------------------------------
Title: Results of the Fourth Flight of SERTS
Authors: Davila, J. M.; Thomas, R. J.; Thompson, W. T.
1992AAS...180.4001D Altcode: 1992BAAS...24..792D
No abstract at ADS

---------------------------------------------------------
Title: The Coronal Density and Temperature for 1.05
&lt;R⊙ &lt; 1.5 Derived from SERTS Observation
Authors: Falconer, D. A.; Davila, J. M.; Thomas, R. J.
1992AAS...180.4003F Altcode: 1992BAAS...24..792F
No abstract at ADS

---------------------------------------------------------
Title: A Rotating Tomographic Imager for Solar
Extreme-Ultraviolet/Soft X-Ray Emission
Authors: Davila, Joseph M.; Thompson, W. T.
1992ApJ...389L..91D Altcode:
A concept is presented for a high-resolution EUV/soft-X-ray imager
that has much in common with the medical imaging procedure of
tomography. The resulting instrument is compatible with a simpler, less
costly spin-axis-stabilized spacecraft. To demonstrate the fidelity
of the reconstruction procedure, the observation and reconstruction
is simulated to compare the results with the original image.

---------------------------------------------------------
Title: Rocket flight of a multilayer coated high-density EUV toroidal
grating
Authors: Keski-Kuha, Ritva A. M.; Thomas, Roger J.; Davila, Joseph M.
1992SPIE.1546..614K Altcode:
A multilayer coated high density toroidal grating was flown on a
sounding rocket experiment in the Solar EUV Rocket Telescope and
Spectrograph (SERTS) instrument. To our knowledge this is the first
space flight of a multilayer coated grating. Pre-flight performance
evaluation showed that the application of a 10-layer Ir/Si multilayer
coating to the 3600 l/mm blazed toroidal replica grating produced a
factor of 9 enhancement in peak efficiency near the design wavelength
around 30 nm in first order over the standard gold coating, with a
measured EUV efficiency that peaked at 3.3 percent. In addition, the
grating's spectral resolution of better than 5000 was maintained. The
region of enhanced grating efficiency due to the multilayer coating
is clearly evident in the flight data. Within the bandpass of the
multilayer coating, the recorded film densities were roughly equivalent
to those obtained with a factor of six longer exposure on the previous
flight of the SERTS instrument.

---------------------------------------------------------
Title: Magnetoacoustic Heating of the Solar Chromosphere
Authors: Davila, Joseph M.; Chitre, S. M.
1991ApJ...381L..31D Altcode:
Long-period acoustic waves generated in the solar convection zone
can propagate radially outward through the overlying atmosphere
and get resonantly absorbed in the magnetic arches of the low-lying
chromospheric canopy. The resulting Poynting and acoustic flux that
enters the magnetic canopy in the network regions is demonstrated to
be adequate to account for the observed chromospheric emission.

---------------------------------------------------------
Title: Simultaneous EUV, Microwave, and Magnetic Field Observations
of Solar Active Regions
Authors: Brosius, J. W.; Davila, J. M.; Thompson, W. T.; Gopalswamy,
N.; White, S. M.; Jones, H. P.; Metcalf, T. R.
1991BAAS...23.1388B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Recent Observations of the Solar Corona with SERTS, an EUV
Multilayer Spectrograph
Authors: Davila, J. M.; Thomas, R. J.; Thompson, W. T.; Keski-Kuha,
R. A. M.; Neupert, W. M.
1991BAAS...23.1387D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Resonant Absorption of p-Modes by Sunspots with Twisted
Magnetic Fields
Authors: Chitre, S. M.; Davila, Joseph M.
1991ApJ...371..785C Altcode:
A simplified inhomogeneous sunspot model with an axial current (twisted
magnetic field) is considered. The absorption of incoming acoustic
modes in a narrow resonance layer inside the sunspot flux tube is
investigated, and the energy loss is estimated. For nonaxisymmetric
modes the results are consistent with previous calculations. However,
contrary to previous work, it is demonstrated that the existence of
an azimuthal component of the magnetic field can lead to significant
absorption of even the axisymmetric modes. If the absorption rate
calculated in this paper is used in conjunction with the observed
wavelength dependence of the absorption coefficient, it is found that
the sunspot flux tube must have significant twist in the subsurface
layers. Furthermore, the presence of twist in the magnetic field
leads to a natural explanation for the observed dependence on m,
the azimuthal wave mode number, and the magnitude of the absorption
coefficient can be accounted for in a self-consistent way.

