Author name code: tarbell
ADS astronomy entries on 2022-09-14
author:"Tarbell, T."
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Title: Achievements of Hinode in the first eleven years
Authors: Hinode Review Team; Al-Janabi, Khalid; Antolin, Patrick;
Baker, Deborah; Bellot Rubio, Luis R.; Bradley, Louisa; Brooks,
David H.; Centeno, Rebecca; Culhane, J. Leonard; Del Zanna, Giulio;
Doschek, George A.; Fletcher, Lyndsay; Hara, Hirohisa; Harra,
Louise K.; Hillier, Andrew S.; Imada, Shinsuke; Klimchuk, James A.;
Mariska, John T.; Pereira, Tiago M. D.; Reeves, Katharine K.; Sakao,
Taro; Sakurai, Takashi; Shimizu, Toshifumi; Shimojo, Masumi; Shiota,
Daikou; Solanki, Sami K.; Sterling, Alphonse C.; Su, Yingna; Suematsu,
Yoshinori; Tarbell, Theodore D.; Tiwari, Sanjiv K.; Toriumi, Shin;
Ugarte-Urra, Ignacio; Warren, Harry P.; Watanabe, Tetsuya; Young,
Peter R.
Bibcode: 2019PASJ...71R...1H
Altcode:
Hinode is Japan's third solar mission following Hinotori (1981-1982)
and Yohkoh (1991-2001): it was launched on 2006 September 22 and is in
operation currently. Hinode carries three instruments: the Solar Optical
Telescope, the X-Ray Telescope, and the EUV Imaging Spectrometer. These
instruments were built under international collaboration with the
National Aeronautics and Space Administration and the UK Science and
Technology Facilities Council, and its operation has been contributed
to by the European Space Agency and the Norwegian Space Center. After
describing the satellite operations and giving a performance evaluation
of the three instruments, reviews are presented on major scientific
discoveries by Hinode in the first eleven years (one solar cycle long)
of its operation. This review article concludes with future prospects
for solar physics research based on the achievements of Hinode.
Title: The Solar-C_EUVST mission
Authors: Shimizu, Toshifumi; Imada, Shinsuke; Kawate, Tomoko;
Ichimoto, Kiyoshi; Suematsu, Yoshinori; Hara, Hirohisa; Katsukawa,
Yukio; Kubo, Masahito; Toriumi, Shin; Watanabe, Tetsuya; Yokoyama,
Takaaki; Korendyke, Clarence M.; Warren, Harry P.; Tarbell, Ted; De
Pontieu, Bart; Teriaca, Luca; Schühle, Udo H.; Solanki, Sami; Harra,
Louise K.; Matthews, Sarah; Fludra, A.; Auchère, F.; Andretta, V.;
Naletto, G.; Zhukov, A.
Bibcode: 2019SPIE11118E..07S
Altcode:
Solar-C EUVST (EUV High-Throughput Spectroscopic Telescope) is a
solar physics mission concept that was selected as a candidate for
JAXA competitive M-class missions in July 2018. The onboard science
instrument, EUVST, is an EUV spectrometer with slit-jaw imaging
system that will simultaneously observe the solar atmosphere from the
photosphere/chromosphere up to the corona with seamless temperature
coverage, high spatial resolution, and high throughput for the first
time. The mission is designed to provide a conclusive answer to the
most fundamental questions in solar physics: how fundamental processes
lead to the formation of the solar atmosphere and the solar wind, and
how the solar atmosphere becomes unstable, releasing the energy that
drives solar flares and eruptions. The entire instrument structure
and the primary mirror assembly with scanning and tip-tilt fine
pointing capability for the EUVST are being developed in Japan, with
spectrograph and slit-jaw imaging hardware and science contributions
from US and European countries. The mission will be launched and
installed in a sun-synchronous polar orbit by a JAXA Epsilon vehicle in
2025. ISAS/JAXA coordinates the conceptual study activities during the
current mission definition phase in collaboration with NAOJ and other
universities. The team is currently working towards the JAXA final
down-selection expected at the end of 2019, with strong support from
US and European colleagues. The paper provides an overall description
of the mission concept, key technologies, and the latest status.
Title: Multi-component Decomposition of Astronomical Spectra by
Compressed Sensing
Authors: Cheung, Mark C. M.; De Pontieu, Bart; Martínez-Sykora,
Juan; Testa, Paola; Winebarger, Amy R.; Daw, Adrian; Hansteen, Viggo;
Antolin, Patrick; Tarbell, Theodore D.; Wuelser, Jean-Pierre; Young,
Peter; MUSE Team
Bibcode: 2019ApJ...882...13C
Altcode: 2019arXiv190203890C
The signal measured by an astronomical spectrometer may be due to
radiation from a multi-component mixture of plasmas with a range of
physical properties (e.g., temperature, Doppler velocity). Confusion
between multiple components may be exacerbated if the spectrometer
sensor is illuminated by overlapping spectra dispersed from different
slits, with each slit being exposed to radiation from a different
portion of an extended astrophysical object. We use a compressed sensing
method to robustly retrieve the different components. This method can
be adopted for a variety of spectrometer configurations, including
single-slit, multi-slit (e.g., the proposed MUlti-slit Solar Explorer
mission), and slot spectrometers (which produce overlappograms).
Title: Multi-component Decomposition of Astronomical Spectra by
Compressed Sensing
Authors: Cheung, Mark; De Pontieu, Bart; Martinez-Sykora, Juan; Testa,
Paola; Winebarger, Amy R.; Daw, Adrian N.; Hansteen, Viggo; Antolin,
Patrick; Tarbell, Theodore D.; Wuelser, Jean-Pierre; Young, Peter R.
Bibcode: 2019AAS...23411603C
Altcode:
The signal measured by an astronomical spectrometer may be due to
radiation from a multi-component mixture of plasmas with a range of
physical properties (e.g. temperature, Doppler velocity). Confusion
between multiple components may be exacerbated if the spectrometer
sensor is illuminated by overlapping spectra dispersed from different
slits, with each slit being exposed to radiation from a different
portion of an extended astrophysical object. We use a compressed sensing
method to robustly retrieve the different components. This method can
be adopted for a variety of spectrometer configurations, including
single-slit, multi-slit (e.g., the proposed MUlti-slit Solar Explorer
mission; MUSE) and slot spectrometers (which produce overlappograms).
Title: Evidence of Twisting and Mixed-polarity Solar Photospheric
Magnetic Field in Large Penumbral Jets: IRIS and Hinode Observations
Authors: Tiwari, Sanjiv K.; Moore, Ronald L.; De Pontieu, Bart;
Tarbell, Theodore D.; Panesar, Navdeep K.; Winebarger, Amy R.;
Sterling, Alphonse C.
Bibcode: 2018ApJ...869..147T
Altcode: 2018arXiv181109554T
A recent study using Hinode (Solar Optical Telescope/Filtergraph
[SOT/FG]) data of a sunspot revealed some unusually large penumbral
jets that often repeatedly occurred at the same locations in the
penumbra, namely, at the tail of a penumbral filament or where the
tails of multiple penumbral filaments converged. These locations had
obvious photospheric mixed-polarity magnetic flux in Na I 5896 Stokes-V
images obtained with SOT/FG. Several other recent investigations have
found that extreme-ultraviolet (EUV)/X-ray coronal jets in quiet-Sun
regions (QRs), in coronal holes (CHs), and near active regions (ARs)
have obvious mixed-polarity fluxes at their base, and that magnetic
flux cancellation prepares and triggers a minifilament flux-rope
eruption that drives the jet. Typical QR, CH, and AR coronal jets are
up to 100 times bigger than large penumbral jets, and in EUV/X-ray
images they show a clear twisting motion in their spires. Here,
using Interface Region Imaging Spectrograph (IRIS) Mg II k λ2796 SJ
images and spectra in the penumbrae of two sunspots, we characterize
large penumbral jets. We find redshift and blueshift next to each
other across several large penumbral jets, and we interpret these as
untwisting of the magnetic field in the jet spire. Using Hinode/SOT
(FG and SP) data, we also find mixed-polarity magnetic flux at the
base of these jets. Because large penumbral jets have a mixed-polarity
field at their base and have a twisting motion in their spires, they
might be driven the same way as QR, CH, and AR coronal jets.
Title: Instrument Calibration of the Interface Region Imaging
Spectrograph (IRIS) Mission
Authors: Wülser, J. -P.; Jaeggli, S.; De Pontieu, B.; Tarbell,
T.; Boerner, P.; Freeland, S.; Liu, W.; Timmons, R.; Brannon, S.;
Kankelborg, C.; Madsen, C.; McKillop, S.; Prchlik, J.; Saar, S.;
Schanche, N.; Testa, P.; Bryans, P.; Wiesmann, M.
Bibcode: 2018SoPh..293..149W
Altcode:
The Interface Region Imaging Spectrograph (IRIS) is a NASA small
explorer mission that provides high-resolution spectra and images of
the Sun in the 133 - 141 nm and 278 - 283 nm wavelength bands. The
IRIS data are archived in calibrated form and made available to the
public within seven days of observing. The calibrations applied to
the data include dark correction, scattered light and background
correction, flat fielding, geometric distortion correction, and
wavelength calibration. In addition, the IRIS team has calibrated the
IRIS absolute throughput as a function of wavelength and has been
tracking throughput changes over the course of the mission. As a
resource for the IRIS data user, this article describes the details
of these calibrations as they have evolved over the first few years
of the mission. References to online documentation provide access to
additional information and future updates.
Title: Motions in Prominence Barbs Observed on the Solar Limb
Authors: Kucera, T. A.; Ofman, L.; Tarbell, T. D.
Bibcode: 2018ApJ...859..121K
Altcode:
We analyze and discuss an example of prominence barbs observed on the
limb on 2016 January 7 by the Hinode/Solar Optical Telescope in Ca
II and Hα, the Interface Region Imaging Spectrograph, with slit jaw
images and Mg II spectral data, and the Solar Dynamics Observatory’s
Atmospheric Imaging Assembly. In the recent literature there has
been a debate concerning whether these features, sometimes referred
to as “tornadoes,” are rotating. Our data analysis provides no
evidence for systematic rotation in the barbs. We do find line-of-sight
motions in the barbs that vary with location and time. We also discuss
observations of features moving along the barbs. These moving features
are elongated parallel to the solar limb and tend to come in clusters
of features moving along the same or similar paths in the plane of
the sky during a period of 10 minutes to an hour, moving toward or
away from the limb. The motion may have a component along the line
of sight as well. The spectral data indicate that the features are
Doppler shifted. We discuss possible explanations for these features.
Title: An Innovative Approach to a High Resolution Coronal Imager
(T-07): MUSE, the Multi-Slit Solar Explorer
Authors: Tarbell, Theodore D.; De Pontieu, Bart
Bibcode: 2018tess.conf41004T
Altcode:
The Next Generation Solar Physics Mission Science Objectives Team
recommended three instruments flying in space simultaneously: a
spectrometer with wide temperature coverage (T-09), a high resolution
coronal imager (T-07), and a photospheric and chromospheric magnetograph
and spectrograph (T-01,4,5). The coronal imager was inspired by the
Hi-C rocket payload, whose successful flight in 2012 gave us a new
view of the corona at resolution approximately 4 times higher (linear
dimension) than AIA. For example, it showed tantalizing evidence of
coronal heating by braiding of field lines. LMSAL and SAO have designed
a payload that goes beyond the basic requirements for T-07 by combining
an imager like Hi-C with a novel multi-slit EUV spectrograph that
obtains complete line profiles in three coronal temperature ranges over
an extended field-of-view (FOV). This payload is MUSE, the Multi-Slit
Solar Explorer, a Small Explorer mission recently selected by NASA
for a Phase A study, which could lead to a launch in 2022. MUSE will
provide unprecendented observations of the dynamics of the corona and
transition region to illuminate the physical processes that heat the
multi-million degree solar corona, accelerate the solar wind and drive
solar activity (CMEs and flares). Using multi-slit coronal spectroscopy
MUSE will exploit a 100x improvement in spectral raster cadence to
reveal temperatures, velocities and non-thermal processes over a wide
temperature range to diagnose physical processes that remain invisible
to current or planned instruments. MUSE will obtain simultaneous EUV
spectra and images with the highest resolution in space (1/3 arcsec)
and time (1-4 s) ever achieved for the transition region and corona,
along 35 slits over a FOV similar to that of IRIS, and a larger context
imager FOV. The MUSE science investigation will exploit recent advances
in numerical modeling and build on the success of IRIS by combining
numerical modeling with a uniquely capable observatory. The MUSE
consortium is led by LMSAL and includes SAO, MSU, ITA Oslo, Stanford,
ARC, GSFC, MSFC and other institutions.
Title: Motions in Prominence Barbs Observed on the Solar Limb
Authors: Kucera, Therese Ann; Ofman, Leon; Tarbell, Theodore D.
Bibcode: 2018tess.conf21059K
Altcode:
We analyze and discuss an example of prominence barbs observed on the
Title: Observations of Large Penumbral Jets from IRIS and Hinode
Authors: Tiwari, Sanjiv K.; Moore, Ronald Lee; De Pontieu, Bart;
Tarbell, Theodore D.; Panesar, Navdeep Kaur; Winebarger, Amy R.;
Sterling, Alphonse C.
Bibcode: 2018tess.conf40807T
Altcode:
Recent observations from Hinode (SOT/FG) revealed the presence of
large penumbral jets (widths ≥ 500 km, larger than normal penumbral
microjets, which have widths < 400 km) repeatedly occurring at
the same locations in a sunspot penumbra, at the tail of a penumbral
filament or where the tails of several penumbral filaments apparently
converge (Tiwari et al. 2016, ApJ). These locations were observed
to have mixed-polarity flux in Stokes-V images from SOT/FG. Large
penumbral jets displayed direct signatures in AIA 1600, 304, 171,
and 193 channels; thus they were heated to at least transition region
temperatures. Because large jets could not be detected in AIA 94 Å,
whether they had any coronal-temperature plasma remains unclear. In
the present work, for another sunspot, we use IRIS Mg II k 2796
slit jaw images and spectra and magnetograms from Hinode SOT/FG and
SOT/SP to examine: whether penumbral jets spin, similar to spicules
and coronal jets in the quiet Sun and coronal holes; whether they stem
from mixed-polarity flux; and whether they produce discernible coronal
emission, especially in AIA 94 Å images.
Title: MUSE, the Multi-Slit Solar Explorer
Authors: Lemen, J. R.; Tarbell, T. D.; De Pontieu, B.; Wuelser, J. P.
Bibcode: 2017AGUFMSH51B2494L
Altcode:
The Multi-Slit Solar Explorer (MUSE) has been selected for a Phase A
study for the NASA Heliophysics Small Explorer program. The science
objective of MUSE is to make high spatial and temporal resolution
imaging and spectral observations of the solar corona and transition
region in order to probe the mechanisms responsible for energy release
in the corona and understand the dynamics of the solar atmosphere. The
physical processes are responsible for heating the corona, accelerating
the solar wind, and the rapid release of energy in CMEs and flares. The
observations will be tightly coupled to state-of-the-art numerical
modeling to provide significantly improved estimates for understanding
and anticipating space weather. MUSE contains two instruments:
an EUV spectrograph and an EUV context imager. Both have similar
spatial resolutions and leverage extensive heritage from previous
high-resolution instruments such as IRIS and the HiC rocket payload. The
MUSE spectrograph employs a novel multi-slit design that enables a
100x improvement in spectral scanning rates, which will reveal crucial
information about the dynamics (e.g., temperature, velocities) of the
physical processes that are not observable with current instruments. The
MUSE investigation builds on the success of IRIS by combining numerical
modeling with a uniquely capable observatory: MUSE will obtain EUV
spectra and images with the highest resolution in space (1/3 arcsec) and
time (1-4 s) ever achieved for the transition region and corona, along
35 slits and a large context FOV simultaneously. The MUSE consortium
includes LMSAL, SAO, Stanford, ARC, HAO, GSFC, MSFC, MSU, and ITA Oslo.
Title: A New Approach to Observing Coronal Dynamics: MUSE, the
Multi-Slit Solar Explorer
Authors: Tarbell, T. D.
Bibcode: 2017AGUFMSH41C..08T
Altcode:
The Multi-Slit Solar Explorer is a Small Explorer mission recently
selected for a Phase A study, which could lead to a launch in 2022. It
will provide unprecendented observations of the dynamics of the corona
and transition region using both conventional and novel spectral imaging
techniques. The physical processes that heat the multi-million degree
solar corona, accelerate the solar wind and drive solar activity (CMEs
and flares) remain poorly known. A breakthrough in these areas can only
come from radically innovative instrumentation and state-of-the-art
numerical modeling and will lead to better understanding of space
weather origins. MUSE's multi-slit coronal spectroscopy will exploit a
100x improvement in spectral raster cadence to fill a crucial gap in
our knowledge of Sun-Earth connections; it will reveal temperatures,
velocities and non-thermal processes over a wide temperature range to
diagnose physical processes that remain invisible to current or planned
instruments. MUSE will contain two instruments: an EUV spectrograph (SG)
and EUV context imager (CI). Both have similar spatial resolution and
leverage extensive heritage from previous high-resolution instruments
such as IRIS and the HiC rocket payload. The MUSE investigation will
build on the success of IRIS by combining numerical modeling with a
uniquely capable observatory: MUSE will obtain EUV spectra and images
with the highest resolution in space (1/3 arcsec) and time (1-4 s)
ever achieved for the transition region and corona, along 35 slits
and a large context FOV simultaneously. The MUSE consortium includes
LMSAL, SAO, Stanford, ARC, HAO, GSFC, MSFC, MSU, ITA Oslo and other
institutions.
Title: MUSE: the Multi-Slit Solar Explorer
Authors: Tarbell, Theodore D.; De Pontieu, Bart
Bibcode: 2017SPD....4811008T
Altcode:
The Multi-Slit Solar Explorer is a proposed Small Explorer mission
for studying the dynamics of the corona and transition region
using both conventional and novel spectral imaging techniques. The
physical processes that heat the multi-million degree solar corona,
accelerate the solar wind and drive solar activity (CMEs and flares)
remain poorly known. A breakthrough in these areas can only come
from radically innovative instrumentation and state-of-the-art
numerical modeling and will lead to better understanding of space
weather origins. MUSE’s multi-slit coronal spectroscopy will use a
100x improvement in spectral raster cadence to fill a crucial gap in
our knowledge of Sun-Earth connections; it will reveal temperatures,
velocities and non-thermal processes over a wide temperature range to
diagnose physical processes that remain invisible to current or planned
instruments. MUSE will contain two instruments: an EUV spectrograph (SG)
and EUV context imager (CI). Both have similar spatial resolution and
leverage extensive heritage from previous high-resolution instruments
such as IRIS and the HiC rocket payload. The MUSE investigation will
build on the success of IRIS by combining numerical modeling with a
uniquely capable observatory: MUSE will obtain EUV spectra and images
with the highest resolution in space (1/3 arcsec) and time (1-4 s)
ever achieved for the transition region and corona, along 35 slits
and a large context FOV simultaneously. The MUSE consortium includes
LMSAL, SAO, Stanford, ARC, HAO, GSFC, MSFC, MSU, ITA Oslo and other
institutions.
Title: Evidence from IRIS that Sunspot Large Penumbral Jets Spin
Authors: Tiwari, Sanjiv K.; Moore, Ronald L.; De Pontieu, Bart;
Tarbell, Theodore D.; Panesar, Navdeep K.; Winebarger, Amy; Sterling,
Alphonse C.
Bibcode: 2017SPD....4810506T
Altcode:
Recent observations from {\it Hinode} (SOT/FG) revealed the presence of
large penumbral jets (widths $\ge$500 km, larger than normal penumbral
microjets, which have widths $<$ 400 km) repeatedly occurring at the
same locations in a sunspot penumbra, at the tail of a filament or where
the tails of several penumbral filaments apparently converge (Tiwari et
al. 2016, ApJ). These locations were observed to have mixed-polarity
flux in Stokes-V images from SOT/FG. Large penumbral jets displayed
direct signatures in AIA 1600, 304, 171, and 193 channels; thus they
were heated to at least transition region temperatures. Because
large jets could not be detected in AIA 94 \AA, whether they had
any coronal-temperature plasma remains unclear. In the present work,
for another sunspot, we use IRIS Mg II k 2796 Å slit jaw images and
spectra and magnetograms from Hinode SOT/FG and SOT/SP to examine:
whether penumbral jets spin, similar to spicules and coronal jets in the
quiet Sun and coronal holes; whether they stem from mixed-polarity flux;
and whether they produce discernible coronal emission, especially in
AIA 94 Å images. The few large penumbral jets for which we have IRIS
spectra show evidence of spin. If these have mixed-polarity at their
base, then they might be driven the same way as coronal jets and CMEs.
Title: An innovative browser-based data exploration tool with
simultaneous scrolling in time and wavelength domains
Authors: Slater, Gregory L.; Schiff, David; De Pontieu, Bart; Tarbell,
Theodore D.; Freeland, Samuel L.
Bibcode: 2017SPD....4810624S
Altcode:
We present Cruiser, a new web tool for the precision interactive
blending of image series across time and wavelength domains. Scrolling
in two dimensions enables discovery and investigation of similarities
and differences in structure and evolution across multiple
wavelengths. Cruiser works in the latest versions of standards compliant
browsers on both desktop and IOS platforms. Co-aligned data cubes
have been generated for AIA, IRIS, and Hinode SOT FG, and image data
from additional instruments, both space-based and ground-based, can be
data sources. The tool has several movie playing and image adjustment
controls which will be described in the poster and demonstrated on a
MacOS notebook and iPad.
Title: MHD Waves at Umbral-Penumbral Boundary Observed with
Hinode/SOT-SP and SDO/HMI
Authors: Norton, A. A.; Tarbell, T. D.; Scherrer, P. H.; Baldner, C. S.
Bibcode: 2016usc..confE.114N
Altcode:
The conversion of p-modes and other perturbations in the near-surface
layers into MHD waves that can propagate along and across magnetic field
lines is a topic of interest for energy transport. The photospheric
signatures of MHD waves are weak due to low amplitudes at the
beta=1 equipartion level where mode-conversion occurs. We report on
oscillations observed with Hinode SOT/SP and HMI in which we have time
series for sunspots 12186 (11.10.2014) and 12434 (17.10.2015). In
the Milne-Eddington inversion results from SP, oscillations in the
inclination angle and velocity are found at the umbral-penumbral
boundary with 5 minute periods. HMI data also shows distinct
umbral-penumbral boundary oscillations consistent with the SP data. We
discuss surface versus body modes that might explain these observations.
Title: Hinode SOT Images Coaligned with IRIS Level 2 Data Products
Authors: Tarbell, Theodore D.
Bibcode: 2016SPD....4710402T
Altcode:
We have produced new data products consisting of HInode SOT images
coaligned with simultaneous observations by IRIS. Cross-correlation
between SOT Filtergraph images and similar SDO wavelength bands provides
accurate pointing coordinates for nearly all SOT images, correcting
for the solar flows followed by the SOT correlation tracker. Data
from all of 2014 and 2015 and part of 2013 have been processed by now
and verification of the data products is ongoing. The cubes of SOT
images are created in IRIS level 2 data format and can be read using
IRIS software tools. In addition, the SOT cubes can be studied using
CRISPEX along with the corresponding IRIS Level 3 data. Work has begun
to process time series of SOT Spectro-Polarimeter data into cubes of
images that can be studied the same way. Examples of some datasets
from IHOPs, both FG and SP, will be shown and instructions given for
accessing and viewing the available datasets.
Title: Motions in Prominence Barbs as observed by Hinode/SOT and IRIS
Authors: Kucera, Therese A.; Ofman, Leon; Tarbell, Theodore D.
Bibcode: 2016SPD....47.0316K
Altcode:
We discuss observations of prominence barb dynamics as observed by
Hinode/SOT and IRIS. Prominence barbs extend outwards to the side of the
main prominence spine and downwards towards the chromosphere. Their
properties, including the structure of their magnetic field and
the nature of the motions observed in them are a subject of current
debate. We use a combination of high cadence, high resolution imaging,
H-alpha Doppler, and Mg II line profile data to analyze and understand
waves and flows in barbs and discuss their ramifications in terms of
a model of the barb magnetic field as collection of dipped field lines.
Title: Comparing Dynamics in Eruptive and Non-Eruptive Flares
Authors: Nitta, Nariaki; Tarbell, Theodore D.; Slater, Gregory L.;
Frank, Zoe Anne
Bibcode: 2016SPD....47.0620N
Altcode:
Close comparison of EUV and coronagraph data suggests that there may
not be clear distinction between eruptive and non-eruptive flares as
far as the coronal and chromospheric signatures are concerned. Here we
define eruptive and non-eruptive flares in terms of the presence and
absence of the associated coronal mass ejection (CME). We have studied
several flares in both categories using Hinode/SOT and IRIS data. The
pointing of the Hinode/SOT data has been updated by correlating
them with AIA 1700 A images. We show our initial results about how
the flare development compares in eruptive and non-eruptive flares,
including the reconnection rate as derived from the magnetic field
swept over by flare ribbons (in SOT Ca images), and the line-of-sight
velocities at different locations and temperatures (in IRIS spectral
data). We also discuss large-scale disturbances and related CMEs in
SDO/AIA and SOHO/LASCO data as context information.
Title: Amplitudes of MHD Waves in Sunspots
Authors: Norton, Aimee Ann; Cally, Paul; Baldner, Charles; Kleint,
Lucia; Tarbell, Theodore D.; De Pontieu, Bart; Scherrer, Philip H.;
Rajaguru, Paul
Bibcode: 2016SPD....47.1009N
Altcode:
The conversion of p-modes into MHD waves by strong magnetic fields
occurs mainly in the sub-photospheric layers. The photospheric
signatures of MHD waves are weak due to low amplitudes at the beta=1
equipartion level where mode-conversion occurs. We report on small
amplitude oscillations observed in the photosphere with Hinode SOT/SP
in which we analyze time series for sunspots ARs 12186 (11.10.2014)
and 12434 (17.10.2015). No significant magnetic field oscillations
are recovered in the umbra or penumbra in the ME inversion. However,
periodicities in the inclination angle are found at the umbral/penumbral
boundary with 5 minute periods. Upward propagating waves are indicated
in the intensity signals correlated between HMI and AIA at different
heights. We compare SP results with the oscillations observed in HMI
data. Simultaneous IRIS data shows transition region brightening above
the umbral core.
Title: Internetwork Chromospheric Bright Grains Observed With IRIS
and SST
Authors: Martínez-Sykora, Juan; Rouppe van der Voort, Luc; Carlsson,
Mats; De Pontieu, Bart; Pereira, Tiago M. D.; Boerner, Paul; Hurlburt,
Neal; Kleint, Lucia; Lemen, James; Tarbell, Ted D.; Title, Alan;
Wuelser, Jean-Pierre; Hansteen, Viggo H.; Golub, Leon; McKillop, Sean;
Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Jaeggli,
Sarah; Kankelborg, Charles
Bibcode: 2015ApJ...803...44M
Altcode: 2015arXiv150203490M
The Interface Region Imaging Spectrograph (IRIS) reveals small-scale
rapid brightenings in the form of bright grains all over coronal holes
and the quiet Sun. These bright grains are seen with the IRIS 1330,
1400, and 2796 Å slit-jaw filters. We combine coordinated observations
with IRIS and from the ground with the Swedish 1 m Solar Telescope
(SST) which allows us to have chromospheric (Ca ii 8542 Å, Ca ii H
3968 Å, Hα, and Mg ii k 2796 Å) and transition region (C ii 1334 Å,
Si iv 1403 Å) spectral imaging, and single-wavelength Stokes maps
in Fe i 6302 Å at high spatial (0\buildrel{\prime\prime}\over{.}
33), temporal, and spectral resolution. We conclude that the IRIS
slit-jaw grains are the counterpart of so-called acoustic grains,
i.e., resulting from chromospheric acoustic waves in a non-magnetic
environment. We compare slit-jaw images (SJIs) with spectra from the
IRIS spectrograph. We conclude that the grain intensity in the 2796
Å slit-jaw filter comes from both the Mg ii k core and wings. The
signal in the C ii and Si iv lines is too weak to explain the presence
of grains in the 1300 and 1400 Å SJIs and we conclude that the grain
signal in these passbands comes mostly from the continuum. Although
weak, the characteristic shock signatures of acoustic grains can often
be detected in IRIS C ii spectra. For some grains, a spectral signature
can be found in IRIS Si iv. This suggests that upward propagating
acoustic waves sometimes reach all the way up to the transition region.
Title: Homologous Helical Jets: Observations By IRIS, SDO, and Hinode
and Magnetic Modeling With Data-Driven Simulations
Authors: Cheung, Mark C. M.; De Pontieu, B.; Tarbell, T. D.; Fu, Y.;
Tian, H.; Testa, P.; Reeves, K. K.; Martínez-Sykora, J.; Boerner,
P.; Wülser, J. P.; Lemen, J.; Title, A. M.; Hurlburt, N.; Kleint,
L.; Kankelborg, C.; Jaeggli, S.; Golub, L.; McKillop, S.; Saar, S.;
Carlsson, M.; Hansteen, V.
Bibcode: 2015ApJ...801...83C
Altcode: 2015arXiv150101593C
We report on observations of recurrent jets by instruments on board
the Interface Region Imaging Spectrograph, Solar Dynamics Observatory
(SDO), and Hinode spacecraft. Over a 4 hr period on 2013 July 21,
recurrent coronal jets were observed to emanate from NOAA Active Region
11793. Far-ultraviolet spectra probing plasma at transition region
temperatures show evidence of oppositely directed flows with components
reaching Doppler velocities of ±100 km s-1. Raster Doppler
maps using a Si iv transition region line show all four jets to have
helical motion of the same sense. Simultaneous observations of the
region by SDO and Hinode show that the jets emanate from a source
region comprising a pore embedded in the interior of a supergranule. The
parasitic pore has opposite polarity flux compared to the surrounding
network field. This leads to a spine-fan magnetic topology in the
coronal field that is amenable to jet formation. Time-dependent
data-driven simulations are used to investigate the underlying drivers
for the jets. These numerical experiments show that the emergence of
current-carrying magnetic field in the vicinity of the pore supplies
the magnetic twist needed for recurrent helical jet formation.
Title: Homologous Helical Jets: Observations by IRIS, SDO and Hinode
and Data-Driven Simulations
Authors: Cheung, C. M. M.; De Pontieu, B.; Tarbell, T. D.; Fu, Y.
Bibcode: 2014AGUFMSH53D..05C
Altcode:
We report on observations of recurrent jets by instruments onboard
the Interface Region Imaging Spectrograph (IRIS), Solar Dynamics
Observatory (SDO) and Hinode spacecrafts. Over a 4-hour period on
July 21st 2013, recurrent coronal jets were observed to emanate from
NOAA Active Region 11793. In more than one instance, double-peaked
FUV spectra probing plasma at transition region temperatures show
evidence of oppositely directed (Doppler) outflows exceeding +/- 100
km/s. Raster Doppler maps using a Si IV transition region line shows
all four jets to have helical motion of the same sense. Time-dependent
data-driven simulations are used to investigate the underlying drivers
for the jets. These numerical experiments show that the emergence of
current-carrying magnetic field in the vicinity of a pore supplies
the magnetic twist needed for recurrent helical jet formation.
Title: Hot explosions in the cool atmosphere of the Sun
Authors: Peter, H.; Tian, H.; Curdt, W.; Schmit, D.; Innes, D.;
De Pontieu, B.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.;
Tarbell, T. D.; Wuelser, J. P.; Martínez-Sykora, Juan; Kleint,
L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.;
Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V.
Bibcode: 2014Sci...346C.315P
Altcode: 2014arXiv1410.5842P
The solar atmosphere was traditionally represented with a simple
one-dimensional model. Over the past few decades, this paradigm shifted
for the chromosphere and corona that constitute the outer atmosphere,
which is now considered a dynamic structured envelope. Recent
observations by the Interface Region Imaging Spectrograph (IRIS) reveal
that it is difficult to determine what is up and down, even in the cool
6000-kelvin photosphere just above the solar surface: This region hosts
pockets of hot plasma transiently heated to almost 100,000 kelvin. The
energy to heat and accelerate the plasma requires a considerable
fraction of the energy from flares, the largest solar disruptions. These
IRIS observations not only confirm that the photosphere is more complex
than conventionally thought, but also provide insight into the energy
conversion in the process of magnetic reconnection.
Title: The unresolved fine structure resolved: IRIS observations of
the solar transition region
Authors: Hansteen, V.; De Pontieu, B.; Carlsson, M.; Lemen, J.; Title,
A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Pereira,
T. M. D.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar,
S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.;
Martínez-Sykora, J.
Bibcode: 2014Sci...346E.315H
Altcode: 2014arXiv1412.3611H
The heating of the outer solar atmospheric layers, i.e., the transition
region and corona, to high temperatures is a long-standing problem
in solar (and stellar) physics. Solutions have been hampered by an
incomplete understanding of the magnetically controlled structure of
these regions. The high spatial and temporal resolution observations
with the Interface Region Imaging Spectrograph (IRIS) at the solar
limb reveal a plethora of short, low-lying loops or loop segments
at transition-region temperatures that vary rapidly, on the time
scales of minutes. We argue that the existence of these loops solves
a long-standing observational mystery. At the same time, based on
comparison with numerical models, this detection sheds light on a
critical piece of the coronal heating puzzle.
Title: Evidence of nonthermal particles in coronal loops heated
impulsively by nanoflares
Authors: Testa, P.; De Pontieu, B.; Allred, J.; Carlsson, M.; Reale,
F.; Daw, A.; Hansteen, V.; Martinez-Sykora, J.; Liu, W.; DeLuca, E. E.;
Golub, L.; McKillop, S.; Reeves, K.; Saar, S.; Tian, H.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kleint, L.; Kankelborg, C.; Jaeggli, S.
Bibcode: 2014Sci...346B.315T
Altcode: 2014arXiv1410.6130T
The physical processes causing energy exchange between the Sun’s
hot corona and its cool lower atmosphere remain poorly understood. The
chromosphere and transition region (TR) form an interface region between
the surface and the corona that is highly sensitive to the coronal
heating mechanism. High-resolution observations with the Interface
Region Imaging Spectrograph (IRIS) reveal rapid variability (~20 to
60 seconds) of intensity and velocity on small spatial scales (≲500
kilometers) at the footpoints of hot and dynamic coronal loops. The
observations are consistent with numerical simulations of heating by
beams of nonthermal electrons, which are generated in small impulsive
(≲30 seconds) heating events called “coronal nanoflares.” The
accelerated electrons deposit a sizable fraction of their energy
(≲1025 erg) in the chromosphere and TR. Our analysis
provides tight constraints on the properties of such electron beams
and new diagnostics for their presence in the nonflaring corona.
Title: Prevalence of small-scale jets from the networks of the solar
transition region and chromosphere
Authors: Tian, H.; DeLuca, E. E.; Cranmer, S. R.; De Pontieu, B.;
Peter, H.; Martínez-Sykora, J.; Golub, L.; McKillop, S.; Reeves,
K. K.; Miralles, M. P.; McCauley, P.; Saar, S.; Testa, P.; Weber,
M.; Murphy, N.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.;
Tarbell, T. D.; Wuelser, J. P.; Kleint, L.; Kankelborg, C.; Jaeggli,
S.; Carlsson, M.; Hansteen, V.; McIntosh, S. W.
Bibcode: 2014Sci...346A.315T
Altcode: 2014arXiv1410.6143T
As the interface between the Sun’s photosphere and corona, the
chromosphere and transition region play a key role in the formation and
acceleration of the solar wind. Observations from the Interface Region
Imaging Spectrograph reveal the prevalence of intermittent small-scale
jets with speeds of 80 to 250 kilometers per second from the narrow
bright network lanes of this interface region. These jets have lifetimes
of 20 to 80 seconds and widths of ≤300 kilometers. They originate from
small-scale bright regions, often preceded by footpoint brightenings
and accompanied by transverse waves with amplitudes of ~20 kilometers
per second. Many jets reach temperatures of at least ~105
kelvin and constitute an important element of the transition region
structures. They are likely an intermittent but persistent source of
mass and energy for the solar wind.
Title: On the prevalence of small-scale twist in the solar
chromosphere and transition region
Authors: De Pontieu, B.; Rouppe van der Voort, L.; McIntosh, S. W.;
Pereira, T. M. D.; Carlsson, M.; Hansteen, V.; Skogsrud, H.; Lemen,
J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser,
J. P.; De Luca, E. E.; Golub, L.; McKillop, S.; Reeves, K.; Saar,
S.; Testa, P.; Tian, H.; Kankelborg, C.; Jaeggli, S.; Kleint, L.;
Martinez-Sykora, J.
Bibcode: 2014Sci...346D.315D
Altcode: 2014arXiv1410.6862D
The solar chromosphere and transition region (TR) form an interface
between the Sun’s surface and its hot outer atmosphere. There,
most of the nonthermal energy that powers the solar atmosphere
is transformed into heat, although the detailed mechanism remains
elusive. High-resolution (0.33-arc second) observations with NASA’s
Interface Region Imaging Spectrograph (IRIS) reveal a chromosphere
and TR that are replete with twist or torsional motions on sub-arc
second scales, occurring in active regions, quiet Sun regions, and
coronal holes alike. We coordinated observations with the Swedish
1-meter Solar Telescope (SST) to quantify these twisting motions and
their association with rapid heating to at least TR temperatures. This
view of the interface region provides insight into what heats the low
solar atmosphere.
Title: An Interface Region Imaging Spectrograph First View on Solar
Spicules
Authors: Pereira, T. M. D.; De Pontieu, B.; Carlsson, M.; Hansteen,
V.; Tarbell, T. D.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt,
N.; Wülser, J. P.; Martínez-Sykora, J.; Kleint, L.; Golub, L.;
McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Tian, H.; Jaeggli,
S.; Kankelborg, C.
Bibcode: 2014ApJ...792L..15P
Altcode: 2014arXiv1407.6360P
Solar spicules have eluded modelers and observers for decades. Since
the discovery of the more energetic type II, spicules have become
a heated topic but their contribution to the energy balance of the
low solar atmosphere remains unknown. Here we give a first glimpse of
what quiet-Sun spicules look like when observed with NASA's recently
launched Interface Region Imaging Spectrograph (IRIS). Using IRIS
spectra and filtergrams that sample the chromosphere and transition
region, we compare the properties and evolution of spicules as
observed in a coordinated campaign with Hinode and the Atmospheric
Imaging Assembly. Our IRIS observations allow us to follow the thermal
evolution of type II spicules and finally confirm that the fading
of Ca II H spicules appears to be caused by rapid heating to higher
temperatures. The IRIS spicules do not fade but continue evolving,
reaching higher and falling back down after 500-800 s. Ca II H type
II spicules are thus the initial stages of violent and hotter events
that mostly remain invisible in Ca II H filtergrams. These events
have very different properties from type I spicules, which show lower
velocities and no fading from chromospheric passbands. The IRIS spectra
of spicules show the same signature as their proposed disk counterparts,
reinforcing earlier work. Spectroheliograms from spectral rasters also
confirm that quiet-Sun spicules originate in bushes from the magnetic
network. Our results suggest that type II spicules are indeed the
site of vigorous heating (to at least transition region temperatures)
along extensive parts of the upward moving spicular plasma.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Kushner, G. D.;
Akin, D. J.; Allard, B.; Berger, T.; Boerner, P.; Cheung, M.; Chou,
C.; Drake, J. F.; Duncan, D. W.; Freeland, S.; Heyman, G. F.; Hoffman,
C.; Hurlburt, N. E.; Lindgren, R. W.; Mathur, D.; Rehse, R.; Sabolish,
D.; Seguin, R.; Schrijver, C. J.; Tarbell, T. D.; Wülser, J. -P.;
Wolfson, C. J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons,
R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.;
Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.;
Phan, L.; Boyle, P.; Cheimets, P. N.; DeLuca, E. E.; Golub, L.;
Gates, R.; Hertz, E.; McKillop, S.; Park, S.; Perry, T.; Podgorski,
W. A.; Reeves, K.; Saar, S.; Testa, P.; Tian, H.; Weber, M.; Dunn, C.;
Eccles, S.; Jaeggli, S. A.; Kankelborg, C. C.; Mashburn, K.; Pust, N.;
Springer, L.; Carvalho, R.; Kleint, L.; Marmie, J.; Mazmanian, E.;
Pereira, T. M. D.; Sawyer, S.; Strong, J.; Worden, S. P.; Carlsson,
M.; Hansteen, V. H.; Leenaarts, J.; Wiesmann, M.; Aloise, J.; Chu,
K. -C.; Bush, R. I.; Scherrer, P. H.; Brekke, P.; Martinez-Sykora,
J.; Lites, B. W.; McIntosh, S. W.; Uitenbroek, H.; Okamoto, T. J.;
Gummin, M. A.; Auker, G.; Jerram, P.; Pool, P.; Waltham, N.
Bibcode: 2014SoPh..289.2733D
Altcode: 2014arXiv1401.2491D; 2014SoPh..tmp...25D
The Interface Region Imaging Spectrograph (IRIS) small explorer
spacecraft provides simultaneous spectra and images of the photosphere,
chromosphere, transition region, and corona with 0.33 - 0.4 arcsec
spatial resolution, two-second temporal resolution, and 1 km
s−1 velocity resolution over a field-of-view of up to
175 arcsec × 175 arcsec. IRIS was launched into a Sun-synchronous
orbit on 27 June 2013 using a Pegasus-XL rocket and consists of a
19-cm UV telescope that feeds a slit-based dual-bandpass imaging
spectrograph. IRIS obtains spectra in passbands from 1332 - 1358 Å,
1389 - 1407 Å, and 2783 - 2834 Å, including bright spectral lines
formed in the chromosphere (Mg II h 2803 Å and Mg II k 2796 Å) and
transition region (C II 1334/1335 Å and Si IV 1394/1403 Å). Slit-jaw
images in four different passbands (C II 1330, Si IV 1400, Mg II k
2796, and Mg II wing 2830 Å) can be taken simultaneously with spectral
rasters that sample regions up to 130 arcsec × 175 arcsec at a variety
of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to
emission from plasma at temperatures between 5000 K and 10 MK and will
advance our understanding of the flow of mass and energy through an
interface region, formed by the chromosphere and transition region,
between the photosphere and corona. This highly structured and dynamic
region not only acts as the conduit of all mass and energy feeding
into the corona and solar wind, it also requires an order of magnitude
more energy to heat than the corona and solar wind combined. The
IRIS investigation includes a strong numerical modeling component
based on advanced radiative-MHD codes to facilitate interpretation of
observations of this complex region. Approximately eight Gbytes of data
(after compression) are acquired by IRIS each day and made available
for unrestricted use within a few days of the observation.
Title: Detection of Supersonic Downflows and Associated Heating
Events in the Transition Region above Sunspots
Authors: Kleint, L.; Antolin, P.; Tian, H.; Judge, P.; Testa, P.;
De Pontieu, B.; Martínez-Sykora, J.; Reeves, K. K.; Wuelser, J. P.;
McKillop, S.; Saar, S.; Carlsson, M.; Boerner, P.; Hurlburt, N.; Lemen,
J.; Tarbell, T. D.; Title, A.; Golub, L.; Hansteen, V.; Jaeggli, S.;
Kankelborg, C.
Bibcode: 2014ApJ...789L..42K
Altcode: 2014arXiv1406.6816K
Interface Region Imaging Spectrograph data allow us to study the solar
transition region (TR) with an unprecedented spatial resolution of
0.''33. On 2013 August 30, we observed bursts of high Doppler shifts
suggesting strong supersonic downflows of up to 200 km s-1
and weaker, slightly slower upflows in the spectral lines Mg II h
and k, C II 1336, Si IV 1394 Å, and 1403 Å, that are correlated
with brightenings in the slitjaw images (SJIs). The bursty behavior
lasts throughout the 2 hr observation, with average burst durations
of about 20 s. The locations of these short-lived events appear to
be the umbral and penumbral footpoints of EUV loops. Fast apparent
downflows are observed along these loops in the SJIs and in the
Atmospheric Imaging Assembly, suggesting that the loops are thermally
unstable. We interpret the observations as cool material falling
from coronal heights, and especially coronal rain produced along the
thermally unstable loops, which leads to an increase of intensity
at the loop footpoints, probably indicating an increase of density
and temperature in the TR. The rain speeds are on the higher end of
previously reported speeds for this phenomenon, and possibly higher
than the free-fall velocity along the loops. On other observing days,
similar bright dots are sometimes aligned into ribbons, resembling
small flare ribbons. These observations provide a first insight into
small-scale heating events in sunspots in the TR.
Title: Lockheed Solar Observatory and the Discovery of Moreton-Ramsey
Waves
Authors: Tarbell, Theodore D.
Bibcode: 2014AAS...22420303T
Altcode:
Moreton Waves are high-speed disturbances seen traveling away from
large solar flares in H-alpha movies of the solar chromosphere. They
were discovered by the observer Harry Ramsey in the late 1950s, and
then published and publicized by the director Gail Moreton, both of
the Lockheed Solar Observatory in the Hollywood Hills of Southern
California. These efforts established the scientific reputation and
secured continuing funding of the observatory, whose present-day
successor is the Lockheed Martin Solar and Astrophysics Lab in Palo
Alto. Moreton waves are rare, and there was limited interest in them
until the EIT instrument on SOHO began seeing large numbers of similar
waves in the corona in the late 1990s. The exact relation between
the two observations is still a research topic today. This talk will
describe some of the history of the observatory and the discovery and
early interpretation of the waves.
Title: The SUVIT Instrument on the Solar-C Mission
Authors: Tarbell, Theodore D.; Ichimoto, Kiyoshi
Bibcode: 2014AAS...22412363T
Altcode:
Solar-C is a new space mission being proposed to JAXA, with significant
contributions anticipated from NASA, ESA, and EU countries. The main
scientific objectives are to: reveal the mechanisms for heating and
dynamics of the chromosphere and corona and acceleration of the solar
wind; determine the physical origin of the large-scale explosions
and eruptions that drive short-term solar, heliospheric, and geospace
variability; use the solar atmosphere as a laboratory for understanding
fundamental physical processes; make unprecedented observations
of the polar magnetic fields. The unique approaches of Solar-C to
achieve these goals are to: determine the properties and evolution of
the 3-dimensional magnetic field, especially on small spatial scales,
and for the first time observed in the crucial low beta plasma region;
observe all the temperature regimes of the atmosphere seamlessly at
the highest spatial resolution ever achieved; observe at high cadence
the prevailing dynamics in all regions of the atmosphere; determine
physical properties from high resolution spectroscopic measurements
throughout the atmosphere and into the solar wind. The powerful suite
of instruments onboard Solar-C will be sensitive to temperatures from
the photosphere 5500 K) to solar flares 20 MK) with no temperature
gap, with spatial resolution at all temperatures of 0.3″ or less
(0.1″ in the lower atmosphere) and at high cadence. The purpose of
the Solar UV-Visible-IR Telescope (SUVIT) is to obtain chromospheric
velocity, temperature, density and magnetic field diagnostics
over as wide arange of heights as possible, through high cadence
spectral line profiles and vector spectro-polarimetry. SUVIT is a
meter-class telescope currently under study at 1.4m in order to obtain
sufficientresolution and S/N. SUVIT has two complementary focal plane
packages, the Filtergraph that makes high cadence imaging observations
with the highest spatial resolution and the Spectro-polarimeter that
makes precise spectro-polarimetric observations. With their powerful
sets of spectral lines, FG and SP collect physical measurements from
the lower photosphere to upper chromosphere with much better spatial
and temporal resolution than Hinode SOT.
Title: High-resolution Observations of the Shock Wave Behavior for
Sunspot Oscillations with the Interface Region Imaging Spectrograph
Authors: Tian, H.; DeLuca, E.; Reeves, K. K.; McKillop, S.; De Pontieu,
B.; Martínez-Sykora, J.; Carlsson, M.; Hansteen, V.; Kleint, L.;
Cheung, M.; Golub, L.; Saar, S.; Testa, P.; Weber, M.; Lemen, J.;
Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.;
Kankelborg, C.; Jaeggli, S.; McIntosh, S. W.
Bibcode: 2014ApJ...786..137T
Altcode: 2014arXiv1404.6291T
We present the first results of sunspot oscillations from observations
by the Interface Region Imaging Spectrograph. The strongly nonlinear
oscillation is identified in both the slit-jaw images and the
spectra of several emission lines formed in the transition region and
chromosphere. We first apply a single Gaussian fit to the profiles of
the Mg II 2796.35 Å, C II 1335.71 Å, and Si IV 1393.76 Å lines in the
sunspot. The intensity change is ~30%. The Doppler shift oscillation
reveals a sawtooth pattern with an amplitude of ~10 km s-1
in Si IV. The Si IV oscillation lags those of C II and Mg II by ~3 and
~12 s, respectively. The line width suddenly increases as the Doppler
shift changes from redshift to blueshift. However, we demonstrate
that this increase is caused by the superposition of two emission
components. We then perform detailed analysis of the line profiles at
a few selected locations on the slit. The temporal evolution of the
line core is dominated by the following behavior: a rapid excursion
to the blue side, accompanied by an intensity increase, followed by a
linear decrease of the velocity to the red side. The maximum intensity
slightly lags the maximum blueshift in Si IV, whereas the intensity
enhancement slightly precedes the maximum blueshift in Mg II. We find
a positive correlation between the maximum velocity and deceleration,
a result that is consistent with numerical simulations of upward
propagating magnetoacoustic shock waves.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, Bart; Title, A. M.; Lemen, J.; Wuelser, J.;
Tarbell, T. D.; Schrijver, C. J.; Golub, L.; Kankelborg, C.; Carlsson,
M.; Hansteen, V. H.; Worden, S.; IRIS Team
Bibcode: 2013SPD....44...03D
Altcode:
The solar chromosphere and transition region (TR) form a highly
structured and dynamic interface region between the photosphere and
the corona. This region not only acts as the conduit of all mass and
energy feeding into the corona and solar wind, it also requires an
order of magnitude more energy to heat than the corona. Nevertheless,
the chromosphere remains poorly understood, because of the complexity
of the required observational and analytical tools: the interface
region is highly complex with transitions from optically thick to
optically thin radiation, from pressure to magnetic field domination,
and large density and temperature contrasts on small spatial scales. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch on 26-June-2013 (with
first light scheduled for mid July). IRIS addresses critical questions:
(1) Which types of non-thermal energy dominate in the chromosphere and
beyond? (2) How does the chromosphere regulate mass and energy supply
to the corona and heliosphere? (3) How do magnetic flux and matter
rise through the lower atmosphere, and what role does flux emergence
play in flares and mass ejections? These questions are addressed with
a high-resolution near and far UV imaging spectrometer sensitive to
emission from plasma at temperatures between 5,000 K and 10 MK. IRIS
has a field-of-view of 120 arcsec, a spatial resolution of 0.4 arcsec,
and velocity resolution of 0.5 km/s. The IRIS investigation includes
a strong numerical modeling component based on advanced radiative MHD
codes to facilitate interpretation of observations. We describe the
IRIS instrumentation and numerical modeling, and present the plans for
observations, calibration and data distribution. We will highlight some
of the issues that IRIS observations can help resolve. More information
can be found at http://iris.lmsal.com
Title: The Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Akin, D. L.; Card, G.; Cruz, T.; Duncan, D. W.;
Edwards, C. G.; Elmore, D. F.; Hoffmann, C.; Katsukawa, Y.; Katz, N.;
Kubo, M.; Ichimoto, K.; Shimizu, T.; Shine, R. A.; Streander, K. V.;
Suematsu, A.; Tarbell, T. D.; Title, A. M.; Tsuneta, S.
Bibcode: 2013SoPh..283..579L
Altcode:
The joint Japan/US/UK Hinode mission includes the first large-aperture
visible-light solar telescope flown in space. One component of the
Focal Plane Package of that telescope is a precision spectro-polarimeter
designed to measure full Stokes spectra with the intent of using those
spectra to infer the magnetic-field vector at high precision in the
solar photosphere. This article describes the characteristics of the
flight hardware of the HinodeSpectro-Polarimeter, and summarizes its
in-flight performance.
Title: The Interface Region Imaging Spectrograph (IRIS)
Authors: De Pontieu, B.; Title, A. M.; Lemen, J. R.; Wuelser, J.;
Tarbell, T. D.; Schrijver, C.; Golub, L.; Kankelborg, C. C.; Hansteen,
V. H.; Carlsson, M.
Bibcode: 2012AGUFMSH33D2256D
Altcode:
The solar chromosphere and transition region (TR) form a highly
structured and dynamic interface region between the photosphere and
the corona. This region not only acts as the conduit of all mass and
energy feeding into the corona and solar wind, it also requires an
order of magnitude more energy to heat than the corona. Nevertheless,
the chromosphere remains poorly understood, because of the complexity
of the required observational and analytical tools: the interface
region is highly complex with transitions from optically thick to
optically thin radiation, from pressure to magnetic field domination,
and large density and temperature contrasts on small spatial scales. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch in early 2013. IRIS
addresses critical questions: (1) Which types of non-thermal energy
dominate in the chromosphere and beyond? (2) How does the chromosphere
regulate mass and energy supply to the corona and heliosphere? (3)
How do magnetic flux and matter rise through the lower atmosphere, and
what role does flux emergence play in flares and mass ejections? These
questions are addressed with a high-resolution near and far UV imaging
spectrometer sensitive to emission from plasma at temperatures between
5,000 K and 10 MK. IRIS has a field-of-view of 120 arcsec, a spatial
resolution of 0.4 arcsec, and velocity resolution of 0.5 km/s. The
IRIS investigation includes a strong numerical modeling component
based on advanced radiative MHD codes to facilitate interpretation of
observations. We will describe the IRIS instrumentation and numerical
modeling, and present the status of the IRIS observatory development. We
will highlight some of the issues that IRIS observations can help
resolve.
Title: Interaction of Cometary Material With the Solar Corona:
EUV Observations and MHD Simulations
Authors: Liu, W.; Jia, Y.; Downs, C.; Schrijver, C.; Saint-Hilaire,
P.; Battams, K.; Tarbell, T. D.; Shine, R. A.
Bibcode: 2012AGUFMSH13B2254L
Altcode:
Extreme ultraviolet (EUV) emission from two recent sun-grazing comets,
C/2011 N3 and C/2011 W3 (Lovejoy), has been observed in the solar corona
for the first time by the SDO/AIA and STEREO/EUVI instruments (Schrijver
et al. 2011). These observations provided a unique opportunity to
investigate the interaction of the cometary material with the solar
corona and probe their physical conditions. We present here EUV
observations and MHD simulations on this subject, focusing on the
deceleration of the cometary tail material within the corona. We found
that despite their different local coronal environments, the two comets
exhibited quite similar characteristics. The initial EUV emitting tail
had a projected velocity of 100-200 km/s, which was much lower than the
orbital velocity of 500-600 km/s in the plane-of-sky. This indicates
that significant deceleration had taken place while the tail material
was heated to coronal temperatures on the order of 1 MK before it
started to emit in EUV (Bryans & Pesnell 2012). After its initial
appearance, the tail further experienced a projected deceleration
of ~1 km/s^2 (or 4 g_Sun). In particular, in the Lovejoy case, the
tail appeared as clusters of bright parallel striations roughly at
right angles to the orbit direction, suggestive of magnetic field
lines illuminated by the plasma frozen onto them. These striations
came to a stop and then accelerated in an opposite direction (seen
in projection), approaching a constant velocity of ~50 km/s. These
observations suggest that a Lorentz force from the coronal magnetic
field was operating on the newly ionized cometary plasma. To test this
hypothesis and understand tail deceleration mechanisms, we adopted a
multi-fluid MHD model (Jia et al. 2012) to simulate the interaction
between charged particles and the magnetized coronal plasma. We used
potential extrapolation (Schrijver & DeRosa 2003) and a more
sophisticated global MHD model (Lionello et al. 2009) to infer the
magnetic field and plasma conditions of the corona along the comet's
orbit as inputs to the simulations. We will compare the observations and
simulation results, and discuss the implications for using sun-grazing
comets as probes to the solar corona in the context of NASA's future
Solar Probe Plus mission.
Title: The interface region imaging spectrograph for the IRIS Small
Explorer mission
Authors: Wülser, Jean-Pierre; Title, Alan M.; Lemen, James R.; De
Pontieu, Bart; Kankelborg, Charles C.; Tarbell, Theodore D.; Berger,
Thomas E.; Golub, Leon; Kushner, Gary D.; Chou, Catherine Y.; Weingrod,
Isaac; Holmes, Buck; Mudge, Jason; Podgorski, William A.
Bibcode: 2012SPIE.8443E..08W
Altcode:
The Interface Region Imaging Spectrograph (IRIS) is a NASA SMall
EXplorer mission scheduled for launch in January 2013. The primary goal
of IRIS is to understand how the solar atmosphere is energized. The
IRIS investigation combines advanced numerical modeling with a high
resolution UV imaging spectrograph. IRIS will obtain UV spectra
and images with high resolution in space (0.4 arcsec) and time (1s)
focused on the chromosphere and transition region of the Sun, a complex
interface region between the photosphere and corona. The IRIS instrument
uses a Cassegrain telescope to feed a dual spectrograph and slit-jaw
imager that operate in the 133-141 nm and 278-283 nm ranges. This paper
describes the instrument with emphasis on the imaging spectrograph,
and presents an initial performance assessment from ground test results.
Title: Plasma Instabilities in Quiescent Prominences
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Title, A.; Tarbell, T.
Bibcode: 2012ASPC..454..143R
Altcode:
We study dynamics of quiescent prominences using several data sets
taken with the SOT on Hinode. We find a number of processes occurring
at different stages of the prominence evolution that are common for
all the chosen cases, and having universal character, can be related
to a fundamental plasma instabilities. We combine the observational
evidence and theory to identify these instabilities. Here we discuss
only two examples: (1) Coronal cavity formation under a prominence
body and its evolution associated with screw pinch instability, and
(2) Development of a regular series of plumes and spikes typical to
the Rayleigh-Taylor instability modified by solenoidal magnetic field.
Title: Quasi-periodic Fast-mode Wave Trains within a Global EUV Wave
and Sequential Transverse Oscillations Detected by SDO/AIA
Authors: Liu, Wei; Ofman, Leon; Nitta, Nariaki V.; Aschwanden, Markus
J.; Schrijver, Carolus J.; Title, Alan M.; Tarbell, Theodore D.
Bibcode: 2012ApJ...753...52L
Altcode: 2012arXiv1204.5470L
We present the first unambiguous detection of quasi-periodic wave
trains within the broad pulse of a global EUV wave (so-called EIT wave)
occurring on the limb. These wave trains, running ahead of the lateral
coronal mass ejection (CME) front of 2-4 times slower, coherently
travel to distances >~ R ⊙/2 along the solar surface,
with initial velocities up to 1400 km s-1 decelerating to
~650 km s-1. The rapid expansion of the CME initiated at
an elevated height of 110 Mm produces a strong downward and lateral
compression, which may play an important role in driving the primary
EUV wave and shaping its front forwardly inclined toward the solar
surface. The wave trains have a dominant 2 minute periodicity that
matches the X-ray flare pulsations, suggesting a causal connection. The
arrival of the leading EUV wave front at increasing distances produces
an uninterrupted chain sequence of deflections and/or transverse (likely
fast kink mode) oscillations of local structures, including a flux-rope
coronal cavity and its embedded filament with delayed onsets consistent
with the wave travel time at an elevated (by ~50%) velocity within
it. This suggests that the EUV wave penetrates through a topological
separatrix surface into the cavity, unexpected from CME-caused magnetic
reconfiguration. These observations, when taken together, provide
compelling evidence of the fast-mode MHD wave nature of the primary
(outer) fast component of a global EUV wave, running ahead of the
secondary (inner) slow component of CME-caused restructuring.
Title: The Journey of Sungrazing Comet Lovejoy
Authors: Bryans, Paul; A'Hearn, M.; Battams, K.; Biesecker, D.;
Bodewits, D.; Boice, D.; Brown, J.; Caspi, A.; Chodas, P.; Hudson,
H.; Jia, Y.; Jones, G.; Keller, H. U.; Knight, M.; Linker, J.; Lisse,
C.; Liu, W.; McIntosh, S.; Pesnell, W. D.; Raymond, J.; Saar, S.;
Saint-Hilaire, P.; Schrijver, C.; Snow, M.; Tarbell, T.; Thompson,
W.; Weissman, P.; Comet Lovejoy Collaboration Team
Bibcode: 2012AAS...22052507B
Altcode:
Comet Lovejoy (C/2011 W3) was the first sungrazing comet, observed
by space-based instruments, to survive perihelion passage. First
observed by ground-based telescopes several weeks prior to perihelion,
its journey towards the Sun was subsequently recorded by several solar
observatories, before being observed in the weeks after perihelion by
a further array of space- and ground-based instruments. Such a surfeit
of wide-ranging observations provides an unprecedented insight into
both sungrazing comets themselves, and the solar atmosphere through
which they pass. This paper will summarize what we have learnt from the
observations thus far and offer some thoughts on what future sungrazing
comets may reveal about comets, the Sun, and their interaction.
Title: SDO/AIA Detection of Quasi-periodic Wave Trains Within Global
EUV ("EIT") Waves and Their Coronal Seismology Implications
Authors: Liu, Wei; Ofman, L.; Aschwanden, M. J.; Nitta, N.; Schrijver,
C. J.; Title, A. M.; Tarbell, T. D.
Bibcode: 2012AAS...22051501L
Altcode:
The nature of global EUV waves (so-called "EIT waves") has long
been under debate because of instrumental limitations and projection
effects when viewed on the solar disk. We present here high cadence
SDO/AIA observations of global EUV waves occurring on the limb. We
report newly discovered quasi-periodic wave trains located in the low
corona within a broad, diffuse pulse of the global EUV wave ahead of
the lateral CME front/flank. These waves coherently travel to large
distances on the order of 1 solar radii with initial velocities up
to 1400 km/s. They have dominant 1-3 minute periodicities that often
match the X-ray pulsations of the accompanying flare, suggestive of
a causal connection. In addition, recently discovered quasi-periodic
fast propagating (QFP) waves of 1000-2000 km/s (Liu, Title, Zhao et
al. 2011 ApJL) are found in the funnel of coronal loops rooted at the
flare kernel. These waves are spatially confined within the CME bubble
and rapidly disappear while approaching the CME front, suggestive
of strong damping and/or dispersion. These observations provide new
evidence of the fast-mode wave nature of the primary, fast component
of a global EUV wave, running ahead of a secondary, slow component
of CME-caused restructuring of the coronal magnetic field. We suggest
that the two types of quasi-periodic waves are both integral parts of
global coronal dynamics manifested as a CME/flare eruption, and they
have important implications for global and local coronal seismology.
Title: Some Like it Hot: the Trajectory of Sungrazing Comet C/2011 W3
(Lovejoy) in the Solar Neighborhood.
Authors: Saint-Hilaire, Pascal; Chodas, P. W.; Battams, K.; Tarbell,
T. D.; Shine, R. A.; Liu, W.; Thompson, W. T.; Comet Lovejoy
Collaboration Team
Bibcode: 2012AAS...22052107S
Altcode:
Sungrazing comet Lovejoy (C/2011 W3) was a recent spectacle in the sky,
observed from the ground and by a host of space-based instruments,
including several solar observatories. It is the first sungrazing comet
in recent memory to have survived perihelion (q 1.2 Rs). It is only
the second sungrazer to have been observed in the Sun's low corona in
the extreme ultra-violet (EUV), where a plethora of EUV observations
were obtained by the SDO and STEREO spacecraft. Such an occurrence
can be used to probe the solar corona and test our understanding
of plasma and cometary physics. In this work, we use the best orbit
elements currently available to plot the path of the comet's nucleus on
solar EUV images from SDO/AIA, both STEREO/EUVIs, and yellow continuum
(near the Na D lines) images from Hinode/SOT. We compare the predicted
positions and timing of the comet's nucleus to the latter, while the
SDO and STEREO EUV observations are used to estimate the distance at
which the EUV tail appears behind the comet's nucleus.
Title: Magnetic Topology of a Naked Sunspot: Is It Really Naked?
Authors: Sainz Dalda, A.; Vargas Domínguez, S.; Tarbell, T. D.
Bibcode: 2012ApJ...746L..13S
Altcode: 2012arXiv1202.0591S
The high spatial, temporal, and spectral resolution achieved by Hinode
instruments gives much better understanding of the behavior of some
elusive solar features, such as pores and naked sunspots. Their fast
evolution and, in some cases, their small sizes have made their study
difficult. The moving magnetic features (MMFs) have been studied during
the last 40 years. They have been always associated with sunspots,
especially with the penumbra. However, a recent observation of a naked
sunspot (one with no penumbra) has shown MMF activity. The authors
of this reported observation expressed their reservations about the
explanation given to the bipolar MMF activity as an extension of the
penumbral filaments into the moat. How can this type of MMF exist when
a penumbra does not? In this Letter, we study the full magnetic and
(horizontal) velocity topology of the same naked sunspot, showing how
the existence of a magnetic field topology similar to that observed
in sunspots can explain these MMFs, even when the intensity map of
the naked sunspot does not show a penumbra.
Title: The Atmospheric Imaging Assembly (AIA) on the Solar Dynamics
Observatory (SDO)
Authors: Lemen, James R.; Title, Alan M.; Akin, David J.; Boerner,
Paul F.; Chou, Catherine; Drake, Jerry F.; Duncan, Dexter W.; Edwards,
Christopher G.; Friedlaender, Frank M.; Heyman, Gary F.; Hurlburt, Neal
E.; Katz, Noah L.; Kushner, Gary D.; Levay, Michael; Lindgren, Russell
W.; Mathur, Dnyanesh P.; McFeaters, Edward L.; Mitchell, Sarah; Rehse,
Roger A.; Schrijver, Carolus J.; Springer, Larry A.; Stern, Robert A.;
Tarbell, Theodore D.; Wuelser, Jean-Pierre; Wolfson, C. Jacob; Yanari,
Carl; Bookbinder, Jay A.; Cheimets, Peter N.; Caldwell, David; Deluca,
Edward E.; Gates, Richard; Golub, Leon; Park, Sang; Podgorski, William
A.; Bush, Rock I.; Scherrer, Philip H.; Gummin, Mark A.; Smith, Peter;
Auker, Gary; Jerram, Paul; Pool, Peter; Soufli, Regina; Windt, David
L.; Beardsley, Sarah; Clapp, Matthew; Lang, James; Waltham, Nicholas
Bibcode: 2012SoPh..275...17L
Altcode: 2011SoPh..tmp..106L; 2011SoPh..tmp..172L; 2011SoPh..tmp..241L;
2011SoPh..tmp..115L
The Atmospheric Imaging Assembly (AIA) provides multiple simultaneous
high-resolution full-disk images of the corona and transition region
up to 0.5 R⊙ above the solar limb with 1.5-arcsec spatial
resolution and 12-second temporal resolution. The AIA consists of four
telescopes that employ normal-incidence, multilayer-coated optics to
provide narrow-band imaging of seven extreme ultraviolet (EUV) band
passes centered on specific lines: Fe XVIII (94 Å), Fe XVII, XXI
(131 Å), Fe IX (171 Å), Fe XII, XXIV (193 Å), Fe XIV (211 Å),
He II (304 Å), and Fe XVI (335 Å). One telescope observes C IV
(near 1600 Å) and the nearby continuum (1700 Å) and has a filter
that observes in the visible to enable coalignment with images from
other telescopes. The temperature diagnostics of the EUV emissions
cover the range from 6×104 K to 2×107 K. The
AIA was launched as a part of NASA's Solar Dynamics Observatory (SDO)
mission on 11 February 2010. AIA will advance our understanding of the
mechanisms of solar variability and of how the Sun's energy is stored
and released into the heliosphere and geospace.
