Author name code: reardon
ADS astronomy entries on 2022-09-14
author:"Reardon, Kevin P."
------------------------------------------------------------------------
Title: Defining the Middle Corona
Authors: West, Matthew J.; Seaton, Daniel B.; Wexler, David B.;
Raymond, John C.; Del Zanna, Giulio; Rivera, Yeimy J.; Kobelski,
Adam R.; DeForest, Craig; Golub, Leon; Caspi, Amir; Gilly, Chris R.;
Kooi, Jason E.; Alterman, Benjamin L.; Alzate, Nathalia; Banerjee,
Dipankar; Berghmans, David; Chen, Bin; Chitta, Lakshmi Pradeep; Downs,
Cooper; Giordano, Silvio; Higginson, Aleida; Howard, Russel A.; Mason,
Emily; Mason, James P.; Meyer, Karen A.; Nykyri, Katariina; Rachmeler,
Laurel; Reardon, Kevin P.; Reeves, Katharine K.; Savage, Sabrina;
Thompson, Barbara J.; Van Kooten, Samuel J.; Viall, Nicholeen M.;
Vourlidas, Angelos
Bibcode: 2022arXiv220804485W
Altcode:
The middle corona, the region roughly spanning heliocentric altitudes
from $1.5$ to $6\,R_\odot$, encompasses almost all of the influential
physical transitions and processes that govern the behavior of
coronal outflow into the heliosphere. Eruptions that could disrupt
the near-Earth environment propagate through it. Importantly, it
modulates inflow from above that can drive dynamic changes at lower
heights in the inner corona. Consequently, this region is essential
for comprehensively connecting the corona to the heliosphere and for
developing corresponding global models. Nonetheless, because it is
challenging to observe, the middle corona has been poorly studied by
major solar remote sensing missions and instruments, extending back to
the Solar and Heliospheric Observatory (SoHO) era. Thanks to recent
advances in instrumentation, observational processing techniques,
and a realization of the importance of the region, interest in the
middle corona has increased. Although the region cannot be intrinsically
separated from other regions of the solar atmosphere, there has emerged
a need to define the region in terms of its location and extension
in the solar atmosphere, its composition, the physical transitions
it covers, and the underlying physics believed to be encapsulated by
the region. This paper aims to define the middle corona and give an
overview of the processes that occur there.
Title: Erratum: "A Study of Sunspot 3 Minute Oscillations Using ALMA
and GST" (2022, ApJ, 924, 100)
Authors: Chai, Yi; Gary, Dale E.; Reardon, Kevin P.; Yurchyshyn, Vasyl
Bibcode: 2022ApJ...933..247C
Altcode:
No abstract at ADS
Title: Evaluating Non-LTE Spectral Inversions with ALMA and IBIS
Authors: Hofmann, Ryan A.; Reardon, Kevin P.; Milic, Ivan; Molnar,
Momchil E.; Chai, Yi; Uitenbroek, Han
Bibcode: 2022ApJ...933..244H
Altcode: 2022arXiv220508760H
We present observations of a solar magnetic network region in the
millimeter continuum with the Atacama Large Millimeter/submillimeter
Array (ALMA) and in the Ca 8542 and Na 5896 Å spectral lines with
the Interferometric Bidimensional Spectrometer (IBIS). Our goal is
to compare the measurement of local gas temperatures provided by ALMA
with the temperature diagnostics provided by non-LTE inversions using
the STockholm inversion Code (STiC). In performing these inversions,
we find that using column mass as the reference height scale, rather
than optical depth, provides more reliable atmospheric profiles above
the temperature minimum and that the treatment of non-LTE hydrogen
ionization brings the inferred chromospheric temperatures into better
agreement with the ALMA measurements. The Band 3 brightness temperatures
are higher but well correlated spatially with the inversion-derived
temperatures at the height of formation of the Ca 8542 line core. The
Band 6 temperatures instead do not show good correlations with the
temperatures at any specific layer in the inverted atmospheres. We then
performed inversions that included the millimeter-continuum intensities
as an additional constraint. Incorporating Band 3 generally resulted in
atmospheres showing a strong temperature rise in the upper atmosphere,
while including Band 6 led to significant regions of anomalously low
temperatures at chromospheric heights. This is consistent with the
idea that the Band 6 emission can come from a combination of heights
ranging from the temperature minimum to upper chromosphere. The
poor constraints on the chromospheric electron density with existing
inversion codes introduces difficulties in determining the height(s)
of formation of the millimeter continuum as well as uncertainties in
the temperatures derived from the spectral lines.
Title: A Spectroscopic Survey of Infrared 1-4 μm Spectra in Regions
of Prominent Solar Coronal Emission Lines of Fe XIII, Si X, and Si IX
Authors: Ali, Aatiya; Paraschiv, Alin Razvan; Reardon, Kevin; Judge,
Philip
Bibcode: 2022ApJ...932...22A
Altcode: 2022arXiv220308636A
The infrared solar spectrum contains a wealth of physical data about
the Sun and is being explored using modern detectors and technology
with new ground-based solar telescopes. One such instrument will be
the ground-based Cryogenic Near-IR Spectro-Polarimeter of the Daniel
K. Inouye Solar Telescope (DKIST), which will be capable of sensitive
imaging of the faint infrared solar coronal spectra with full Stokes I,
Q, U, and V polarization states. Highly ionized magnetic dipole emission
lines have been observed in galaxies and the solar corona. Quantifying
the accuracy of spectral inversion procedures requires a precise
spectroscopic calibration of observations. A careful interpretation
of the spectra around prominent magnetic dipole lines is essential
for deriving physical parameters and particularly for quantifying the
off-limb solar coronal observations from DKIST. In this work, we aim to
provide an analysis of the spectral regions around the infrared coronal
emission lines of Fe XIII 1074.68 nm, Fe XIII 1079.79 nm, Si X 1430.10
nm, and Si IX 3934.34 nm, aligning with the goal of identifying solar
photospheric and telluric lines that will help facilitate production of
reliable inversions and data products from four sets of solar coronal
observations. The outputs can be integrated in processing pipelines
to produce level 2 science-ready data.
Title: Atmospheric Gravity Waves in the Magnetized Solar Atmosphere
Authors: Vesa, Oana; Jackiewicz, Jason; Reardon, Kevin
Bibcode: 2022AAS...24033203V
Altcode:
Atmospheric gravity waves (AGWs) are abundantly generated and excited
in the lower solar atmosphere by turbulent convection along with
other commonly studied waves, such as acoustic waves. These waves are
ubiquitous in various stellar and planetary atmospheres. On Earth, they
play a pivotal role in improving our global weather predictions and
climate models. On the Sun, AGWs are predicted to reach chromospheric
heights, where they can deposit substantial amounts of energy to
compensate for radiative losses. Recent numerical simulations have
explored how magnetic fields modify the behavior of AGWs and their
potential as seismic diagnostics for the average magnetic field. Using high-resolution, narrowband multi-wavelength ground-based
observations taken with IBIS at the Dunn Solar Telescope and
space-based data from the Solar Dynamics Observatory, we investigate
the behavior of these waves throughout the lower solar atmosphere on
the quiet Sun. By examining the phase lag from velocity and intensity
fluctuations measured at different atmospheric heights, we observe the
signatures of upwardly propagating AGWs at disk center up to around
the temperature minimum region. We detect unique velocity signatures
that have not been clearly observed to date. In the regime of AGWs,
our phase analysis of the intensity and velocity perturbations exhibit
different overall behavior. Given the weak average magnetic field in our
field of view, we find that the observed behavior of AGWs is consistent
with the weak field models reported in numerical simulations. Our
ultimate goal is to harness their untapped potential as diagnostics
to probe the average magnetic field structure and atmospheric flows
in a novel way. In future work, we plan to investigate the behavior
and energy flux of AGWs away from disk center and around more magnetic
environments. This study will serve as a pilot for future observations
of these waves, especially with the 4-meter Daniel K. Inouye Solar
Telescope.