---------------------------------------------------------
Title: Solar Tomography: Deducing the Three-dimensional Structure
of the Corona from Stereoscopic Images of Optically Thin Line Emission
Authors: Davila, J. M.
1991BAAS...23.1063D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Magnetoacoustic Heating of the Solar Chromosphere (With
1 Figure)
Authors: Chitre, S. M.; Davila, J. M.
1991mcch.conf..402C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Resonance Absorption Heating (With 5 Figures)
Authors: Davila, J. M.
1991mcch.conf..464D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Sunspot Seismology Theory
Authors: Davila, Joseph M.
1990IAUS..142..149D Altcode:
Physical mechanisms proposed to explain the absorption of significant
p-mode wave power by sunspots are reviewed, and their viability in view
of the current knowledge of the scattering process is discussed. It
is concluded that there is no satisfactory theoretical model for
the absorption of p-modes by sunspots available at present. It is
argued that the resonance absorption model is able to obtain the large
absorption coefficients observed for nonaxisymmetric perturbations. For
axisymmetric perturbations, departures from perfect cylindrical symmetry
or the inclusion of a slight twist in the sunspot flux tube may be able
to resolve the problem with the absorption of m = 0 wave modes. Other
dissipative models, which do not incorporate the background gradient
effects inherent in the resonance absorption mechanism, require
inconveniently large dissipation coefficients within the sunspot.

---------------------------------------------------------
Title: Resonant Absorption of P-Modes by Sunspots
Authors: Chitre, S. M.; Davila, Joseph M.
1990IAUS..142..187C Altcode:
Explanations for the observed p-mode absorption in sunspots are
examined. It is demonstrated that any dissipative process like
radiative, viscous, or resistive dissipation leads to the resonant
absorption of acoustic waves incident on the sunspot tube, and that the
resultant heating rate can be shown to be consistent with the observed
absorption of the p-mode power impinging on an isolated inhomogeneously
structured sunspot.

---------------------------------------------------------
Title: The Scattering of Solar P-Modes by Sunspots
Authors: Davila, J.; Jensen, K.
1989BAAS...21.1110D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Sunspot Seismology
Authors: Chitre, S. M.; Davila, J. M.
1989BAAS...21.1110C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A Theory for the Scattering of Solar P-Modes by Sunspots
Authors: Jensen, K.; Davila, J.
1989BAAS...21..837J Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Accretion of Interplanetary Dust by AP and AM Stars
Authors: Kumar, C. Krishna; Davila, Joseph M.; Rajan, R. Sundar
1989ApJ...337..414K Altcode:
Accretion of interplanetary dust and comets by A-type stars is
investigated to see whether this process can explain the overabundances
of heavy elements in Ap and Am stars. The dust particles spiral in
by the Poynting-Robertson effect and evaporate above the star. This
process is evaluated by considering the evolution of silicate and
graphite particles in the radiation field of Alpha Leo (B7 V). It is
found that graphite particles evaporate above 20 stellar radii and
silicate dust grains above 50 stellar radii. The evaporated atoms will
be quickly ionized. In the case of Am stars the ions will wander off
and not reach the photosphere, but in the case of Ap stars they can be
trapped by the magnetic field of the star and reach the surface. The
magnetosphere of a typical Ap star is modeled, and the fate of the
ions is studied. The efficiency of accretion from the magnetosphere is
sensitive to the presence of any plasma in the magnetosphere. The comet
impact process is found capable of producing the abundance anomalies in
Ap as well as Am stars, assuming that the comet impact rate is 0.03/yr,
nearly the same as in the solar system.