Title: Initial Calibration of the Atmospheric Imaging Assembly (AIA)
on the Solar Dynamics Observatory (SDO)
Authors: Boerner, Paul; Edwards, Christopher; Lemen, James; Rausch,
Adam; Schrijver, Carolus; Shine, Richard; Shing, Lawrence; Stern,
Robert; Tarbell, Theodore; Title, Alan; Wolfson, C. Jacob; Soufli,
Regina; Spiller, Eberhard; Gullikson, Eric; McKenzie, David; Windt,
David; Golub, Leon; Podgorski, William; Testa, Paola; Weber, Mark
Bibcode: 2012SoPh..275...41B
Altcode:
The Atmospheric Imaging Assembly (AIA) instrument onboard the Solar
Dynamics Observatory (SDO) is an array of four normal-incidence
reflecting telescopes that image the Sun in ten EUV and UV wavelength
channels. We present the initial photometric calibration of AIA,
based on preflight measurements of the response of the telescope
components. The estimated accuracy is of order 25%, which is consistent
with the results of comparisons with full-disk irradiance measurements
and spectral models. We also describe the characterization of the
instrument performance, including image resolution, alignment,
camera-system gain, flat-fielding, and data compression.
Title: Design and Ground Calibration of the Helioseismic and Magnetic
Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)
Authors: Schou, J.; Scherrer, P. H.; Bush, R. I.; Wachter, R.;
Couvidat, S.; Rabello-Soares, M. C.; Bogart, R. S.; Hoeksema, J. T.;
Liu, Y.; Duvall, T. L.; Akin, D. J.; Allard, B. A.; Miles, J. W.;
Rairden, R.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Wolfson,
C. J.; Elmore, D. F.; Norton, A. A.; Tomczyk, S.
Bibcode: 2012SoPh..275..229S
Altcode:
The Helioseismic and Magnetic Imager (HMI) investigation (Solar
Phys. doi:10.1007/s11207-011-9834-2, 2011) will study the solar
interior using helioseismic techniques as well as the magnetic field
near the solar surface. The HMI instrument is part of the Solar
Dynamics Observatory (SDO) that was launched on 11 February 2010. The
instrument is designed to measure the Doppler shift, intensity, and
vector magnetic field at the solar photosphere using the 6173 Å Fe I
absorption line. The instrument consists of a front-window filter, a
telescope, a set of waveplates for polarimetry, an image-stabilization
system, a blocking filter, a five-stage Lyot filter with one tunable
element, two wide-field tunable Michelson interferometers, a pair
of 40962 pixel cameras with independent shutters, and
associated electronics. Each camera takes a full-disk image roughly
every 3.75 seconds giving an overall cadence of 45 seconds for the
Doppler, intensity, and line-of-sight magnetic-field measurements
and a slower cadence for the full vector magnetic field. This article
describes the design of the HMI instrument and provides an overview of
the pre-launch calibration efforts. Overviews of the investigation,
details of the calibrations, data handling, and the science analysis
are provided in accompanying articles.
Title: The Helioseismic and Magnetic Imager (HMI) Investigation for
the Solar Dynamics Observatory (SDO)
Authors: Scherrer, P. H.; Schou, J.; Bush, R. I.; Kosovichev, A. G.;
Bogart, R. S.; Hoeksema, J. T.; Liu, Y.; Duvall, T. L.; Zhao, J.;
Title, A. M.; Schrijver, C. J.; Tarbell, T. D.; Tomczyk, S.
Bibcode: 2012SoPh..275..207S
Altcode:
The Helioseismic and Magnetic Imager (HMI) instrument and investigation
as a part of the NASA Solar Dynamics Observatory (SDO) is designed
to study convection-zone dynamics and the solar dynamo, the origin
and evolution of sunspots, active regions, and complexes of activity,
the sources and drivers of solar magnetic activity and disturbances,
links between the internal processes and dynamics of the corona and
heliosphere, and precursors of solar disturbances for space-weather
forecasts. A brief overview of the instrument, investigation objectives,
and standard data products is presented.
Title: Spectropolarimetric Comparison Between SDO/HMI and
Hinode-SOT/SP Through THEMIS/MTR
Authors: Sainz Dalda, A.; Lopez Ariste, A.; Gelly, B.; Tarbell, T. D.;
Centeno, R.; DeRosa, M. L.; Hoeksema, J. T.
Bibcode: 2011AGUFMSH31A1986S
Altcode:
In the golden age of solar spacecraft observatories, the use of similar
instruments observing same targets offers us the possibility to get
more accurate information of the physical processes taking place on
them. We present a comparison between the vector magnetic field and
thermodynamic quantities obtained by three different spectropolarimetric
instruments. We have used the simultaneous multi-wavelength capabilities
of THEMIS/MTR as bridge between the observations at Fe I 6173 Å
provided by SDO/HMI and at Fe I 6301 & 6302 Å by Hinode-SOT/SP
observations. The official inversion codes for these instruments (PCA
based-on, VFISV and MERLIN respectively) have been used with the data
properly arranged for them. Therefore, we compare the final products
usually offered to the community, i.e. after the inversion, using
different codes and these different wavelengths. The cross-calibration
of these products shall allow us to go forward from one instrument
result to other one in an easy, convenient way.
Title: Direct Imaging of Quasi-periodic Fast Propagating Waves of
~2000 km s-1 in the Low Solar Corona by the Solar Dynamics
Observatory Atmospheric Imaging Assembly
Authors: Liu, Wei; Title, Alan M.; Zhao, Junwei; Ofman, Leon;
Schrijver, Carolus J.; Aschwanden, Markus J.; De Pontieu, Bart;
Tarbell, Theodore D.
Bibcode: 2011ApJ...736L..13L
Altcode: 2011arXiv1106.3150L
Quasi-periodic propagating fast mode magnetosonic waves in the solar
corona were difficult to observe in the past due to relatively low
instrument cadences. We report here evidence of such waves directly
imaged in EUV by the new Atmospheric Imaging Assembly instrument
on board the Solar Dynamics Observatory. In the 2010 August 1 C3.2
flare/coronal mass ejection event, we find arc-shaped wave trains of
1%-5% intensity variations (lifetime ~200 s) that emanate near the
flare kernel and propagate outward up to ~400 Mm along a funnel of
coronal loops. Sinusoidal fits to a typical wave train indicate a phase
velocity of 2200 ± 130 km s-1. Similar waves propagating
in opposite directions are observed in closed loops between two flare
ribbons. In the k-ω diagram of the Fourier wave power, we find a
bright ridge that represents the dispersion relation and can be well
fitted with a straight line passing through the origin. This k-ω
ridge shows a broad frequency distribution with power peaks at 5.5,
14.5, and 25.1 mHz. The strongest signal at 5.5 mHz (period 181 s)
temporally coincides with quasi-periodic pulsations of the flare,
suggesting a common origin. The instantaneous wave energy flux
of (0.1-2.6) × 107 erg cm-2 s-1
estimated at the coronal base is comparable to the steady-state heating
requirement of active region loops.
Title: SDO/AIA Observations of a Global EUV Disturbance Traveling
into a Coronal Cavity and Its Subsequent Oscillations: New Evidence
of Fast Mode MHD Waves
Authors: Liu, Wei; Aschwanden, M. J.; Ofman, L.; Nitta, N. V.; Tarbell,
T. D.
Bibcode: 2011SPD....42.0906L
Altcode: 2011BAAS..43S.0906L
We report new SDO/AIA observations of a global EUV disturbance
that propagates at 600 km/s and sweeps through a coronal cavity,
instigating its bodily transverse oscillations. The high temporal
resolution and large FOV of AIA allow us to clearly see, for the first
time, the timing coincidence between the onsets of the oscillations
and the arrival of the disturbance at increasing distances covering
300 Mm in the neighborhood of the cavity. There is a time delay of
the oscillations from the near side to the far side of the cavity,
which is consistent with the travel time of the global perturbation. In
addition, we find a fine structure consisting of evenly spaced pulses
of periods 100-120 s within the global disturbance. In contrast, the
CME loop expansion falls behind the global disturbance at a smaller
velocity of 200 km/s. These observations suggests that this global
disturbance is a real fast mode MHD wave that continues propagating
into the cavity, rather than an apparent wave caused by CME expulsion
that is not expected to penetrate through a topological separatrix,
including the flux rope cavity boundary here. The cavity and its
hosted prominence have oscillation amplitudes of 20 km/s and periods
of 20-30 minutes. Such unusually long periods, compared with a few
minutes commonly observed in coronal loops, likely reflect kink mode
oscillations of the long cavity flux rope of a large length (a fraction
of the solar radius).
Title: The Interface Region Imaging Spectrograph (IRIS) NASA SMEX
Authors: Lemen, James; Title, A.; De Pontieu, B.; Schrijver, C.;
Tarbell, T.; Wuelser, J.; Golub, L.; Kankelborg, C.
Bibcode: 2011SPD....42.1512L
Altcode: 2011BAAS..43S.1512L
The solar chromosphere and transition region (TR) is highly structured,
dynamic, and intimately connected to the corona. It requires more
than ten times the energy required to heat the corona, and yet it
has received far less interest because of the complexity of the
required observational and analytical tools. In the TR the density
drops by six orders of magnitude and the temperature increases by
three orders of magnitude. Hinode observations reveal the importance
the magnetic field has on this region of the solar atmosphere that
acts as the interface between the photosphere and the corona. The
Interface Region Imaging Spectrograph (IRIS) was selected for a NASA
SMEX mission in 2009 and is scheduled to launch in December 2012. IRIS
addresses critical questions in order to understand the flow of energy
and mass through the chromosphere and TR, namely: (1) Which types of
non-thermal energy dominate in the chromosphere and beyond? (2) How
does the chromosphere regulate mass and energy supply to the corona
and heliosphere? (3) How do magnetic flux and matter rise through the
lower atmosphere, and what roles dos flux emergence play in flares and
mass ejections? These questions are addressed with a high-resolution
imaging spectrometer that observes Near- and Far-VU emissions that
are formed at temperatures between 5,000K and 1.5 x 106
K. IRIS has a field-of-view of 120 arcsec, a spatial resolution
of 0.4 arcsec, and velocity resolution of 0.5 km/s. Members of the
IRIS investigation team are developing advanced radiative MHD codes
to facilitate comparison with and interpretation of observations. We
present the status of the IRIS observatory development, which completed
its Critical Design Review in December 2010.
Title: Spectropolarimetric Study of Sea-serpent Penumbral Filaments
and a Naked Sunspot
Authors: Sainz Dalda, Alberto; Tarbell, T.; Title, A.; Vargas
Dominguez, S.; Bellot Rubio, L. R.
Bibcode: 2011SPD....42.0303S
Altcode: 2011BAAS..43S.0303S
We present a spectropolarimetric study of the sea-serpent penumbral
filaments in AR NOAA 10944 and of a naked sunspot (i.e. a sunspot-like
feature without penumbra) in AR NOAA 10977. Both active regions were
observed by Hinode-SOT/SP in the photospheric lines Fe I 6301 &
6302 [[Unable to Display Character: Ǻ]]. The high spatial and
temporal resolution combined with the high polarimetric sensitivity
of these observations enables us to get a better understanding of the
dynamics of the penumbra and the moving magnetic feature (herafter MMF)
activity in and around both traditional and naked sunspots. Our results
show how the temporal evolution of the sea-serpent filaments fits
very well with the thin-tube flux model for the penumbra presented by
Schlichenmaier (2003). In addition, the spectropolarmetric analysis of
the naked sunspot addresses the issue posed by Zuccarello et al. (2009)
about the existence of bipolar MMFs around naked sunspots even when
they cannot be explained as an extension of the penumbral filaments.
Title: Helioseismic Studies With Multi-wavelength Data From HMI And
AIA Onboard SDO
Authors: Hill, Frank; Jain, K.; Tripathy, S.; Kholikov, S.; Gonzalez
Hernandez, I.; Leibacher, J.; Howe, R.; Baudin, F.; Carlsson, M.;
Chaplin, W.; Tarbell, T.
Bibcode: 2011SPD....42.2111H
Altcode: 2011BAAS..43S.2111H
The successful launch of the Solar Dynamics Observatory (SDO) in
February 2010 opens important, new possibilities for helioseismic
exploration of the solar interior and atmosphere using multi-wavelength
observations from multiple instruments. In order to better understand
the solar interior and atmosphere, as well as the physics of the
helioseismic modes and waves themselves, we exploit the potential of
the Atmospheric Imaging Assembly (AIA) 1600 and 1700 Angstrom continuum
measurements and the contemporaneous Helioseismic and Magnetic Imager
(HMI) Fe I 6173.3 Angstrom velocity and intensity observations. Standard
techniques of helioseismology e.g Sun-as-a-star, spherical harmonic
analysis, ring diagrams, and time- distance analysis are applied to
obtain acoustic mode parameters and other characteristics. Here we
present our preliminary results, and interpret these in the context
of the differences in the heights of formation of the lines.
Title: Direct Imaging by SDO/AIA of Quasi-periodic Propagating Fast
Mode Magnetosonic Waves of 2000 km/s in the Solar Corona
Authors: Liu, Wei; Title, A. M.; Zhao, J.; Ofman, L.; Schrijver,
C. J.; Aschwanden, M. J.; De Pontieu, B.; Tarbell, T. D.
Bibcode: 2011SPD....42.2114L
Altcode: 2011BAAS..43S.2114L
Quasi-periodic, propagating fast mode magnetosonic waves in the
corona were difficult to observe in the past due to relatively low
instrument cadences. We report here unprecedented evidence of such
waves directly imaged in EUV by the new SDO/AIA instrument. In the 2010
August 1 C3.2 flare/CME event, we find arc-shaped wave trains of 1-5%
intensity variations emanating near the flare kernel and propagating
outward along a funnel of coronal loops. Sinusoidal fits to a typical
wave train indicate a phase velocity of 2350 +/- 210 km/s. Similar
waves propagating in opposite directions are observed in closed loops
between two flare ribbons. In the k-omega diagram of the Fourier wave
power, we find a bright ridge that represents the dispersion relation
and can be well fitted with a straight line passing through the
origin, giving an equal phase and group velocity of 1630 +/- 760 km/s
averaged over the event. This k-omega ridge shows a broad frequency
distribution with prominent power at four non-harmonic frequencies,
5.5, 14.5, 25.1, and 37.9 mHz, among which the 14.5 mHz (period:
69 s) signal is the strongest. The signal at 5.5 mHz (period: 181 s,
same as chromospheric 3-minute oscillations) temporally coincides with
flare pulsations, suggesting a common origin of possibly quasi-periodic
magnetic reconnection. The instantaneous wave energy flux of (0.1-2.6)e7
ergs/cm2/s estimated at the coronal base is comparable to
the steady-state heating requirement of active region loops.
Title: Monitoring Image Alignments and Flat Fields for AIA/SDO
Data Images
Authors: Shine, Richard A.; Wolfson, C.; Boerner, P. F.; Tarbell,
T. D.; Nightingale, R. W.
Bibcode: 2011SPD....42.2126S
Altcode: 2011BAAS..43S.2126S
The images from the 4 telescopes on the Atmospheric Imaging Assembly
(AIA) on board the NASA Solar Dynamics Observatory (SDO) have different
offsets (from sun center), plate scales, and absolute rotations that
can be measured and corrected for accurate alignment. The most variable
of these is the offsets presumably due to small thermal flexings of
the telescopes. Here we describe the techniques used to make these
measurements and show how the image alignments vary with time. Weekly
measurements are made as part of the data monitoring that capture much
of the drift in the geometric corrections but shorter time variations
of typically a pixel also exist in the offsets. Angles and scales
have much better short term stability. We hope to eventually capture
these variations for the mission or at least provide software for
end users. We also describe progress made in determining flat
fields for the 10 wavebands and show how these have been varying over
the mission to date. This work was supported by NASA under the
SDO/AIA contract NNG04EA00C.
Title: Magneto-thermal convection in solar prominences
Authors: Berger, Thomas; Testa, Paola; Hillier, Andrew; Boerner, Paul;
Low, Boon Chye; Shibata, Kazunari; Schrijver, Carolus; Tarbell, Ted;
Title, Alan
Bibcode: 2011Natur.472..197B
Altcode:
Coronal cavities are large low-density regions formed by
hemispheric-scale magnetic flux ropes suspended in the Sun's outer
atmosphere. They evolve over time, eventually erupting as the dark
cores of coronal mass ejections. Although coronal mass ejections are
common and can significantly affect planetary magnetospheres, the
mechanisms by which cavities evolve to an eruptive state remain poorly
understood. Recent optical observations of high-latitude `polar crown'
prominences within coronal cavities reveal dark, low-density `bubbles'
that undergo Rayleigh-Taylor instabilities to form dark plumes rising
into overlying coronal cavities. These observations offered a possible
mechanism for coronal cavity evolution, although the nature of the
bubbles, particularly their buoyancy, was hitherto unclear. Here we
report simultaneous optical and extreme-ultraviolet observations of
polar crown prominences that show that these bubbles contain plasma at
temperatures in the range (2.5-12)×105 kelvin, which is
25-120 times hotter than the overlying prominence. This identifies a
source of the buoyancy, and suggests that the coronal cavity-prominence
system supports a novel form of magneto-thermal convection in the solar
atmosphere, challenging current hydromagnetic concepts of prominences
and their relation to coronal cavities.
Title: Chromospheric Jet and Growing "Loop" Observed by Hinode: New
Evidence of Fan-spine Magnetic Topology Resulting from Flux Emergence
Authors: Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell,
Theodore D.; Low, B. C.
Bibcode: 2011ApJ...728..103L
Altcode: 2010arXiv1012.1897L
We present observations of a chromospheric jet and growing "loop" system
that show new evidence of a fan-spine topology resulting from magnetic
flux emergence. This event, occurring in an equatorial coronal hole on
2007 February 9, was observed by the Hinode Solar Optical Telescope in
the Ca II H line in unprecedented detail. The predecessor of the jet is
a bundle of fine material threads that extend above the chromosphere and
appear to rotate about the bundle axis at ~50 km s-1 (period
lsim200 s). These rotations or transverse oscillations propagate upward
at velocities up to 786 km s-1. The bundle first slowly and
then rapidly swings up, with the transition occurring at the onset of an
A4.9 flare. A loop expands simultaneously in these two phases (velocity:
16-135 km s-1). Near the peak of the flare, the loop appears
to rupture; simultaneous upward ejecta and mass downflows faster than
free-fall appear in one of the loop legs. The material bundle then
swings back in a whip-like manner and develops into a collimated jet,
which is orientated along the inferred open-field lines with transverse
oscillations continuing at slower rates. Some material falls back along
smooth streamlines, showing no more oscillations. At low altitudes, the
streamlines bifurcate at presumably a magnetic null point and bypass
an inferred dome, depicting an inverted-Y geometry. These streamlines
closely match in space the late Ca II H loop and X-ray flare loop. These
observations are consistent with the model that flux emergence in an
open-field region leads to magnetic reconnection, forming a jet and
fan-spine topology. We propose that the material bundle and collimated
jet represent the outer spine in quasi-static and eruptive stages,
respectively, and the growing loop is a two-dimensional projection of
the three-dimensional fan surface.
Title: Early Results from the Atmospheric Imaging Assembly (AIA)
on the Solar Dynamics Observatory (SDO)
Authors: Tarbell, Theodore D.; AIA Team
Bibcode: 2011AAS...21715509T
Altcode: 2011BAAS...4315509T
SDO was launched on February 11, 2010, and first light was in late
March. AIA provides multiple simultaneous high-resolution full-disk
images of the corona and transition region up to 0.5 R above the solar
limb with 1.5" spatial resolution (0.6" pixels) and 10 second temporal
resolution. AIA consists of four telescopes that employ normal incidence
multilayer coated optics to provide narrow band imaging of seven EUV
band-passes centered on specific lines: Fe XVIII (94 A), Fe VIII, XX,
XXIII (131 A), Fe IX (171 A), Fe XII, XXIV (193 A), Fe XIV (211 A), He
II (304 A), and Fe XVI (335 A). One telescope observes C IV (1600 A)
and the nearby continuum (1700 A), and a filter that observes in the
visible enables coalignment with images from other telescopes. The
temperature diagnostics of the EUV emissions covers the range from
0.06M °K to 20M °K. Since early April, these images have been taken
nearly continuously, usually with a cadence of 12 seconds. Although
solar activity has only been increasing slowly in this cycle, there
have been a large number of filament ejections that interact with
large regions over the solar surface. In addition, because of the rapid
cadence of images, a number of new wave phenomena have been discovered
associated both with small flares and the interaction of expanding
magnetic structures with pre-existing structures. Movies illustrating
some of these events will be shown. AIA is supported by NASA (GSFC)
contract NNG04EA00C at the Lockheed Martin Advanced Technology Center.
Title: The Origins of Hot Plasma in the Solar Corona
Authors: De Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Boerner, P.; Martinez-Sykora, J.; Schrijver,
C. J.; Title, A. M.
Bibcode: 2011Sci...331...55D
Altcode:
The Sun's outer atmosphere, or corona, is heated to millions of degrees,
considerably hotter than its surface or photosphere. Explanations for
this enigma typically invoke the deposition in the corona of nonthermal
energy generated by magnetoconvection. However, the coronal heating
mechanism remains unknown. We used observations from the Solar Dynamics
Observatory and the Hinode solar physics mission to reveal a ubiquitous
coronal mass supply in which chromospheric plasma in fountainlike jets
or spicules is accelerated upward into the corona, with much of the
plasma heated to temperatures between ~0.02 and 0.1 million kelvin (MK)
and a small but sufficient fraction to temperatures above 1 MK. These
observations provide constraints on the coronal heating mechanism(s)
and highlight the importance of the interface region between photosphere
and corona.
Title: Flat Fielding and Image Alignments for AIA/SDO Data Images
Authors: Shine, R. A.; Nightingale, R. W.; Boerner, P.; Tarbell,
T. D.; Wolfson, C. J.
Bibcode: 2010AGUFMSH23C1872S
Altcode:
The Atmospheric Imaging Assembly (AIA) on the NASA Solar Dynamics
Observatory (SDO) takes 4096 by 4096 CCD images of the sun in 10
wavelengths utilizing 4 telescopes and each wavelength channel requires
a flat field that is applied shortly after receipt of the data on the
ground. Although some useful information about the CCD's was obtained
pre-launch, most of the flat field computation must be done with solar
images taken in orbit. Raw flat field images are collected as out of
focus images at 14 offsets using PZT adjustments on each telescope
and then each wavelength group is processed together using the Kuhn,
Lin, and Loranz (1991) flat field algorithm. However, the PZT motions
are restricted to about 14 arc sec limiting the measurement of large
scale variations. Hence larger offsets are also used by adjusting
the space craft pointing. All of these suffer from changes in the
solar image between exposures (especially the larger offsets), low
counts in some channels, and reflections in the UV channels. These
make direct use of the flats unfeasible and instead we process them to
compute 6 separable effects: 1) differences in the CCD quad gains and
inner row/column effects, 2) a repeating pattern across the CCD from
the manufacturing process (dubbed "tire tracks"), 3) a grid pattern
in the extreme ultraviolet wavelengths from the back filter, 4)
blemishes (some are translucent and some are treated as bad pixels),
5) large scale vignetting, and 6) all other variations. The last
category includes all remaining flat field effects after the others
are removed. This has not been done well for any of the wavelengths
yet. These effects will be described and illustrated, as will the
before and after images resulting from applying the processed flat
fields. We also describe techniques for fitting the solar limb to
accurately determine image centers and radii. This is not a trivial
problem for the extreme ultraviolet images but is required to align
images, determine relative plate scales, and monitor pointing variations
related to thermal changes. All channels except the He II 304A can be
now be routinely measured with an rms error of typically less than 0.2
arc sec. This allows us to easily see the radius variations during the
24 hour orbit for example. The computer code requires about 3 seconds
(single threaded) for each measurement. This work was supported by
NASA under the SDO/AIA contract NNG04EA00C.
Title: Coordinated observations of solar prominences with Hinode/SOT
and SDO/AIA
Authors: Berger, T. E.; Tarbell, T. D.; Schrijver, C. J.; Title,
A. M.; Boerner, P.; Shine, R. A.
Bibcode: 2010AGUFMSH21C..04B
Altcode:
We show the first detailed study of a solar quiescent prominence
using simultaneous observations from the Hinode/SOT and SDO/AIA
instruments. The prominence studied is a polar crown prominence
located at the base of a large coronal cavity on the NW solar limb on
22-June-2010. Hinode observed the prominence for 2.75 hours running
the HOP 73 prominence observation program to acquire Ca II H-line
filtergrams and H-alpha doppler observations at a 20-second cadence. SOT
observations in Ca II H-line and H-alpha spectral lines reveal the
common dynamics of filamentary downflows and large-scale oscillations
of the prominence body. In addition a dark cavity is observed to
rise into the prominence and stagnate before going unstable to form
Rayleigh-Taylor plume upflows. AIA observations in the 304, 171, 193,
and 211 channels with 14 second cadence reveal that both the cavity
and the plume upflows are bright in these hotter passbands. Filter
ratio measurements as well as preliminary EM estimates imply that
the cavity and plume plasma temperature is at least 10^6 K. Plasma at
this temperature has never been detected or theorized in a confined
configuration in the lower chromosphere below a prominence. Assuming
an electron number density of 3e09 cm-3, the balance between thermal
pressure in the cavity and magnetic pressure in the overlying prominence
implies a magnetic flux density of order 10 gauss, in line with earlier
measurements of prominence magnetic fields. However the cavity likely
contains a significant magnetic energy density of its own implying that
the prominence magnetic fields may need to be significantly higher to
balance the cavity buoyancy. The existence of 10^6 K plasma confined
below a quiescent prominence and the subsequent onset of buoyancy
instabilities present new challenges to theories of prominence and
coronal cavity formation and suggest new avenues for supply of mass
and magnetic flux to the associated coronal cavity systems that make
up the bulk of CMEs. Hinode/SOT Ca II H-line image overlain on SDO/AIA
304A image of a quiescent solar prominence.
Title: First results for the Solar Ultraviolet Magnetograph
Investigation (SUMI)
Authors: Moore, R. L.; Cirtain, J. W.; West, E.; Kobayashi, K.;
Robinson, B.; Winebarger, A. R.; Tarbell, T. D.; de Pontieu, B.;
McIntosh, S. W.
Bibcode: 2010AGUFMSH11B1655M
Altcode:
On July 31, 2010 SUMI was launched to 286km above the White
Sands Missile Range to observe active region 11092. SUMI is a
spectro-polarimeter capable of measuring the spectrum for Mg II h &
k at 280 nm and C IV at 155 nm. Simultaneous observations with Hinode
and SDO provide total coverage of the region from the photosphere into
the corona, a very unique and original data set. We will present the
initial results from this first flight of the experiment and demonstrate
the utility of further observations by SUMI.
Title: First SDO/AIA Observations of Global Coronal EUV "Waves":
Multiple Components and "Ripples"
Authors: Liu, W.; Nitta, N. V.; Schrijver, C. J.; Title, A. M.;
Tarbell, T. D.
Bibcode: 2010AGUFMSH13A..07L
Altcode:
Global coronal EUV disturbances (so-called "EIT waves") are useful
diagnostics for physical conditions on the Sun. Major drawbacks that
hindered our understanding of this phenomenon were previous instruments'
single view point, low cadence (e.g., 12 minutes of EIT), and limited
wavelength coverage. The Atmospheric Imaging Assembly (AIA) on board
the Solar Dynamics Observatory (SDO) observes the full-sun corona
at 10 EUV and UV wavelengths, covering a wide range of temperatures,
with high resolution (1.4") and cadence (up to 12 s). It thus offers a
great chance to end the decade long debate on the nature of global EUV
"waves". We present here the first AIA observations of such phenomenon
on 2010 April 8 revealed in unprecedented detail and discuss their
physical implications. The disturbance exhibits two components: one
weak, diffuse pulse superimposed by multiple strong, sharp fronts,
which again have slow and fast components. The disturbance originates
in front of erupting coronal loops and the slow sharp front undergoes
acceleration, both implying the disturbance being driven by the
coronal mass ejection (CME). Even at a 20 s cadence, the diffuse pulse
propagates at a surprisingly constant velocity of ~200 km/s, weakly
dependent on direction. The fast sharp front overtakes the slow front,
producing multiple "ripples" and steepening of the local pulse, and both
fronts propagate independently afterwards. These resemble the nature
of real waves. Unexpectedly, the amplitude and FWHM of the diffuse
pulse decreases linearly with distance. The diffuse pulse appears as
emission enhancement at hotter 193 Å but reduction at cooler 171 Å,
suggestive of heating, while the sharp fronts appear as enhancement at
both wavelengths, indicating density increase. As evidence for both
wave and non-wave models of "EIT waves" has been found, we suggest
that a hybrid model combining both mechanisms (e.g., Cohen et al. 2010)
may best explaine the data. In addition to the global EUV disturbance,
we found fast (600-1100 km/s) features repeated at 100 s intervals
as tentative evidence of fast mode MHD waves. Discoveries of the fast
features, multiple ripples, and two-component fronts were made possible
for the first time thanks to AIA's high cadences and sensitivities.
Title: The role of the chromosphere in filling the corona with hot
plasma (Invited)
Authors: de Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Boerner, P.; Martinez-Sykora, J.; Schrijver,
C. J.; Title, A. M.
Bibcode: 2010AGUFMSH21C..03D
Altcode:
We use coordinated observations from the Solar Dynamics Observatory
(SDO), Hinode and the Swedish Solar Telescope (SST) to show how
plasma is heated to coronal temperatures from its source in the
chromosphere. Our observations reveal a ubiquitous mass supply
for the solar corona in which chromospheric plasma is accelerated
upward into the corona with much of the plasma heated to transition
region temperatures, and a small, but significant fraction heated
to temperatures in excess of 1 million K. Our observations show,
for the first time, how chromospheric spicules, fountain-like jets
that have long been considered potential candidates for coronal
heating, are directly associated with heating of plasma to coronal
temperatures. These results provide strong physical constraints on
the mechanism(s) responsible for coronal heating and do not seem
compatible with current models. The association with chromospheric
spicules highlights the importance of the interface region between
the photosphere and corona to gain a full understanding of the coronal
heating problem.
Title: Observation of Plasma Instabilities in Quiescent Prominences
Authors: Ryutova, M.; Berger, T.; Frank, Z.; Tarbell, T.; Title, A.
Bibcode: 2010SoPh..267...75R
Altcode: 2010SoPh..tmp..170R
We study dynamics of quiescent prominences using several data sets taken
with the Solar Optical Telescope (SOT) on Hinode. We find a number of
processes occurring at different stages of prominence evolution that
are common for all of our chosen cases and, having universal character,
can be related to fundamental plasma instabilities. We combine the
observational evidence and theory to identify these instabilities. Here
we discuss three examples: i) prominence cavity formation and its
evolution, associated with a screw-pinch instability; ii) development
of a regular series of plumes and spikes typical to the Rayleigh -
Taylor (RT) instability; and iii) the appearance of growing ripples at
the prominence/corona interface, often followed by a sudden collimated
mass upflow, attributed to the Kelvin - Helmholtz (KH) instability. The
conditions for transition from a linear (rippling mode) to nonlinear
stage of the KH instability, known to have an explosive character,
are specified. Given excellent Hinode data, all three aspects of
prominence dynamics allow quantitative analysis.
Title: First SDO AIA Observations of a Global Coronal EUV "Wave":
Multiple Components and "Ripples"
Authors: Liu, Wei; Nitta, Nariaki V.; Schrijver, Carolus J.; Title,
Alan M.; Tarbell, Theodore D.
Bibcode: 2010ApJ...723L..53L
Altcode: 2012arXiv1201.0815L
We present the first Solar Dynamics Observatory Atmospheric Imaging
Assembly (AIA) observations of a global coronal EUV disturbance
(so-called "EIT wave") revealed in unprecedented detail. The disturbance
observed on 2010 April 8 exhibits two components: one diffuse pulse
superimposed, on which are multiple sharp fronts that have slow and
fast components. The disturbance originates in front of erupting coronal
loops and some sharp fronts undergo accelerations, both effects implying
that the disturbance is driven by a coronal mass ejection. The diffuse
pulse, propagating at a uniform velocity of 204-238 km s-1
with very little angular dependence within its extent in the south,
maintains its coherence and stable profile for ~30 minutes. Its arrival
at increasing distances coincides with the onsets of loop expansions and
the slow sharp front. The fast sharp front overtakes the slow front,
producing multiple "ripples" and steepening the local pulse, and both
fronts propagate independently afterward. This behavior resembles
the nature of real waves. Unexpectedly, the amplitude and FWHM of
the diffuse pulse decrease linearly with distance. A hybrid model,
combining both wave and non-wave components, can explain many, but
not all, of the observations. Discoveries of the two-component fronts
and multiple ripples were made possible for the first time thanks to
AIA's high cadences (<=20 s) and high signal-to-noise ratio.
Title: Hinode Observation of Photospheric Magnetic Activities
Triggering X-ray Microflares Around a Well-developed Sunspot
Authors: Kano, R.; Shimizu, T.; Tarbell, T. D.
Bibcode: 2010ApJ...720.1136K
Altcode:
Microflares, which are small energetic events in the solar corona, are
an example of dynamical phenomena suitable for understanding energy
release processes in the solar corona. We identified 55 microflares
around a well-developed sunspot surrounded by a moat with high-cadence
X-ray images from the Hinode X-ray Telescope, and searched for their
photospheric counterparts in line-of-sight magnetograms taken with the
Hinode Solar Optical Telescope. We found opposite magnetic polarities
encountering each other around the footpoints of 28 microflares,
while we could not find such encounters around the footpoints of the
other 27 microflares. Emerging magnetic fluxes in the moat were the
dominant origin causing the encounters of opposite polarities (21 of
28 events). Unipolar moving magnetic features (MMFs) with negative
polarities the same as the sunspot definitely caused the encounters of
opposite polarities for five microflares. The decrease of magnetic flux,
i.e., magnetic flux cancellation, was confirmed at the encountering site
in typical examples of microflares. Microflares were not isotropically
distributed around the spot; the microflares with emerging magnetic
fluxes (EMFs) were observed in the direction where magnetic islands
with the same polarity as the spot were located at the outer boundary
of the moat, while the microflares with negative MMFs were observed
in the direction where magnetic islands with polarity opposite to the
spot were located at the outer boundary of the moat. We also found that
EMFs in the moat had a unique orientation in which those with the same
polarity as the spot is closer to the spot than the other one that had
the opposite polarity to the spot. These observational results lead
to two magnetic configurations including magnetic reconnection for
triggering energy release at least in half of the microflares around
the spot, and suggest that the global magnetic structures around the
spot strongly affect what kinds of polarity encounters are formed in
the sunspot moat.
Title: Emergence of Helical Flux and the Formation of an Active
Region Filament Channel
Authors: Lites, B. W.; Kubo, M.; Berger, T.; Frank, Z.; Shine, R.;
Tarbell, T.; Title, A.; Okamoto, T. J.; Otsuji, K.
Bibcode: 2010ApJ...718..474L
Altcode:
We present comprehensive observations of the formation and evolution
of a filament channel within NOAA Active Region (AR) 10978 from
Hinode/Solar Optical Telescope and TRACE. We employ sequences
of Hinode spectro-polarimeter maps of the AR, accompanying Hinode
Narrowband Filter Instrument magnetograms in the Na I D1 line, Hinode
Broadband Filter Instrument filtergrams in the Ca II H line and G-band,
Hinode X-ray telescope X-ray images, and TRACE Fe IX 171 Å image
sequences. The development of the channel resembles qualitatively
that presented by Okamoto et al. in that many indicators point to
the emergence of a pre-existing sub-surface magnetic flux rope. The
consolidation of the filament channel into a coherent structure takes
place rapidly during the course of a few hours, and the filament form
then gradually shrinks in width over the following two days. Particular
to this filament channel is the observation of a segment along its
length of horizontal, weak (500 G) flux that, unlike the rest of the
filament channel, is not immediately flanked by strong vertical plage
fields of opposite polarity on each side of the filament. Because this
isolated horizontal field is observed in photospheric lines, we infer
that it is unlikely that the channel formed as a result of reconnection
in the corona, but the low values of inferred magnetic fill fraction
along the entire length of the filament channel suggest that the bulk
of the field resides somewhat above the low photosphere. Correlation
tracking of granulation in the G band presents no evidence for either
systematic flows toward the channel or systematic shear flows along
it. The absence of these flows, along with other indications of these
data from multiple sources, reinforces (but does not conclusively
demonstrate) the picture of an emerging flux rope as the origin of
this AR filament channel.
Title: Quiescent Prominence Dynamics Observed with the Hinode Solar
Optical Telescope. I. Turbulent Upflow Plumes
Authors: Berger, Thomas E.; Slater, Gregory; Hurlburt, Neal; Shine,
Richard; Tarbell, Theodore; Title, Alan; Lites, Bruce W.; Okamoto,
Takenori J.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Magara, Tetsuya;
Suematsu, Yoshinori; Shimizu, Toshifumi
Bibcode: 2010ApJ...716.1288B
Altcode:
Hinode/Solar Optical Telescope (SOT) observations reveal two new
dynamic modes in quiescent solar prominences: large-scale (20-50 Mm)
"arches" or "bubbles" that "inflate" from below into prominences, and
smaller-scale (2-6 Mm) dark turbulent upflows. These novel dynamics are
related in that they are always dark in visible-light spectral bands,
they rise through the bright prominence emission with approximately
constant speeds, and the small-scale upflows are sometimes observed to
emanate from the top of the larger bubbles. Here we present detailed
kinematic measurements of the small-scale turbulent upflows seen in
several prominences in the SOT database. The dark upflows typically
initiate vertically from 5 to 10 Mm wide dark cavities between the
bottom of the prominence and the top of the chromospheric spicule
layer. Small perturbations on the order of 1 Mm or less in size
grow on the upper boundaries of cavities to generate plumes up to
4-6 Mm across at their largest widths. All plumes develop highly
turbulent profiles, including occasional Kelvin-Helmholtz vortex
"roll-up" of the leading edge. The flows typically rise 10-15 Mm before
decelerating to equilibrium. We measure the flowfield characteristics
with a manual tracing method and with the Nonlinear Affine Velocity
Estimator (NAVE) "optical flow" code to derive velocity, acceleration,
lifetime, and height data for several representative plumes. Maximum
initial speeds are in the range of 20-30 km s-1, which
is supersonic for a ~10,000 K plasma. The plumes decelerate in the
final few Mm of their trajectories resulting in mean ascent speeds
of 13-17 km s-1. Typical lifetimes range from 300 to 1000
s (~5-15 minutes). The area growth rate of the plumes (observed as
two-dimensional objects in the plane of the sky) is initially linear
and ranges from 20,000 to 30,000 km2 s-1 reaching
maximum projected areas from 2 to 15 Mm2. Maximum contrast of
the dark flows relative to the bright prominence plasma in SOT images
is negative and ranges from -10% for smaller flows to -50% for larger
flows. Passive scalar "cork movies" derived from NAVE measurements show
that prominence plasma is entrained by the upflows, helping to counter
the ubiquitous downflow streams in the prominence. Plume formation
shows no clear temporal periodicity. However, it is common to find
"active cavities" beneath prominences that can spawn many upflows in
succession before going dormant. The mean flow recurrence time in these
active locations is roughly 300-500 s (5-8 minutes). Locations remain
active on timescales of tens of minutes up to several hours. Using a
column density ratio measurement and reasonable assumptions on plume
and prominence geometries, we estimate that the mass density in the
dark cavities is at most 20% of the visible prominence density, implying
that a single large plume could supply up to 1% of the mass of a typical
quiescent prominence. We hypothesize that the plumes are generated from
a Rayleigh-Taylor instability taking place on the boundary between
the buoyant cavities and the overlying prominence. Characteristics,
such as plume size and frequency, may be modulated by the strength
and direction of the cavity magnetic field relative to the prominence
magnetic field. We conclude that buoyant plumes are a source of
quiescent prominence mass as well as a mechanism by which prominence
plasma is advected upward, countering constant gravitational drainage.
Title: Fundamental Solar Physics Results from Hinode and the Solar
Dynamics Obervatory
Authors: Tarbell, Theodore D.
Bibcode: 2010AAS...21610601T
Altcode:
Hinode is the most technologically advanced solar observatory ever operated in space. It contains three instruments that provide major
improvements in spatial, temporal and spectral resolution over
previous solar space instruments. In its 3-year prime mission (starting November, 2006) during low levels of solar activity, observations have resulted in greatly improved understanding of the
interaction between convection and the solar magnetic fields and
new insights into the mechanisms that heat the solar atmosphere
and produce the UV and X-ray emission. Hinode results cover a
wide range of scientific issues that include the local solar
dynamo, evidence for the convective origin of sunspot penumbrae,
the ubiquity of jets formed by magnetic reconnection in the low
solar atmosphere, the presence of strong Alfven waves in the
chromosphere and corona with enough power to drive the solar
wind, measurements of the free energy powering solar eruptions,
direct observations of current sheets formed by Petschek-like
reconnection driving CMEs, the presence of pervasive, impulsive
heating events in active regions that constrain coronal heating
models, and persistent outflows at the edges of active regions that provide mass and energy to the solar wind. Solar Dynamics Observatory (SDO), launched in February, 2010, has full disk imagers
with very high cadence to study the causes and predictability of
solar variability. In some important ways, Hinode will function
as the ``microscope,'' both in spatial and spectral resolution,
for SDO, just as TRACE did for SOHO. Some initial examples of
joint observations will be shown.
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.
Bibcode: 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: Direct Imaging of an Emerging Flux Rope and a Resulting
Chromospheric Jet Observed by Hinode
Authors: Liu, Wei; Berger, T.; Title, A. M.; Tarbell, T. D.; DeRosa, M.
Bibcode: 2010AAS...21640307L
Altcode: 2010BAAS...41R.878L
Magnetic flux emergence has been traditionally observed on the disk by
identifying changes in magnetograms. Observations near the limb offer
an alternative perspective and allow direct imaging of emerging flux
ropes. We present Hinode/SOT Ca II H observations of such an event in
an equatorial coronal hole on 2007 February 9. The precursor of the
event was a bundle of fine material threads that extended at an oblique
angle above the chromosphere and appeared to rotate about a common
axis. This bundle first slowly and then rapidly swung up, accompanied
by a loop that appeared at the base of the bundle and expanded at
comparable rates. During the first (slow rise) stage, the apex of the
loop ascended at 16 km/s, a velocity similar to that of H-alpha arch
filaments (e.g., Chou & Zirin) and of emerging flux ropes expanding
into the corona as found in MHD simulations (e.g., Fan & Gibson;
Martinez-Sykora). The second stage started at the onset of a GOES A5
flare and the loop expansion accelerated, reaching a velocity of 130
km/s when the loop appeared to rupture near the peak of the flare. The
material bundle then swung back in a whiplike manner and developed into
a collimated jet, exhibiting oscillatory transverse motions across its
axis, as expected from unwinding twists. Some jet material fell back
along smooth streamlines, which bypass an unseen dome and presumably
a null point in the low corona, depicting an inverted-Y shape. Some
of these observations resemble the model (e.g., Uchida & Shibata)
of the emergence of a twisted flux rope into an open field region that
leads to reconnection and formation of a jet. Some observations are,
however, not predicted in previous models and we will discuss their
implications.
Title: High frequency waves in the solar atmosphere?.
Authors: Fleck, B.; Straus, T.; Carlsson, M.; Jefferies, S. M.;
Severino, G.; Tarbell, T. D.
Bibcode: 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 0o 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 CO5BOLD). 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 detection of fast moving upflows in the quiet solar
photosphere.
Authors: Straus, Th.; Fleck, B.; Jefferies, S. M.; Carlsson, M.;
Tarbell, T. D.
Bibcode: 2010MmSAI..81..751S
Altcode: 2010arXiv1002.3305S
In our studies of the dynamics and energetics of the solar atmosphere,
we have detected, in high-quality observations from Hinode SOT/NFI,
ubiquitous small-scale upflows which move horizontally with supersonic
velocities in the quiet Sun. We present the properties of these fast
moving upflows (FMUs) and discuss different interpretations.
Title: Joint STEREO-Hinode Observations of Coronal Dimming and Waves
Associated with a CME/Flare Event
Authors: Nitta, Nariaki; Aschwanden, Markus; Frank, Zoe; Slater,
Gregory; Tarbell, Theodore; Zarro, Dominic
Bibcode: 2010cosp...38.2928N
Altcode: 2010cosp.meet.2928N
During the solar minimum between cycles 23 and 24, a number of
minor flares from unimpressive active regions were associated with
large-scale dimming and waves as observed by the EUV Imager (EUVI) on
STEREO. We present a detailed study on one of the CME/flare events that
was observed also by the instruments on Hinode. We analyze SOT Ca II
data to explore the origin of the disturbances and EIS slit spectra to
determine the timings of the upflow and associated turbulence that are
presumably correlated with coronal dimming. The sequence of phenomena
as captured by different instruments on STEREO, Hinode and SOHO helps
us identify the key physical processes that gave rise to the event.
Title: Travel-Time Analyses of an Emerging-Flux Region
Authors: Nagashima, K.; Sekii, T.; Kosovichev, A. G.; Zhao, J.;
Tarbell, T. D.
Bibcode: 2009ASPC..415..417N
Altcode:
Travel-time analyses of a newly-formed plage region are presented. The
dataset has been obtained from the 12-hr Hinode observation of an
emerging-flux region (to be NOAA AR 10975) close to the disc center
on 23 November 2007. The SOT provides data in Ca II H line and in
Fe I 557.6nm line; we use both chromospheric intensity oscillation
data and photospheric Dopplergrams for travel-time measurement by
a cross-correlation method. In the plage region, we have detected
a travel-time anomaly in the chromospheric data, but not in the
photospheric data. This can be interpreted as a signature of downflows
in the chromosphere. This result illustrates how time-distance
techniques can be used to study chromospheric flows.
Title: An Intriguing Chromospheric Jet Observed by Hinode: Fine
Structure Kinematics and Evidence of Unwinding Twists
Authors: Liu, Wei; Berger, Thomas E.; Title, Alan M.; Tarbell,
Theodore D.
Bibcode: 2009ApJ...707L..37L
Altcode: 2009arXiv0910.5186L
We report a chromospheric jet lasting for more than 1 hr observed by
the Hinode Solar Optical Telescope in unprecedented detail. The ejection
occurred in three episodes separated by 12-14 minutes, with the amount
and velocity of material decreasing with time. The upward velocities
range from 438 to 33 km\nolimits s\nolimits ^{-1}, while the downward
velocities of the material falling back have smaller values (mean:
-56 km\nolimits s\nolimits ^{-1}) and a narrower distribution (standard
deviation: 14 km\nolimits s\nolimits ^{-1}). The average acceleration
inferred from parabolic spacetime tracks is 141 m\nolimits s^{-2}, a
fraction of the solar gravitational acceleration. The jet consists of
fine threads (0farcs5-2'' wide), which exhibit coherent, oscillatory
transverse motions perpendicular to the jet axis and about a common
equilibrium position. These motions propagate upward along the jet,
with the maximum phase speed of 744 ± 11 km\nolimits s\nolimits ^{-1}
at the leading front of the jet. The transverse oscillation velocities
range from 151 to 26 km\nolimits s\nolimits ^{-1}, amplitudes from
6.0 to 1.9 Mm\nolimits, and periods from 250 to 536 s\nolimits. The
oscillations slow down with time and cease when the material starts to
fall back. The falling material travels along almost straight lines in
the original direction of ascent, showing no transverse motions. These
observations are consistent with the scenario that the jet involves
untwisting helical threads, which rotate about the axis of a single
large cylinder and shed magnetic helicity into the upper atmosphere.
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.
Bibcode: 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: Helical Shape and Twisting Motion as Intrinsic Properties of
Penumbral Filaments
Authors: Shine, R. A.; Ryutova, M.; Berger, T. E.; Title, A. M.;
Tarbell, T. D.; Ichimoto, K.
Bibcode: 2009AGUFMSH23B1541S
Altcode:
A wealth of high resolution data obtained with advanced ground based
telescopes and the SOT instrument on HINODE have led to new findings
in the properties of penumbral filaments and controversies in their
interpretation. Here we address one such issue, namely the question of
whether the apparent twist of filaments is real or is just a viewing
effect. We show that the helical shape and twisting motions of penumbral
filaments follow from first principles and represent an integral part of
penumbra formation and dynamics. As such, these properties link together
other observed features of filaments including their magnetic and
thermal substructure and their impact on the overlying atmosphere. At
all stages of penumbral dynamics, qualitative agreement of theory and
observations is supported by quantitative analysis as well.
Title: Role of the Resistive and Thermal Instabilities in Dynamics
of Quiescent Prominences
Authors: Frank, Z.; Ryutova, M.; Berger, T. E.; Title, A. M.; Tarbell,
T. D.
Bibcode: 2009AGUFMSH41B1653F
Altcode:
We present the observations taken with the SOT instrument on Hinode in
G-band and Ca H lines. High cadence data compiled in movies show clear
evidence for several fundamental plasma instabilities. We combine
the observational evidence and theoretical estimates to identify
these instabilities. The following can be given as examples. (1)
An analogue of the Kelvin-Helmholtz instability develops at the
prominence/corona interface that manifests itself in growing ripples
during a linear growth phase and may be followed by a nonlinear stage
taking the form of an explosive instability corresponding to a CME
ejection. This instability also includes the regime of "smoke ring"
formation. (2) The appearence of "bubbles and spikes" typical to
the Rayleigh-Taylor instability are observed. Their evolution and
growth rates are found to be modified by both poloidal and toroidal
components of magnetic field. (3) A resistive interchange instability,
associated with an "unfavorable" magnetic field curvature relative to
the density/temperature gradients, may be responsible for a hot barb
formation, its evolution and collapse.
Title: Fine Structures and Kinematics of an Intriguing Chromospheric
Jet Observed by Hinode Solar Optical Telescope
Authors: Liu, W.; Berger, T. E.; Title, A. M.; Tarbell, T. D.
Bibcode: 2009AGUFMSH51A1266L
Altcode:
Transient, small-scale ejections of plasma from the lower atmosphere
are common manifestations of solar activity. Hinode, with its superior
resolutions, has spurred renewed interest in solar jets since its
launch. Here we report a chromospheric jet lasting for more than 1
hr on 2007 February 9 observed by the Hinode Solar Optical Telescope
(SOT) in unprecedented detail. SOT Ca II H passband observations
at high resolution of 0.2 arcsecond and cadence of 8 s allowed us to
investigate the fine structures and kinematics of the jet. The ejection
occurred in three episodes, rather than continuously, with the amount
and velocity of material decreasing with time. The upward velocities
along the jet range from ~440 to ~30 km/s, while the downward velocities
of the material falling back have much smaller values (mean: -60 km/s)
and a narrower distribution. Some tracks in the space-time plot clearly
show parabolic shapes and the inferred acceleration is a fraction of
the solar gravitational acceleration. The jet consists of fine threads
(0.5-2 arcsecond wide), which exhibit coherent, oscillatory transverse
motions perpendicular to the jet axis and about a common equilibrium
position. These motions propagate upward, with the maximum phase speed
of ~740 km/s found at the leading front of the jet. The transverse
oscillation velocities range from 150 to 30 km/s, amplitudes from 6 to 2
Mm, and periods from 250 to 550 s. The oscillations slow down with time
and cease when the material starts to fall back. The falling material
travels along almost straight lines in the original direction of ascent,
showing no transverse motions. These observations are consistent with
the models suggested by Shibata & Uchida (1985) and Canfield et
al. (1996). In this scenario, the jet involves untwisting helical
threads, which rotate about the axis of a single large cylinder and
shed magnetic helicity into the upper atmosphere. Implications of this
event in the context of multiwavelength data in H-alpha, EUV, and X-rays
will be discussed. A chromospheric jet observed by Hinode SOT in the
Ca II H passband (T=1-2×10 4 K). Note the helical-like fine threads.
Title: Solar Surface Emerging Flux Regions: A Comparative Study of
Radiative MHD Modeling and Hinode SOT Observations
Authors: Cheung, M.; Schüssler, M.; Tarbell, T. D.; Title, A. M.
Bibcode: 2009ASPC..415...79C
Altcode:
We present results from three-dimensional radiative MHD simulations
of the rise of buoyant magnetic flux tubes through the convection
zone and into the photosphere. Due to the strong stratification
of the convection zone, the rise results in a lateral expansion
of the tube into a magnetic sheet, which acts as a reservoir for
small-scale flux emergence events at the scale of granulation. The
interaction of the convective downflows and the rising magnetic flux
tube undulates it to form serpentine field lines that emerge into the
photosphere. Observational characteristics of the simulated emerging
flux regions are discussed in the context of new observations from
Hinode SOT.
Title: Origin of Filamentary Structures and Flows in Quiescent
Prominences
Authors: Ryutova, M.; Berger, T. E.; Tarbell, T. D.; Frank, Z.; Title,
A. M.
Bibcode: 2009AGUFMSH23B1540R
Altcode:
The paradox of fine vertical structure has usually referred to an
apparent contradiction met when comparing vertical fine structures
of quiescent prominences observed on the limb with the necessary
horizontal magnetic field along their long axis. In addition to this
fundamental problem, the very formation of fine vertical structures
has been a long standing puzzle. Here we address these problems and
show that considering the global structure of a prominence as a large
scale skewed formation with toroidal and poloidal fields removes the
paradox and allows derivation of dynamic stability criteria. This also
includes the mechanism of the fine structure formation and peculiarities
of downward mass motions. Theoretical estimates of key parameters
are compared with the observations taken with the SOT instrument
on Hinode. We find results of comparison very encouraging. For the
approximate 3D reconstruction of the general shape of prominences,
the STEREO A and B images have been used.
Title: A New View of Fine Scale Dynamics and Magnetism of Sunspots
Revealed by Hinode/SOT
Authors: Ichimoto, K.; Suematsu, Y.; Katsukawa, Y.; Tsuneta, S.;
Shimojo, M.; Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Berger, T.;
Title, A. M.; Lites, B. W.; Kubo, M.; Yokoyama, T.; Nagata, S.
Bibcode: 2009ASPC..405..167I
Altcode:
The Solar Optical Telescope on-board Hinode is providing a new view of
the fine scale dynamics in sunspots with its high spatial resolution and
unprecedented image stability. We present three features related to the
Evershed flow each of which raises a new puzzle in sunspot dynamics;
i.e., twisting appearance of penumbral filaments, the source and sink
of individual Evershed flow channels, and the net circular polarization
in penumbrae with its spatial relation to the Evershed flow channels.
Title: Has Hinode Revealed the Missing Turbulent Flux of the
Quiet Sun?
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A. M.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2009ASPC..405..173L
Altcode:
The Hinode Spectro-Polarimeter has revealed the presence of surprisingly
strong horizontal magnetic fields nearly everywhere in the quiet
solar atmosphere. These horizontal fields, along with measures of the
vertical fields, may be the signature of the ``hidden turbulent flux''
of the quiet Sun. The measured horizontal fields average at least to
55 Gauss: nearly 5 times that of the measured longitudinal apparent
flux density. The nature of these fields are reviewed, and discussed
in the light of recent magneto-convection numerical simulations of
the quiet Sun.
Title: Hinode Observation of the Magnetic Fields in a Sunspot Light
Bridge Accompanied by Long-Lasting Chromospheric Plasma Ejections
Authors: Shimizu, Toshifumi; Katsukawa, Yukio; Kubo, Masahito; Lites,
Bruce W.; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Tsuneta, Saku;
Nagata, Shin'ichi; Shine, Richard A.; Tarbell, Theodore D.
Bibcode: 2009ApJ...696L..66S
Altcode:
We present high-resolution magnetic field measurements of a sunspot
light bridge (LB) that produced chromospheric plasma ejections
intermittently and recurrently for more than 1 day. The observations
were carried out with the Hinode Solar Optical Telescope on 2007
April 29 and 30. The spectro-polarimeter reveals obliquely oriented
magnetic fields with vertical electric current density higher than
100 mA m-2 along the LB. The observations suggest that
current-carrying highly twisted magnetic flux tubes are trapped below
a cusp-shaped magnetic structure along the LB. The presence of trapped
current-carrying flux tubes is essential for causing long-lasting
chromospheric plasma ejections at the interface with pre-existing
vertically oriented umbral fields. A bidirectional jet was clearly
detected, suggesting magnetic reconnections occurring at very low
altitudes, slightly above the height where the vector magnetic fields
are measured. Moreover, we found another strong vertical electric
current on the interface between the current-carrying flux tube
and pre-existing umbral field, which might be a direct detection
of the currents flowing in the current sheet formed at the magnetic
reconnection sites.
Title: Magnetic Feature Tracking in Sunspot Moats Using Hinode/SOT
Observations
Authors: Hagenaar-Daggett, Hermance J.; Shine, R. A.; Tarbell, T. D.
Bibcode: 2009SPD....40.0908H
Altcode:
A long series of continuous observations of NOAA AR 10933 taken
by Hinode/SOT from 2-4 January, 2007 is used to study MMF's (moving
magnetic features) in the periphery of the large sunspot in the region
and its surrounding moat. We describe some algorithms we have developed
to quickly recognize and track discrete features and apply these to
the magnetic structures seen in Na I 589.6nm Stokes V images. Because
the features evolve and show variable visibilty, automatic tracking is
not always successful even with the seeing free Hinode images and we
are still attempting to improve our techniques. We also compute flow
maps from the photospheric G band images using LCT (local correlation
tracking) to compare with the generally faster MMF motions. This
work was supported by NASA contract NNM07AA01C.
Title: Recent Advances in Understanding Magnetic Fields in the
Quiet Sun
Authors: Tarbell, Theodore D.
Bibcode: 2009SPD....40.0501T
Altcode:
I will describe recent advances in our understanding of magnetic fields
in the quiet sun. These have been developed both from high resolution
observations made by the Hinode Solar Optical Telescope and ground-based
observatories and from increasingly realistic three-dimensional MHD
models of the upper convection zone and atmosphere. Examples of flux
emergence, evolution, transport and disappearance are included. Some
observational and theoretical problems in relating the photospheric
fields to the upper atmosphere are discussed. This work is
supported by the NASA Hinode contract with the Lockheed Martin Advanced
Technology Center.
Title: Prominence Formation Associated with an Emerging Helical
Flux Rope
Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo,
Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2009ApJ...697..913O
Altcode: 2009arXiv0904.0007O
The formation and evolution process and magnetic configuration of
solar prominences remain unclear. In order to study the formation
process of prominences, we examine continuous observations of a
prominence in NOAA AR 10953 with the Solar Optical Telescope on
the Hinode satellite. As reported in our previous Letter, we find
a signature suggesting that a helical flux rope emerges from below
the photosphere under a pre-existing prominence. Here we investigate
more detailed properties and photospheric indications of the emerging
helical flux rope, and discuss their relationship to the formation of
the prominence. Our main conclusions are: (1) a dark region with absence
of strong vertical magnetic fields broadens and then narrows in Ca II
H-line filtergrams. This phenomenon is consistent with the emergence
of the helical flux rope as photospheric counterparts. The size of the
flux rope is roughly 30,000 km long and 10,000 km wide. The width is
larger than that of the prominence. (2) No shear motion or converging
flows are detected, but we find diverging flows such as mesogranules
along the polarity inversion line. The presence of mesogranules may
be related to the emergence of the helical flux rope. (3) The emerging
helical flux rope reconnects with magnetic fields of the pre-existing
prominence to stabilize the prominence for the next several days. We
thus conjecture that prominence coronal magnetic fields emerge in
the form of helical flux ropes that contribute to the formation and
maintenance of the prominence.
Title: On The Interpretation Of Hinode NFI Filtergrams
Authors: Fleck, Bernard; Straus, T.; Jefferies, S. M.; Severino, G.;
Tarbell, T. D.
Bibcode: 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: Helioseismic Signature of Chromospheric Downflows in Acoustic
Travel-Time Measurements From Hinode
Authors: Nagashima, Kaori; Sekii, Takashi; Kosovichev, Alexander G.;
Zhao, Junwei; Tarbell, Theodore D.
Bibcode: 2009ApJ...694L.115N
Altcode: 2009arXiv0903.1323N
We report on a signature of chromospheric downflows in two emerging
flux regions detected by time-distance helioseismology analysis. We
use both chromospheric intensity oscillation data in the Ca II H line
and photospheric Dopplergrams in the Fe I 557.6 nm line obtained
by Hinode/SOT for our analyses. By cross-correlating the Ca II
oscillation signals, we have detected a travel-time anomaly in the
plage regions; outward travel times are shorter than inward travel
times by 0.5-1 minute. However, such an anomaly is absent in the Fe
I data. These results can be interpreted as evidence of downflows in
the lower chromosphere. The downflow speed is estimated to be below
10 km s-1. This result demonstrates a new possibility of
studying chromospheric flows by time-distance analysis.
Title: The Magnetic Landscape of the Sun's Polar Region
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Lites, B. W.;
Matsuzaki, K.; Nagata, S.; Orozco Suárez, D.; Shimizu, T.; Shimojo,
M.; Shine, R. A.; Suematsu, Y.; Suzuki, T. K.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2008ApJ...688.1374T
Altcode: 2008arXiv0807.4631T
We present observations of the magnetic landscape of the polar region
of the Sun that are unprecedented in terms of spatial resolution,
field of view, and polarimetric precision. They were carried out with
the Solar Optical Telescope aboard Hinode. Using a Milne-Eddington
inversion, we find many vertically oriented magnetic flux tubes
with field strengths as strong as 1 kG scattered in latitude between
70° and 90°. They all have the same polarity, consistent with the
global polarity of the polar region. The field vectors are observed to
diverge from the centers of the flux elements, consistent with a view
of magnetic fields that are expanding and fanning out with height. The
polar region is also found to have ubiquitous horizontal fields. The
polar regions are the source of the fast solar wind, which is channeled
along unipolar coronal magnetic fields whose photospheric source is
evidently rooted in the strong-field, vertical patches of flux. We
conjecture that vertical flux tubes with large expansion around the
photospheric-coronal boundary serve as efficient chimneys for Alfvén
waves that accelerate the solar wind.
Title: Dynamics of the upper chromosphere
Authors: de Pontieu, B.; Carlsson, M.; McIntosh, S.; Hansteen, V.;
Tarbell, T.
Bibcode: 2008AGUFMSH51C..05D
Altcode:
In the past few years, high-resolution observations with ground-based
telescopes and the Broadband Filter Imager (BFI) and Narrowband
Filter Imager (NFI) of the Solar Optical Telescope onboard Hinode
have revolutionized our view of the dynamics and energetics of
the chromosphere. We review some of these results, including the
discovery of two different types of spicules and the finding that the
chromosphere is riddled with strong Alfvenic waves. We describe how
these observations, when combined with advanced numerical simulations,
can help address important unresolved issues regarding the connection
between the photosphere and corona, such as the role of waves and
of reconnection in driving the dynamics and energetics of the upper
chromosphere, and how chromospheric dynamics impact the transition
region and corona.
Title: Solar Surface Emerging Flux Regions: A Comparative Study of
Radiative MHD Modeling and Hinode SOT Observations
Authors: Cheung, M. C. M.; Schüssler, M.; Tarbell, T. D.; Title, A. M.
Bibcode: 2008ApJ...687.1373C
Altcode: 2008arXiv0810.5723C
We present results from numerical modeling of emerging flux regions
on the solar surface. The modeling was carried out by means of
three-dimensional (3D) radiative MHD simulations of the rise of
buoyant magnetic flux tubes through the convection zone and into the
photosphere. Due to the strong stratification of the convection zone,
the rise results in a lateral expansion of the tube into a magnetic
sheet, which acts as a reservoir for small-scale flux emergence
events at the scale of granulation. The interaction of the convective
downflows and the rising magnetic flux tube undulates it to form
serpentine field lines that emerge into the photosphere. Observational
characteristics, including the pattern of the emerging flux regions,
the cancellation of surface flux and associated high-speed downflows,
the convective collapse of photospheric flux tubes, the appearance
of anomalous darkenings, the formation of bright points, and the
possible existence of transient kilogauss horizontal fields are
discussed in the context of new observations from the Hinode Solar
Optical Telescope. Implications for the local helioseismology of
emerging flux regions are also discussed.
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.
Bibcode: 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: Magnetic Fields of the Quiet Sun: A New Quantitative
Perspective From Hinode
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..397...17L
Altcode:
This article summarizes results of studies presented in two papers
already published: Lites et al. (2007a); Lites et al. (2007b). Please
see these for further details.
Title: On-orbit Performance of the Solar Optical Telescope aboard
Hinode
Authors: Ichimoto, K.; Katsukawa, Y.; Tarbell, T.; Shine, R. A.;
Hoffmann, C.; Berger, T.; Cruz, T.; Suematsu, Y.; Tsuneta, S.; Shimizu,
T.; Lites, B. W.
Bibcode: 2008ASPC..397....5I
Altcode: 2008arXiv0804.3248I
On-orbit performance of the Solar Optical Telescope (SOT) aboard Hinode
is described with some attention to its unpredicted aspects. In general,
SOT reveals an excellent performance and has been providing outstanding
data. Some unexpected features exist, however, in behaviours of the
focus position, throughput and structural stability. Most of them are
recovered by the daily operation i.e., frequent focus adjustment,
careful heater setting and corrections in data analysis. The
tunable filter contains air bubbles which degrade the data quality
significantly. Schemes for tuning the filter without disturbing the
bubbles have been developed and tested, and some useful procedures
to obtain Dopplergrams and magnetograms are now available. October
and March, when the orbit of satellite becomes nearly perpendicular
to the direction towards the Sun, provide a favourable condition for
continuous runs of the narrow-band filter imager.
