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Author name code: straus
ADS astronomy entries on 2022-09-14
author:"Straus, Thomas"
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Title: Linking Small-scale Solar Wind Properties with Large-scale
Coronal Source Regions through Joint Parker Solar Probe-Metis/Solar
Orbiter Observations
Authors: Telloni, Daniele; Zank, Gary P.; Sorriso-Valvo, Luca;
D'Amicis, Raffaella; Panasenco, Olga; Susino, Roberto; Bruno, Roberto;
Perrone, Denise; Adhikari, Laxman; Liang, Haoming; Nakanotani, Masaru;
Zhao, Lingling; Hadid, Lina Z.; Sánchez-Cano, Beatriz; Verscharen,
Daniel; Velli, Marco; Grimani, Catia; Marino, Raffaele; Carbone,
Francesco; Mancuso, Salvatore; Biondo, Ruggero; Pagano, Paolo; Reale,
Fabio; Bale, Stuart D.; Kasper, Justin C.; Case, Anthony W.; de Wit,
Thierry Dudok; Goetz, Keith; Harvey, Peter R.; Korreck, Kelly E.;
Larson, Davin; Livi, Roberto; MacDowall, Robert J.; Malaspina, David
M.; Pulupa, Marc; Stevens, Michael L.; Whittlesey, Phyllis; Romoli,
Marco; Andretta, Vincenzo; Deppo, Vania Da; Fineschi, Silvano; Heinzel,
Petr; Moses, John D.; Naletto, Giampiero; Nicolini, Gianalfredo;
Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca; Capobianco,
Gerardo; Capuano, Giuseppe E.; Casini, Chiara; Casti, Marta; Chioetto,
Paolo; Corso, Alain J.; Leo, Yara De; Fabi, Michele; Frassati,
Federica; Frassetto, Fabio; Giordano, Silvio; Guglielmino, Salvo L.;
Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro; Magli,
Enrico; Massone, Giuseppe; Messerotti, Mauro; Pancrazzi, Maurizio;
Pelizzo, Maria G.; Romano, Paolo; Sasso, Clementina; Schühle, Udo;
Slemer, Alessandra; Straus, Thomas; Uslenghi, Michela; Volpicelli,
Cosimo A.; Zangrilli, Luca; Zuppella, Paola; Abbo, Lucia; Auchère,
Frédéric; Cuadrado, Regina Aznar; Berlicki, Arkadiusz; Ciaravella,
Angela; Lamy, Philippe; Lanzafame, Alessandro; Malvezzi, Marco;
Nicolosi, Piergiorgio; Nisticò, Giuseppe; Peter, Hardi; Solanki,
Sami K.; Strachan, Leonard; Tsinganos, Kanaris; Ventura, Rita; Vial,
Jean-Claude; Woch, Joachim; Zimbardo, Gaetano
2022ApJ...935..112T Altcode:
The solar wind measured in situ by Parker Solar Probe in the very
inner heliosphere is studied in combination with the remote-sensing
observation of the coronal source region provided by the METIS
coronagraph aboard Solar Orbiter. The coronal outflows observed near
the ecliptic by Metis on 2021 January 17 at 16:30 UT, between 3.5 and
6.3 R <SUB>⊙</SUB> above the eastern solar limb, can be associated
with the streams sampled by PSP at 0.11 and 0.26 au from the Sun,
in two time intervals almost 5 days apart. The two plasma flows
come from two distinct source regions, characterized by different
magnetic field polarity and intensity at the coronal base. It follows
that both the global and local properties of the two streams are
different. Specifically, the solar wind emanating from the stronger
magnetic field region has a lower bulk flux density, as expected,
and is in a state of well-developed Alfvénic turbulence, with low
intermittency. This is interpreted in terms of slab turbulence in the
context of nearly incompressible magnetohydrodynamics. Conversely,
the highly intermittent and poorly developed turbulent behavior of the
solar wind from the weaker magnetic field region is presumably due to
large magnetic deflections most likely attributed to the presence of
switchbacks of interchange reconnection origin.
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Title: Cosmic-ray flux predictions and observations for and with
Metis on board Solar Orbiter
Authors: Grimani, C.; Andretta, V.; Chioetto, P.; Da Deppo, V.; Fabi,
M.; Gissot, S.; Naletto, G.; Persici, A.; Plainaki, C.; Romoli, M.;
Sabbatini, F.; Spadaro, D.; Stangalini, M.; Telloni, D.; Uslenghi, M.;
Antonucci, E.; Bemporad, A.; Capobianco, G.; Capuano, G.; Casti, M.;
De Leo, Y.; Fineschi, S.; Frassati, F.; Frassetto, F.; Heinzel, P.;
Jerse, G.; Landini, F.; Liberatore, A.; Magli, E.; Messerotti, M.;
Moses, D.; Nicolini, G.; Pancrazzi, M.; Pelizzo, M. G.; Romano, P.;
Sasso, C.; Schühle, U.; Slemer, A.; Straus, T.; Susino, R.; Teriaca,
L.; Volpicelli, C. A.; Freiherr von Forstner, J. L.; Zuppella, P.
2021A&A...656A..15G Altcode: 2021arXiv210413700G
Context. The Metis coronagraph is one of the remote sensing instruments
hosted on board the ESA/NASA Solar Orbiter mission. Metis is devoted
to carry out the first simultaneous imaging of the solar corona in
both visible light (VL) and ultraviolet (UV). High-energy particles
can penetrate spacecraft materials and may limit the performance of
the on-board instruments. A study of the galactic cosmic-ray (GCR)
tracks observed in the first VL images gathered by Metis during the
commissioning phase is presented here. A similar analysis is planned
for the UV channel. <BR /> Aims: We aim to formulate a prediction of
the GCR flux up to hundreds of GeV for the first part of the Solar
Orbiter mission to study the performance of the Metis coronagraph. <BR
/> Methods: The GCR model predictions are compared to observations
gathered on board Solar Orbiter by the High-Energy Telescope in the
range between 10 MeV and 100 MeV in the summer of 2020 as well as with
the previous measurements. Estimated cosmic-ray fluxes above 70 MeV
n<SUP>−1</SUP> have been also parameterized and used for Monte Carlo
simulations aimed at reproducing the cosmic-ray track observations in
the Metis coronagraph VL images. The same parameterizations can also
be used to study the performance of other detectors. <BR /> Results:
By comparing observations of cosmic-ray tracks in the Metis VL images
with FLUKA Monte Carlo simulations of cosmic-ray interactions in
the VL detector, we find that cosmic rays fire only a fraction, on
the order of 10<SUP>−4</SUP>, of the whole image pixel sample. We
also find that the overall efficiency for cosmic-ray identification
in the Metis VL images is approximately equal to the contribution
of Z ≥ 2 GCR particles. A similar study will be carried out during
the whole of the Solar Orbiter's mission duration for the purposes of
instrument diagnostics and to verify whether the Metis data and Monte
Carlo simulations would allow for a long-term monitoring of the GCR
proton flux.
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Title: First light observations of the solar wind in the outer corona
with the Metis coronagraph
Authors: Romoli, M.; Antonucci, E.; Andretta, V.; Capuano, G. E.; Da
Deppo, V.; De Leo, Y.; Downs, C.; Fineschi, S.; Heinzel, P.; Landini,
F.; Liberatore, A.; Naletto, G.; Nicolini, G.; Pancrazzi, M.; Sasso,
C.; Spadaro, D.; Susino, R.; Telloni, D.; Teriaca, L.; Uslenghi,
M.; Wang, Y. -M.; Bemporad, A.; Capobianco, G.; Casti, M.; Fabi, M.;
Frassati, F.; Frassetto, F.; Giordano, S.; Grimani, C.; Jerse, G.;
Magli, E.; Massone, G.; Messerotti, M.; Moses, D.; Pelizzo, M. -G.;
Romano, P.; Schühle, U.; Slemer, A.; Stangalini, M.; Straus, T.;
Volpicelli, C. A.; Zangrilli, L.; Zuppella, P.; Abbo, L.; Auchère,
F.; Aznar Cuadrado, R.; Berlicki, A.; Bruno, R.; Ciaravella, A.;
D'Amicis, R.; Lamy, P.; Lanzafame, A.; Malvezzi, A. M.; Nicolosi,
P.; Nisticò, G.; Peter, H.; Plainaki, C.; Poletto, L.; Reale, F.;
Solanki, S. K.; Strachan, L.; Tondello, G.; Tsinganos, K.; Velli,
M.; Ventura, R.; Vial, J. -C.; Woch, J.; Zimbardo, G.
2021A&A...656A..32R Altcode: 2021arXiv210613344R
In this work, we present an investigation of the wind in the solar
corona that has been initiated by observations of the resonantly
scattered ultraviolet emission of the coronal plasma obtained with
UVCS-SOHO, designed to measure the wind outflow speed by applying
Doppler dimming diagnostics. Metis on Solar Orbiter complements the
UVCS spectroscopic observations that were performed during solar
activity cycle 23 by simultaneously imaging the polarized visible
light and the H I Lyman-α corona in order to obtain high spatial and
temporal resolution maps of the outward velocity of the continuously
expanding solar atmosphere. The Metis observations, taken on May 15,
2020, provide the first H I Lyman-α images of the extended corona
and the first instantaneous map of the speed of the coronal plasma
outflows during the minimum of solar activity and allow us to identify
the layer where the slow wind flow is observed. The polarized visible
light (580-640 nm) and the ultraviolet H I Lyα (121.6 nm) coronal
emissions, obtained with the two Metis channels, were combined in
order to measure the dimming of the UV emission relative to a static
corona. This effect is caused by the outward motion of the coronal
plasma along the direction of incidence of the chromospheric photons
on the coronal neutral hydrogen. The plasma outflow velocity was then
derived as a function of the measured Doppler dimming. The static
corona UV emission was simulated on the basis of the plasma electron
density inferred from the polarized visible light. This study leads
to the identification, in the velocity maps of the solar corona, of
the high-density layer about ±10° wide, centered on the extension
of a quiet equatorial streamer present at the east limb - the coronal
origin of the heliospheric current sheet - where the slowest wind
flows at about 160 ± 18 km s<SUP>−1</SUP> from 4 R<SUB>⊙</SUB>
to 6 R<SUB>⊙</SUB>. Beyond the boundaries of the high-density layer,
the wind velocity rapidly increases, marking the transition between
slow and fast wind in the corona.