---------------------------------------------------------
Title: A Theory for the Radiation of Magnetohydrodynamic Surface
Waves and Body Waves into the Solar Corona
Authors: Davila, Joseph M.
1988ApJ...332.1076D Altcode:
The Green's function for the slab coronal hole is obtained
explicitly. The Fourier integral representation for the radiated
field inside and outside the coronal hole waveguide is obtained. The
radiated field outside the coronal hole is calculated using the method
of steepest descents. It is shown that the radiated field can be written
as the sum of two contributions: (1) a contribution from the integral
along the steepest descent path and (2) a contribution from all the
poles of the integrand between the path of the original integral and
the steepest descent path. The free oscillations of the waveguide
can be associated with the pole contributions in the steepest descent
representation for the Green's function. These pole contributions are
essentially generalized surface waves with a maximum amplitude near the
interface which separates the plasma inside the coronal hole from the
surrounding background corona. The path contribution to the integral
is essentially the power radiated in body waves.

---------------------------------------------------------
Title: Guided Waves in Diverging Coronal Hole Waveguides
Authors: Davila, J. M.
1988BAAS...20..704D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The heating of coronal loops by MHD waves.
Authors: Davila, Joseph M.
1988sscd.conf...97D Altcode:
The purpose of this paper is to discuss some of the important
developments of the last few years and to illustrate the basic physics
of the resonant absorption process by considering dissipation in a
simple coronal loop model. It is concluded that resonance absorption is
a viable mechanism for the heating of solar active region coronal loops.

---------------------------------------------------------
Title: Resonance Absorption Heating in the Solar Corona
Authors: Davila, Joseph M.; Warnock, A., III
1987BAAS...19..937D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Heating of the Solar Corona by the Resonant Absorption of
Alfven Waves
Authors: Davila, Joseph M.
1987ApJ...317..514D Altcode:
An improved method for calculating the resonance absorption heating
rate is discussed and the results are compared with observations in the
solar corona. To accomplish this, the wave equation for a dissipative,
compressible plasma is derived from the linearized magnetohydrodynamic
equations for a plasma with transverse Alfven speed gradients. For
parameters representative of the solar corona, it is found that a
two-scale description of the wave motion is appropriate. The large-scale
motion, which can be approximated as nearly ideal, has a scale which is
on the order of the width of the loop. The small-scale wave, however,
has a transverse scale much smaller than the width of the loop, with
a width of about 0.3-250 km, and is highly dissipative. These two wave
motions are coupled in a narrow resonance region in the loop where the
global wave frequency equals the local Alfven wave frequency. Formally,
this coupling comes about from using the method of matched asymptotic
expansions to match the inner and outer (small and large scale)
solutions. The resultant heating rate can be calculated from either
of these solutions. A formula derived using the outer (ideal) solution
is presented, and shown to be consistent with observations of heating
and line broadening in the solar corona.

---------------------------------------------------------
Title: The Acceleration of Winds by MHD Waves in Open Magnetic
Structures
Authors: Davila, J. M.
1987sowi.conf..107D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Heating of the solar corona by the resonant absorption of
Alfvén waves.
Authors: Davila, Joseph M.
1986NASCP2442..445D Altcode: 1986copp.nasa..445D
An improved method for calculating the resonance absorption heating rate
is discussed and the results are compared with observations in the solar
corona. The primary conclusion to be drawn from these calculations is
that to the level of the approximation adopted, the observations of
the heating rate and nonthermal line broadening in the solar corona
are consistent with heating by the resonance absorption mechanism.