Title: High Resolution Observations of Spicules with Hinode/SOT
Authors: Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Shimizu, T.;
Okamoto, T.; Tsuneta, S.; Tarbell, T.; Shine, R. A.
Bibcode: 2008ASPC..397...27S
Altcode:
High time cadence unprecedented images at the limb with Ca II H line
filtergraph from the Solar Optical Telescope (SOT) aboard Hinode
have revealed that a spicule consists of highly dynamic multi-threads
(typically twin) as thin as a few tenths of an arcsecond, and shows
prominent lateral movement or oscillation with rotation on its axis
during its life. This multi-thread structure and lateral motion indicate
that the spicules can be driven by magnetic reconnection at unresolved
spatial scales at their footpoints.
Title: Evolution of Magnetic Fields at the Boundary of the Penumbra
Authors: Kubo, M.; Ichimoto, K.; Shimizu, T.; Lites, B. W.; Tsuneta,
S.; Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Tarbell, T.; Shine,
R. A.; Title, A. M.
Bibcode: 2008ASPC..397...79K
Altcode:
The formation of moving magnetic features (MMFs) separating from the
penumbra were successfully observed with the Solar Optical Telescope
(SOT) aboard the Hinode satellite. We find that bright features in
the outer penumbra are located at the penumbral spines, which have
magnetic fields more vertical than the surroundings, or located at the
MMFs separating from the spines. This suggests that convection in the
outer penumbra is related to the disintegration of the sunspot.
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.
Bibcode: 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: Hinode Observations of Magnetic Elements in Internetwork Areas
Authors: de Wijn, A. G.; Lites, B. W.; Berger, T. E.; Frank, Z. A.;
Tarbell, T. D.; Ishikawa, R.
Bibcode: 2008ApJ...684.1469D
Altcode: 2008arXiv0806.0345D
We use sequences of images and magnetograms from Hinode to
study magnetic elements in internetwork parts of the quiet solar
photosphere. Visual inspection shows the existence of many long-lived
(several hours) structures that interact frequently and may migrate
over distances of ~7 Mm over a period of a few hours. About a fifth
of the elements have an associated bright point in G-band or Ca
II H intensity. We apply a hysteresis-based algorithm to identify
elements. The algorithm is able to track elements for about 10 minutes
on average. Elements intermittently drop below the detection limit,
although the associated flux apparently persists and often reappears
some time later. We infer proper motions of elements from their
successive positions and find that they obey a Gaussian distribution
with an rms of 1.57 +/- 0.08 km s-1. The apparent flows
indicate a bias of about 0.2 km s-1 toward the network
boundary. Elements of negative polarity show a higher bias than elements
of positive polarity, perhaps as a result of the dominant positive
polarity of the network in the field of view or because of increased
mobility due to their smaller size. A preference for motions in X is
likely explained by higher supergranular flow in that direction. We
search for emerging bipoles by grouping elements of opposite polarity
that appear close together in space and time. We find no evidence
supporting Joy's law at arcsecond scales.
Title: What do Spicules Tell us About the Chromosphere?
Authors: de Pontieu, B.; Carlsson, M.; McIntosh, S.; Hansteen, V.;
Tarbell, T.
Bibcode: 2008ESPM...12.2.15D
Altcode:
In the past few years, high-resolution observations with ground-based
telescopes and the Broadband Filter Imager (BFI) and Narrowband
Filter Imager (NFI) of the Solar Optical Telescope onboard
Hinode have revolutionized our view of spicules and their role in
the chromosphere. We review some of these results, including the
discovery of two different types of spicules with different dynamics
and formation mechanisms, as well as the finding that the chromosphere
is riddled with strong Alfvenic waves. In an effort to determine
the formation mechanism of spicules and their impact on the outer
atmosphere, we further focus on the thermal evolution and velocities
developed by spicules. We use Dopplergrams made in the Na D 589.6 nm,
H-alpha 656.3 nm and Mg B 517.3 nm passbands, as well as filtergrams in
the Ca H 396.8 nm passband to study the spatio-temporal relationship
between the various spicular features. We compare those findings with
synthesized images based on line profiles computed from high-resolution
3D MHD numerical simulations from the University of Oslo. We also use
the Dopplergram data to investigate the velocities that develop in
the two types of spicules that were reported previously. We perform
statistical analysis of apparent velocities in the plane of the sky
and line-of-sight velocities derived from Dopplergrams to disentangle
the superposition of Alfvenic wave amplitudes and field-aligned
flows. We study these properties for a variety of magnetic field
configurations (coronal holes, quiet Sun, active region). Finally,
we focus on the formation mechanism of spicules by analyzing spicular
features in Dopplergrams on the disk that were taken simultaneously
with SP magnetograms.
Title: Erratum: The Analysis of Penumbral Fine Structure Using an
Advanced Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
Bibcode: 2008PASJ...60..933J
Altcode:
In the article [PASJ 59, S601-S606 (2007)], the word ''CSIC'' was
omitted from the affiliation of Dr. Luis Bellot Rubio. The correct
affiliation is : 2Instituto de Astrofísica de Andalucía
(CSIC), Apdo. de Correos 3004, 18080 Granada, Spain
Title: Disintegration of Magnetic Flux in Decaying Sunspots as
Observed with the Hinode SOT
Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu,
Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata,
S.; Tsuneta, S.
Bibcode: 2008ApJ...681.1677K
Altcode: 2008arXiv0806.0415K
Continuous observations of sunspot penumbrae with the Solar Optical
Telescope aboard Hinode clearly show that the outer boundary of the
penumbra fluctuates around its averaged position. The penumbral outer
boundary moves inward when granules appear in the outer penumbra. We
discover that such granules appear one after another while moving
magnetic features (MMFs) are separating from the penumbral "spines"
(penumbral features that have fields that are stronger and more vertical
than those of their surroundings). These granules that appear in the
outer penumbra often merge with bright features inside the penumbra
that move with the spines as they elongate toward the moat region. This
suggests that convective motions around the penumbral outer boundary are
related to the disintegration of magnetic flux in the sunspot. We also
find that dark penumbral filaments frequently elongate into the moat
region in the vicinity of MMFs that detach from penumbral spines. Such
elongating dark penumbral filaments correspond to nearly horizontal
fields extending from the penumbra. Pairs of MMFs with positive and
negative polarities are sometimes observed along the elongating dark
penumbral filaments. This strongly supports the notion that such
elongating dark penumbral filaments have magnetic fields with a "sea
serpent"-like structure. Evershed flows, which are associated with the
penumbral horizontal fields, may be related to the detachment of the
MMFs from the penumbral spines, as well as to the formation of the MMFs
along the dark penumbral filaments that elongate into the moat region.
Title: Polarization Calibration of the Solar Optical Telescope
onboard Hinode
Authors: Ichimoto, K.; Lites, B.; Elmore, D.; Suematsu, Y.; Tsuneta,
S.; Katsukawa, Y.; Shimizu, T.; Shine, R.; Tarbell, T.; Title, A.;
Kiyohara, J.; Shinoda, K.; Card, G.; Lecinski, A.; Streander, K.;
Nakagiri, M.; Miyashita, M.; Noguchi, M.; Hoffmann, C.; Cruz, T.
Bibcode: 2008SoPh..249..233I
Altcode: 2008SoPh..tmp...69I
The Solar Optical Telescope (SOT) onboard Hinode aims to obtain vector
magnetic fields on the Sun through precise spectropolarimetry of
solar spectral lines with a spatial resolution of 0.2 - 0.3 arcsec. A
photometric accuracy of 10−3 is achieved and, after the
polarization calibration, any artificial polarization from crosstalk
among Stokes parameters is required to be suppressed below the level
of the statistical noise over the SOT's field of view. This goal was
achieved by the highly optimized design of the SOT as a polarimeter,
extensive analyses and testing of optical elements, and an end-to-end
calibration test of the entire system. In this paper we review both
the approach adopted to realize the high-precision polarimeter of the
SOT and its final polarization characteristics.
Title: Image Stabilization System for Hinode (Solar-B) Solar Optical
Telescope
Authors: Shimizu, T.; Nagata, S.; Tsuneta, S.; Tarbell, T.; Edwards,
C.; Shine, R.; Hoffmann, C.; Thomas, E.; Sour, S.; Rehse, R.; Ito,
O.; Kashiwagi, Y.; Tabata, M.; Kodeki, K.; Nagase, M.; Matsuzaki,
K.; Kobayashi, K.; Ichimoto, K.; Suematsu, Y.
Bibcode: 2008SoPh..249..221S
Altcode:
The Hinode Solar Optical Telescope (SOT) is the first space-borne
visible-light telescope that enables us to observe magnetic-field
dynamics in the solar lower atmosphere with 0.2 - 0.3 arcsec spatial
resolution under extremely stable (seeing-free) conditions. To achieve
precise measurements of the polarization with diffraction-limited
images, stable pointing of the telescope (<0.09 arcsec, 3σ) is
required for solar images exposed on the focal plane CCD detectors. SOT
has an image stabilization system that uses image displacements
calculated from correlation tracking of solar granules to control
a piezo-driven tip-tilt mirror. The system minimizes the motions
of images for frequencies lower than 14 Hz while the satellite and
telescope structural design damps microvibration in higher frequency
ranges. It has been confirmed from the data taken on orbit that
the remaining jitter is less than 0.03 arcsec (3σ) on the Sun. This
excellent performance makes a major contribution to successful precise
polarimetric measurements with 0.2 - 0.3 arcsec resolution.
Title: The Solar Optical Telescope for the Hinode Mission: An Overview
Authors: Tsuneta, S.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Otsubo,
M.; Shimizu, T.; Suematsu, Y.; Nakagiri, M.; Noguchi, M.; Tarbell,
T.; Title, A.; Shine, R.; Rosenberg, W.; Hoffmann, C.; Jurcevich,
B.; Kushner, G.; Levay, M.; Lites, B.; Elmore, D.; Matsushita, T.;
Kawaguchi, N.; Saito, H.; Mikami, I.; Hill, L. D.; Owens, J. K.
Bibcode: 2008SoPh..249..167T
Altcode: 2008SoPh..tmp...74T; 2007arXiv0711.1715T
The Solar Optical Telescope (SOT) aboard the Hinode satellite
(formerly called Solar-B) consists of the Optical Telescope Assembly
(OTA) and the Focal Plane Package (FPP). The OTA is a 50-cm
diffraction-limited Gregorian telescope, and the FPP includes the
narrowband filtergraph (NFI) and the broadband filtergraph (BFI), plus
the Stokes Spectro-Polarimeter (SP). The SOT provides unprecedented
high-resolution photometric and vector magnetic images of the
photosphere and chromosphere with a very stable point spread function
and is equipped with an image-stabilization system with performance
better than 0.01 arcsec rms. Together with the other two instruments
on Hinode (the X-Ray Telescope (XRT) and the EUV Imaging Spectrometer
(EIS)), the SOT is poised to address many fundamental questions about
solar magnetohydrodynamics. This paper provides an overview; the
details of the instrument are presented in a series of companion papers.
Title: Frequent Occurrence of High-Speed Local Mass Downflows on
the Solar Surface
Authors: Shimizu, T.; Lites, B. W.; Katsukawa, Y.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Nagata, S.; Kubo, M.; Shine, R. A.; Tarbell,
T. D.
Bibcode: 2008ApJ...680.1467S
Altcode: 2008arXiv0804.1167S
We report on new spectropolarimetric measurements with simultaneous
filter imaging observation, revealing the frequent appearance of
polarization signals indicating high-speed, probably supersonic,
downflows that are associated with at least three different
configurations of magnetic fields in the solar photosphere. The
observations were carried out with the Solar Optical Telescope on
board the Hinode satellite. High-speed downflows are excited when a
moving magnetic feature is newly formed near the penumbral boundary of
sunspots. Also, a new type of downflows is identified at the edge of
sunspot umbra that lack accompanying penumbral structures. These may
be triggered by the interaction of magnetic fields swept by convection
with well-concentrated magnetic flux. Another class of high-speed
downflows are observed in quiet Sun and sunspot moat regions. These are
closely related to the formation of small concentrated magnetic flux
patches. High-speed downflows of all types are transient time-dependent
mass motions. These findings suggest that the excitation of supersonic
mass flows are one of the key observational features of the dynamical
evolution occurring in magnetic-field fine structures on the solar
surface.
Title: Cooperative Observation of Ellerman Bombs between the Solar
Optical Telescope aboard Hinode and Hida/Domeless Solar Telescope
Authors: Matsumoto, Takuma; Kitai, Reizaburo; Shibata, Kazunari;
Nagata, Shin'ichi; Otsuji, Kenichi; Nakamura, Tahei; Watanabe, Hiroko;
Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu,
Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Lites, Bruce W.;
Shine, Richard A.; Title, Alan M.
Bibcode: 2008PASJ...60..577M
Altcode:
High-resolution CaIIH broad-band filter images of NOAA10933 on 2007
January 5 were obtained by the Solar Optical Telescope aboard the Hinode
satellite. Many small-scale (∼1") bright points were observed outside
the sunspot and inside the emerging flux region. We identified some of
these bright points with Ellerman bombs (EBs) by using Hα images taken
by the Domeless Solar Telescope at Hida observatory. The sub-arcsec
structures of two EBs seen in CaIIH were studied in detail. Our
observation showed the following two aspects: (1) The CaIIH bright
points identified with EBs were associated with the bipolar magnetic
field structures, as reported by previous studies. (2)The structure
of the CaIIH bright points turned out to consist of the following two
parts: a central elongated bright core (0.7" × 0.5") located along
the magnetic neutral line and a diffuse halo (1.2"×1.8").
Title: Velocities and thermal evolution of chromospheric spicules
Authors: de Pontieu, B.; McIntosh, S. W.; Tarbell, T.; Carlsson,
M. P.; Hansteen, V. H.
Bibcode: 2008AGUSMSP53A..06D
Altcode:
We use the Broadband Filter Imager (BFI) and Narrowband Filter
Imager (NFI) of the Solar Optical Telescope on Hinode to study the
thermal evolution and velocities developed by chromospheric plasma in
spicules. We use Dopplergrams made in the Na D 589.6 nm, Hα 656.3 nm
and Mg B 517.3 nm passbands, as well as filtergrams in the Ca H 396.8 nm
passband to study the spatio-temporal relationship between the various
spicular features. We compare those findings with synthesized images
based on line profiles computed from high-resolution 3D MHD numerical
simulations from the University of Oslo. We also use the Dopplergram
data to investigate the velocities that develop in the two types of
spicules that were reported previously. We perform statistical analysis
of apparent velocities in the plane of the sky and line-of-sight
velocities derived from Dopplergrams to disentangle the superposition
of Alfvenic wave amplitudes and field-aligned flows. We study these
properties for a variety of magnetic field configurations (coronal
holes, quiet Sun, active region). Finally, we focus on the formation
mechanism of spicules by analyzing spicular features in Dopplergrams
on the disk that were taken simultaneously with SP magnetograms. This
work was supported by NASA contract NNM07AA01C. The Hinode mission is
operated by ISAS/JAXA, NAOJ, NASA, STFC, ESA and NSC.
Title: Emergence of a helical flux rope and prominence formation
Authors: Okamoto, T. J.; Tsuneta, S.; Lites, B. W.; Kubo, M.; Yokoyama,
T.; Berger, T. E.; Ichimoto, K.; Katsukawa, Y.; Nagata, S.; Shibata,
K.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2008AGUSMSP43B..06O
Altcode:
We report a discovery about emergence of a helical flux rope. The
episode may be related to the formation and evolution of an active
region prominence. Statistical studies by previous authors indicate that
numerous prominences have the inverse-polarity configuration suggesting
the helical magnetic configurations. There are two theoretical
models about formation of such a coronal helical magnetic field in
association with prominences: flux rope model and sheared-arcade
model. We have so far no clear observational evidence to support
either model. In order to find a clue about the formation of the
prominence, we had continuous observations of NOAA AR 10953 with the
SOT during 2007 April 28 to May 9. A prominence was located over the
polarity inversion line in the south-east of the main sunspot. These
observations provided us with a time series of vector magnetic fields
on the photosphere under the prominence. We found four new features:
(1) The abutting opposite-polarity regions on the two sides along
the polarity inversion line first grew laterally in size and then
narrowed. (2) These abutting regions contained vertically-weak,
but horizontally-strong magnetic fields. (3) The orientations of
the horizontal magnetic fields along the polarity inversion line on
the photosphere gradually changed with time from a normal- polarity
configuration to an inverse-polarity one. (4) The horizontal-magnetic
field region was blueshifted. These indicate that helical flux rope
emerges from below the photosphere into the corona along the polarity
inversion line under the prominence. We suggest that this supply of a
helical magnetic flux possibly into the corona is related to formation
and maintenance of active-region prominences.
Title: Chromospheric Flows in the Vicinity of Magnetic Features in
the Quiet Sun Observed with Hinode SOT
Authors: Tarbell, T.; de Pontieu, B.; Carlsson, M.; Hansteen, V.;
McIntosh, S.; Ichimoto, K.
Bibcode: 2008AGUSMSP41B..02T
Altcode:
The Narrowband Filter Imager of the Solar Optical Telescope on Hinode
can measure Doppler shifts and line-of- sight magnetic fields in two
lines with contributions from the low chromosphere: Na D 589.6 nm and
Mg b 517.3 nm. The SOT Spectro-Polarimeter also measures very accurate
vector magnetic fields and Doppler velocities in the photosphere. These
observations have diffraction-limited spatial resolution and superb
stability. We present examples of these measurements in quiet sun
at various disk positions. In addition to the expected granulation
and f- and p-modes, conspicuous longer-lived downflows are seen near
strong network flux elements. Transient upflows are also detected,
presumably the base of flows seen in spicules at the limb and H-alpha
mottles on the disk. Velocity features associated with emerging and
cancelling magnetic features are also described. The observations are
compared with synthesized images made from line profiles computed from
the University of Oslo 3-D MHD simulations. This work was supported by
NASA contract NNM07AA01C. The Hinode mission is operated by ISAS/JAXA,
NAOJ, NASA, STFC, ESA and NSC.
Title: Photospheric Signature of Penumbral Microjets
Authors: Katsukawa, Y.; Jurcak, J.; Ichimoto, K.; Suemtasu, Y.;
Tsuneta, S.; Shimizu, T.; Berger, T. E.; Shine, R. A.; Tarbell, T. D.;
Lites, B. W.
Bibcode: 2008AGUSMSP53A..03K
Altcode:
HINODE Solar Optical Telescope (SOT) discovered ubiquitous occurrence
of fine-scale jetlike activities in penumbral chromospheres, which
are referred to as penumbral microjets. The microjets' small width
of 400 km and short duration of less than 1 min make them difficult
to identify in existing ground-based observations. The apparent
rise velocity is faster than 50km/s and is roughly comparable to
the Alfven speed in the sunspot chromosphere. These properties of
penumbral microjets suggest that magnetic reconnection in uncombed
magnetic field configuration is the most possible cause of penumbral
microjets. In order to understand magnetic configuration associated with
penumbral microjets and prove the chromospheric magnetic reconnection
hypothesis, we investigated relationship between penumbral microjets
seen in CaIIH images and photospheric magnetic fields measured by
the HINODE spectro-polarimeter. We found the inclination angles of
penumbral microjets measured in CaII H images are roughly consistent
with inclination angles of relatively vertical magnetic field
component in uncombed magnetic field configuration. In addition,
strong and transient downflows are observed in the photosphere near
the boundary of a horizontal flux tube associated with a penumbral
microjet. The size of the downflow region is about 300km, which is
close to the width of penumbral microjets seen in CaII H images. The
downflow velocity of several km/s might be a result of an outflow of
chromospheric magnetic reconnection and suffer deceleration due to
the higher density in the photosphere.
Title: Non-Linear Force-Free Field Modeling of a Solar Active Region
Around the Time of a Major Flare and Coronal Mass Ejection
Authors: De Rosa, M. L.; Schrijver, C. J.; Metcalf, T. R.; Barnes,
G.; Lites, B.; Tarbell, T.; McTiernan, J.; Valori, G.; Wiegelmann,
T.; Wheatland, M.; Amari, T.; Aulanier, G.; Démoulin, P.; Fuhrmann,
M.; Kusano, K.; Régnier, S.; Thalmann, J.
Bibcode: 2008AGUSMSP31A..06D
Altcode:
Solar flares and coronal mass ejections are associated with rapid
changes in coronal magnetic field connectivity and are powered by
the partial dissipation of electrical currents that run through
the solar corona. A critical unanswered question is whether the
currents involved are induced by the advection along the photosphere
of pre-existing atmospheric magnetic flux, or whether these currents
are associated with newly emergent flux. We address this problem by
applying nonlinear force-free field (NLFFF) modeling to the highest
resolution and quality vector-magnetographic data observed by the
recently launched Hinode satellite on NOAA Active Region 10930 around
the time of a powerful X3.4 flare in December 2006. We compute 14
NLFFF models using 4 different codes having a variety of boundary
conditions. We find that the model fields differ markedly in geometry,
energy content, and force-freeness. We do find agreement of the best-fit
model field with the observed coronal configuration, and argue (1)
that strong electrical currents emerge together with magnetic flux
preceding the flare, (2) that these currents are carried in an ensemble
of thin strands, (3) that the global pattern of these currents and
of field lines are compatible with a large-scale twisted flux rope
topology, and (4) that the ~1032~erg change in energy associated with
the coronal electrical currents suffices to power the flare and its
associated coronal mass ejection. We discuss the relative merits of
these models in a general critique of our present abilities to model
the coronal magnetic field based on surface vector field measurements.
Title: Disintegration of Magnetic Flux in Decaying Sunspots as
Observed with the Hinode/SOT
Authors: Kubo, M.; Lites, B. W.; Ichimoto, K.; Shimizu, T.; Suematsu,
Y.; Katsukawa, Y.; Tarbell, T. D.; Shine, R. A.; Title, A. M.; Nagata,
S.; Tsuneta, S.
Bibcode: 2008AGUSMSP31B..01K
Altcode:
Continuous observations of sunspot penumbrae with the Solar Optical
Telescope aboard Hinode clearly show that the outer boundary of the
penumbra fluctuates around its averaged position. The penumbral outer
boundary moves inward when granules appear in the outer penumbra. We
discover that such granules appear one after another while moving
magnetic features (MMFs) are separating from the penumbral "spines"
(penumbral features having fields that are stronger and more vertical
than their surroundings). These granules that appear in the outer
penumbra often merge with bright features inside the penumbra that move
with spines as they elongate toward the moat region. This suggests that
convective motions around the penumbral outer boundary are related to
disintegration of magnetic flux in the sunspot. We also find that dark
penumbral filaments frequently elongate into the moat region in the
vicinity of MMFs that detach from penumbral spines. Such elongating
dark penumbral filaments correspond to nearly horizontal fields
extending from the penumbra. Pairs of MMFs with positive and negative
polarities are sometimes observed along the elongating dark penumbral
filaments. This strongly supports the notion that such elongating dark
penumbral filaments have magnetic fields with a "sea serpent"-like
structure. Evershed flows, which are associated with the penumbral
horizontal fields, may be related to detachment of the MMFs from the
penumbral spines, as well as to the formation of the MMFs along the
dark penumbral filaments that elongate into the moat region.
Title: Quiescent Prominence Structure and Dynamics: a new View From
the Hinode/SOT
Authors: Berger, T.; Okamoto, J.; Slater, G.; Magara, T.; Tarbell,
T.; Tsuneta, S.; Hurlburt, N.
Bibcode: 2008AGUSMSP53A..01B
Altcode:
To date the Hinode/Solar Optical Telescope (SOT) has produced over a
dozen sub-arcsecond, multi-hour movies of quiescent solar prominences
in both the Ca II 396.8~nm H-line and the H-alpha 656.3~nm line. These
datasets have revealed new details of the structure and dynamics of
quiescent prominences including a new form of mass transport in the
form of buoyant plume upflows from the chromosphere. We review the
SOT prominence datasets to show that quiescent prominences appear in
two major morphological categories: "vertically" and "horizontally"
structured. The vertically structured prominences all show ubiquitous
downflows in 400--700~km wide "streams" with velocities of approximately
10~km~s-1. Most of the vertically structured prominences also show
episodic upflows in the form of dark turbulent plumes with typical
velocities of 20~km~s-1. Large-scale oscillations are frequently
seen in vertical prominences with periods on the order of 10 min and
upward propagation speeds of approximately 10~km~s-1. In addition,
"bubble" events in which large voids 10--30~Mm across inflate and
then burst are seen in some of the vertical prominences. In contrast,
the horizontally structured quiescent prominences exhibit only limited
flows along the horizontal filaments. We speculate on the origin of
the distinction between the vertically and horizontally structured
prominences, taking into account viewing angle and the underlying
photospheric magnetic flux density. We also discuss the nature of the
mysterious dark plumes and bubble expansions and their implications
for prominence mass balance in light of recent models of prominence
magnetic structure that find vertical flows along some field lines.
Title: High Frequency Acoustic Waves in the Sun's Atmosphere
Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Straus, T.;
Tarbell, T. D.
Bibcode: 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: Formation of Solar Magnetic Flux Tubes with Kilogauss Field
Strength Induced by Convective Instability
Authors: Nagata, Shin'ichi; Tsuneta, Saku; Suematsu, Yoshinori;
Ichimoto, Kiyoshi; Katsukawa, Yukio; Shimizu, Toshifumi; Yokoyama,
Takaaki; Tarbell, Theodore D.; Lites, Bruce W.; Shine, Richard A.;
Berger, Thomas E.; Title, Alan M.; Bellot Rubio, Luis R.; Orozco
Suárez, David
Bibcode: 2008ApJ...677L.145N
Altcode:
Convective instability has been a mechanism used to explain
the formation of solar photospheric flux tubes with kG field
strength. However, the turbulence of the Earth's atmosphere has
prevented ground-based observers from examining the hypothesis
with precise polarimetric measurement on the subarcsecond scale
flux tubes. Here we discuss observational evidence of this scenario
based on observations with the Solar Optical Telescope (SOT) aboard
Hinode. The cooling of an equipartition field strength flux tube
precedes a transient downflow reaching 6 km s-1 and the
intensification of the field strength to 2 kG. These observations
agree very well with the theoretical predictions.
Title: Transient horizontal magnetic fields in solar plage regions
Authors: Ishikawa, R.; Tsuneta, S.; Ichimoto, K.; Isobe, H.; Katsukawa,
Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu,
Y.; Tarbell, T. D.; Title, A. M.
Bibcode: 2008A&A...481L..25I
Altcode: 2008arXiv0802.1769I
Aims:We report the discovery of isolated, small-scale emerging
magnetic fields in a plage region with the Solar Optical Telescope
aboard Hinode.
Methods: Spectro-polarimetric observations were
carried out with a cadence of 34 s for the plage region located near
disc center. The vector magnetic fields are inferred by Milne-Eddington
inversion.
Results: The observations reveal widespread occurrence
of transient, spatially isolated horizontal magnetic fields. The
lateral extent of the horizontal magnetic fields is comparable to
the size of photospheric granules. These horizontal magnetic fields
seem to be tossed about by upflows and downflows of the granular
convection. We also report an event that appears to be driven by the
magnetic buoyancy instability. We refer to buoyancy-driven emergence
as type 1 and convection-driven emergence as type 2. Although both
events have magnetic field strengths of about 600 G, the filling
factor of type 1 is a factor of two larger than that of type 2.
Conclusions: Our finding suggests that the granular convection in
the plage regions is characterized by a high rate of occurrence of
granular-sized transient horizontal fields.
Title: Net circular polarization of sunspots in high spatial
resolution
Authors: Ichimoto, K.; Tsuneta, S.; Suematsu, Y.; Katsukawa, Y.;
Shimizu, T.; Lites, B. W.; Kubo, M.; Tarbell, T. D.; Shine, R. A.;
Title, A. M.; Nagata, S.
Bibcode: 2008A&A...481L...9I
Altcode:
Context: Net circular polarization (NCP) of spectral lines in
sunspots has been most successfully explained by the presense of
discontinuities in the magnetic field inclination and flow velocity
along the line-of-sight in the geometry of the embedded flux tube model
of penumbrae (Δγ-effect).
Aims: The fine scale structure of
NCP in a sunspot is examined with special attention paid to spatial
relations of the Evershed flow to confirm the validity of the present
interpretation of the NCP of sunspots.
Methods: High resolution
spectro-polarimetric data of a positive-polarity sunspot obtained
by the Solar Optical Telescope aboard Hinode are analysed.
Results: A positive NCP is associated with the Evershed flow
channels in both limb-side and disk center-side penumbrae and with
upflows in the penumbra at disk center. The negative NCP in the disk
center-side penumbra is generated in inter-Evershed flow channels.
Conclusions: The first result is apparently inconsistent with the
current explanation of NCP with the Δγ-effect but rather suggests a
positive correlation between the magnetic field strength and the flow
velocity as the cause of the NCP. The second result serves as strong
evidence for the presence of gas flows in inter-Evershed flow channels.
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.
Bibcode: 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: Nonlinear Force-free Field Modeling of a Solar Active Region
around the Time of a Major Flare and Coronal Mass Ejection
Authors: Schrijver, C. J.; DeRosa, M. L.; Metcalf, T.; Barnes, G.;
Lites, B.; Tarbell, T.; McTiernan, J.; Valori, G.; Wiegelmann, T.;
Wheatland, M. S.; Amari, T.; Aulanier, G.; Démoulin, P.; Fuhrmann,
M.; Kusano, K.; Régnier, S.; Thalmann, J. K.
Bibcode: 2008ApJ...675.1637S
Altcode: 2007arXiv0712.0023S
Solar flares and coronal mass ejections are associated with rapid
changes in field connectivity and are powered by the partial dissipation
of electrical currents in the solar atmosphere. A critical unanswered
question is whether the currents involved are induced by the motion of
preexisting atmospheric magnetic flux subject to surface plasma flows or
whether these currents are associated with the emergence of flux from
within the solar convective zone. We address this problem by applying
state-of-the-art nonlinear force-free field (NLFFF) modeling to the
highest resolution and quality vector-magnetographic data observed
by the recently launched Hinode satellite on NOAA AR 10930 around
the time of a powerful X3.4 flare. We compute 14 NLFFF models with
four different codes and a variety of boundary conditions. We find
that the model fields differ markedly in geometry, energy content,
and force-freeness. We discuss the relative merits of these models in
a general critique of present abilities to model the coronal magnetic
field based on surface vector field measurements. For our application
in particular, we find a fair agreement of the best-fit model field
with the observed coronal configuration, and argue (1) that strong
electrical currents emerge together with magnetic flux preceding the
flare, (2) that these currents are carried in an ensemble of thin
strands, (3) that the global pattern of these currents and of field
lines are compatible with a large-scale twisted flux rope topology,
and (4) that the ~1032 erg change in energy associated with
the coronal electrical currents suffices to power the flare and its
associated coronal mass ejection.
Title: Hinode SOT Observations of Solar Quiescent Prominence Dynamics
Authors: Berger, Thomas E.; Shine, Richard A.; Slater, Gregory L.;
Tarbell, Theodore D.; Title, Alan M.; Okamoto, Takenori J.; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Suematsu, Yoshinori; Tsuneta, Saku; Lites,
Bruce W.; Shimizu, Toshifumi
Bibcode: 2008ApJ...676L..89B
Altcode:
We report findings from multihour 0.2'' resolution movies of
solar quiescent prominences (QPs) observed with the Solar Optical
Telescope (SOT) on the Hinode satellite. The observations verify
previous findings of filamentary downflows and vortices in QPs. SOT
observations also verify large-scale transverse oscillations in QPs,
with periods of 20-40 minutes and amplitudes of 2-5 Mm. The upward
propagation speed of several waves is found to be ~10 km s-1,
comparable to the sound speed of a 10,000 K plasma, implying that
the waves are magnetoacoustic in origin. Most significantly, Hinode
SOT observations reveal that dark, episodic upflows are common in
QPs. The upflows are 170-700 km in width, exhibit turbulent flow,
and rise with approximately constant speeds of ~20 km s-1
from the base of the prominence to heights of ~10-20 Mm. The upflows
are visible in both the Ca II H-line and Hα bandpasses of SOT. The new
flows are seen in about half of the QPs observed by SOT to date. The
dark upflows resemble buoyant starting plumes in both their velocity
profile and flow structure. We discuss thermal and magnetic mechanisms
as possible causes of the plumes.
Title: Reappraising Transition Region Line Widths in Light of Recent
Alfvén Wave Discoveries
Authors: McIntosh, Scott W.; De Pontieu, Bart; Tarbell, Theodore D.
Bibcode: 2008ApJ...673L.219M
Altcode: 2008arXiv0801.0671M
We provide a new interpretation of ultraviolet transition region
emission line widths observed by the SUMER instrument on the Solar
and Heliospheric Observatory (SOHO). This investigation is prompted
by observations of the chromosphere at unprecedented spatial and
temporal resolution from the Solar Optical Telescope (SOT) on Hinode
revealing that all chromospheric structures above the limb display
significant transverse (Alfvénic) perturbations. We demonstrate
that the magnitude, network sensitivity, and apparent center-to-limb
isotropy of the measured line widths (formed below 250,000 K) can be
explained by an observationally constrained forward model in which the
line width is caused by the line-of-sight superposition of longitudinal
and Alfvénic motions on the small-scale (spicular) structures that
dominate the chromosphere and low transition region.
Title: Emergence of a Helical Flux Rope under an Active Region
Prominence
Authors: Okamoto, Takenori J.; Tsuneta, Saku; Lites, Bruce W.; Kubo,
Masahito; Yokoyama, Takaaki; Berger, Thomas E.; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shibata, Kazunari; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2008ApJ...673L.215O
Altcode: 2008arXiv0801.1956O
Continuous observations were obtained of NOAA AR 10953 with the Solar
Optical Telescope (SOT) on board the Hinode satellite from 2007 April
28 to May 9. A prominence was located over the polarity inversion
line (PIL) to the southeast of the main sunspot. These observations
provided us with a time series of vector magnetic fields on the
photosphere under the prominence. We found four features: (1) The
abutting opposite-polarity regions on the two sides along the PIL first
grew laterally in size and then narrowed. (2) These abutting regions
contained vertically weak but horizontally strong magnetic fields. (3)
The orientations of the horizontal magnetic fields along the PIL on
the photosphere gradually changed with time from a normal-polarity
configuration to an inverse-polarity one. (4) The horizontal magnetic
field region was blueshifted. These indicate that helical flux rope
was emerging from below the photosphere into the corona along the PIL
under the preexisting prominence. We suggest that this supply of a
helical magnetic flux to the corona is associated with evolution and
maintenance of active region prominences.
Title: The Horizontal Magnetic Flux of the Quiet-Sun Internetwork
as Observed with the Hinode Spectro-Polarimeter
Authors: Lites, B. W.; Kubo, M.; Socas-Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa, Y.;
Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ApJ...672.1237L
Altcode:
Observations of very quiet Sun using the Solar Optical
Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft
reveal that the quiet internetwork regions are pervaded by horizontal
magnetic flux. The spatial average horizontal apparent flux density
derived from wavelength-integrated measures of Zeeman-induced linear
polarization is BTapp = 55 Mx cm -2, as
compared to the corresponding average vertical apparent flux density of
| BLapp| = 11 Mx cm -2. Distributions
of apparent flux density are presented. Magnetic fields are organized on
mesogranular scales, with both horizontal and vertical fields showing
"voids" of reduced flux density of a few granules spatial extent. The
vertical fields are concentrated in the intergranular lanes, whereas the
stronger horizontal fields are somewhat separated spatially from the
vertical fields and occur most commonly at the edges of the bright
granules. High-S/N observations from disk center to the limb help
to constrain possible causes of the apparent imbalance between |
BLapp| and BTapp, with
unresolved structures of linear dimension on the surface smaller by at
least a factor of 2 relative to the SOT/SP angular resolution being one
likely cause of this discrepancy. Other scenarios for explaining this
imbalance are discussed. The horizontal fields are likely the source of
the "seething" fields of the quiet Sun discovered by Harvey et al. The
horizontal fields may also contribute to the "hidden" turbulent flux
suggested by studies involving Hanle effect depolarization of scattered
radiation.
Title: Hinode Observations of Flux Emergence in Quiet and Active
Regions
Authors: Lites, B. W.; Centeno, R.; Kubo, M.; Socas-Navarro, H. Berger,
T.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.;
Katsukawa, Y.; Tsuneta, S.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2008ASPC..383...71L
Altcode:
We review briefly the observational understanding of emergence of
flux in both the quiet Sun and active regions in the light of first
results from the joint Japan/US/UK Hinode mission. That spacecraft
is now providing us with our first continuous, high resolution
measurements of the photospheric vector magnetic field, along with
high resolution observations of the thermal and dynamic properties
of the chromosphere and corona. This review is intended to present a
few very early results and to highlight the potential for discovery
offered by this extraordinary new mission. The discovery of ubiquitous
horizontal magnetic flux in the quiet internetwork regions is presented.
Title: Mangetic field properties at the footpoints of solar
microflares (active-region transient brightenings)
Authors: Shimizu, T.; Kano, R.; Katsukawa, Y.; Kubo, M.; Deluca, E.;
Ichimoto, K.; Lites, B.; Nagata, S.; Sakao, T.; Shine, R.; Suematsu,
Y.; Tarbell, T.; Title, A.; Tsuneta, S.
Bibcode: 2007AGUFMSH52C..06S
Altcode:
Solar active regions produce numerous numbers of small-scale explosive
energy releases, i.e., microflares, which are captured by imaging
observations in soft X-rays as transient brightenings of small-scale
coronal loops. Thanks to advanced performance of X-Ray Telescope (XRT)
onboard the Hinode satellite, we can investigate finer structure
of the brightening X-ray sources in more details than we did with
Yohkoh data. One of important questions on microflares is what causes
microflares. The simultaneous visible-light observations by the Solar
Optical Telescope (SOT) allow us to explore magnetic activities
and magnetic field configuration at the photospheric footpoints
of brightening loops, giving key observations to investigate the
question. For our investigations of corona-photosphere magnetic
coupling, we have established co-alignment between SOT and XRT
with accuracy better than 1 arcsec (Shimizu et al. 2007, PASJ in
press). It turns out that Ca II H observations are very useful
to identify the exact positions of footpoints of X-ray transient
brightening loops. Small "Kernels" are sometimes observed in Ca II H
and they may be signature of highly accelerated non-thermal particles
impinging on chromosphere. As already shown in Shimizu et al.(2002),
frequent transient brightenings are observed at the locations where
emerging activities are on going. However, another type of brightening
triggering mechanism should exist to explain some observed multiple-loop
brightenings. In the multiple-loop brightenings, multiple loops are
magnetically in parallel with each other and no apparent magnetic
activities, such as emerging and canceling, are observed at and near
the footpoints. This paper will present SOT observations of some
microflares observed with XRT.
Title: Small-Scale Jetlike Features in Penumbral Chromospheres
Authors: Katsukawa, Y.; Berger, T. E.; Ichimoto, K.; Lites, B. W.;
Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.;
Title, A. M.; Tsuneta, S.
Bibcode: 2007Sci...318.1594K
Altcode:
We observed fine-scale jetlike features, referred to as penumbral
microjets, in chromospheres of sunspot penumbrae. The microjets
were identified in image sequences of a sunspot taken through a Ca II
H-line filter on the Solar Optical Telescope on board the Japanese solar
physics satellite Hinode. The microjets’ small width of 400 kilometers
and short duration of less than 1 minute make them difficult to identify
in existing observations. The microjets are possibly caused by magnetic
reconnection in the complex magnetic configuration in penumbrae and
have the potential to heat the corona above a sunspot.
Title: Chromospheric Alfvénic Waves Strong Enough to Power the
Solar Wind
Authors: De Pontieu, B.; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Tarbell, T. D.; Schrijver, C. J.; Title, A. M.; Shine, R. A.;
Tsuneta, S.; Katsukawa, Y.; Ichimoto, K.; Suematsu, Y.; Shimizu, T.;
Nagata, S.
Bibcode: 2007Sci...318.1574D
Altcode:
Alfvén waves have been invoked as a possible mechanism for the heating
of the Sun's outer atmosphere, or corona, to millions of degrees and
for the acceleration of the solar wind to hundreds of kilometers per
second. However, Alfvén waves of sufficient strength have not been
unambiguously observed in the solar atmosphere. We used images of
high temporal and spatial resolution obtained with the Solar Optical
Telescope onboard the Japanese Hinode satellite to reveal that the
chromosphere, the region sandwiched between the solar surface and
the corona, is permeated by Alfvén waves with strong amplitudes on
the order of 10 to 25 kilometers per second and periods of 100 to
500 seconds. Estimates of the energy flux carried by these waves and
comparisons with advanced radiative magnetohydrodynamic simulations
indicate that such Alfvén waves are energetic enough to accelerate
the solar wind and possibly to heat the quiet corona.
Title: Magnetic and Doppler Observations of the Photosphere and Low
Chromosphere with the Solar Optical Telescope on Hinode
Authors: Tarbell, T. D.; Lites, B. W.; Shine, R. A.; Ichimoto, K.
Bibcode: 2007AGUFMSH53A1064T
Altcode:
We present magnetic field and Doppler shift measurements in the Mg
I b line at 517.3 nm obtained with the Solar Optical Telescope's
Narrowband Filter Imager on Hinode. The line core forms in the low
chromosphere, and the wings where the measurements are made probably
form around the temperature minimum. Stokes IQUV images in the red and
blue wings are combined to make movies of longitudinal magnetograms
and Dopplergrams. The direction of the transverse field component is
also measurable in strong field concentrations. These are compared
with very accurate photospheric magnetic measurements in Fe I 630.2 nm
from the Spectro-Polarimeter. This comparison calibrates the filter
longitudinal magnetograms in flux density and shows changes in field
geometry with height. The Doppler measurements are calibrated using
wavelength scans through the Mg line profile. A number of emerging and
canceling magnetic features were observed in AR 10961 during its disk
passage in late June and early July. Since these were made during the
Hinode eclipse season, the observations have somewhat lower spatial
resolution than usual (0.32 arcsecond pixels), but the uniformity
and sensitivity are excellent. Intermittent upflows seen between
canceling magnetic features are interpreted in terms of reconnection
outflows. Strong, persistent downflows are seen adjacent to but not
on flux concentrations outside of sunspots and pores. In the sunspot,
running penumbral waves are clearly visible, and steady downflows are
observed over the light bridges. Hinode is a Japanese mission developed
and launched by ISAS/ JAXA, with NAOJ as domestic partner and NASA and
STFC (UK) as international partners. It is operated by these agencies
in cooperation with ESA and NSC (Norway).
Title: Chromospheric Anemone Jets as Evidence of Ubiquitous
Reconnection
Authors: Shibata, Kazunari; Nakamura, Tahei; Matsumoto, Takuma; Otsuji,
Kenichi; Okamoto, Takenori J.; Nishizuka, Naoto; Kawate, Tomoko;
Watanabe, Hiroko; Nagata, Shin'ichi; UeNo, Satoru; Kitai, Reizaburo;
Nozawa, Satoshi; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi;
Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.; Berger,
Thomas E.; Lites, Bruce W.; Shine, Richard A.; Title, Alan M.
Bibcode: 2007Sci...318.1591S
Altcode: 2008arXiv0810.3974S
The heating of the solar chromosphere and corona is a long-standing
puzzle in solar physics. Hinode observations show the ubiquitous
presence of chromospheric anemone jets outside sunspots in active
regions. They are typically 3 to 7 arc seconds = 2000 to 5000 kilometers
long and 0.2 to 0.4 arc second = 150 to 300 kilometers wide, and their
velocity is 10 to 20 kilometers per second. These small jets have an
inverted Y-shape, similar to the shape of x-ray anemone jets in the
corona. These features imply that magnetic reconnection similar to that
in the corona is occurring at a much smaller spatial scale throughout
the chromosphere and suggest that the heating of the solar chromosphere
and corona may be related to small-scale ubiquitous reconnection.
Title: Twisting Motions of Sunspot Penumbral Filaments
Authors: Ichimoto, K.; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.;
Shimizu, T.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Lites, B. W.;
Kubo, M.; Nagata, S.
Bibcode: 2007Sci...318.1597I
Altcode:
The penumbra of a sunspot is composed of numerous thin, radially
extended, bright and dark filaments carrying outward gas flows
(the Evershed flow). Using high-resolution images obtained by the
Solar Optical Telescope aboard the solar physics satellite Hinode, we
discovered a number of penumbral bright filaments revealing twisting
motions about their axes. These twisting motions are observed only
in penumbrae located in the direction perpendicular to the symmetry
line connecting the sunspot center and the solar disk center, and
the direction of the twist (that is, lateral motions of intensity
fluctuation across filaments) is always from limb side to disk-center
side. Thus, the twisting feature is not an actual twist or turn of
filaments but a manifestation of dynamics of penumbral filaments with
three-dimensional radiative transfer effects.
Title: Hinode SOT observations of plume upflows and cascading
downflows in quiescent solar prominences
Authors: Berger, T.; Shine, R.; Slater, G.; Tarbell, T.; Title, A.;
Lites, B.; Tsuneta, S.; Okamoto, T. J.; Ichimoto, K.; Katsukawa, Y.;
Sekii, T.; Suematsu, Y.; Shimizu, T.
Bibcode: 2007AGUFMSH53A1065B
Altcode:
We present several Hinode SOT filtergram movies of quiescent solar
prominences that show newly discovered "plume-like" upflows and
cascading "waterfall-like" downflows that persist for the entire
multi-hour duration of the observations. The flow speeds are on the
order of 10 km/sec with typical widths of 400-700 km. Preliminary
calculations show that if the upflows are buoyancy driven, the
associated thermal perturbation is on the order of 10,000 K, sufficient
to explain the dark appearance of the upflows in the interference
filter passbands. In addition we observe rotational vortices and
body oscillations within the prominences. These new observations
challenge current magnetostatic models of solar prominences by showing
that prominence plasmas are in constant motion, often in directions
perpendicular to the magnetic field lines proposed by the models. TRACE,
Hinode/EIS, and Hinode/XRT observations are used to investigate the
differential topology of the flows across temperature regimes.
Title: On the Chromospheric Micro-jets Associated with the Penumbral
Filaments
Authors: Ryutova, M.; Berger, T.; Tarbell, T.; Frank, Z.; Title, A.
Bibcode: 2007AGUFMSH22A0843R
Altcode:
We present observations of sunspot penumbrae obtained during the disk
passage of AR 10923 (November 10--20, 2006) with the Solar Optical
Telescope (SOT) on the Hinode satellite. Co-aligned multi-hour movies
taken simultaneously in several wavelengths show fine-scale dynamics
at the sub-arcsecond level. The dynamics include helical flows along
penumbral filaments, branching of filaments, and penumbral "micro-jets"
recently described by Katsukawa et al. (AAS 210, 94.13). We present
quantitative analyzes of the penumbral jets and interpret them relative
to our recent model of penumbral filaments (Ryutova, Berger and Title,
2007, in "Collective phenomena in macroscopic systems", Ed. G. Bertin,
et al., World Scientific) to show that the jets are the result of
magnetic reconnection of the helical field lines in neighboring
non-collinear filaments.
Title: Coronal Transverse Magnetohydrodynamic Waves in a Solar
Prominence
Authors: Okamoto, T. J.; Tsuneta, S.; Berger, T. E.; Ichimoto, K.;
Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shibata, K.; Shimizu, T.;
Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.
Bibcode: 2007Sci...318.1577O
Altcode: 2008arXiv0801.1958O
Solar prominences are cool 104 kelvin plasma clouds
supported in the surrounding 106 kelvin coronal plasma by
as-yet-undetermined mechanisms. Observations from Hinode show fine-scale
threadlike structures oscillating in the plane of the sky with periods
of several minutes. We suggest that these represent Alfvén waves
propagating on coronal magnetic field lines and that these may play
a role in heating the corona.
Title: Photospheric Magnetic Flux Emergence: A comparative study
between Hinode/SOT Observations and MHD simulations
Authors: Cheung, M. C.; Schüssler, M.; Moreno-Insertis, F.; Tarbell,
T. D.
Bibcode: 2007AGUFMSH53A1073C
Altcode:
With high angular resolution, high temporal cadence and a stable
point spread function, the Solar Optical Telescope (SOT) onboard the
Hinode satellite is the ideal instrument for the study of magnetic
flux emergence and its manifestations on the solar surface. In this
presentation, we focus on the development of ephemeral regions and
small active regions. In many instances, SOT has been able to capture
the entire emergence process from beginning to end: i.e. from the
initial stages of flux appearance in granule interiors, through the
intermediate stages of G-band bright point formation, and finally
to the coalescence of small vertical flux elements to form pores. To
investigate the physics of the flux emergence process, we performed
3D numerical MHD simulations with the MURaM code. The models are able
to reproduce, and help us explain, various observational signatures
of magnetic flux emergence.
Title: Quiet-Sun Internetwork Magnetic Fields from the Inversion of
Hinode Measurements
Authors: Orozco Suárez, D.; Bellot Rubio, L. R.; del Toro Iniesta,
J. C.; Tsuneta, S.; Lites, B. W.; Ichimoto, K.; Katsukawa, Y.; Nagata,
S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title,
A. M.
Bibcode: 2007ApJ...670L..61O
Altcode: 2007arXiv0710.1405O
We analyze Fe I 630 nm observations of the quiet Sun at disk center
taken with the spectropolarimeter of the Solar Optical Telescope aboard
the Hinode satellite. A significant fraction of the scanned area,
including granules, turns out to be covered by magnetic fields. We
derive field strength and inclination probability density functions from
a Milne-Eddington inversion of the observed Stokes profiles. They show
that the internetwork consists of very inclined, hG fields. As expected,
network areas exhibit a predominance of kG field concentrations. The
high spatial resolution of Hinode's spectropolarimetric measurements
brings to an agreement the results obtained from the analysis of
visible and near-infrared lines.
Title: Center-to-Limb Variation of Stokes V Asymmetries in Solar
Pores Observed with the Hinode Spectro-Polarimeter
Authors: Morinaga, Shuji; Nagata, Shin'ichi; Ichimoto, Kiyoshi;
Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu,
Toshifumi; Shine, Richard A.; Tarbell, Theodore D.; Title, Alan M.;
Lites, Bruce; Kubo, Masahito; Sakurai, Takashi
Bibcode: 2007PASJ...59S.613M
Altcode:
Here we present spectro-polarimetric measurements of several pores
and the surrounding regions taken with the Solar Optical Telescope
aboard Hinode at various viewing angles. We analyzed the Stokes V
area asymmetry, and confirmed that it is depressed at the center of
the pores, while it shows large positive values (a blue lobe larger
than a red lobe) in the surrounding area; this is consistent with a
previous report. In addition to this ring of positive asymmetry, we
found regions of alternating positive and negative area asymmetries
when weak V regions were observed near the solar limb. The positive
asymmetry occurs on the disk-center side and the negative asymmetry
on the limb side of the magnetic concentrations. These center-to-limb
variations of the Stokes V area asymmetry can be interpreted as being
a systematic inflow of plasma into the magnetic concentrations from
their surroundings.
Title: Initial Results on Line-of-Sight Field Calibrations of SP/NFI
Data Taken by SOT/Hinode
Authors: Chae, Jongchul; Moon, Yong-Jae; Park, Young-Deuk; Ichimoto,
Kiyoshi; Sakurai, Takashi; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Shimizu, Toshifumi; Shine, Richard A.; Tarbell,
Theodore D.; Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata,
Shin'ichi; Yokoyama, Takaaki
Bibcode: 2007PASJ...59S.619C
Altcode:
We present initial results on the line-of-sight field calibration
of the two kinds of Stokes I and V data taken by the Solar Optical
Telescope on the satellite Hinode: spectral profiles of Stokes I and V
parameters recorded on the Spectro-polarimeter (SP), and monochromatic
images of the same parameters recorded on the Narrow-band Filter Imager
(NFI). By applying the center-of-gravity method to the SP data of
AR10930 taken on 2006 December 11, we determined the line-of-sight field
at every location in the active region. As a result, we found that the
line-of-sight field strength ranges up to 2kG in plages, even without
taking into account the filling factor, and up to 3.5kG or higher values
inside the umbra of the major sunspot. We calibrated the NFI data in
reference to the field determined from the SP data. In regions outside
the sunspots and the penumbral regions, we adopted a linear relation,
B|| = βV / I, between the circular polarization, V / I,
and the line-of-sight field strength, B||, and obtained β =
23.5kG in regions outside the sunspots, and β = 12.0kG in penumbral
regions. In umbral regions of sunspots, a first-order polynomial was
adopted to model the reversal of the polarization signal over the
field strength.
Title: Response of the Solar Atmosphere to Magnetic Flux Emergence
from Hinode Observations
Authors: Li, Hui; Sakurai, Takashi; Ichimito, Kiyoshi; Suematsu,
Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimizu, Toshifumi; Shine,
Richard A.; Tarbell, Theodore D.; Title, Alan M.; Lites, Bruce; Kubo,
Masahito; Nagata, Shin'ichi; Kotoku, Jun; Shibasaki, Kiyoto; Saar,
Steven H.; Bobra, Monica
Bibcode: 2007PASJ...59S.643L
Altcode:
No abstract at ADS
Title: Initial Helioseismic Observations by Hinode/SOT
Authors: Sekii, Takashi; Kosovichev, Alexander G.; Zhao, Junwei;
Tsuneta, Saku; Shibahashi, Hiromoto; Berger, Thomas E.; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu,
Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell, Theodore
D.; Title, Alan M.
Bibcode: 2007PASJ...59S.637S
Altcode: 2007arXiv0709.1806S
Results from initial helioseismic observations by the Solar Optical
Telescope on-board Hinode are reported. It has been demonstrated
that intensity oscillation data from the Broadband Filter Imager
can be used for various helioseismic analyses. The k - ω power
spectra, as well as the corresponding time-distance cross-correlation
function, which promise high-resolution time-distance analysis below
the 6-Mm travelling distance, were obtained for G-band and CaII-H
data. Subsurface supergranular patterns were observed from our first
time-distance analysis. The results show that the solar oscillation
spectrum is extended to much higher frequencies and wavenumbers, and
the time-distance diagram is extended to much shorter travel distances
and times than were observed before, thus revealing great potential
for high-resolution helioseismic observations from Hinode.
Title: Hinode Observations of Horizontal Quiet Sun Magnetic Flux
and the ``Hidden Turbulent Magnetic Flux''
Authors: Lites, Bruce; Socas-Navarro, Hector; Kubo, Masahito; Berger,
Thomas; Frank, Zoe; Shine, Richard A.; Tarbell, Theodore D.; Title,
Alan M.; Ichimoto, Kiyoshi; Katsukawa, Yukio; Tsuneta, Saku; Suematsu,
Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.571L
Altcode:
We present observations of magnetic fields of the very quiet Sun
near disk center using the Spectro-Polarimeter of the Solar Optical
Telescope aboard the Hinode satellite. These observations reveal for
the first time the ubiquitous presence of horizontal magnetic fields in
the internetwork regions. The horizontal fields are spatially distinct
from the vertical fields, demonstrating that they are not arising mainly
from buffeting of vertical flux tubes by the granular convection. The
horizontal component has an average ``apparent flux density'' of
55Mxcm-2 (assuming the horizontal field structures are
spatially resolved), in contrast to the average apparent vertical flux
density of 11Mxcm-2. The vertical fields reside mainly in
the intergranular lanes, whereas the horizontal fields occur mainly
over the bright granules, with a preference to be near the outside
edge of the bright granules. The large apparent imbalance of vertical
and horizontal flux densities is discussed, and several scenarios are
presented to explain this imbalance.
Title: Strategy for the Inversion of Hinode Spectropolarimetric
Measurements in the Quiet Sun
Authors: Orozco Suárez, David; Bellot Rubio, Luis R.; Del Toro
Iniesta, Jose Carlos; Tsuneta, Saku; Lites, Bruce; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.837O
Altcode: 2007arXiv0709.2033O
In this paper we propose an inversion strategy for the analysis of
spectropolarimetric measurements taken by Hinode in the quiet Sun. The
Spectro-Polarimeter of the Solar Optical Telescope aboard Hinode records
the Stokes spectra of the FeI line pair at 630.2nm with unprecendented
angular resolution, high spectral resolution, and high sensitivity. We
discuss the need to consider a local stray-light contamination to
account for the effects of telescope diffraction. The strategy is
applied to observations of a wide quiet Sun area at disk center. Using
these data we examine the influence of noise and initial guess models
in the inversion results. Our analysis yields the distributions of
magnetic field strengths and stray-light factors. They show that quiet
Sun internetwork regions consist mainly of hG fields with stray-light
contamination of about 0.8.
Title: Hinode Calibration for Precise Image Co-Alignment between
SOT and XRT (2006 November-2007 April)
Authors: Shimizu, Toshifumi; Katsukawa, Yukio; Matsuzaki, Keiichi;
Ichimoto, Kiyoshi; Kano, Ryohei; Deluca, Edward E.; Lundquist,
Loraine L.; Weber, Mark; Tarbell, Theodore D.; Shine, Richard A.;
Sôma, Mitsuru; Tsuneta, Saku; Sakao, Taro; Minesugi, Kenji
Bibcode: 2007PASJ...59S.845S
Altcode: 2007arXiv0709.4098S
To understand the physical mechanisms for activity and heating in
the solar atmosphere, the magnetic coupling from the photosphere
to the corona is an important piece of information from the Hinode
observations, and therefore precise positional alignment is required
among the data acquired by different telescopes. The Hinode spacecraft
and its onboard telescopes were developed to allow us to investigate
magnetic coupling with co-alignment accuracy better than 1". Using
the Mercury transit observed on 2006 November 8 and co-alignment
measurements regularly performed on a weekly basis, we have determined
the information necessary for precise image co-alignment, and have
confirmed that co-alignment better than 1" can be realized between
Solar Optical Telescope (SOT) and X-Ray Telescope (XRT) with our
baseline co-alignment method. This paper presents results from the
calibration for precise co-alignment of CCD images from SOT and XRT.
Title: Penumbral Dynamics and its Manifestation in the Overlying
Chromosphere
Authors: Ryutova, Margarita; Berger, Thomas; Tarbell, Theodor; Frank,
Zoe; Title, Alan
Bibcode: 2007APS..DPPYP8056R
Altcode:
Mature sunspots are usually surrounded by penumbra - a dense
conglomerate of a random interlaced flux tubes with varying
inclinations. High resolution observations show a fine sub-structure
of penumbral filaments and new regularities in their dynamics. These
regularities fit well our recent model of penumbra based on cascading
reconnection events occurring in the system of non-collinear flux
tubes. Each act of reconnection generates twist in the reconnected
filaments and facilitates the onset of a screw pinch instability,
consistent with the observations showing that individual filaments
are cylindrical helices with a pitch/radius ratio providing their
stability. In addition, the post-reconnection products produce a
sling-shot effect that generates oblique shocks and leads to appearence
of a lateral jets. Here we report high resolution (120-180 km) high
cadence (15-30 sec) observations taken with the Solar Optical Telescope
(SOT) on the Hinode satellite. Co-aligned multi-hour movies taken
simultaneously in several wavelengths show detailed behavior of penumbra
filaments and their effect on the overlying chromosphere. We confirm
the ubiquitous nature of penumbral micro-jets recently discovered by
SOT instrument (Katsukawa et al. 2007, AAS 210, 94.13), and present
quantitative analysis of chromospheric jets based on our recent model
of penumbra.
Title: Hinode Observations of a Vector Magnetic Field Change
Associated with a Flare on 2006 December 13
Authors: Kubo, Masahito; Yokoyama, Takaaki; Katsukawa, Yukio; Lites,
Bruce; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto, Kiyoshi; Shimizu,
Toshifumi; Nagata, Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.;
Title, Alan M.; Elmore David
Bibcode: 2007PASJ...59S.779K
Altcode: 2007arXiv0709.2397K
Continuous observations of the flare productive active region 10930
were successfully carried out with the Solar Optical Telescope aboard
the Hinode spacecraft during 2006 December 6 to 19. We focused on the
evolution of photospheric magnetic fields in this active region, and the
magnetic field properties at the site of the X3.4 class flare, using
a time series of vector field maps with high spatial resolution. The
X3.4 class flare occurred on 2006 December 13 at the apparent
collision site between the large, opposite polarity umbrae. Elongated
magnetic structures with alternatingly positive and negative polarities
resulting from flux emergence appeared one day before the flare in the
collision site penumbra. Subsequently, the polarity inversion line
at the collision site became very complicated. The number of bright
loops in CaII H increased during the formation of these elongated
magnetic structures. Flare ribbons and bright loops evolved along
the polarity inversion line and one footpoint of the bright loop was
located in a region having a large departure of the field azimuth angle
with respect to its surroundings. SOT observations with high spatial
resolution and high polarization precision revealed temporal change in
the fine structure of magnetic fields at the flare site: some parts of
the complicated polarity inversion line then disappeared, and in those
regions the azimuth angle of the photospheric magnetic field changed by
about 90°, becoming more spatially uniform within the collision site.
Title: The Analysis of Penumbral Fine Structure Using an Advanced
Inversion Technique
Authors: Jurcák, Jan; Bellot Rubio, Luis; Ichimoto, Kiyoshi;
Katsukawa, Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi;
Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.; Tsuneta,
Saku
Bibcode: 2007PASJ...59S.601J
Altcode: 2007arXiv0707.1560J
We present a method to study the penumbral fine structure using data
obtained by the spectropolarimeter on board Hinode. For the first
time, the penumbral filaments can be considered as being resolved in
spectropolarimetric measurements. This enables us to use inversion
codes with only one-component model atmospheres, and thus to assign
the obtained stratifications of the plasma parameters directly to the
penumbral fine structure. This approach was applied to the limb-side
part of the penumbra in the active region NOAA10923. Preliminary results
show a clear dependence of the plasma parameters on the continuum
intensity in the inner penumbra, i.e., a weaker and horizontal magnetic
field along with an increased line-of-sight velocity are found in the
low layers of the bright filaments. The results in the mid penumbra
are ambiguous, and future analyses are necessary to unveil the magnetic
field structure and other plasma parameters there.
Title: Fine-Scale Structures of the Evershed Effect Observed by the
Solar Optical Telescope aboard Hinode
Authors: Ichimoto, Kiyoshi; Shine, Richard A.; Lites, Bruce; Kubo,
Masahito; Shimizu, Toshifumi; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Tarbell, Theodore D.; Title, Alan M.; Nagata,
Shin'ichi; Yokoyama, Takaaki; Shimojo, Masumi
Bibcode: 2007PASJ...59S.593I
Altcode:
The small-scale structure of the Evershed effect is being studied
using data obtained by the Spectropolarimeter and the Broadband Filter
Imager of the Solar Optical Telescope aboard Hinode. We find that the
Evershed flow starts at the leading edge of inwardly migrating bright
penumbral grains, and turns to nearly a horizontal flow preferentially
in the dark lanes of the penumbra. A number of small elongated regions
that have an upward motion of ∼ 1kms-1 are found in the
deep photosphere distributed over the penumbra. They are cospatial
with bright grains and have relatively horizontal magnetic fields. A
number of patches having a strong downward motion associated with the
opposite magnetic polarity from the sunspot are also found in the mid
and outer penumbra. They could be identified as foot points of the
Evershed flow channels, though the identification of individual pairs
is not straightforward. Our results provide strong support for some
recent findings from ground-based high-resolution observations, and
are in general agreement with the well-known picture of the uncombed
structure of the penumbra, in which the penumbrae consist of rising
flux tubes carrying nearly horizontal Evershed flows embedded in more
vertical background magnetic fields.
Title: Flare Ribbons Observed with G-band and FeI 6302Å, Filters
of the Solar Optical Telescope on Board Hinode
Authors: Isobe, Hiroaki; Kubo, Masahito; Minoshima, Takashi; Ichimoto,
Kiyoshi; Katsukawa, Yukio; Tarbell, Theodore D.; Tsuneta, Saku; Berger,
Thomas E.; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Title, Alan M.
Bibcode: 2007PASJ...59S.807I
Altcode: 2007arXiv0711.3946I
The Solar Optical Telescope (SOT) on board the Hinode satellite observed
an X3.4 class flare on 2006 December 13. A typical two-ribbon structure
was observed, not only in the chromospheric CaII H line, but also in
the G-band and FeI 6302Å line. The high-resolution, seeing-free images
achieved by SOT revealed, for the first time, sub-arcsec fine structures
of the ``white light'' flare. The G-band flare ribbons on sunspot
umbrae showed a sharp leading edge, followed by a diffuse inside,
as well as a previously known core-halo structure. The underlying
structures, such as umbral dots, penumbral filaments, and granules,
were visible in the flare ribbons. Assuming that the sharp leading
edge was directly heated by a particle beam and the diffuse parts were
heated by radiative back-warming, we estimated the depth of the diffuse
flare emission using an intensity profile of the flare ribbon. We found
that the depth of the diffuse emission was about 100km or less from
the height of the source of radiative back-warming. The flare ribbons
were also visible in the Stokes-V images of FeI 6302Å, as a transient
polarity reversal. This is probably related to a ``magnetic transient''
reported in the literature. The intensity increase in Stokes-I images
indicates that the FeI 6302Å line was significantly deformed by the
flare, which may cause such a magnetic transient.
Title: Small-Scale Magnetic-Flux Emergence Observed with Hinode
Solar Optical Telescope
Authors: Otsuji, Kenichi; Shibata, Kazunari; Kitai, Reizaburo; Ueno,
Satoru; Nagata, Shin'ichi; Matsumoto, Takuma; Nakamura, Tahei;
Watanabe, Hiroko; Tsuneta, Saku; Suematsu, Yoshinori; Ichimoto,
Kiyoshi; Shimizu, Toshifumi; Katsukawa, Yukio; Tarbell, Theodore D.;
Lites, Bruce; Shine, Richard A.; Title Alan M.