Title: IBIS-A: The IBIS data Archive. High-resolution observations
of the solar photosphere and chromosphere with contextual data
Authors: Ermolli, Ilaria; Giorgi, Fabrizio; Murabito, Mariarita;
Stangalini, Marco; Guido, Vincenzo; Molinaro, Marco; Romano, Paolo;
Guglielmino, Salvatore L.; Viavattene, Giorgio; Cauzzi, Gianna;
Criscuoli, Serena; Reardon, Kevin P.; Tritschler, Alexandra
Bibcode: 2022A&A...661A..74E
Altcode: 2022arXiv220209946E
Context. The IBIS data Archive (IBIS-A) stores data acquired with
the Interferometric BIdimensional Spectropolarimeter (IBIS), which
was operated at the Dunn Solar Telescope of the US National Solar
Observatory from June 2003 to June 2019. The instrument provided series
of high-resolution narrowband spectropolarimetric imaging observations
of the photosphere and chromosphere in the range 5800-8600 Å and
co-temporal broadband observations in the same spectral range and
with the same field of view as for the polarimetric data.
Aims: We present the data currently stored in IBIS-A, as well as the
interface utilized to explore such data and facilitate its scientific
exploitation. To this end, we also describe the use of IBIS-A data
in recent and undergoing studies relevant to solar physics and
space weather research.
Methods: IBIS-A includes raw and
calibrated observations, as well as science-ready data. The latter
comprise maps of the circular, linear, and net circular polarization,
and of the magnetic and velocity fields derived for a significant
fraction of the series available in the archive. IBIS-A furthermore
contains links to observations complementary to the IBIS data, such
as co-temporal high-resolution observations of the solar atmosphere
available from the instruments onboard the Hinode and IRIS satellites,
and full-disk multi-band images from INAF solar telescopes.
Results: IBIS-A currently consists of 30 TB of data taken with IBIS
during 28 observing campaigns performed in 2008 and from 2012 to 2019
on 159 days. Of the observations, 29% are released as Level 1 data
calibrated for instrumental response and compensated for residual seeing
degradation, while 10% of the calibrated data are also available as
Level 1.5 format as multi-dimensional arrays of circular, linear, and
net circular polarization maps, and line-of-sight velocity patterns;
81% of the photospheric calibrated series present Level 2 data with
the view of the magnetic and velocity fields of the targets, as derived
from data inversion with the Very Fast Inversion of the Stokes Vector
code. Metadata and movies of each calibrated and science-ready series
are also available to help users evaluate observing conditions.
Conclusions: IBIS-A represents a unique resource for investigating
the plasma processes in the solar atmosphere and the solar origin of
space weather events. The archive currently contains 454 different
series of observations. A recently undertaken effort to preserve
IBIS observations is expected to lead in the future to an increase in
the raw measurements and the fraction of processed data available in
IBIS-A. Research supported by the H2020 SOLARNET grant no. 824135.
Title: Subarcsecond Imaging of a Solar Active Region Filament With
ALMA and IRIS
Authors: da Silva Santos, J. M.; White, S. M.; Reardon, K.; Cauzzi,
G.; Gunár, S.; Heinzel, P.; Leenaarts, J.
Bibcode: 2022FrASS...9.8115D
Altcode: 2022arXiv220413178D
Quiescent filaments appear as absorption features on the solar disk
when observed in chromospheric lines and at continuum wavelengths
in the millimeter (mm) range. Active region (AR) filaments are their
small-scale, low-altitude analogues, but they could not be resolved
in previous mm observations. This spectral diagnostic can provide
insight into the details of the formation and physical properties of
their fine threads, which are still not fully understood. Here, we shed
light on the thermal structure of an AR filament using high-resolution
brightness temperature (Tb) maps taken with ALMA Band 6 complemented by
simultaneous IRIS near-UV spectra, Hinode/SOT photospheric magnetograms,
and SDO/AIA extreme-UV images. Some of the dark threads visible in the
AIA 304 Å passband and in the core of Mg ii resonance lines have dark
(Tb < 5,000 K) counterparts in the 1.25 mm maps, but their visibility
significantly varies across the filament spine and in time. These
opacity changes are possibly related to variations in temperature and
electron density in filament fine structures. The coolest Tb values
(< 5,000 K) coincide with regions of low integrated intensity in the
Mg ii h and k lines. ALMA Band 3 maps taken after the Band 6 ones do not
clearly show the filament structure, contrary to the expectation that
the contrast should increase at longer wavelengths based on previous
observations of quiescent filaments. The ALMA maps are not consistent
with isothermal conditions, but the temporal evolution of the filament
may partly account for this.
Title: Chromospheric Carbon Monoxide Formation around a Solar Pore
Authors: Stauffer, Johnathan R.; Reardon, Kevin P.; Penn, Matt
Bibcode: 2022ApJ...930...87S
Altcode:
We present observations of NOAA AR 11159, obtained on 2011 February
14 in the 4.7 μm band of carbon monoxide (CO) and coordinated with
spectroscopic imaging of three atomic lines (Na I 5896 Å, Fe I 7090 Å,
and Ca II 8542 Å) which sample heights from the mid-photosphere to the
chromosphere. Phase-difference spectra between the observed spectral
lines instead indicate that the CO lines form at z ≍ 530-650 km in
the quiet Sun. During the two hours of observations, seven long-lived
cooling events ("cold bubbles") were observed in CO in the region
surrounding a large pore, but were not visible in the three atomic
lines. These events show self-similar temporal evolution with time
scales consistent with the chemical formation rate of CO at z ≍
1000 km. Due to the lack of such features in the surrounding quiet
Sun, we hypothesize that the magnetic canopy field surrounding the
pore, which suppresses the upward propagation of acoustic waves into
the chromosphere and the subsequent formation of shocks, depresses
the rate of acoustic heating and allows CO to condense and cool the
atmosphere at those heights. These "cold bubbles" may be a source of
the chromospheric CO that produces the unexpectedly high (z ≍ 1000
km) limb extensions seen in the stronger CO lines, and may provide
a unique opportunity to study this enigmatic component of the solar
atmosphere in spatially resolved observations.
Title: Revisiting the Solar Research Cyberinfrastructure Needs:
A White Paper of Findings and Recommendations
Authors: Nita, Gelu; Ahmadzadeh, Azim; Criscuoli, Serena;
Davey, Alisdair; Gary, Dale; Georgoulis, Manolis; Hurlburt, Neal;
Kitiashvili, Irina; Kempton, Dustin; Kosovichev, Alexander; Martens,
Piet; McGranaghan, Ryan; Oria, Vincent; Reardon, Kevin; Sadykov,
Viacheslav; Timmons, Ryan; Wang, Haimin; Wang, Jason T. L.