---------------------------------------------------------
Title: Heating the Solar Corona by the Resonant Absorption of
MHD Waves
Authors: Davila, J. M.
1986BAAS...18..677D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: MHD Wave-Driven Winds from Open Magnetic Structures
Authors: Davila, Joseph M.
1986LNP...254..463D Altcode: 1986csss....4..463D
No abstract at ADS

---------------------------------------------------------
Title: A leaky magnetohydrodynamic waveguide model for the
acceleration of high-speed solar wind streams in coronal holes
Authors: Davila, J. M.
1985ApJ...291..328D Altcode:
It is well established observationally that high-speed solar wind
streams originate in coronal hole regions in the solar corona. One
suggested source for the additional momentum of these streams is "wave
pressure" generated by magnetohydrodynamic (MHD) waves. In the paper
the effect of coronal hole magnetic structure on the propagation of
MHD waves of all periods is considered. It is found that the coronal
hole structure acts as a "leaky" MHD waveguide, i.e., wave flux which
enters at the base of the coronal hole is only weakly guided by the
coronal hole structure. The force on the coronal hole plasma due to the
propagation of the leaky wave modes is calculated. It is found that
the net force consists of two terms: (1) magnetic wave pressure and
(2) magnetic wave tension. The calculations imply that the coupling
of the solar wind plasma to the turbulence in the photosphere may not
be as efficient as previous theories of wave propagation in the corona
have indicated.

---------------------------------------------------------
Title: MHD Flux Leakage from a Turbulently Driven Coronal Hole
Authors: Davila, Joseph M.
1985BAAS...17..637D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A leaky waveguide model for MHD wave driven winds from
coronal holes.
Authors: Davila, J. M.
1985NASCP2358..183D Altcode: 1985onhm.rept..183D
High speed solar wind streams are now known to originate in discrete
open field magnetic structures within the solar corona called coronal
holes. The simple model presented in this paper demonstrates that
coronal holes can act as waveguides for MHD waves. These waves serve
as a source of additional acceleration for the solar wind.

---------------------------------------------------------
Title: The interplanetary scattering mean free path - Collisionless
wave-damping effects
Authors: Davila, J. M.; Scott, J. S.
1984ApJ...285..400D Altcode:
The role of dissipation in the scattering of charged particles in
the interplanetary medium (IPM) is analyzed to obtain a model for
the interplanetary magnetic turbulence spectrum that yields particle
free paths (PEP) which agree with observational data. The scattering
processes are attributed to waves with small wavelengths intersected
by particles with zero pitch angles. The waves, being strongly damped
by collisionless cyclotron damping in the ambient thermal plasma,
produce reduced scattering and longer MFPs. The model, which includes
the damping factor, was used to generate proton propagation maps
at kinetic energy levels of under, over, and within the 5 MeV-2 GeV
range. The results, when compared with observational data, displayed
good agreement. The same held true for the MFP propagation of energetic
electrons.

---------------------------------------------------------
Title: Coronal Holes: A Driven MHD Waveguide Model
Authors: Davila, J. M.
1984BAAS...16..928D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The scattering of energetic particles by waves in a finite
beta plasma
Authors: Davila, J. M.; Scott, J. S.
1984ApJ...280..334D Altcode:
Solutions to the dispersion relation for waves propagating parallel to
the ambient magnetic field in a plasma of arbitrary β are obtained,
where β is the ratio of the thermal pressure to the magnetic
pressure. The results of previous authors for wave frequencies, ω,
much less than the ion cyclotron frequency, Ωi, are extended
to include all frequencies less than the electron cyclotron frequency,
Ωe. It is found that the cyclotron turnovers, which occur
at Ωe(Ωi) for the right-hand (left-hand)
circularly polarized waves in a cold plasma, occur at significantly
lower frequencies in a finite β plasma. The precise limitations of the
"high β" approximation are established and details of wave propagation
in plasmas with intermediate values of β are examined.