Bibcode: 2007PASJ...59S.649O
Altcode: 2007arXiv0709.3207O
We observed small-scale magnetic-flux emergence in a sunspot moat region
by the Solar Optical Telescope (SOT) aboard the Hinode satellite. We
analyzed filtergram images observed at wavelengths of Fe 6302Å, G band,
and CaII H. In Stokes I images of Fe 6302Å, emerging magnetic flux was
recognized as dark lanes. In the G band, they showed to be their shapes
almost the same as in Stokes I images. These magnetic fluxes appeared
as dark filaments in CaII H images. Stokes V images of Fe 6302Å showed
pairs of opposite polarities at footpoints of each filament. These
magnetic concentrations were identified to correspond to bright points
in G band/CaII H images. From an analysis of time-sliced diagrams, we
derived the following properties of emerging flux, which are consistent
with those of previous studies: (1) Two footpoints separate each other
at a speed of 4.2kms-1 during the initial phase of evolution,
and decrease to about 1kms-1 10minutes later. (2) CaII H
filaments appear almost simultaneously with the formation of dark lanes
in Stokes I in an observational cadence of 2minutes. (3) The lifetime
of the dark lanes in the Stokes I and G band is 8minutes, while that
of Ca filament is 12minutes. An interesting phenomena was observed,
that an emerging flux tube expanded laterally in the photosphere with a
speed of 3.8kms-1. A discussion on the horizontal expansion
of the flux tube is given with refernce to previous simulation studies.
Title: Observations of Sunspot Oscillations in G Band and CaII H
Line with Solar Optical Telescope on Hinode
Authors: Nagashima, Kaori; Sekii, Takashi; Kosovichev, Alexander G.;
Shibahashi, Hiromoto; Tsuneta, Saku; Ichimoto, Kiyoshi; Katsukawa,
Yukio; Lites, Bruce; Nagata, Shin'ichi; Shimizu, Toshifumi; Shine,
Richard A.; Suematsu, Yoshinori; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 2007PASJ...59S.631N
Altcode: 2007arXiv0709.0569N
Exploiting high-resolution observations made by the Solar Optical
Telescope on board Hinode, we investigate the spatial distribution
of the power spectral density of the oscillatory signal in and around
the active region NOAA 10935. The G-band data show that in the umbra
the oscillatory power is suppressed in all frequency ranges. On
the other hand, in CaII H intensity maps oscillations in the umbra,
so-called umbral flashes, are clearly seen with the power peaking around
5.5mHz. The CaII H power distribution shows the enhanced elements with
the spatial scale of the umbral flashes over most of the umbra, but
there is a region with suppressed power at the center of the umbra. The
origin and property of this node-like feature remain unexplained.
Title: Hinode SP Vector Magnetogram of AR10930 and Its
Cross-Comparison with MDI
Authors: Moon, Yong-Jae; Kim, Yeon-Han; Park, Young-Deuk; Ichimoto,
Kiyoshi; Sakurai, Takashi; Chae, Jongchul; Cho, Kyung Suk; Bong,
Suchan; Suematsu, Yoshinori; Tsuneta, Saku; Katsukawa, Yukio; Shimojo,
Masumi; Shimizu, Toshifumi; Shine, Richard A.; Tarbell, Theodore D.;
Title, Alan M.; Lites, Bruce; Kubo, Masahito; Nagata, Shin'ichi;
Yokoyama, Takaaki
Bibcode: 2007PASJ...59S.625M
Altcode:
We present one Hinode Spectropolarimeter (SP) magnetogram of AR 10930
that produced several major flares. The inversion from Stokes profiles
to magnetic field vectors was made using the standard Milne-Eddington
code. We successfully applied the Uniform Shear Method for resolving
the 180° ambiguity to the magnetogram. The inversion gave very strong
magnetic field strengths (near 4500 gauss) for a small portion of area
in the umbra. Considering that the observed V-profile of 6301.5Å was
well-fitted as well as a direct estimation of the Zeeman splitting
results in 4300-4600 gauss, we think that the field strengths
should not be far from the actual value. A cross-comparison of the
Hinode SP and SOHO MDI high resolution flux densities shows that the
MDI flux density could be significantly underestimated by about a
factor of two. In addition, it has a serious negative correlation
(the so-called Zeeman saturation effect) with the Hinode SP flux
density for umbral regions. Finally, we could successfully obtain
a recalibrated MDI magnetogram that has been corrected for the
Zeeman saturation effect using not only a pair of MDI intensity and
magnetogram data simultaneously observed, but also the relationship
from the cross-comparison between the Hinode SP and MDI flux densities.
Title: Formation Process of a Light Bridge Revealed with the Hinode
Solar Optical Telescope
Authors: Katsukawa, Yukio; Yokoyama, Takaaki; Berger, Thomas E.;
Ichimoto, Kiyoshi; Kubo, Masahito; Lites, Bruce; Nagata, Shin'ichi;
Shimizu, Toshifumi; Shine, Richard A.; Suematsu, Yoshinori; Tarbell,
Theodore D.; Title, Alan M.; Tsuneta, Saku
Bibcode: 2007PASJ...59S.577K
Altcode: 2007arXiv0709.2527K
The Solar Optical Telescope (SOT) on-board Hinode successfully and
continuously observed the formation process of a light bridge in a
matured sunspot of the NOAA active region 10923 for several days with
high spatial resolution. During its formation, many umbral dots were
observed to be emerging from the leading edges of penumbral filaments,
and rapidly intruding into the umbra. The precursor of the light bridge
formation was also identified as a relatively slow inward motion of
the umbral dots, which emerged not near the penumbra, but inside the
umbra. The spectro-polarimeter on SOT provided physical conditions in
the photosphere around the umbral dots and the light bridges. We found
that the light bridges and the umbral dots had significantly weaker
magnetic fields associated with upflows relative to the core of the
umbra, which implies that there was hot gas with weak field strength
penetrating from the subphotosphere to near the visible surface inside
those structures. There needs to be a mechanism to drive the inward
motion of the hot gas along the light bridges. We suggest that the
emergence and the inward motion are triggered by a buoyant penumbral
flux tube as well as subphotospheric flow crossing the sunspot.
Title: Umbral Fine Structures in Sunspots Observed with Hinode Solar
Optical Telescope
Authors: Kitai, Reizaburo; Watanabe, Hiroko; Nakamura, Tahei; Otsuji,
Ken-ichi; Matsumoto, Takuma; UeNo, Satoru; Nagata, Shin'ichi; Shibata,
Kazunari; Muller, Richard; Ichimoto, Kiyoshi; Tsuneta, Saku; Suematsu,
Yoshinori; Katsukawa, Yukio; Shimizu, Toshifumi; Tarbell, Theodore D.;
Shine, Richard A.; Title, Alan M.; Lites, Bruce
Bibcode: 2007PASJ...59S.585K
Altcode: 2007arXiv0711.3266K
A high resolution imaging observation of a sunspot umbra was made with
the Hinode Solar Optical Telescope. Filtergrams at wavelengths of the
blue and green continua were taken during three consecutive days. The
umbra consisted of a dark core region, several diffuse components,
and numerous umbral dots. We derived basic properties of umbral dots
(UDs), especially their temperatures, lifetimes, proper motions,
spatial distribution, and morphological evolution. The brightness
of UDs is confirmed to depend on the brightness of their surrounding
background. Several UDs show fission and fusion. Thanks to the stable
condition of the space observation, we could for the first time follow
the temporal behavior of these events. The derived properties of the
internal structure of the umbra are discussed from the viewpoint of
magnetoconvection in a strong magnetic field.
Title: On Connecting the Dynamics of the Chromosphere and Transition
Region with Hinode SOT and EIS
Authors: Hansteen, Viggo H.; de Pontieu, Bart; Carlsson, Mats;
McIntosh, Scott; Watanabe, Tetsuya; Warren, Harry P.; Harra, Louise K.;
Hara, Hirohisa; Tarbell, Theodore D.; Shine, Dick; Title, Alan M.;
Schrijver, Carolus J.; Tsuneta, Saku; Katsukawa, Yukio; Ichimoto,
Kiyoshi; Suematsu, Yoshinori; Shimizu, Toshifumi
Bibcode: 2007PASJ...59S.699H
Altcode: 2007arXiv0711.0487H
We use coordinated Hinode SOT/EIS observations that include
high-resolution magnetograms, chromospheric, and transition region
(TR) imaging, and TR/coronal spectra in a first test to study how
the dynamics of the TR are driven by the highly dynamic photospheric
magnetic fields and the ubiquitous chromospheric waves. Initial
analysis shows that these connections are quite subtle and require a
combination of techniques including magnetic field extrapolations,
frequency-filtered time-series, and comparisons with synthetic
chromospheric and TR images from advanced 3D numerical simulations. As a
first result, we find signatures of magnetic flux emergence as well as
3 and 5mHz wave power above regions of enhanced photospheric magnetic
field in both chromospheric, transition region, and coronal emission.
Title: Can High Frequency Acoustic Waves Heat the Quiet Sun
Chromosphere?
Authors: Carlsson, Mats; Hansteen, Viggo H.; de Pontieu, Bart;
McIntosh, Scott; Tarbell, Theodore D.; Shine, Dick; Tsuneta, Saku;
Katsukawa, Yukio; Ichimoto, Kiyoshi; Suematsu, Yoshinori; Shimizu,
Toshifumi; Nagata, Shin'ichi
Bibcode: 2007PASJ...59S.663C
Altcode: 2007arXiv0709.3462C
We use Hinode/SOT Ca II H-line and blue continuum broadband observations
to study the presence and power of high frequency acoustic waves at
high spatial resolution. We find that there is no dominant power at
small spatial scales; the integrated power using the full resolution of
Hinode (0.05'' pixels, 0.16'' resolution) is larger than the power in
the data degraded to 0.5'' pixels (TRACE pixel size) by only a factor
of 1.2. At 20 mHz the ratio is 1.6. Combining this result with the
estimates of the acoustic flux based on TRACE data of Fossum &
Carlsson (2006), we conclude that the total energy flux in acoustic
waves of frequency 5-40 mHz entering the internetwork chromosphere of
the quiet Sun is less than 800 W m$^{-2}$, inadequate to balance the
radiative losses in a static chromosphere by a factor of five.
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields with Hinode/SOT
Authors: Kubo, Masahito; Ichimoto, Kiyoshi; Shimizu, Toshifumi;
Tsuneta, Saku; Suematsu, Yoshinori; Katsukawa, Yukio; Nagata,
Shin'ichi; Tarbell, Theodore D.; Shine, Richard A.; Title, Alan M.;
Frank, Zoe A.; Lites, Bruce; Elmore, David
Bibcode: 2007PASJ...59S.607K
Altcode: 2007arXiv0709.1853K
Vector magnetic fields of moving magnetic features (MMFs) were well
observed with the Solar Optical Telescope (SOT) aboard the Hinode
satellite. We focused on the evolution of three MMFs with the SOT in
this study. We found that an MMF having relatively vertical fields
with the same polarity as the sunspot was detached from the penumbra
around the granules appearing in the outer penumbra. This suggests
that granular motions in the outer penumbra are responsible for
disintegration of the sunspot. Two MMFs with polarity opposite to
the sunspot are located around the outer edge of horizontal fields
extending from the penumbra. This is evidence that the MMFs with
polarity opposite to the sunspot are the prolongation of penumbral
horizontal fields. Redshifts larger than the sonic velocity in the
photosphere are detected for some of the MMFs with polarity opposite
to the sunspot.
Title: A Tale of Two Spicules: The Impact of Spicules on the Magnetic
Chromosphere
Authors: de Pontieu, Bart; McIntosh, Scott; Hansteen, Viggo H.;
Carlsson, Mats; Schrijver, Carolus J.; Tarbell, Theodore D.; Title,
Alan M.; Shine, Richard A.; Suematsu, Yoshinori; Tsuneta, Saku;
Katsukawa, Yukio; Ichimoto, Kiyoshi; Shimizu, Toshifumi; Nagata,
Shin'ichi
Bibcode: 2007PASJ...59S.655D
Altcode: 2007arXiv0710.2934D
We use high-resolution observations of the Sun in CaIIH (3968Å)
from the Solar Optical Telescope on Hinode to show that there are
at least two types of spicules that dominate the structure of the
magnetic solar chromosphere. Both types are tied to the relentless
magnetoconvective driving in the photosphere, but have very different
dynamic properties. ``Type-I'' spicules are driven by shock waves
that form when global oscillations and convective flows leak into
the upper atmosphere along magnetic field lines on 3--7minute
timescales. ``Type-II'' spicules are much more dynamic: they form
rapidly (in ∼ 10s), are very thin (≤ 200 km wide), have lifetimes
of 10-150s (at any one height), and seem to be rapidly heated to
(at least) transition region temperatures, sending material through
the chromosphere at speeds of order 50--150kms-1. The
properties of Type II spicules suggest a formation process that is
a consequence of magnetic reconnection, typically in the vicinity
of magnetic flux concentrations in plage and network. Both types of
spicules are observed to carry Alfvén waves with significant amplitudes
of order 20kms-1.
Title: Hinode Observations of the Onset Stage of a Solar Filament
Eruption
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Berger, Thomas
E.; Bobra, Monica; Davis, John M.; Jibben, Patricia; Kano, Ryohei;
Lundquist, Loraine L.; Myers, D.; Narukage, Noriyuki; Sakao, Taro;
Shibasaki, Kiyoto; Shine, Richard A.; Tarbell, Theodore D.; Weber, Mark
Bibcode: 2007PASJ...59S.823S
Altcode:
We used Hinode X-Ray Telescope (XRT) and Solar Optical Telescope (SOT)
filtergraph (FG) Stokes-V magnetogram observations, to study the
early onset of a solar eruption that includes an erupting filament
that we observe in TRACE EUV images. The filament undergoes a slow
rise for at least 20min prior to its fast eruption and strong soft
X-ray (SXR) flaring; such slow rises have been previously reported,
and the new Hinode data elucidate the physical processes occurring
during this period. XRT images show that during the slow-rise phase,
an SXR sigmoid forms from apparent reconnection low in the sheared core
field traced by the filament, and there is a low-level intensity peak
in both EUV and SXRs during the slow rise. MDI and SOT FG Stokes-V
magnetograms show that the pre-eruption filament is along a neutral
line between opposing-polarity enhanced network cells, and the SOT
magnetograms show that these opposing fields are flowing together
and canceling for at least six hours prior to eruption. From the MDI
data we measured the canceling network fields to be ∼ 40G, and we
estimated that ∼ 1019 Mx of flux canceled during the
five hours prior to eruption; this is only ∼ 5% of the total flux
spanned by the eruption and flare, but apparently its tether-cutting
cancellation was enough to destabilize the sigmoid field holding the
filament and resulted in that field's eruption.
Title: What are 'Faculae'?
Authors: Berger, T. E.; Title, A. M.; Tarbell, T.; Rouppe van der
Voort, L.; Löfdahl, M. G.; Scharmer, G. B.
Bibcode: 2007ASPC..369..103B
Altcode:
We present very high resolution filtergram and magnetogram observations
of solar faculae taken at the Swedish 1-meter Solar Telescope (SST)
on La Palma. Three datasets with average line-of-sight angles of 16,
34, and 53 degrees are analyzed. The average radial extent of faculae is
at least 400~km. In addition we find that contrast versus magnetic flux
density is nearly constant for faculae at a given disk position. These
facts and the high resolution images and movies reveal that faculae are
not the interiors of small flux tubes - they are granules seen through
the transparency caused by groups of magnetic elements or micropores
``in front of'' the granules. Previous results which show a strong
dependency of facular contrast on magnetic flux density were caused
by bin-averaging of lower resolution data leading to a mixture of
the signal from bright facular walls and the associated intergranular
lanes and micropores. The findings are relevant to studies of total
solar irradiance (TSI) that use facular contrast as a function of disk
position and magnetic field in order to model the increase in TSI with
increasing sunspot activity.
Title: Estimate on SOT Light Level in Flight with Throughput
Measurements in SOT Sun Tests
Authors: Shimizu, T.; Kubo, M.; Tarbell, T. D.; Berger, T. E.;
Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Miyashita, M.; Noguchi,
M.; Nakagiri, M.; Tsuneta, S.; Elmore, D. F.; Lites, B. W.
Bibcode: 2007ASPC..369...51S
Altcode:
The SOT (Solar Optical Telescope, e.g., Shimizu 2004) optical
system consists of 50cm-aperture optical telescope (OTA) and focal
plane instrument (FPP). The solar light into the telescope penetrates
through many optical elements located in OTA and FPP before illuminating
CCDs. Natural solar light was fed to the integrated SOT in sun tests for
verifying various optical aspects including the confirmation of photon
throughput. CCD exposures provide the number of photons accumulated
in an exposure duration with a clean-room test condition. To estimate
the absolute intensity of the solar light at the telescope entrance
in the clean-room test condition, we developed a pinhole-PSD sensor
for simultaneous monitoring the solar light outside the clean room
and measured the transmission of light through two flat mirrors of
the heliostat and clean-room entrance window glass as a function of
wavelength. The PSD sensor was pre-calibrated with continuous monitoring
the solar light in a day long under a clear constant sky condition,
determining the earth atmospheric attenuation and the PSD output for
the solar light on orbit. These throughput measurements have provided
an estimate on photon throughput for the SOT flight model. The results
confirm suitable number of photons without saturation for proper CCD
exposures in flight.
Title: Performance Characteristics of the Solar-B Spectro-Polarimeter
Authors: Lites, B. W.; Elmore, D. F.; Streander, K. V.; Hoffmann,
C. M.; Tarbell, T. D.; Title, A. M.; Shine, R. A.; Ichimoto, K.;
Tsuneta, S.; Shimizu, T.; Suematsu, Y.
Bibcode: 2007ASPC..369...55L
Altcode:
The Focal Plane Package (FPP) of the Solar Optical Telescope (SOT)
includes the first precision Spectro-Polarimeter (SP) for solar space
observations. The FPP/SP will provide high precision measures of
the vector magnetic field in the solar photosphere. Here we present
some as-built performance specifications for the entire system of
telescope + polarimeter. The FPP-SP system represents significant
gains in several aspects over existing spectro-polarimetric systems;
notably, angular resolution, polarimetric accuracy, spectral purity,
and most importantly, temporal continuity of stable, high angular
resolution. In this short summary of the poster, a few of the
performance characteristics of the SP are presented.
Title: Calibration of the SOT Polarization
Authors: Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Katsukawa, Y.;
Noguchi, M.; Nakagiri, M.; Miyashita, M.; Tsuneta, S.; Tarbell, T. D.;
Shine, R. A.; Hoffmann, C. M.; Cruz, T.; Lites, B. W.; Elmore, D. F.
Bibcode: 2007ASPC..369...39I
Altcode:
Calibration of SOT polarization property was performed using natural
sunlight and well calibrated sheet polarizer (linear and circular)
placed on the entrance of the telescope. The polarimeter response
matrices were determined for the spectropolarimeter (SP) and the
narrowband filter imager (NFI), and it is shown that they are well
behave as predicted and constant over the field of view. The crosstalk
between I,Q,U,V will be suppressed to the negligible level at the
photometric accuracy of 10^{-3} after the calibration with the obtained
matrices. The sensitivity of SOT on linear and circular polarizations
at each wavelength observed by NFI are also obtained.
Title: Calibration of SOT Dopplergrams
Authors: Katsukawa, Y.; Ichimoto, K.; Sekii, T.; Suematsu, Y.; Tsuneta,
S.; Shine, R. A.; Tarbell, T. D.
Bibcode: 2007ASPC..369...43K
Altcode:
Narrow-band Filter Imager on SOT provides Dopplergrams (DGs) which
are images of Doppler (line- of-sight) velocities. Observations with
DGs are critically important in studies of photospheric dynamics and
helioseismology. The primary photospheric line used for DGs is Fe I 5576
Å which is a line insensitive to Zeeman effect. We made a calibration
function for the 5576 Å DGs to get actual Doppler velocities from
velocity indexes using an atlas spectrum and simulated transmission
profiles for the tunable filter (TF) on SOT. Using data sets taken
in the natural sun-light test, we quantitatively evaluated accuracy
of the DGs by comparing the rotational speed of the Sun measured
with DGs with the expected one. There was a little systematic error
in the velocity obtained by SOT, but the error was less than 20 %
of the predicted velocities.
Title: Examinations of the Relative Alignment of the Instruments
on SOT
Authors: Okamoto, T. J.; Katsukawa, Y.; Shimizu, T.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Tarbell, T. D.
Bibcode: 2007ASPC..369...47O
Altcode:
We report the results of the examination about the relative alignment
among the instruments on SOT. We employ a test data set obtained in the
natural sun-light test in May 2005, which has had a grid pattern over
the entire FOV. SOT has the filtergraph (FG) and the spectro-polarimeter
(SP). The FG consists of six broadband filter imagers (BFI) and six
narrowband filter imagers (NFI). We examined the displacements among
the images taken with different filters to an accuracy of better than
0.1 pixel corresponding to 0.02''. It is important to know relative
displacements and plate scales of these instruments for accurate
alignment of observational data. We note that the values measured in
our work are relative and it is needed to decide the absolute values
with another way.
Title: Vector Spectropolarimetry of Dark-cored Penumbral Filaments
with Hinode
Authors: Bellot Rubio, L. R.; Tsuneta, S.; Ichimoto, K.; Katsukawa,
Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu,
Y.; Tarbell, T. D.; Title, A. M.; del Toro Iniesta, J. C.
Bibcode: 2007ApJ...668L..91B
Altcode: 2007arXiv0708.2791B
We present spectropolarimetric measurements of dark-cored penumbral
filaments taken with Hinode at a resolution of 0.3". Our observations
demonstrate that dark-cored filaments are more prominent in polarized
light than in continuum intensity. Far from disk center, the Stokes
profiles emerging from these structures are very asymmetric and show
evidence for magnetic fields of different inclinations along the
line of sight, together with strong Evershed flows of at least 6-7 km
s-1. In sunspots closer to disk center, dark-cored penumbral
filaments exhibit regular Stokes profiles with little asymmetries due
to the vanishing line-of-sight component of the horizontal Evershed
flow. An inversion of the observed spectra indicates that the magnetic
field is weaker and more inclined in the dark cores as compared with
the surrounding bright structures. This is compatible with the idea
that dark-cored filaments are the manifestation of flux tubes carrying
hot Evershed flows.
Title: Emergence of Small-Scale Magnetic Loops in the Quiet-Sun
Internetwork
Authors: Centeno, R.; Socas-Navarro, H.; Lites, B.; Kubo, M.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Shimizu, T.; Nagata, S.
Bibcode: 2007ApJ...666L.137C
Altcode: 2007arXiv0708.0844C
We study the emergence of magnetic flux at very small spatial
scales (less than 2") in the quiet-Sun internetwork. To this aim,
a time series of spectropolarimetric maps was taken at disk center
using the instrument SP/SOT on board Hinode. The LTE inversion of
the full Stokes vector measured in the Fe I 6301 and 6302 Å lines
allows us to retrieve the magnetic flux and topology in the region
of study. In the example presented here, the magnetic flux emerges
within a granular structure. The horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field disappear, while the vertical dipoles
drift-carried by the plasma motions-toward the surrounding intergranular
lanes. These events take place within typical granulation timescales.
Title: Data Archive of the Hinode Mission
Authors: Matsuzaki, K.; Shimojo, M.; Tarbell, T. D.; Harra, L. K.;
Deluca, E. E.
Bibcode: 2007SoPh..243...87M
Altcode:
All of the Hinode telemetry data are to be reformatted and archived
in the DARTS system at ISAS and mirrored to data centers around
the word. The archived data are distributed to users through the
Internet. This paper gives an overview of the files in the archive,
including the file formats. All formats are portable and have
heritage from the previous missions. From the reformatted files, index
information is created for faster data search. Users can perform queries
based on information contained in the index. This allows for searches
to return observations that conform to particular observing conditions.
Title: Chromospheric Micro-jets Discovered Above Sunspot Penumbrae
Authors: Katsukawa, Yukio; Tsuneta, S.; Suematsu, Y.; Ichimoto, K.;
Shimizu, T.; Kubo, M.; Nagata, S.; Berger, T.; Tarbell, T.; Shine,
R.; Title, A.
Bibcode: 2007AAS...210.9413K
Altcode: 2007BAAS...39..219K
The Solar Optical Telescope (SOT) aboard HINODE allows us to observe
dynamical activities in the solar photosphere and the chromosphere
with high and stable image quality of 0.2 arcseconds. This superior
performance of SOT provides new findings of fine-scale transient
activities occurring in the chromosphere. In this paper, we report
discovery of fine-scale jet-like phenomena ubiquitously observed
above sunspot penumbrae. The jets are identified in image sequences
of a sunspot taken through a Ca II H line filter at 3968A. The Ca II
H line is sensitive to about 10^4 K plasma in the chromosphere. Their length is typically between 3000 and 10000km, and their
width is smaller than 500km. It is notable that their lifetime
is shorter than 1 minute. Those small spatial and temporal scale
possibly makes it difficult to identify the phenomena in existing
ground-based observations. The jets are easily identified when a
sunspot is located far from the disk center, and motion of the bright
features suggests that mass is erupted from lower chromosphere to upper
atmosphere. Velocities of the motion are estimated to be 50 to 100 km/s
from their lateral motion of intensity patterns. The velocities are much
faster than sound speeds in the chromosphere. A possible cause of such
high-speed jets is magnetic reconnection at the lower chromosphere
resulted from fluted magnetic configuration in penumbrae which is
suggested by vector magnetic field measurements in the photosphere.
Title: Hinode Data Calibration For Precise Image Co-alignment:
XRT vs. SOT
Authors: Shimizu, Toshifumi; DeLuca, E. E.; Lundquist, L.; Sakao,
T.; Kubo, M.; Narukage, N.; Kano, R.; Katsukawa, Y.; Ichimoto, K.;
Suematsu, Y.; Tsuneta, S.; Tarbell, T.; Shine, D.; Hinode Team
Bibcode: 2007AAS...210.9417S
Altcode: 2007BAAS...39Q.220S
From late October in 2006, Hinode solar optical telescope (SOT) has
started to produce series of 0.2-0.3 arcsec visible-light images,
revealing dynamical behaviors of solar magnetic fields on the
solar surface. Simultaneously, Hinode X-ray telescope (XRT) has been
providing 1 arcsec resolution X-ray images of the solar corona, giving
the location of heating and dynamics occuring in the corona. Precise
image co-alignment of SOT data on XRT data with sub-arcsec accuracy is
required to provide new information regarding connecting the corona to
the photosphere. This presentation will give an introduction of Hinode
between-telescopes' image co-alignment to SPD participants. For active
region observations with sunspots, sunspots can be used as fiducial to
co-align the data from the two telescopes each other. Satellite jitter
in order of 1 arcsec or less is included in the series of XRT data,
whereas image stabilization system (correlation tracker) removes the
satellite jitter from the series of SOT images. Telescope pointings show
orbital variation in order of a few arcsec, which can be well predicted
from Hinode orbit information. Modeling co-alignment is under study
and it is the only precise method for quiet Sun and limb observations.
Title: Magnetic Flux Emergence In Granular Convection: Radiative
MHD Simulations And Hinode SOT Observations
Authors: Cheung, Mark; Schüssler, M.; Moreno-Insertis, F.; Tarbell,
T.; SOT Team
Bibcode: 2007AAS...210.9425C
Altcode: 2007BAAS...39..221C
We model the emergence of buoyant magnetic flux from the convection
zone into the photosphere by means of 3D radiative MHD simulations
using the MURaM code. In a series of simulations, we study how
an initially buoyant magnetic flux tube rises in the presence of
granular convection. The simulations take into account the effects of
radiative energy exchange, ionization effects in the equation of state
and compressibility. An emphasis of this talk is the comparison of
observational diagnostics from the simulations with recent observations
from Hinode SOT.
Title: Hinode/SOT Observations Of Apparent "Thermal Plume" Motions
In A Solar Prominence
Authors: Berger, Thomas; Tarbell, T.; Slater, G.; Tsuneta, S.;
Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.; Shimizu, T.; Kubo, M.;
Nagata, S.
Bibcode: 2007AAS...210.9433B
Altcode: 2007BAAS...39..222B
We present 396.8 nm Ca II H-line observations of a large
hedgerow, or "sheet", prominence seen on the solar western limb
on 30-November-2006. The 16 second cadence observations show dark
channels rising vertically at speeds of approximately 10 km/sec to
heights of about 15 Mm above the limb. Many of the motions end in
vortical overturning near the top of the sheet . Bright downflows of
similar speed are also seen within the sheet, often in association
with a dark channel that has risen to the top of the sheet. The dark
channels are suggestive of hot material rising in thermal plumes
within the prominence sheet. Similarly, the bright material motions
appear to be density enhanced regions of turbulent downflow. Current
models of sheet prominences do not include the observed dynamics. In
these models, the prominence plasma is in a low-beta state and is
constrained to move only along magnetic field lines. However the
motions observed here are extremely complex, implying either that the
magnetic field lines are undergoing turbulent motion, thus tangling
and reconnecting constantly, or that the plasma is not constrained
by the field and is in a high-beta convective state. We measure the
motion of several representative "plumes" and downflows, estimate the
density and temperature of the prominence plasma, and suggest several
avenues for further investigation. This work was supported by
NASA under the Hinode/SOT contract NNM07AA01C.
Title: High Resolution Observation of Spicules in Ca II H with
Hinode/SOT
Authors: Suematsu, Yoshinori; Katsukawa, Y.; Ichimoto, K.; Tsuneta, S.;
Okamoto, T.; Nagata, S.; Shimizu, T.; Tarbell, T.; Shine, R.; Title, A.
Bibcode: 2007AAS...210.9411S
Altcode: 2007BAAS...39..219S
High cadence observation with a Ca II H broadband filtergraph
(passband of 0.25 nm) of the Solar Optical Telescope (SOT) aboard
HINODE has revealed dynamical nature of solar limb spicules. Thanks to a
diffraction-limited and low-scattered light property of the instrument,
we can track the detailed evolution of individual spicules for the first
time with a spatial resolution of 0.2 arcsec. The spicules in Ca II
H are typically several arcsec tall and have multi-thread structure;
each threads are a few tenth of arcsec wide. It should be stressed
that most spicules do not show a simple up-and-down motion along a
rigid path line. They start with bright structure emanating from Ca II
H bright region, get widen and diffused with time and ascent, showing
expansion with lateral or even helical motion in tall events. Small and
short lived spicules tend to fade out after ascent. We will present
new findings of spicule dynamics in different magnetic environments
and discuss about long standing controversy of its motion and evolution.
Title: Hinode/SOT Observation of Fine Structure of the Evershed Flow
Authors: Ichimoto, Kiyoshi; Suematsu, Y.; Tsuneta, S.; Katsukawa, Y.;
Shimojo, M.; Kubo, M.; Shimizu, T.; Shine, R.; Tarbell, T.; Title,
A.; Lites, B.; Elmore, D.; Yokoyama, T.; Nagaka, S.
Bibcode: 2007AAS...210.9408I
Altcode: 2007BAAS...39..218I
Small scale structure of the Evershed effect was studied using the
Spectropolarimeter (SP) and Broadband Filter Imager (BFI) of SOT aboard
Hinode. SP maps and high cadence continuum images of BFI coverting
entire sunspots are used to investigate the spatial distribution of
the flow field, brightness and magnetic fields. It is revealed that the
Evershed flow starts at the front edge of inwardly migrating penumbral
grains with an upward velocity component and turns to nearly holizontal
flow preferentially in dark lanes (or dark core of filaments) of the
penumbra. Our results are in general agreement with the well known
uncombed penumbral concept in which the Evershed flow takes place
in nearly holizontal field channels. We discovered a number of tiny
elongated regions in deep photosphere in which there is an obvious
upward motion of 1-1.5km/s distributing over the penumbra. They
could be identified as the 'foot points' of the individual Evershed
flow channels. Cross-correlation among the flow speed, intensity,
magnetic field strength and inclination, and distribution of string
down flows in and around the penumbra will also be discussed.
Title: Observational Evidence For The Ubiquity Of Strong Alfven
Waves In The Magnetized Chromosphere
Authors: De Pontieu, Bart; McIntosh, S. W.; Carlsson, M.; Hansteen,
V. H.; Schrijver, C. J.; Tarbell, T. D.; Title, A.; SOT Team
Bibcode: 2007AAS...210.9415D
Altcode: 2007BAAS...39R.219D
Hinode/SOT Ca II broadband observations show that Alfven waves with
significant amplitudes of order 10-20 km/s and periods of 150-300 s are
extremely ubiquitous in the magnetized middle to upper chromosphere. Our
observations focus on spicules at the limb, and straw-like features
associated with network and plage on the disk. We find that the
weak straw-like features and most spicules all undergo significant
transverse motions that are driven by Alfven waves. These waves are
seen to propagate both up- and downward, and may carry an energy flux
that is significant compared to both the local, coronal and solar wind
energy balance. We will provide estimates of the energy flux carried
by these waves, and will compare our observations with Alfven waves
that are observed in 3D numerical simulations that include advanced
radiative transfer treatment for the chromosphere. This work was
supported by NASA contract NNM07AA01C.
Title: A Tale of Two Spicules
Authors: McIntosh, Scott W.; De Pontieu, B.; Carlsson, M.; Hansteen,
V. H.; Schrijver, C. J.; Tarbell, T. D.; Title, A. M.; SOT Team
Bibcode: 2007AAS...210.9414M
Altcode: 2007BAAS...39..219M
Hinode/SOT Ca II broadband images and movies show that there are
several different types of spicules at the limb. These different
types are distinguished by dynamics on different timescales. The
first type involves up- and downward motion on timescales of 3-5
minutes. The dynamics of these spicules are very similar to those of
fibrils and mottles as observed on the disk. Recent work suggests that
these are driven by slow-mode magnetoacoustic shocks that form when
convective flows and global oscillations leak into the chromosphere
along magnetic flux tubes. The second type is much more dynamic with
typical lifetimes of 10-60 s. These spicules are characterized by
sudden appearance and disappearance that may be indicative of rapid
heating to TR temperatures. We will describe the properties of these
spicules in various magnetic environments (coronal hole, quiet Sun,
active region) and study the possible role of reconnection in driving
the second type of spicules. In addition, we will perform detailed
comparisons of these different types of jets with synthetic Ca images
derived from advanced 3D numerical simulations that encompass the
convection zone up through the corona.
Title: Magnetic Flux Emergence In The Quiet Sun Photosphere
Authors: Centeno, Rebecca; Lites, B.; Socas-Navarro, H.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Tsuneta, S.;
Katsukawa, Y.; Suematsu, Y.; Kubo, M.; Shimizu, T.
Bibcode: 2007AAS...210.9406C
Altcode: 2007BAAS...39..218C
We study the emergence of magnetic flux at very small spacial scales
(less than 1 arcsec) in the quiet Sun internetwork. To this aim, several
time series of spectropolarimetric maps were taken at disk center using
the instrument SP/SOT on board Hinode. The LTE inversion of the full
Stokes vector measured in the Fe I 6301 and 6302 lines will allow us
to retrieve the magnetic flux and topology in the region of study. We
find that the magnetic flux emerges typically within the granular
structures. In many cases, the horizontal magnetic field appears
prior to any significant amount of vertical field. As time goes on,
the traces of the horizontal field dissapear while the the vertical
dipoles drift -carried by the plasma motions- towards the surrounding
intergranular lanes. Sometimes they stay trapped there for a while
but they eventually either disappear by disgregation/cancelation
or agregate to other magnetic field concentrations giving rise to
larger flux elements. The time scale of these events is of the order
of 10-20 minutes.
Title: Formation of Moving Magnetic Features and Penumbral Magnetic
Fields
Authors: Kubo, Masahito; Ichimoto, K.; Shimizu, T.; Tsuneta, S.;
Suematsu, Y.; Katsukawa, Y.; Nagata, S.; Lites, B. W.; Frank, Z.;
Tarbell, T. D.; Shine, R. A.; Title, A. M.
Bibcode: 2007AAS...210.9410K
Altcode: 2007BAAS...39..218K
We investigate the formation process of Moving Magnetic Features
(MMFs) observed with Hinode/SOT. Moving magnetic features are small
magnetic elements moving outward in the moat region surrounding
mature sunspots. We derive vector magnetic fields of MMFs around
simple sunspots near the disk center. Most of MMFs with polarity
opposite to the sunspot have large redshift around the penumbral outer
boundary. We find that some of them have Doppler velocities of about
10 km/s and such large Doppler motion is observed only in the Stokes
V profile. The Stokes Q and U profiles in the same pixel do not have
any significant Doppler motions. Horizontal magnetic fields of the
penumbra frequently extend to the moat region and the MMFs having
horizontal fields with polarity same as the sunspot are formed. The
MMFs with polarity opposite to the sunspot appear around the outer
edge of the extending penumbral fields. We also find penumbral spines,
which have more vertical magnetic fields than the surroundings, branch
off at their outer edge and MMFs having relatively vertical fields
with polarity same as the sunspot are detached from the outer edge
of the branch. The branch of penumbral spine is formed when granular
cells in the moat region go into the penumbra.
Title: Ubiquitous Horizontal Magnetic Fields in the Quiet Solar
Photosphere as Revealed by HINODE Meaurements
Authors: Lites, Bruce W.; Socas Navarro, H.; Berger, T.; Frank,
Z.; Shine, R.; Tarbell, T.; Title, A.; Ichimoto, K.; Katsukawa,
Y.; Tsuneta, S.; Suematsu, Y.; Kubo, M.; Shimizu, T.; Nagata, S.;
Hinode Team
Bibcode: 2007AAS...210.6303L
Altcode: 2007BAAS...39..171L
Measurements with the HINODE Spectro-Polarimeter (SP) of the quiet
Sun allow characterization of the weak, mixed-polarity magnetic
flux at the highest angular resolution to date (0.3"), and with good
polarimetric sensitivity(0.025% relative to the continuum). The image
stabilization of the HINODE spacecraft allows long integrations with
degradation of the image quality only by the evolution of the solar
granulation. From the Stokes V profile measurements we find an average
solar "Apparent Flux Density" of 14 Mx cm-2, with significant Stokes V
signals at every position on the disk at all times. However, there are
patches of meso-granular size (5-15") where the flux is very weak. At
this high sensitivity, transverse fields produce measurable Stokes
Q,U linear polarization signals over a majority of the area, with
apparent transverse flux densities in the internetwork significantly
larger than the corresponding longitudinal flux densities. When viewed
at the center of the solar disk, the Stokes V signals (longitudinal
fields) show a preference for occurrence in the intergranular lanes,
and the Q,U signals occur preferably over the granule interiors,
but neither association is exclusive. Hinode is an international
project supported by JAXA, NASA, PPARC and ESA. We are grateful to the
Hinode team for all their efforts in the design, build and operation
of the mission.
Title: The Solar Optical Telescope on Hinode: Performance and
Capabilities
Authors: Tarbell, Theodore D.; Tsuneta, S.; SOT Team
Bibcode: 2007AAS...210.9401T
Altcode: 2007BAAS...39..217T
The Hinode (Solar B) satellite includes the Solar Optical Telescope
(SOT) with its 50 cm diameter Optical Telescope Assembly (OTA) and
Focal Plane Package (FPP), for near UV and visible observations of
the photosphere and chromosphere at very high (diffraction limited)
angular resolution. The FPP has a Spectropolarimeter (SP) for precision
measurements of photospheric vector magnetic fields over a 160 x
320 arcsecond field of view; a Narrowband Filter Imager (NFI) with
a tunable birefringent filter for magnetic, Doppler, and intensity
maps over the same field of view; and a Broadband Filter Imager (BFI)
for highest resolution images in six wavelengths (G band, Ca II H,
continua, etc.) over two thirds of that field of view. A polarization
modulator in the telescope allows measurement of Stokes parameters at
all wavelengths in the SP and NFI. This poster gives examples of SOT
observables from the performance verification and initial observing
phases of the mission. The SP routinely collects Stokes profiles with
spatial resolution 0.16 arc seconds (pixel) and rms noise less than
0.001. Initially the NFI only made magnetograms in Fe I 6302.5 with
rms noise less than 0.002; more recently it has begun to observe
the other photospheric and chromospheric lines available. The BFI
movies have unprecedented uniformity and stability for such high
spatial resolution; cadence can be 4 seconds or less. All images are
stabilized to 0.01 arc seconds by a tip tilt mirror and correlation
tracker. The process for requesting Hinode observations is described,
along with guidelines for SOT observing programs. Starting in May, 2007,
the Hinode data policy becomes completely open, with all data available
to the community immediately after receipt and reformatting at ISAS. Hinode is an international cooperative mission between JAXA/ISAS of
Japan, NASA of the United States, PPARC of the United Kingdom, and ESA.
Title: Can High Frequency Acoustic Waves Heat the Quiet Sun
Chromosphere?
Authors: Carlsson, Mats P. O.; De Pontieu, B.; Tarbell, T.; Hansteen,
V. H.; McIntosh, S.; SOT Team
Bibcode: 2007AAS...210.6306C
Altcode: 2007BAAS...39..172C
We use Hinode/SOT Ca II, G-band and blue continuum broadband
observations to study the presence and power of high frequency acoustic
waves at high spatial resolution. Previous observations with TRACE,
which were limited by the 1 arcsec resolution, and 1D numerical
simulations (Fossum & Carlsson, 2005) have been used to constrain
the possible role of high frequency waves in the heating of the quiet
Sun chromosphere. We will use the higher spatial resolution Hinode
data and comparisons with both 1D and 3D numerical models to study
the amount of high frequency power at smaller scales, and whether that
power is sufficient to heat the quiet Sun chromosphere.
Title: First Results from the Solar Optical Telescope on Hinode
Authors: Title, Alan M.; Tarbell, T.; Tsuneta, S.; SOT Team
Bibcode: 2007AAS...210.6301T
Altcode: 2007BAAS...39..171T
The Solar Optical Telescope (SOT) is a joint project of the National
Observatory of Japan and the Lockheed Martin Solar and Astrophysical
Laboratory. SOT consists of a 50 cm Gregorian telescope optimized to
reduce instrumental polarization and the Focal Plane Package (FPP). FPP
contains a version of the Advanced Stokes Polarimeters developed by
the High Altitude Observatory, a broadband filter system, and a tunable
birefringent filter. A correlation tracker in the FPP sends a control
signal to an active mirror in the telescope. Both the telescope and the
active mirror were developed by the National Astronomical Observatory
of Japan. The correlation tracking system reduces image motion in the
focal planes to +/- 0.02 arcseconds. The diffraction limited performance
of the SOT coupled with large format CCD’s and high data rates have
allowed the construction of high resolution line of sight and vector
magnetograms and imaging of phenomena on solar surface and off the
solar limb. This data are providing new insights into the processes
of flux emergence and disappearance from the scale of granulation to
active regions. High cadence observations of filaments, prominences,
and spicules have revealed surprising evolutionary features that include
alfven waves, current systems, and rapid reconnection. Movies of many
of these phenomena will be shown.
Title: Attempt to detect Aflven waves with Solar Optical Telescope
aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Katsukawa, Y.;
Shimizu, T.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9428T
Altcode: 2007BAAS...39..222T
Flux tube on the sun may carry linear and torsional Alfven waves
generated by photospheric motion. Photospheric motion of 2 km/s would
provide magnetic fluctuation of 40G for 1KG tube and for the Alfven
speed of 50km/s. This may be close to the detection limit of the Stokes
Q and U signals for flux tubes located in the sun center. However,
for flux tubes located near the limb, the fluctuation would be seen in
the Stokes V signal, and can be detectable. We also may be able
to confirm the 90 degree phase shift between magnetic fluctuation and
velocity fluctuation, which is easier to observe for flux tubes near
the limb. Detection of waves would be important in terms of coronal
heating and solar wind acceleration. An attempt to detect waves along
flux tubes will be reported.
Title: Discovery Of Cool Cloud-like Structures In The Corona With
Hinode Solar Optical Telescope
Authors: Okamoto, Takenori; Tsuneta, S.; Katsukawa, Y.; Ichimoto,
K.; Suematsu, Y.; Shimizu, T.; Nagata, S.; Shibata, K.; Tarbell, T.;
Shine, R.; Berger, T.; Lites, B.; Myers, D.
Bibcode: 2007AAS...210.9426O
Altcode: 2007BAAS...39..221O
A solar observation satellite Hinode (Japanese for sun rise) was
launched in September 2006.Hinode carried 3 advanced solar telescopes,
visible light telescope, EUV imaging spectrometer, and X-ray telescope
to simultaneously observe the photosphere, chromosphere, transition
region, and corona. In the performance verification phase of the Hinode
spacecraft with its telescopes, we observed an active region AR10921
near the west limb of the solar disk on November 9 2006. At this point,
we planned to observe spicules on the limb with a broadband filter
dedicated to Ca II H line (3968A). Ca II-H emission line (3968A) comes
from plasma with temperature of approx. 10(4) K, which is much lower
than the coronal temperature of 10(6-7) K. In addition to spectacular
spicules, we find a large cloud-like structure located 10,000-20,000
km above the limb. The cloud has a very complex fine structure with
dominant horizontal thread-like structure. Some features are moving
horizontally and also have clear vertical oscillatory motions. The
periods and amplitudes of these oscillations are 130-250 seconds and
200-850 km, respectively. The vertical oscillatory motion sometimes
has a coherence length as long as 16,000 km. We conclude that from
various observational features this vertical oscillation is a signature
of Alfven waves propagating along the horizontal magnetic fields. We
will discuss their origin and implications.
Title: Discovery Of Small-scale Horizontal Magnetic Structures On
The Solar Photosphere
Authors: Ishikawa, Ryohko; Tsuneta, S.; Suematsu, Y.; Ichimoto, K.;
Katsukawa, Y.; Nagata, S.; Ishobe, H.; Tarbell, T.; Lites, B. W.;
Title, A.
Bibcode: 2007AAS...210.9404I
Altcode: 2007BAAS...39..217I
We discover two different types of episodes on the appearance
of horizontal magnetic fields with Solar Optical Telescope aboard
Hinode. The first episode is an emergence of strong thin horizontal
magnetic fields associated with separating vertical components on
both ends. Its size is about two granules. We also detect strong area
asymmetry of the environment Stokes Vprofile for the bout 8 minutes
before the first emergence of the horizontal component. One of the
footpoints has very strong downflows (several km/s), while the region
with strong linear polarization signal has small blue shift, indicating
an upward-moving horizontal flux. The second episode appears to be
more ubiquitous. Linear polarization signals appear inside granules (not
in inter-granules). Their size is smaller than granules, and lifetime
is longer than several minutes. We will summarize the nature of the
two types of the horizontal magnetic fluxes, and discuss their origin.
Title: Hinode/SOT Observations of Sunspot Penumbral Dynamics and
Evolution
Authors: Shine, Richard A.; Hagenaar, M.; Tarbell, T.; Title, A.;
Lites, B.; Ichimoto, K.; Tsuneta, S.; Katsakawa, Y.; Suematsu, Y.;
Nagata, S.; Kubo, M.; Shimizu, T.
Bibcode: 2007AAS...210.9407S
Altcode: 2007BAAS...39..218S
The Solar Optical Telescope (SOT) on the Hinode satellite (launched
October 2006) has obtained long and nearly continuous time series of
several large sunspots including those in NOAA AR's 10923, 10925,
and 10930. Here we use high resolution movies taken primarily with
the broad band Ca II (396.8nm) and G band (430.5nm) channels and
magnetograms taken with the 630.2nm narrow band channel to study
the details and short term evolution of penumbral fine structures
as well as the long term evolution of the sunspots. We compute flow
maps and use space/time slices to track motions of Evershed clouds,
penumbral grains, and visualize oscillations. The data contain examples
of penumbral formation and disintegration including "orphan" penumbra
(i.e., penumbra without an obvious umbra). There is also an interesting
instance of "colliding" penumbra in AR 10930 as two sunspots of opposite
polarity converged. The zone of apparent shear was associated with
several flares. This work was supported by NASA contract NNM07AA01C
Title: Magnetic Landscape Of Solar Polar Region With Solar Optical
Telescope Aboard Hinode
Authors: Tsuneta, Saku; Suematsu, Y.; Ichimoto, K.; Shimizu, T.;
Katsukawa, Y.; Nagata, S.; Orozco Suárez, D.; Lites, B.; Shine, D.;
Tarbell, T.; Title, A.
Bibcode: 2007AAS...210.9405T
Altcode: 2007BAAS...39..218T
Solar polar region is the final destination for remnant magnetic
fields due to meridional flow and granular diffusion, and is very
important for the global solar dynamo. Hinode satellite carried out
high-resolution spectro-polarimetric observations for the Northern
pole on 2006 November 22 as a part of its performance verification
program. We find ubiquitous isolated (positive and negative) patches
in the Stokes V map (i.e. fields horizontal to local surface) all over
the Arctic circle. The Q (vertical to local surface) map indicates
scattered vertical flux tubes, which have bipolar feature in the U and
V maps. This suggests canopy-like structure of the strong isolated flux
tubes. This will be compared with equatorial landscape with similar
distance from the sun center. Strong flux tube and weaker ubiquitous
horizontal fields as represented by Stokes V would have implication
to the current understanding of the global and local dynamo.
Title: First Results From The Solar-B Mission, Part II
Authors: Tarbell, T.; Team, S. I.
Bibcode: 2006AGUFMSH23A0338T
Altcode:
This poster continues showing first results from the instruments on
Solar-B. The Solar-B Observatory is a highly capable satellite equipped
with three advanced solar telescopes. Its Solar Optical Telescope (SOT)
has an unprecedented 0.2 arcsec resolution for observation of the solar
atmosphere from space in multiple optical passbands. It will also,
for the first time, measure the vector magnetic fields from space. The
X-Ray Telescope (XRT) has broad temperature coverage and a spatial
a resolution three times as high as Yohkoh. The image cadence will
be significantly higher than Yohkoh's and a flare buffer will provide
exceptional capability for observing rapid changes at flare onset. The
EUV Imaging Spectrometer (EIS) has sensitivity ten times as high as the
SOHO CDS instrument and covers a broad range of transition region and
coronal temperatures. Flexible operating modes permit slit, slot and
raster options in a selectable number of spectral lines. Both XRT and
EIS have 2 arcsec spatial resolution (1 arcsec pixels). Solar-B is the
follow-up mission to the very successful Japan/UK/US Yohkoh mission. We
present a status report from the initial operation of the observatory,
showing some of the first observations obtained. Following a short
commissioning phase, science planning and regular operations are due
to begin January 2007. Starting six months after launch, all mission
data will be open and freely available to researchers shortly after
receipt at the DARTS data archive hosted in Japan.
Title: Magnetic Field Diagnostic Capability of Solar-B/SOT:
Filtergraph Instrument
Authors: Ichimoto, K.; Suematsu, Y.; Shimizu, T.; Katsukawa, Y.;
Tsuneta, S.; Tarbell, T. D.; Shine, R. A.; Hoffmann, C. M.; Title,
A. M.; Lites, B. W.; Elmore, D. F.; Streander, K. V.
Bibcode: 2006ASPC..358..189I
Altcode:
The Narrowband Filter Instrument (NFI) of the Solar Optical Telescope
onboard Solar-B provides 2D magnetograms/Dopplergrams with a tunable
Lyot filter (width ∼ 0.1 Å) in 6 selected wavelength bands, and
spatial sampling of 0.08 arcsec/px. The Zeeman-effect sensitivity of
NFI and the detection limits of weak magnetic fields are evaluated for
2 photospheric and 3 chromospheric lines. Magnetic-field retrievability
from the NFI observables is studied using synthetic Stokes profiles
of Fe I 5250 Å. We find that, with optimized wavelength sampling at 4
positions, the inferred magnetic field is sufficiently accurate under
the hypothesis of constant magnetic field and velocity along the LOS.
Title: Gamma Rays and the Evolving, Compact Structures of the 2003
October 28 X17 Flare
Authors: Schrijver, C. J.; Hudson, H. S.; Murphy, R. J.; Share, G. H.;
Tarbell, T. D.
Bibcode: 2006ApJ...650.1184S
Altcode:
The X17 flare on 2003 October 28 was observed by high-resolution
imaging or spectroscopic instruments on CORONAS, GOES, INTEGRAL,
RHESSI, SOHO, and TRACE. These spacecraft observed the temporal
evolution of the γ-ray positron-annihilation and nuclear de-excitation
line spectra, imaged the hard X-ray bremsstrahlung and EUV and UV
emission, and measured the surface magnetic field and subphotospheric
pressure perturbations. In the usual pattern, the onset of the flare
is dominated by particle acceleration and interaction, and by the
filling of coronal magnetic structures with hot plasma. The associated
positron-annihilation signatures early in the impulsive phase from
11:06 to 11:16 UT have a line-broadening temperature characteristic of
a few hundred thousand kelvins. The most intense precipitation sites
within the extended flare ribbons are very compact, with diameters
of less than 1400 km, and a 195 Å TRACE intensity that can exceed
7500 times the quiescent active-region value. These regions appear to
move at speeds of up to 60 km s-1. The associated rapidly
evolving, compact perturbations of the photosphere below these sites
excite acoustic pulses that propagate into the solar interior. Less
intense precipitation sites typically persist for several minutes
behind the advancing flare ribbons. After ~1 ks, the flare enters
a second phase, dominated by coronal plasma cooling and downflows
and by annihilation-line radiation characteristic of a photospheric
environment. We point out (1) that these detailed observations
underscore that flare models need to explicitly incorporate the
multitude of successively excited environments whose evolving signals
differ at least in their temporal offsets and energy budgets, if not
also in the exciting particle populations and penetration depths, and
(2) that the spectral signatures of the positron annihilation do not
fit conventional model assumptions.
Title: The Focal Plane Package of the Solar Optical telescope on
Solar B
Authors: Tarbell, Theodore D.
Bibcode: 2006SPD....37.3602T
Altcode: 2006BAAS...38..260T
The Solar-B satellite will be launched into a full-sun low-earth
orbit in the fall of 2006 from Japan's Uchinoura Space center. It
includes the 50-cm diameter Solar Optical Telescope with its Focal
Plane Package (FPP), for near-UV and visible observations of the
photosphere and chromosphere at very high (diffraction limited)
angular resolution. The FPP has a Spectro-Polarimeter (SP) for
precision measurements of photospheric vector magnetic fields over
a 160 x 320 arcsecond field of view; a Narrowband Filter Imager
(NFI) with a tunable birefringent filter for magnetic, Doppler, and
intensity maps over the same field of view; and a Broadband Filter
Imager (BFI) for highest resolution images in six wavelengths (G band,
Ca II H, continua, etc.) over two-thirds of that field of view. A
polarization modulator in the telescope allows measurement of Stokes
parameters at all wavelengths in the SP and NFI. The NFI wavelengths
include both photospheric and chromospheric lines (Fe I, Mg b, Na D,
H-alpha). All images are stabilized by a tip-tilt mirror and correlation
tracker. This presentation will include pictures and description of
the instrument, results from calibration and sun testing, portions
of the draft science plan, and some preliminary JOP's. Solar-B is an
international cooperative mission between JAXA/ISAS of Japan, NASA of
the United States, and PPARC of the United Kingdom. The Solar Optical
Telescope has been developed by the National Astronomical Observatory
of Japan, Mitsubishi Electric Company, and JAXA/ISAS. The FPP has
been developed by the Lockheed Martin Advanced Technology Center,
High Altitude Observatory, and NASA.
Title: Analysis of Solar Flare Ribbon Evolution: A Semiautomated
Approach
Authors: Saba, J. L. R.; Gaeng, T.; Tarbell, T. D.
Bibcode: 2006ApJ...641.1197S
Altcode:
We exploit a rare joint set of high-resolution, very high cadence
TRACE UV images and high-resolution magnetograms from SOHO MDI to
investigate the dynamical properties of flare ribbons in a GOES M1
class flare from NOAA active region 9236 on 2000 November 23 at 23:28
UT. Assuming that flare ribbons locate the chromospheric footpoints of
magnetic field lines reconnecting in the corona and that magnetic flux
is conserved, we measure the magnetic reconnection rate (in maxwells
per second) by overlaying the ribbons on co-registered magnetograms
and using intensity-based binary masks to track the magnetic flux
swept over by the evolving ribbons, and by assumption swept up in
the reconnection. In the event observed, the ribbons did not separate
with time but remained stationary while they brightened, lengthened,
and faded in place. Thus, the ribbons may be akin to hard X-ray flare
kernels moving antiparallel to each other, which others interpret as
caused by strong photospheric shear. The derived reconnection rate is
noisy, with little correlation between adjacent 1.4 s samples; the
peak rate for pixels summed over the ribbon is ~5×1018
Mx s-1 the average rise-phase rate is 10 times lower. The
``local'' rates for adjacent pixels added to the ribbon at adjacent
times show correlations with 1600 Å band intensities, supporting the
reconnection interpretation. For simple assumptions about geometry, the
reconnection appears fast (Vin>=0.01VA). The
peak reconnection rates, along with estimates of the current-sheet
length scale suggested by measured quantities, imply peak electric
fields of order 40 V cm-1. We discuss caveats to these
results.
Title: Self-focusing of Shocks and Hydrodynamic Cumulation in the
Solar Atmosphere
Authors: Tarbell, T.; Ryutova, M.
Bibcode: 2005AGUFMSH53A1251T
Altcode:
Network magnetic field in the solar atmosphere is concentrated
in isolated non-collinear thin flux tubes embedded in almost
non-magnetic environment with plasma beta β=8π pext/Bext2>>
1. Brought together by convective motions flux tubes collide and
reconnect. Post-reconnection dynamics of the photospheric magnetic flux
tubes is radically different from a low beta coronal plasma. Here
the reconnection does not give in situ heating, but it sets the
system in a highly unsteady state. After reconnection, the strongly
curved flux tubes behave as elastic bands: straightening they create
a sling-shot effect which generates complex 3D shock waves with the
curved surface. Self-focusing of these shocks occurs as they propagate
upward in the stratified atmosphere, producing a strong cumulative
effects. Depending on the geometry of the shock conversion, highly
concentrated energy may be either converted entirely into heat or into
strong jets, or be distributed between the two. These processes have
been observed in simultaneous observations of the solar atmosphere
from its surface to the corona obtained with the Solar and Heliospheric
Observatory (SOHO) and Transition Region and Coronal Explorer (TRACE)
showing a ubiquitous sequence of events that start from cancellation of
photospheric magnetic fields, pass through shock formation and result in
the transition region supersonic jets and microflares (Ryutova &
Tarbell, 2003, Physical Review Letters, 90, 191101). We also find
that lateral shocks produced by the reconnection of the same polarity
non-collinear magnetic flux tubes may cause the ubiquitous bright points
observed in sunspots and their environment. The mechanisms of energy
flow and release in the solar atmosphere involve fundamental physical
processes that are commonplace throughout astrophysics and laboratory
plasma physics. The advances in the coordinated observations with SOHO
and TRACE provide a unique opportunity to check the theoretical models,
and shed light on the general mechanisms of energy production, transfer
and release in stellar atmospheres and other astrophysical objects.
Title: The TRACE Inter-Network Oscillations (INO) Program II:
Observations of Limb and Coronal Hole Regions
Authors: McIntosh, S. W.; Crotser, D.; Leamon, R. J.; Fleck, B.;
Tarbell, T. D.
Bibcode: 2005AGUSMSH13C..06M
Altcode:
We will present results of the TRACE Inter-Network Oscillations (INO)
observing program from 2003 to the present. The INO program uses
near-simultaneous observations in the 1600Å and 1700Å UV continuum
pass bands as an acoustic probe of chromospheric structure. In
this poster we will discuss the INO observations of limb, polar and
coronal hole regions and show the key results found, thus far. These
observations offer us a remote means to study the structure and behavior
of the chromopsheric plasma topography at a potential driving base
for the heliospheric plasma system.
Title: The Focal Plane Package for the Solar Optical Telescope
on Solar-B
Authors: Tarbell, T. D.
Bibcode: 2005AGUSMSP43A..03T
Altcode:
Solar-B is a space science mission of the Japanese Aerospace Exploration
Agency (JAXA) and a NASA Solar Terrestrial Probes mission. It
includes the 50-cm aperture Solar Optical Telescope (SOT), with its
Focal Plane Package (FPP) designed for high resolution photospheric
and chromospheric imaging and spectro-polarimetry. There are also
two coronal instruments, the X-Ray Telescope and Extreme-ultraviolet
Imaging Spectrometer. Solar-B will be launched into a Sun-synchronous
polar orbit in August, 2006. The SOT is provided by JAXA and is
being built by the National Astronomical Observatory of Japan (NAOJ)
and Mitsubishi Electric Co. A team of Lockheed Martin, High Altitude
Observatory (HAO), and NAOJ scientists and engineers have built the
FPP instrument. This paper gives an overview of the science goals of
the FPP as well as the instrument performance characteristics. The
primary goal is to understand the coupling between the fine magnetic
structures in the photosphere and dynamic processes and heating
in the chromosphere and corona. The FPP consists of a narrow-band
tunable birefringent filter imager, broad-band interference filter
imager, and spectro-polarimeter (SP), essentially a space version
of the HAO Advanced Stokes Polarimeter. The image is stabilized by a
correlation tracker and active tilt mirror. The SP makes vector magnetic
measurements from Stokes spectra of the Fe I lines 630.1 and 630.2 nm,
with 0.16 arcsec pixels and field of view up to 164 x 328 arcsec. The
broad-band system takes diffraction-limited images (0.05 arcsec pixels)
in the Ca II H line, CN and G bandheads, and continuum bands. The
narrow-band system makes filtergrams, magnetograms, Dopplergrams, and
Stokes images in several photospheric lines, Mg b, Na D, and H-alpha,
similar to the SOUP filter at La Palma. It has 0.08 arcsec pixels and
field-of-view same as that of the SP. SOT and FPP have been calibrated
in great detail and have observed the sun in two end-to-end tests at
NAOJ. Sample results of these observations will be shown. Observing
programs and coordination with the other instruments and observatories
during the mission will be managed by SOT/FPP science planners, similar
to those of SOHO and TRACE. The FPP project is supported by NASA
(NAS8-01002).
Title: Calibration and Tesing of the Tunable Filter on Solar B
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Mitchell, K.;
Tavarez, L.; Rosenberg, W.
Bibcode: 2005AGUSMSP43A..04S
Altcode:
The tunable filter in the Focal Plane Package (FPP) on the Japanese
Solar B satellite, scheduled for launch in August 2006, was designed,
built, and tested at the Lockheed Martin Advanced Technology Center
(LMATC). It is an eight element wide field calcite filter (an improved
Lyot type) with a spectral resolution of about 100mÅ and a tuning range
of 11.87Å at 6302Å. Using 6 prefilters, it operates in bands covering
the 5172Å Fe I, 5250Å Fe I, 5576Å Fe I, 5896Å Na I, 6302Å Fe I,
and 6563Å H I lines. Here we describe the testing and calibrations
used to determine the tuning parameters as functions of temperature
and wavelength for the six bands. We also measure performance using
sunlight and laser sources in a standalone mode and integrated into
the FPP package. Images and derived magnetograms and Dopplergrams
using a low resolution solar image have also been obtained while
attached to the Solar B telescope and using a heliostat at the LMATC
in Palo Alto. In the course of this work we have also refined the
mathematical description for these types of filters, especially the
error terms that arise from residual misalignments. In particular,
we now believe we understand the intensity oscillations seen in this
and earlier Lyot tunable filters.
Title: Travel Time and Phase Analysis of Waves in the Lower Solar
Chromosphere
Authors: Fleck, B.; Armstrong, J.; Cacciani, A.; de Pontieu, B.;
Finsterle, W.; Jefferies, S. M.; McIntosh, S. W.; Tarbell, T. D.
Bibcode: 2005AGUSMSH13C..04F
Altcode:
In an effort to better understand how the chromospheric plasma and
magnetic fields are guiding, converting and dissipating acoustic waves,
we analyze high-cadence time series taken in Na I D2 589.0 nm and K I
769.9 nm that were obtained with the Magneto Optical Filters at Two
Heights (MOTH) experiment at the South Pole in January 2003. These
data are complemented by a very high spatial resolution time series
taken in Na D with the Swedish Vacuum Solar Telescope in June 1992. The
travel time maps, power maps, and phase diagrams show some unexpected
behaviour, in particular in and around active regions.
Title: The TRACE Inter-Network Oscillations (INO) Program I: Probing
Chromospheric Topography
Authors: McIntosh, S. W.; Bernhard, F.; Tarbell, T. D.
Bibcode: 2005AGUSMSH13C..05M
Altcode:
We will present results of the TRACE Inter-Network Oscillations (INO)
observing program from 2003 to the present. The INO program uses
near-simultaneous observations in the 1600Å and 1700Å UV continuum
pass bands as an acoustic probe of chromospheric structure. In the
two years of INO observations we have studied a large number of quiet
chromosphere and active regions as well as regions of the chromosphere
under coronal holes. In this poster we will discuss the diagnostic
methods applied to analyze the INO observations and the key results
found, thus far. These diagnostic methods offer us a remote means to
study the complex plasma topography of the solar chromosphere.
Title: The Next Generation of Chromospheric Measurements
Authors: Tarbell, T. D.
Bibcode: 2005AGUSMSH12A..06T
Altcode:
I discuss the new measurements which we know will happen, from
missions or observatories which are being developed now, as well as
the measurements which should happen for further progress. The future
is promising, with new missions such as Solar-B, SDO, and SunRise,
and new or upgraded observatories, such as SVST, DOT, GREGOR, ATST,
and FASR. I also point out significant needs for the future, such as
detailed chromospheric spectroscopy of the type which would have been
provided by NEXUS or similar instruments.
Title: Dynamics of the solar chromosphere. V. High-frequency
modulation in ultraviolet image sequences from TRACE
Authors: de Wijn, A. G.; Rutten, R. J.; Tarbell, T. D.
Bibcode: 2005A&A...430.1119D
Altcode: 2007arXiv0706.1987D
We search for signatures of high-frequency oscillations in the upper
solar photosphere and low chromosphere in the context of acoustic
heating of outer stellar atmospheres. We use ultraviolet image
sequences of a quiet center-disk area from the Transition Region
and Coronal Explorer (TRACE) mission which were taken with strict
cadence regularity. The latter permits more reliable high-frequency
diagnosis than in earlier work. Spatial Fourier power maps, spatially
averaged coherence and phase-difference spectra, and spatio-temporal
(kh,f) decompositions all contain high-frequency features
that at first sight seem of considerable intrinsic interest but actually
are more likely to represent artifacts of different nature. Spatially
averaged phase difference measurement provides the most sensitive
diagnostic and indicates the presence of acoustic modulation up to
f≈20 mHz (periods down to 50 s) in internetwork areas.