Bibcode: 2022arXiv220309544N
Altcode:
Solar and Heliosphere physics are areas of remarkable data-driven
discoveries. Recent advances in high-cadence, high-resolution
multiwavelength observations, growing amounts of data from realistic
modeling, and operational needs for uninterrupted science-quality data
coverage generate the demand for a solar metadata standardization and
overall healthy data infrastructure. This white paper is prepared as
an effort of the working group "Uniform Semantics and Syntax of Solar
Observations and Events" created within the "Towards Integration of
Heliophysics Data, Modeling, and Analysis Tools" EarthCube Research
Coordination Network (@HDMIEC RCN), with primary objectives to discuss
current advances and identify future needs for the solar research
cyberinfrastructure. The white paper summarizes presentations and
discussions held during the special working group session at the
EarthCube Annual Meeting on June 19th, 2020, as well as community
contribution gathered during a series of preceding workshops and
subsequent RCN working group sessions. The authors provide examples
of the current standing of the solar research cyberinfrastructure, and
describe the problems related to current data handling approaches. The
list of the top-level recommendations agreed by the authors of the
current white paper is presented at the beginning of the paper.
Title: A Strategy for a Coherent and Comprehensive Basis for
Understanding the Middle Corona
Authors: West, M. J.; Seaton, D. B.; Alzate, N.; Caspi, A.; DeForest,
C. E.; Gilly, C. R.; Golub, L.; Higginson, A. K.; Kooi, J. E.; Mason,
J. P.; Rachmeler, L. A.; Reeves, K. K.; Reardon, K.; Rivera, Y. J.;
Savage, S.; Viall, N. M.; Wexler, D. B.
Bibcode: 2022heli.conf.4060W
Altcode:
We describe a strategy for coherent and comprehensive observations
needed to achieve a fundamental understanding of the middle solar
corona.
Title: A Study of Sunspot 3 Minute Oscillations Using ALMA and GST
Authors: Chai, Yi; Gary, Dale E.; Reardon, Kevin P.; Yurchyshyn, Vasyl
Bibcode: 2022ApJ...924..100C
Altcode: 2021arXiv211105812C
Waves and oscillations are important solar phenomena, not only because
they can propagate and dissipate energy in the chromosphere, but also
because they carry information about the structure of the atmosphere
in which they propagate. The nature of the 3 minute oscillations
observed in the umbral region of sunspots is considered to be an
effect of propagation of magnetohydrodynamic waves upward from below
the photosphere. We present a study of sunspot oscillations and wave
propagation in NOAA Active Region 12470 using an approximately 1
hr long data set acquired on 2015 December 17 by the Atacama Large
Millimeter/submillimeter Array (ALMA), the Goode Solar Telescope
(GST) operating at the Big Bear Solar Observatory, the Atmospheric
Imaging Assembly on board the Solar Dynamics Observatory, and the
Interface Region Imaging Spectrograph. The ALMA data are unique in
providing a time series of direct temperature measurements in the
sunspot chromosphere. The 2 s cadence of ALMA images allows us to well
resolve the 3 minute periods typical of sunspot oscillations in the
chromosphere. Fourier analysis is applied to ALMA Band 3 (~100 GHz, ~3
mm) and GST Hα data sets to obtain power spectra as well as oscillation
phase information. We analyzed properties of the wave propagation by
combining multiple wavelengths that probe physical parameters of solar
atmosphere at different heights. We find that the ALMA temperature
fluctuations are consistent with that expected for a propagating
acoustic wave, with a slight asymmetry indicating nonlinear steepening.
Title: A Prototype of a Large Tunable Fabry-Pérot Interferometer
for Solar Spectroscopy
Authors: Greco, V.; Sordini, A.; Cauzzi, G.; Cavallini, F.; Del
Vecchio, C.; Giovannelli, L.; Berrilli, F.; Del Moro, D.; Reardon,
K.; Pietraszewski, K. A. R. B.
Bibcode: 2022PASP..134a5007G
Altcode: 2021arXiv211202224G
Large Fabry-Pérot Interferometers (FPIs) are used in a variety of
astronomical instrumentation, including spectro-polarimeters for 4 m
class solar telescopes. In this work we comprehensively characterize
the cavity of a prototype 150 mm FPI, sporting a novel, fully symmetric
design. Of particular interest, we define a new method to properly
assess the gravity effects on the interferometer's cavity when the
system is used in either the vertical or horizontal configuration,
both typical of solar observations. We show that the symmetric design
very effectively limits the combined effects of pre-load and gravity
forces to only a few nm over a 120 mm diameter illuminated surface,
with gravity contributing ~2 nm peak-to-valley (~0.3 nm rms) in either
configuration. We confirm a variation of the tilt between the plates
of the interferometer during the spectral scan, which can be mitigated
with appropriate corrections to the spacing commands. Finally, we show
that the dynamical response of the new system fully satisfies typical
operational scenarios. We conclude that large, fully symmetric FPIs
can be safely used within solar instrumentation in both, horizontal
and vertical position, with the latter better suited to limiting the
overall volume occupied by such an instrument.
Title: Final Report for SAG 21: The Effect of Stellar Contamination
on Space-based Transmission Spectroscopy
Authors: Rackham, Benjamin V.; Espinoza, Néstor; Berdyugina, Svetlana
V.; Korhonen, Heidi; MacDonald, Ryan J.; Montet, Benjamin T.; Morris,
Brett M.; Oshagh, Mahmoudreza; Shapiro, Alexander I.; Unruh, Yvonne C.;
Quintana, Elisa V.; Zellem, Robert T.; Apai, Dániel; Barclay, Thomas;
Barstow, Joanna K.; Bruno, Giovanni; Carone, Ludmila; Casewell, Sarah
L.; Cegla, Heather M.; Criscuoli, Serena; Fischer, Catherine; Fournier,
Damien; Giampapa, Mark S.; Giles, Helen; Iyer, Aishwarya; Kopp, Greg;
Kostogryz, Nadiia M.; Krivova, Natalie; Mallonn, Matthias; McGruder,
Chima; Molaverdikhani, Karan; Newton, Elisabeth R.; Panja, Mayukh;
Peacock, Sarah; Reardon, Kevin; Roettenbacher, Rachael M.; Scandariato,
Gaetano; Solanki, Sami; Stassun, Keivan G.; Steiner, Oskar; Stevenson,
Kevin B.; Tregloan-Reed, Jeremy; Valio, Adriana; Wedemeyer, Sven;
Welbanks, Luis; Yu, Jie; Alam, Munazza K.; Davenport, James R. A.;
Deming, Drake; Dong, Chuanfei; Ducrot, Elsa; Fisher, Chloe; Gilbert,
Emily; Kostov, Veselin; López-Morales, Mercedes; Line, Mike; Močnik,
Teo; Mullally, Susan; Paudel, Rishi R.; Ribas, Ignasi; Valenti, Jeff A.