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Title: Exploring the Solar Wind from Its Source on the Corona into
the Inner Heliosphere during the First Solar Orbiter-Parker Solar
Probe Quadrature
Authors: Telloni, Daniele; Andretta, Vincenzo; Antonucci, Ester;
Bemporad, Alessandro; Capuano, Giuseppe E.; Fineschi, Silvano;
Giordano, Silvio; Habbal, Shadia; Perrone, Denise; Pinto, Rui F.;
Sorriso-Valvo, Luca; Spadaro, Daniele; Susino, Roberto; Woodham, Lloyd
D.; Zank, Gary P.; Romoli, Marco; Bale, Stuart D.; Kasper, Justin C.;
Auchère, Frédéric; Bruno, Roberto; Capobianco, Gerardo; Case,
Anthony W.; Casini, Chiara; Casti, Marta; Chioetto, Paolo; Corso,
Alain J.; Da Deppo, Vania; De Leo, Yara; Dudok de Wit, Thierry;
Frassati, Federica; Frassetto, Fabio; Goetz, Keith; Guglielmino,
Salvo L.; Harvey, Peter R.; Heinzel, Petr; Jerse, Giovanna; Korreck,
Kelly E.; Landini, Federico; Larson, Davin; Liberatore, Alessandro;
Livi, Roberto; MacDowall, Robert J.; Magli, Enrico; Malaspina, David
M.; Massone, Giuseppe; Messerotti, Mauro; Moses, John D.; Naletto,
Giampiero; Nicolini, Gianalfredo; Nisticò, Giuseppe; Panasenco,
Olga; Pancrazzi, Maurizio; Pelizzo, Maria G.; Pulupa, Marc; Reale,
Fabio; Romano, Paolo; Sasso, Clementina; Schühle, Udo; Stangalini,
Marco; Stevens, Michael L.; Strachan, Leonard; Straus, Thomas; Teriaca,
Luca; Uslenghi, Michela; Velli, Marco; Verscharen, Daniel; Volpicelli,
Cosimo A.; Whittlesey, Phyllis; Zangrilli, Luca; Zimbardo, Gaetano;
Zuppella, Paola
2021ApJ...920L..14T Altcode: 2021arXiv211011031T
This Letter addresses the first Solar Orbiter (SO)-Parker Solar
Probe (PSP) quadrature, occurring on 2021 January 18 to investigate
the evolution of solar wind from the extended corona to the inner
heliosphere. Assuming ballistic propagation, the same plasma volume
observed remotely in the corona at altitudes between 3.5 and 6.3
solar radii above the solar limb with the Metis coronagraph on SO
can be tracked to PSP, orbiting at 0.1 au, thus allowing the local
properties of the solar wind to be linked to the coronal source region
from where it originated. Thanks to the close approach of PSP to the
Sun and the simultaneous Metis observation of the solar corona, the
flow-aligned magnetic field and the bulk kinetic energy flux density
can be empirically inferred along the coronal current sheet with an
unprecedented accuracy, allowing in particular estimation of the Alfvén
radius at 8.7 solar radii during the time of this event. This is thus
the very first study of the same solar wind plasma as it expands from
the sub-Alfvénic solar corona to just above the Alfvén surface.
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Title: In-flight optical performance assessment for the Metis solar
coronagraph
Authors: Da Deppo, Vania; Chioetto, Paolo; Andretta, Vincenzo; Casini,
Chiara; Frassetto, Fabio; Slemer, Alessandra; Zuppella, Paola; Romoli,
Marco; Fineschi, Silvano; Heinzel, Petr; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Stangalini, Marco; Teriaca, Luca;
Bemporad, Alessandro; Casti, Marta; Fabi, Michele; Grimani, Catia;
Heerlein, Klaus; Jerse, Giovanna; Landini, Federico; Liberatore,
Alessandro; Magli, Enrico; Melich, Radek; Pancrazzi, Maurizio; Pelizzo,
Maria-G.; Romano, Paolo; Sasso, Clementina; Straus, Thomas; Susino,
Roberto; Uslenghi, Michela; Volpicelli, Cosimo Antonio
2021SPIE11852E..10D Altcode:
Metis is a multi-wavelength coronagraph onboard the European Space
Agency (ESA) Solar Orbiter mission. The instrument features an
innovative instrument design conceived for simultaneously imaging the
Sun's corona in the visible and ultraviolet range. The Metis visible
channel employs broad-band, polarized imaging of the visible K-corona,
while the UV one uses narrow-band imaging at the HI Ly , i.e. 121.6
nm. During the commissioning different acquisitions and activities,
performed with both the Metis channels, have been carried out with the
aim to check the functioning and the performance of the instrument. In
particular, specific observations of stars have been devised to assess
the optical alignment of the telescope and to derive the instrument
optical parameters such as focal length, PSF and possibly check the
optical distortion and the vignetting function. In this paper, the
preliminary results obtained for the PSF of both channels and the
determination of the scale for the visible channel will be described
and discussed. The in-flight obtained data will be compared to those
obtained on-ground during the calibration campaign.
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Title: On-ground flat-field calibration of the Metis coronagraph
onboard the Solar Orbiter ESA mission
Authors: Casini, C.; Da Deppo, V.; Zuppella, P.; Chioetto, P.; Slemer,
A.; Frassetto, F.; Romoli, M.; Landini, F.; Pancrazzi, M.; Andretta,
V.; De Leo, Y.; Bemporad, A.; Fabi, M.; Fineschi, S.; Frassati, F.;
Grimani, C.; Jerse, G.; Heerlein, K.; Liberatore, A.; Magli, E.;
Naletto, G.; Nicolini, G.; Pelizzo, M. G.; Romano, P.; Sasso, C.;
Spadaro, D.; Stangalini, M.; Straus, T.; Susino, R.; Teriaca, L.;
Uslenghi, M.; Casti, M.; Heinzel, P.; Volpicelli, A.
2021SPIE11852E..5BC Altcode:
Solar Orbiter, launched on February 9<SUP>th</SUP> 2020, is an
ESA/NASA mission conceived to study the Sun. This work presents
the embedded Metis coronagraph and its on-ground calibration in the
580-640 nm wavelength range using a flat field panel. It provides
a uniform illumination to evaluate the response of each pixel of
the detector; and to characterize the Field of View (FoV) of the
coronagraph. Different images with different exposure times were
acquired during the on-ground calibration campaign. They were analyzed
to verify the linearity response of the instrument and the requirements
for the FoV: the maximum area of the sky that Metis can acquire.
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Title: Challenges during Metis-Solar Orbiter commissioning phase
Authors: Romoli, Marco; Andretta, Vincenzo; Bemporad, Alessandro;
Casti, Marta; Da Deppo, Vania; De Leo, Yara; Fabi, Michele; Fineschi,
Silvano; Frassetto, Fabio; Grimani, Catia; Heerlein, Klaus; Heinzel,
Petr; Jerse, Giovanna; Landini, Federico; Liberatore, Alessandro;
Magli, Enrico; Naletto, Giampiero; Nicolini, Gianalfredo; Pancrazzi,
Maurizio; Pelizzo, Maria Guglielmina; Romano, Paolo; Sasso, Clementina;
Schühle, Udo; Slemer, Alessandra; Spadaro, Daniele; Straus, Thomas;
Susino, Roberto; Teriaca, Luca; Uslenghi, Michela; Volpicelli, Cosimo
Antonio; Zupella, Paola
2021SPIE11852E..5AR Altcode:
Metis is the visible light and UV light imaging coronagraph on board
the ESA-NASA mission Solar Orbiter that has been launched February 10th,
2020, from Cape Canaveral. Scope of the mission is to study the Sun up
close, taking high-resolution images of the Sun's poles for the first
time, and understanding the Sun-Earth connection. Metis coronagraph
will image the solar corona in the linearly polarized broadband visible
radiation and in the UV HI Ly-α line from 1.6 to 3 solar radii when at
Solar Orbiter perihelion, providing a diagnostics, with unprecedented
temporal coverage and spatial resolution, of the structures and dynamics
of the full corona. Solar Orbiter commissioning phase big challenge was
Covid-19 social distancing phase that affected the way commissioning
of a spacecraft and its payload is typically done. Metis coronagraph
on-board Solar Orbiter had its additional challenges: to wake up and
check the performance of the optical, electrical and thermal subsystems,
most of them unchecked since Metis delivery to spacecraft prime, Airbus,
in May 2017. The roadmap to the fully commissioned coronagraph is here
described throughout the steps from the software functional test,
the switch on of the detectors of the two channels, UV and visible,
to the optimization of the occulting system and the characterization
of the instrumental stray light, one of the most challenging features
in a coronagraph.