Title: Image stabilization system on SOLAR-B Solar Optical Telescope
Authors: Shimizu, Toshifumi; Nagata, Shin'ichi; Edwards, Chris;
Tarbell, Theodore; Kashiwagi, Yasuhiro; Kodeki, Kazuhide; Ito,
Osamu; Miyagawa, Hiroyuki; Nagase, Masayuki; Inoue, Syunsaku; Kaneko,
Kazumasa; Sakamoto, Yasushi; Ichimoto, Kiyoshi; Tsuneta, Saku; Miki,
Shiro; Endo, Makoto; Tabata, Masaki; Nakaoji, Toshitaka; Matsuzaki,
Keiichi; Kobayashi, Ken; Otsubo, Masashi; Suematsu, Yoshinori; Kumagai,
Kazuyoshi; Noguchi, Motokazu; Tamura, Tomonori; Nakagiri, Masao
Bibcode: 2004SPIE.5487.1199S
Altcode:
Extremely stable pointing of the telescope is required for images on the
CCD cameras to accurately measure the nature of magnetic field on the
sun. An image stabilization system is installed to the Solar Optical
Telescope onboard SOLAR-B, which stabilizes images on the focal plane
CCD detectors in the frequency range lower than about 20Hz. The system
consists of a correlation tracker and a piezo-based tip-tilt mirror with
servo control electronics. The correlation tracker is a high speed CCD
camera with a correlation algorithm on the flight computer, producing
a pointing error from series of solar granule images. Servo control
electronics drives three piezo actuators in the tip-tilt mirror. A
unique function in the servo control electronics can put sine wave
form signals in the servo loop, allowing us to diagnose the transfer
function of the servo loop even on orbit. The image stabilization
system has been jointly developed by collaboration of National
Astronomical Observatory of Japan/Mitsubishi Electronic Corp. and
Lockheed Martin Advanced Technology Center Solar and Astrophysics
Laboratory. Flight model was fabricated in summer 2003, and we measured
the system performance of the flight model on a laboratory environment
in September 2003, confirming that the servo stability within 0-20 Hz
bandwidth is 0.001-0.002 arcsec rms level on the sun.
Title: Chromospheric Oscillations in an Equatorial Coronal Hole
Authors: McIntosh, Scott W.; Fleck, Bernhard; Tarbell, Theodore D.
Bibcode: 2004ApJ...609L..95M
Altcode:
We report phase-difference and travel-time analyses of propagating
chromospheric oscillations in and around an equatorial coronal hole
as observed by TRACE. Our results suggest a significant change in
atmospheric conditions at the base of the chromosphere inside the
coronal hole relative to its boundary and quiet-Sun regions.
Title: EUVI: the STEREO-SECCHI extreme ultraviolet imager
Authors: Wuelser, Jean-Pierre; Lemen, James R.; Tarbell, Theodore
D.; Wolfson, C. J.; Cannon, Joseph C.; Carpenter, Brock A.; Duncan,
Dexter W.; Gradwohl, Glenn S.; Meyer, Syndie B.; Moore, Augustus S.;
Navarro, Rosemarie L.; Pearson, J. D.; Rossi, George R.; Springer,
Larry A.; Howard, Russell A.; Moses, John D.; Newmark, Jeffrey S.;
Delaboudiniere, Jean-Pierre; Artzner, Guy E.; Auchere, Frederic;
Bougnet, Marie; Bouyries, Philippe; Bridou, Francoise; Clotaire,
Jean-Yves; Colas, Gerard; Delmotte, Franck; Jerome, Arnaud; Lamare,
Michel; Mercier, Raymond; Mullot, Michel; Ravet, Marie-Francoise;
Song, Xueyan; Bothmer, Volker; Deutsch, Werner
Bibcode: 2004SPIE.5171..111W
Altcode:
The Extreme Ultraviolet Imager (EUVI) is part of the SECCHI instrument
suite currently being developed for the NASA STEREO mission. Identical
EUVI telescopes on the two STEREO spacecraft will study the structure
and evolution of the solar corona in three dimensions, and specifically
focus on the initiation and early evolution of coronal mass ejections
(CMEs). The EUVI telescope is being developed at the Lockheed Martin
Solar and Astrophysics Lab. The SECCHI investigation is led by the
Naval Research Lab. The EUVI"s 2048 x 2048 pixel detectors have a
field of view out to 1.7 solar radii, and observe in four spectral
channels that span the 0.1 to 20 MK temperature range. In addition to
its view from two vantage points, the EUVI will provide a substantial
improvement in image resolution and image cadence over its predecessor
SOHO-EIT, while complying with the more restricted mass, power, and
volume allocations on the STEREO mission.
Title: MHD Shocks: The Origin of the Solar Transition Region and
Coronal Sporadic Events
Authors: Ryutova, M. P.; Tarbell, T. D.
Bibcode: 2004ESASP.547..239R
Altcode: 2004soho...13..239R
No abstract at ADS
Title: Correlations on Arcsecond Scales between Chromospheric and
Transition Region Emission in Active Regions
Authors: De Pontieu, B.; Tarbell, T.; Erdélyi, R.
Bibcode: 2003ApJ...590..502D
Altcode:
The discovery of active region moss, i.e., dynamic and bright upper
transition region (TR) emission at chromospheric heights above active
region plage, provides a powerful diagnostic to probe the structure,
dynamics, energetics, and coupling of the magnetized solar chromosphere
and TR. Here we present an observational study of the interaction
of the chromosphere with the upper TR, by studying correlations (or
lack thereof) between emission at varying temperatures: from the low
chromosphere (Ca II K line), to the middle and upper chromosphere (Hα),
to the low TR (C IV λ1550 at 0.1 MK) and the upper TR (Fe IX/X λ171
at 1 MK and Fe XII λ195 at 1.5 MK). We use several data sets at high
cadence (24-42 s) obtained with the Swedish Vacuum Solar Telescope
(SVST, La Palma) and the Transition Region and Coronal Explorer
(TRACE). This correlation analysis from low chromosphere to upper
TR in active region plage quantifies and considerably expands on
previous studies. Our results elucidate various issues, such as (1)
how the heating mechanisms of the chromosphere and lower and upper TR
are related (if at all), (2) how important heating of spicular jets is
for the energy balance of the lower TR, (3) which timescales dominate
the dynamic behavior of the active region TR, and (4) whether the
spatial and temporal variability of moss can be used as a diagnostic
for coronal heating.
Title: TRACE Image Flat Field and Sensitivity Corrections
Authors: Nightingale, R. W.; Tarbell, T. D.; Wolfson, C. J.
Bibcode: 2003SPD....34.1710N
Altcode: 2003BAAS...35..839N
As of April 1, 2003, the TRACE instrument has been in orbit for 5
years. During this time the lumogen phosphor coating on the CCD has
degraded due to the flux of extreme ultraviolet (EUV) photons. We have
utilized flat field images obtained for the UV 1700 Å and broad-band
white light (WL) channels, together with the synoptic disk center,
and low-resolution ``dosimeter'' image data from throughout the
mission, to correct for the degradation at all of the TRACE UV and EUV
wavelengths. A set of time dependent power and multiplier parameters
have been determined from fitting these flat fields to the mission
synoptic data for the various UV wavelengths. By comparing the relative
EUV sensitivity at different positions on the detector throughout the
mission using images of the same active region at different pointings,
we have calibrated the sensitivity changes and flat fields at the
EUV wavelengths, including 171 Å and 195 Å. The WL flat field
images have not changed within +/-1.5 % over the mission to date. The
WL flat fields are also used in the corrections for all images, to
remove small artifacts intrinsic to the CCD and dust shadows common to
certain channels. All these corrections have now been implemented as an
update into the SolarSoft (SSW) routine TRACE_PREP.PRO, and normally
are automatically applied to the images after the dark pedestal and
current corrections. Plots of the time dependence of the sensitivity
and examples of the flat field corrections, along with their use in
TRACE_PREP.PRO, will be presented. This work was supported by the
TRACE project at LMSAL (contract NAS5-38099).
Title: Time Profiles of Magnetic Reconnection Measured from Flare
Ribbons
Authors: Tarbell, T.; Gaeng, T.; Saba, J.
Bibcode: 2003SPD....34.1614T
Altcode: 2003BAAS...35..835T
We study flare ribbons using observations of very high temporal
and spatial resolution to measure time profiles of magnetic
reconnection. TRACE images in the 1600 band show flare ribbons in
the low chromosphere, and we analyze M and X-class events with time
resolution as high as a few seconds during the buildup, impulsive and
decay phases. MDI high resolution magnetograms provide photospheric
fields for estimation of reconnection rates in Mx/s. Another M-class
event is studied with La Palma observations of very high spatial
resolution but lower cadence; H-alpha images are used to locate the
flare ribbons in this case. Both types of data show examples in weak
plage or network where the flare ribbons do not overlie significant
photospheric magnetic fields. We believe these ribbons are in the
chromospheric magnetic canopy, where fields are nearly horizontal
and flare heating can be widely separated from the photospheric
footpoints. In regions of stronger fields, we argue that careful spatial
coalignment of flare ribbons with photospheric fields can provide
information about the time profile of reconnection in the corona. The
reconnection rate is very noisy, with a correlation time of at most
a few seconds. During the gradual buildup to one of the M flares,
an exponential growth in reconnection rate by two orders of magnitude
over 40 minutes before the impulsive phase is observed. Rates during the
gradual decay of a long duration event are also measured. This work
was supported by NASA contracts NAG5-10483 (MDI) and NAS5-38099 (TRACE).
Title: MHD Shocks and the Origin of the Solar Transition Region
Authors: Ryutova, Margarita; Tarbell, Theodore
Bibcode: 2003PhRvL..90s1101R
Altcode:
Simultaneous observations of the solar atmosphere from its surface to
the corona obtained with the Solar and Heliospheric Observatory (SOHO)
and Transition Region and Coronal Explorer (TRACE) show a ubiquitous
sequence of events that start from cancellation of photospheric magnetic
fields, pass through shock formation, and result in transition region
supersonic jets and microflares. These results support a novel view of
the energy buildup in the solar atmosphere associated with a cascade
of shock waves produced by interacting network magnetic elements
in the photosphere and provide insight into the origin of the solar
transition region. The findings account for the general mechanisms
of energy production, transfer, and release throughout the Sun's and
stellar atmospheres.
Title: Interaction and Dynamics of the Photospheric Network Magnetic
Elements
Authors: Ryutova, M.; Tarbell, T. D.; Shine, R.
Bibcode: 2003SoPh..213..231R
Altcode:
Small-scale magnetic elements in the quiet photospheric network are
believed to play a key role in the energy flow from the solar surface
to upper layers of atmosphere. Their intense hydro-magnetic activity
includes merging and fragmentation of same polarity fluxes, `total'
or partial cancellation of neighboring flux elements of opposite
polarity, dynamic appearance and disappearance of compact bipoles,
etc. We study the general features of these processes, and show
that non-collinearity of flux tubes, sharp stratification of low
atmosphere and finite plasma beta lead to several specific effects
in the interacting flux tubes that may explain the morphological
properties of network magnetic field and also provide a mechanism
for the energy build up and release in the nearby chromosphere and
transition region. We show that during the collision of flux tubes in
the photosphere reconnection occurs regardless of whether the flux
tubes are of opposite or of the same polarity. But the dynamics of
reconnection products are significantly different and lead to different
macroscopic effects that can be observed.
Title: Estimating the Effects of JPEG Compression and Radiation on
the Accuracy of Vector Magnetic Fields Measurements for Solar-B
Authors: Lites, B.; Shine, R. A.; López Ariste, A.; Tarbell, T. D.
Bibcode: 2002AGUFMSH52A0471L
Altcode:
The Japanese Solar-B satellite, currently scheduled for launch in
September 2005, includes a spectro-polarimeter (SP) to precisely measure
the full Stokes polarization vector (I,Q,U,V) in the Fe I lines at
6302Å. These will be processed to produce vector magnetograms of the
solar surface using algorithms based on those for the Advanced Stokes
Polarimeter (ASP) as described in Skumanich, et al, 1997, ApJ Suppl
110. Accumulations of the raw images into time averaged I,Q,U,V images
will be done on board and the results will be 12 bit JPEG compressed to
make the best use of the available telemetry. Hence a single radiation
hit in a raw image affects the entire time average at that point. Also,
radiation spikes affect JPEG compression performance. Because of
concerns about these effects, we simulated them separately and in
combination using ASP data and radiation level measurements from the
TRACE satellite. Like TRACE, Solar-B will fly in a high inclination,
sun synchronous orbit and be exposed to radiation from the polar
radiation belts as well as the SAA. Since the SP detector will be
better shielded than that on TRACE, we hope that these will be an over
estimate of the effects. The results from the simulations are very
encouraging. We find that for active region magnetic fields we can use
JPEG to compress the data volume by more than a factor of 10 without
compromising the accuracy of the inferred magnetic field vector. The
radiation in the polar regions has little effect and even the much
stronger SAA radiation causes average perturbations that are less than
the formal errors for sunspot fields and about twice the formal errors
for plage fields. However, very weak field measurements will benefit
from less lossy compression and periods of low radiation. Of course,
the very strong radiation hits always produce artifacts. Compression
performance is affected only slightly so it will not be necessary to
avoid observations in the SAA because of excessive telemetry usage. This
work was supported by NASA contract NAS8-01002.
Title: Correlations on Arcsecond Scales Between Chromospheric and
Transition Region Structures in Active Regions
Authors: de Pontieu, B.; Tarbell, T.
Bibcode: 2002AGUFMSH52A0439D
Altcode:
The discovery of active region moss, i.e, dynamic and bright upper
transition region emission at chromospheric heights above active
region (AR) plage, provides a powerful diagnostic to probe the
structure, dynamics, energetics and coupling of the magnetized
solar chromosphere and transition region (TR). Here we present an
observational study of the interaction of the chromosphere with the
TR moss, by studying correlations (or lack thereof) between emission
at varying temperatures: from the low chromosphere (Ca II K-line),
to the middle and upper chromosphere (wings of Hα), to the low
transition region (C IV 1550 Å~at 0.1 MK), and the upper transition
region (Fe IX/X 171 Å~at 1 MK and Fe XII 195 Å~at 1.5 MK). We use
several datasets at high cadence (24 to 42 seconds) obtained with the
Swedish Vacuum Solar Telescope (SVST, La Palma) and the Transition
Region and Coronal Explorer (TRACE). This correlation analysis from
low chromosphere to upper TR in AR plage quantifies and considerably
expands on previous studies. Our results elucidate various issues,
such as: 1. how the heating mechanisms of the chromosphere and lower
and upper transition region are related (if at all), 2. how important
heating of spicular jets is for the energy balance of the lower TR,
3. the occurrence of significant periodic activity at all levels of the
transition region and its coherence over a wide range of temperatures,
4. which time scales dominate the dynamic behavior of the AR transition
region, and, 5. whether the spatial and temporal variability of moss
can be used as a diagnostic for coronal heating.
Title: Photospheric Magnetic Activities Responsible for Soft
X-Ray Pointlike Microflares. I. Identifications of Associated
Photospheric/Chromospheric Activities
Authors: Shimizu, T.; Shine, R. A.; Title, A. M.; Tarbell, T. D.;
Frank, Z.
Bibcode: 2002ApJ...574.1074S
Altcode:
By combining Yohkoh soft X-ray images with high-resolution magnetograms
simultaneously obtained at La Palma, we studied photospheric magnetic
signatures responsible for soft X-ray microflares (active-region
transient brightenings). In order to have a reliable correspondence
between the photosphere and the corona, we studied 16 pointlike
transient brightenings with X-ray source size less than 10" occurring
during periods when the seeing was excellent at La Palma, although a
lot of transient brightenings were in forms of multiple- or single-loop
structures. In half of the studied events, small-scale emergences
of magnetic flux loops are found in the vicinity of the transient
brightenings. Six events of that half show that a small-scale flux
emergence accompanies the X-ray brightening 5-30 minutes prior to
its onset. In the other half of the studied events, no apparent
evolutionary change of magnetic flux elements is found associated
with the transient brightenings. Many of these events are found in
rather strong magnetic fields, such as sunspots and pores, implying
that small-scale changes of magnetic flux are obscured or suppressed
by strong magnetic fields. The horizontal plasma flows derived from
local cross-correlation tracking of granules in continuum images are
suppressed at the feet of some X-ray transient brightenings.
Title: Extreme Ultraviolet Flux and Sensitivity Changes in TRACE
Images
Authors: Tarbell, T. D.; Nightingale, R. W.
Bibcode: 2002AAS...200.5504T
Altcode: 2002BAAS...34..732T
During the TRACE mission, the sensitivity of the instrument in both
UV and EUV channels has changed. This was expected from pre-flight
measurements of the effects of EUV flux on a lumogen-coated CCD detector
similar to the TRACE flight CCD. A mission-long record of EUV flux
on the CCD has been maintained using low-resolution ``dosimeter''
images. The correlations between EUV flux and UV sensitivity suggest
that most of the change can be attributed to the detector and not to
reductions in optical throughput. The techniques for UV calibration
described in our accompanying poster have not been successful for the
EUV channels. The Kuhn-Lin algorithm for deriving flat fields fails
due to the very high contrast and temporal variability of TRACE EUV
images. The synoptic images have not yet yielded useful information
either, due to low fluxes in quiet sun and intermittency and variability
among active regions. However, it is possible to measure the relative
EUV sensitivity at different positions on the detector throughout
the mission, using images of the same active region at different
pointings. By comparing these with the dosimeter images and UV results,
a preliminary calibration of sensitivity changes and flat fields in
171 Å and 195 Å have been derived. Examples of corrected images
are shown. This work was supported by the TRACE project at LMSAL
(contract NAS5-38099).
Title: Active Region Moss as a Diagnostic for the Thermal Evolution
of Chromospheric Spicule-Like Jets, and for Coronal Heating.
Authors: De Pontieu, B.; Tarbell, T.
Bibcode: 2002AAS...200.8807D
Altcode: 2002BAAS...34..790D
The recent discovery of active region moss, i.e, dynamic and bright
upper transition region emission at chromospheric heights above active
region plage, provides a powerful diagnostic to probe the structure,
dynamics, energetics and coupling of the magnetized solar chromosphere
and transition region. Here we present an observational study of the
interaction of the chromosphere with the TR moss, using a 2 hour
time sequence of high-cadence (30 s) TRACE C IV 1550 Å (0.1 MK),
Fe IX/X 171 Å (1 MK) and Fe XII 195 Å (1.5 MK) images, as well as
co-aligned, simultaneous SUMER spectra, and ground-based filtergrams
from the Swedish Vacuum Solar Telescope (SVST, La Palma) in the wings
of H-alpha. Detailed comparisons of the H-alpha filtergrams (at -700,
-350, +350 and +700 mÅ) with the TRACE C IV images reveals that there
is often a significant spatial correlation of the C IV emission with
the highly redshifted fibril or spicule-like structures in H-alpha +700
mÅ. The discovery and detailed quantitative study of this correlation
promises to shed light on the long outstanding issue of what role
chromospheric spicule-like jets play in the heating and momentum
balance of the outer atmosphere. We have also quantitatively studied
the auto-correlation and cross-correlation time-scales of moss using
a time sequence of high cadence TRACE 171 Å and 195 Å images. In
most of the active region moss patch we studied, we find that the
emission of 1 and 1.5 MK plasma is highly correlated, but often with
significant negative and positive time delays. Our results indicate that
the footpoints of hot coronal loops seem to undergo frequent cooling
and heating on time-scales of order fifteen minutes. By quantifying
these variations we can shed light on the temporal variability and on
the location of coronal heating in general.
Title: What Can We Learn about Magnetic Reconnection in the Solar
Corona from Joint SOHO/MDI and TRACE Observations?
Authors: Saba, J. L. R.; Gaeng, T.; Tarbell, T. D.
Bibcode: 2002AAS...200.6809S
Altcode: 2002BAAS...34..756S
High-resolution, high-cadence images from the Transition Region and
Coronal Explorer (TRACE) together with high quality line-of-sight
magnetograms from the Michelson Doppler Imager (MDI) on SOHO let
us examine signatures of magnetic reconnection and attempt to infer
associated physical parameters. Recently we analyzed joint TRACE UV and
MDI magnetogram data for the rise phase of a two-ribbon, GOES M1 class
flare from NOAA active region 9236 at 2000 Nov 23 23:28 UT. We estimated
the magnetic reconnection rate from the change in the photospheric
magnetic flux swept out by the evolving 1600 Å-band flare ribbons. For
simple assumptions with standard coronal parameters, the reconnection
appeared to be fast, with the inferred inflow velocity a significant
fraction of the Alfvén velocity. We extend our analysis to the peak
and decay phases of that event, and consider other reconnection events
observed jointly by TRACE and MDI, with guidance from coronal imaging
of the reconnection region by the SOHO/EUV Imaging Telescope or the
Yohkoh/Soft X-ray Telescope when not available from TRACE, and from
extrapolation of the MDI magnetograms. We look for correlations of,
e.g., the local reconnection rate with the instantaneous, peak, and
integrated intensities and the time rate of change of intensity of the
flare ribbons as a check on our analysis. The TRACE 1600 Å intensity
includes contributions from both chromospheric and transition region
(C IV) emission; it should be a proxy for the energy transmitted to the
lower atmosphere and perhaps correlated with the total energy released
by reconnection in the corona. This work is supported by NASA contracts
NAG5-10483 (MDI) and NAS5-38099 (TRACE).
Title: Ultraviolet Flat Fields, Sensitivity Changes, and Their
Removal from TRACE Images
Authors: Nightingale, R. W.; Tarbell, T. D.
Bibcode: 2002AAS...200.5505N
Altcode: 2002BAAS...34..732N
As of April 1, 2002, the TRACE instrument has been in orbit for 4
years. During this time the lumogen phosphor coating on the CCD has
degraded due to the flux of extreme ultraviolet (EUV) photons. Flat
field images have been obtained for the UV 1700 Å, 1216 Å,
and broad-band white light (WL) channels. Normalized flat field
responses have been calculated for each of these channels throughout
the mission to date. Recent 1700 Å images show up to about a 30 %
reduction in sensitivity near the center of the CCD relative to the
edges. Analyzing these flat fields together with the synoptic disk
center images throughout the mission, the flat fields and sensitivity
changes over time for all 5 UV channels have been determined. The
1700 Å flat field images serve as the basis for the lumogen loss
corrections in all UV channels (but not WL). A set of time dependent
power and multiplier parameters have been determined from fitting
these flat fields to the mission synoptic data for the various UV
wavelengths. The WL flat field images have not changed within +/- 1.5
% over the mission to date. The WL flat fields are also used in the
corrections for all UV images, to remove small artifacts intrinsic
to the CCD and dust shadows common to certain channels. All these
corrections have been implemented as an update into the SolarSoft (SSW)
routine TRACE_PREP.PRO, and normally are automatically applied to the
images after the dark pedestal and current corrections. Examples of
these corrections applied to images over time will be presented. This
work was supported by the TRACE project at LMSAL (contract NAS5-38099).
Title: A Study of Magnetic Reconnection using Simultaneous SOHO/MDI
and TRACE Data
Authors: Saba, J. L. R.; Gaeng, T.; Tarbell, T. D.
Bibcode: 2002mwoc.conf..175S
Altcode:
High-resolution, high-cadence images from the Transition Region and
Coronal Explorer (TRACE) together with high quality magnetograms from
the Michelson Doppler Imager (MDI) on SOHO let us examine signatures
of magnetic reconnection and attempt to infer associated physical
parameters such as the electric field strength in the corona. We
analyzed TRACE UV and MDI magnetogram data for a two-ribbon, GOES
M1-class flare from NOAA active region 9236 at 2000 Nov 23 23:28 UT,
with emphasis on the dynamical development of the flare ribbons in
the TRACE images. To estimate the rate of magnetic reconnection,
we chose two obvious flare ribbons which grew rapidly in the first
290-second sequence of high-cadence 1600Å flare response images. These
ribbons could be separated with a simple binary mask from ejecta
and other emission. They were located on strong fields of opposite
polarity and grew rapidly, then faded away in place. This suggests
that the emission was low in the atmosphere and well-aligned with the
photospheric footpoints of fieldlines reconnecting in the corona. Thus
we assume that the reconnection rate can be determined from the changing
photospheric magnetic flux swept out by the evolving ribbon mask. The
reconnection rate is very noisy, with a correlation time of at most a
few seconds. For simple assumptions with standard coronal parameters
(B ~ 100 G, np ~ 3 times 109, m cm-3
near a strong sunspot), the reconnection appears to be fast, with
the inferred inflow velocity a significant fraction of the Alfven
velocity. Some guidance from coronal imaging of the reconnection region
or Doppler measurement of inflow is needed to sharpen the constraints
on the length of the reconnecting current sheet and the strength of
the coronal electric field. This work was supported by NASA contracts
NAG5-8878, NAG5-10483 (MDI) and NAS5-38099 (TRACE).
Title: Solar magnetic reconnection viewed with TRACE and SOHO/MDI
Authors: Saba, J.; Gaeng, T.; Tarbell, T.
Bibcode: 2002cosp...34E2811S
Altcode: 2002cosp.meetE2811S
We combine high-resolution, high-cadence images from the Transition
Region and Coronal Explorer (TRACE) with high quality line-of-sight
magnetograms from the Michelson Doppler Imager (MDI) on SOHO to
examine signatures of solar magnetic reconnection and attempt
to infer associated physical parameters. We estimate the coronal
magnetic reconnection rate from the change in the photospheric
magnetic flux swept out by the evolving flare ribbons. For the first
event studied - a two-ribbon, GOES M1 class flare from NOAA active
region 9236 near central meridian on 2000 Nov 23 23:28 UT - we found
that the reconnection appeared to be fast, with the inferred inflow
velocity a significant fraction of the Alfvén velocity, assuming
standard coronal parameters and a simple geometry for the reconnecting
region. We consider other events and use (a) coronal imaging of the
reconnection region (as available from TRACE, the SOHO/EUV Imaging
Telescope, or the Yohkoh/Soft Xray Telescope), (b) extrapolation of
the photospheric magnetograms, and (c) correlative studies of the
reconnection rates with ribbon intensities, to check our assumptions
and assess the uncertainties of our results. This work is supported
by NASA contracts NAG5-10483 (MDI) and NAS5-38099 (TRACE).
Title: On the Correlation between Coronal and Lower Transition Region
Structures at Arcsecond Scales
Authors: Vourlidas, A.; Klimchuk, J. A.; Korendyke, C. M.; Tarbell,
T. D.; Handy, B. N.
Bibcode: 2001ApJ...563..374V
Altcode:
We compare the morphology of active region structures observed in
the 171 Å (T~9×105 K) and Lyα (T~2×104 K)
lines. The coronal data were obtained by the Transition Region and
Coronal Explorer (TRACE) in support of the Very High Angular Resolution
Ultraviolet Telescope (VAULT) sounding rocket launch, which acquired
subarcsecond resolution images of an active region in the Lyα line,
on 1999 May 7. Using a pair of calibrated, nearly simultaneous images,
we find that: (i) a very good correlation exists between the Lyα and
171 Å intensities in the TRACE moss regions, (ii) we can identify
several identical structures in some (but not all) moss areas, and
(iii) the correlations are greatly reduced at the footpoints of the
171 Å large-scale loops. We derive a lower limit for the Lyα emission
measure, under the assumption of effectively optically thin emission,
and compare it to the 171 Å emission measure. As in previous studies,
we find an excess of Lyα material compared to the amount expected
for a thermal conduction-dominated corona-chromosphere transition
region, even for structures that appear to be identical in the two
wavelengths. This result implies that some other mechanism besides
classical heat conduction from the corona must contribute to the
observed Lyα intensities. The observations do not support the idea
of a physically distinct cool loop component within active regions.
Title: Dynamics of the solar chromosphere. III. Ultraviolet brightness
oscillations from TRACE
Authors: Krijger, J. M.; Rutten, R. J.; Lites, B. W.; Straus, Th.;
Shine, R. A.; Tarbell, T. D.
Bibcode: 2001A&A...379.1052K
Altcode:
We analyze oscillations in the solar atmosphere using image sequences
from the Transition Region and Coronal Explorer (TRACE) in three
ultraviolet passbands which sample the upper solar photosphere and
low chromosphere. We exploit the absence of atmospheric seeing in
TRACE data to furnish comprehensive Fourier diagnostics (amplitude
maps, phase-difference spectra, spatio-temporal decomposition) for
quiet-Sun network and internetwork areas with excellent sampling
statistics. Comparison displays from the ground-based Ca Ii H
spectrometry that was numerically reproduced by Carlsson &
Stein are added to link our results to the acoustic shock dynamics
in this simulation. The TRACE image sequences confirm the dichotomy
in oscillatory behaviour between network and internetwork and show
upward propagation above the cutoff frequency, the onset of acoustic
shock formation in the upper photosphere, phase-difference contrast
between pseudo-mode ridges and the interridge background, enhanced
three-minute modulation aureoles around network patches, a persistent
low-intensity background pattern largely made up of internal gravity
waves, ubiquitous magnetic flashers, and low-lying magnetic canopies
with much low-frequency modulation. The spatio-temporal occurrence
pattern of internetwork grains is found to be dominated by acoustic
and gravity wave interference. We find no sign of the high-frequency
sound waves that have been proposed to heat the quiet chromosphere, but
such measurement is hampered by non-simultaneous imaging in different
passbands. We also find no signature of particular low-frequency
fluxtube waves that have been proposed to heat the network. However,
internal gravity waves may play a role in their excitation.
Title: Flow Map Studies of Supergranule and Mesogranule Evolution
from TRACE
Authors: Shine, R. A.; Frank, Z. A.; Tarbell, T. D.; Simon, G. W.
Bibcode: 2001AGUFMSH11A0702S
Altcode:
From 00:44 UT 22-April-2000 to 00:09 UT 29-April-2000 we obtained a
nearly continuous set of white light images using the Transition Region
and Corona Explorer (TRACE) satellite. A 384x384 arc second field of
view was used that tracked solar rotation from Stonyhurst longitudes
45E to 45W along the solar equator. The total time is nearly 7 days
with images taken every minute over most of the interval. The largest
temporal gap was 45m and there were only 9 gaps longer than 10m. The
area was mostly free of active regions. These images are broad band
white light with 0.5 arc second pixels. Granulation is well defined and
we used local correlation techniques (LCT) to compute flow maps of the
horizontal velocities with a resolution of about 5 arc seconds. The flow
map resolution and quality suffer somewhat near the longitude extrema
but the maps are usable throughout the 7 days to define supergranules
and mesogranules. We compute horizontal divergence to study the motions
of mesogranules and the evolution and lifetime of supergranules. When
enough telemetry capacity was available, we also obtained co-spatial
images in the TRACE Fe IX/X 171Å channel and the 1600Å channel. We
use these to study the response of the corona and chromosphere to the
photospheric motions. During times with particularly high telemetry
throughput, we took white light images every 30 seconds. This allows
us to empirically determine the noise in our flow maps using two
interleaved and disjoint sets of white light data, each with one minute
intervals. This work was supported by NASA contract NAS5-38099.
Title: A Study of Magnetic Reconnection Processes in Solar Active
Regions using TRACE, MDI and EIT Data
Authors: Gaeng, T. E.; Saba, J.; Tarbell, T.
Bibcode: 2001AGUFMSH42A0779G
Altcode:
We use high-resolution, high-cadence images from TRACE together with
high quality magnetograms from SOHO/MDI and EUV images from SOHO/EIT
to study signatures of magnetic reconnection and attempt to infer
associated physical parameters such as the electric field strength
in the corona. In this poster we present mainly results from the
study of the GOES M1-class flare from NOAA active region 9236 at 2000
Nov 23 23:28 UT, with emphasis on the dynamical development of the
flare ribbons in the TRACE images. To estimate the rate of magnetic
reconnection, we chose flare ribbons that could easily be separated
with binary masks from ejecta and other emission by non-interactive
IDL routines. The determined reconnection rate is very noisy, with
a correlation time of at most a few seconds. For simple assumptions
with standard coronal parameters (B ~ 100 G, np ~ 3 x
109 cm-3 near a strong sunspot), the reconnection
appears to be fast, with the inferred inflow velocity a significant
fraction of the Alfven velocity. Estimates of the uncertainties of
our measurements and analyses are derived from EIT images and simple
potential field models. More guidance from coronal imaging of the
reconnection regions or Doppler measurements of inflows are needed
to sharpen the constraints on the length of the reconnecting current
sheets and the coronal electric fields. This work was supported by
NASA contracts NAG5-8878, NAG5-10483 (MDI) and NAS5-38099 (TRACE).
>http://chippewa.nascom.nasa.gov/gaeng/EOF-Science/</a>
Title: Can the SOI/MDI Detect White Light Flares?
Authors: Gregory, S. E.; Myers, D.; Tarbell, T.; McIntosh, S.; Bush, R.
Bibcode: 2001AGUFMSH42A0765G
Altcode:
We examine flares observed jointly with high spatial resolution by
the SOHO instrument the Solar Oscillation Investigation/Michelson
Doppler Imager (SOI/MDI) and the Transition Region and Coronal Explorer
(TRACE). These include a GOES X1.1 class flare on 6 June 2000 and an
X5.7 flare on 14 July 2000. The June flare data provide a unique set
of line profiles across the flare site which help us better understand
potential instrumental effects in the SOI/MDI response to flares. We
locate the photospheric footpoints of the flares in both the SOI/MDI
and TRACE intensity images and examine their relationship with the
magnetograms. We also show that some flare kernels show emission in
both the line and the continuum in SOI/MDI data.
Title: Precision spectro-polarimeter for high-resolution observations
of solar magnetic fields
Authors: Lites, Bruce W.; Elmore, David F.; Streander, Kim V.; Akin,
David L.; Berger, Tom; Duncan, Dexter W.; Edwards, Chris G.; Francis,
Barbara; Hoffmann, Chris; Katz, Noah; Levay, Michael; Mathur, Dnyanesh;
Rosenberg, William A.; Sleight, Ericka; Tarbell, Theodore D.; Title,
Alan M.; Torgerson, Darrel
Bibcode: 2001SPIE.4498...73L
Altcode:
As a Japanese National space mission with international collaboration,
Solar-B (2005 launch) will carry a spectro- polarimeter (SP)
to be operated in visible light to obtain the first high angular
resolution, precision measurements of solar vector magnetic fields
from space. The SP is part of the Focal Plane Package (FPP) fed by a
diffraction-limited 50-cm optical telescope. The SP will be operated
exclusively at the photospheric 630 nm Fe I lines. It features a
rotating, low-order crystalline quartz retarder for polarization
modulation and a reflecting Littrow spectrograph design that is
shortened by using diffraction from the 12micrometers wide slit to
fill the grating. Polarization analysis is accomplished by a modified
Savart plate beam splitter. A custom CCD detector with two active
areas, one for each beam from the beam splitter, allows continuous
high duty-cycle sampling of polarization. The spectrograph slit will
sample a 0.16 x 164 arcsec2 rectangle of the solar image,
which may be scanned across the slit by up to +/- 160 arcsec in order
to build up vector magnetic field maps of the solar photosphere. Along
with simultaneous, co-spatial imaging and polarimetry with the filter
imagers of the FPP, the SP will provide a precise view of active and
quiet solar magnetic fields that control the structure, dynamics,
and energetics of the upper solar atmosphere.
Title: On the Magnetic Energy Avalanche in the Solar Atmosphere
Authors: Ryutova, M. P.; Tarbell, T. D.
Bibcode: 2001Ap&SS.277..153R
Altcode:
We discuss a mechanism of energy production associated with the acoustic
and MHD shocks produced by colliding and reconnecting flux tubes and
present the observational results showing a connection between the
dynamic changes in the photosphere and the high velocity and heating
events in the transition region. We suggest that these processes may
provide a constant energy supply for the origin of the fast wind and
help to advance studies of coronal dynamics.
Title: A Study of Chromospheric Oscillations Using the SOHO and
TRACE Spacecraft
Authors: Judge, Philip G.; Tarbell, Theodore D.; Wilhelm, Klaus
Bibcode: 2001ApJ...554..424J
Altcode:
We analyze line and continuum time-series data of the solar atmosphere,
with between 10 and 60 s cadence, using the MDI and SUMER instruments
on the SOHO spacecraft and the UV bandpasses on the TRACE satellite. The
co-aligned data sets sample spectral features formed from photosphere to
the middle transition region, spanning five decades in pressure, under
quiet-Sun and plage conditions. We discuss power, phase difference,
and coherence spectra, and examine data in the time domain. The
observed photospheric and chromospheric oscillations are strongly
coupled for frequencies between 2 and 8 mHz. Phase coherences decrease
with increasing height, with only occasional periods and locations of
observable coherence up to heights where transition region emission
lines are formed. The middle chromosphere (in the SUMER continua)
oscillates in several megameter (Mm) diameter coherent patches
with power predominantly in the 5-7 mHz range. The TRACE data,
formed in the upper photosphere, show smaller patterns superimposed
on these large-scale oscillations, resulting (at least in part)
from granulation. At the observed spatial scales, all the observed
properties point to p-modes, especially the ``pseudomodes'' just above
the acoustic cutoff frequency, as the dominant mode of the chromospheric
dynamics. Smaller scale ``acoustic event'' drivers, associated
with granular dynamics, appear to be less important. The predominant
internetwork chromospheric oscillations arise from regions much larger
horizontally than vertically. If propagating largely vertically, this
can naturally explain why the one-dimensional simulations of Carlsson
& Stein might be more successful than expected. The chromospheric
response to the p-mode driving is, however, intermittent in space and
time. Some of the intermittency appears to result from the interaction
of the upward-propagating waves with magnetic fields. Evidence for this
includes suppressed intensities and oscillations near quiet-Sun network
elements (which we dub ``magnetic shadows''), absence of oscillations
in internetwork regions neighboring plage magnetic fields, and a change
in character of the quiet-Sun internetwork oscillations between the
119 and 104 nm continua formed at 1 and 1.2 Mm. The latter might be
caused by canopy fields that form between these heights under typical
quiet-Sun conditions. A SUMER-only data set reported by Wikstøl et
al. has a factor of 3 more oscillatory power in the 104 nm continuum
than the data analyzed here, with stronger coherences extending into
the solar transition region. Together, these data support the general
picture that the chromosphere oscillates primarily in response to
forcing by the p-modes, they are therefore large-scale (several Mm
across) waves, and they are often strongly influenced by magnetic
effects (internetwork fields, or the overlying canopy), before the
oscillations even reach the transition region.
Title: Measurements of Magnetic Reconnection Rates and Inferred
Coronal Electric Fields in Solar Active Regions from Simultaneous
SOHO/MDI and TRACE observations
Authors: Gaeng, T.; Saba, J.; Tarbell, T.
Bibcode: 2001AGUSM..SH41A08G
Altcode:
One of the long-standing issues in coronal physics is the lack of
solid constraints on parameters that are fundamental to realistic
models of magnetic reconnection. For example, the electric field
strength above solar active regions is generally unknown, although it
has been estimated to about a factor of two (Forbes and Lin 2000) in a
specific large flare (Poletto and Kopp 1986). Recently, high resolution
high cadence UV and EUV observations from the Transition Region and
Coronal Explorer (TRACE) together with high quality magnetograms from
the Michelson Doppler Imager (MDI) on SOHO provide an opportunity
to approach this problem. These observations allow measuremenents
of the rate of magnetic reconnection, which may be converted (using
simple geometric models of the coronal fields) to electric fields
in the reconnection region. We use the MDI and TRACE data archives
to choose simultaneous TRACE observations and MDI high-resolution
magnetograms of active regions near disk center. We create movies
with these data to investigate reconnection rates in various coronal
transient events. Some earlier La Palma high resolution observations
in H-alpha showing reconnection rates may also be presented. This work
was supported by NASA contracts NAG5-8878 (MDI) and NAS5-38099 (TRACE).
Title: Photospheric Network as the Energy Source for the quiet-Sun
corona
Authors: Ryutova, M.; Habbal, S.; Woo, R.; Tarbell, T.
Bibcode: 2001SoPh..200..213R
Altcode:
We propose a mechanism for the formation of a magnetic energy avalanche
based on highly dynamic phenomena within the ubiquitous small-scale
network magnetic elements in the quiet photosphere. We suggest that
this mechanism may provide constant mass and energy supply for the
corona and fast wind. Constantly emerging from sub-surface layers,
flux tubes collide and reconnect generating magneto-hydrodynamic shocks
that experience strong gradient acceleration in the sharply stratified
photosphere/chromosphere region. Acoustic and fast magnetosonic
branches of these waves lead to heating and/or jet formation due to
cumulative effects (Tarbell et al., 1999). The Alfvén waves generated
by post-reconnection processes have quite a restricted range of
parameters for shock formation, but their frequency, determined by the
reconnection rate, may be high enough (ω≃0.1-2.5 s−1)
to carry the energy into the corona. We also suggest that the primary
energy source for the fast wind lies far below the coronal heights, and
that the chromosphere and transition region flows and also radiative
transient form the base of the fast wind. The continuous supply of
emerging magnetic flux tubes provides a permanent energy production
process capable of explaining the steady character of the fast wind
and its energetics.
Title: The Focal Plane Package for the Solar Optical Telescope
on Solar-B
Authors: Tarbell, T.
Bibcode: 2001AGUSM..SH31D01T
Altcode:
Solar-B is a Japanese space science mission of the Institute of
Space and Astronautical Sciences (ISAS), with major participation of
US and UK research groups. The mission includes the 50-cm aperture
Solar Optical Telescope (SOT), with its Focal Plane Package (FPP)
designed for high resolution photospheric and chromospheric imaging
and spectro-polarimetry. There are also two coronal instruments, the
X-Ray Telescope and Extreme-ultraviolet Imaging Spectrometer. Solar-B
will be launched into a Sun-synchronous polar orbit in August,
2005. The SOT is provided by ISAS and is being built by the National
Astronomical Observatory of Japan (NAOJ) and Mitsubishi Electric
Co. A team of Lockheed Martin, High Altitude Observatory (HAO), and
NAOJ scientists and engineers are designing the FPP instrument. This
talk gives an overview of the science goals of the FPP as well as
the current instrument design and performance characteristics. The
primary goal is to understand the coupling between the fine magnetic
structures in the photosphere and dynamic processes and heating
in the chromosphere and corona. The FPP consists of a narrow-band
tunable birefringent filter imager, broad-band interference filter
imager, and spectro-polarimeter (SP), essentially a space version
of the HAO Advanced Stokes Polarimeter. The image is stabilized by a
correlation tracker and active tilt mirror. The SP makes vector magnetic
measurements from Stokes spectra of the Fe I lines 630.1 and 630.2 nm,
with 0.16 arcsec pixels and field of view up to 164 x 328 arcsec. The
broad-band system takes diffraction-limited images (0.05 arcsec pixels)
in the Ca II H line, CN and G bandheads, and continuum bands. The
narrow-band system makes filtergrams, magnetograms, Dopplergrams, and
Stokes images in several photospheric lines, Mg b, and H-alpha. It has
0.08 arcsec pixels and field-of-view same as that of the SP. The SP and
filter imagers will usually observe simultaneously on the same target
region. High-level observing sequences and coordination with the other
instruments will be managed by FPP science planners, similar to those
of SXT and TRACE. The FPP project is supported by NASA (NAS8-01002).
Title: Energy Distribution of Solar Oscillation Modes Inferred from
Space-Based Measurements
Authors: Woodard, M. F.; Korzennik, S. G.; Rabello-Soares, C.; Kumar,
P.; Tarbell, T. D.; Acton, S.
Bibcode: 2001AGUSM..SP21C05W
Altcode:
We have measured the energy distribution of solar p- and f-mode
oscillations of angular degree and temporal frequency in the range
100<l<800 and 2<ν (mHz)<4 using helioseismology data from
the SOI/MDI instrument on the SOHO satellite. At temporal frequency ν
≈ 3 mHz, the surface velocity power per oscillation mode increases
slightly with angular degree between l = 100 and l=200, but decreases
rather steeply with l above l=200, in approximate agreement with
earlier findings from ground-based measurements. From this we infer
that the time-averaged energy per mode, which is theoretically related
to the modal surface velocity power, decreases steeply with l at fixed
frequency, over the entire observed l range. Specifically, at ν =3.1
mHz the energy per mode drops by a factor of ≈ 10 between l=150 and
l=650, a circumstance not quantitatively understood at present. This
research was supported by NASA and Stanford University.
Title: Intercomparison of SOUP, ASP, LPSP, and MDI magnetograms
Authors: Berger, T.; Lites, B.; Martinez-Pillet, V.; Tarbell, T.;
Title, A.
Bibcode: 2001AGUSM..SP51B12B
Altcode:
We compare simultaneous magnetograms of a solar active region taken by
the Advanced Stokes Polarimeter (ASP) and the Solar Optical Universal
Polimeter (SOUP) in 1998. In addition we compare magnetograms taken by
the La Palma Stokes Polarimeter (LPSP), the Michelson Doppler Imager
(MDI) on SOHO, and the SOUP instrument in 2000. The SOUP instrument on
the Swedish Vacuum Solar Telescope (SVST) attains the highest spatial
resolution but has the least understood calibration; the ASP on the Dunn
Solar Telescope (DST) at Sacramento Peak attains the highest magnetic
field precision. The goal of the program is to better quantify the
SOUP magnetograms and thereby study magnetic element dynamics in the
photosphere with higher precision.
Title: Formation of Compact Coronal Structures Associated with the
Emerging Magnetic Flux
Authors: Ryutova, M. P.; Shine, R.; Tarbell, T. D.
Bibcode: 2001AGUSM..SH32C01R
Altcode:
We study the events associated with the emergence of magnetic flux
in the photosphere occurring throughout the solar atmosphere from
its surface up to the low corona using coordinated observations from
Swedish Vacuum Solar Telescope (SVST) on La Palma, the TRACE satellite
and the MDI instrument on SOHO. The object of the observations is a
plage dominated initially (UT 08:01:03, June 10, 1999) by positive
polarity elements with about 0.3 magnetic filling factor near the
same polarity sunspot. High resolution MDI magnetograms are assembled
in a 6-hour movie and co-aligned with TRACE Fe IX/X 171 Å images of
the corona, SVST Ca II K-line images showing the low chromosphere and
Hα filtergrams showing plasma motions higher in the chromosphere. To
study line of sight motions, we used filtergrams taken in the +/- 350
~mÅ (and +/- 700 ~mÅ) wings of Hα . During the first two hours,
there are almost no changes (at the MDI resolution) in the initial
magnetic field pattern of studied region, and the 171 Å emission
above this region shows stable amorphous structures. Then a series of
events lead to the formation of two opposite polarity pores in the
target region and compact coronal loops above it with the following
chronology. First, opposite polarity small-scale flux tubes emerge
and interact with the existing plage elements. This is followed almost
immediately by strong Hα surges, whose peak activity lasts about 10
minutes. After this lag, enhanced emission in 171 Å takes the form
of a short-lived transient. During the next one hour (long before
the pore and compact coronal loops form), there are several new Hα
surges and coronal plasma jets whose activity correlates well with
remarkable changes in the photospheric fluxes which eventually form
pores. For a quantitative analysis we apply a theoretical model of
energy transport from subsurface motions associated with the emerging
magnetic flux. Strong disturbances generated in a limited surface
area may propagate upward like blast waves along a cone. This in
turn may cause a sequence of phenomena associated with forward and
reflected shocks, whose signatures are similar to the observations. The
process may last as long as significant changes in the photospheric
magnetic field occur, until it is suppressed by the strong fields in
the pores. Under some condition the established pore structure may
be accompanied by a current drive which leads to formation of the
coronal loops.
Title: Diffraction Pattern Analysis of Bright TRACE Flares
Authors: Lin, Andrew C.; Nightingale, Richard W.; Tarbell, Theodore D.
Bibcode: 2001SoPh..198..385L
Altcode:
A study of the diffraction patterns seen in TRACE images of bright
flare kernels was undertaken to better understand the properties of
the telescope. The diffraction pattern caused by light from a bright
flare kernel passing through the mesh supporting the filters at the
front of the TRACE telescope has been examined, and a method has been
developed to use this pattern to determine the zeroth order intensity
of flares that cannot be measured directly due to saturation of the
Analog to Digital Converter (ADC) in the CCD detection package. The
validity of this method is confirmed by testing it on a flare that
does not saturate the ADC. The diffraction pattern allows us to
measure intensities far brighter than the detection package allows;
the range has been effectively increased by at least 41 times. The light
scattered from any point was observed to be ≈20%, a significant amount
which may be affecting the image quality of the telescope. An accurate
determination of the ratio of the square slit size to slit spacing of
the wire mesh was obtained. Wavelength dispersion, the phenomenon that
as the higher-order diffracted peaks lie further from the center, they
spread out until double peaks are observed, has also been examined. This
effect is caused by two principal wavelengths, Fe ix at 171.073 Å and
Fe x at 174.507 Å in the TRACE 171 Å passband. This study is a part
of the TRACE Team educational outreach program.
Title: An Observational Manifestation of Magnetoatmospheric Waves
in Internetwork Regions of the Chromosphere and Transition Region
Authors: McIntosh, S. W.; Bogdan, T. J.; Cally, P. S.; Carlsson, M.;
Hansteen, V. H.; Judge, P. G.; Lites, B. W.; Peter, H.; Rosenthal,
C. S.; Tarbell, T. D.
Bibcode: 2001ApJ...548L.237M
Altcode:
We discuss an observational signature of magnetoatmospheric waves in
the chromosphere and transition region away from network magnetic
fields. We demonstrate that when the observed quantity, line or
continuum emission, is formed under high-β conditions, where β is
the ratio of the plasma and magnetic pressures, we see fluctuations in
intensity and line-of-sight (LOS) Doppler velocity consistent with the
passage of the magnetoatmospheric waves. Conversely, if the observations
form under low-β conditions, the intensity fluctuation is suppressed,
but we retain the LOS Doppler velocity fluctuations. We speculate that
mode conversion in the β~1 region is responsible for this change in
the observational manifestation of the magnetoatmospheric waves.
Title: Energy Distribution of Solar Oscillation Modes Inferred from
Space-based Measurements
Authors: Woodard, M. F.; Korzennik, S. G.; Rabello-Soares, M. C.;
Kumar, P.; Tarbell, T. D.; Acton, S.
Bibcode: 2001ApJ...548L.103W
Altcode:
We have measured the energy distribution of solar p- and f-mode
oscillations of angular degree and temporal frequency in the range
100<l<800 and 2<ν(mHz)<4 using helioseismology data
from the Solar Oscillations Investigation-Michelson Doppler Imager
instrument on the Solar and Heliospheric Observatory satellite. At
temporal frequency ν~3 mHz, the surface velocity power per oscillation
mode increases slightly with angular degree between l=100 and l=200 but
decreases rather steeply with l above l=200, in approximate agreement
with earlier findings from ground-based measurements. From this we
infer that the time-averaged energy per mode, which is theoretically
related to the modal surface velocity power, decreases steeply with l,
at fixed frequency, over the entire observed l-range. Specifically, at
ν=3.1 mHz, the energy per mode drops by a factor of ~10 between l=150
and l=650, a circumstance not quantitatively understood at present.
Title: In-flight performance of the Very high Angular resolution
ULtraviolet Telescope sounding rocket payload
Authors: Korendyke, Clarence M.; Vourlidas, A.; Cook, John W.; Dere,
Kenneth P.; Feldman, R.; Howard, Russell A.; Lilley, D. N.; Morrill,
Jeff S.; Moses, J. Daniel; Moulton, Norman E.; Moye, Robert W.;
Roberts, D. E.; Shepler, E. L.; Smith, J. K.; Socker, Dennis G.;
Spears, T. R.; Waymire, R. S.; Brown, Wayne E.; Tarbell, Theodore D.;
Berger, Tom; Handy, Brian N.
Bibcode: 2000SPIE.4139..340K
Altcode:
The Very high Angular Resolution ULtraviolet Telescope experiment was
successfully launched on May 7, 1999 on a Black Brant sounding rocket
vehicle from White Sands Missile Range. The instrument consists of a
30 cm UV diffraction limited telescope followed by a double grating
spectroheliograph tuned to isolate the solar Lyman (alpha) emission
line. During the flight, the instrument successfully obtained a series
of images of the upper chromosphere with a limiting resolution of
approximately 0.33 arc-seconds. The resulting observations are the
highest resolution images of the solar atmosphere obtained from space
to date. The flight demonstrated that subarc-second ultraviolet images
of the solar atmosphere are achievable with a high quality, moderate
aperture space telescope and associated optics. Herein, we describe
the payload and its in- flight performance.
Title: On the Transition Region Explosive Events
Authors: Ryutova, M. P.; Tarbell, T. D.
Bibcode: 2000ApJ...541L..29R
Altcode:
We describe the properties of high-velocity and explosive events in the
solar transition region determined from time series of data taken by
the Transition Region and Coronal Explorer and the SUMER instrument
on the Solar and Heliospheric Observatory (SOHO) simultaneously in
several chromospheric and transition region lines co-aligned with
high-resolution Michelson Doppler Imager (SOHO) magnetograms. We
outline what the various features of these events can tell us about
the heating mechanisms and formation of plasma flows. Our results
strongly support the mechanism of hydrodynamic cumulation of energy
associated with the cascade of shock waves produced by colliding
and reconnecting flux tubes in the photospheric network (as recently
discussed by T. D. Tarbell et al.). We find that the majority of the
explosive events are caused by the explosive instability occurring in
the presence of the behind-shock downflows, and less than 10% can be
explained by the direct collision of shock fronts.
Title: Time Variability of the ``Quiet'' Sun Observed with
TRACE. I. Instrumental Effects, Event Detection, and Discrimination
of Extreme-Ultraviolet Microflares
Authors: Aschwanden, Markus J.; Nightingale, Richard W.; Tarbell,
Ted D.; Wolfson, C. J.
Bibcode: 2000ApJ...535.1027A
Altcode:
The Transition Region and Coronal Explorer (TRACE) observed a
``quiet-Sun'' region on 1999 February 17 from 02:15 UT to 3:00 UT
with full resolution (0.5" pixel size), high cadence (125 s), and deep
exposures (65 and 46 s) in the 171 Å and 195 Å wavelengths. We start
our investigation of the time variability of ``quiet-Sun'' images
with a detailed analysis of instrumental and nonsolar effects, such
as orbital temperature variations, filtering of particle radiation
spikes, spacecraft pointing drift, and solar rotation tracking. We
quantify the magnitude of various noise components (photon Poisson
statistics, data digitization, data compression, and readout noise)
and establish an upper limit for the data noise level, above which
temporal variability can safely be attributed to solar origin. We
develop a pattern recognition code that extracts spatiotemporal events
with significant variability, yielding a total of 3131 events in 171 Å
and 904 events in 195 Å. We classify all 904 events detected in 195 Å
according to flarelike characteristics and establish a numerical flare
criterion based on temporal, spatial, and dynamic cross-correlation
coefficients between the two observed temperatures (0.9 and 1.4
MK). This numerical criterion matches the visual flare classification
in 83% of the cases and can be used for automated flare search. Using
this flare discrimination criterion we find that only 35% (and 25%) of
the events detected in 171 (and 195) Å represent flarelike events. The
discrimination of flare events leads to a frequency distribution of
peak fluxes, N(ΔF)~ΔF-1.83+/-0.07 at 195 Å, which is
significantly flatter than the distribution of all events. A sensitive
discrimination criterion of flare events is therefore important for
microflare statistics and for conclusions on their occurrence rate
and efficiency for coronal heating.
Title: Time Variability of the ``Quiet'' Sun Observed with
TRACE. II. Physical Parameters, Temperature Evolution, and Energetics
of Extreme-Ultraviolet Nanoflares
Authors: Aschwanden, Markus J.; Tarbell, Ted D.; Nightingale, Richard
W.; Schrijver, Carolus J.; Title, Alan; Kankelborg, Charles C.;
Martens, Piet; Warren, Harry P.
Bibcode: 2000ApJ...535.1047A
Altcode:
We present a detailed analysis of the geometric and physical
parameters of 281 EUV nanoflares, simultaneously detected with the
TRACE telescope in the 171 and 195 Å wavelengths. The detection and
discrimination of these flarelike events is detailed in the first paper
in this series. We determine the loop length l, loop width w, emission
measure EM, the evolution of the electron density ne(t) and
temperature Te(t), the flare decay time τdecay,
and calculate the radiative loss time τloss, the conductive
loss time τcond, and the thermal energy Eth. The
findings are as follows: (1) EUV nanoflares in the energy range of
1024-1026 ergs represent miniature versions
of larger flares observed in soft X-rays (SXR) and hard X-rays
(HXR), scaled to lower temperatures (Te<~2 MK),
lower densities (ne<~109 cm-3),
and somewhat smaller spatial scales (l~2-20 Mm). (2) The cooling
time τdecay is compatible with the radiative cooling
time τrad, but the conductive cooling timescale
τcond is about an order of magnitude shorter, suggesting
repetitive heating cycles in time intervals of a few minutes. (3)
The frequency distribution of thermal energies of EUV nanoflares,
N(E)~10-46(E/1024)-1.8 (s-1
cm-2 ergs-1) matches that of SXR microflares
in the energy range of 1026-1029, and exceeds
that of nonthermal energies of larger flares observed in HXR by a
factor of 3-10 (in the energy range of 1029-1032
ergs). Discrepancies of the power-law slope with other studies, which
report higher values in the range of a=2.0-2.6 (Krucker & Benz;
Parnell & Jupp), are attributed to methodical differences in the
detection and discrimination of EUV microflares, as well as to different
model assumptions in the calculation of the electron density. Besides
the insufficient power of nanoflares to heat the corona, we find also
other physical limits for nanoflares at energies <~1024
ergs, such as the area coverage limit, the heating temperature limit,
the lower coronal density limit, and the chromospheric loop height
limit. Based on these quantitative physical limitations, it appears
that coronal heating requires other energy carriers that are not
luminous in EUV, SXR, and HXR.
Title: The Solar-B Focal Plane Package
Authors: Berger, T. E.; Title, A. M.; Tarbell, T. D.; Lites, B. W.;
Elmore, D. F.
Bibcode: 2000SPD....31.0292B
Altcode: 2000BAAS...32..827B
Solar-B is a Japanese national space science mission of the Institute
of Space and Astronautical Sciences (ISAS) with participation from
US and UK research groups. The satellite consists of a 50-cm optical
telescope and Focal Plane Package (FPP) designed for high resolution
photospheric and chromospheric imaging and spectro-polarimetry as
well as two coronal instruments: the X-Ray Telescope (XRT) and the
Extreme-ultraviolet Imaging Spectrometer (EIS). Solar-B will be
launched into a Sun-synchronous orbit in August of 2004. A team of
Lockheed Martin Solar and Astrophysics Laboratory (LMSAL), High Altitude
Observatory, and ISAS personnel are designing the FPP instrument. It
consists of a narrow-band tunable birefringent filter system,
a wide band interference filter system, and a spectro-polarimeter
system for very high sensitivity Stokes polarimetry, all of which
will be fabricated at LMSAL. We describe the main science goals of
the FPP as well as the current instrument design and performance
characteristics. This work is supported by NASA contract NAS8-00014
(Solar-B FPP).
Title: Instrumental Effects and their Removal from TRACE Images
Authors: Tarbell, T. D.; Nightingale, R. N.; Metcalf, T. R.; Frank,
Z. A.; TRACE Team
Bibcode: 2000SPD....31.0291T
Altcode: 2000BAAS...32..827T
TRACE raw images often show fine structures at such high contrast
that compensation for instrumental effects is not necessary to study
their morphology and evolution. Nevertheless, TRACE team members have
gradually been developing the techniques and calibrations necessary
to understand and (sometimes) remove the principal instrumental
degradations. These degradations include CCD pedestal variation
with temperature and time, flat-field response, CCD sensitivity loss
varying with position and wavelength, electrical interference during
CCD readout, permanent dim pixels, intermittent hot pixels, overall
system point spread function, diffraction of EUV radiation by the front
entrance filters, scattered light at off-limb pointings, tracks of
electrons and protons from the radiation belts, and artifacts from JPEG
compression of solar strucures and the above defects. Characterization
and removal of some of these will be presented in the poster, such
as the following. A deconvolution routine can partially compensate
for the EUV diffraction, which is described in the adjacent poster by
Frank et al. White light flat fields are derived using the Kuhn-Lin
algorithm. CCD sensitivity degradation (presumably lumogen damage) is
measured both from crude UV and EUV flat fields and from mission-long
analysis of synoptic disk center images; combining these results with
the WL flats yields flat fields at all wavelengths. Some information on
scattered light and point spread functions are obtained from the August,
1999, eclipse observations and the Mercury transit. SSW routines for
dealing with some of these degradations will be identified. This work
is supported by the TRACE project at LMSAL (contract NAS5-38099).
Title: Observation of Shocks in the Chromosphere and Transition Region
Authors: Ryutova, M. P.; Tarbell, T. D.
Bibcode: 2000SPD....31.0141R
Altcode: 2000BAAS...32..808R
The spectra of CII and OVI lines corresponding to chromosphere and
transition region temperatures show significant broadening and complex
line profiles in regions overlying the sites of small scale magnetic
elements in the photopsheric network. Doppler shifted multiple peaks
in CII line are always seen soon after the reconnection of magnetic
flux tubes occurs and usually consist of supersonic and subsonic
components caused by shocks propagating upward. Multiple peaks in OVI
line have more diverse features: they are not as persistent as those
seen in CII line, and may have the configuration of maximum intensity
peaks corresponding either to forward or reflected shocks. We develop
a consistency analysis which allows to compare the shock relations
and their properties with the observed signatures and infer physical
parameters such as Mach number, direction of the shock propagation
and velocities. We use the uninterrupted time series of data to trace
particular events at the different stages of their evolution and deduce
some intrinsic features of the mechanism of the energy production and
its transport through the chromosphere/transition region.
Title: The STEREO-SECCHI Extreme Ultraviolet Imager
Authors: Wülser, J. -P.; Lemen, J. R.; Tarbell, T. D.; Wolfson,
C. J.; Howard, R. A.; Moses, J. D.; Delaboudinière, J. -P.
Bibcode: 2000SPD....31.0294W
Altcode:
The Extreme Ultraviolet Imager (EUVI) is part of the SECCHI
investigation selected for flight on the STEREO mission. The twin EUVI
telescopes on the two STEREO spacecraft will study the structure and
evolution of the solar corona in three dimensions, and specifically
focus on the initiation and early evolution of coronal mass ejections
(CMEs). The EUVI's 2048 x 2048 pixel detectors will have a full sun
field of view, and will observe in four spectral channels that cover
the 0.1 to 2 MK temperature range. The EUVI's major advance is its
view from two vantage points in space. It will allow it to investigate
the structure of CMEs in three dimensions, while the EUVI's high image
cadence capability will allow it to resolve the CME's initiation and
early evolution.
Title: The STEREO-SECCHI extreme ultraviolet imager.
Authors: Wülser, J. -P.; Lemen, J. R.; Tarbell, T. D.; Wolfson,
C. J.; Howard, R. A.; Moses, J. D.; Delaboudinière, J. -P.
Bibcode: 2000BAAS...32..827W
Altcode:
No abstract at ADS
Title: Diffraction Pattern Analysis of Bright TRACE Flares
Authors: Frank, Z. A.; Lin, A. C.; Nightingale, R. W.; Tarbell, T. D.
Bibcode: 2000SPD....31.0290F
Altcode: 2000BAAS...32..827F
A study of the diffraction patterns seen in TRACE images of bright
flares was undertaken to better understand the properties of the
telescope. The pattern caused by light from a bright solar flare passing
through the wire mesh in front of the telescope has been examined, and
a method has been developed to use this pattern to determine the zeroth
order intensity of bright flares. This intensity cannot usually be
measured directly due to saturation of the Analog to Digital Converter
(ADC) electronics in the CCD camera package. The validity of this
method has been tested on dimmer flares, whose intensity do not saturate
the ADC. The diffraction pattern allows us to measure intensities far
brighter than the camera package permits. For the bright flare on May
16, 1999 at 13:49:21 UT the range has been effectively increased by at
least 41 times. The light defracted away from any point was observed
to be 18%, a significant amount which affects the contrast of TRACE
images. An accurate determination of the ratio of the square slit
size to slit spacing of the wire mesh has been obtained. This is an
important parameter for a deconvolution routine that can remove the
diffraction patterns from the image (see adjacent SPD poster paper
by Tarbell et al.). Wavelength dispersion, the phenomenon that as the
higher order diffracted peaks lie further from the center they spread
out until double peaks are observed, has also been examined as part of
this study. This effect is observable because there are two principal
wavelengths, Fe IX at 171.06 Angstroms and Fe X at 174.52 Angstroms
in the TRACE 171 Angstroms passband used in present analysis. This
study is a part of the TRACE Team educational outreach program and is
supported by contract NAS5-38099 at LMSAL.
Title: TRACE Observations of Footpoints, Connections and Loops
Authors: Tarbell, T. D.
Bibcode: 2000SPD....31.1303T
Altcode: 2000BAAS...32..845T
The Transition Region and Coronal Explorer (a NASA Small Explorer
mission) was launched in April, 1998, and began observing in May. Since
launch, TRACE has performed nearly flawlessly and has collected over
two million images of the Sun. TRACE was designed to collect images
of all temperature domains of the solar atmosphere with high spatial
resolution and high cadence. Its movie sequences of the transition
region and corona have given us an unprecedented view of the dynamic
activity of magnetic fields above the solar surface. Using powerful
movie analysis software (the ANA browser), quantitative interactive
study of large datacubes is possible within hours of receipt of the raw
data. Since solar activity is increasing and since potential damage
to the CCD detector by over-exposure is better understood now, TRACE
devotes a large fraction of its observing time to flare watches. The
full-sun orbit, circular data buffers, and generous telemetry allow
TRACE to collect high cadence observations of preflare and flare
conditions. This talk will show examples of interesting and beautiful
TRACE observations of flares and less energetic coronal changes. The
footpoints of loops involved can sometimes be identified from transient
brightenings in the chromosphere and transition region. The inferred
connectivity is compared with photospheric magnetograms and with loops
seen in Fe IX/X 171 and Fe XII 195. This work is supported by the
TRACE project at LMSAL (contract NAS5-38099) and the SOI/MDI project
at Stanford and LMSAL (grant NAG5-3077).
Title: Electro-Mechanical Coupling Between the Photosphere and
Transition Region
Authors: Tarbell, T. D.; Ryutova, M.; Shine, R.