Bibcode: 2022arXiv220109905R
Altcode:
Study Analysis Group 21 (SAG21) of the Exoplanet Exploration Program
Analysis Group (ExoPAG) was organized to study the effect of stellar
contamination on space-based transmission spectroscopy, a method for
studying exoplanetary atmospheres by measuring the wavelength-dependent
radius of a planet as it transits its star. Transmission spectroscopy
relies on a precise understanding of the spectrum of the star being
occulted. However, stars are not homogeneous, constant light sources
but have temporally evolving photospheres and chromospheres with
inhomogeneities like spots, faculae, and plages. This SAG has brought
together an interdisciplinary team of more than 100 scientists, with
observers and theorists from the heliophysics, stellar astrophysics,
planetary science, and exoplanetary atmosphere research communities,
to study the current needs that can be addressed in this context to
make the most of transit studies from current NASA facilities like
HST and JWST. The analysis produced 14 findings, which fall into
three Science Themes encompassing (1) how the Sun is used as our best
laboratory to calibrate our understanding of stellar heterogeneities
("The Sun as the Stellar Benchmark"), (2) how stars other than the Sun
extend our knowledge of heterogeneities ("Surface Heterogeneities of
Other Stars") and (3) how to incorporate information gathered for the
Sun and other stars into transit studies ("Mapping Stellar Knowledge
to Transit Studies").
Title: High-frequency Wave Power Observed in the Solar Chromosphere
with IBIS and ALMA
Authors: Molnar, Momchil E.; Reardon, Kevin P.; Cranmer, Steven R.;
Kowalski, Adam F.; Chai, Yi; Gary, Dale
Bibcode: 2021ApJ...920..125M
Altcode: 2021arXiv210708952M
We present observational constraints on the chromospheric heating
contribution from acoustic waves with frequencies between 5 and 50
mHz. We use observations from the Dunn Solar Telescope in New Mexico,
complemented with observations from the Atacama Large Millimeter Array
collected on 2017 April 23. The properties of the power spectra of the
various quantities are derived from the spectral lines of Ca II 854.2
nm, H I 656.3 nm, and the millimeter continuum at 1.25 and 3 mm. At
the observed frequencies, the diagnostics almost all show a power-law
behavior, whose particulars (slope, peak, and white-noise floors)
are correlated with the type of solar feature (internetwork, network,
and plage). In order to disentangle the vertical versus transverse
Alfvénic plasma motions, we examine two different fields of view: one
near disk center, and the other close to the limb. To infer the acoustic
flux in the middle chromosphere, we compare our observations with
synthetic observables from the time-dependent radiative hydrodynamic
RADYN code. Our findings show that acoustic waves carry up to about
1 kW m-2 of energy flux in the middle chromosphere, which
is not enough to maintain the quiet chromosphere. This is in contrast
to previous publications.
Title: Spectroscopic Study Of Wave Propagation In The Quiet Solar
Chromosphere with IRIS and IBIS
Authors: Molnar, M. E.; Cranmer, S. R.; Reardon, K. P.; Kowalski, A. F.
Bibcode: 2021AAS...23811303M
Altcode:
In this work, we present constraints on the longitudinal (compressive)
and transverse (Alfvenic) wave velocity perturbations observed in the
chromosphere. Better knowledge of the power in these different wave
modes in different regions of the atmosphere are important inputs into
models for the heating of the solar corona. By using observations
at multiple viewing angles (distances from the disc center), the
relative importance of these two components can be evaluated and
the power in the local acoustic flux can be explored. This work is
based on Doppler velocity measurements from IRIS of the ultraviolet
Mg II h & k and the Mn I 280.19 nm lines. These are compared with
co-temporal observations from IBIS of the H-alpha and Ca II 854.2 nm
chromospheric lines in the visible. The observed phase differences
between the velocity diagnostics in these different lines allows us to
estimate a formation height of the Mn I 280.19 nm line and compare it
with recent results from simulations. We can also measure the lowest
observed frequency at which the phase differences indicate the presence
of wave propagation in order to calculate the local acoustic-wave
cutoff. We calculate the coherency of the signals and their phases with
a cross-wavelet analysis. We further combine the IRIS observations
with 1D simulations of the lower solar atmosphere from the RADYN
code to estimate the wave flux inthe upper chromosphere. This study
provides heating constraints for the middle and upper chromospheres and
additional estimates of the transverse wave power in the chromosphere
extending previous work by Molnar et al. (2021).
Title: New Observations Of Chromospheric CO
Authors: Stauffer, J.; Reardon, K.
Bibcode: 2021AAS...23811301S
Altcode:
The detailed temperature structure of the solar photosphere and
chromosphere still holds some mysteries. A key example is the challenge
of trying to reconcile observations of spectral lines from the CO
molecule into the 1-D models of the solar atmosphere. The line core
temperatures of this molecular band suggest average temperatures
around 200 K lower than expected, while observations at the limb
indicate the presence of CO at what would be considered chromospheric
heights. Observations at higher resolution and with additional context
- provided by multi-wavelength datasets - might help resolve some of
these puzzles. In this work, I present observations of a solar
pore observed in the CO 4.7 µm band with the McMath Pierce Solar
Telescope. These observations were coordinated with simultaneous
IBIS/DST observations in the Fe I 709.0 nm, Na I 589.6 nm, and Ca
II 854.2 nm lines. These well understood lines, whose regions of
sensitivity span the base of the photosphere to the middle chromosphere,
provide a reference against which observations of the CO spectra may
be compared. Comparisons of the stronger, higher-forming CO lines
with the atomic spectra suggest that different components of the CO
spectrum are sensitive to regions of the solar atmosphere spanning the
temperature minimum (z = 500 km above the surface of the photosphere)
to chromospheric heights. Velocity phase spectra between the Fe and
CO lines suggests the CO line core velocity is sensitive to the upper
photosphere, while comparisons with the calcium line scans suggests
that the CO line core intensity has significant contributions from
both photospheric and chromospheric heights. Additionally, a time
series of the CO line core intensity reveals several intermittent,
CO-rich features, which appear primarily around the boundary of the
pore. These "cold bubbles" occur on spatio-temporal scales which are
distinct from the 5 minute oscillations and solar granulation, but are
instead consistent with the chemical reaction timescale of CO at z =
1000 km. A thorough understanding of the height of formation and
behavior of these lines is particularly valuable in anticipation of
observations of the 4.7 µm CO band at much better resolution from
DKIST's Cryo-NIRSP instrument.
Title: On The Interpretation Of H-alpha Filtergrams
Authors: Reardon, K.
Bibcode: 2021AAS...23831314R
Altcode:
For over 150 years the H-alpha line has been a mainstay of chromospheric
studies, which have revealed many important aspects of the structure
and dynamics of the upper solar atmosphere. The strong absorption
of this line in the visible range has long made it possible to
isolate its chromospheric contribution in the solar spectrum using
spectroheliographs, and later using various filter technologies. The
great bulk of observations in H-alpha, covering decades, have been
obtained using relatively broad-band filters (0.5-2 Å FWHM). More
recently, imaging spectroscopy in H-alpha, usually performed with
Fabry-Perot interferometers, has revealed new information about the
detailed spectral behavior and characteristics of this line. Using such
observations, we can now simulate and better interpret observations
taken through the more widely used, broad filters. In this paper,
I will evaluate the sensitivity of filter measurements to chromospheric
temperatures and velocities, depending on the placement and shape of
the filter passband. In particular, I will discuss how this will aid in
the interpretation of observations that will be obtained from the Visual
Broadband Imager (VBI) on the Daniel K. Inouye Solar Telescope (DKIST).