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Title: In-flight calibration of Metis coronagraph on board of
Solar Orbiter
Authors: Liberatore, A.; Fineschi, S.; Casti, M.; Capobianco, G.;
Romoli, M.; Andretta, V.; Bemporad, A.; Da Deppo, V.; De Leo, Y.; Fabi,
M.; Frassetto, F.; Grimani, C.; Heerlein, K.; Heinzel, P.; Jerse,
G.; Landini, F.; Magli, E.; Naletto, G.; Nicolini, G.; Pancrazzi,
M.; Pelizzo, M. G.; Romano, P.; Sasso, C.; Slemer, A.; Spadaro, D.;
Straus, T.; Susino, R.; Teriaca, L.; Uslenghi, M.; Volpicelli, C. A.;
Zuppella, P.
2021SPIE11852E..48L Altcode:
Metis coronagraph is one of the remote-sensing instruments of the Solar
Orbiter mission launched at the begin of 2020. The mission profile will
allow for the first time the remote-sensing observation of the Sun
from a very close distance and increasing the latitude with respect
to the ecliptic plane. In particular, Metis is aimed at the overall
characterization and study of the solar corona and solar wind. Metis
instrument acquires images of the solar corona in two different
wavelengths simultaneously; ultraviolet (UV) and visible-light (VL). The
VL channel includes a polarimeter with an electro-optically modulating
Liquid Crystal Variable Retarder (LCVR) to measure the linearly
polarized brighness pB) of the K-corona. This paper presents part of
the in-flight calibration results for both wavelength channels together
with a comparison with on-ground calibrations. The orientation of the
K-corona linear polarization was used for the in-flight calibration
of the Metis polarimeter. This paper describes the correction of the
on-ground VL vignetting function after the in-flight adjustment of
the internal occulter. The same vignetting function was adaptated to
the UV channel.
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Title: The signature of granulation in a solar power spectrum as
seen with CO<SUP>5</SUP>BOLD
Authors: Lundkvist, Mia S.; Ludwig, Hans-Günter; Collet, Remo;
Straus, Thomas
2021MNRAS.501.2512L Altcode: 2020arXiv201110045L; 2020MNRAS.tmp.3425L
The granulation background seen in the power spectrum of a solar-like
oscillator poses a serious challenge for extracting precise and detailed
information about the stellar oscillations. Using a 3D hydrodynamical
simulation of the Sun computed with CO<SUP>5</SUP>BOLD, we investigate
various background models to infer, using a Bayesian methodology,
which one provides the best fit to the background in the simulated
power spectrum. We find that the best fit is provided by an expression
including the overall power level and two characteristic frequencies,
one with an exponent of two and one with a free exponent taking on a
value around six. We assess the impact of the 3D hydro-code on this
result by repeating the analysis with a simulation from S TAGGER and
find that the main conclusion is unchanged. However, the details of
the resulting best fits differ slightly between the two codes, but we
explain this difference by studying the effect of the spatial resolution
and the duration of the simulation on the fit. Additionally, we look
into the impact of adding white noise to the simulated time series as
a simple way to mimic a real star. We find that, as long as the noise
level is not too low, the results are consistent with the no-noise case.
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Title: The MDOR/PDOR on-line module for MISO, the planning software
of Solar Orbiter instruments
Authors: Volpicelli, Cosimo; Landini, Federico; Pancrazzi, Maurizio;
Straus, Thomas; Susino, Roberto; Nicolini, Gianalfredo; Sasso,
Clementina; Fabi, Michele; De Leo, Yara; Casini, Chiara; Naletto,
Giampiero; Nicolosi, Piergiorgio; Spadaro, Daniele; Andretta, Vincenzo;
Antonucci, Ester; Fineschi, Silvano; Da Deppo, Vania; Zuppella, Paola;
Frassetto, Fabio; Slemer, Alessandra; Mercier, Claude; Kouliche,
Dimitri; Caminade, Stephane; Picard, David; Buchlin, Eric; Auchère,
Frédéric; Romoli, Marco
2020SPIE11452E..0SV Altcode:
Solar Orbiter is a solar mission that will approach the Sun down to a
minimum perihelion of 0.28 AU and will increase its orbit inclination
with respect to the ecliptic up to a maximum angle of 34 deg. For
imagers aboard Solar Orbiter there will be three 10-days remote sensing
windows per orbit. Observations shall be carefully planned at least 6
months in advance. The Multi Instrument Sequence Organizer (MISO) is
a web based platform developed by the SPICE group and made available
to support Solar Orbiter instruments teams in planning observations
by assembling Mission Database sequences. Metis is the UV and visible
light coronagraph aboard Solar Orbiter. Metis is a complex instrument
characterized by a rich variety of observing modes, which required a
careful commissioning activity and will need support for potential
maintenance operations throughout the mission. In order to support
commissioning and maintenance activities, the Metis team developed
a PDOR (Payload Direct Operation Request) and MDOR (Memory Direct
Operation Request) module integrated in MISO and made available to all
Solar Orbiter instruments. An effort was made in order to interpret
the coding philosophy of the main project and to make the additional
module as homogeneous as possible both to the web interface and to the
algorithm logic, while integrating characteristics which are peculiar
to PDORs and MDORs. An user friendly web based interface allows the
operator to build the operation request and to successively modify or
integrate it with further or alternative information. In the present
work we describe the PDOR/MDOR module for MISO by addressing its logic
and main characteristics.
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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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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. <BR /> 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.
---------------------------------------------------------
Title: Metis: the Solar Orbiter visible light and ultraviolet
coronal imager
Authors: Antonucci, Ester; Romoli, Marco; Andretta, Vincenzo; Fineschi,
Silvano; Heinzel, Petr; Moses, J. Daniel; Naletto, Giampiero; Nicolini,
Gianalfredo; Spadaro, Daniele; Teriaca, Luca; Berlicki, Arkadiusz;
Capobianco, Gerardo; Crescenzio, Giuseppe; Da Deppo, Vania; Focardi,
Mauro; Frassetto, Fabio; Heerlein, Klaus; Landini, Federico; Magli,
Enrico; Marco Malvezzi, Andrea; Massone, Giuseppe; Melich, Radek;
Nicolosi, Piergiorgio; Noci, Giancarlo; Pancrazzi, Maurizio; Pelizzo,
Maria G.; Poletto, Luca; Sasso, Clementina; Schühle, Udo; Solanki,
Sami K.; Strachan, Leonard; Susino, Roberto; Tondello, Giuseppe;
Uslenghi, Michela; Woch, Joachim; Abbo, Lucia; Bemporad, Alessandro;
Casti, Marta; Dolei, Sergio; Grimani, Catia; Messerotti, Mauro;
Ricci, Marco; Straus, Thomas; Telloni, Daniele; Zuppella, Paola;
Auchère, Frederic; Bruno, Roberto; Ciaravella, Angela; Corso,
Alain J.; Alvarez Copano, Miguel; Aznar Cuadrado, Regina; D'Amicis,
Raffaella; Enge, Reiner; Gravina, Alessio; Jejčič, Sonja; Lamy,
Philippe; Lanzafame, Alessandro; Meierdierks, Thimo; Papagiannaki,
Ioanna; Peter, Hardi; Fernandez Rico, German; Giday Sertsu, Mewael;
Staub, Jan; Tsinganos, Kanaris; Velli, Marco; Ventura, Rita; Verroi,
Enrico; Vial, Jean-Claude; Vives, Sebastien; Volpicelli, Antonio;
Werner, Stephan; Zerr, Andreas; Negri, Barbara; Castronuovo, Marco;
Gabrielli, Alessandro; Bertacin, Roberto; Carpentiero, Rita; Natalucci,
Silvia; Marliani, Filippo; Cesa, Marco; Laget, Philippe; Morea, Danilo;
Pieraccini, Stefano; Radaelli, Paolo; Sandri, Paolo; Sarra, Paolo;
Cesare, Stefano; Del Forno, Felice; Massa, Ernesto; Montabone, Mauro;
Mottini, Sergio; Quattropani, Daniele; Schillaci, Tiziano; Boccardo,
Roberto; Brando, Rosario; Pandi, Arianna; Baietto, Cristian; Bertone,
Riccardo; Alvarez-Herrero, Alberto; García Parejo, Pilar; Cebollero,
María; Amoruso, Mauro; Centonze, Vito
2020A&A...642A..10A Altcode: 2019arXiv191108462A
<BR /> Aims: Metis is the first solar coronagraph designed for a
space mission and is capable of performing simultaneous imaging of the
off-limb solar corona in both visible and UV light. The observations
obtained with Metis aboard the Solar Orbiter ESA-NASA observatory
will enable us to diagnose, with unprecedented temporal coverage and
spatial resolution, the structures and dynamics of the full corona
in a square field of view (FoV) of ±2.9° in width, with an inner
circular FoV at 1.6°, thus spanning the solar atmosphere from 1.7
R<SUB>⊙</SUB> to about 9 R<SUB>⊙</SUB>, owing to the eccentricity
of the spacecraft orbit. Due to the uniqueness of the Solar Orbiter
mission profile, Metis will be able to observe the solar corona
from a close (0.28 AU, at the closest perihelion) vantage point,
achieving increasing out-of-ecliptic views with the increase of the
orbit inclination over time. Moreover, observations near perihelion,
during the phase of lower rotational velocity of the solar surface
relative to the spacecraft, allow longer-term studies of the off-limb
coronal features, thus finally disentangling their intrinsic evolution
from effects due to solar rotation. <BR /> Methods: Thanks to a novel
occultation design and a combination of a UV interference coating of
the mirrors and a spectral bandpass filter, Metis images the solar
corona simultaneously in the visible light band, between 580 and 640
nm, and in the UV H I Lyman-α line at 121.6 nm. The visible light
channel also includes a broadband polarimeter able to observe the
linearly polarised component of the K corona. The coronal images in
both the UV H I Lyman-α and polarised visible light are obtained at
high spatial resolution with a spatial scale down to about 2000 km
and 15 000 km at perihelion, in the cases of the visible and UV light,
respectively. A temporal resolution down to 1 s can be achieved when
observing coronal fluctuations in visible light. <BR /> Results: The
Metis measurements, obtained from different latitudes, will allow for
complete characterisation of the main physical parameters and dynamics
of the electron and neutral hydrogen/proton plasma components of the
corona in the region where the solar wind undergoes the acceleration
process and where the onset and initial propagation of coronal mass
ejections (CMEs) take place. The near-Sun multi-wavelength coronal
imaging performed with Metis, combined with the unique opportunities
offered by the Solar Orbiter mission, can effectively address crucial
issues of solar physics such as: the origin and heating/acceleration
of the fast and slow solar wind streams; the origin, acceleration,
and transport of the solar energetic particles; and the transient
ejection of coronal mass and its evolution in the inner heliosphere,
thus significantly improving our understanding of the region connecting
the Sun to the heliosphere and of the processes generating and driving
the solar wind and coronal mass ejections. <BR /> Conclusions: This
paper presents the scientific objectives and requirements, the overall
optical design of the Metis instrument, the thermo-mechanical design,
and the processing and power unit; reports on the results of the
campaigns dedicated to integration, alignment, and tests, and to
the characterisation of the instrument performance; describes the
operation concept, data handling, and software tools; and, finally,
the diagnostic techniques to be applied to the data, as well as a brief
description of the expected scientific products. The performance of the
instrument measured during calibrations ensures that the scientific
objectives of Metis can be pursued with success. <P />Metis website:
<A href="http://metis.oato.inaf.it">http://metis.oato.inaf.it</A>
---------------------------------------------------------
Title: Preface
Authors: Bemporad, A.; Criscuoli, S.; Del Moro, D.; Guglielmino,
S. L.; Landi, S.; Laurenza, M.; Reale, F.; Straus, T.; Vecchio, A.
2019NCimC..42....1B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The third CO5BOLD workshop
Authors: Straus, T.; Marconi, M.; Alcalà, J. M.
2017MmSAI..88....5S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: A virtual appliance as proxy pipeline for the Solar
Orbiter/Metis coronagraph
Authors: Pancrazzi, M.; Straus, T.; Andretta, V.; Spadaro, D.; Haugan,
S. V.; de Groof, A.; Carr, R.; Focardi, M.; Nicolini, G.; Landini,
F.; Baccani, C.; Romoli, M.; Antonucci, E.
2016SPIE.9913E..4LP Altcode:
Metis is the coronagraph on board Solar Orbiter, the ESA mission devoted
to the study of the Sun that will be launched in October 2018. Metis is
designed to perform imaging of the solar corona in the UV at 121.6 nm
and in the visible range where it will accomplish polarimetry studies
thanks to a variable retarder plate. Due to mission constraints, the
telemetry downlink on the spacecraft will be limited and data will be
downloaded with delays that could reach, in the worst case, several
months. In order to have a quick overview on the ongoing operations
and to check the safety of the 10 instruments on board, a high-priority
downlink channel has been foreseen to download a restricted amount of
data. These so-called Low Latency Data will be downloaded daily and,
since they could trigger possible actions, they have to be quickly
processed on ground as soon as they are delivered. To do so, a proper
processing pipeline has to be developed by each instrument. This
tool will then be integrated in a single system at the ESA Science
Operation Center that will receive the downloaded data by the Mission
Operation Center. This paper will provide a brief overview of the on
board processing and data produced by Metis and it will describe the
proxy-pipeline currently under development to deal with the Metis
low-latency data.
---------------------------------------------------------
Title: Testing Wave Propagation Properties in the Solar Chromosphere
with ALMA and IRIS
Authors: Fleck, Bernard; Straus, Thomas; Wedemeyer, Sven
2016SPD....47.0102F Altcode:
Waves and oscillations are interesting not only from the point of view
that they can propagate energy into the chromosphere and dissipate that
energy to produce non-radiative heating, they also carry information
about the structure of the atmosphere in which they propagate. Since
the late 80s there is substantial evidence that the chromospheric
wave field is dominated by a non-propagating component, presumably
resulting from wave reflection at the transition region. Observations
of Doppler oscillations measured in the Ca II infrared tripet lines,
Ca II K, and He 10830 all show vanishing phase lags (i.e. vanishing
travel time differences) between the various lines, in particular also
for frequencies above the cut-off frequency. Why is the apparent phase
speed of high frequency acoustic waves in the chromosphere so high? Are
these results misleading because of complex radiation transfer effects
in these optically thick lines? ALMA, which acts as a linear thermometer
of the solar chromosphere, will provide measurements of the local
plasma conditions that should be, at least in principle, much easier
to interpret. Multi-wavelength time series of ALMA observations of the
temperature fluctuations of inter-network oscillations should allow
travel time measurements between different heights as these disturbances
propagate through the chromosphere and thus should finally settle the
long-standing question about the propagation characteristics of high
frequency acoustic waves in the chromosphere. We plan to combine ALMA
mm-observations with high resolution IRIS observations in the Mg II
h and k lines, and until ALMA observations are available, will study
the expected signals using time series of mm-maps from 3D radiation
hydrodynamics simulations that are being prepared within the framework
of the Solar Simulations for the Atacama Large Millimeter Observatory
Network (SSALMON).
---------------------------------------------------------
Title: A steady-state supersonic downflow in the transition region
above a sunspot umbra
Authors: Straus, Thomas; Fleck, Bernhard; Andretta, Vincenzo
2015A&A...582A.116S Altcode: 2015arXiv150704279S
We investigate a small-scale (~1.5 Mm along the slit), supersonic
downflow of about 90 km s<SUP>-1</SUP> in the transition region
above the lightbridged sunspot umbra in AR 11836. The observations
were obtained with the Interface Region Spectrograph (IRIS) on
2013 September 2 from 16:40 to 17:59 UT. The downflow shows up as
redshifted "satellite" lines of the Si iv and O iv transition region
lines and is remarkably steady over the observing period of nearly
80 min. The downflow is not visible in the chromospheric lines,
which only show an intensity enhancement at the location of the
downflow. The density inferred from the line ratio of the redshifted
satellites of the O iv lines (N<SUB>e</SUB> = 10<SUP>10.6 ± 0.25</SUP>
cm<SUP>-3</SUP>) is only a factor 2 smaller than the one inferred
from the main components (N<SUB>e</SUB> = 10<SUP>10.95 ± 0.20</SUP>
cm<SUP>-3</SUP>). Consequently, this implies a substantial mass flux
(~5 × 10<SUP>-7</SUP> g cm<SUP>-2</SUP> s<SUP>-1</SUP>), which would
evacuate the overlying corona on timescales close to 10 s. We interpret
these findings as evidence of a stationary termination shock of a
supersonic siphon flow in a cool loop that is rooted in the central
umbra of the spot. <P />The movie is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201525805/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: Observations of a Steady-State Supersonic Downflow in the
Transition Region above a Sunspot Umbra
Authors: Fleck, Bernhard; Straus, Thomas; Andretta, Vincenzo
2015TESS....120311F Altcode:
Sunspots have been an area of intense research ever since Hale's
discovery of strong magnetic fields in these structures. Here we report
on the detection of a particular sunspot phenomenon: a small-scale (~
1.5 Mm), supersonic downflow of about 90 km/s in the transition region
above a light-bridged sunspot umbra. The observations were obtained with
the Interface Imaging Region Spectrograph (IRIS) on 2 September 2013
from 16:39 to 17:58 UT in the sunspot of AR 11836 near disk center. Slit
length and width were 68” and 0.166”, respectively. The cadence of
the time series was 3 s, with exposure times of 2 s. The observations
comprise nine spectral windows: C II 1336, Fe XII 1349, Cl I 1352,
O I 1356, Si IV 1394, Si IV 1403, NUV at 2786 and 2831, and Mg II h
and k 2796. The spectral window containing the Si IV 1403 line also
includes the O IV 1400, 1401, and 1405 lines, the last one blended
with a S IV line. The downflow shows up as red-shifted, well-separated
“satellite” lines of the Si IV and O IV transition region lines and
is remarkably steady over the observing period of nearly 80 min. The
satellite lines do not participate in the 3-min shock wave Doppler
maneuvres of the main component. The downflow is not visible in the
chromospheric lines, which only show an intensity enhancement at the
location of the downflow. The density inferred from the line ratio of
the redshifted satellites of the O IV lines (N<SUB>e</SUB>=10<SUP>10.5
±0.3 </SUP>cm<SUP>-3</SUP>) is only a factor 2.5 smaller than the
one inferred from the main components (N<SUB>e</SUB>=10<SUP>10.9 ±0.2
</SUP>cm<SUP>-3</SUP>). Consequently, this implies a substantial mass
flux (~ 4×10<SUP>-7</SUP> g cm<SUP>-2</SUP> s<SUP>-1</SUP>), which
would evacuate the overlying corona on time scales of the order of 10
s. We interpret these findings as evidence of a stationary termination
shock of a supersonic siphon flow in a cool loop rooted in the central
umbra of the spot. Such stationary shocks have been predicted for
siphon flows in hot coronal loops by Noci (1981).
---------------------------------------------------------
Title: Wave Propagation in the Internetwork Chromosphere: Comparing
IRIS Observations of Mg II h and k with Simulations
Authors: Fleck, B.; De Pontieu, B.; Leenaarts, J.; Pereira, T. M. D.;
Straus, T.