Bibcode: 2000SoPh..193..195T
Altcode:
We study the response of the chromosphere and transition region to
dynamic changes in the photospheric network magnetic fields. We present
results from simultaneous measurements taken by TRACE in chromospheric
and transition region (C iv) images, high-resolution magnetograms taken
by MDI, and spectra of chromospheric (C ii) and transition region
lines (O vi) obtained with the SUMER instrument on SOHO. Enhanced
emission in the C iv line is generally co-spatial with the magnetic
pattern in the photosphere. We propose a mechanism of electro-mechanical
coupling between the photosphere and upper layers of atmosphere based on
hydrodynamic cumulation of energy produced by reconnecting flux tubes in
the photosphere/chromosphere region (Tarbell et al., 1999). We believe
that a basic process causing energetic events is the cascade of shock
waves produced by colliding and reconnecting flux tubes. The continuous
supply of flux tubes in the `magnetic carpet' ensures the ubiquitous
nature of this process and its imprint on the upper atmosphere. The
appearance of bright transients often, but not always, correlates with
canceling mixed polarity magnetic elements in the photosphere. In
other cases, transients occur in regions of unipolar flux tubes,
suggesting reconnection of oblique components. Transients are also
seen in regions with no fields detected with the MDI sensitivity;
these may be reconnections of tiny features with diameters less than
100 km. Blinkers and other bright transients are often accompanied by
two directional plasma jets. These may be generated by cylindrical
self-focusing of shock fronts or by collision of shocks produced by
neighboring reconnection processes. The observations suggest that
stronger emissions correspond to lower velocity jets, and vice versa;
this property is a natural consequence of the proposed mechanism. Plasma
flows are always seen whenever the slit crosses strong magnetic flux
tubes or vertices of converging flows in the supergranular network. The
overall energy distribution between heating and plasma flows is an
intrinsic feature of our mechanism.
Title: Calibrated H I Lyman α Observations with TRACE
Authors: Handy, B. N.; Tarbell, T. D.; Wolfson, C. J.; Korendyke,
C. M.; Vourlidas, A.
Bibcode: 1999SoPh..190..351H
Altcode:
Since shortly after launch in April 1998, the Transition Region and
Coronal Explorer (TRACE) observatory has amassed a collection of H
i Lα (1216 Å) observations of the Sun that have been not only of
high spatial and temporal resolution, but also span a duration in
time never before achieved. The Lα images produced by TRACE are,
however, composed of not only the desired line emission, but also
local ultraviolet continuum and longer wavelength contamination. This
contamination has frustrated attempts to interpret TRACE observations
in H i Lα. The Very Advanced Ultraviolet Telescope (VAULT) sounding
rocket payload was launched from White Sands Missile range 7 May 1999
at 20:00 UT. The VAULT telescope for this flight was a dedicated H i
Lα imaging spectroheliograph. We use TRACE observations in the 1216
Å and 1600 Å channels along with observations from the VAULT flight
to develop a method for removing UV continuum and longer wavelength
contamination from TRACE Lα images.
Title: Simultaneous Observations of Chromospheric and Transition
Region Oscillations in HI Lyman Transitions and in Optical Lines
Authors: Curdt, W.; Heinzel, P.; Schmidt, W.; Tarbell, T.; von
Uexküll, M.; Wilken, V.
Bibcode: 1999ESASP.448..177C
Altcode: 1999mfsp.conf..177C; 1999ESPM....9..177C
No abstract at ADS
Title: What is Moss?
Authors: Berger, T. E.; De Pontieu, B.; Fletcher, L.; Schrijver,
C. J.; Tarbell, T. D.; Title, A. M.
Bibcode: 1999SoPh..190..409B
Altcode:
TRACE observations of active regions show a peculiar extreme ultraviolet
(EUV) emission over certain plage areas. Termed `moss' for its spongy,
low-lying, appearance, observations and modeling imply that the
phenomenon is caused by thermal conduction from 3-5 MKcoronal loops
overlying the plage: moss is the upper transition region emission of
hot coronal loops. The spongy appearance is due to the presence of
chromospheric jets or `spicules' interspersed with the EUV emission
elements. High cadence TRACE observations show that the moss EUV
elements interact with the chromospheric jets on 10 s time scales. The
location of EUV emission in the moss does not correlate well to the
locations of underlying magnetic elements in the chromosphere and
photosphere, implying a complex magnetic topology for coronal loop
footpoint regions. We summarize here the key observations leading to
these conclusions and discuss new implications for understanding the
structuring of the outer solar atmosphere.
Title: Characteristics of MHD Oscillations Observed with MDI
Authors: Norton, A. A.; Ulrich, R. K.; Bush, R. I.; Tarbell, T. D.
Bibcode: 1999ASPC..184..136N
Altcode:
We report on the spatial distribution of magnetic oscillatory power and
phase angles between velocity and magnetic signals as observed with the
Michelson Doppler Imager. The dataset is 151.25arcsec x 151.25arcsec
containing sunspot from Dec 2, 1997 with a temporal sampling interval
of 60 seconds and spatial sampling of 0.605arcsec. Simultaneously
observed continuum intensity and surface velocity accompany the magnetic
information. We focus on three frequency regimes: 0.5-1.0, 3.0-3.5 and
5.5-6.0 mHz corresponding roughly to timescales of magnetic evolution,
p-modes and the 3 minute resonant sunspot oscillation. Significant low
frequency magnetic power is found in lower flux pixels, 100-300 Gauss,
in a striking ring with filamentary structure surrounding sunspot. Five
minute oscillatory magnetic power peaks in extended regions of flux
600-800 Gauss. The 3 minute oscillation is observed in sunspot umbra
in pixels whose flux measures 1300-1500 Gauss. Phase angles of -90°
between velocity and magnetic flux in the 3.0-3.5 and 5.5-6.0 mHz
regimes suggest the MHD oscillations are magnetoacoustic in nature.
Title: A new view of the solar outer atmosphere by the Transition
Region and Coronal Explorer
Authors: Schrijver, C. J.; Title, A. M.; Berger, T. E.; Fletcher, L.;
Hurlburt, N. E.; Nightingale, R. W.; Shine, R. A.; Tarbell, T. D.;
Wolfson, J.; Golub, L.; Bookbinder, J. A.; DeLuca, E. E.; McMullen,
R. A.; Warren, H. P.; Kankelborg, C. C.; Handy, B. N.; De Pontieu, B.
Bibcode: 1999SoPh..187..261S
Altcode:
The Transition Region and Coronal Explorer (TRACE) - described in the
companion paper by Handy et al. (1999) - provides an unprecedented
view of the solar outer atmosphere. In this overview, we discuss the
initial impressions gained from, and interpretations of, the first
million images taken with TRACE. We address, among other topics,
the fine structure of the corona, the larger-scale thermal trends,
the evolution of the corona over quiet and active regions, the high
incidence of chromospheric material dynamically embedded in the coronal
environment, the dynamics and structure of the conductively dominated
transition region between chromosphere and corona, loop oscillations
and flows, and sunspot coronal loops. With TRACE we observe a corona
that is extremely dynamic and full of flows and wave phenomena, in
which loops evolve rapidly in temperature, with associated changes in
density. This dynamic nature points to a high degree of spatio-temporal
variability even under conditions that traditionally have been referred
to as quiescent. This variability requires that coronal heating can
turn on and off on a time scale of minutes or less along field-line
bundles with cross sections at or below the instrumental resolution
of 700 km. Loops seen at 171 Å (∼1 MK) appear to meander through
the coronal volume, but it is unclear whether this is caused by the
evolution of the field or by the weaving of the heating through the
coronal volume, shifting around for periods of up to a few tens of
minutes and lighting up subsequent field lines. We discuss evidence
that the heating occurs predominantly within the first 10 to 20 Mm
from the loop footpoints. This causes the inner parts of active-region
coronae to have a higher average temperature than the outer domains.
Title: The transition region and coronal explorer
Authors: Handy, B. N.; Acton, L. W.; Kankelborg, C. C.; Wolfson, C. J.;
Akin, D. J.; Bruner, M. E.; Caravalho, R.; Catura, R. C.; Chevalier,
R.; Duncan, D. W.; Edwards, C. G.; Feinstein, C. N.; Freeland, S. L.;
Friedlaender, F. M.; Hoffmann, C. H.; Hurlburt, N. E.; Jurcevich,
B. K.; Katz, N. L.; Kelly, G. A.; Lemen, J. R.; Levay, M.; Lindgren,
R. W.; Mathur, D. P.; Meyer, S. B.; Morrison, S. J.; Morrison, M. D.;
Nightingale, R. W.; Pope, T. P.; Rehse, R. A.; Schrijver, C. J.;
Shine, R. A.; Shing, L.; Strong, K. T.; Tarbell, T. D.; Title, A. M.;
Torgerson, D. D.; Golub, L.; Bookbinder, J. A.; Caldwell, D.; Cheimets,
P. N.; Davis, W. N.; Deluca, E. E.; McMullen, R. A.; Warren, H. P.;
Amato, D.; Fisher, R.; Maldonado, H.; Parkinson, C.
Bibcode: 1999SoPh..187..229H
Altcode:
The Transition Region and Coronal Explorer (TRACE) satellite, launched
2 April 1998, is a NASA Small Explorer (SMEX) that images the solar
photosphere, transition region and corona with unprecedented spatial
resolution and temporal continuity. To provide continuous coverage
of solar phenomena, TRACE is located in a sun-synchronous polar
orbit. The ∼700 Mbytes of data which are collected daily are made
available for unrestricted use within a few days of observation. The
instrument features a 30-cm Cassegrain telescope with a field of view
of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec
pixels). TRACE contains multilayer optics and a lumogen-coated CCD
detector to record three EUV wavelengths and several UV wavelengths. It
observes plasmas at selected temperatures from 6000 K to 10 MK with
a typical temporal resolution of less than 1 min.
Title: Magnetic energy avalanche as the source of the fast wind
Authors: Ryutova, M. P.; Habbal, S. R.; Woo, R.; Tarbell, T.
Bibcode: 1999AIPC..471..227R
Altcode: 1999sowi.conf..227R
We propose a mechanism for the formation of a magnetic energy avalanche
based on highly dynamic phenomena within the ubiquitous small scale
network magnetic elements in the quiet photosphere. We suggest that
this mechanism may provide constant mass and energy supply for the
origin of the fast wind.
Title: Characteristics of Magnetohydrodynamic Oscillations Observed
with the Michelson Doppler Imager
Authors: Norton, A. A.; Ulrich, R. K.; Bush, R. I.; Tarbell, T. D.
Bibcode: 1999ApJ...518L.123N
Altcode: 1999astro.ph..7256N
We report on the spatial distribution of the magnetogram oscillatory
power and the phase angles between velocity and magnetogram signals
as observed with the Michelson Doppler Imager. The data set is
151.25" × 151.25", containing the sunspot from 1997 December 2
with a temporal sampling interval of 60 s and spatial sampling of
0.605". The simultaneously observed continuum intensity and surface
velocity accompany the magnetic information. We focus on three frequency
regimes: 0.5-1.0, 3.0-3.5, and 5.5-6.0 mHz, corresponding roughly to
timescales of magnetic evolution, p-modes, and the 3 minute resonant
sunspot oscillation. Significant low-frequency magnetogram power
is found in lower flux pixels, 100-300 G, in a striking ring with
filamentary structure surrounding the sunspot. The 5 minute magnetogram
power peaks in extended regions of flux that measure 600-800 G. The
3 minute oscillation is observed in the sunspot umbra in pixels whose
flux measures 1300-1500 G. Phase angles of approximately -90° between
velocity and magnetic flux in the 3.0-3.5 and 5.5-6.0 mHz regimes are
found in regions of significant cross amplitude.
Title: Heating and jet formation by colliding shocks in solar
atmosphere
Authors: Tarbell, T.; Ryutova, M. P.; Covington, J.; Fludra, A.
Bibcode: 1999AIPC..471..419T
Altcode: 1999sowi.conf..419T
We show that ubiquitous small-scale magnetic flux ``tubes''
constantly emerging from subsurface layers, may cause the formation
of plasma jets and a sporadic excess of temperature near the solar
surface. Photospheric network magnetic elements collide and reconnect,
creating a sling-shot effect which generates complex 3D shock waves
with the curved surface. Self-focusing of these shocks occurs as they
propagate upward in the rarefied atmosphere. Depending on the geometry
of the shock collision, highly concentrated energy may be either
converted entirely into heat or into strong jets, or be distributed
between the two.
Title: A Transition Region Eruption Observed with CDS, TRACE and EIT
Authors: Brekke, P.; Kjeldseth-Moe, O.; Fredvik, T.; Haugan, S. V. H.;
Tarbell, T. D.; Gurman, J. B.
Bibcode: 1999AAS...194.5905B
Altcode: 1999BAAS...31..918B
An ejection of plasma on the west limb has been observed with CDS,
TRACE and EIT on 19 May 1998. The start of the eruption coincided
with a weak flare observed with GOES. Erupting material rose to 120
Mm above the solar surface in 17 min, and then fell back to the solar
surface. Vertical velocities of 200 km s(-1) are estimated from a series
of TRACE images in the C(+3) resonance lines at 155 nm and from EIT
images in the 19.5 nm band, while Doppler shifts of the transition
region lines observed with CDS yield maximum horizontal velocities
of 300 km s(-1) at the top of the plasma trajectories. The similar
appearance and time variation of the eruption as seen with all three
instruments indicate the presence of a multi-temperature plasma in
spatial regions less than 1-2 arc seconds, with temperatures ranging
from 10(5) K to 1.5 MK. The material did not have the momentum to break
loose from the Sun and was not associated with any CME observed with
LASCO. However, we may speculate that CMEs are similar to the eruption
observed, with even higher speeds involved.
Title: TRACE Images of the Solar Chromosphere, Transition Region,
and Low Corona at High Cadence and High Spatial Resolution
Authors: Tarbell, T. D.; Handy, B. N.; Judge, P. G.
Bibcode: 1999AAS...194.7801T
Altcode: 1999BAAS...31..960T
We present TRACE images and movies showing C IV emission (transition
region at 80,000 degrees) and UV continuum (temperature minimum
region) of quiet and active regions. TRACE images using the 1550,
1600, and 1700 Angstroms filters can be combined to estimate the total
emission in the C IV 1548 and 1550 lines and the UV continuum. These
are supplemented in different observations with MDI magnetograms, TRACE
171 Angstroms images (Fe IX/X and perhaps O VI), and SUMER spectra of
chromospheric and transition region lines from SOHO JOP 72. In quiet
sun, bright C IV transients are seen in the vicinity of flux emergence,
flux cancellation, and less dramatic interactions of small magnetic
structures. Some of these are accompanied by high-velocity explosive
events seen in SUMER spectra. The C IV emission can be well-separated
from the photospheric magnetic footpoints, suggesting that it takes
place on current sheets higher in the atmosphere separating different
flux systems. In active regions, both bright and dark fibrils or loops
are seen in C IV. Many nano/micro/sub flares are seen, some but not
all of which are associated with emerging flux. The C IV emission of
"moss" regions, footpoints of hot coronal loops, is contrasted with
that of similar plage which does not have hot loops above it. This work
was supported by the NASA contracts and grants for TRACE, MDI, and SOHO.
Title: The Solar-B Solar Optical Telescope Focal Plane Package
Authors: Levay, M.; Berger, T.; Rosenberg, W.; Tarbell, T.; Title,
A.; Bogdan, T.; Elmore, D.; Lites, B.
Bibcode: 1999AAS...194.7610L
Altcode: 1999BAAS...31R.957L
The primary goal of the Solar-B mission is to understand the physical
processes responsible for dynamics and heating of the outer solar
atmosphere. The Focal Plane Package (FPP) instrument for the 50-cm Solar
Optical Telescope provides precise measurements of the vector magnetic
field, vertical and horizontal flows, and thermal conditions in the
photosphere and low chromosphere with spatial resolution as high as
0.16 arcsec and a field-of-view as large as 320 x 160 arcsec. The FPP
can measure continuously and at high cadence to follow the evolution
of solar features. The FPP consists of broad ( 8 Angstroms) and narrow
( 100 m Angstroms) filters and a spectro-polarimeter that provides
precise polarimetry with high spectral resolution ( 25 m Angstroms). A
correlation tracker and tip-tilt mirror ensure that all focal planes
are stable to better than 0.01 arcsec. A major design consideration
of the FPP is cooperative science operations with the other Solar-B
instruments. Solar-B is a Japanese mission with US and UK partners;
S. Tsuneta is the PI of the Solar Optical Telescope and A. Title the
US PI of the FPP. It is scheduled to launch in Japanese FY 2004.
Title: A new view of the solar corona from the transition region
and coronal explorer (TRACE)
Authors: Golub, L.; Bookbinder, J.; Deluca, E.; Karovska, M.; Warren,
H.; Schrijver, C. J.; Shine, R.; Tarbell, T.; Title, A.; Wolfson,
J.; Handy, B.; Kankelborg, C.
Bibcode: 1999PhPl....6.2205G
Altcode:
The TRACE Observatory is the first solar-observing satellite in the
National Aeronautics and Space Administration's (NASA) Small Explorer
series. Launched April 2, 1998, it is providing views of the solar
transition region and low corona with unprecedented spatial and
temporal resolution. The corona is now seen to be highly filamented,
and filled with flows and other dynamic processes. Structure is seen
down to the resolution limit of the instrument, while variability and
motions are observed at all spatial locations in the solar atmosphere,
and on very short time scales. Flares and shock waves are observed,
and the formation of long-lived coronal structures, with consequent
implications for coronal heating models, has been seen. This overview
describes the instrument and presents some preliminary results from
the first six months of operation.
Title: Observational Constraints on Models of the Solar Background
Spectrum
Authors: Straus, Th.; Severino, G.; Deubner, F. -L.; Fleck, B.;
Jefferies, S. M.; Tarbell, T.
Bibcode: 1999ApJ...516..939S
Altcode:
We discuss the properties of the solar background signal as observed in
high-quality, l-ν power and phase difference spectra of the continuum
(C), velocity (V), and line intensity (I) fluctuations of the Ni
I 6768 Å line. These spectra were generated from high-resolution
images acquired by the Michelson Doppler Imager on board SOHO. We
confirm that the background signal in the velocity power spectra can be
reproduced by a composite model with two quasi-stationary components,
describing large-scale and small-scale convective motions, and a
periodic component. The line and continuum intensity power spectra
require additional quasi-stationary and periodic components. The
extra quasi-stationary component dominates the intensity and
continuum background signals over the spectral region where the I-V
phase difference spectra show essentially constant negative phase
difference: i.e., below and in between the p-mode ridges (called the
plateau-interridge regime by Deubner et al.). Since the I-V phase
between the p-mode ridges is not random, the solar background beneath
the p-modes must be considered as coherent. We thus speculate that
the negative phase regime may be the manifestation of a correlated
background. Such a background has been proposed to explain the opposite
sense of the asymmetries of the p-mode line profiles in velocity and
brightness oscillations.
Title: Plasma Streaming and Explosive Events in the Solar Transition
Region: Theory and Observations
Authors: Ryutova, M.; Tarbell, T.
Bibcode: 1999AAS...194.7803R
Altcode: 1999BAAS...31..961R
As shown by Tarbell et al. (ApJ, 514, L47, 1999 ) a sporadic excess of
temperature and wide variety of plasma jets observed in the chromosphere
and transition region overlying quiet sun regions may be explained by
hydrodynamic cumulation resulted from the acoustic shocks generated by
the reconnecting small scale network magnetic elements in the solar
photosphere. Here we study magneto-hydrodynamic cumulation resulted
from post-reconnection MHD shocks generated in complex magnetic field
geometries typical to upper chromosphere and low corona. We present
the results for the observed regularities obtained from simultaneous
measurements taken by TRACE in chromospheric, transition region and
coronal images and MDI on SOHO showing time series of high resolution
magnetograms. We find that (1) All the essential features of the
hydrodynamic cumulation remain in place: the MHD shocks driven by the
post-reconnection sling-shot effect and self-focusing of these shocks
lead to several well observed signatures of the energy release. (2) The
evolution of generated flows depends on the geometry of intermittent
magnetic fields and the height of jet formation. In regions of open
magnetic structures plasma flows have tendency to accelerate and reach
supersonic and super-Alfvenic velocities. Due to linear KH instability
such flows may generate high frequency Alfven waves propagating along
the magnetic structures. (3) In those regions where cumulative effects
result in the predominant heating which is accompanied by generation of
"moderate" (sub-Alfvenic) velocity jets, there are conditions when high
velocity explosive events are driven. Our theoretical model shows that
the explosive events proceeded by appearance of the bright transients
are caused by the development of shear flow dissipative (nonlinear)
instabilities. We also suggest that "non-bright"explosive events may
be driven by rare effect of the cylindrical focusing of the MHD shocks
(the Guderley's effect).
Title: Observations of Filaments
Authors: Title, A.; Schrijver, C.; Tarbell, T.; Shine, R.
Bibcode: 1999AAS...194.7905T
Altcode: 1999BAAS...31..963T
Filaments are clearly seen as absorption features in the TRACE FE
IX and XII images. Because of the 24 hour coverage of TRACE many
filaments have been observed on the disk and near the limb, and as
quiescent and active structures. A quiescent filament consists of many
parallel strands the run nearly parallel to the surface. The strands
are often at the TRACE resolution and are always in motion. Adjacent
strands often exhibit flows in opposite directions with speeds of
10 to 40 km/second. Filaments occasionally erupt explosive from the
surface. The initial accelerations have not been observed with a 30
second cadence. Velocities in the initial phase range between 200
and 400 km/s. Filaments are observed to erupt and travel out of the
TRACE field of view, erupt and fall back to the solar surface, and
erupt and travel a short distance before being constraint by overlying
fields. Examples of the dynamic structure of filaments and their modes
of eruption will be demonstrated in a video presentation.
Title: Heating and Jet Formation by Hydrodynamic Cumulation in the
Solar Atmosphere
Authors: Tarbell, T.; Ryutova, M.; Covington, J.; Fludra, A.
Bibcode: 1999ApJ...514L..47T
Altcode:
The solar transition region is the site of supersonic plasma jets and
sporadic radiative events, whose origin and physical nature have not
been understood. Here we show that ubiquitous small-scale magnetic flux
``tubes,'' constantly emerging from subsurface layers, may cause the
formation of plasma jets and a sporadic excess of temperature near
the solar surface. These flux tubes collide and reconnect, creating
a sling-shot effect that generates complex three-dimensional shock
waves with the curved surface. Self-focusing of these shocks occurs
as they propagate upward in the rarefied atmosphere. Depending on the
geometry of the shock collision, highly concentrated energy may be
converted entirely into either heat or strong jets, or distributed
between the two.
Title: An eruption in the transition region observed with CDS and
TRACE, on May 19, 1998.
Authors: Brekke, P.; Kjeldseth-Moe, O.; Tarbell, T.
Bibcode: 1999joso.proc..170B
Altcode:
The authors present simultaneous CDS and TRACE observations in the EUV
of an eruption of May 19, 1998. A large ejection of plasma was seen
on the west limb and could be followed in EUV rasters in transition
region lines with CDS and in high cadence images in the C+3
155 nm line from TRACE. The onset of the eruption coincided with a
weak flare observed with GOES. The eruption extended to 120000 km
above the solar surface after 17 min and then fell back to the solar
surface. At the leading edge of the eruption CDS observed Doppler
shifts of 300 km s-1 away from the observer (i.e. parallel
to the solar surface) in the O+4 line at 62.9 nm. High
cadence observations with TRACE indicate that the plasma velocities
perpendicular to the line of sight (i.e. along the solar vertical)
reached similar values, i.e. 200 km s-1. Perhaps this was a
"coronal mass ejection" that did not make it?
Title: Jets and Eruptions in the Transition Region Observed with CDS,
EIT and TRACE
Authors: Brekke, P.; Kjeldseth-Moe, O.; Tarbell, T.; Gurman, J.
Bibcode: 1999ASPC..183..357B
Altcode: 1999hrsp.conf..357B
No abstract at ADS
Title: The Transition Region and Coronal Explorer
Authors: Handy, B. N.; Deluca, E. E.; McMullen, R. A.; Schrijver,
C. J.; Tarbell, T. D.; Title, A. M.; Wolfson, C. J.
Bibcode: 1998AAS...193.1207H
Altcode: 1998BAAS...30R1269H
The Transition Region and Coronal Explorer (TRACE), launched 1 April
1998, will have at the time of this meeting been in orbit for just over
8 months. In that time, the instrument will have taken over 500,000
exposures of the sun in ultraviolet and extreme ultraviolet wavelengths,
will have completed three-forths of the nominal mission and will be
approaching the end of the first eclipse season. The TRACE telescope
is unique in its ability to observe in UV and EUV wavelengths at high
cadence with unprecedented resolution. We present a review of the TRACE
instrument and show current observations and results. We discuss the
performance of the instrument in terms of observational capabilities,
sensitivity, calibration, effects of aging on the instrument, CCD
effects, and contamination effects.
Title: The TRACE Mission: Initial Scientific Results
Authors: Title, A. M.; Tarbell, T. D.; Wolfson, J.; Schrijver, K.;
Fisher, R. R.; Gang, Th.; Golub, L.; McMullen, R. A.; Kankelborg,
C.; TRACE Collaboration
Bibcode: 1998AAS...19310008T
Altcode: 1998BAAS...30R1398T
TRACE (Transition Region and Coronal Explorer) is a Small Explorer
Mission (SMEX) devoted to studying the evolution and propagation
of fine-scale magnetic fields and plasma structures throughout the
solar atmosphere. The instrument consists of a telescope with a 30 cm
primary mirror, normal incidence coatings for three EUV bands (171,
195 and 284 Angstroms), and interference filters for UV bands (1216
to 1700 Angstroms) as well as white light (allowing the selection of
temperature ranges from ~ 6 000 to ~ 2 500 000 degrees K). The 1024
x 1024 CCD camera has a field of view of 8.5 arcmin with a spatial
resolution of 1 arcsec and exposure times of 0.002 to 260 sec with
a cadence as short as two seconds. The spacecraft was launched on
April 1, 1998, and first light for the telescope occurred on April
20. Observations have been collected nearly 24 hours per day since
then, with no significant problems in any segment of the spacecraft,
instrument, or mission operations. TRACE transmits about 3--4 GB of
data per week which gets automatically reformatted and becomes available
for the scientific community within approx. 24 hours. It is accessible
without restrictions (only guidelines) together with other informations
(technical details, educational material, movies, images,...) at:
http://vestige.lmsal.com/TRACE. The images reveal activity in the
solar atmosphere in stunning detail and include the first detailed
observations of a magnetic energy release. This magnetic reconnection
was observed on May 8, 1998, in a region of the solar atmosphere where
two sets of perpendicular magnetic loops expanded into each other (see
NASA Press Release 98-92). The TRACE mission has been developed and
operated by NASA's Goddard Space Flight Center, Lockheed Martin Solar
& Astrophysics Laboratory, Smithsonian Astrophysical Observatory,
and Montana State University.
Title: Spatiotemporal Correlations and Turbulent Photospheric Flows
from SOHO/MDI Velocity Data
Authors: Cadavid, A. C.; Lawrence, J. K.; Ruzmaikin, A. A.; Walton,
S. R.; Tarbell, T.
Bibcode: 1998ApJ...509..918C
Altcode:
Time series of high-resolution and full-disk velocity images obtained
with the Michelson Doppler Imager (MDI) instrument on board SOHO
have been used to calculate the spacetime spectrum of photospheric
velocity flow. The effects of different methods for filtering acoustic
oscillations have been carefully studied. It is found that the spectra
show contributions both from organized structures that have their origin
in the convection zone and from the turbulent flow. By considering
time series of different duration and cadence in solar regions with
different line-of-sight projections, it is possible to distinguish the
contributions of the spectra from the two different kinds of flows. The
spectra associated with the turbulent velocity fields obey power laws
characterized by two scaling parameters whose values can be used to
describe the type of diffusion. The first parameter is the spectral
exponent of the spatial correlation function and the second is a
scaling parameter of the time correlation function. Inclusion of the
time parameter is an essential difference between the present work
and other solar studies. Within the confidence limits of the data,
the values of the two parameters indicate that the turbulent part of
the flow in the scale range 16-120 Mm produces superdiffusive transport.
Title: Efficiency loss of lumogen-coated CCDs by exposure to
ultraviolet and extreme ultraviolet photons
Authors: Catura, Richard C.; Duncan, Dexter W.; Shing, Lawrence;
Tarbell, Theodore D.; Wolfson, C. Jacob
Bibcode: 1998SPIE.3445..291C
Altcode:
The efficiency of lumogen coated CCDs has been measured as a function of
wavelength in the range from 171 angstrom to 1800 angstrom. A decrease
in efficiency has been observe as a function of exposure of the lumogen
to high levels of radiation at UV and extreme UV wavelengths. The drop
in efficiency was found to be most rapid at lower exposure levels,
decreasing in rate as the dosage increased.
Title: UV Observations with the Transition Region and Coronal Explorer
Authors: Handy, B. N.; Bruner, M. E.; Tarbell, T. D.; Title, A. M.;
Wolfson, C. J.; Laforge, M. J.; Oliver, J. J.
Bibcode: 1998SoPh..183...29H
Altcode:
The Transition Region and Coronal Explorer is a space-borne solar
telescope featuring high spatial and temporal resolution. TRACE
images emission from solar plasmas in three extreme-ultraviolet (EUV)
wavelengths and several ultraviolet (UV) wavelengths, covering selected
ion temperatures from 6000 K to 1 MK. The TRACE UV channel employs
special optics to collect high-resolution solar images of the H i
Lα line at 1216 Å, the C iv resonance doublet at 1548 and 1550 Å,
the UV continuum near 1550 Å, and also a white-light image covering
the spectrum from 2000-8000 Å.
Title: Helioseismic Studies of Differential Rotation in the Solar
Envelope by the Solar Oscillations Investigation Using the Michelson
Doppler Imager
Authors: Schou, J.; Antia, H. M.; Basu, S.; Bogart, R. S.; Bush,
R. I.; Chitre, S. M.; Christensen-Dalsgaard, J.; Di Mauro, M. P.;
Dziembowski, W. A.; Eff-Darwich, A.; Gough, D. O.; Haber, D. A.;
Hoeksema, J. T.; Howe, R.; Korzennik, S. G.; Kosovichev, A. G.;
Larsen, R. M.; Pijpers, F. P.; Scherrer, P. H.; Sekii, T.; Tarbell,
T. D.; Title, A. M.; Thompson, M. J.; Toomre, J.
Bibcode: 1998ApJ...505..390S
Altcode:
The splitting of the frequencies of the global resonant acoustic modes
of the Sun by large-scale flows and rotation permits study of the
variation of angular velocity Ω with both radius and latitude within
the turbulent convection zone and the deeper radiative interior. The
nearly uninterrupted Doppler imaging observations, provided by the
Solar Oscillations Investigation (SOI) using the Michelson Doppler
Imager (MDI) on the Solar and Heliospheric Observatory (SOHO) spacecraft
positioned at the L1 Lagrangian point in continuous sunlight,
yield oscillation power spectra with very high signal-to-noise ratios
that allow frequency splittings to be determined with exceptional
accuracy. This paper reports on joint helioseismic analyses of
solar rotation in the convection zone and in the outer part of the
radiative core. Inversions have been obtained for a medium-l mode set
(involving modes of angular degree l extending to about 250) obtained
from the first 144 day interval of SOI-MDI observations in 1996. Drawing
inferences about the solar internal rotation from the splitting data
is a subtle process. By applying more than one inversion technique
to the data, we get some indication of what are the more robust
and less robust features of our inversion solutions. Here we have
used seven different inversion methods. To test the reliability and
sensitivity of these methods, we have performed a set of controlled
experiments utilizing artificial data. This gives us some confidence
in the inferences we can draw from the real solar data. The inversions
of SOI-MDI data have confirmed that the decrease of Ω with latitude
seen at the surface extends with little radial variation through much
of the convection zone, at the base of which is an adjustment layer,
called the tachocline, leading to nearly uniform rotation deeper
in the radiative interior. A prominent rotational shearing layer in
which Ω increases just below the surface is discernible at low to
mid latitudes. Using the new data, we have also been able to study the
solar rotation closer to the poles than has been achieved in previous
investigations. The data have revealed that the angular velocity
is distinctly lower at high latitudes than the values previously
extrapolated from measurements at lower latitudes based on surface
Doppler observations and helioseismology. Furthermore, we have found
some evidence near latitudes of 75° of a submerged polar jet which
is rotating more rapidly than its immediate surroundings. Superposed
on the relatively smooth latitudinal variation in Ω are alternating
zonal bands of slightly faster and slower rotation, each extending
some 10° to 15° in latitude. These relatively weak banded flows
have been followed by inversion to a depth of about 5% of the solar
radius and appear to coincide with the evolving pattern of ``torsional
oscillations'' reported from earlier surface Doppler studies.
Title: Oscillations of sunspot magnetic fields
Authors: Rueedi, I.; Solanki, S. K.; Stenflo, J. O.; Tarbell, T.;
Scherrer, P. H.
Bibcode: 1998A&A...335L..97R
Altcode:
We report on velocity and magnetic field oscillations observed
in sunspots using the MDI instrument onboard SOHO. In addition to
the well-known velocity oscillations, the data clearly show highly
localised oscillations of the magnetogram signal in different parts
of the sunspots. We show that only oscillations of the magnetic field
vector can produce the observed magnetogram oscillations, and that the
observed phase relations suggest an origin in terms of magnetoacoustic
gravity waves.
Title: Large-scale coronal heating by the small-scale magnetic field
of the Sun
Authors: Schrijver, C. J.; Title, A. M.; Harvey, K. L.; Sheeley,
N. R.; Wang, Y. -M.; van den Oord, G. H. J.; Shine, R. A.; Tarbell,
T. D.; Hurlburt, N. E.
Bibcode: 1998Natur.394..152S
Altcode:
Magnetic fields play a crucial role in heating the outer atmospheres
of the Sun and Sun-like stars, but the mechanisms by which magnetic
energy in the photosphere is converted to thermal energy in the corona
remain unclear. Observations show that magnetic fields emerge onto
the solar surface as bipolar regions with a broad range of length
scales. On large scales, the bipolar regions survive for months before
dispersing diffusively. On the smaller scales, individual bipolar
regions disappear within days but are continuously replenished by new
small flux concentrations, resulting in a sustained state of mixed
polarity. Here we determine the rate of emergence of these small
bipolar regions and we argue that the frequent magnetic reconnections
associated with these regions (an unavoidable consequence of continued
flux replacement) will heat the solar atmosphere. The model that
describes the details of these mixed-polarity regions is complementary
to the traditional diffusion model for large-scale flux dispersal and
a combination of the two should lead to a more complete understanding
of the role of magnetic fields in stellar atmospheres.
Title: First Results from the TRACE Mission
Authors: Title, A.; Tarbell, T.; Schrijver, C.; Wolfson, J.; Shine,
R.; Hurlburt, N.; Golub, L.; Deluca, E.; Bookbinder, J.; Handy, B.;
Acton, L.; Harrison, R.; Delaboudinere, J. -P.
Bibcode: 1998AAS...192.1507T
Altcode: 1998BAAS...30..841T
The TRACE spacecraft was launched on 1 April and all systems are
functioning as designed. The initial outgassing period will conclude
on 20 April and the science program will then begin. TRACE is a UV-EUV
imager with one arc second spatial resolution and is capable of taking
images with a cadence as high as two seconds. We will present images
and image sequences. We hope to present initial comparisons of magnetic
evolution and transition region and coronal brightenings.
Title: The Postflare Loops and the Nearby Active Chromosphere of
1992 June 26: Addendum
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
Bibcode: 1998ApJ...495..502M
Altcode:
Video segments are presented that were processed from a quantitative
study of the dynamics of the evolution of Hα postflare loops developed
after a large solar flare. The high spatial resolution of the Swedish
Vacuum Solar Telescope (SVST) at La Palma provided a unique set of
data for such an event.
Title: Helio-Atmospheric Links Explorer (HALE): A MIDEX Experiment
for Exploring the Emergence of Magnetic Flux from Below the Solar
Photosphere through the Corona
Authors: Scherrer, P. H.; Title, A. M.; Bush, R. I.; Duvall, T. L.,
Jr.; Gurman, J. B.; Kosovichev, J. T.; Hoeksema, A. G.; Poland, A. I.;
Tarbell, T. D.
Bibcode: 1998ESASP.417..285S
Altcode: 1998cesh.conf..285S
No abstract at ADS
Title: The Stellar and Planetary Explorer (SPEX) Mission
Authors: Schou, J.; Scherrer, P. H.; Brown, T. M.; Frandsen, S.;
Horner, S. D.; Korzennik, S. G.; Noyes, R. W.; Tarbell, T. D.; Title,
A. M.; Walker, A. B. C., II; Weiss, W. W.; Bogart, R. S.; Bush, R. I.;
Christensen-Dalsgaard, J.; Hoeksema, J. T.; Jones, A.; Kjeldsen, H.
Bibcode: 1998ESASP.418..401S
Altcode: 1998soho....6..401S
The Stellar and Planetary Explorer (SPEX) is a mission designed
to search for terrestrial sized planets around sun-like stars using
precise photometry. The planets will be detected by searching for the
decrease in brightness associated with transits of the planets in front
of their parent stars. One of the secondary scientific objective of
SPEX is to do asteroseismology on a number of sun-like stars. SPEX
is designed as a secondary payload on a commercial communications
satellite and will have a design life time of three years. We will
provide an overview of the SPEX scientific objectives and design,
with particular emphasis on the prospects for doing asteroseismology.
Title: Phase spectra seen from space
Authors: Straus, Th.; Deubner, F. -L.; Fleck, B.; Marmolino, C.;
Severino, G.; Tarbell, T.
Bibcode: 1998IAUS..185..455S
Altcode:
We discuss preliminary results of a study of the dynamics of the solar
atmosphere including a first space based investigation of k-omega phase
difference spectra between velocity and intensity perturbations. The
data, including simultaneous line shift, line depth, and continuum
intensity measurements at disk center, have been obtained from a MDI
time series in its high resolution mode. Line depth and continuum
intensity are used to calculate the line intensity which is the more
frequently used parameter in phase difference studies. We compare the
results to ground based observations.
Title: Calibration and Stability of MDI Velocities
Authors: Beck, J. G.; Scherrer, P. H.; Bush, R. I.; Tarbell, T. D.
Bibcode: 1998ESASP.418..105B
Altcode: 1998soho....6..105B
No abstract at ADS
Title: A Modification to the Calibration of MDI Velocities
Authors: Evans, S.; Ulrich, R. K.; Scherrer, P. H.; Bush, R. I.;
Tarbell, T. D.
Bibcode: 1998ESASP.418..157E
Altcode: 1998soho....6..157E
The ability of the Michelson Doppler Imager instrument used by the
Solar Oscillations Investigation (Scherrer, et al, 1995) to produce
velocity measurements is affected by center-to-limb effects on the Ni
6768 AA line profile. These effects are removed by special calibration
observations known as detunes. Part of the detune procedure involves the
modelling of center-to-limb line profile changes by fitting a Gaussian
to the line profile and varying both the model profile's depth and
FWHM as a function of center-to-limb angle. However, the functions
used for modelling both line depth and FWHM differ from those derived
from data from both the Mt. Wilson 150' Tower and the Fourier Transform
Spectrometer at Kitt Peak. This variation can produce velocity errors
of ~100 m/s. By modifying the line depth and FWHM functions to conform
to those derived from the data, an improved velocity calibration can
be achieved.
Title: K-ϖ Phase Spectra Obtained from Space
Authors: Straus, Th.; Fleck, B.; Severino, G.; Deubner, F. -L.;
Marmolino, C.; Tarbell, T.
Bibcode: 1998ESASP.417..293S
Altcode: 1998cesh.conf..293S
No abstract at ADS
Title: Rotation and Zonal Flows in the Solar Envelope from the
SOHO/MDI Observations
Authors: Scherrer, P. H.; Schou, J.; Bogart, R. S.; Bush, R. I.;
Hoeksema, J. T.; Kosovichev, A. G.; Antia, H. M.; Chitre, S. M.;
Christensen-Dalsgaard, J.; Larsen, R. M.; Pijpers, F. P.; Eff-Darwich,
A.; Korzennik, S. G.; Gough, D. O.; Sekii, T.; Howe, R.; Tarbell,
T.; Title, A. M.; Thompson, M. J.; Toomre, J.
Bibcode: 1997AAS...191.7310S
Altcode: 1997BAAS...29.1322S
We report on the latest inferences concerning solar differential
rotation that have been drawn from the helioseismic data that are now
available from the Solar Oscillations Investigation (SOI) using the
Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory
(SOHO). That spacecraft is positioned in a halo orbit near the Sun-Earth
Lagrangian point L_1, in order to obtain continuous Doppler-imaged
observations of the sun with high spatial fidelity. Doppler velocity,
intensity and magnetic field images are recorded, based on modulations
of the 676.8 nm Ni I solar absorption line. The high spatial resolution
of MDI thereby permits the study of many millions of global resonant
modes of solar oscillation. Determination and subsequent inversion
of the frequencies of these modes, including the degeneracy-splitting
by the rotation of the sun, enables us to infer how the sun's angular
velocity varies throughout much of the interior. The current MDI data
are providing substantial refinements to the helioseismic deductions
that can be made about differential rotation both within the convection
zone and in its transition to the radiative interior. The shearing
layer evident in the angular velocity Omega just below the solar
surface is becoming better defined, as is the adjustment layer or
tachocline near the base of the convection zone. The MDI data are also
revealing a prominent decrease in Omega at high latitudes from the
rotation rate expressed by a simple three-term expansion in latitude
that was originally deduced from surface Doppler measurements. Further,
there are indications that a submerged polar vortex involving somewhat
faster Omega than its surroundings exists at about 75(deg) in latitudes.
Title: Photospheric flows as measured by SOI/MDI
Authors: Hurlburt, N.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.;
Simon, G.
Bibcode: 1997ASSL..225..285H
Altcode: 1997scor.proc..285H
On 2 February and 7 March 1996, MDI on the SOHO spacecraft ran several
hours to provide high resolution continuum images to map the horizontal
flows near the equator and pole by correlation tracking. Here we present
preliminary results on the performance of the tracking technique
in measuring the differential rotation profile. These preliminary
results are compared with each other and with corresponding results
of previous studies.
Title: 3-D Magnetic Field Configuration Late in a Large Two-Ribbon
Flare
Authors: Moore, R. L.; Schmieder, B.; Hathaway, D. H.; Tarbell, T. D.
Bibcode: 1997SoPh..176..153M
Altcode:
We present Hα and coronal X-ray images of the large two-ribbon flare
of 25-26 June, 1992 during its long-lasting gradual decay phase. From
these observations we deduce that the 3-D magnetic field configuration
late in this flare was similar to that at and before the onset of
such large eruptive bipolar flares: the sheared core field running
under and out of the flare arcade was S-shaped, and at least one
elbow of the S looped into the low corona. From previous observations
of filament-eruption flares, we infer that such core-field coronal
elbows, though rarely observed, are probably a common feature of the
3-D magnetic field configuration late in large two-ribbon flares. The
rare circumstance that apparently resulted in a coronal elbow of the
core field being visible in Hα in our flare was the occurrence of a
series of subflares low in the core field under the late-phase arcade
of the large flare; these subflares probably produced flaring arches
in the northern coronal elbow, thereby rendering this elbow visible
in Hα. The observed late-phase 3-D field configuration presented
here, together with the recent sheared-core bipolar magnetic field
model of Antiochos, Dahlburg, and Klimchuk (1994) and recent Yohkoh
SXT observations of the coronal magnetic field configuration at
and before the onset of large eruptive bipolar flares, supports the
seminal 3-D model for eruptive two-ribbon flares proposed by Hirayama
(1974), with three modifications: (1) the preflare magnetic field is
closed over the filament-holding core field; (2) the preflare core
field has the shape of an S (or backward S) with coronal elbows; (3)
a lower part of the core field does not erupt and open, but remains
closed throughout flare, and can have prominent coronal elbows. In
this picture, the rest of the core field, the upper part, does erupt
and open along with the preflare arcade envelope field in which it
rides; the flare arcade is formed by reconnection that begins in the
middle of the core field at the start of the eruption and progresses
from reconnecting closed core field early in the flare to reconnecting
`opened' envelope field late in the flare.
Title: Post-Flare Loops of 26 June 1992 - IV. Formation and Expansion
of Hot and Cool Loops
Authors: Van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.; Tarbell,
T.; Kitai, R.; Funakoshi, Y.; Anwar, B.
Bibcode: 1997SoPh..174..151V
Altcode:
Observations of the post-flare loops after the X3.9 flare which occurred
on 25 June, 1992 at 20:11 UT by the Yohkoh/SXT in X-rays, as well as
in Hα obtained at 5 different observatories, have provided a unique,
longest ever, set of data for a study of the relationship between the
hot and cool post-flare loops as they evolve. At any given time, the
altitude difference between the hot X-ray loops of 6-7× 106
K and the cool Hα loops of 1.5× 104 K is related to the
expansion rate of the loop systems and their cooling time. Therefore,
measurements of the expansion rate and relative height of hot and
cool loops can provide direct observational values for their cooling
times. We measured the altitude of hot and cool loops for 15 and 19
hours, respectively, and found that the cooling time increased as the
density of the loops decreased. We found a reasonably good agreement
between the observed cooling times and those obtained from model
calculations, although the observed values were always somewhat longer
than the theoretical ones. Taking into account evolutionary effects,
we also found similar shapes and configurations of hot and cool loops
during the entire observing period and confirmed that, at any time,
hot loops are at higher altitude than cool loops, suggesting that cool
loops indeed evolve from hot loops. These results were used to check
the validity of the reconnection model.
Title: Properties of the Smallest Solar Magnetic
Elements. II. Observations versus Hot Wall Models of Faculae
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1997ApJ...484..479T
Altcode:
Observations obtained at the Swedish Solar Observatory, La Palma,
using the Lockheed tunable filter, have been used to measure
properties of active region faculae, including contrast from disk
center to near the limb. The data consist of coregistered digital
photometric images of the line-of-sight magnetic field and of the
continuum intensity. The results are related to the structure
of the individual flux tubes comprising faculae in active regions. In
addition to center-limb contrast, the observations reveal a change in
contrast between heliocentric angles of about 45° and 60° related
to the ``turn-on'' of bright faculae. A class of models has been
constructed that describes a facula as an evacuated thin flux tube
with a hot wall and a depressed cool floor (hot wall model). The
hot wall model is very successful in predicting the observations,
including the changes observed between 45° and 60°. The model
predicts that the larger flux tubes comprising active region plage are
micropores with a Wilson depression of 100 km largely independent of
micropore diameter. Their typical diameter is 350-650 km; the largest
ones are about 1200 km across. Bright points are the major component of
active region plages by number, but micropores probably are the major
component by total magnetic flux. Bright active region faculae seen
near the limb are simply micropores viewed from the side, where the hot
wall is visible and the depressed cool floor is not. The temperature
difference between cool floor and hot wall varies from 300 to nearly
500 K, depending on tube diameter and heliocentric angle. These
results have important implications for solar irradiance variations.
Title: The Postflare Loops and the Nearby Active Chromosphere of
1992 June 26
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
Bibcode: 1997ApJ...482..535M
Altcode:
The main objective of this paper is to present a quantitative study
of the dynamics of the evolution of Hα postflare loops developed
after a large solar flare and the processed videos produced from the
observations. The high spatial resolution of the Swedish Vacuum Solar
Telescope (SVST) at La Palma has provided a unique set of data for such
an event. A Gaussian fitting method is proposed to derive intensities
and Doppler shifts from observations taken at three wavelengths (Hα
center and Hα +/- 0.07 nm). Moving condensations or ``blobs'' of cold
material provide transverse velocities, which, together with the radial
component, enable us to derive their velocity vector magnitude. Plasma
velocities are around free-fall velocities near the top of the loops
but are significantly smaller close to their footpoints, suggesting
a deceleration mechanism. The loops are anchored in the chromosphere,
which shows tremendous activity in the active region and in the nearby
``quiet Sun.'' Spicules and ejection of plasmoids are also observed
at the limb.
Title: On the Dynamics of Magnetic Flux Concentrations in Quiet
Photospheric Network.
Authors: Sakai, J. I.; Ryutova, M.; Schrijver, K.; Shine, R.; Tarbell,
T.; Berger, T.; Title, A.; Hagenaar, H.
Bibcode: 1997SPD....28.0260S
Altcode: 1997BAAS...29..904S
Magnetic flux concentrations in the quiet photospheric network show
a complex dynamics which includes merging of colliding fluxes, the
"total" or partial cancellation of neighboring fluxes, fragmentation
and others. We propose a mechanism to explain the observed phenomena
based on the idea that magnetic flux concentrations in the photospheric
network are essentially non-collinear. We show that non-collinearity
of colliding fluxes leads to the whole new class of effects which are
observed; for example, the apparent cancellation of opposite polarity
fluxes turns into the formation of horizontal magnetic fluxes (which
later may appear as a new weaker bipoles) and is accompanied by the
shock formation and mini-flares. In the case of shock formation
the reconnection area becomes a source of the acoustic emission;
mini-flares may be seen as bright points. The energetics of these
processes strongly depends on geometry of "collision" and physical
parameters of colliding fluxes. For example, if colliding fluxes have
comparable and "small" cross sections, the reconnection results in
complete reorganization of their magnetic fields; if merging fluxes
are large enough or considerably different, magnetic flux may be
only partially reconnected and partially survived. Reconnection of
non-collinear equal polarity fluxes leads to the "scattering" processes
which include the fragmentation into several smaller fluxes if initially
colliding concentrations carried different amount of magnetic flux. We
give the example of numerical simulation for the case of merging and
fragmentation process occurring during the collision of collinear
"strong" and "weak" magnetic flux concentrations. The calculation
results shown to be consistent with observational data from both
the SOHO/MDI instrument and the Swedish Vacuum Solar Telescope on
La Palma. This research is supported by NASA contract NAG5-3077 at
Stanford University and the MDI contract PR 9162 at Lockheed.
Title: Photospheric Differential Rotation from Full-Disk SOI/MDI
Dopplergrams
Authors: Bogart, R. S.; Bai, T.; Scherrer, P. H.; Strous, L. H.;
Simon, G. W.; Tarbell, T. D.
Bibcode: 1997SPD....28.0258B
Altcode: 1997BAAS...29..903B
We report on measurements of the solar surface differential rotation
made from SOI/MDI full-disk Dopplergrams obtained once per minute during
the 2-month Dynamics Program from 23 May through 26 July 1996. We infer
the rotation profile both from the direct photospheric Doppler signal
and also by tracking Doppler features (supergranules) across the solar
disk. We study the rotation curve as a function of latitude, feature
size, and tracking method, and look for global scale flows. This work
was supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin,
and by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP.
Title: Comparison of Granulation Correlation Tracking (CT) and
Feature Tracking (FT) Results from SOHO/MDI and the Swedish Vacuum
Solar Telescope on La Palma
Authors: Shine, R.; Strous, L.; Simon, G.; Berger, T.; Hurlburt, N.;
Tarbell, T.; Title, A.; Scharmer, G.
Bibcode: 1997SPD....28.0262S
Altcode: 1997BAAS...29Q.904S
We have computed photospheric velocity flow maps from simultaneous
observations taken with MDI and at the Swedish Vacuum Solar Tower
(SVST) on La Palma on August 15, 1996. Both sets consist of a series
of photospheric images, and flow maps are computed by following the
local motions of granules. The MDI data have the important advantages
of very stable images and longer continuous coverage of the same area
of the solar surface. This longer coverage is necessary to study the
evolution of mesogranules, supergranules, and to detect possible low
amplitude motions on scales larger than supergranules. However, the
high resolution mode of MDI is limited by the small telescope size to
about 1.2 arc seconds angular resolution and uses a 0.6 arc second pixel
size. This is adequate to show granulation but has the rms constrast
significantly reduced to about 2%. Early efforts adapting techniques
that were successful with higher resolution ground based images gave
poor results and although new methods have now been developed, there
are still some problems with accuracy. On the other hand, the SVST
images have much higher angular resolution (as good as 0.2 arc second)
but suffer from variable atmospheric distortion. They also have a much
smaller field of view. By detailed comparison of the two data sets
and by using CT and FT techniques to track the motions, we hope to
understand the sources of any differences between them and to develop
credible correction parameters to the MDI data sets if necessary. This
work was supported by NASA Grant NAG5-3077 at Stanford and Lockheed
Martin, by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP,
and by the Swedish Royal Academy of Sciences.
Title: Initial Comparison of MDI Photospheric Magnetic Movies and
CDS Transition Region Movies in Quiet Sun
Authors: Tarbell, T.; Brekke, P.; Fludra, A.; Deforest, C.; Saba,
J.; Covington, J.
Bibcode: 1997SPD....28.0111T
Altcode: 1997BAAS...29..881T
We present simultaneous, coaligned movies of photospheric magnetic
fields and transition region (TR) intensities in very quiet sun near
disk center obtained by SOHO in January, 1997. For example, the 22 Jan
1997 CDS movies show He I 584 (2x10(4) K) and O V 630 (2.4 x 10(5) K)
from 16:51 to 19:54 UT, with a 310 x 240 arcsecond field of view, 105
second cadence, and 1.7 arcsecond pixels. MDI photospheric longitudinal
magnetograms, with 60 second cadence and 0.6 arcsecond pixels, have been
coaligned with these. Bright TR emission correlates more strongly with
close bipoles in the photospheric magnetic field than with magnetic
flux alone. Some strong photospheric flux tubes are barely visible
in the TR emission, appearing only occasionally in connections with
nearby weak opposite polarity fields. Bright transient emissions in
the TR are located at places of cancelling opposite polarities in
photospheric magnetic fields. The flux cancellation continues for tens
of minutes or hours in the magnetic movies. Searches for more rapid
magnetic counterparts to these TR transients and for emerging magnetic
flux regions in the movies are under way. This work was supported by
NASA grant NAG5-3077 at Stanford and Lockheed Martin.
Title: Surface Flows in Active Regions
Authors: Bai, T.; Bogart, R. S.; Scherrer, P. H.; Tarbell, T. D.
Bibcode: 1997SPD....28.1701B
Altcode: 1997BAAS...29..921B
Plasma flows around sunspots must influence the stability and
development of sunspots. We have been studying photospheric flows
around sunspots by analyzing dopplergrams and magneto- grams obtained
by the MDI (Michelson Doppler Imager) aboard SOHO. We have found some
interesting phenomena. First, during the growing phase of an active
region, plasmas around sunspots seem to draft downward with a speed of
order of 100 m/s. Second, during the decaying phase of an active region,
plasmas around sunspots flow outward. Outflow speeds range up to several
hundred m/s. Such outflows are prominent during the decaying phase of
a long-lived big active region. Third, there is evidence for flows
within sunspots. Such flows are presumed to be along magnetic field
lines. We will present the details of these results and discuss their
implications on the dynamics and stability of sunspots. MDI research
is supported by NASA contract NAG5-3077 at Stanford University.
Title: Solar Irradiance Variations due to the Quiet Sun Network
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1997SPD....28.0263T
Altcode: 1997BAAS...29..904T
An estimate for the change in total solar irradiance due to quiet sun
network during the 11-year solar cycle is presented. The estimate is
based on measurements of the center-limb contrast function for quiet
sun magnetic elements. These measurements are the result of analysis
of near-simultaneous, co-registered, digital, photometric images of
the photospheric intensity (4300 - 6300 A) and line-of-sight magnetic
field. Images were made with the Lockheed tunable filter instrument at
the Swedish Solar Observatory, La Palma, between 1991 and 1994. The
result is of order 0.1%. The images cover only a tiny fraction of
the surface of the Sun and thus a very large extrapolation is made,
limiting the accuracy of the result. Measurements made by satellite
radiometers indicate that on the time scale of solar activity, the total
solar irradiance is greater at activity maximum than at minimum by about
0.1 to 0.15 %. Our result is consistent with this. Earlier results on
active region plage, using similar data from La Palma, indicate that it
does does not contribute significantly to long-term solar irradiance
variations. This work has been supported by NSF contract ATM-9320353,
by NASA contracts NASW-4612 and NAS8-39747, and by Lockheed IR funds.
Title: The Height and Temporal Structure of X-Ray Bright Points
Authors: Harvey, K. L.; Penn, M.; Tarbell, T.; Saba, J.; Hassler,
D.; Moses, J. D.; Fludra, A.
Bibcode: 1997SPD....28.0124H
Altcode: 1997BAAS...29..883H
On April 12, 1996, several ground-based observatories, the Yohkoh/SXT
and the SOHO/MDI, EIT, SUMER, and CDS instruments participated in a
collaborative study of X-Ray Bright Points (XBPs). During a several
hour period, simultaneous images were obtained of an area centered
at N10E00. At NSO/KP, observations were made of the HeI 1083 nm line
profile from which we have derived the intensity at line center,
equivalent width, and the velocity at every 1 pixel (1.15 arc-seconds)
within an 8 x 8 arc-minute area. Our paper will present the results
of a comparison, spatially and temporally, of these data with changes
in the magnetic field observed by the MDI, intensities and velocities
observed with SUMER and CDS, and the intensity images observed by
the SXT and EIT. We will use this ensemble of intensity, magnetic
and velocity field images to derive the height structure of XBPS,
its variation as a function of time and relation to the associated
magnetic field configuration.
Title: A search for interaction between magnetic fields and
supergranular flows in the network based on MDI observations
Authors: Schrijver, C. J.; Shine, R. A.; Title, A. M.; Hagenaar,
H. J.; Hurlburt, N. E.; Tarbell, T. D.; Simon, G. W.
Bibcode: 1997SPD....28.0243S
Altcode: 1997BAAS...29..901S
We study the supergranular flow field and its temporal evolution in
the quiet Sun as observed with the Michelson Doppler Imager on board
SOHO. We use the intensity images to derive the flow fields using
local correlation tracking. The data sets span one to two days with a
one--minute cadence. We separate areas with a relatively high filling
factor for magnetic concentrations from areas with a low magnetic
filling factor in order to study to what extent the flows influence
the magnetic network in the quiet Sun and vice versa. This work is
supported by NASA Grant NAG5-3077 at Stanford and Lockheed Martin,
and by AFOSR and the Fellows Program of AF Phillips Lab at NSO/SP
Title: Continuous Observations of Solar Magnetic Fields from SOI/MDI
on SOHO
Authors: Hoeksema, J. T.; Bush, R. I.; Scherrer, P. H.; Heck, C.;
Hurlburt, N.; Shine, R.; Tarbell, T.; Title, A.
Bibcode: 1997SPD....28.0127H
Altcode: 1997BAAS...29..884H
The Solar Oscillations Investigation's Michelson Doppler Imager
instrument (SOI/MDI) on SOHO measures the photospheric magnetic field
over the whole disk nearly every 96 minutes with 4" resolution and a
noise level of a few Gauss. Beginning in April 1996, this unprecedented
continuous series of frequent, uniform quality magnetograms provides
a striking view of the continual emergence, motion, evolution, and
interaction of magnetic flux everywhere on the visible solar surface
near solar minimum. These evolving photospheric fields ultimately
drive the variations of the corona and solar wind that affect the
terrestrial environment. Knowledge of the rapidly evolving photospheric
field provides a crucial input for forecasting conditions in the
corona, heliosphere, and geospace. A few magnetograms are available
each day within hours of observation through the SOHO web site at
http://sohowww.nascom.nasa.gov/. These may be used for planning and
forecasting, e.g. to compute models of the solar corona. The remainder
are generally available within a few weeks. Sometimes more focused
campaigns provide magnetic observations as often as once each minute
for up to 8 hours. Campaigns can be run with either the full disk
resolution or with 0.6" pixels in a limited field near the center of
the disk. The SOI project welcomes collaborations. More information
can be found at http://soi.stanford.edu/.
Title: The TRACE Mission
Authors: Wolfson, J.; Bruner, M.; Jurcevich, B.; Lemen, J.; Schrijver,
K.; Shine, R.; Strong, K.; Tarbell, T.; Title, A.; Golub, L.;
Bookbinder, J.; Deluca, E.; Acton, L.; Handy, B.; Kankelborg, C.;
Fisher, R.
Bibcode: 1997SPD....28.0143W
Altcode: 1997BAAS...29..887W
The TRACE (Transition Region and Coronal Explorer) mission will explore
the connections between fine-scale magnetic fields and plasma structures
in the coronal, transition zone and temperature minimum regions of the
sun. TRACE will collect images of solar plasmas at temperatures from
10(4) to 10(7) K, with one arc second spatial resolution and excellent
temporal resolution and continuity. With a scheduled launch date of 15
December 1997, the mission will emphasize collaborative observations
with SoHO, enabling simultaneous observations of high-resolution images,
spectra, and magnetograms. The 30 cm aperture TRACE telescope uses four
normal-incidence coatings for the EUV and UV on quadrants of the primary
and secondary mirrors. Interference filters further isolate 5 different
UV bands. The images are co-aligned and internally stabilized against
spacecraft jitter. A 1024 x 1024 lumigen-coated CCD detector collects
images over an 8.5 x 8.5 arc minute field-of-view. LMATC, SAO, and GSFC
built the TRACE instrument, which was integrated with the GSFC-produced
SMEX spacecraft on 28 February (just over two years from the start
of its development). It will be put into a Sun-synchronous orbit and
operated in coordination with the SoHO Experiment Operations Facility at
GSFC. We are committed to maintaining a publicly accessible data base
for TRACE data. Browsing and data set requesting capabilities will be
provided at Web site www.space.lockheed.com/TRACE/TRACElinks.html. This
site already contains a large volume of information on the mission
including preliminary scientific observing programs and directions
as to how to participate in the mission now and in the future. This
project is supported by NASA contract NAS5-38099.
Title: Performance of the Michelson Doppler Imager Instrument on SOHO
Authors: Scherrer, P.; Bogart, R.; Bush, R.; Duvall, T.; Hoeksema,
J. T.; Kosovichev, A.; Schou, J.; Morrison, M.; Tarbell, T.; Title, A.
Bibcode: 1997SPD....28.0207S
Altcode: 1997BAAS...29..894S
Launched on SOHO in December 1995, the MDI instrument took its 10
millionth filtergram in early April, 1997. The instrument and spacecraft
have performed admirably since commissioning, providing over a year
of virtually uninterrupted time series of velocity and intensity
measurements at moderate resolution, a continuous 60-day time series
of full disk 4" velocity and line depth maps, monthly 72+ hour time
series in various observables, a host of daily 8-hour campaigns, and
full-disk magnetograms every 96 minutes. Another uninterrupted 90-day
interval of nearly full data recovery is scheduled to be completed in
mid July. Various scientific results using MDI data are being presented
at this meeting. About a dozen terabytes of data sets have been created
and archived and normal pipeline processing is now completed soon after
retrieving the data, typically less than a month after the observations
are made. Most of the data products are generally available on the WWW,
see http://soi.stanford.edu. Selected data are available in near real
time. The SOI team welcomes collaborations. Routine and extraordinary
calibrations along with analysis of scientific data sets allow us to
make good estimates of the noise and understand many of the sources
of systematic errors in the instrument. In almost every respect the
instrument performs as well or better than expected before launch,
the primary limitations being photon noise on the short term and
fixed or slowly varying offsets on the long term. We have found that
the Michelsons are somewhat more sensitive to operational temperature
variations than was expected, adding some additional constraints on
our observing sequences.
Title: 3-D Magnetic Field Configuration Late in a Large Two-Ribbon
Flare
Authors: Moore, R. L.; Schmieder, B.; Hathaway, D. H.; Tarbell, T. D.
Bibcode: 1997SPD....28.0157M
Altcode: 1997BAAS...29R.889M
We present H-alpha and coronal X-ray images of the large two-ribbon
flare of 25/26 June 1992 during its long-lasting gradual decay
phase. From these observations we deduce that the 3-D magnetic field
configuration late in this flare was similar to that at and before the
onset of such large eruptive bipolar flares: the sheared core field
running under and out of the flare arcade was S-shaped, and at least one
elbow of the S looped into the low corona. From previous observations
of filament-eruption flares, we infer that such core-field coronal
elbows, though rarely observed, are probably a common feature of the
3-D magnetic field configuration late in large two-ribbon flares. The
rare circumstance that apparently resulted in a coronal elbow of the
core field being visible in H-alpha in our flare was the occurrence
of a series of subflares low in the core field under the late-phase
arcade of the large flare; these subflares probably produced flaring
arches in the northern coronal elbow, thereby rendering this elbow
visible in H-alpha. The observed late-phase 3-D field configuration
presented here, together with the recent sheared-core bipolar magnetic
field model of Antiochos, Dahlburg, and Klimchuk (1994) and recent
Yohkoh SXT observations of the coronal magnetic field configuration
at and before the onset of large eruptive bipolar flares, supports the
seminal 3-D model for eruptive two-ribbon flares proposed by Hirayama
(1974), with three modifications: (1) the preflare magnetic field is
closed over the filament-holding core field; (2) the preflare core
field has the shape of an S (or backward S) with coronal elbows; (3)
a lower part of the core field does not erupt and open, but remains
closed throughout flare, and can have prominent coronal elbows. In
this picture, the rest of the core field, the upper part, does erupt
and open along with the preflare arcade envelope field in which it
rides; the flare arcade is formed by reconnection that begins in the
middle of the core field at the start of the eruption and progresses
from reconnecting closed core field early in the flare to reconnecting
"opened" envelope field late in the flare.
Title: Comparison of supergranular flows from doppler and local
correlation tracking velocities
Authors: Frank, Z.; Hurlburt, N.; Shine, R.; Tarbell, T.; Simon, G.;
Strous, L.; Matt, S.
Bibcode: 1997SPD....28.0259F
Altcode: 1997BAAS...29..903F
Measurements of the flows in the solar photosphere rely upon two
techniques: doppler measurements of the line-of-sight velocity
or tracking of features or patterns moving perpendicular to the
line-of-sight. These methods have differing characteristics. Doppler
measurements can easily measure surface flows near the limb
which are not seriously contaminated by p-modes or other solar
sources. However, they require excellent instrument calibration over
the full field of view. Even then vertical flows within supergranules
are barely detectable. Correlation and feature tracking have proven
useful for estimating transverse velocity using granules and other
tracers. Nevertheless, they can be degraded by the intensity variations
of p-modes and possibly other oscillatory motions, as well as by effects
of limb darkening and foreshortening. The two methods would both be
strengthened through detailed comparisons. Data collected by MDI/SOHO is
ideal for this purpose. The data is co-spatial and co-temporal, and is
all obtained through the same instrument. We compare Doppler velocities
with those obtained through correlation tracking using high-resolution
MDI/SOHO images. We focus on motions at positions exceeding 30 degrees
from disk center. After taking projection effects into account, we
combine the two measurements to form a three-dimensional picture of
the flows in the average supergranule. This work was supported by NASA
Grant NAG5-3077 at Stanford and Lockheed Martin, and by AFOSR and the
Fellows Program of AF Phillips Lab at NSO/SP.
Title: Interactive interface for visualizing and analyzing
multispectral solar images
Authors: Hurlbert, Neal E.; Shine, Richard A.; Tarbell, Theodore D.