Title: ALMA and IRIS Observations Highlighting the Dynamics and
Structure of Chromospheric Plage
Authors: Hofmann, R. A.; Reardon, K.; Milic, I.
Bibcode: 2021AAS...23820505H
Altcode:
Studies of the thermal structure of the solar chromosphere are typically
hampered by the complexities of non-LTE radiative transfer. This issue
can be addressed using observations of the millimeter continuum, which
directly probes the electron temperatures in the chromosphere. In recent
years, the Atacama Large Millimeter/submillimeter Array (ALMA) has made
it possible, for the first time, to obtain millimeter observations of
sufficient spatial resolution to supplement spectral line observations
and inversions. Here, we present observations of a plage in the 3.0
mm and 1.2 mm continua with ~2 arcsecond resolution, combined with
simultaneous imaging spectroscopy observations from the Interferometric
Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope. We
compare the observed ALMA brightness temperatures with temperatures
inferred from spectral inversions using the Na D1 5896 Å and Ca II 8542
Å lines, and investigate the wide range of physical heights probed by
the millimeter continuum. We find that the millimeter emission arises
from a range of heights both above and below the chromospheric calcium
line, depending on the local temperature profile and electron densities.
Title: Inferring Plasma Flows In The Solar Photosphere &
Chromosphere Using Deep Learning And Surface Observations
Authors: Tremblay, B.; Reardon, K.; Attie, R.; Kazachenko, M.;
Tilipman, D.; Asensio Ramos, A.
Bibcode: 2021AAS...23812301T
Altcode:
Direct measurements of plasma motions are limited to the line-of-sight
component at the Sun's surface. Multiple tracking and inversion methods
were developed to infer the transverse motions from observational
data. Recently, the fully convolutional DeepVel & DeepVelU neural
networks were trained in conjunction with detailed magnetohydrodynamics
(MHD) simulations of the Quiet Sun and sunspots to recover the
instantaneous depth/height-dependent transverse velocity vector from a
combination of intensitygrams, magnetograms and/or Dopplergrams of the
solar surface. Through this supervised learning approach, the neural
network attempts to emulate the synthetic flows, and by extension the
physics, from the numerical simulation it was presented during its
training, i.e. its outputs are model-dependent and may be subjected
to biases. Although simulations have become increasingly realistic,
the validity of flows inferred by DeepVel or DeepVelU is subject to
debate when using real observational data as input. As a test, we use
white light images of the Quiet Sun photosphere (optical depth tau=1)
produced by the Interferometric BIdimensional Spectropolarimeter
(IBIS) installed at the Dunn Solar Telescope to infer plasma motions
approx. 150-200 km above the surface (i.e., near the transition between
the photosphere and the chromosphere) using DeepVel. We discuss work
in progress comparing the neural network estimates to the optical
flows determined from a time series of observational data formed near
150-200 km above the surface. Optical flows do not directly track
actual transverse plasma motions, but are correlated with physical
flows over certain spatial and temporal scales.
Title: Critical Science Plan for the Daniel K. Inouye Solar Telescope
(DKIST)
Authors: Rast, Mark P.; Bello González, Nazaret; Bellot Rubio,
Luis; Cao, Wenda; Cauzzi, Gianna; Deluca, Edward; de Pontieu, Bart;
Fletcher, Lyndsay; Gibson, Sarah E.; Judge, Philip G.; Katsukawa,
Yukio; Kazachenko, Maria D.; Khomenko, Elena; Landi, Enrico; Martínez
Pillet, Valentín; Petrie, Gordon J. D.; Qiu, Jiong; Rachmeler,
Laurel A.; Rempel, Matthias; Schmidt, Wolfgang; Scullion, Eamon; Sun,
Xudong; Welsch, Brian T.; Andretta, Vincenzo; Antolin, Patrick; Ayres,
Thomas R.; Balasubramaniam, K. S.; Ballai, Istvan; Berger, Thomas E.;
Bradshaw, Stephen J.; Campbell, Ryan J.; Carlsson, Mats; Casini,
Roberto; Centeno, Rebecca; Cranmer, Steven R.; Criscuoli, Serena;
Deforest, Craig; Deng, Yuanyong; Erdélyi, Robertus; Fedun, Viktor;
Fischer, Catherine E.; González Manrique, Sergio J.; Hahn, Michael;
Harra, Louise; Henriques, Vasco M. J.; Hurlburt, Neal E.; Jaeggli,
Sarah; Jafarzadeh, Shahin; Jain, Rekha; Jefferies, Stuart M.; Keys,
Peter H.; Kowalski, Adam F.; Kuckein, Christoph; Kuhn, Jeffrey R.;
Kuridze, David; Liu, Jiajia; Liu, Wei; Longcope, Dana; Mathioudakis,
Mihalis; McAteer, R. T. James; McIntosh, Scott W.; McKenzie, David
E.; Miralles, Mari Paz; Morton, Richard J.; Muglach, Karin; Nelson,
Chris J.; Panesar, Navdeep K.; Parenti, Susanna; Parnell, Clare E.;
Poduval, Bala; Reardon, Kevin P.; Reep, Jeffrey W.; Schad, Thomas A.;
Schmit, Donald; Sharma, Rahul; Socas-Navarro, Hector; Srivastava,
Abhishek K.; Sterling, Alphonse C.; Suematsu, Yoshinori; Tarr, Lucas
A.; Tiwari, Sanjiv; Tritschler, Alexandra; Verth, Gary; Vourlidas,
Angelos; Wang, Haimin; Wang, Yi-Ming; NSO and DKIST Project; DKIST
Instrument Scientists; DKIST Science Working Group; DKIST Critical
Science Plan Community
Bibcode: 2021SoPh..296...70R
Altcode: 2020arXiv200808203R
The National Science Foundation's Daniel K. Inouye Solar Telescope
(DKIST) will revolutionize our ability to measure, understand,
and model the basic physical processes that control the structure
and dynamics of the Sun and its atmosphere. The first-light DKIST
images, released publicly on 29 January 2020, only hint at the
extraordinary capabilities that will accompany full commissioning of
the five facility instruments. With this Critical Science Plan (CSP)
we attempt to anticipate some of what those capabilities will enable,
providing a snapshot of some of the scientific pursuits that the DKIST
hopes to engage as start-of-operations nears. The work builds on the
combined contributions of the DKIST Science Working Group (SWG) and
CSP Community members, who generously shared their experiences, plans,
knowledge, and dreams. Discussion is primarily focused on those issues
to which DKIST will uniquely contribute.