2014AGUFMSH51C4174F Altcode:
The objective of this study is to explore the dynamics of the
upper internetwork chromosphere using high-resolution spectroscopic
"sit-and-stare" time series obtained with the Interface Region Imaging
Spectrogragh (IRIS) in the Mg II h and k lines. The Mg II h and k lines
reveal a particularly complex spatio-temporal behavior, which strongly
depends on the magnetic field topology. We focus on six parameters in
both the h and k line: the Doppler shift and intensity of the central
reversal (h3 and k3) and the blue and red emission peaks (h2v, h2r,
k2v, k2r). In an effort to better understand what physical parameters
can be extracted from these lines and to put our interpretation of
the observations on more solid grounds, we extend our analysis to
synthetic spectra obtained from numerical simulations and compare the
results to the observations.
---------------------------------------------------------
Title: On-board CME detection algorithm for the Solar Orbiter-METIS
coronagraph
Authors: Bemporad, A.; Andretta, V.; Pancrazzi, M.; Focardi, M.;
Straus, T.; Sasso, C.; Spadaro, D.; Uslenghi, M.; Antonucci, E.;
Fineschi, S.; Abbo, L.; Nicolini, G.; Landini, F.; Romoli, M.; Naletto,
G.; Nicolosi, P.
2014SPIE.9152E..0KB Altcode:
The METIS coronagraph is one of the instruments part of the payload of
the ESA - Solar Orbiter mission to be launched in 2017. The spacecraft
will operate much like a planetary encounter mission, with the main
scientific activity taking place with the remote-sensing instruments
during three 10-days intervals per orbit: optimization of the different
instrument observing modes will be crucial. One of the key scientific
targets of METIS will be the study of transient ejections of mass
through the solar corona (Coronal Mass Ejections - CMEs) and their
heliospheric evolution. METIS will provide for the first time imaging of
CMEs in two different wavelengths: VL (visible light 580- 640 nm) and UV
(Lyman-α line of HI at 121.6 nm). The detection of transient phenomena
shall be managed directly by the METIS Processing and Power Unit (MPPU)
by means of both external triggers ("flags") coming from other Solar
Orbiter instruments, and internal "flags" produced directly by the METIS
on-board software. METIS on-board algorithm for the automatic detection
of CMEs will be based on running differences between consecutive images
re-binned to very low resolution and thresholded for significant changes
over a minimum value. Given the small relative variation of white light
intensity during CMEs, the algorithm will take advantage of VL images
acquired with different polarization angles to maximize the detection
capability: possible false detections should be automatically managed
by the algorithm. The algorithm will be able to provide the CME first
detection time, latitudinal direction of propagation on the plane
of the sky (within 45 degrees), a binary flag indicating whether a
"halo CME" has been detected.
---------------------------------------------------------
Title: On-board detection and removal of cosmic ray and solar
energetic particle signatures for the Solar Orbiter-METIS coronagraph
Authors: Andretta, V.; Bemporad, A.; Focardi, M.; Grimani, C.;
Landini, F.; Pancrazzi, M.; Sasso, C.; Spadaro, D.; Straus, T.;
Uslenghi, M. C.; Antonucci, E.; Fineschi, S.; Naletto, G.; Nicolini,
G.; Nicolosi, P.; Romoli, M.
2014SPIE.9152E..2QA Altcode:
METIS is part of the science payload of Solar Orbiter. It is a
coronagraph designed to obtain images of the outer solar corona both in
the visible 580-640 nm band and in the UV, in a narrow band centered
around the hydrogen Lyman-α line. We describe the main features of
the procedures to remove signatures due to cosmic rays (CRs) and to
solar energetic particles (SEPs) comparing them with alternatives in
other contexts and in other solar coronagraphic missions. Our analysis
starts from a realistic assessment of the radiation environment where
the instrument is expected to operate, which is characteristic of the
interplanetary space of the inner solar system, but quite unusual for
most solar missions.
---------------------------------------------------------
Title: On the Signatures of Waves and Oscillations in IRIS
Observations
Authors: Fleck, Bernard; Straus, Thomas; De Pontieu, Bart; Leenaarts,
Jorrit; Pereira, Tiago M. D.
2014AAS...22432305F Altcode:
The objective of this study is to explore the signatures of acoustic
waves and oscillations in a variety of magnetic field configurations
in the Sun’s atmosphere using high-resolution spectroscopic
“sit-an-stare” time series obtained with the Interface Region
Imaging Spectrogragh (IRIS) in lines formed in the chromosphere and
lower transition region (C II 1335 & 1336, C I 1352, O I 1356,
Si IV 1394 & 1403 and Mg h and k). The occurrence of oscillations
in the transition region is found to strongly depend on the magnetic
field topology. The Mg h and k lines reveal a particularly complex
spatio-temporal behavior. In an effort to better understand what
physical parameters can be extracted from these lines, we extend our
analysis to synthetic spectra obtained from numerical simulations and
compare the results to observations.
---------------------------------------------------------
Title: The Intensity-Velocity Phase Spectra of Evanescent Oscillations
and Acoustic Sources
Authors: Severino, G.; Straus, T.; Oliviero, M.; Steffen, M.; Fleck, B.
2013SoPh..284..297S Altcode: 2012SoPh..tmp..295S
There are three major issues in modeling solar evanescent oscillations:
the variation of the intensity [I]-velocity [V] phase difference of
p-modes close to the base of photosphere; the existence of a plateau
of negative I-V phase differences below and between the ridges of the
low-frequency p-modes; the explanation of the I-V cross-spectra of
the evanescent oscillations. We present new interpretations for the
first two issues, based on modeling intensity fluctuations taking steep
temperature gradients, opacity, and non-adiabatic cooling into account.
---------------------------------------------------------
Title: On the Effects of the SDO Orbital Motion on the HMI Vector
Magnetic Field Measurements
Authors: Fleck, B.; Centeno, R.; Cheung, M.; Couvidat, S.; Hayashi,
K.; Rezaei, R.; Steiner, O.; Straus, T.
2013enss.confE.145F Altcode:
In a previous study we have investigated the magnetic field diagnostics
potential of SDO/HMI. We have used the output of high-resolution
3D, time-dependent, radiative magneto-hydrodynamics simulations to
calculate Stokes profiles for the Fe I 6173 Å line. From these we
constructed Stokes filtergrams using a representative set of HMI filter
response functions. The magnetic field vector (x,y) and line-of-sight
Doppler velocities V(x,y) were determined from these filtergrams using
a simplified version of the HMI magnetic field processing pipeline,
and the reconstructed magnetic field (x,y) and line-of-sight velocity
V(x,y) were compared to the actual magnetic field (x,y,z) and vertical
velocity V0(x,y,z) in the simulations. The present investigation expands
this analysis to include the effects of the significant orbital motions
of SDO, which, given the limited wavelength range of the HMI filter
profiles, affects the outer wing measurements and therefore might impact
the magnetic field measurements. We find that the effects of the orbital
movement of SDO are noticeable, in particular for the strongest fields
(B > 3 kG) and the maximum wavelength shift of 5.5 km/s (3.5 km/s
orbital movement + 2 km/s solar rotation). Saturation effects for strong
fields (B > 3 kG) are already visible for wavelength shifts of 3.2
km/s (orbital movement, disk center). The measurements of inclination
and vertical velocity are more robust. Compared to other factors of
uncertainty in the inversion of HMI Stokes measurements the orbital
movement is not a major concern or source of error.
---------------------------------------------------------
Title: Acoustic-Gravity Waves in the Solar Atmosphere: Comparing
Hinode/SP Observations with Numerical Simulations
Authors: Fleck, Bernard; Straus, T.; Severino, G.
2012AAS...22020121F Altcode:
We investigate the signatures of acoustic-gravity waves in Hinode/SP
observations and compare them to those found in line spectra synthesized
from high-resolution 3D radiation-hydrodynamics simulations. The
Hinode/SP time series extends over 4 hours, with a cadence of 16 s and a
spatial resolution of 0.16 arcsec/pixel. The observations are compared
to two numerical simulations of the Sun’s surface layers, both
computed with the radiation hydrodynamics code CO<SUP>5</SUP>BOLD. The
higher resolution simulation has a fixed 3D Cartesian grid with 400
x 400 x 300 cells, each of size 14 km x 14 km x 7.5 km, the lower
resolution simulation 200 x 200 x 250 cells, each of size 56 km x 56
km x 21 km. The higher resolution simulation thus covers a cube of 5.6
x 5.6 x 2.3 Mm<SUP>3</SUP>, the lower resolution simulation a cube of
size 11.2 x 11.2 x 5.2 Mm<SUP>3</SUP>. A line-synthesis code, based
on the assumption of local thermodynamic equilibrium (LTE), was fed
with the physical parameters of the simulations to produce synthetic,
two-dimensional spectra of the photospheric lines of Fe 6301/6302 Å
(Hinode/SP), Fe 6173 Å (SDO/ HMI), and Ni 6768 Å (SOHO/MDI). The
resulting Doppler velocity time series are analyzed using Fourier
techniques and compared to the observed Hinode/SP spectra. The
height-dependent energy flux in the simulations is determined in the
acoustic, evanescent and internal gravity wave regime and compared to
energy flux estimates from the Hinode observations and the synthesized
Doppler velocities of the simulations.
---------------------------------------------------------
Title: On The Magnetic-Field Diagnostics Potential of SDO/HMI
Authors: Fleck, Bernard; Hayashi, K.; Rezaei, R.; Vitas, N.; Centeno,
R.; Cheung, M.; Couvidat, S.; Fischer, C.; Steiner, O.; Straus, T.;
Viticchie, B.