---------------------------------------------------------
Title: Coronal Holes: Leaky MHD Waveguides
Authors: Davila, J. M.
1984BAAS...16..452D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Wave Propagation in Magnetic Coronal Loops
Authors: Davila, J. M.
1983BAAS...15R.700D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Resolution of the Solar Cosmic Ray Mean Free Path Controversy
Authors: Davila, J. M.; Scott, J. S.
1982BAAS...14..977D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Propagation of Energetic Particles in Finite Temperature
Astrophysical Plasmas.
Authors: Davila, Joseph Michael
1982PhDT........24D Altcode:
Solutions to the dispersion relation for waves propagating
parallel to the static magnetic field in a plasma of arbitrary
(beta) are obtained. ((beta) is the ratio of thermal to magnetic
pressure.) Resonant scattering by these waves is evaluated. It is found
that the magnetostatic approximation, used extensively in the past,
breaks down for particles with pitch angles near 90(DEGREES), and
one must consider the more complicated process of particle scattering
in electromagnetic turbulence. Many aspects of particle propagation
in a finite temperature plasma can be discussed without assuming
magnetostatic turbulence. This is accomplished by using a graphical
method to obtain the solutions of the resonance condition. Results
show that in a high (beta) plasma, wave damping causes a gap, or
hole, in (mu)-space where the resonant particle scattering rate
is severely depressed. It is found that only high energy ((gamma)
(GREATERTHEQ) 10('5)) electrons can be trapped within a typical
supernova remnant. When the notion of electromagnetic resonance
is applied to particle propagation in the interplanetary ((beta)(,
)&lt;(, )1) plasma, it is found that significant modifications to
the conventional scattering picture must be made. It is found that
a resonance gap exists which is similar to the one in a high (beta)
plasma. For electrons, this gap provides a natural explanation for
scatter-free events. Theory predicts that these events should occur
for kinetic energies T (LESSTHEQ) 300 keV while observations indicate
that the majority have T (LESSTHEQ) 500 keV. For protons and energetic
electrons, the scattering mean free path is critically dependent on
the non-resonant scattering rate for particles within the gap. This
fact provides a way to resolve the well known discrepancy between the
theoretical and observational values for the mean free path, (lamda).

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Title: The propagation of energetic particles in finite temperature
astrophysical plasmas
Authors: Davila, Joseph Michael
1982pepf.book.....D Altcode:
No abstract at ADS

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Title: Effects of particle drift on the transport of cosmic rays. IV -
More realistic diffusion coefficients
Authors: Jokipii, J. R.; Davila, J. M.
1981ApJ...248.1156J Altcode:
Results from numerical simulations of cosmic-ray modulations by the
solar wind are presented which show that the scattering mean free path
should be larger than the particle gyroradius in the average magnetic
field. It is found that the difference between drift and no-drift
solutions is not as great as in previous simulations, which violated
the mean free path constraint stated. Profound effects are still noted
for the drifts, which determine the origin of the bulk of the cosmic
rays seen at any given time in the inner solar system. Accordingly,
during the 1975 solar minimum, the positively charged cosmic rays seen
in the inner solar system came primarily from the outer boundary near
the heliospheric poles while negative particles came from the equatorial
regions of the boundary.

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Title: A Radiation Model for the VELA Pulsar
Authors: Davila, J.; Wright, C.; Benford, G.
1980Ap&SS..71...51D Altcode:
We model the Vela emission in radio, optical and gamma wavelengths. We
assume that radio emission occurs near the polar axis deep in the
magnetosphere. Optical and gamma radiation arises through ordinary
synchrotron mechanisms in a wide hollow cone, near the light
cylinder. Fitting of observed frequencies and luminosities in the
gamma and optical give reasonable plasma parameters, and indicate that
field-plasma pressure balance breaks down before the light cylinder,
as required by the picture. Some optical coherence is necessary if
we attribute both radio and optical emission to the same species of
particles, with γ∼100, but it is not required otherwise. Gamma-ray
pulses arise from γ∼105 electrons. We suggest a
single-pole orthogonal rotor picture which might account for the Vela
pulse phases.