Bibcode: 1997SPIE.3017..165H
Altcode:
We present an interactive software tool for manipulating image data,
especially high resolution multi-spectral solar movies and images
from several different instruments. This tool contains procedures for
distortion removal for ground based solar movies, correlation tracking,
image alignments, data compression, 3D FOurier filtering, interactive
viewing of space/time slices in movies, and browsing through data
cubes. This is a compete public domain package based on X windows
and Unix which is currently running on Silicon Graphics and Digital
Equipment workstations. These software tools are freely available to
the international solar community. Many components are also applicable
to image an movie analysis in astrophysics, space physics, and earth
sciences. They are available with documentation via our web pages
under http://www.space.lockheed.com.
Title: Structure and Rotation of the Solar Interior: Initial Results
from the MDI Medium-L Program
Authors: Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Bogart, R. S.;
Bush, R. I.; Hoeksema, J. T.; Aloise, J.; Bacon, L.; Burnette, A.; de
Forest, C.; Giles, P. M.; Leibrand, K.; Nigam, R.; Rubin, M.; Scott,
K.; Williams, S. D.; Basu, Sarbani; Christensen-Dalsgaard, J.; Dappen,
W.; Rhodes, E. J., Jr.; Duvall, T. L., Jr.; Howe, R.; Thompson, M. J.;
Gough, D. O.; Sekii, T.; Toomre, J.; Tarbell, T. D.; Title, A. M.;
Mathur, D.; Morrison, M.; Saba, J. L. R.; Wolfson, C. J.; Zayer, I.;
Milford, P. N.
Bibcode: 1997SoPh..170...43K
Altcode:
The medium-l program of the Michelson Doppler Imager instrument on board
SOHO provides continuous observations of oscillation modes of angular
degree, l, from 0 to ∽ 300. The data for the program are partly
processed on board because only about 3% of MDI observations can be
transmitted continuously to the ground. The on-board data processing,
the main component of which is Gaussian-weighted binning, has been
optimized to reduce the negative influence of spatial aliasing of the
high-degree oscillation modes. The data processing is completed in a
data analysis pipeline at the SOI Stanford Support Center to determine
the mean multiplet frequencies and splitting coefficients. The initial
results show that the noise in the medium-l oscillation power spectrum
is substantially lower than in ground-based measurements. This enables
us to detect lower amplitude modes and, thus, to extend the range of
measured mode frequencies. This is important for inferring the Sun's
internal structure and rotation. The MDI observations also reveal the
asymmetry of oscillation spectral lines. The line asymmetries agree
with the theory of mode excitation by acoustic sources localized in the
upper convective boundary layer. The sound-speed profile inferred from
the mean frequencies gives evidence for a sharp variation at the edge
of the energy-generating core. The results also confirm the previous
finding by the GONG (Gough et al., 1996) that, in a thin layer just
beneath the convection zone, helium appears to be less abundant than
predicted by theory. Inverting the multiplet frequency splittings from
MDI, we detect significant rotational shear in this thin layer. This
layer is likely to be the place where the solar dynamo operates. In
order to understand how the Sun works, it is extremely important to
observe the evolution of this transition layer throughout the 11-year
activity cycle.
Title: On the dynamics of magnetic flux concentrations in quiet
photospheric network.
Authors: Sakai, J. I.; Ryutova, M.; Schrijver, K.; Shine, R. A.;
Tarbell, T. D.; Berger, T. E.; Title, A. M.; Hagenaar, H. J.
Bibcode: 1997BAAS...29T.904S
Altcode:
No abstract at ADS
Title: The Dynamic Quiet Solar Corona: 4 Days of Joint Observing
with MDI and EIT
Authors: Schrijver, C. J.; Shine, R. A.; Hurlburt, N. E.; Tarbell,
T. D.; Lemen, J. R.
Bibcode: 1997ESASP.404..669S
Altcode: 1997cswn.conf..669S
No abstract at ADS
Title: Internal structure and rotation of the Sun: First results
from MDI data
Authors: Kosovichev, A. G.; Schou, J.; Scherrer, P. H.; Bogart, R. S.;
Bush, R. I.; Hoeksema, J. T.; Aloise, J.; Bacon, L.; Burnette, A.;
De Forest, C.; Giles, P. M.; Leibrand, K.; Nigam, R.; Rubin, M.;
Scott, K.; Williams, S. D.; Basu, Sarbani; Christensen-Dalsgaard,
J.; Däppen, W.; Rhodes, E. J., Jr.; Duvall, T. L., Jr.; Howe, R.;
Thompson, M. J.; Gough, D. O.; Sekii, T.; Toomre, J.; Tarbell, T. D.;
Title, A. M.; Mathur, D.; Morrison, M.; Saba, J. L. R.; Wolfson,
C. J.; Zayer, I.; Milford, P. N.
Bibcode: 1997IAUS..181..203K
Altcode:
No abstract at ADS
Title: Temporal Variability in the Quiet Sun Transition Region
Authors: Wikstoøl, Ø.; Hansteen, V. H.; Brynildsen, N.; Maltby,
P.; Kyeldseth-Moe, O.; Harrison, R. A.; Wilhelm, K.; Tarbell, T. D.;
Scherrer, P. H.
Bibcode: 1997ESASP.404..733W
Altcode: 1997cswn.conf..733W
No abstract at ADS
Title: Time-Distance Helioseismology with the MDI Instrument:
Initial Results
Authors: Duvall, T. L., Jr.; Kosovichev, A. G.; Scherrer, P. H.;
Bogart, R. S.; Bush, R. I.; de Forest, C.; Hoeksema, J. T.; Schou,
J.; Saba, J. L. R.; Tarbell, T. D.; Title, A. M.; Wolfson, C. J.;
Milford, P. N.
Bibcode: 1997SoPh..170...63D
Altcode:
In time-distance helioseismology, the travel time of acoustic waves
is measured between various points on the solar surface. To some
approximation, the waves can be considered to follow ray paths that
depend only on a mean solar model, with the curvature of the ray
paths being caused by the increasing sound speed with depth below the
surface. The travel time is affected by various inhomogeneities along
the ray path, including flows, temperature inhomogeneities, and magnetic
fields. By measuring a large number of times between different locations
and using an inversion method, it is possible to construct 3-dimensional
maps of the subsurface inhomogeneities. The SOI/MDI experiment on SOHO
has several unique capabilities for time-distance helioseismology. The
great stability of the images observed without benefit of an intervening
atmosphere is quite striking. It has made it possible for us to detect
the travel time for separations of points as small as 2.4 Mm in the
high-resolution mode of MDI (0.6 arc sec pixel-1). This has
enabled the detection of the supergranulation flow. Coupled with the
inversion technique, we can now study the 3-dimensional evolution of
the flows near the solar surface.
Title: On the Acoustic Emission in the Quiet Sun
Authors: Ryutova, M. P.; Tarbell, T. D.
Bibcode: 1997AAS...18912001R
Altcode: 1997BAAS...29..729R
The interaction of solar acoustic oscillations with magnetic regions on
the Sun strongly depends on the distribution of the random magnetic
fluxes in space and their physical parameters. The dynamics of
differently magnetized regions (sunspots, plages and quiet Sun), their
dispersion properties and their response to the propagation of acoustic
waves are completely different. For example, the enhanced absorption of
acoustic power by sunspot and plage regions is well established. Several
authors who have made similar measurements in quiet regions report that
the quiet Sun shows small but systematic acoustic emission. The effects,
enhanced absorption in active regions and "emission' of acoustic power
in quiet sun, are seen in the same range of wave numbers (0.2<=
k <= 0.6 Mm(-1) ). We report here that an excess of emission of
acoustic power in quiet regions is expected as a result of "inelastic"
scattering of acoustic waves by the random ensembles of widely spaced
magnetic flux tubes. The outcome of the effect strongly depends on the
magnetic filling factor of medium, phi (the total fraction of observed
area occupied by fluxes) and the parameters of acoustic wave. It is
most efficient in those regions of quiet Sun where k(2R^2<<) phi
, R being the characteristic radius of a magnetic flux tube. In this
case, resonant interaction is the most important of several physical
processes contribute to the energy exchange between the wave and
medium. Due to an effect similar to Landau damping, the energy of the
incident acoustic wave is accumulated in the system of magnetic flux
tubes and causes the acoustic wave (of frequency omega ) to damp at a
rate nu_L =~ phi omega . The energy remains for a long time in the form
of flux-tube oscillations. Then, in a time nu_ {rad}(-1) , the resonant
flux tubes radiate their energy as a secondary acoustic waves, where the
radiative damping rate (or the rate of the emission of secondary waves),
nu_ {rad} =~ omega k(2) R(2) . The power of emitted waves expressed
in terms of the parameters of the medium allows one to specify the
regions of an efficient energy input and corresponding range of wave
parameters. This research is supported by NASA contract NAG5-3077 at
Stanford University and NASA contract NAS8-39747 at Lockheed Martin.
Title: High-resolution spectral imaging of the Sun in the far
ultraviolet
Authors: Bruner, Marilyn E.; Tarbell, Theodore D.; Title, Alan M.;
Wuelser, J. -P.; Handy, Brian N.; Zukic, Muamer
Bibcode: 1996SPIE.2804..249B
Altcode:
The Transition Region and Coronal Explorer instrument (TRACE) will
use narrow-band interference filters together with other appropriate
band limiting elements to make high resolution images of the Sun in
the C IV lines at 154.8 and 155.0 nm. Filter observations of solar
C IV emission are complicated by the presence of UV Continuum and
nearby chromospheric lines because of the relatively wide bandpasses
of the narrowest currently available interference filters. TRACE will
use a series of filters to estimate the effects of the UV continuum
and the long-wavelength `leaks' in the blocking filters which we
show are the most important contaminants in the C IV images. Further
improvements in filtergraph performance may be realized through the use
of tunable Fabry-Perot etalons, which have been under development at
Lockheed-Martin. We present test data from a cultured quartz etalon
designed for 155 nm, and will discuss the prospects for etalons
operation at substantially shorter wavelengths.
Title: Precision pointing and image stabilization for the transition
region and coronal explorer solar observatory
Authors: Zimbelman, Darrell; Burt, Joseph; Bruner, Marilyn E.; Tarbell,
Theodore D.; Edwards, Chris G.; Chen, J. R.
Bibcode: 1996SPIE.2739...77Z
Altcode:
This paper presents a detailed description of the precision pointing
system and the image stabilization system (ISS) for the Transition
Region and Coronal Explorer (TRACE) satellite mission. The TRACE
spacecraft is the fourth in NASA's small explorer series of missions
and is scheduled for launch in September 1997. The primary TRACE
science objective is to explore the relationship between the fine scale
magnetic fields in the solar surface and features in the photosphere,
chromosphere, transition region and corona. Quantitative images of
these regions will be collected and used to study the structure and
evolution of the sun's magnetic field with a spatial and temporal
resolution of one arc-second and one second, respectively. TO meet
the science objectives, the instrument payload and the spacecraft
attitude control system are coupled using a guide telescope. The guide
telescope provides both the targeting mechanism and pointing error
signals for the spacecraft feedback control system. In addition, the
guide telescope generates signals used to control the active mirror
of the ISS. Simulation results show that precision target pointing is
maintained to less than 5 arc-seconds, while analysis indicates that
the ISS reduces image motion jitter below the 0.1 arc- second level.
Title: Coordinated SOHO Observations of Polar Plumes
Authors: Deforest, C. E.; Scherrer, P. H.; Tarbell, T.; Harrison,
R. A.; Fludra, A.; Delaboudiniere, J. P.; Gurman, J. B.; Wilhelm,
K.; Lemaire, P.; Hassler, D. M.; Kohl, J. L.; Noci, G.; Fineschi,
S.; Brueckner, G. E.; Howard, R. A.; Cyr, O. C. St.
Bibcode: 1996AAS...188.4909D
Altcode: 1996BAAS...28R.898D
On 7 and 8 March 1996, SOHO instruments engaged in their first
joint science operation, a 12-hr observation of polar plumes
over the South polar coronal hole. The observing mini-campaign
included observations from SOHO, other spacecraft, and ground-based
observatories. Contributing SOHO instruments -- in order of altitude,
MDI, CDS, SUMER, EIT, UVCS, and LASCO -- made overlapping, simultaneous
observations of plume structures from the photosphere out to the
LASCO C3 limit of 32 solar radii. MDI provided line-of-sight surface
magnetograms with a one-min cadence and 0.6 arcsec resolution;
CDS, SUMER, and EIT supplied temperature-sensitive images of the
lower corona with varying cadences and resolutions; UVCS measured
fluctuations in Ly B intensity across the coronal hole with a one-min
cadence at 1.4 R0; and LASCO imaged the entire corona out to 30 R0 in
various visible passbands. Plume footpoints in the lower corona are
observed by EIT and CDS to vary by a factor of two in EUV brightness
with a timescale of tens of minutes, while the structures above are
(as as been previously observed) quiescent on at least a ten-hr time
scale. We present preliminary results of cross-instrument analysis
of the observed plumes, and suggest how this and similar future data
sets can be used to constrain quiet-sun wind acceleration and coronal
heating models for the coronal hole. This research is supported by
the SOI-MDI NASA contract NAG5-3077 at Stanford University. SOHO is
project of international cooperation between NASA and ESA.
Title: The MDI Structure Program: Continuous Monitoring of the
Solar Interior
Authors: Bush, R. I.; Bogart, R. S.; Hoeksema, J. T.; Kosovichev,
A. G.; Scherrer, P. H.; Mathur, D.; Morrison, M.; Tarbell, T. D.
Bibcode: 1996AAS...188.3708B
Altcode: 1996BAAS...28..878B
The Structure Program for the Michelson Doppler Imager instrument
on SOHO is designed to provide valuable helioseismic observations
through a continuously operating 5 kbps telemetry channel. Only about
3% of the total MDI raw data can be transmitted without interruption
to the ground. Therefore, extensive data processing must be performed
by the MDI instrument in order produce data products that will fit
into the restricted telemetry and to meet the scientific observing
requirements. The Structure Program consists of five observing programs:
the Medium-l Velocity, Low-l (LOI) Velocity and Intensity, Limb Figure,
Flux Budget, and Magnetic Proxy. These programs generate spatial
and temporal averages of three of the MDI full disk observables:
the velocity, computed continuum intensity, and the computed line
depth. The performance of these filters will be described. The
goal of the Medium-l Program is to provide reliable measurements
of solar p-modes in the range of the angular degree, l, from 0 to
300, by generating a 23,000 bin spatial average of the full disk
velocity. The Low-l Program re-bins the velocity and continuum intensity
images into 180 bins, with the intent of observing long period global
oscillations. The other three Structure Observations are averaged over
24 minutes with a 12 minute sample time. The Limb Figure extracts a 14
arcsecond annulus at the Sun's limb in order to study long wavelength
oscillations in the observed limb. The Flux Budget and Magnetic Proxy
are 128 by 128 pixel re-bins of the continuum intensity and line depth
observables respectively, to study the solar luminosity and large
scale features. Extensive tests of the individual components of the
Structure Program have been performed during the commissioning phase of
the SOHO operation. Uninterrupted operation started in April 1996. This
research is supported by NASA contract NAG5-3077 at Stanford University.
Title: TRACE: the Transition Region and Coronal Explorer
Authors: Schrijver, C.; Title, A.; Acton, L.; Bruner, M.; Fischer,
R.; Golub, L.; Harrison, R.; Lemen, J.; Rosner, R.; Scharmer, G.;
Scherrer, P.; Strong, K.; Tarbell, T.; Wolfson, J.
Bibcode: 1996AAS...188.6704S
Altcode: 1996BAAS...28..934S
The TRACE mission is designed to obtain images of the solar
transition region and corona of unprecedented quality. With these
images we will be able to explore quantitatively the connections
between the photospheric magnetic field and the associated hot and
tenuous structures in the outer atmosphere. The TRACE telescope has
an aperture of 30 cm, and will observe an 8.5 x 8.5 arcminute field of
view with a resolution of one arcsecond. Finely tuned coatings on four
quadrants on the primary and secondary normal--incidence mirrors will
allow observations in narrow EUV and UV spectral bands. The passbands
are set to Fe IX, XII, and XV lines in the EUV band, while filters
allow observations in C IV, Ly alpha , and the UV continuum using
the UV mirror quadrant. The data thus cover temperatures from 10(4)
K up to 10(7) K. The Sun--synchronous orbit allows long intervals of
uninterrupted viewing. Observations at different wavelengths can be
made in rapid succession with an alignment of 0.1 arcsec. Coordinated
observing with TRACE, SoHO and YOHKOH will give us the first opportunity
to observe all temperature regimes in the solar atmosphere, including
magnetograms, simultaneously from space. TRACE is currently scheduled
to be launched in October 1997. More information can be found on the
web at ``http://pore1.space.lockheed.com/TRACE/welcome.html''.
Title: Initial Results from SOI/MDI High Resolution Magnetograms
Authors: Title, A.; Tarbell, T.; Frank, Z.; Schrijver, C.; Shine,
R.; Wolfson, J.; Zayer, I.; Scherrer, P.; Bush, R.; Deforest, C.;
Hoeksema, T.
Bibcode: 1996AAS...188.6915T
Altcode: 1996BAAS...28..938T
The Michelson Doppler Imager (MDI) on SoHO takes magnetogram
s with resolutions of 1.2 (high resolution) and 4 (full disk)
arcseconds. Movies of 16 hour duration have been constructed in full
disk and high resolution mode. High resolution movies of the south
polar region also have been obtained. In sums of nine high resolution
magnetograms it is possible to detect fields as low as 5 gauss and
total fluxes as low as 5 10(1) 6 Mx. In mid latitude regions new flux
is observed to emerge everywhere. At all latitudes below 60 degrees
flux is mixed on the scale of supergranulation. In the polar region
above 60 degrees only fields of a single polarity are observed above
the detection limit.
Title: Preliminary SOI/MDI Observations of Surface Flows by
Correlation Tracking in the Quiet Solar Photosphere and an Emerging
Active Region
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Saba, J.; Schrijver,
C.; Shine, R.; Title, A.; Simon, G.; Strous, L.
Bibcode: 1996AAS...188.6914T
Altcode: 1996BAAS...28..937T
The extended observation of the solar surface with frequent sampling
provided by MDI on SoHO offers the chance to observe the evolution of
supergranules and to measure surface flows associated with active
regions and perhaps larger scale zonal and meridonal flows. We
have used local correlation tracking of the granulation pattern for
measuring surface flows from MDI high resolution continuum images. The
datasets consist of 1024 x 1024 pixel images collected with a cadence
of one minute and extending many hours each. The images are typically
centered upon the central meridian of the sun and offset to the north
of sun center, spanning roughly 40 degrees of solar longitude and from
approximately -10 to +30 degrees of solar latitude. The latitude
dependence of the differential rotation is evident. We present
preliminary results of our search for signatures of mesogranules,
supergranules and giant cells. On 23 Feb. 1996, we obtained a 12-hour
continuous sequence including quiet sun near disk center and NOAA
region 7946 at about N08 E30. The active region grew rapidly over this
interval, forming several sunpots. We show preliminary comparisons of
the measured flow fields with coaligned SOI/MDI magnetograms taken
at 15-minute intervals. The SOI/MDI program is supported by NASA
grant NAG5-3077.
Title: SOI/MDI Measurements of Horizontal Flows in the South Polar
Region of the Sun by Correlation Tracking and Doppler Shifts
Authors: Simon, G.; Frank, Z.; Hurlburt, N.; Schrijver, C.; Shine,
R.; Tarbell, T.; Title, A.; Deforest, C.
Bibcode: 1996AAS...188.6913S
Altcode: 1996BAAS...28R.937S
On 7 March 1996, the SOHO spacecraft was offset from its usual
disk center pointing for an 11-hour observation of the South
Polar region. MDI took a continuous time series of high resolution
longitudinal magnetograms during this period, in support of the
SOHO-wide Joint Observing Program on polar plumes. It also ran several
hours each of two other programs: one to map the horizontal flows near
the pole by correlation tracking and Doppler shifts, and another to
study wave propagation (e.g., by time-distance helioseismology) at
these high latitudes. In this poster we present preliminary results
from the first program. Both techniques yield measurements of the
differential rotation profile near the pole and of horizontal flows of
supergranulation. These results are compared with each other and with
corresponding measurements in low latitudes. The location of magnetic
features in the horizontal flows is also shown. The SOI/MDI program
is supported by NASA grant NAG5-3077.
Title: Calibration and Performance of the Michelson Doppler Imager
on SOHO.
Authors: Zayer, I.; Morrison, M.; Tarbell, T. D.; Title, A.; Wolfson,
C. J.; MDI Engineering Team; Bogart, R. S.; Bush, R. I.; Hoeksema,
J. T.; Duvall, T.; Sa, L. A. D.; Scherrer, P. H.; Schou, J.
Bibcode: 1996AAS...188.3712Z
Altcode: 1996BAAS...28..879Z
The Michelson Doppler Imager (MDI) instrument probes the interior
of the Sun by measuring the photospheric manifestations of solar
oscillations. MDI was launched in December, 1995, on the Solar and
Heliospheric Observatory (SOHO) and has been successfully observing the
Sun since then. The instrument images the Sun on a 1024 x 1024 pixel CCD
camera through a series of increasingly narrow spectral filters. The
final elements, a pair of tunable Michelson interferometers, enable
MDI to record filtergrams with FWHM bandwidth of 94 m Angstroms with
a resolution of 4 arcseconds over the whole disk. Images can also be
collected in MDI's higher resolution (1.25 arcsecond) field centered
about 160 arcseconds north of the equator. An extensive calibration
program has verified the end-to-end performance of the instrument
in flight. MDI is working very well; we present the most important
calibration results and a sample of early science observations. The
Image Stabilization System (ISS) maintains overall pointing to
better than ca. 0.01 arcsec, while the ISS' diagnostic mode allows
us to measure spectrally narrow pointing jitter down to less than
1 mili-arcsec. We have confirmed the linearity of each CCD pixel to
lie within 0.5%\ (the FWHM of the distribution is 0.2% ), and have to
date not detected any contamination on the detector, which is cooled
to -72 C. The noise in a single Dopplergram is of the order of 20 m/s,
and initial measurements of transverse velocities are reliable to 100
m/s. The sensitivity of magnetograms reach 5G in a 10 minute average
(15G in a single magnetogram). MDI's primary observable, the p-modes
from full-disk medium-l data, are of very high quality out to l=300
as seen in the initial l-nu diagram. The SOI-MDI program is supported
by NASA contract NAG5-3077.
Title: Phenomena in an emerging active region. I. Horizontal dynamics.
Authors: Strous, L. H.; Scharmer, G.; Tarbell, T. D.; Title, A. M.;
Zwaan, C.
Bibcode: 1996A&A...306..947S
Altcode:
Horizontal dynamics in observations of NOAA AR 5617 are studied by
tracking individual elements through the field of view. Small magnetic
elements of both magnetic polarities occur everywhere in the active
region, and define unipolar thread-like concentrations of magnetic
field of up to 15Mm length. The horizontal granular flow field in
the active region is divergent (e-time scale 2.1hours) and clockwise
(time scale 32hours). Facular elements are tracers of (clumps of)
fluxtubes. A hierarchy of movement of magnetic elements appears:
Facular elements everywhere in the active region move obliquely toward
the edges of the active region of the same polarity as their own, faster
than those edges (as defined by strings of pores) move apart. The pores
move along the edges toward the major sunspots of their own polarity,
and the major sunspots of either polarity move apart. The separation
velocity of both polarities of facular elements is about 0.84km/s, of
pores about 0.73km/s, and that of the major sunspots is about 0.50km/s.
Title: Relative Altitude of Hot and Cool Post-Flare Loops
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Wiik, J. E.; Tarbell,
T.; Heinzel, P.; Kitai, R.; Funakoshi, Y.; Anwar, B.
Bibcode: 1996ASPC..111..359V
Altcode: 1997ASPC..111..359V
The authors collected a unique set of data obtained simultaneously at
4 different ground based observatories and with the Yohkoh satellite
to study the relationship between hot X-ray and cool Hα post-flare
loops as they evolved during the long gradual phase of the X3.9 flare
which occurred on 25 June 1992. They found reasonably good agreement
between the computed 'theoretical' cooling times and the 'observed'
cooling times derived from the relative altitudes of hot and cool
loops. Taking into account evolutionary effects, the authors also found
similar shape and configuration of hot and cool loops during the entire
observing period and confirmed that at any time hot loops are at higher
altitude than cool loops, suggesting that cool loops indeed descend
from hot loops. The results provide support for the reconnection model.
Title: Heating of Active Region Corona by Transient Brightenings
(Microflares)
Authors: Shimizu, T.; Tsuneta, T.; Title, A.; Tarbell, T.; Shine,
R.; Frank, Z.
Bibcode: 1996mpsa.conf...37S
Altcode: 1996IAUCo.153...37S
No abstract at ADS
Title: The Solar Oscillations Investigation - Michelson Doppler Imager
Authors: Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema, J. T.;
Kosovichev, A. G.; Schou, J.; Rosenberg, W.; Springer, L.; Tarbell,
T. D.; Title, A.; Wolfson, C. J.; Zayer, I.; MDI Engineering Team
Bibcode: 1995SoPh..162..129S
Altcode:
The Solar Oscillations Investigation (SOI) uses the Michelson Doppler
Imager (MDI) instrument to probe the interior of the Sun by measuring
the photospheric manifestations of solar oscillations. Characteristics
of the modes reveal the static and dynamic properties of the
convection zone and core. Knowledge of these properties will improve
our understanding of the solar cycle and of stellar evolution. Other
photospheric observations will contribute to our knowledge of the
solar magnetic field and surface motions. The investigation consists
of coordinated efforts by several teams pursuing specific scientific
objectives.
Title: The TRACE Mission
Authors: Title, A.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong,
K.; Tarbell, T.; Wolfson, J.; Golub, L.; Fisher, R.
Bibcode: 1995AAS...18710107T
Altcode: 1995BAAS...27.1427T
We have seen significant progress in the flight preparation of the
TRACE (Transition Region and Coronal Explorer) instrument during
the last few months. TRACE, approved for 1997 launch, will collect
images of solar plasmas at temperatures from 10(4) to 10(7) K, with
one arc second spatial resolution and excellent temporal resolution
and continuity. TRACE will explore the connections between fine-scale
magnetic fields and plasma structures in the coronal, transition
zone and temperature minimum regions of the sun. The 1997 launch
opportunity allows for collaborative observations from Earth orbit
with the SoHO instruments stationed at L1. Simultaneous observations
including high-resolution images, spectra, and magnetograms are
possible. The 30 cm aperture TRACE telescope uses four normal-incidence
coatings for the EUV and UV on quadrants of the primary and secondary
mirrors. Interference filters further isolate 5 different UV bands. The
images are coaligned and internally stabilized against spacecraft
jitter. A 1024 x 1024 CCD detector collects images over an 8.5 x 8.5
arc minute field-of-view. TRACE is launched on a GSFC SMEX spacecraft
into a Sun-synchronous orbit. It will operate in coordination with
the SoHO Experiment Operations Facility at GSFC. We are committed to
maintaining an publicly accessible data base for TRACE data. Browsing
and data set requesting capabilities will be included at our World
Wide Web site (see http://www.space.lockheed.com/TRACE/welcome.html).
Title: Precise Photometry Mission -- Measuring Stellar
Microvariability from Space
Authors: Brown, T. M.; Borucki, W.; Frandsen, S.; Gilliland, R. L.;
Jones, A.; Noyes, R. W.; Tarbell, T.; Title, A.; Ulrich, R. K.
Bibcode: 1995AAS...187.7111B
Altcode: 1995BAAS...27R1385B
Atmospheric scintillation limits the precision attainable by
ground-based photometry; this limitation is a major obstacle to
progress in several fields, notably asteroseismology of Sun-like
stars. A space-borne photometric telescope could operate near the shot
noise limit, removing this obstacle and providing new opportunities
for inquiry. As part of the program for New Mission Concepts in
Astrophysics, we are studying the scientific rewards and technological
challenges associated with a Precise Photometry Mission (PPM). The
baseline performance goal for the PPM is to measure solar-like
pulsations (amplitude 3 mu mag) in G stars in the Hyades with a S/N
ratio of 4 in 10 days of observing time. This performance would also
allow detection of transits of Earth-sized planets of main-sequence
stars, extremely precise characterization of the light curves of
micro-lensing events, and other novel applications. The technical
approach envisioned for the PPM is wide-band CCD photometry. The study
that is underway focuses on two aspects of the required technology: (1)
Are CCD detectors able to provide the necessary very high S/N within
the spacecraft operating environment? (2) Can new lightweight mirror
and telescope structure technology be applied to yield significant
reductions in mission cost? We are addressing both questions with
laboratory tests, including time-series performance tests of suitable
CCDs, and thermal and mechanical tests of a SiC telescope mirror. In
addition to describing PPM's scientific aims and technical rationale,
we report preliminary results of the CCD tests.
Title: Motion and Evolution of Solar Magnetic Elements
Authors: Berger, T. E.; Schrijver, C. J.; Shine, R. S.; Tarbell,
T. D.; Title, A. M.; Scharmer, G.
Bibcode: 1995AAS...18710104B
Altcode: 1995BAAS...27.1426B
The dynamics of sub-arcsecond solar magnetic flux tubes are analyzed
based on very-high resolution movies of photospheric bright points
obtained in 1994 at the 50-cm Swedish Solar Vacuum Telescope (SVST)
on the island of La Palma, Spain. The bright points are imaged using
a 12 Angstroms bandpass interference filter centered at 4305 Angstroms
in the ``G Band'' molecular bandhead of the CH molecule. The image sets
typically consist of up to 4 hours of consecutive images taken at a 10
to 20 second cadence. Spatial resolution throughout the movies averages
less than 0\arcsec.5 and many frames in the sets exhibit resolution
down to 0\arcsec.25. Magnetic flux elements in the photosphere are
shown to move continually along the intergranular lanes at speeds
of up to 5 km/sec and ranges up to several thousand km. Evolution of
individual magnetic elements is dominated by the local evolution of
surrounding granules. Fragmentation and merging is the fundamental
mode of evolution of the majority of magnetic elements seen in our
data. Rotation and folding of chains or groups of elements is also
frequently observed. The time scale for the fragmentation/merging
evolution of the elements is on the order of the lifetime of granulation
(6--8 minutes), but significant morphological changes are seen to
occur on time scales as short as 100 seconds. The concept of a stable,
isolated, sub-arcsecond magnetic flux element in the solar photosphere
is inconsistent with the observations presented here.
Title: Solar Lite
Authors: Rosenberg, W. J.; Title, A. M.; Tarbell, T. D.
Bibcode: 1995AAS...187.7406R
Altcode: 1995BAAS...27.1390R
Solar Lite is a one meter diameter Gregorian diffraction limited
solar telescope using Silicon Carbide optics that is currently being
fabricated by the Vavilov Optical Institute in St. Petersburg,
Russia. The mirror is made of a two phase ceramic that is 83%
SiC and 17% Si. A 63 cm, f/1.5 test sphere has been fabricated and
polished. The test mirror weighs 12 Kg, the surface error 1/40 wave RMS,
and the surface roughness is 18 angstroms RMS. The telescope structure
is a corrugated aluminum tube (bellows) with Invar stringers. This
approach is possible because Russian material technology is capable
of producing thin Invar sheets with a coefficient of linear expansion
of 3x10(-7) . The primary mirror has a design weight of 30 kg and the
entire telescope has a total weight of 150 kg. A preliminary design
review has been completed. The detailed design of the telescope will be
completed in January 1996. We hope to fly the telescope with a vector
magnetograph in a sun synchronous orbit. The completion date for the
telescope is July 1997.
Title: New Observations of Subarcsecond Photospheric Bright Points
Authors: Berger, T. E.; Schrijver, C. J.; Shine, R. A.; Tarbell,
T. D.; Title, A. M.; Scharmer, G.
Bibcode: 1995ApJ...454..531B
Altcode:
We have used an interference filter centered at 4305 Å within the
bandhead of the CH radical (the "G band") and real-time image selection
at the Swedish Vacuum Solar Telescope on La Palma to produce very
high contrast images of subarcsecond photospheric bright points at all
locations on the solar disk. During the 6 day period of 1993 September
15-20 we observed active region NOAA 7581 from its appearance on the
East limb to a near disk-center position on September 20. A total of
1804 bright points were selected for analysis from the disk center image
using feature extraction image processing techniques. The measured FWHM
distribution of the bright points in the image is subnormal with a modal
value of 220 km (0".30) and an average value of 250 km (0".35). The
smallest measured bright point diameter is 120 km (0".17) and the
largest is 600 km (0".69). Approximately 60% of the measured bright
points are circular (eccentricity ∼1.0), the average eccentricity
is 1.5, and the maximum eccentricity corresponding to filigree in
the image is 6.5. The peak contrast of the measured bright points is
normally distributed. The contrast distribution variance is much greater
than the measurement accuracy, indicating a large spread in intrinsic
bright-point contrast. When referenced to an averaged "quiet-Sun area 1n
the image, the modal contrast is 29% and the maximum value is 75%; when
referenced to an average intergranular lane brightness in the image,
the distribution has a modal value of 61 % and a maximum of 119%. The
bin-averaged contrast of G-band bright points is constant across the
entire measured size range. The measured area of the bright points,
corrected for population and selection effects, covers about 1.8% of
the total image area. Large pores and micropores occupy an additional
2% of the image area, implying a total area fraction of magnetic
proxy features in the image of 3.8%. We discuss the implications of
this area fraction measurement in the context of previously published
measurements which show that typical active region plage has a magnetic
filling factor on the order of 10% or greater. The results suggest that
in the active region analyzed here, less than 50% of the small-scale
magnetic flux tubes are demarcated by visible proxies such as bright
points or pores.
Title: Vorticity and Divergence in the Solar Photosphere
Authors: Wang, Yi; Noyes, Robert W.; Tarbell, Theodore D.; Title,
Alan M.
Bibcode: 1995ApJ...447..419W
Altcode:
We have studied an outstanding sequence of continuum images of the
solar granulation from Pic du Midi Observatory. We have calculated the
horizontal vector flow field using a correlation tracking algorithm,
and from this determined three scalar fields: the vertical component of
the curl, the horizontal divergence, and the horizontal flow speed. The
divergence field has substantially longer coherence time and more power
than does the curl field. Statistically, curl is better correlated
with regions of negative divergence that is, the vertical vorticity is
higher in downflow regions, suggesting excess vorticity in intergranular
lanes. The average value of the divergence is largest (i.e., outflow
is largest) where the horizontal speed is large; we associate these
regions with exploding granules. A numerical simulation of general
convection also shows similar statistical differences between curl
and divergence. Some individual small bright points in the granulation
pattern show large local vorticities.
Title: The Transition Region and Coronal Explorer (trace)
Authors: Title, A.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong,
K.; Tarbell, T.; Wolfson, J.; Golub, L.; Bookbinder, J.; Fisher, R.
Bibcode: 1995ESASP.376b.505T
Altcode: 1995help.confP.505T; 1995soho....2..505T
No abstract at ADS
Title: Soi/mdi Studies of Active-Region Seismology and Evolution
Authors: Tarbell, T. D.; Title, A.; Hoeksema, J. T.; Scherrer, P.;
Zweibel, E.
Bibcode: 1995ESASP.376b..99T
Altcode: 1995help.confP..99T; 1995soho....2...99T
The Solar Oscillations Investigation (SOI) will study active regions
in many ways using both helioseismic and conventional observing
techniques. The Michelson Doppler Imager (MDI) instrument can
make Doppler, continuum and line depth images and also longitudinal
magnetograms, showing either the full disk or a high resolution field of
view. There will be a Dynamics Program of continuous full disk Doppler
observations for two months per year, many Campaign Programs of 8 hours
continuous observing per day, and a synoptic Magnetic Program of about
15 full disk magnetograms per day. This paper gives a brief description
of some of the scientific plans, measurements, and observing programs.
Title: Solar Irradiance Variations due to Active Region Faculae
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1995SPD....26..512T
Altcode: 1995BAAS...27..959T
No abstract at ADS
Title: Frame Selection Techniques for Solar Movies
Authors: Shine, R. A.; Tarbell, T.; Title, A.; Scharmer, G.; Simon,
G.; Brandt, P.; Berger, T.
Bibcode: 1995SPD....26..506S
Altcode: 1995BAAS...27..957S
No abstract at ADS
Title: Flux Emergence in a Sunspot Moat and Young Active Region
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.;
Simon, G. W.; Brandt, P. N.
Bibcode: 1995SPD....26.1007T
Altcode: 1995BAAS...27..978T
No abstract at ADS
Title: Properties of Sub-Arcsecond Facular Bright Points
Authors: Berger, T.; Schrijver, C.; Shine, R.; Tarbell, T.; Title,
A.; Scharmer, G.
Bibcode: 1995SPD....26..505B
Altcode: 1995BAAS...27..957B
No abstract at ADS
Title: Michelson Doppler Imager (MDI) Performance Characteristics
Authors: Zayer, I.; Morrison, M.; Pope, T.; Rosenberg, W.; Tarbell,
T.; Title, A.; Wolfson, J.; Bogart, R. S.; Hoeksema, J. T.; Milford,
P.; Scherrer, P. H.; Schou, J.
Bibcode: 1995ASPC...76..456Z
Altcode: 1995gong.conf..456Z
No abstract at ADS
Title: Observations of Convection
Authors: Title, A. M.; Hurlburt, N.; Schrijver, C.; Shine, R.;
Tarbell, T.
Bibcode: 1995ESASP.376a.113T
Altcode: 1995heli.conf..113T; 1995soho....1..113T
The primary goal of the Solar Oscillations Investigation is
to understand the interior of the Sun using the techniques of
helioseismology. In addition the Michelson Doppler Imager produces
images of the solar surface with sufficient resolution to measure
surface flows via the technique of local correlation tracking and
magnetograms which allow feature tracking of magnetic fields. It will
be possible to measure the evolution of meso and supergranulation, the
evolution of the meso and supergranulation patterns, and the motion of
magnetic elements in the flow field. With observing periods of 8 hours
one should be able to detect large scale flow fields of 10 m/s second
or less. The magnetograms will provide the data to understand how the
cell patterns evolve as a function of magnetic field configuration.
Title: Status of the Solar Oscillations Investigation - Michelson
Doppler Imager
Authors: Scherrer, P. H.; Bogart, R. S.; Bush, R. I.; Hoeksema,
J. T.; Milford, P.; Schou, J.; Pope, T.; Rosenberg, W.; Springer,
L.; Tarbell, T.; Title, A.; Wolfson, J.; Zayer, I.
Bibcode: 1995ASPC...76..402S
Altcode: 1995gong.conf..402S
No abstract at ADS
Title: The transition region and coronal explorer (TRACE)
Authors: Tarbell, T. D.; Bruner, M.; Jurcevich, B.; Lemen, J.; Strong,
K.; Title, A.; Wolfson, J.
Bibcode: 1994ESASP.373..375T
Altcode: 1994soho....3..375T
No abstract at ADS
Title: On the Relation Between Facular Bright Points and the
Magnetic Field
Authors: Berger, Thomas; Shine, Richard; Tarbell, Theodore; Title,
Alan; Scharmer, Goran
Bibcode: 1994AAS...185.8607B
Altcode: 1994BAAS...26.1465B
Multi-spectral images of magnetic structures in the solar photosphere
are presented. The images were obtained in the summers of 1993 and
1994 at the Swedish Solar Telescope on La Palma using the tunable
birefringent Solar Optical Universal Polarimeter (SOUP filter), a 10
Angstroms wide interference filter tuned to 4304 Angstroms in the band
head of the CH radical (the Fraunhofer G-band), and a 3 Angstroms wide
interference filter centered on the Ca II--K absorption line. Three
large format CCD cameras with shuttered exposures on the order of
10 msec and frame rates of up to 7 frames per second were used to
create time series of both quiet and active region evolution. The
full field--of--view is 60times 80 arcseconds (44times 58 Mm). With
the best seeing, structures as small as 0.22 arcseconds (160 km) in
diameter are clearly resolved. Post--processing of the images results
in rigid coalignment of the image sets to an accuracy comparable to the
spatial resolution. Facular bright points with mean diameters of 0.35
arcseconds (250 km) and elongated filaments with lengths on the order
of arcseconds (10(3) km) are imaged with contrast values of up to 60
% by the G--band filter. Overlay of these images on contemporal Fe I
6302 Angstroms magnetograms and Ca II K images reveals that the bright
points occur, without exception, on sites of magnetic flux through the
photosphere. However, instances of concentrated and diffuse magnetic
flux and Ca II K emission without associated bright points are common,
leading to the conclusion that the presence of magnetic flux is a
necessary but not sufficient condition for the occurence of resolvable
facular bright points. Comparison of the G--band and continuum images
shows a complex relation between structures in the two bandwidths:
bright points exceeding 350 km in extent correspond to distinct
bright structures in the continuum; smaller bright points show no
clear relation to continuum structures. Size and contrast statistical
cross--comparisons compiled from measurements of over two-thousand
bright point structures are presented. Preliminary analysis of the time
evolution of bright points in the G--band reveals that the dominant mode
of bright point evolution is fission of larger structures into smaller
ones and fusion of small structures into conglomerate structures. The
characteristic time scale for the fission/fusion process is on the
order of minutes.
Title: Facular Contrast and Hot Wall Models of Flux Tubes
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1994AAS...185.8606T
Altcode: 1994BAAS...26.1465T
Solar rotation causes features on its surface to be viewed at different
angles. The appearance of active region faculae changes dramatically
with viewing angle. They have minimum contrast at disk center, but
appear bright near the limb. The nature of this center-limb variation
is related to the structure of the individual flux tubes comprising
faculae. One class of models depict a facula as an evacuated flux tube
with hot walls and a depressed cool floor (hot wall model). Another
depicts them as hot clouds, because of internal heating. Both can
explain the observed center-limb variation in contrast. In this paper
we ask whether there are other observable phenomena that can help
differentiate between these models. The observations were obtained at
the Swedish Solar Observatory, La Palma, using the Lockheed tunable
filter. The data consist of co-registered images of line-of-sight
magnetic field and of continuum intensity. The correlation between
strong magnetic field and continuum intensity in active region faculae
shows a remarkable and reproducible change between heliocentric angles
of 50deg and 60deg . These results support the hot wall model, but not
the hot cloud model. Hybrid models in which the flux tube has properties
of both models cannot by ruled out. This work has been supported by
NSF contract ATM-9320353, by NASA contracts NASW-4612 and NAS8-39747,
and by Lockheed IR funds.
Title: On the Temperature and Velocity through the Photosphere of
a Sunspot Penumbra
Authors: del Toro Iniesta, J. C.; Tarbell, T. D.; Ruiz Cobo, B.
Bibcode: 1994ApJ...436..400D
Altcode:
We investigate the structure in depth of a sunspot penumbra by means
of the inversion code of the radiative transfer equation proposed
by Ruiz Cobo & del Toro Iniesta (1992), applied to a set of
filtergrams of a sunspot, scanning the Fe I line at 5576.1 A, with
a sampling interval of 30 mA, from -120 to 120 mA from line center
(data previously analyzed by Title et al. 1993). The temperature
structure of this penumbra is obtained for each of the 801 pixels
selected (0.32 sec x 0.32 sec). On the average, the temperatures seem
to decrease as we move inward, but the differences are of the order
of the rms values (approximately equal 100-200 K) at a given distance
to sunspot center. The outer parts of the penumbra have also a bigger
curvature in the T versus log tau5 relation than the inner
parts. We realize, however, that these differences might be influenced
by possible stray light effects. Compared to the quiet Sun, penumbral
temperatures are cooler at deep layers and hotter at high layers. A mean
penumbral model atmosphere is presented. The asymmetries observed in the
intensity profile (the line is magnetically insensitive) are deduced
to be produced by strong gradients of the line-of-sight velocity that
sharply vary spatially along slices of almost constant distance to
sunspot center. These variations suggest that such gradients are not
only needed to explain the broadband circular polarization observed
in sunspots (see Sanchez Almeida & Lites 1992) but are a main
characteristic of the fine-scale penumbra. The results are compatible
with an Evershed flow present everywhere, but its gradient with depth
turns out to vary so that the flow seems to be mainly concentrated in
some penumbral fibrils when studied through Dopplergrams. Finally,
as by-products of this study, we put constraints to the practical
usefulness of the Eddington-Barbier relation, and we explain the values
of the Fourier Dopplergrams to be carrying information of layers around
the centroid of the generalized response function of Dopplergrams to
velocity fluctuations.
Title: Trace — The transition region and coronal explorer
Authors: Strong, K.; Bruner, M.; Tarbell, T.; Title, A.; Wolfson, C. J.
Bibcode: 1994SSRv...70..119S
Altcode:
TRACE is a single-instrument solar mission that will be put into
a Sunsynchronous polar orbit and will obtain continuous solar
observations for about 8 months per year. It will collect images of
solar plasmas at temperatures from 104 to 107
K, with 1-arcsec spatial resolution and excellent temporal resolution
and continuity. With such data, we expect to gain a new understanding
of many solar and stellar problems ranging from coronal heating to
impulsive magnetohydrodynamic phenomena.
Title: High-Resolution Observations of the Evershed Effect in Sunspots
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Smith, K.; Frank,
Z. A.; Scharmer, Goran
Bibcode: 1994ApJ...430..413S
Altcode:
High spatial resolution movies of sunspots taken at the Swedish
Solar Observatory on La Palma reveal that the Evershed effect is time
dependent. Outward proper motions are visible in both the continuum
and Dopplergrams. These can be tracked over most of the width of
the penumbra and overlap regions that show inward moving penubral
grains. The radial spacing between the moving structures is about 2000
km, and they exhibit irregular repetitive behavior with a typical
interval of 10 minutes. These are probably the cause of 10 minutes
oscillations sometimes seen in a penumbral power spectra. Higher
velocities are spatially correlated with the relatively darker regions
between bright filaments. Regions with a strong variation in the Doppler
signal show peak-to-peak modulations of 1 km/s on an average velocity
of about 3-4 km/s. The proper motion velocity is approximately constant
from the iner penumbra and generally larger than the Doppler velocity
when both are interpreted as projections of horizontal motion. Regions
where thay are consistent suggest a typical horizontal velocity of
3.5 km/s. Some proper motion velocites as high as 7 km/s are seen,
but these are less certain. The temporal behavoir shows a correlation
between increased Doppler signal and increased continuum intensity,
the opposite of the spatial correlation. When spatially averaged
across filaments and over time, the averaged Evershed effect has a peak
horizontal component near the outer edge of the penumbra of 2.0 km/s
with evidence for a 200-400 m/s upward component. The latter depends
on an uncertain absolute velocity calibration. If real it could be
an actual upward component or a penumbral analogue of the convective
blueshift seen in the quiet Sun.
Title: Dynamics of the Evershed effect
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Smith, K.; Frank,
Z. A.; Scharmer, G.
Bibcode: 1994ASIC..433..197S
Altcode:
No abstract at ADS
Title: Photospheric origins of chromospheric and coronal activity
Authors: Tarbell, Theodore
Bibcode: 1994lock.reptQ....T
Altcode:
This contract is for a two-year research study of the origins of
activity in the upper atmosphere of the sun. The approach is to collect
high resolution images of the lower atmosphere on observing runs at the
Swedish Solar Observatory on La Palma, Canary Islands, Spain. The best
observations are analyzed and compared with data from other telescopes
and/or theoretical models, to study magnetic flux emergence, coronal
heating, and various dynamic phenomena and transients. Software for
analysis and visualization of the data is developed as needed. The
contract is being performed by the Solar and Astrophysics Laboratory,
part of the Lockheed Palo Alto Research Laboratory (LPARL) of the
Research and Development Division (RDD) of Lockheed Missiles and Space
Co., Inc. (LMSC).
Title: The Solar Oscillation Investigation - Michelson Doppler Imager
(SOI-MDI)
Authors: Hoeksema, J. T.; Bogart, R. S.; Bush, R. I.; Milford, P. N.;
Pope, T.; Rosenberg, W.; Scherrer, P. H.; Springer, L.; Tarbell, T.;
Title, A.; Wolfson, J.; Zayer, I.
Bibcode: 1993BAAS...25.1192H
Altcode:
No abstract at ADS
Title: Michelson Doppler Imager Calibration and Performance Tests
Authors: Zayer, I.; Bogart, R. S.; Hoeksema, J. T.; Tarbell, T.
Bibcode: 1993BAAS...25.1192Z
Altcode:
No abstract at ADS
Title: Multitemperature Observations of an Emerging Flux Region
Authors: Bruner, M. E.; Acton, L. W.; Brown, W. A.; Lemen, J. R.;
Shine, R.; Strong, K. T.; Tarbell, T.; Dulk, G.; Tsuneta, S.; Bastian,
T.; Dame, L.
Bibcode: 1993BAAS...25.1179B
Altcode:
No abstract at ADS
Title: Observations of an Emerging Flux Region
Authors: Brown, W. A.; Acton, L. W.; Bruner, M. E.; Lemen, J. R.;
Shine, R.; Strong, K. T.; Tarbell, T.; Dulk, G.; Tsuneta, S.; Bastian,
T.; Dame, L.
Bibcode: 1993BAAS...25Q1214B
Altcode:
No abstract at ADS
Title: The Quiet Sun Network and Solar Irradiance Variations
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1993BAAS...25R1183T
Altcode:
No abstract at ADS
Title: Solar Coronal Magnetic Field Topology Inferred from High
Resolution Optical and X-ray Movies
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine,
R.; Title, A.; Acton, L.
Bibcode: 1993BAAS...25.1208T
Altcode:
No abstract at ADS
Title: Invited Talk: (Low-Cost Missions in High Resolution Solar
Physics Using Small Spacecraft)
Authors: Tarbell, T. D.
Bibcode: 1993BAAS...25.1180T
Altcode:
No abstract at ADS
Title: Vertical Stratification of a Sunspot Penumbra
Authors: del Toro Iniesta, J. C.; Tarbell, T. D.; Ruiz Cobo, B.
Bibcode: 1993BAAS...25Q1221D
Altcode:
No abstract at ADS
Title: La Palma Observations During the CoMStOC'92 Campaign
Authors: Shine, R.; Tarbell, T.; Topka, K.; Frank, Z.; Title, A.;
Scharmer, G.
Bibcode: 1993BAAS...25S1223S
Altcode:
No abstract at ADS
Title: ``The Active Sun'': Educational Videotapes on Solar Physics
for College Astronomy
Authors: Hurlburt, N.; Title, A.; Tarbell, T.; Frank, Z.; Topka, K.;
Shine, R.
Bibcode: 1993AAS...182.1002H
Altcode: 1993BAAS...25..809H
We present a series of short, educational documentaries on solar
physics aimed at college-level general astronomy courses. These
tapes highlight recent advances in high-resolution solar astronomy
and in theoretical and computational modeling of solar physics
with particular focus on dynamical phenomena. The relevant physical
mechanisms, theoretical interpretations and observational techniques
are discussed. These include granulation, the theory of convection,
five-minute oscillations, sunspots, magnetic fields, seeing and
dopplergrams. VHS tapes are available to researchers and educators
through a variety of distributors. This work supported by Lockheed
Independent Research Funds.
Title: Solar Coronal Magnetic Field Topology Inferred from High
Resolution Optical and X-ray Movies
Authors: Tarbell, T.; Frank, Z.; Hurlburt, N.; Morrison, M.; Shine,
R.; Title, A.; Acton, L.
Bibcode: 1993AAS...182.4805T
Altcode: 1993BAAS...25R.880T
We are using high resolution digital movies of solar active regions
in optical and X-ray wavelengths to study solar flares and other
transients. The optical movies were collected at the Swedish Solar
Observatory on La Palma using the Lockheed tunable filtergraph
system, in May - July, 1992. They include longitudinal and transverse
magnetograms, H-alpha Doppler and intensity images at many wavelengths,
Ca K, Na D, and white light images. Simultaneous X-ray images from
Yohkoh are available much of the time. We are learning several ways to
establish the connectivity of some coronal magnetic field lines. Some
of the clues available are: magnetic footpoint polarities and transverse
field directions; H-alpha fibrils and loops seen in several wavelengths;
proper motion and Doppler shifts of blobs moving along field lines;
footpoint brightening in micro-flares; spreading of flare ribbons
during gradual phases of flares; X-ray morphology and correlations with
H-alpha; and draining of flare loops. Examples of each of these will
be shown on video. This work is supported by NASA Contracts NASW-4612
and NAS8-37334 and by Lockheed Independent Research Funds.
Title: On the Magnetic and Velocity Field Geometry of Simple Sunspots
Authors: Title, Alan M.; Frank, Zoe A.; Shine, Richard A.; Tarbell,
Theodore D.; Topka, Kenneth P.; Scharmer, Goran; Schmidt, Wolfgang
Bibcode: 1993ApJ...403..780T
Altcode:
It is presently shown that a simple sunspot model with azimuthal
variations in inclination, but lacking azimuthal field-strength
variations, is free from azimuthal Lorentz forces. The meridional
currents arising from the inclination variations are parallel to the
field lines, suggesting that a cylindrically symmetric magnetostatic
sunspot model can be perturbed into one with azimuthal variations in
inclination with adjustment of the meridional force balance.
Title: Percolation theory and the geometry of photospheric magnetic
flux concentrations
Authors: Balke, A. C.; Schrijver, C. J.; Zwaan, C.; Tarbell, T. D.
Bibcode: 1993SoPh..143..215B
Altcode:
The magnetic field in solar active regions forms a highly structured
pattern without an apparent length scale. We study this pattern in
detail for a plage and its surroundings observed with the Swedish Solar
Observatory on La Palma. The magnetogram has a resolution of about
1/3″, after image optimisation. We analysed the geometric properties
of isolated patches of magnetic flux. Patches with a linear size up to
3″ appear to be statistically self-similar, with a fractal dimension
ofDf = 1.54 ± 0.05 for the relation between area and linear
size. This value agrees very well with the dimensionDf
= 1.56 which is found in percolation theory for clusters of tracers
placed randomly on a lattice with a tracer density below a critical
threshold. The distribution of observed cluster areas also agrees
with that of clusters on such a random lattice. The correspondence
between properties of observations and of clusters on randomly filled
lattices suggests that- well after emergence - the magnetic flux on
the Sun is randomly distributed at least up to sizes of about 3″
and possibly larger.
Title: Observations of High Frequency and High Wavenumber Solar
Oscillations
Authors: Fernandes, D.; Scherrer, P.; Tarbell, T.; Title, A.
Bibcode: 1993ASPC...42..101F
Altcode: 1993gong.conf..101F
No abstract at ADS
Title: High Resolution Magnetic Field Measurements in the Sunspot
Photosphere (Invited)
Authors: Hofmann, A.; Schmidt, W.; Balthasar, H.; Tarbell, T. T.;
Frank, Z. A.
Bibcode: 1993ASPC...46...11H
Altcode: 1993IAUCo.141...11H; 1993mvfs.conf...11H
No abstract at ADS
Title: Subsurface Transverse Flows Near an Active Region
Authors: Milford, P. N.; Hill, F.; Tarbell, T. D.
Bibcode: 1993ASPC...42...85M
Altcode: 1993gong.conf...85M
No abstract at ADS
Title: White-light movies of the solar photosphere from the SOUP
instrument on Spacelab 2 (Advances in Space Research 1986)
Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.;
Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren,
R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka,
K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L.
Bibcode: 1993inas.book..100T
Altcode:
No abstract at ADS
Title: The solar oscillations investigation - Michelson Doppler
Imager.
Authors: Hoeksema, J. Todd; Scherrer, P. H.; Bush, R. I.; Title, A.;
Tarbell, T.
Bibcode: 1992ESASP.348....9H
Altcode: 1992cscl.work....9H
The Solar Oscillations Investigation (SOI) has developed the Michelson
Doppler Imager (MDI) to investigate the properties of solar interior
using the tools of helioseismology and of the photosphere and
corona using more conventional techniques. A fundamental goal is
to understand the Sun by determining its structure and observing its
dynamics. The basic observables, velocity, intensity and magnetic field,
are computed on board from up to twenty 1024 by 1024 filtergrams made
each minute. Subsequent analysis will extend the region one can explore
downward into the solar interior and upward into the corona. While
the instrument is dedicated to producing an uninterrupted series
of helioseismology data, several magnetograms will be made each day
and special 8-hour campaigns are being developed to address specific
scientific questions, some in coordination with other SOHO instruments.
Title: Polarimetry and spectroscopy of a simple sunspot. I - On the
magnetic field of a sunspot penumbra
Authors: Schmidt, W.; Hofmann, A.; Balthasar, H.; Tarbell, T. D.;
Frank, Z. A.
Bibcode: 1992A&A...264L..27S
Altcode:
We investigate the magnetic field structure of a medium sized sunspot
using high resolution magnetograms and spectrograms and derive a
relationship between the brightness of penumbral structures and the
inclination of the magnetic field. The field inclination to the spot
normal is larger in the dark structures than in the bright ones. We
show that the field strength does not vary between dark and bright
structures. At the inner penumbral boundary the field strength is 2000
Gauss and about 1000 Gauss at the outer penumbral edge. The line-of
sight component of the material flow decreases rapidly within one
arcsecond at the photospheric boundary of the spot.
Title: Properties of the Smallest Solar Magnetic Elements. I. Facular
Contrast near Sun Center
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1992ApJ...396..351T
Altcode:
Measurements are presented which indicate that the continuum intensity
of facular areas in solar active regions, outside sunspots and pores, is
less than that of the quiet sun very near disk center. It is shown that
the observed continuum intensity of faculae at disk center near 5000
A is nearly 3 percent less than that of the quiet sun. The continuum
contrast increases rapidly away from disk center, reaching +2 percent
at 45 deg. The zero-crossing point, where the contrast changes sign,
occurs at 20-degree heliocentric angle. This is contrary to many earlier
observations. The constraint these observations place on the size
of flux tubes depends upon the value of the zero-crossing point. It
is proposed that most of the flux tubes in solar faculae may be very
small, in the range 50-100 km in diameter, and that inclination from
local vertical of about 10 deg at the photosphere is common on the
sun. Footpoints of opposite polarity tend to tilt toward one another.
Title: From Filtergrams to Physical Atmospheric Magnitudes: A
Prospective Diagnostic
Authors: del Toro Iniesta, J. C.; Tarbell, T.; Ruiz Cobo, B.
Bibcode: 1992AAS...181.8115D
Altcode: 1992BAAS...24.1255D
No abstract at ADS
Title: A solar magnetic and velocity field measurement system for
Spacelab 2: The solar optical universal polarimeter (SOUP)
Authors: Tarbell, Theodore D.; Title, Alan M.
Bibcode: 1992lock.reptS....T
Altcode:
The Solar Optical Universal Polarimeter flew on the Shuttle Mission
Spacelab 2 (STS-51F) in August, 1985, and collected historic solar
observations. SOUP is the only solar telescope on either a spacecraft
or balloon which has delivered long sequences of diffraction-limited
images. These movies led to several discoveries about the solar
atmosphere which were published in the scientific journals. After
Spacelab 2, reflights were planned on the Space Shuttle Sunlab
Mission, which was cancelled after the Challenger disaster, and on
balloon flights, which were also cancelled for funding reasons. In
the meantime, the instrument was used in a productive program of
ground-based observing, which collected excellent scientific data
and served as instrument tests. This report gives an overview of
the history of the SOUP program, the scientific discoveries, and the
instrument design and performance.
Title: A solar magnetic and velocity field measurement system for
Spacelab 2: The Solar Optical Universal Polarimeter (SOUP)
Authors: Tarbell, Theodore D.; Title, Alan M.
Bibcode: 1992lock.reptR....T
Altcode:
The Solar Optical Universal Polarimeter (SOUP) flew on the shuttle
mission Spacelab 2 (STS-51F) in August, 1985, and collected
historic solar observations. SOUP is the only solar telescope on
either a spacecraft or balloon which has delivered long sequences of
diffraction-limited images. These movies led to several discoveries
about the solar atmosphere which were published in the scientific
journals. After Spacelab 2, reflights were planned on the shuttle Sunlab
mission, which was cancelled after the Challenger disaster, and on a
balloon flights, which were also cancelled for funding reasons. In
the meantime, the instrument was used in a productive program of
ground-based observing, which collected excellent scientific data and
served as instrument tests. Given here is an overview of the history
of the SOUP program, the scientific discoveries, and the instrument
design and performance.
Title: On the Differences between Plage and Quiet Sun in the Solar
Photosphere
Authors: Title, Alan M.; Topka, Kenneth P.; Tarbell, Theodore D.;
Schmidt, Wolfgang; Balke, Christiaan; Scharmer, Goran
Bibcode: 1992ApJ...393..782T
Altcode:
Time sequences of interleaved observations of the continuum intensity,
longitudinal magnetic field, vertical velocity in the midphotosphere,
and the line-center intensity in Ni I 6768 A were obtained in an
active-region plage and the surrounding relatively field-free area near
disk center. Spacetime Fourier filtering techniques are used to separate
the convective and oscillatory components of the solar atmosphere. The
properties of the photosphere are found to differ qualitatively and
quantitatively between the plage, where the field is 150 G or more,
and its quiet surroundings. The scale of granulation is smaller, the
contrast lower, and the temporal evolution slower in the plage than the
quiet sun. In the plage, the vertical velocity is reduced in amplitude
compared to the quiet sun, and there is little evidence of a granulation
pattern, while in the quiet sun the vertical flow pattern is similar in
size and shape to the underlying granulation pattern in the continuum.
Title: Observations of High-Frequency and High-Wavenumber Solar
Oscillations
Authors: Fernandes, D. N.; Scherrer, P. H.; Tarbell, T. D.; Title,
A. M.
Bibcode: 1992ApJ...392..736F
Altcode:
Doppler shift measurements of the Na D1 absorption line reveal solar
oscillations in a new regime of frequency and wavenumber. Oscillations
of vertical velocities in the temperature minimum and low chromosphere
of the sun are observed with frequencies ranging up to 9.5 mHz. The
fundamental modes appear with wavenumbers up to 5.33/Mm (equivalent
spherical harmonic degree 3710). No evidence for chromospheric modes
of 3-minute period is reported.
Title: Facular Contrast Near Solar Disk Center and the Inclination
of Magnetic Lines of Force from Local Vertical
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1992AAS...180.4004T
Altcode: 1992BAAS...24..793T
No abstract at ADS
Title: The Solar Oscillation Imager-Michelson Doppler Imager for SoHO
Authors: Title, A.; Tarbell, T.; Wolfson, J.; Scherrer, P.; Bush,
R.; Hoeksema, T.
Bibcode: 1992AAS...180.0606T
Altcode: 1992BAAS...24Q.737T
No abstract at ADS
Title: Optical Components of the Solar Oscillations Imager-Michelson
Doppler Imager
Authors: Tarbell, T.; Rosenberg, W.; Pope, T.; Huff, L.; Torgerson,
D.; Title, A.; Wolfson, J.; Scherrer, P.; Bush, R.; Hoeksema, T.
Bibcode: 1992AAS...180.0607T
Altcode: 1992BAAS...24R.737T
No abstract at ADS
Title: High resolution observations: the state of the art and beyond.
Authors: Title, A.; Tarbell, T.; Shine, R.; Topka, K.; Frank, Z.
Bibcode: 1992ESASP.344....9T
Altcode: 1992spai.rept....9T
Excellent telescopes on excellent sites with fast digital CCD cameras
and special purpose computers allow the collection of broad band images
at just the instants of good seeing. This has resulted in nearly optimal
movies of the solar surface for several hours. When longer exposures
are required for narrowband filtergrams or spectra it is not enough to
capture single images. However, big fast memories allow the collection
of many selected low signal-to-noise ratio images in real time, which
can be summed to achieve the desired signal to noise ratios. Adaptive
optics shows promise of diffraction limited images for limited fields
of view. Nevertheless, groundbased observations will always be limited
in their duration, uniformity, and resolution qualities which are
essential for understanding the development and evolution of small scale
processes. Until there are observations in space we will not be able
to completely understand either the processes in the solar atmosphere
or how processes occurring at different height are interrelated.
Title: SOI-MDI Onboard Real Time Data Reduction - Requirements
and Design.
Authors: Milford, P.; Lindgren, R.; Tarbell, T.; Bacon, L.; Scherrer,
P.
Bibcode: 1992AAS...180.0608M
Altcode: 1992BAAS...24..737M
SOI-MDI is a space-based high-resolution helioseismology experiment. To
observe Solar oscillations accurately requires a long time base of
(nearly) continuous observations. Due to telemetry restrictions,
SOI-MDI must carry out onboard data reduction of the high-resolution
observations prior to sending the data to the ground. This paper
summarizes the reduction requirements and discusses the hardware and
software design of the processor built to meet these requirements. The
main computational requirement to be met is the one-minute observing
cadence, required to observe a solar signal with a Nyquist frequency
corresponding to a 2-minute period. The analysis requires computing
dopplergrams from the observed filtergrams and a partial spherical
harmonic decomposition of the full disk dopplergrams. A custom image
processor was designed to meet these specifications. Other requirements
include low power, radiation tolerance and light weight. A design based
on an ASIC, designed around the 2903 bitslice family of processors,
has been developed to meet these requirements. The CPU includes three
memory busses with simultaneous DMA transfers to main memory and a
one-cycle 16 bit multiplier. Simultaneous access to the main memory by
the CCD Camera, via a DMA memory adder (also implemented as an ASIC),
and by the telemetry subsystem give the system sufficient performance
to handle the 30 Mb/minute of input data. This work was supported by
NASA Contract NAS5-30386 and Stanford Contract PR-6209.
Title: Investigation of solar active regions at high resolution
by balloon flights of the solar optical universal polarimeter,
definition phase
Authors: Tarbell, Theodore D.; Topka, Kenneth P.
Bibcode: 1992lock.reptQ....T
Altcode:
The definition phase of a scientific study of active regions on the sun
by balloon flight of a former Spacelab instrument, the Solar Optical
Universal Polarimeter (SOUP) is described. SOUP is an optical telescope
with image stabilization, tunable filter and various cameras. After
the flight phase of the program was cancelled due to budgetary
problems, scientific and engineering studies relevant to future balloon
experiments of this type were completed. High resolution observations
of the sun were obtained using SOUP components at the Swedish Solar
Observatory in the Canary Islands. These were analyzed and published
in studies of solar magnetic fields and active regions. In addition,
testing of low-voltage piezoelectric transducers was performed,
which showed they were appropriate for use in image stabilization on
a balloon.
Title: Patterns in the photospheric magnetic field and percolation
theory
Authors: Schrijver, C. J.; Zwaan, C.; Balke, A. C.; Tarbell, T. D.;
Lawrence, J. K.