2012AAS...22020701F Altcode:
The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO) is designed to study oscillations and the magnetic
field in the solar photosphere. It observes the full solar disk
in the Fe I absorption line at 6173 Å. We use the output of three
high-resolution 3D, time-dependent, radiative magneto-hydrodynamics
simulations (two based on the MURaM code, one on the CO<SUP>5</SUP>BOLD
code) to calculate Stokes profiles for the Fe I 6173 Å line
for snapshots of a sunspot, a plage area and an enhanced network
region. Stokes filtergrams are constructed for the 6 nominal HMI
wavelengths by multiplying the Stokes profiles with a representative
set of HMI filter response functions. The magnetic field vector B(x,y)
and line-of-sight Doppler velocities V(x,y) are determined from these
filtergrams using a simplified version of the HMI magnetic field
processing pipeline. Finally, the reconstructed magnetic field B(x,y)
and line-of-sight velocity V(x,y) are compared to the actual magnetic
field B<SUB>0</SUB>(x,y,z) and vertical velocity V<SUB>0</SUB>(x,y,z)
in the simulations.
---------------------------------------------------------
Title: On the Magnetic-Field Diagnostics Potential of SDO/HMI
Authors: Fleck, B.; Hayashi, K.; Rezaei, R.; Vitas, N.; Centeno,
R.; Cheung, M.; Couvidat, S.; Fischer, C.; Steiner, O.; Straus, T.;
Viticchie, B.
2012decs.confE.104F Altcode:
The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO) is designed to study oscillations and the magnetic
field in the solar photosphere. It observes the full solar disk
in the Fe I absorption line at 6173 Å. We use the output of three
high-resolution 3D, time-dependent, radiative magneto-hydrodynamics
simulations (two based on the MURaM code, one on the CO5BOLD code)
to calculate Stokes profiles Fi(λ,x,y; i=I, V, Q, U) for the Fe I
6173 Å line for snapshots of a sunspot, a plage area and an enhanced
network region. Stokes filtergrams are constructed for the 6 nominal
HMI wavelengths by multiplying the Stokes profiles with a representative
set of HMI filter response functions. The magnetic field vector B(x,y)
and line-of-sight Doppler velocities V(x,y) are determined from these
filtergrams using a simplified version of the HMI magnetic field
processing pipeline. Finally, the reconstructed magnetic field B(x,y)
and line-of-sight velocity V(x,y) are compared to the actual magnetic
field B0(x,y,z) and vertical velocity V0(x,y,z) in the simulations.
---------------------------------------------------------
Title: On the Magnetic-Field Diagnostics Potential of SDO/HMI
Authors: Fleck, B.; Hayashi, K.; Rezaei, R.; Vitas, N.; Centeno, R.;
Couvidat, S.; Fischer, C.; Steiner, O.; Straus, T.; Viticchie, B.
2011sdmi.confE..74F Altcode:
The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO) is designed to study oscillations and the magnetic
field in the solar photosphere. It observes the full solar disk in the
Fe I 6173 absorption line. We use the output of two high-resolution 3D,
time-dependent, radiative magneto-hydrodynamics simulations (one based
on the MURAM code, the other one on the COBOLD code) to calculate
Stokes profiles for the Fe I 6173 line for a snapshot of a plage
region and a snapshot of an enhanced network region. After spatially
degrading the Stokes profiles to HMI resolution, they are multiplied
by a representative set of HMI filter response functions and Stokes
filtergrams are constructed for the 6 nominal HMI wavelengths. The
magnetic field vector and line-of-sight Doppler velocities are
determined from these filtergrams using a simplified version of the HMI
magnetic field processing pipeline. Finally, the reconstructed magnetic
field is compared to the actual magnetic field in the simulation.
---------------------------------------------------------
Title: On the Formation Height of the SDO/HMI Fe 6173 Å Doppler
Signal
Authors: Fleck, B.; Couvidat, S.; Straus, T.
2011SoPh..271...27F Altcode: 2011SoPh..tmp..242F; 2011arXiv1104.5166F; 2011SoPh..tmp..117F;
2011SoPh..tmp..173F
The Helioseismic and Magnetic Imager (HMI) onboard the Solar
Dynamics Observatory (SDO) is designed to study oscillations and the
magnetic field in the solar photosphere. It observes the full solar
disk in the Fe I absorption line at 6173 Å. We use the output of a
high-resolution, 3D, time-dependent, radiation-hydrodynamic simulation
based on the CO<SUP>5</SUP>BOLD code to calculate profiles F(λ,x,y,t)
for the Fe I 6173 Å line. The emerging profiles F(λ,x,y,t) are
multiplied by a representative set of HMI filter-transmission profiles
R<SUB>i</SUB>(λ, 1≤i≤6) and filtergrams I<SUB>i</SUB>(x,y,t;
1≤i≤6) are constructed for six wavelengths. Doppler velocities
V<SUB>HMI</SUB>(x,y,t) are determined from these filtergrams using
a simplified version of the HMI pipeline. The Doppler velocities are
correlated with the original velocities in the simulated atmosphere. The
cross-correlation peaks near 100 km, suggesting that the HMI Doppler
velocity signal is formed rather low in the solar atmosphere. The same
analysis is performed for the SOHO/MDI Ni I line at 6768 Å. The MDI
Doppler signal is formed slightly higher at around 125 km. Taking
into account the limited spatial resolution of the instruments,
the apparent formation height of both the HMI and MDI Doppler signal
increases by 40 to 50 km. We also study how uncertainties in the HMI
filter-transmission profiles affect the calculated velocities.
---------------------------------------------------------
Title: High-frequency Waves in Numerical Simulations of the Solar
Atmosphere
Authors: Fleck, Bernard; Straus, T.; Severino, G.
2011SPD....42.1720F Altcode: 2011BAAS..43S.1720F
We investigate the excitation processes, propagation characteristics,
and energy transport of high-frequency waves in the solar atmosphere
with the help of high-resolution 3D radiation-hydrodynamics
simulations. Time series of synthetic spectra of four photospheric
Fraunhofer lines (Fe 6302, Fe 6301, Fe 6173, Ni 6768) from these
simulations are analyzed in order to evaluate the diagnostic power of
spectroscopic observations.
---------------------------------------------------------
Title: Estimating the Energy Flux of Acoustic-Gravity Waves in the
Solar Atmosphere from SDO/HMI Data
Authors: Fleck, B.; Straus, T.; Jefferies, S.; Scherrer, P.
2010AGUFMSH11A1602F Altcode:
Straus et al. (2008, 2009) demonstrated the existence of internal
gravity waves in the solar atmosphere and showed that they are a
key mediator of mechanical energy in the middle/upper photosphere,
transporting even more energy than high-frequency acoustic waves. Here
we repeat this analysis with data from SDO/HMI, which offers several
distinct advantages, which are particularly relevant for the study
of internal gravity waves (which have long periods and small spatial
scales): excellent image stability over long time intervals, high
spatial resolution, large field-of-view, and good temporal cadence.
---------------------------------------------------------
Title: On the Origin of High-Frequency "Acoustic” Power in
Photospheric and Chromospheric Velocity Power Spectra
Authors: Fleck, Bernard; Straus, T.; Carlsson, M.; Jefferies, S. M.;
Severino, G.; Tarbell, T. D.
2010AAS...21640309F Altcode: 2010BAAS...41..879F
In a recent paper (Fleck et al., 2010) we compared observed Dopplergram
time series from Hinode with results from 3-D numerical simulations
based on the Oslo "Stagger” and CO5BOLD codes. Given the rapid falloff
of atmospheric modulation transfer functions at high frequencies due
to the extended widths of typical velocity response functions, one
would expect the high-frequency tail of Doppler power spectra to drop
significantly below those of actual velocities at the corresponding
heights in the simulations. Surprisingly, our analysis of power spectra
of Doppler shifts of simulated line profiles did not reveal such a
steep falloff at high frequencies. Instead, they are comparable to
(and in some cases even larger than) those of the actual velocities,
making estimates of the energy flux of high frequency acoustic
waves questionable, in particular those that apply atmospheric MTF
corrections. In this work we study the cause of this unexpected
behavior in detail, with particular emphasis on the role of rapidly
changing velocity response functions in a dynamic atmosphere with
strong vertical velocity gradients.
---------------------------------------------------------
Title: High frequency waves in the solar atmosphere?.
Authors: Fleck, B.; Straus, T.; Carlsson, M.; Jefferies, S. M.;
Severino, G.; Tarbell, T. D.
2010MmSAI..81..777F Altcode: 2010arXiv1002.3285F
The present study addresses the following questions: How representative
of the actual velocities in the solar atmosphere are the Doppler
shifts of spectral lines? How reliable is the velocity signal derived
from narrowband filtergrams? How well defined is the height of the
measured Doppler signal? Why do phase difference spectra always pull
to 0<SUP>o</SUP> phase lag at high frequencies? Can we actually observe
high frequency waves (P< 70 s)? What is the atmospheric MTF of high
frequency waves? How reliably can we determine the energy flux of high
frequency waves? We address these questions by comparing observations
obtained with Hinode/NFI with results from two 3D numerical simulations
(Oslo Stagger and CO<SUP>5</SUP>BOLD). Our results suggest that the
observed high frequency Doppler velocity signal is caused by rapid
height variations of the velocity response function in an atmosphere
with strong velocity gradients and cannot be interpreted as evidence of
propagating high frequency acoustic waves. Estimates of the energy flux
of high frequency waves should be treated with caution, in particular
those that apply atmospheric MTF corrections.
---------------------------------------------------------
Title: On the Role of Acoustic-Gravity Waves in the Energetics of
the Solar Atmosphere
Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; McIntosh, S. W.;
Severino, G.; Steffen, M.; Tarbell, T. D.