Title: Inferring Plasma Flows in the Solar Photosphere &
Chromosphere using Deep Learning and Surface Observations
Authors: Tremblay, Benoit; Reardon, Kevin; Attié, Raphaël;
Kazachenko, Maria; Asensio Ramos, Andrés; Tilipman, Dennis
Bibcode: 2021csss.confE.204T
Altcode:
Direct measurements of plasma motions are limited to the line-of-sight
component at the Sun's surface. Multiple tracking and inversion methods
were developed to infer the transverse motions from observational
data. Recently, the fully convolutional DeepVel & DeepVelU neural
networks were trained in conjunction with detailed magnetohydrodynamics
(MHD) simulations of the Quiet Sun and sunspots to recover the
instantaneous depth/height-dependent transverse velocity vector from a
combination of intensitygrams, magnetograms and/or Dopplergrams of the
solar surface. Through this supervised learning approach, the neural
network attempts to emulate the synthetic flows, and by extension the
physics, from the numerical simulation it was presented during its
training, i.e. its outputs are model-dependent and may be subjected
to biases. Although simulations have become increasingly realistic,
the validity of flows inferred by DeepVel or DeepVelU is subject to
debate when using real observational data as input. As a test, we use
white light images of the Quiet Sun photosphere (optical depth tau=1)
produced by the Interferometric BIdimensional Spectropolarimeter
(IBIS) installed at the Dunn Solar Telescope to infer plasma motions
approx. 150-200 km above the surface (i.e., near the transition between
the photosphere and the chromosphere) using DeepVel. We discuss work
in progress comparing the neural network estimates to the optical
flows determined from a time series of observational data formed near
150-200 km above the surface. Optical flows do not directly track
actual transverse plasma motions, but are correlated with physical
flows over certain spatial and temporal scales.
Title: An overall view of temperature oscillations in the solar
chromosphere with ALMA
Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.;
Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu,
X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen,
B.; Reardon, K.; White, S. M.
Bibcode: 2021RSPTA.37900174J
Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J
By direct measurements of the gas temperature, the Atacama Large
Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic
tool to study the solar chromosphere. Here, we present an overview
of the brightness-temperature fluctuations from several high-quality
and high-temporal-resolution (i.e. 1 and 2 s cadence) time series
of images obtained during the first 2 years of solar observations
with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz)
and 1.25 mm (239 GHz), respectively. The various datasets represent
solar regions with different levels of magnetic flux. We perform
fast Fourier and Lomb-Scargle transforms to measure both the spatial
structuring of dominant frequencies and the average global frequency
distributions of the oscillations (i.e. averaged over the entire field
of view). We find that the observed frequencies significantly vary from
one dataset to another, which is discussed in terms of the solar regions
captured by the observations (i.e. linked to their underlying magnetic
topology). While the presence of enhanced power within the frequency
range 3-5 mHz is found for the most magnetically quiescent datasets,
lower frequencies dominate when there is significant influence from
strong underlying magnetic field concentrations (present inside and/or
in the immediate vicinity of the observed field of view). We discuss
here a number of reasons which could possibly contribute to the power
suppression at around 5.5 mHz in the ALMA observations. However,
it remains unclear how other chromospheric diagnostics (with an
exception of Hα line-core intensity) are unaffected by similar
effects, i.e. they show very pronounced 3-min oscillations dominating
the dynamics of the chromosphere, whereas only a very small fraction
of all the pixels in the 10 ALMA datasets analysed here show peak power
near 5.5 mHz. This article is part of the Theo Murphy meeting issue
`High-resolution wave dynamics in the lower solar atmosphere'.
Title: A Survey of Computational Tools in Solar Physics
Authors: Bobra, M.; Mumford, S.; Hewett, R. J.; Christe, S.; Reardon,
K.; Savage, S. L.; Ireland, J.; Mendes Domingos Pereira, T.; Chen,
B.; Pérez-Suárez, D.
Bibcode: 2020AGUFMSH0100001B
Altcode:
The SunPy project is happy to announce the results of the solar physics
community survey! For six months last year, between February
and July 2019, the SunPy Project asked members of the solar physics
community to fill out a 13-question survey about computational software
and hardware. A total of 364 community members, across 35 countries,
took our survey. We found that 99±0.5% of respondents use
software in their research and 66% use the Python scientific software
stack. Students are twice as likely as faculty, staff scientists, and
researchers to use Python. In this respect, the astrophysics and solar
physics communities differ widely: 78% of solar physics faculty, staff
scientists, and researchers in our sample uses IDL, compared with 44%
of astrophysics faculty and scientists sampled by Momcheva and Tollerud
(2015). We also found that most respondents (63±4%) have not taken
any computer science courses at an undergraduate or graduate level. We
found that a small fraction of respondents use the commercial cloud (5%)
or a regional or national cluster (14%) for their research. Finally,
we found that 73±4% of respondents cite scientific software in their
research, although only 42±3% do so routinely. Our survey results
are published in the journal Solar Physics and available via open
access at the following URL: https://doi.org/10.1007/s11207-020-01622-2.
Title: Spectroscopic Inversions & Calibrations for DKIST Coronal
Observations
Authors: Ali, A.; Paraschiv, A.; Reardon, K.; Judge, P. G.
Bibcode: 2020AGUFMSH0280014A
Altcode:
The Cryo-NIRSP's (Cryogenic Near-IR Spectro-Polarimeter) is one of the
DKIST instruments capable of sensitive imaging of faint infrared coronal
solar spectra, and its primary goal is to measure the full polarization
state (Stokes I, Q, U and V) of spectral lines originating on the Sun
at different wavelengths. Producing data products from off-limb solar
coronal observations from the DKIST telescope is essential when trying
to study its future observations. Quantifying the accuracy of spectral
inversion procedures based on its spectral comparisons to absorption
and telluric calibrated spectra will give insight to interpreting
valid DKIST observations and its ultimate findings. Using simulated
contaminated data of both pure and noisy data sets has allowed us
to compare the wavelength shifts and broadening properties to help
pinpoint where contamination would affect the data set as a whole,
and by how much. In doing so, we developed code that will eventually
be integrated in the DKIST Level-2 pipeline. Working to compare
these findings to absorption and telluric readings will further help
minimize the uncertainties read in through observations, and give
direction on how to reduce the original coronal data in hopes to refine
it. Understanding the origins and magnitude of the contamination would
therefore help refine the original coronal data and make it compatible
for data processing, and would assist the automation of processing
the data observed by the DKIST telescope.
Title: Constraining wave propagation throughout the solar atmosphere
with IBIS, ALMA and IRIS
Authors: Molnar, M.; Reardon, K.; Cranmer, S. R.; Kowalski, A. F.
Bibcode: 2020AGUFMSH0010003M
Altcode:
The heating mechanism of the solar chromosphere is still an open
scientific question. We present observational constraints on the
high-frequency (acoustic) wave contribution to the chromospheric
heating. We utilize a unique combination of observations from NSO's
Dunn Solar Telescope and the Atacama Large Millimeter Array obtained on
April 23rd 2017 to estimate the high-frequency wave flux in the lower
solar atmosphere. We extend this study to the upper chromosphere and
the transition region with archival IRIS data. We infer the wave flux
through comparison of the observations with synthetic observables
from the time-dependent hydrodynamic RADYN code. Our findings are
able to constrain the wave flux at higher altitudes in the solar
atmosphere than previous works using similar approaches. Furthermore,
the different diagnostics we use form at different heights, which
allow us to explore the propagation and dissipation of waves with
height. We will discuss future plans to extend this work with more
advanced modeling and additional observations with the upcoming Innoue
Solar Telescope (DKIST).
Title: The CO Fundamental Band as an LTE Diagnostic of the Temperature
Minimum
Authors: Stauffer, J.; Reardon, K.