Bibcode: 1992A&A...253L...1S
Altcode:
The magnetic field in solar plages forms a highly structured pattern
with no apparent characteristic length scale. This pattern appears
to be a fractal with a dimension between 1.45 and 1.60. Small-scale
displacements of concentrations of magnetic flux in the network
are consistent with a random walk on a fractal with a similar
dimension. Percolation theory offers an effective explanation for
observed geometric properties of small-scale flux concentrations
in the solar photosphere, by demonstrating the close correspondence
with clusters formed by randomly placed tracers on a 2D (irregular)
lattice. Percolation theory also offers a model for the subdiffusive
behavior of tracers performing a random walk on clusters formed
by bonded sites. The geometry of flux concentrations and of the
displacement of magnetic flux as a function of time are equivalent
to situations in percolation theory below a critical value, called
'the percolation threshold'.
Title: Observations of high frequency and high wavenumber solar
oscillations
Authors: Fernandes, D. N.; Scherrer, P. H.; Tarbell, T. D.; Title,
A. M.
Bibcode: 1992STIN...9232488F
Altcode:
Doppler shift measurements of the Na D1 absorption line
have revealed solar oscillations in a new regime of frequency and
wavenumber. Oscillations of vertical velocities in the temperature
minimum and low chromosphere of the Sun are observed with frequencies
ranging up to 9.5 mHz. The fundamental modes appear with wavenumbers
up to 5.33 M/m (equivalent spherical harmonic degree, 3710). We find
no evidence for chromospheric modes of a 3-minute period.
Title: High Resolution Observations of the Magnetic and Velocity
Field of Simple Sunspots
Authors: Title, Alan M.; Frank, Zoe A.; Shine, Richard A.; Tarbell,
T. D.; Topka, K. P.; Scharmer, Goran; Schmidt, Wolfgang
Bibcode: 1992ASIC..375..195T
Altcode: 1992sto..work..195T
We have observed the disk passage of relatively simple round sunspots
using a narrowband filter and a large format CCD detector and have
created magnetograms, Dopplergrams, and continuum images nearly
simultaneously. In addition the spectral resolution of the filter
allows the construction of 'spectra' for all points in the field of
view. The mean inclination of the magnetic field increases from 45-50
deg to 70-75 deg across the penumbra and there is a fluctuation of the
inclination angle about the mean of about 4 +/- 18 deg. The variation in
inclination is large enough that substantial amounts of magnetic field
are parallel to the solar surface from the mid to outer penumbra. The
Evershed flow tends to occur in the regions where the magnetic field
is horizontal. This suggests that the Evershed flow is confined to the
regions of horizontal fields. We show that a simple sunspot model with
azimuthal variations in inclination but no azimuthal variations of
field strength is free from azimuthal Lorentz forces. The meridional
component of the currents which arise from the azimuthal variation
in inclination are parallel to the field lines. This suggests that a
cylindrically symmetric magnetostatic sunspot model can be perturbed
into one with azimuthal variations in inclination with some adjustment
in the meridional force balance.
Title: Fractals in Magnetograms
Authors: Schrijver, C. J.; Zwaan, C.; Balke, A. C.; Tarbell, T. D.;
Lawrence, J. K.
Bibcode: 1992ASPC...27...67S
Altcode: 1992socy.work...67S
No abstract at ADS
Title: On the magnetic field of a sunspot penumbra.
Authors: Balthasar, H.; Schmidt, W.; Hofmann, A.; Tarbell, T. D.;
Frank, Z. A.
Bibcode: 1992AGAb....7..153B
Altcode:
No abstract at ADS
Title: Results from a Recent Observing Run with the Lockheed Solar
Adaptive Optics System
Authors: Acton, D. S.; Tarbell, T. D.; Dunn, R. B.
Bibcode: 1991BAAS...23.1453A
Altcode:
No abstract at ADS
Title: Low-Cost Space Missions in Solar Physics or Astrophysics
Using Mass-Produced Spacecraft
Authors: Tarbell, T. D.; Jurcevich, B. K.; Title, A. M.; Topka, K. P.
Bibcode: 1991BAAS...23.1317T
Altcode:
No abstract at ADS
Title: Properties of the Smallest Magnetic Elements on the Sun
Authors: Topka, K. P.; Smith, K. L.; Tarbell, T. D.; Title, A. M.;
Scharmer, G.
Bibcode: 1991BAAS...23.1388T
Altcode:
No abstract at ADS
Title: Power Spectra of Flows and Magnetic Fields in the Solar
Photosphere
Authors: Tarbell, T. D.; Slater, G. L.; Frank, Z. A.; Topka, K. P.;
Scharmer, G.; Schmidt, W.
Bibcode: 1991BAAS...23.1048T
Altcode:
No abstract at ADS
Title: Field Geometry of Sunspots Inferred from Inclination Effects
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.
Bibcode: 1991BAAS...23R1052T
Altcode:
No abstract at ADS
Title: Sunspot Umbral and Penumbral Oscillations in Hα
Authors: Shine, R.; Tarbell, T.; Title, A.; Topka, K.; Frank, Z.;
Smith, K.
Bibcode: 1991BAAS...23.1033S
Altcode:
No abstract at ADS
Title: 1024 x 1024 CCD Cameras under Development and Operation at
Lockheed PARL
Authors: Zayer, I.; Duncan, D.; Edwards, C.; Kelly, G.; Levay, M.;
Morrill, M.; Title, A.; Tarbell, T.; Wolfson, J.; Rosenberg, W.
Bibcode: 1991BAAS...23.1056Z
Altcode:
No abstract at ADS
Title: Stokes Polarimetry of a Sunspot from the Swedish Solar
Observatory at La Palma
Authors: Topka, K. P.; Frank, Z. A.; Tarbell, T. D.; Title, A. M.;
Scharmer, G.
Bibcode: 1991BAAS...23Q1052T
Altcode:
No abstract at ADS
Title: Fractal Flux Tubes of the Solar Magnetic Field
Authors: Ruzmaikin, Alexander; Sokoloff, Dmitry; Tarbell, Theodore
Bibcode: 1991LNP...380..140R
Altcode: 1991IAUCo.130..140R; 1991sacs.coll..140R
The small-scale solar magnetic field exceeding a given threshold forms
a fractal set. A dimension of this fractal is found from magnetograms
with varying linear resolution. The dimension depends on the value
of the threshold magnetic field (multifractality). A simple dynamo
model explaining the origin of the fractal magnetic structure is
considered. The dynamo produces a magnetic field in the form of
flux tubes with a fractal distribution of magnetic field across the
tube. The observed dimension gives a possibility of estimating a degree
of structuredness of the solar velocity field.
Title: Variation of granulation properties on a mesogranular scale
Authors: Brandt, P. N.; Ferguson, S.; Shine, R. A.; Tarbell, T. D.;
Scharmer, G. B.
Bibcode: 1991A&A...241..219B
Altcode:
A 79 min series of CCD images of the solar granulation with subarcsec
spatial resolution is analyzed. Local correlation techniques are applied
to determine horizontal displacements of the granular intensity pattern
in a 14.2 by 12.2 sq arcsec field of view. The divergence of the average
horizontal flow field shows mean cell sizes of 5 to 7 arcsec. Granules
are selected with respect to area, brightness, lifetime, and expansion
rate. It is shown that small, faint, short-lived, and fast collapsing
granules are located preferentially in the negative divergence
(down-draft) regions of the mesogranular flow field, while bright,
long-lived, and rapidly expanding granules populate preferentially
the positive divergence (up-draft) regions. The differences in area
coverage range between + or - 6 percent and + or - 9 percent.
Title: Results from high resolution solar images and spectra obtained
at the Pic du Midi Observatory (1986-1990)
Authors: Roudier, Th.; Muller, R.; Vigneau, J.; Auffret, H.; Espagnet,
O.; Simon, G. W.; Title, A. M.; Frank, Z.; Shine, R. A.; Tarbell,
T. D.; Mein, P.; Malherbe, J. M.
Bibcode: 1991AdSpR..11e.205R
Altcode: 1991AdSpR..11..205R
We present an overview of our recent results about solar granulation and
mesogranulation, obtained with Pic du Midi observations. These results
were obtained during 1986-1990 using image and spectrographic analysis
of high spatial resolution data. The study of the solar granulation,
with 2 Dim. ``Multichannel Subtractive Double Pass'' (M.S.D.P.) spectra,
shows a clear change of the dynamical regime at 3'' (⋍ 2200 km)
of the photospheric velocity field when oscillatory components are
filtered out. A three hour movie obtained on film at Pic du Midi
Observatory and analyzed at the Lockheed Research Laboratory and the
National Solar Observatory (Sacramento Peak) was used to calculate
the horizontal flow pattern. The mean lifetime of the diverging areas
related to mesogranulation is estimated at 3 hours; these diverging
areas are swept by the supergranulation flow towards the supergranule
boundary with a mean speed of 0.4 km/s.
Title: Generation of Electric Currents and Waves on Magnetic Flux
Tubes by Horizontal Velocities in the Photosphere (With 1 Figure)
Authors: Tarbell, T. D.; Slater, G. L.; Frank, Z. A.; Shine, R. A.;
Topka, K. P.
Bibcode: 1991mcch.conf...39T
Altcode:
No abstract at ADS
Title: SOUP Observations of Solar Activity
Authors: Shine, R. A.; Scharmer, G.; Tarbell, T. D.; Title, A. M.;
Topka, K. P.
Bibcode: 1991max..conf..295S
Altcode:
No abstract at ADS
Title: Solar magnetic field strength determinations from high spatial
resolution filtergrams
Authors: Keller, C. U.; Stenflo, J. O.; Solanki, S. K.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1990A&A...236..250K
Altcode:
Circularly polarized images with high spatial resolution (better than 1
arcsec) of a solar active region, obtained with a tunable filter in the
wings of Fe I 5247.1 A and Fe I 5250.2 A, have been analyzed in terms of
the magnetic line ratio technique introduced by Stenflo (1973). Whenever
a measurable amount of polarization is present, the distribution of
the observed magnetic-line ratio is compatible with a unique value,
which is randomly blurred by noise due to the photon statistics,
the CCD camera, and atmospheric distortions. There is no need for a
distribution of field strengths to explain the observed distribution of
the magnetic line ratio. Consequently, the observations are compatible
with a unique magnetic field strength in solar small-scale magnetic
elements of about 1000 G at the level of line formation. For a thin
flux tube, this corresponds to a field strength of approximately 2000
G at the level of continuum formation, which is in excellent agreement
with previous field strength determinations from low spatial resolution
spectra (4-10 arcsec).
Title: Detailed Comparison of Quiet and Magnetic Sun
Authors: Topka, K.; Ferguson, S.; Shine, R.; Tarbell, T.; Title, A.;
Balke, C.; Scharmer, G.; Schmidt, W.
Bibcode: 1990BAAS...22R.879T
Altcode:
No abstract at ADS
Title: Penumbral Flows and Magnetic Fields
Authors: Shine, R.; Smith, K.; Tarbell, T.; Title, A.; Scharmer, G.
Bibcode: 1990BAAS...22..878S
Altcode:
No abstract at ADS
Title: Intermittency of Fine Scale Solar Magnetic Fields in the
Photosphere
Authors: Tarbell, T.; Acton, S.; Topka, K.; Title, A.; Schmidt, W.;
Scharmer, G.
Bibcode: 1990BAAS...22..878T
Altcode:
No abstract at ADS
Title: Generation of Waves and Electric Currents on Magnetic Flux
Tubes by Horizontal and Vertical Velocities in the Photosphere
Authors: Frank, Z. A.; Shine, R. A.; Slater, G.; Tarbell, T.; Topka, K.
Bibcode: 1990BAAS...22..878F
Altcode:
No abstract at ADS
Title: Magnetic flux tubes and their relation to continuum and
photospheric features
Authors: Title, A.; Tarbell, T.; Topka, K.; Cauffman, D.; Balke, C.;
Scharmer, G.
Bibcode: 1990GMS....58..171T
Altcode:
An investigation is made of the relationship between photospheric
'filigree' light points, line-center brightness, and magnetic field,
as inferred from sets of individual images and films showing a distinct
difference between two classes of magnetic regions. While in the first
such region the vertical velocity field is average and the magnetic
field is mostly confined in narrow lanes, the granulation pattern
of the second scale is much smaller, the vertical velocity is lower,
and the magnetic field is less compact. Where granulation is normal,
excellent correlation is obtained between bright continuum, line-center,
and magnetic field line structure.
Title: High-Resolution Observations of Emerging Magnetic Fields and
Flux Tubes in Active Region Photosphere
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Shine, R.; Title, A.;
Topka, K.; Scharmer, G.
Bibcode: 1990IAUS..138..147T
Altcode:
No abstract at ADS
Title: Structure and Evolution of the Large Scale Granulation
Authors: Muller, R.; Roudier, Th.; Vigneau, J.; Frank, Z.; Shine,
R.; Tarbell, T.; Title, A.; Simon, G.
Bibcode: 1990PDHO....7...44M
Altcode: 1990dysu.conf...44M; 1990ESPM....6...44M
A granulation movie of 3 hours has been performed at the Pic du Midi
Observatory on September 20, 1988.
Title: High Resolution Observations of the Photosphere
Authors: Title, A. M.; Shine, R. A.; Tarbell, T. D.; Topka, K. P.;
Scharmer, G. B.
Bibcode: 1990IAUS..138...49T
Altcode:
No abstract at ADS
Title: Formation of Network Bright Points by Granule Compression
Authors: Muller, R.; Roudier, Th.; Vigneau, J.; Frank, Z.; Shine,
R.; Tarbell, T.; Title, A.; Simon, G.
Bibcode: 1990PDHO....7..150M
Altcode: 1990dysu.conf..150M; 1990ESPM....6..150M
No abstract at ADS
Title: Intial Results of the Lockheed 1989 La Palma Observing Campaign
Authors: Topka, K.; Frank, Z.; Shine, R.; Smith, K.; Tarbell, T.;
Title, A.; Scharmer, G.
Bibcode: 1989BAAS...21.1111T
Altcode:
No abstract at ADS
Title: High - resolution observations of emerging magnetic flux
Authors: Tarbell, T. D.; Topka, K.; Ferguson, S.; Frank, Z.; Title,
A. M.
Bibcode: 1989hsrs.conf..506T
Altcode:
No abstract at ADS
Title: Variation of granulation properties on a meso-granular scale
Authors: Brandt, P. N.; Ferguson, S.; Scharmer, G. B.; Shine, R. A.;
Tarbell, T. D.; Title, A. M.; Topka, K.
Bibcode: 1989hsrs.conf..473B
Altcode:
No abstract at ADS
Title: Proper Motion and Lifetime of Mesogranules
Authors: Frank, Z.; Muller, R.; Roudier, T.; Vigneau, J.; Shine, R.;
Tarbell, T.; Title, A.; Topka, K.; Simon, G.
Bibcode: 1989BAAS...21..841F
Altcode:
No abstract at ADS
Title: Short Term Evolution of Fine Scale Magnetic Structures
Authors: Topka, K.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.;
Scharmer, G.; Balke, A.
Bibcode: 1989BAAS...21..842T
Altcode:
No abstract at ADS
Title: Magnetic Field Inclination in Penumbra of a Round Sunspot
Observed at Very High Spatial Resolution
Authors: Title, A. M.; Frank, Z. A.; Shine, R. A.; Tarbell, T. D.;
Scharmer, G.
Bibcode: 1989BAAS...21Q.837T
Altcode:
No abstract at ADS
Title: Investigation of Active Regions at High Resolution by Balloon
Flights of the Solar Optical Universal Polarimeter (SOUP)
Authors: Tarbell, T.; Gilbreth, C.; Shine, R.; Title, A.; Topka, K.;
Wolfson, J.
Bibcode: 1989BAAS...21R.837T
Altcode:
No abstract at ADS
Title: Observations of Running Penumbral Waves
Authors: Shine, R.; Tarbell, T.; Title, A.; Topka, K.; Frank, Z.;
Scharmer, G.
Bibcode: 1989BAAS...21..837S
Altcode:
No abstract at ADS
Title: Generation of Waves on Magnetic Flux Tubes by Horizontal
Velocities in the Photosphere
Authors: Tarbell, T. D.; Ferguson, S. H.; Frank, Z. A.; Shine, R. A.
Bibcode: 1989BAAS...21..830T
Altcode:
No abstract at ADS
Title: Ground-Based Tunable Filter Observations
Authors: Title, A. M.; Tarbell, T. D.; Wolfson, C. J.
Bibcode: 1989ASIC..263...25T
Altcode: 1989ssg..conf...25T
No abstract at ADS
Title: Details of Large Scale Solar Motions Revealed by Granulation
Test Particles
Authors: Simon, G. W.; November, L. J.; Ferguson, S. H.; Shine, R. A.;
Tarbell, T. D.; Title, A. M.; Topka, K. P.; Zirin, H.
Bibcode: 1989ASIC..263..371S
Altcode: 1989ssg..conf..371S
No abstract at ADS
Title: Statistical Properties of Solar Granulation Derived from the
SOUP Instrument on Spacelab 2
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.; Ferguson, S. H.;
Shine, R. A.; SOUP Team
Bibcode: 1989ApJ...336..475T
Altcode:
Computer algorithms and statistical techniques were used to identify,
measure, and quantify the properties of solar granulation derived
from movies collected by the Solar Optical Universal Polarimeter on
Spacelab 2. The results show that there is neither a typical solar
granule nor a typical granule evolution. A granule's evolution is
dependent on local magnetic flux density, its position with respect to
the active region plage, its position in the mesogranulation pattern,
and the evolution of granules in its immediate neighborhood.
Title: Optical disk processing of solar images.
Authors: Title, A.; Tarbell, T.
Bibcode: 1989GMS....54...31T
Altcode: 1989sspp.conf...31T
The current generation of space and ground-based experiments in solar
physics produces many megabyte-sized image data arrays. Optical
disk technology is the leading candidate for convenient analysis,
distribution, and archiving of these data. The authors have been
developing data analysis procedures which use both analog and digital
optical disks for the study of solar phenomena.
Title: Flows, Random Motions and Oscillations in Solar Granulation
Derived from the SOUP Instrument on Spacelab 2
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.; Ferguson, S. H.;
Shine, R. A.; SOUP Team
Bibcode: 1989ASIC..263..225T
Altcode: 1989ssg..conf..225T
No abstract at ADS
Title: Magnetoconvection on the solar surface.
Authors: Simon, G. W.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Shine, R. A.; Ferguson, S. H.; Zirin, H.
Bibcode: 1989GMS....54...53S
Altcode: 1989sspp.conf...53S
The authors describe and illustrate the first high-resolution
observations of horizontal flows on the solar surface and their relation
to magnetic field structure seen in the Sun's photosphere.
Title: Vortex Motion of the Solar Granulation
Authors: Brandt, P. N.; Scharmer, G. B.; Ferguson, S. H.; Shine,
R. A.; Tarbell, T. D.; Title, A. M.
Bibcode: 1989ASIC..263..305B
Altcode: 1989ssg..conf..305B
No abstract at ADS
Title: Investigation of active regions at high resolution by balloon
flights of the Solar Optical Universal Polarimeter (SOUP)
Authors: Tarbell, T.; Frank, Z.; Gilbreth, C.; Shine, R.; Title, A.;
Topka, K.; Wolfson, J.
Bibcode: 1989dots.work..310T
Altcode:
SOUP is a versatile, visible-light solar observatory, built for space
or balloon flight. It is designed to study magnetic and velocity
fields in the solar atmosphere with high spatial resolution and
temporal uniformity, which cannot be achieved from the surface of the
earth. The SOUP investigation is carried out by the Lockheed Palo Alto
Research Laboratory, under contract to NASA's Marshall Space Flight
Center. Co-investigators include staff members at a dozen observatories
and universities in the U.S. and Europe. The primary objectives of the
SOUP experiment are: to measure vector magnetic and velocity fields in
the solar atmosphere with much better spatial resolution than can be
achieved from the ground; to study the physical processes that store
magnetic energy in active regions and the conditions that trigger
its release; and to understand how magnetic flux emerges, evolves,
combines, and disappears on spatial scales of 400 to 100,000 km. SOUP
is designed to study intensity, magnetic, and velocity fields in the
photosphere and low chromosphere with 0.5 arcsec resolution, free of
atmospheric disturbances. The instrument includes: a 30 cm Cassegrain
telescope; an active mirror for image stabilization; broadband film
and TV cameras; a birefringent filter, tunable over 5100 to 6600 A
with 0.05 A bandpass; a 35 mm film camera and a digital CCD camera
behind the filter; and a high-speed digital image processor.
Title: The Michelson Doppler imager for the solar oscillations imager
program on SOHO.
Authors: Hoeksema, J. T.; Scherrer, Philip H.; Title, A. M.; Tarbell,
T. D.
Bibcode: 1988ESASP.286..407H
Altcode: 1988ssls.rept..407H
The Michelson Doppler Imager (MDI) will be the instrument used
in the Solar Oscillations Imager Program on SOHO. MDI will make a
line-of-sight velocity map of the full solar disk with 2 arc-second
pixels each minute. The instrument will be a modification of the
Fourier Tachometer and will operate by using narrow bandpass solar
images at four wavelengths to measure the line profile of the Ni
I line at 6768 Å. This method is relatively insensitive to line
profile changes and has a linear response to velocity. The instrument
is also capable of making partial maps with 0.7 arc-sec pixels. All
data will be transmitted to the ground for two continuous months
each year and 8 hours each day (160 kilobits/sec). At all times the
on-board computer will compute and transmit a selection of modes
(5 kilobits/sec) to take full advantage of the advantages of a space
based telescope. Line-of-sight magnetic fields will also be measured
regularly. The flight instrument will be built by the Lockheed Palo
Alto Research Laboratory.
Title: Observations of f- and p-mode oscillations of high degree
(500 < l < 2500) in quiet and active Sun.
Authors: Tarbell, T. D.; Peri, M.; Frank, Z.; Shine, R.; Title, A. M.
Bibcode: 1988ESASP.286..315T
Altcode: 1988ssls.rept..315T
Spectra (l-ν diagrams) from high resolution observations taken at
the Vacuum Tower Telescope (NSO/Sunspot) are presented. The raw data
are CCD images taken through the SOUP narrowband filter in Fe I 5576
Å. Four filtergrams spaced through the spectral line are combined to
form velocity movies. Spectra for 80 minutes of data with 0.5 - 1.5
arcsecond resolution are presented for the entire field-of-view and
for quiet and magnetic (plage) subregions. Ridges f and p1 -
p5 are evident in velocity spectra, extending to l = 2500(f),
l = 1800(p1), and l = 1200(p2). Much less power is
seen in the magnetic region than in the quiet sun. Three-dimensional
Fourier filtering shows that oscillation velocity amplitude drops
sharply at the boundary of the active region for each family of modes
considered.
Title: SOI: The Solar Oscillations Imager on SOHO
Authors: Scherrer, P. H.; Hoeksema, J. T.; Bogart, R. S.; Walker,
A. B. C., Jr.; Title, A. M.; Tarbell, T. D.; Wolfson, C. J.; Brown,
T. M., Jr.; Christensen-Dalsgaard, J.; Gough, D. O.
Bibcode: 1988sohi.rept...25S
Altcode:
The Solar Oscillations Imager (SOI) program for SOHO (solar and
heliospheric observatory) is described. It will consist of a Michelson
Doppler Imager (MDI) instrument, a facility providing data reduction
and analysis capability, and a coordinated set of investigations
designed to address a set of science objectives. The MDI is designed
to take advantage of the anticipated SOHO telemetry by organizing
the observations into four observation programs: structure (at all
times), dynamics (two months per year), campaign (eight hours per day,
ten months per year), and magnetic fields (few minutes per day). The
MDI will measure line-of-sight velocity by Doppler shift, transverse
velocity by local correlation tracking, line and continuum intensity,
and line-of-sight magnetic fields with both 4 and 1.4 arc-second
resolution (2 and 0.7 arc-sec pixels respectively).
Title: High-resolution digital movies of emerging flux and horizontal
flows in active regions on the sun
Authors: Topka, K.; Ferguson, S.; Frank, Z.; Tarbell, T.; Title, A.
Bibcode: 1988fnsm.work..283T
Altcode:
High-resolution observations of active regions in many wavelength bands
obtained at the Vacuum Tower Telescope of NSO/Sunspot (Sacramento Peak)
are presented. The SOUP tunable filter, HRSO 1024 x 1024 CCD camera,
and a sunspot tracker for image stabilization were used. Subarrays of
512 x 512 pixels were processed digitally and recorded on videodisk
in movie format. The movies with 0.5 to 1 arcsecond resolution of
the following simultaneous observations were shown: green continuum,
longitudinal magnetogram, Doppler velocity, Fe I 5576 A line center,
H alpha wings, and H alpha line center. The best set of movies show a
90 x 90 arcsecond field-of-view of an active region at S29, W11. When
viewed at speeds of a few thousand times real-time, the photospheric
movies clearly show the active region fields being distorted by a
remarkable combination of systematic flows and small eruptions of new
flux. Flux emergence is most easily discovered in line center movies:
an elongated dark feature appears first, followed soon after by bright
points at one or both ends. A brief, strong upflow is seen when the
dark feature first appears; downflow in the bright points persists
much longer. The magnetic flux appears to increase gradually over this
extended period. Some of the flux emergence events were studied in
detail, with measurements of horizontal and vertical velocities and
magnetic flux versus time within one footpoint of the loop.
Title: Statistical properties of solar granulation from the SOUP
instrument on Spacelab 2
Authors: Topka, K.; Title, A.; Tarbell, T.; Ferguson, S.; Shine, R.
Bibcode: 1988fnsm.work..294T
Altcode:
The Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 collected
movies of solar granulation completely free from atmospheric blurring,
and are not degraded by pointint jitter (the pointing stability
was 0.003 sec root mean square). The movies illustrate that the
solar five minute oscillation has a major role in the appearance of
solar granulation and that exploding granules are a common feature
of the granule evolution. Using 3-D Fourier filtering techniques
the oscillations were removed and it was demonstrated that the
autocorrelation lifetime of granulation is a factor of two greater
in magnetic field regions than in field-free quiet sun. Horizontal
velocities were measured and flow patterns were observed on the scale of
meso- and super granulation. In quiet regions the mean flow velocity
is 370 m/s while in the magnetic regions it is about 125 m/s. It
was also found that the root mean square (RMS) fluctuating horizonal
velocity field is substantially greater in quiet sun than in strong
magnetic field regions. By superimposing the location of exploding
granules on the average flow maps it was found that they appear almost
exclusively in the center of mesogranulation size flow cells. Because
of the nonuniformity of the distribution of exploding granules, the
evolution of the granulation pattern in mesogranule cell centers and
boundaries differs fundamentally. It is clear from this study there
is neither a typical granule nor a typical granule evolution.
Title: Observations of photospheric magnetic fields and shear flows
in flaring active regions
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
Bibcode: 1988fnsm.work...50T
Altcode:
Horizontal flows in the photosphere and subsurface convection zone move
the footpoints of coronal magnetic field lines. Magnetic energy to power
flares can be stored in the corona if the flows drive the fields far
from the potential configuration. Videodisk movies were shown with 0.5
to 1 arcsecond resolution of the following simultaneous observations:
green continuum, longitudinal magnetogram, Fe I 5576 A line center
(mid-photosphere), H alpha wings, and H alpha line center. The movies
show a 90 x 90 arcsecond field of view of an active region at S29,
W11. When viewed at speeds of a few thousand times real-time, the
photospheric movies clearly show the active region fields being
distorted by a remarkable combination of systematic flows and small
eruptions of new flux. Magnetic bipoles are emerging over a large area,
and the polarities are systematically flowing apart. The horizontal
flows were mapped in detail from the continuum movies, and these may
be used to predict the future evolution of the region. The horizontal
flows are not discernable in H alpha. The H alpha movies strongly
suggest reconnection processes in the fibrils joining opposite
polarities. When viewed in combination with the magnetic movies,
the cause for this evolution is apparent: opposite polarity fields
collide and partially cancel, and the fibrils reconnect above the
surface. This type of reconnection, driven by subphotospheric flows,
complicates the chromospheric and coronal fields, causing visible
braiding and twisting of the fibrils. Some of the transient emission
events in the fibrils and adjacent plage may also be related.
Title: Fractal Geometry of Convective Flows and Magnetic Fields in
the Solar Atmosphere
Authors: Tarbell, T.; Ferguson, S.; Title, A.; Scharmer, G.; Brandt, P.
Bibcode: 1988BAAS...20Q1010T
Altcode:
No abstract at ADS
Title: Observations of Granulation in Quiet and Magnetic Sun from
the Swedish Solar Observatory on LaPalma
Authors: Topka, K.; Ferguson, S.; Frank, Z.; Shine, R.; Tarbell, T.;
Title, A.; Wolfson, J.; Scharmer, G.; Brandt, P.
Bibcode: 1988BAAS...20S1010T
Altcode:
No abstract at ADS
Title: On the Feasibility of Correlation Tracking at Moderate
Resolution
Authors: Bogart, R. S.; Ferguson, S. H.; Scherrer, P. H.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1988SoPh..116..205B
Altcode:
The SOUP experiment demonstrated that photospheric surface flows can
be measured by correlation tracking of white-light intensity features
at high resolution (November et al., 1987). In order to assess
the feasibility of this technique with observations made at lower
resolution, we have applied it to the same SOUP data artificially
degraded, but still free of seeing distortion. Comparison with the
velocity structures inferred from the original data shows generally
good agreement when the resolution is better than about 2″. The
radial outflow from a sunspot penumbra, however, can only be seen with
resolution of better than 1″. With resolution of worse than 2″,
the inferred velocity fields rapidly lose coherence, while resolution of
better than 1″ yields little improvement. We conclude that apertures
as small as 10-14 cm on a space-based platform will be useful for the
measurement of large-scale horizontal motions.
Title: Solar Activity and Flare Observations from the Swedish Solar
Observatory on La Palma
Authors: Wolfson, J.; Ferguson, S.; Frank, Z.; Shine, R.; Tarbell,
T.; Title, A.; Topka, K.; Scharmer, G.; Brandt, P.; Gurman, J.
Bibcode: 1988BAAS...20..978W
Altcode:
No abstract at ADS
Title: Measurements of Turbulent Diffusion by Solar Granulation in
Quiet and Magnetic Areas
Authors: Title, A.; Ferguson, S.; Tarbell, T.; Scharmer, G.; Brandt, P.
Bibcode: 1988BAAS...20R1010T
Altcode:
No abstract at ADS
Title: Vortex flow in the solar photosphere
Authors: Brandt, P. N.; Scharmer, G. B.; Ferguson, S.; Shine, R. A.;
Tarbell, T. D.; Title, A. M.
Bibcode: 1988Natur.335..238B
Altcode:
Convective flow fields in the solar atmosphere play a key role in the
concentration and dispersal of magnetic flux1, but because
the individual flow elements-the solar granules-are a few arcsec or less
in size, studies of their motions have been limited by the distortion
and blurring of the Earth's atmosphere ('seeing'). We report here a
very high-quality series of granulation images taken at the new Swedish
Solar Observatory on La Palma (Canary Islands) which have permitted
flow measurements at the sub-arcsec level. These movies show a vortex
structure which visibly dominates the motion of the granules in its
neighbourhood and persists for the 1.5 h duration of the movie. If such
vortices are a common feature of the solar convective zone, they may
provide an important mechanism for the heating of stellar chromospheres
and coronae by twisting the footprints of magnetic flux tubes.
Title: On the Relation between Photospheric Flow Fields and the
Magnetic Field Distribution on the Solar Surface
Authors: Simon, George W.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Shine, R. A.; Ferguson, S. H.; Zirin, H.; SOUP Team
Bibcode: 1988ApJ...327..964S
Altcode:
Using the technique of local correlation tracking on a 28 minute time
sequence of white-light images of solar granulation, the horizontal
flow field on the solar surface is measured. The time series was
obtained by the Solar Optical Universal Polarimeter (SOUP) on Spacelab 2
(Space Shuttle flight 51-F) and is free from atmospheric blurring and
distortion. The SOUP flow fields have been compared with carefully
aligned magnetograms taken over a nine hour period at the Big Bear
Solar Observatory before, during, and after the SOUP images. The flow
field and the magnetic field agree in considerable detail: vectors which
define the flow of the white-light intensity pattern (granulation) point
toward magnetic field regions, magnetic fields surround flow cells, and
magnetic features move along the flow arrows. The projected locations
of free particles ('corks') in the measured flow field congregate at
the same locations where the magnetic field is observed.
Title: Observations of F-and P-Mode Oscillations of High Degree
(500< <3500) in Quiet and Active Sun
Authors: Peri, M.; Frank, Z.; Shine, R.; Tarbell, T.; Title, A.
Bibcode: 1988BAAS...20..702P
Altcode:
No abstract at ADS
Title: Convection and Magnetic Fields on the Sun
Authors: Tarbell, T.
Bibcode: 1988BAAS...20..723T
Altcode:
No abstract at ADS
Title: A New Technique for Measuring Solar Velocity
Authors: Scherrer, P. H.; Tarbell, T. D.
Bibcode: 1988BAAS...20..702S
Altcode:
No abstract at ADS
Title: Observations of Photospheric Magnetic Fields and Shear Flows
in Flaring Active Regions
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
Bibcode: 1988BAAS...20..744T
Altcode:
No abstract at ADS
Title: High-Resolution Digital Movies of Emerging Flux and Horizontal
Flows in Active Regions on the Sun
Authors: Tarbell, T.; Ferguson, S.; Frank, Z.; Title, A.; Topka, K.
Bibcode: 1988BAAS...20..680T
Altcode:
No abstract at ADS
Title: Solar Granulation Movies of Exceptional Spatial Resolution:
Observations and Simulations of Horizontal Convective Flows
Authors: Title, A.; Shine, R.; Ferguson, S.; Tarbell, T.; Brandt,
P.; Scharmer, G.
Bibcode: 1988BAAS...20R.679T
Altcode:
No abstract at ADS
Title: Statistical Properties of Solar Granulation from the SOUP
Instrument on Spacelab 2
Authors: Topka, K.; Title, A.; Tarbell, T.; Ferguson, S.; Shine, R.
Bibcode: 1988BAAS...20Q.679T
Altcode:
No abstract at ADS
Title: Variability of solar mesogranulation
Authors: Simon, G. W.; November, L. J.; Acton, L. W.; Ferguson, S. H.;
Shine, R. A.; Tarbell, T. D.; Title, A. M.; Topka, K. P.; Zirin, H.
Bibcode: 1988AdSpR...8g.169S
Altcode: 1988AdSpR...8..169S
From white-light photographs of solar granulation obtained with the
SOUP instrument on Space Shuttle Flight STS-19 we have measured the
motions of granules using local correlation tracking techniques. The
granules are organized into larger-scale structures (mesogranular and
supergranular) which exhibit outflow from upwellings, convergence into
sinks, as well as significant vorticity. Magnetic fields follow these
same flow patterns. We describe these velocity structures, and suggest
that their effect on magnetic field structures may be important to
the solar flare buildup process.
Title: Correlation Lifetimes of Quiet and Magnetic Granulation from
the SOUP Instrument on Spacelab 2
Authors: Title, A.; Tarbell, T.; Topka, K.; Acton, L.; Duncan, D.;
Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill,
M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Simon, G.; Harvey,
J.; Leibacher, J.; Livingston, W.; November, L.; Zirker, J.
Bibcode: 1988ApL&C..27..141T
Altcode:
The time sequences of diffraction limited granulation images obtained by
the Solar Optical Universal Polarimeter on Spacelab 2 are presented. The
uncorrection autocorrelation limetime in magnetic regions is dominated
by the 5-min oscillation. The removal of this oscillation causes the
autocorrelation lifetime to increase by more than a factor of 2. The
results suggest that a significant fraction of granule lifetimes are
terminated by nearby explosions. Horizontal displacements and transverse
velocities in the intensity field are measured. Lower limits to the
lifetime in the quiet and magnetic sun are set at 440 s and 950 s,
respectively.
Title: Max '91: Flare research at the next solar maximum
Authors: Dennis, Brian; Canfield, Richard; Bruner, Marilyn; Emslie,
Gordon; Hildner, Ernest; Hudson, Hugh; Hurford, Gordon; Lin, Robert;
Novick, Robert; Tarbell, Ted
Bibcode: 1988STIN...8814919D
Altcode:
To address the central scientific questions surrounding solar
flares, coordinated observations of electromagnetic radiation and
energetic particles must be made from spacecraft, balloons, rockets,
and ground-based observatories. A program to enhance capabilities
in these areas in preparation for the next solar maximum in 1991 is
recommended. The major scientific issues are described, and required
observations and coordination of observations and analyses are
detailed. A program plan and conceptual budgets are provided.
Title: The relation between convection flows and magnetic structure
at the solar surface
Authors: Simon, G. W.; November, L. J.; Acton, L. W.; Title, A. M.;
Tarbell, T. D.; Topka, K. P.; Shine, R. A.; Ferguson, S. H.; Weiss,
N. O.; Zirin, H.
Bibcode: 1988AdSpR...8k.133S
Altcode: 1988AdSpR...8..133S
We describe recent results from the comparison of data from the Solar
Optical Universal Polarimeter instrument on Spacelab 2 and magnetograms
from Big Bear Solar Observatory. We show that the Sun's surface velocity
field governs the structure of the observed magnetic field over the
entire solar surface outside sunspots and pores. We attempt to describe
the observed flows by a simple axisymmetric plume model. Finally,
we suggest that these observations may have important implications
for the prediction of solar flares, mass ejections, and coronal heating.
Title: White Light Sunspot Observations from the Solar Optical
Universal Polarimeter on Spacelab-2
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Topka, K. P.
Bibcode: 1987Sci...238.1264S
Altcode:
The flight of the Solar Optical Universal Polarimeter on Spacelab-2
provided the opportunity for the collection of time sequences of
diffraction-limited (0.5 arc second) solar images with excellent
pointing stability (0.003 arc second) and with freedom from the
distortion that plagues ground-based images. A series of white-light
images of active region 4682 were obtained on 5 August 1985, and
the area containing the sunspot has been analyzed. These data have
been digitally processed to remove noise and to separate waves from
low-velocity material motions. The results include (i) proper motion
measurements of a radial outflow in the photospheric granulation
pattern just outside the penumbra; (ii) discovery of occasional bright
structures (``streakers'') that appear to be ejected outward from the
penumbra; (iii) broad dark ``clouds'' moving outward in the penumbra,
in addition to the well-known bright penumbral grains moving inward;
(iv) apparent extensions and contractions of penumbral filaments over
the photosphere; and (v) observation of a faint bubble or looplike
structure that seems to expand from two bright penumbral filaments
into the photosphere.
Title: High-Resolution CCD Observations of Doppler and Magnetic
Images in the Solar Photosphere
Authors: Tarbell, T. D.; Frank, Z. A.; Morrill, M. E.; Shine, R. A.;
Topka, K. P.; Title, A. M.
Bibcode: 1987BAAS...19.1117T
Altcode:
No abstract at ADS
Title: Power Spectra of Solar Granulation
Authors: Acton, D. S.; Brandt, P.; Scharmer, G.; Dunn, D.; Tarbell,
T. D.; Title, A. M.; Smithson, R. C.
Bibcode: 1987BAAS...19.1118A
Altcode:
No abstract at ADS
Title: Sunspot observations from the SOUP instrument on Spacelab 2.
Authors: Shine, R. A.; Title, A. M.; Tarbell, T. D.; Acton, L.; Duncan,
D.; Ferguson, S. H.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.
Bibcode: 1987NASCP2483..133S
Altcode: 1987tphr.conf..133S
A series of white light images obtained by the SOUP instrument on
Spacelab 2 of active region 4682 on August 5, 1985 were analyzed
in the area containing sunspots. Although the umbra of the spot is
underexposed, the film is well exposed in the penumbral regions. These
data were digitally processed to remove noise and to separate p-mode
oscillations from low velocity material motions. The results of this
preliminary investigation include: (1) proper motion measurements of
a radial outflow in the photospheric granulation pattern just outside
the penumbra; (2) discovery of occasional bright structures (streakers)
that appear to be ejected outward from the penumbra; (3) broad dark
clouds moving outward in the penumbra in addition to the well known
bright penumbral grains moving inward; (4) apparent extensions and
contractions of penumbral filaments over the photosphere; and (5)
observation of a faint bubble or loop-like structure which seems to
expand from two bright penumbral filaments into the photosphere.
Title: Large-scale horizontal flows from SOUP observations of solar
granulation.
Authors: November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.;
Ferguson, S. H.
Bibcode: 1987NASCP2483..121N
Altcode: 1987tphr.conf..121N
Using high-resolution time-sequence photographs of solar granulation
from the SOUP experiment on Spacelab 2 the authors observed large-scale
horizontal flows in the solar surface. The measurement method is
based upon a local spatial cross correlation analysis. The horizontal
motions have amplitudes in the range 300 to 1000 m/s. Radial outflow of
granulation from a sunspot penumbra into the surrounding photosphere is
a striking new discovery. Both the supergranulation pattern and cellular
structures having the scale of mesogranulation are seen. The vertical
flows that are inferred by continuity of mass from these observed
horizontal flows have larger upflow amplitudes in cell centers than
downflow amplitudes at cell boundaries.
Title: First results on quiet and magnetic granulation from SOUP.
Authors: Title, A. M.; Tarbell, T. D.; Acton, L.; Duncan, D.; Ferguson,
S. H.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren, R.; Morrill, M.
Bibcode: 1987NASCP2483...55T
Altcode: 1987tphr.conf...55T
The flight of Solar Optical Universal Polarimeter (SOUP) on Spacelab
2 allowed the collection of time sequences of diffraction limited (0.5
arc sec) granulation images with excellent pointing (0.003 arc sec) and
completely free of the distortion that plagues groundbased images. The
p-mode oscillations are clearly seen in the data. Using Fourier
transforms in the temporal and spatial domain, it was shown that the
p-modes dominate the autocorrelation lifetime in magnetic regions. When
these oscillations are removed the autocorrelation lifetime is found
to be 500 sec in quiet and 950 sec in magnetic regions. In quiet
areas exploding granules are seen to be common. It is speculated that
a significant fraction of granule lifetimes are terminated by nearby
explosions. Using local correlation tracking techniques it was able to
measure horizontal displacements, and thus transverse velocities, in
the magnetic field. In quiet sun it is possible to detect both super
and mesogranulation. Horizontal velocities are as great as 1000 m/s
and the average velocity is 400 m/s. In magnetic regions horizontal
velocities are much less, about 100 m/s.
Title: On the Relation between Magnetic Field Structures and
Granulation
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.
Bibcode: 1987ApJ...317..892T
Altcode:
Narrow-band observations of a solar emerging-flux region, obtained
at 525.02 nm with resolution 0.5 arcsec using the Sacramento Peak
vacuum-tower telescope and the Spacelab 2 tunable filter on December
10, 1979, are reported. The data are presented in histograms and
characterized in detail. Magnetic-flux concentrations of 600-1000 G
are found to be located in areas of suppressed downflow near holes or
pores in the granulation pattern, while 100-500-G concentrations occur
in areas with stronger downdrafts, in cell-like structures of diameter
2-5 arcsec, the fields being aligned with dark intergranular lanes. It
is inferred that granulation concentrates the magnetic field in the
downflow lanes (as found in numerical simulations by Nordlund, 1983),
and that the magnetic structures are more diffuse and longer-lasting
than the bright spots; thus bright-point maps are contained in, rather
than equivalent to, magnetic-field maps.
Title: On the Relation Between Large-Scale Granular Flows and
Supergranules and Mesogranules
Authors: Simon, G.; Ferguson, S.; Tarbell, T.; Title, A.; Topka, K.;
November, L.; Zirin, H.
Bibcode: 1987BAAS...19R.935S
Altcode:
No abstract at ADS
Title: Simultaneous Observations of Emerging Flux from the Big Bear
Solar Observatory and the SOUP Instrument on Spacelab 2
Authors: Topka, K.; Ferguson, S.; Title, A.; Tarbell, T.; Zirin, H.;
Simon, G.; November, L.
Bibcode: 1987BAAS...19R.927T
Altcode:
No abstract at ADS
Title: On the Feasibility of Correlation Tracking at Moderate
Resolution
Authors: Bogart, R. S.; Scherrer, P. H.; Ferguson, S. H.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1987BAAS...19..941B
Altcode:
No abstract at ADS
Title: Simultaneous Sunspot Observations from the SOUP Instrument
on Spacelab 2 and the Big Bear Solar Observatory
Authors: Shine, R. A.; Title, A. M.; Topka, K. P.; Tarbell, T. D.;
Zirin, H.
Bibcode: 1987BAAS...19..927S
Altcode:
No abstract at ADS
Title: The Correlation Tracker Image Stabilization System for HRSO
Authors: Edwards, C. G.; Levay, M.; Gilbreth, C. W.; Tarbell, T. D.;
Title, A. M.; Wolfson, C. J.; Torgerson, D. D.
Bibcode: 1987BAAS...19..929E
Altcode:
No abstract at ADS
Title: Ocean Waves in the Photosphere: Measurements of Oscillations
with Wavelengths of 1 - 10 Mm from SOUP White Light Images
Authors: Tarbell, T. D.; Shine, R. A.; Ferguson, S. H.; Title, A. M.;
Leibacher, J. W.
Bibcode: 1987BAAS...19Q.936T
Altcode:
No abstract at ADS
Title: Exploding and Elongated Granules
Authors: Title, A. M.; Tarbell, T. D.; Ferguson, S. H.; Topka, K. P.
Bibcode: 1987BAAS...19Q.927T
Altcode:
No abstract at ADS
Title: New Ideas About Granulation Based on Data from the Solar
Optical Universal Polarimeter Instrument on Spacelab 2 and Magnetic
Data from Big Bear Solar Observatory
Authors: Title, A. M.; Tarbell, T. D.; Topka, K. P.; Shine, R. A.;
Simon, G. W.; Zirin, H.; SOUP Team
Bibcode: 1987LNP...292..173T
Altcode: 1987ssp..conf..173T
The SOUP flow fields have been compared with carefully aligned
magnetograms taken at the BBSO before, during, and after the SOUP
images. The magnetic field is observed to exist in locations where
either the flow is convergent or on the boundaries of the outflow from
a flow cell center. Streamlines calculated from the flow field agree
very well with the observed motions of the magnetic field in the BBSO
magnetogram movies.
Title: Properties of Granulation from Filtered Movies of Spacelab
2 SOUP Images
Authors: Title, A. M.; Tarbell, T. D.
Bibcode: 1986BAAS...18Q.992T
Altcode:
No abstract at ADS
Title: Measurements of Transverse Flows in the Solar Photosphere
from Spacelab 2 SOUP Images
Authors: Tarbell, T. D.; Title, A. M.; Ferguson, S. H.; November,
L. J.; Simon, G. W.
Bibcode: 1986BAAS...18R.992T
Altcode:
No abstract at ADS
Title: High-Resolution Observations of Changing Magnetic Features
on the Sun
Authors: Topka, K. P.; Tarbell, T. D.; Title, A. M.
Bibcode: 1986ApJ...306..304T
Altcode:
The total magnetic flux present in 28 small isolated unipolar features
that surround an active region has been measured on a well-registered
sequence of high-resolution magnetograms. Seventeen features showed no
changes, but the rest showed changes in measured flux with time that
were much greater than the uncertainty in the flux determination. Two
magnetic features showed evidence for increases in flux with time,
while nine others showed decay. In some cases the decaying features
appear to be canceling with nearby opposite polarity flux, which may
represent the submergence of flux below the photosphere. In others,
the observed decay occurs in regions that are strictly unipolar,
with no observable opposite polarity flux present. Some evidence for
the outward diffusion of flux from a decaying feature in a unipolar
region was found.
Title: Properties of Solar Granulation in Magnetic versus Non-Magnetic
Regions
Authors: Topka, K. P.; Tarbell, T. D.; SOUP Team
Bibcode: 1986BAAS...18..662T
Altcode:
No abstract at ADS
Title: Measurements of the Lifetimes of Individual Granules from
SOUP Data
Authors: Title, A. M.; Tarbell, T. D.; SOUP Team
Bibcode: 1986BAAS...18Q.661T
Altcode:
No abstract at ADS
Title: Videodisk Movies of the Solar Photosphere from the SOUP
Instrument on Spacelab 2
Authors: Tarbell, T. D.; Title, A. M.; SOUP Team
Bibcode: 1986BAAS...18R.661T
Altcode:
No abstract at ADS
Title: Precise Proper Motion Measurement of Solar Granulation
Authors: November, L. J.; Simon, G. W.; Tarbell, T. D.; Title, A. M.
Bibcode: 1986BAAS...18..665N
Altcode:
No abstract at ADS
Title: White-light movies of the solar photosphere from the soup
instrument on spacelab 2
Authors: Title, A. M.; Tarbell, T. D.; Simon, G. W.; Acton, L.;
Duncan, D.; Ferguson, S.; Finch, M.; Frank, Z.; Kelly, G.; Lindgren,
R.; Morrill, M.; Pope, T.; Reeves, R.; Rehse, R.; Shine, R.; Topka,
K.; Harvey, J.; Leibacher, J.; Livingston, W.; November, L.
Bibcode: 1986AdSpR...6h.253T
Altcode: 1986AdSpR...6..253T
We present initial results on solar granulation, pores and sunspots
from the white-light films obtained by the Solar Optical Universal
Polarimeter (SOUP) instrument on Spacelab 2. SOUP contains a
30-cm Cassegrain telescope, an active secondary mirror for image
stabilization, and a white-light optical system with 35-mm film
and video cameras. Outputs from the fine guidance servo provided
engineering data on the performance of the ESA Instrument Pointing
System (IPS). Several hours of movies were taken at various
disk and limb positions in quiet and active regions. The images
are diffraction-limited at 0.5 arc second resolution and are, of
course, free of atmospheric seeing and distortion. Properties of the
granulation in magnetic and non-magnetic regions are compared and are
found to differ significantly in size, rate of intensity variation,
and lifetime. In quiet sun on the order of fifty percent of the area
has at least one ``exploding granule'' occurring in it during a 25
minute period. Local correlation tracking has detected several types
of transverse flows, including systematic outflow from the penumbral
boundary of a spot, motion of penumbral filaments, and cellular flow
patterns of supergranular and mesogranular size. Feature tracking has
shown that in quiet sun the average granule fragment has a velocity
of about one kilometer per second.
Title: An Initial Study of Granulation Using Data from the SOUP
Instrument on SpaceLab 2
Authors: Tarbell, T. D.; Title, A. M.; SOUP Team
Bibcode: 1985BAAS...17..833T
Altcode:
No abstract at ADS
Title: A High Quality Movie from the SOUP Instrument on SpaceLab 2
Authors: Title, A. M.; Tarbell, T. D.; SOUP Team
Bibcode: 1985BAAS...17..896T
Altcode:
No abstract at ADS
Title: Scientific Observing Plans for the SOUP Instrument on Spacelab
2 in July, 1985
Authors: Tarbell, T. D.; Finch, M. L.; Title, A. M.
Bibcode: 1985BAAS...17..641T
Altcode:
No abstract at ADS
Title: Spectral imaging with a CID camera
Authors: Tarbell, T. D.
Bibcode: 1985lock.rept.....T
Altcode:
The electron velocity distribution is calculated for an idealized model
of the high electron mobility transistor using a many-particle Monte
Carlo model and a self-consistent two-dimensional Poisson solver. Hot
electron effects, nonstationary effects, and real space transfers
are analyzed. The results show that significant velocity overshoot
2.8 X 10 to the power 7th cm/s at 300 K and 3.7 X 10 to the 7th power
cm/s at 77 K exits under the gate and that the velocity overshoot; is
limited by both k-space transfer and real-space transfer. The value
of the overshoot is limited by both k-space transfer and real-space
transfer. The values of the overshoot velocities are much smaller that
those obtained from the more conventional drift-diffusion model.
Title: Magnetic Fields, Downdrafts, and Granulation in the Solar
Photosphere
Authors: Title, A. M.; Tarbell, T. D.
Bibcode: 1984BAAS...16.1001T
Altcode:
No abstract at ADS
Title: X-ray, Ultraviolet, Optical and Magnetic Structure in and
near an Active Region
Authors: Haisch, B. M.; Tarbell, T. D.; Bruner, M. E.; Acton, L. W.;
Bonnet, R. M.; Hagyard, M. J.
Bibcode: 1984BAAS...16Q1002H
Altcode:
No abstract at ADS
Title: High Resolution Observations of Magnetic Features on the Sun
Authors: Topka, K. P.; Tarbell, T. D.
Bibcode: 1984BAAS...16..991T
Altcode:
No abstract at ADS
Title: High Spatial Resolution Magnetic Observation of an Active
Region
Authors: Topka, K.; Tarbell, T.
Bibcode: 1984ssdp.conf..278T
Altcode:
High spatial resolution magnetograms of an active region reveal
apparent changes in the magnetic flux of small isolated features on
time scales less than 30 minutes. Both flux increases and decreases
are observed, sometimes for a single feature. These changes are seen
in small unipolar magnetic regions with no obvious changes observed
in any nearby opposite polarity features.
Title: Flux Changes in Small Magnetic Regions on the Sun
Authors: Topka, Ken P.; Tarbell, Ted
Bibcode: 1984BAAS...16Q.408T
Altcode:
No abstract at ADS
Title: The Solar Optical Universal Polarimeter
Authors: Finch, Mike L.; Tarbell, Ted D.; Title, Alan M.
Bibcode: 1984BAAS...16..404F
Altcode:
No abstract at ADS
Title: The Coordinated Instrument Package for the Solar Optical
Telescope
Authors: Wolfson, C. J.; Tarbell, T. D.; Topka, K. P.; Title, A. M.
Bibcode: 1983BAAS...15R.718W
Altcode:
No abstract at ADS
Title: A Real-Time Seeing Correction System for Solar Observations
Authors: Smithson, R. C.; Marshall, N. K.; Pope, T. P.; Sharbaugh,
R. J.; Tarbell, T. D.
Bibcode: 1983BAAS...15R.717S
Altcode:
No abstract at ADS
Title: Scientific Observing Plans for the SOT Coordinated Filtergraph
Spectrograph
Authors: Tarbell, T. D.; Wolfson, C. J.; Topka, K. P.
Bibcode: 1983BAAS...15R.709T
Altcode:
No abstract at ADS
Title: The rotation of horizontal-branch stars. I. Members of
the field.
Authors: Peterson, R. C.; Tarbell, T. D.; Carney, B. W.
Bibcode: 1983ApJ...265..972P
Altcode:
Multiple echelle spectra of eight field horizontal-branch stars at
a resolution of 2.4 x 10 to the 4th are obtained. At least two stars
exhibit intrinsically broadened lines. The line profiles of the broadest
lined star are well resolved, and rotation is found unambiguously to
be the cause of the broadening. It is pointed out that the inference
that rotation is a rather common phenomenon in horizontal-branch
stars has several ramifications for the normal stellar evolution of
metal-poor stars. The rotation rates of the main-sequence stars implied
if the angular momentum is primordial are discussed, together with the
possibility that rotation was acquired during the giant-branch phase
by angular momentum transfer from a companion.
Title: Fine Structure in the Solar Magnetic Field
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1982BAAS...14..924T
Altcode:
No abstract at ADS
Title: Low noise imaging photon counter for astronomy
Authors: Mertz, Lawrence N.; Tarbell, Theodore D.; Title, Alan M.
Bibcode: 1982ApOpt..21..628M
Altcode:
No abstract at ADS
Title: The initialisation of a mesoscale weather prediction model
using satellite and precipitation data
Authors: Tarbell, T. C.; Warner, T. T.; Wolcott, S. W.
Bibcode: 1981ESASP.165..259T
Altcode: 1981nmos.conf..259T
No abstract at ADS
Title: Sensor Technology for Adaptive Mirror Systems Applied to
Solar Astronomy
Authors: Smithson, R.; Tarbell, T.
Bibcode: 1981siwn.conf..480S
Altcode:
No abstract at ADS
Title: The Rotation of Horizontal Branch Stars
Authors: Tarbell, T. D.; Peterson, R. C.
Bibcode: 1981BAAS...13..516T
Altcode:
No abstract at ADS
Title: a Simple Image Motion Compensation System for Solar
Observations
Authors: Tarbell, T.; Smithson, R.
Bibcode: 1981siwn.conf..491T
Altcode:
No abstract at ADS
Title: Image Photon Counting System
Authors: Mertz, L.; Title, A.; Tarbell, T. D.
Bibcode: 1981BAAS...13..840M
Altcode:
No abstract at ADS
Title: Image motion compensation on the Spacelab 2 Solar Optical
Universal Polarimeter /SL2 SOUP/
Authors: Tarbell, T. D.; Duncan, D. W.; Finch, M. L.; Spence, G.
Bibcode: 1981SPIE..265...39T
Altcode:
The SOUP experiment on Spacelab 2 includes a 30 cm visible light
telescope and focal plane package mounted on the Instrument Pointing
System (IPS). Scientific goals of the experiment dictate pointing
stability requirements of less than 0.05 arcsecond jitter over periods
of 5-20 seconds. Quantitative derivations of these requirements from
two different aspects are presented: (1) avoidance of motion blurring
of diffraction-limited images; (2) precise coalignment of consecutive
frames to allow measurement of small image differences. To achieve this
stability, a fine guider system capable of removing residual jitter of
the IPS and image motions generated on the IPS cruciform instrument
support structure has been constructed. This system uses solar limb
detectors in the prime focal plane to derive an error signal. Image
motion due to pointing errors is compensated by the agile secondary
mirror mounted on piezoelectric transducers, controlled by a closed-loop
servo system.
Title: Video image processor on the Spacelab 2 Solar Optical Universal
Polarimeter /SL2 SOUP/
Authors: Lindgren, R. W.; Tarbell, T. D.
Bibcode: 1981SPIE..265...47L
Altcode:
The SOUP instrument is designed to obtain diffraction-limited digital
images of the sun with high photometric accuracy. The Video Processor
originated from the requirement to provide onboard real-time image
processing, both to reduce the telemetry rate and to provide meaningful
video displays of scientific data to the payload crew. This original
concept has evolved into a versatile digital processing system with
a multitude of other uses in the SOUP program. The central element in
the Video Processor design is a 16-bit central processing unit based on
2900 family bipolar bit-slice devices. All arithmetic, logical and I/O
operations are under control of microprograms, stored in programmable
read-only memory and initiated by commands from the LSI-11. Several
functions of the Video Processor are described, including interface
to the High Rate Multiplexer downlink, cosmetic and scientific data
processing, scan conversion for crew displays, focus and exposure
testing, and use as ground support equipment.
Title: A Simple Image Motion Compensation System for Solar
Observations
Authors: Smithson, R. C.; Tarbell, T. D.; Title, A. M.
Bibcode: 1980BAAS...12..915S
Altcode:
No abstract at ADS
Title: Status of the Spacelab 2 Solar Optical Universal Polarimeter
(SOUP)
Authors: Tarbell, T. D.; Finch, M. L.; Ramsey, H. E.; Schoolman,
S. A.; Title, A. M.
Bibcode: 1980BAAS...12..915T
Altcode:
No abstract at ADS
Title: Correlation Tracking Techniques as a Tool for Measuring Solar
Transverse Velocities
Authors: Smithson, R. C.; Tarbell, T. D.
Bibcode: 1980BAAS...12..437S
Altcode:
No abstract at ADS
Title: Using Tunable Filters for Two-Dimensional Solar Spectroscopy
Authors: Ramsey, H. B.; Schoolman, S. A.; Smithson, R. C.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1979BAAS...11..640R
Altcode:
No abstract at ADS
Title: Problems in the Detection of Weak Magnetic Fields on the Sun
Authors: Tarbell, T. D.
Bibcode: 1979BAAS...11..631T
Altcode:
No abstract at ADS
Title: In search of the perfect magnetogram.
Authors: Ramsey, H. E.; Schoolman, S. A.; Smithson, R. C.; Tarbell,
T. D.; Title, A. M.
Bibcode: 1979BAAS...11..611R
Altcode:
No abstract at ADS
Title: Weak and strong magnetic fields in the solar photosphere.
Authors: Tarbell, T. D.; Title, A. M.; Schoolman, S. A.
Bibcode: 1979ApJ...229..387T
Altcode:
Very high-resolution (0.5 arcsec) magnetograms of the quiet sun
and a plage are discussed which were obtained by using a tunable
birefringent filter in Fe I 6302A. A search for a turbulent bipolar
field with the use of co-added and spatially filtered frames is
unsuccessful. Statistical analysis sets an upper limit of 50 gauss on
the rms vertical component of such a field and probably rules out the
possibility of field strengths exceeding 100 gauss in the inner network
field observed at Kitt Peak. The area, total flux, and energy content
of the strong (kilogauss) network fields are measured and compared with
the upper limits for these properties of a hypothetical widespread
weak field. In the quiet photosphere, a weak background field may
contain interesting amounts of flux and energy, but the strong fields
are dominant at higher levels and in the plage. The total magnetic
energy in the quiet photospheric is roughly equal to the kinetic
energy of granular and oscillatory velocities at the same level. By
flux conservation, field strengths in the transition region are greater
than 25 gauss in the quiet network and 100 gauss in the plage.
Title: Pseudo-Resolution of Solar Magnetic Flux Tubes in Faculae
Authors: Tarbell, T. D.
Bibcode: 1978BAAS...10..657T
Altcode:
No abstract at ADS
Title: Correlation tracking study for meter-class solar telescope
on space shuttle
Authors: Smithson, R. C.; Tarbell, T. D.
Bibcode: 1977lock.reptR....S
Altcode:
The theory and expected performance level of correlation trackers used
to control the pointing of a solar telescope in space using white
light granulation as a target were studied. Three specific trackers
were modeled and their performance levels predicted for telescopes of
various apertures. The performance of the computer model trackers on
computer enhanced granulation photographs was evaluated. Parametric
equations for predicting tracker performance are presented.
Title: Measurements of magnetic fluxes and field strengths in the
photospheric network.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1977SoPh...52...13T
Altcode:
We present digital pictures of an active region network cell in five
quantities, measured simultaneously: continuum intensity, line-center
intensity, equivalent width, magnetogram signal, and magnetic field
strength. These maps are derived from computer analysis of circularly
polarized line profiles of FeI λ 5250.2; spectral and spatial
resolution are 1/40 Å and 1.5″, respectively. Measured Zeeman
splittings show the existence of strong magnetic fields (1000-1800 G)
at nearly all points with a magnetogram signal exceeding 125 G. The
mean and rms deviation of the field strengths change by less than
20% over a factor-of-four range of fluxes. From the significant
disparity between measured fluxes and field strengths, we conclude
that large flux patches (up to 4″ across) consist of closely-packed
unresolved filaments. The smallest filaments must be less than 0.7″
in diameter. We also observe the dark component of the photospheric
network, which appears to contain sizable transverse fields.
Title: Magnetic Field Strengths in Photospheric Filaments.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1976BAAS....8..501T
Altcode:
No abstract at ADS
Title: Measurements of solar magnetic fields by Fourier transform
techniques. II. Saturated and blended lines.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1976SoPh...47..563T
Altcode:
The Fourier techniques of Paper I have been exhaustively calibrated
using Unno's results for the absorption profile of a simple Zeeman
triplet. If a simple transformation is applied to the normalized line
depths, then magnetic field strengths and inclination angles can be
measured very accurately from noisy, saturated line profiles. Systematic
errors caused by saturation effects can be estimated and reduced by
varying one parameter. When a significant fraction of the line profile
is unsplit and unpolarized, large errors may be made in measurements
of low fields, unless the line is sufficiently weak. For a weak line,
a vertical field of 1600 gauss can be measured to 10% accuracy even
when 70% of the line profile is stray light. These stray light
errors are troublesome in measuring fields of gaps and pores but
not sunspots. Numerical results of our error analysis are presented
graphically.
Title: Erratum: the Triple-Alpha Rate, Screening Factors, and the
Helium Flash
Authors: Tarbell, T. D.; Rood, R. T.
Bibcode: 1976ApJ...203..770T
Altcode:
No abstract at ADS
Title: Semiconvection in halo stars and the primordial helium
abundance
Authors: Tarbell, Theodore Dean
Bibcode: 1976PhDT.......116T
Altcode:
No abstract at ADS
Title: Semiconvection in Halo Stars and the Primordial Helium
Abundance.
Authors: Tarbell, T. D.
Bibcode: 1976PhDT.........3T
Altcode: 1976PhDT.......113T
Convective overshooting and semiconvection in core-helium burning stars
are studied. A necessary condition for the onset of semiconvection
is derived, and the Schwarzschild neutrality criterion for the
semiconvective zone is justified. Evolutionary sequences for horizontal
branch stars in the globular cluster M3 are computed. They illustrate
the effects of different treatments of overshooting and semiconvection,
helium-burning nuclear reaction rates, and the primordial helium
abundance. Evolutionary models for subdwarf B stars are computed
which show excellent agreement with observed gravities and effective
temperatures. These models are burning helium at their centers with
thin, inert hydrogen envelopes. The hypothesis of mass loss at the
helium flash can explain the small envelope masses and the observed
gaps in the color distribution of blue halo stars. An upper limit
to the initial helium abundance of sdB stars is derived from their
light-to-mass ratios.
Title: The Triple-Alpha Rate, Screening Factors, and the Helium Flash
Authors: Tarbell, T. D.; Rood, K. T.
Bibcode: 1975ApJ...199..443T
Altcode:
A simple but accurate stability analysis is presented for a degenerate
stellar core containing a temperature-sensitive nuclear fuel. It is
used to study the dependence of the helium core mass at the helium
flash Mcf on the triple-a rate and its screening factor. Updated values
of Mof are computed, and a sizable discrepancy between the results of
different workers is removed. Subject headings: interiors, stellar -
late-type stars - nuclear reactions - stellar evolution
Title: High Resolution Observations of Photospheric Network Magnetic
Fields.
Authors: Tarbell, T. D.; Title, A. M.
Bibcode: 1975BAAS....7..459T
Altcode:
No abstract at ADS
Title: Measurement of Solar Magnetic Fields by Fourier Transform
Techniques. I: Unsaturated Lines
Authors: Title, A. M.; Tarbell, T. D.
Bibcode: 1975SoPh...41..255T
Altcode:
If the basic profile shapes of the normal Zeeman triplet do not have
zeros in their Fourier transform, the magnetic field splitting can
be determined independent of the profile shape. When the ratio of
the splitting of the components is greater than the intrinsic FWHM
of the component profiles the magnetic splitting can be determined
with significantly greater accuracy than the measurement accuracy of
the original profile. For Gaussian shaped components and a ratio of
magnetic splitting to FWHM of 1.5 the noise reduction factor is 25.
Title: On the Accuracy of Measuring Magnetic Fields Using Fourier
Transform Techniques
Authors: Tarbell, T. D.
Bibcode: 1975BAAS....7Q.351T
Altcode:
No abstract at ADS