2009ASPC..415...95S Altcode: 2010arXiv1003.3773S
In a recent paper (Straus et al. 2008) we determined the energy
flux of internal gravity waves in the lower solar atmosphere using
a combination of 3D numerical simulations and observations obtained
with the IBIS instrument operated at the Dunn Solar Telescope and
the Michelson Doppler Imager (MDI) on SOHO. In this paper we extend
these studies using coordinated observations from SOT/NFI and SOT/SP
on Hinode and MDI. The new measurements confirm that gravity waves
are the dominant phenomenon in the quiet middle/upper photosphere and
that they transport more mechanical energy than the high-frequency
(> 5 mHz) acoustic waves, even though we find an acoustic flux 3-5
times larger than the upper limit estimate of Fossum & Carlsson
(2006). It therefore appears justified to reconsider the significance of
(non-M)HD waves for the energy balance of the solar chromosphere.
---------------------------------------------------------
Title: On The Interpretation Of Hinode NFI Filtergrams
Authors: Fleck, Bernard; Straus, T.; Jefferies, S. M.; Severino, G.;
Tarbell, T. D.
2009SPD....40.0927F Altcode:
Phase difference spectra between the velocity signals at two
different heights represent a powerful tool to study the propagation
characteristics of acoustic-gravity waves in the solar atmosphere. In
our efforts to study the dynamics and energetics of these waves we
have acquired high-resolution, high-cadence time series with Hinode
SOT/NFI at two different levels in the Mg b2 or Na D1 lines. The
observed phase spectra between the velocity signals derived from the
"wing" and "core" filtergrams of these lines do not show the expected
behavior. This points to (a) a fundamental lack of understanding of
the propagation characteristics of acoustic waves, which may be more
complex than commonly assumed, or (b) significant difficulties in
interpreting filtergrams taken at fixed wavelengths in the wings of an
absorption line, possibly limiting the diagnostic potential of Doppler
"velocity" measurements from such filtergrams. The present work aims
at disentangling these effects with the help of numerical simulations.
---------------------------------------------------------
Title: High Frequency Acoustic Waves in the Sun's Atmosphere
Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Severino, G.;
Straus, T.; Tarbell, T. D.
2008ESPM...12.2.39F Altcode:
This year marks the 60th anniversary of two pioneering papers by
Schwarzschild (1948) and Biermann (1948), who independently proposed
that acoustic waves generated in the turbulent convection zone play
an important role in the heating of the chromosphere and corona. High
frequency acoustic waves have remained one of the leading contenders
for solving the heating problem of the non-magnetic chromospheres of
the Sun and late-type stars ever since. Earlier attempts to determine
the acoustic energy flux from ground were compromised by atmospheric
seeing, which has its biggest effect on the high frequency parts
of the observed signal. Recently, based on a comparison of TRACE
observations and 1-D simulations, Fossum & Carlsson (2005, 2006)
concluded that high-frequency acoustic waves are not sufficient
to heat the solar chromosphere. The same conclusion was reached by
Carlsson et al. (2007) from an analysis of Hinode SOT/BFI Ca II H and
blue continuum observations. Other authors (e.g. Cuntz et al. 2007;
Wedemeyer-Boehm et al. 2007, Kalkofen 2007), however, questioned
these results for a number of reasons. Because of its limited spatial
resolution and limited sensitivity there are inherent difficulties
when comparing TRACE observations with numerical simulations. Further,
intensity oscillations are difficult to interpret, as they result from
a phase-sensitive mix of temperature and pressure fluctuations, and
non-local radiation transfer effects may complicate the picture even
more. Here we revisit the role of high frequency acoustic waves in the
dynamics and energetics of the Sun's atmosphere using high cadence,
high resolution Doppler velocity measurements obtained with SOT/SP
and SOT/NFI on Hinode.
---------------------------------------------------------
Title: Spatio-Temporal Analysis of Photospheric Turbulent Velocity
Fields Using the Proper Orthogonal Decomposition
Authors: Vecchio, A.; Carbone, V.; Lepreti, F.; Primavera, L.;
Sorriso-Valvo, L.; Straus, T.; Veltri, P.
2008SoPh..251..163V Altcode: 2008SoPh..tmp...40V
The spatio-temporal dynamics of the solar photosphere are studied by
performing a proper orthogonal decomposition (POD) of line-of-sight
velocity fields computed from high-resolution data coming from the
SOHO/MDI instrument. Using this technique, we are able to identify and
characterize the different dynamical regimes acting in the system. All
of the POD modes are characterized by two well-separated peaks in the
frequency spectra. In particular, low-frequency oscillations, with
frequencies in the range 20 - 130 μHz, dominate the most energetic
POD modes (excluding solar rotation) and are characterized by spatial
patterns with typical scales of about 3 Mm. Patterns with larger
typical scales, of about 10 Mm, are dominated by p-mode oscillations
at frequencies of about 3000 μHz. The p-mode properties found by
POD are in agreement with those obtained with the classical Fourier
analysis. The spatial properties of high-energy POD modes suggest
the presence of a strong coupling between low-frequency modes and
turbulent convection.
---------------------------------------------------------
Title: On the Role of Acoustic-gravity Waves in the Energetics of
the Solar Atmosphere
Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; Cauzzi, G.; McIntosh,
S. W.; Reardon, K.; Severino, G.; Steffen, M.; Suter, M.; Tarbell,
T. D.
2008ESPM...12.2.11S Altcode:
We revisit the dynamics and energetics of the solar atmosphere, using a
combination of high-quality observations and 3D numerical simulations
of the overshoot region of compressible convection into the stable
photosphere. We discuss the contribution of acoustic-gravity waves
to the energy balance of the photosphere and low chromosphere. We
demonstrate the presence of propagating internal gravity waves at
low frequencies (< 5mHz). Surprisingly, these waves are found
to be the dominant phenomenon in the quiet middle/upper photosphere
and to transport a significant amount of mechanical energy into the
atmosphere outweighing the contribution of high-frequency (> 5mHz)
acoustic waves by more than an order of magnitude. We compare the
properties of high-frequency waves in the simulations with results
of recent high cadence, high resolution Doppler velocity measurements
obtained with SOT/SP and SOT/NFI on Hinode. Our results seem to be in
conflict with the simple picture of upward propagating sound waves. We
discuss the implications of our findings on the energy flux estimate
at high-frequencies.
---------------------------------------------------------
Title: Velocity and Intensity Power and Cross Spectra in Numerical
Simulations of Solar Convection
Authors: Severino, G.; Straus, T.; Steffen, M.
2008SoPh..251..549S Altcode: 2008SoPh..tmp...54S
Fitting observed power and cross spectra of medium-degree p modes
in velocity (V) and intensity (I) has been widely used for getting
information about the p-mode excitation process and, in particular,
for trying to determine the type and location of the acoustic
sources. Numerical simulations of solar convection allow one to
"observe" velocity and temperature (T, used as proxy for I) fluctuations
in different reference frames. Sampling the oscillations on planes of
constant optical depth (τ-frame) closely corresponds to the observer's
point of view, whereas sampling the oscillations at constant geometrical
height (z-frame) is more appropriate for comparison with predictions
from theoretical models based on Eulerian hydrodynamics. The results of
the analysis in the two frames show significant differences. Considering
the effects introduced on oscillations by the steep temperature gradient
of the photosphere and by the temperature- and pressure-dependent
continuum opacity, we develop a new model for fitting the simulated V
and T power and cross spectra both in the τ- and z-frames and discuss
its merits and limitations.
---------------------------------------------------------
Title: The Energy Flux of Internal Gravity Waves in the Lower Solar
Atmosphere
Authors: Straus, Thomas; Fleck, Bernhard; Jefferies, Stuart M.;
Cauzzi, Gianna; McIntosh, Scott W.; Reardon, Kevin; Severino, Giuseppe;
Steffen, Matthias
2008ApJ...681L.125S Altcode:
Stably stratified fluids, such as stellar and planetary atmospheres,
can support and propagate gravity waves. On Earth these waves,
which can transport energy and momentum over large distances and can
trigger convection, contribute to the formation of our weather and
global climate. Gravity waves also play a pivotal role in planetary
sciences and modern stellar physics. They have also been proposed
as an agent for the heating of stellar atmospheres and coronae, the
exact mechanism behind which is one of the outstanding puzzles in solar
and stellar physics. Using a combination of high-quality observations
and 3D numerical simulations we have the first unambiguous detection
of propagating gravity waves in the Sun's (and hence a stellar)
atmosphere. Moreover, we are able to determine the height dependence of
their energy flux and find that at the base of the Sun's chromosphere it
is around 5 kW m<SUP>-2</SUP>. This amount of energy is comparable to
the radiative losses of the entire chromosphere and points to internal
gravity waves as a key mediator of energy into the solar atmosphere.
---------------------------------------------------------
Title: High Frequency Acoustic Waves in the Sun's Atmosphere
Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Straus, T.;
Tarbell, T. D.
2008AGUSMSP41B..04F Altcode:
This year marks the 60th anniversary of two pioneering papers by
Schwarzschild (1948) and Biermann (1948), who independently proposed
that acoustic waves generated in the turbulent convection zone play
an important role in the heating of the chromosphere and corona. High
frequency acoustic waves have remained one of the leading contenders
for solving the heating problem of the non-magnetic chromospheres of
the Sun and late-type stars ever since. Earlier attempts to determine
the acoustic energy flux from ground were compromised by atmospheric
seeing, which has its biggest effect on the high frequency parts
of the observed signal. Recently, based on a comparison of TRACE
observations and 1-D simulations, Fossum & Carlsson (2005, 2006)
concluded that high-frequency acoustic waves are not sufficient to heat
the solar chromosphere. The same conclusion was reached by Carlsson et
al. (2007) from an analysis of Hinode SOT/BFI Ca II H and blue continuum
observations. Other authors (e.g. Cuntz et al. 2007; Wedemeyer-Boehm
et al. 2007, Kalkofen 2007), however, questioned these results for
a number of reasons. Because of its limited spatial resolution and
limited sensitivity there are inherent difficulties when comparing TRACE
observations with numerical simulations. Further, intensity oscillations
are difficult to interpret, as they result from a phase-sensitive mix of
density, temperature, and pressure fluctuations, and radiation transfer
effects may complicate the picture even more. Here we revisit the role
of high frequency acoustic waves in the Sun's atmosphere using high
cadence, high resolution Doppler velocity measurements obtained with
SOT/SP and SOT/NFI on Hinode.