Bibcode: 2020AGUFMSH004..02S
Altcode:
Spectral and spectro-polarimetric inversion techniques are a powerful
set of tools capable of inferring the 3-D structure of the solar
atmosphere from a set of observed atomic spectral lines. However, the
degree to which an inversion can retrieve the true solar atmospheric
profiles depends on the formation properties of the observed lines,
as well as the complexity of the physics involved in the inversion. In
this work, we invert DST/IBIS observations of several atomic lines (Na
I 589.6 nm, Fe I 709.0 nm, and Ca II 854.2 nm, which together sample
the lower photosphere to the mid chromosphere) using the Stockholm
Inversion Code (STiC) for the temperature and velocity structure in
the vicinity of a decaying sunspot observed on 02/14/2011. The results
of these inversions are compared to simultaneous observations of the
fundamental (Δν=1) ro-vibrational band of CO, which is comprised
of dozens of individual molecular lines with varying strengths and
formation properties. These lines form in LTE and can be used to sample
the properties of the Solar temperature minimum; therefore, by comparing
the inversion results to maps of CO column density and brightness
temperature, we can determine the fidelity of the NLTE STiC inversions
in inferring the qualities of the temperature minimum. Particular focus
is given to several CO-rich "cold spots" which appear in the vicinity
of the sunspot remnant during the observing sequence.
Title: ALMA observations and spectral inversions - what can we learn
about the Sun and our techniques?
Authors: Hofmann, R.; Reardon, K.; Milic, I.
Bibcode: 2020AGUFMSH0010002H
Altcode:
Studies of the thermal structure of the solar chromosphere are typically
hampered by the complexities of non-LTE radiative transfer. This issue
can be addressed using observations of the millimeter continuum, which
directly probes the electron temperatures in the chromosphere. In recent
years, the Atacama Large Millimeter/submillimeter Array (ALMA) has made
it possible, for the first time, to obtain millimeter observations of
sufficient spatial resolution to supplement spectral line observations
and inversions. Here, we present observations of a plage in the 3.0
mm and 1.2 mm continua with ~2 arcsecond resolution, combined with
simultaneous imaging spectroscopy observations from the Interferometric
Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope. We
compare the observed ALMA brightness temperatures with temperatures
inferred from spectral inversions using the Na D1 5896 Å and Ca II 8542
Å lines, and investigate the wide range of physical heights probed by
the millimeter continuum. We find that the millimeter emission arises
from a range of heights both above and below the chromospheric calcium
line, depending on the local temperature profile and electron densities.
Title: Inferring Plasma Flows in the Solar Photosphere &
Chromosphere using Deep Learning and Surface Observations
Authors: Tremblay, B.; Reardon, K.; Attié, R.; Asensio Ramos, A.;
Kazachenko, M.; Tilipman, D.
Bibcode: 2020AGUFMSH007..08T
Altcode:
Direct measurements of plasma motions are limited to the line-of-sight
component at the Sun's surface. Multiple tracking and inversion methods
were developed to infer the transverse motions from observational
data. Optical flows do not directly track actual transverse plasma
motions, but our most recent results show that unsupervised flow
tracking performed on simulation data of the solar surface with the
Ball-tracking method accurately reconstructs the true transverse
plasma velocity over certain spatial and temporal scales. Recently,
the fully convolutional DeepVel & DeepVelU neural networks
were trained in conjunction with detailed magnetohydrodynamics (MHD)
simulations of the Quiet Sun and sunspots to recover the instantaneous
depth/height-dependent transverse velocity vector from a combination
of intensitygrams, magnetograms and/or Dopplergrams of the solar
surface. Through this supervised learning approach, the neural
network attempts to emulate the synthetic flows, and by extension the
physics, from the numerical simulation it was presented during its
training, i.e. its outputs are model-dependent and may be subjected
to biases. Although simulations have become increasingly realistic,
the validity of flows inferred by DeepVel or DeepVelU is subject to
debate when using real observational data as input. As a test, we use
white light images of the Quiet Sun photosphere (optical depth τ=1)
produced by the Interferometric BIdimensional Spectropolarimeter (IBIS)
installed at the Dunn Solar Telescope to infer plasma motions at optical
depth τ=0.1 (i.e., near the transition between the photosphere and
the chromosphere) using DeepVelU. We then compare the results to
the optical flows determined from a time series of observational
data formed near τ=0.1, which may not be subjected to the biases
present in DeepVelU . Finally, we discuss work in progress to infer
photospheric and chromospheric (optical) flows through unsupervised
learning, i.e. learning strictly from observational data and thus
without simulations.
Title: SunPy 2.0: the community-developed open-source solar data
analysis environment for Python
Authors: Murray, S. A.; Barnes, W.; Bobra, M.; Christe, S.; Freij,
N.; Hayes, L.; Ireland, J.; Mumford, S.; Pérez-Suárez, D.; Ryan,
D.; Shih, A. Y.; Chanda, P.; Hewett, R.; Hughitt, V. K.; Hill, A.;
Hiware, K.; Inglis, A.; Kirk, M. S.; Konge, S.; Mason, J. P.; Maloney,
S.; Panda, A.; Park, J.; M D Pereira, T.; Reardon, K.; Savage, S. L.;
Sipocz, B.; Stansby, D.; Jain, Y.; Taylor, G.; Yadav, T.; Kien, H. T.;
Chen, B.; Glogowski, K.
Bibcode: 2020AGUFMSH0100006M
Altcode:
The SunPy project facilitates and promotes the use and development
of several community-led, free, and open-source data analysis
software packages for solar physics based on the scientific
Python environment. The project achieves this goal by developing
and maintaining the SunPy core package and supporting an ecosystem
of affiliated packages. The SunPy community is pleased to announce
the release of version 2.0! Some highlights for this release include
updates to the Fido data search and retrieval tool, various fixes to the
sunpy.map sub package, and integration of differential rotation into
the sunpy.coordinates framework. Also new in SunPy 2.0 is the aiapy
package for analyzing data from SDO/AIA, which replaces aiaprep. Learn
more about how to install and use the publicly available code at sunpy.org , as well as information about
how to get involved with the community!
Title: The Propagation of Atmospheric Gravity Waves in the Magnetic
Solar Atmosphere
Authors: Vesa, O.; Jackiewicz, J.; Reardon, K.
Bibcode: 2020SPD....5120708V
Altcode:
Atmospheric gravity waves are generated by overshooting convection and
are thought to propagate throughout the lower solar atmosphere. The
properties of these waves will be modified by the strength and
orientation of the magnetic field, resulting in either suppression at
regions of strong magnetic activity or mode conversion. By combining
high-resolution, multi-wavelength IBIS observations and co-aligned SDO
data, we investigate the characteristics of these waves throughout the
lower solar atmosphere, with the goal of revealing new information about
the quiet Sun's magnetic field. We have analyzed line core velocities
and intensities of four spectral lines (Ca II 8542 Å, Fe I 5434 Å,
Fe I 7090 Å, and K I 7699 Å) along with HMI's Fe I 6173 Å, to
derive phase differences and construct k-ω diagnostic diagrams at a
range of heights. We detect the signatures of propagating atmospheric
gravity waves at disk center. We will ultimately use multiple datasets
taken at disk center, near the limb, and around active regions to
also explore their large horizontal velocities and behavior in more
magnetic environments.
Title: High-frequency Wave Power Observed in the Chromosphere with
IBIS and ALMA
Authors: Molnar, M. E.; Cranmer, S.; Reardon, K.; Kowalski, A.