---------------------------------------------------------
Title: Internal Gravity Waves and their Role in the Energetics of
the Solar Atmosphere
Authors: Fleck, Bernard; Straus, T.; Jefferies, S.; McIntosh, S. W.;
Severino, G.; Steffen, M.
2007AAS...210.2410F Altcode: 2007BAAS...39..130F
Internal gravity waves are believed to be excited by convective
overshoot in the solar atmosphere. We compare the results from numerical
simulations of the overshoot region of compressible convection into a
stable photosphere, with observations of the velocity field at several
heights in the solar atmosphere. We find a consistent picture for the
quiet middle/upper photosphere in which internal gravity waves are the
dominant phenomenon at low frequencies (< 2.5 mHz). We estimate the
contribution of these waves to the energy balance in the photosphere
and low chromosphere.
---------------------------------------------------------
Title: Resonant Oscillation Modes and Background in Realistic
Hydrodynamical Simulations of Solar Surface Convection
Authors: Straus, T.; Severino, G.; Steffen, M.
2006ESASP.617E...4S Altcode: 2006soho...17E...4S
No abstract at ADS
---------------------------------------------------------
Title: SOLARNET-Italian Solar Archive Federation. The First Italian
Virtual Observatory Application
Authors: Volpicelli, C. A.; Antonucci, E.; Cora, A.; Giordano, S.;
Messerotti, M.; Santin, A.; Zlobec, P.; Severino, G.; Oliviero, M.;
DeMarino, I.; Alvino, R.; Straus, T.; Ermolli, I.; Centrone, C.;
Perna, C.; Zuccarello, F.; Romano, P.; Spadaro, D.; Contarino, L.
2006MSAIS...9..129V Altcode:
We describe the implementation of the national project SOLARNET (SOLar
ARchive NETwork) aimed at federating the heterogeneous Italian solar
data archives into a VO (Virtual Observatory) framework as a single
integrated database, and providing users with tools to search and
retrieve specific data sets. It interoperates using the SOAP/XML
Web Services exposed by each single node and managed via a unified
Portal.This project is the first real Italian Virtual Observatory
application using the standard defined by the IVOA (International
Virtual Observatory Alliance) working groups.
---------------------------------------------------------
Title: A model of intensity and velocity power and I-V phase
difference across p-mode line profile based on a forced damped
harmonic oscillator and on the observed coherence spectrum
Authors: Magri, Maria; Oliviero, Maurizio; Severino, Giuseppe;
Straus, Thomas
2001MmSAI..72..511M Altcode:
We develop a simple model, based on a damped harmonic oscillator excited
by a random forcing, with the aim to reproduce the observed trends in
the intensity I and velocity V power and in the I-V phase difference and
coherence spectra. The model accounts for an oscillation mode embedded
in a solar background which is partly correlated to the mode. The
complex vectors I and V and the corresponding power spectra and I-V
phase difference are computed. The observed power spectra and the I-V
phase difference in the frequencies range 2.245 - 2.275 mHz for l = 17
(GONG data) are used as a comparison. We can also reproduce the trend
of the observed coherence. The obtained results are quite stimulating to
understand how the correlated convective background affects the data and
what fraction of the convective background is correlated to the mode.
---------------------------------------------------------
Title: Recent results on the solar photospheric dynamics
Authors: Severino, Giuseppe; Magri, Maria; Oliviero, Maurizio;
Straus, Thomas
2001MmSAI..72..677S Altcode:
The solar photosphere is a relatively small atmospheric layer, that
is a boundary between the convective interior and the optically thin
and magnetic outer atmosphere, where convection overshoots into and
different types of waves are excited and damped. Such a system cannot
be described by a simple dynamical model. Recent progress in the study
of the solar photospheric dynamics has been obtained thanks to the
space-time analysis of the velocity (V) and intensity (I) fluctuations
measured by the GONG, MDI/SOHO and VAMOS experiments. In particular,
it is claimed that the I-V phase differences and coherence can allow
to identify the seismic events which are thought to excite the solar
global oscillations.
---------------------------------------------------------
Title: The photosphere - region of reflection and excitation of
solar oscillations
Authors: Straus, Thomas; Severino, Giuseppe
2001MmSAI..72..533S Altcode:
Two observational facts have enforced the interest in the solar p-mode
background spectrum in the recent past: the opposite asymmetry of the
p-mode profiles in intensity and velocity, and the particular behavior
of the I-V phase difference in the transition from the background to
the p-mode across the line profiles. We give a short review on the
current status of the investigation of the solar background.
---------------------------------------------------------
Title: I-V phase difference and gain analysis of GONG full-disk data
Authors: Oliviero, M.; Severino, G.; Straus, T.; Jefferies, S. M.;
Appourchaux, T.
2000MmSAI..71..999O Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Calibration of VAMOS Magnetic Data
Authors: Vogt, E.; Oliviero, M.; Severino, G.; Straus, T.
1999ESASP.448..405V Altcode: 1999ESPM....9..405V; 1999mfsp.conf..405V
No abstract at ADS
---------------------------------------------------------
Title: Wavelet Analysis of Spatial Coherent Structures in the
Photosphere
Authors: Pietropaolo, E.; Berrilli, F.; Consolini, G.; Smaldone,
L. A.; Straus, T.; Cauzzi, G.; Bruno, R.; Bavassano, B.
1999ESASP.448..343P Altcode: 1999ESPM....9..343P; 1999mfsp.conf..343P
No abstract at ADS
---------------------------------------------------------
Title: Properties of solar granulation cells in quiet regions as
derived from a time series of white light images
Authors: Cauzzi, G.; Consolini, G.; Berrilli, F.; Smaldone, L. A.;
Straus, T.; Bavassano, B.; Bruno, R.; Caccin, B.; Carbone, V.; Egidi,
A.; Ermolli, I.; Florio, A.; Pietropaolo, E.
1998MmSAI..69..647C Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Magneto-Optical Filter in Napoli: Perspectives and Test
Observations
Authors: Moretti, P. F.; Severino, G.; Cauzzi, G.; Reardon, K.;
Straus, T.; Cacciani, A.; Marmolino, C.; Oliviero, M.; Smaldone, L. A.
1997ASSL..225..293M Altcode: 1997scor.proc..293M
An observing station based on the Magneto-Optical-Filter (MOF)
technology is being installed at Osservatorio Astronomico di
Capodimonte, in Napoli. In this paper, the main characteristics and
goals of this new instrument are discussed, and several velocity and
magnetic observations from a test campaign are shown.
---------------------------------------------------------
Title: Dynamics of the solar photosphere. I. Two-dimensional
spectroscopy of mesoscale phenomena.
Authors: Straus, T.; Bonaccini, D.
1997A&A...324..704S Altcode:
We address the "mesogranulation" phenomenon by analyzing a spectral
time series, taken at disk center with a two-dimensional spectroscopy
device and covering a period of 4 hours. This tunable device was
composed by a Fabry-Perot interferometer mounted in tandem with an
Universal Birefringent Filter (UBF). We calculate spatial power spectra,
spatio-temporal k-ω power, phase difference and coherence spectra at
different low photospheric levels, in order to investigate the nature
of the mesoscale phenomena. At the lowest levels, mesostructures
appear as a part of an extended distribution of granular sizes
without further distinction from granulation. Here, the plasma
flows are driven by convection. On the other hand, a different
mesoscale phenomenon emerges at levels as high as approximately
200-300km above τ_5000_=1, at medium spatial (k=~0.5...2Mm^-1^)
and medium temporal (ν=~0.5...1mHz) frequencies. This phenomenon is
distinct from convection by its non-convective phase difference values
({PHI}_v-I_=~-30°, {PHI}_v-v_<0°) and by its different propagation
character (almost horizontal propagation). By these properties, the
mesoscale phenomena in the higher photosphere can be identified as
internal gravity waves in the solar atmosphere.
---------------------------------------------------------
Title: ARTHEMIS: The Archive Project for the IPM and THEMIS
Authors: Reardon, K.; Severino, G.; Cauzzi, G.; Gomez, M. T.; Straus,
T.; Russo, G.; Smaldone, G.; Marmolino, C.
1997ASPC..118..398R Altcode: 1997fasp.conf..398R
We describe the plan for ARTHEMIS, the italian archive for THEMIS, from
the point of view of the prospective users of the archive. This archive
is designed to store the data from the Italian Panoramic Monochromator
(IPM) instrument installed on THEMIS as well as the full-disk images
obtained by the telescope. We break the expected users down into
seven categories: a) prospective IPM users; b) campaign planners; c)
data analysts, d) external collaborators; e) instrument monitors, f)
archival observers; and g) the general public.
---------------------------------------------------------
Title: ARTHEMIS: The archive project for the Italian Panoramic
Monochromator
Authors: Reardon, K.; Severino, G.; Cauzzi, G.; Gomez, M. T.; Straus,
T.; Russo, G.; Smaldone, L. A.; Marmolino, C.
1997MmSAI..68..499R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: k-ω diagrams of the solar atmosphere revisited.
Authors: Deubner, F. -L.; Fleck, B.; Schmitz, F.; Straus, T.
1990AGAb....5...35D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamics of mesogranulation.
Authors: Straus, T.; Deubner, F. -L.
1990AGAb....5...34S Altcode:
No abstract at ADS