Bibcode: 2020SPD....5120106M
Altcode:
The heating mechanism of the solar chromosphere is still an open
scientific question. In this work we study observational constraints on
the contribution to chromospheric heating from high-frequency acoustic
waves. We utilize a unique combination of observations from NSO's Dunn
Solar Telescope and from the Atacama Large Millimeter Array obtained
on April 23rd 2017 to estimate the high-frequency wave flux in the
lower solar atmosphere. The wave flux is inferred from comparison of
the observations with synthetic observables from the time-dependent
hydrodynamic RADYN code. Our findings suggest thatacoustic waves may
carry up to a few kW/m2 of flux, which is comparable to
what is required to heat the quiet chromosphere.
Title: Spectral deconvolution with deep learning: removing the
effects of spectral PSF broadening
Authors: Molnar, Momchil; Reardon, Kevin P.; Osborne, Christopher;
Milić, Ivan
Bibcode: 2020FrASS...7...29M
Altcode: 2020arXiv200505529M
We explore novel methods of recovering the original spectral line
profiles from data obtained by instruments that sample those profiles
with an extended or multipeaked spectral transmission profile. The
techniques are tested on data obtained at high spatial resolution from
the Fast Imaging Solar Spectrograph (FISS) grating spectrograph at the
Big Bear Solar Observatory and from the Interferometric Bidimensional
Spectrometer (IBIS) instrument at the Dunn Solar Telescope. The method
robustly deconvolves wide spectral transmission profiles for fields of
view sampling a variety of solar structures (granulation, plage and
pores) with a photometrical precision of less than 1%. The results
and fidelity of the method are tested on data from IBIS obtained
using several different spectral resolution modes. The method, based
on convolutional neural networks (CNN), is extremely fast, performing
about 10^5 deconvolutions per second on a single CPU for a spectrum with
40 wavelength samples. This approach is applicable for deconvolving
large amounts of data from instruments with wide spectral profiles,
such as the Visible Tunable Filter (VTF) on the DKI Solar Telescope
(DKIST). We also investigate the application to future instruments
by recovering spectral line profiles obtained with a theoretical
multi-peaked spectral transmission profile. We further discuss the
limitations of this deconvolutional approach through the analysis of
the dimensionality of the original and multiplexed data.
Title: Solar Disk Center Shows Scattering Polarization in the Sr I
4607 Å Line
Authors: Zeuner, Franziska; Manso Sainz, Rafael; Feller, Alex; van
Noort, Michiel; Solanki, Sami K.; Iglesias, Francisco A.; Reardon,
Kevin; Martínez Pillet, Valentín
Bibcode: 2020ApJ...893L..44Z
Altcode: 2020arXiv200403679Z
Magnetic fields in turbulent, convective high-β plasma naturally
develop highly tangled and complex topologies - the solar photosphere
being the paradigmatic example. These fields are mostly undetectable by
standard diagnostic techniques with finite spatio-temporal resolution
due to cancellations of Zeeman polarization signals. Observations of
resonance scattering polarization have been considered to overcome
these problems. But up to now, observations of scattering polarization
lack the necessary combination of high sensitivity and high spatial
resolution in order to directly infer the turbulent magnetic structure
at the resolution limit of solar telescopes. Here, we report the
detection of clear spatial structuring of scattering polarization
in a magnetically quiet solar region at disk center in the Sr I
4607 Å spectral line on granular scales, confirming theoretical
expectations. We find that the linear polarization presents a
strong spatial correlation with the local quadrupole of the radiation
field. The result indicates that polarization survives the dynamic and
turbulent magnetic environment of the middle photosphere and is thereby
usable for spatially resolved Hanle observations. This is an important
step toward the long-sought goal of directly observing turbulent
solar magnetic fields at the resolution limit and investigating their
spatial structure.
Title: A Survey of Computational Tools in Solar Physics
Authors: Bobra, Monica G.; Mumford, Stuart J.; Hewett, Russell J.;
Christe, Steven D.; Reardon, Kevin; Savage, Sabrina; Ireland, Jack;
Pereira, Tiago M. D.; Chen, Bin; Pérez-Suárez, David
Bibcode: 2020SoPh..295...57B
Altcode: 2020arXiv200314186B
The SunPy Project developed a 13-question survey to understand the
software and hardware usage of the solar-physics community. Of the
solar-physics community, 364 members across 35 countries responded
to our survey. We found that 99 ±0.5 % of respondents use software
in their research and 66% use the Python scientific-software
stack. Students are twice as likely as faculty, staff scientists,
and researchers to use Python rather than Interactive Data Language
(IDL). In this respect, the astrophysics and solar-physics communities
differ widely: 78% of solar-physics faculty, staff scientists, and
researchers in our sample uses IDL, compared with 44% of astrophysics
faculty and scientists sampled by Momcheva and Tollerud (2015). 63
±4 % of respondents have not taken any computer-science courses at an
undergraduate or graduate level. We also found that most respondents use
consumer hardware to run software for solar-physics research. Although
82% of respondents work with data from space-based or ground-based
missions, some of which (e.g. the Solar Dynamics Observatory and Daniel
K. Inouye Solar Telescope) produce terabytes of data a day, 14% use
a regional or national cluster, 5% use a commercial cloud provider,
and 29% use exclusively a laptop or desktop. Finally, we found that
73 ±4 % of respondents cite scientific software in their research,
although only 42 ±3 % do so routinely.
Title: The SunPy Project: Open Source Development and Status of the
Version 1.0 Core Package
Authors: SunPy Community; Barnes, Will T.; Bobra, Monica G.; Christe,
Steven D.; Freij, Nabil; Hayes, Laura A.; Ireland, Jack; Mumford,
Stuart; Perez-Suarez, David; Ryan, Daniel F.; Shih, Albert Y.; Chanda,
Prateek; Glogowski, Kolja; Hewett, Russell; Hughitt, V. Keith; Hill,
Andrew; Hiware, Kaustubh; Inglis, Andrew; Kirk, Michael S. F.; Konge,
Sudarshan; Mason, James Paul; Maloney, Shane Anthony; Murray, Sophie
A.; Panda, Asish; Park, Jongyeob; Pereira, Tiago M. D.; Reardon,
Kevin; Savage, Sabrina; Sipőcz, Brigitta M.; Stansby, David; Jain,
Yash; Taylor, Garrison; Yadav, Tannmay; Rajul; Dang, Trung Kien
Bibcode: 2020ApJ...890...68S
Altcode: 2020ApJ...890...68A
The goal of the SunPy project is to facilitate and promote the
use and development of community-led, free, and open source data
analysis software for solar physics based on the scientific Python
environment. The project achieves this goal by developing and
maintaining the sunpy core package and supporting an ecosystem of
affiliated packages. This paper describes the first official stable
release (version 1.0) of the core package, as well as the project
organization and infrastructure. This paper concludes with a discussion
of the future of the SunPy project.
Title: Hi-C 2.1 Observations of Small-scale
Miniature-filament-eruption-like Cool Ejections in an Active Region
Plage
Authors: Sterling, Alphonse C.; Moore, Ronald L.; Panesar, Navdeep
K.; Reardon, Kevin P.; Molnar, Momchil; Rachmeler, Laurel A.; Savage,
Sabrina L.; Winebarger, Amy R.
Bibcode: 2020ApJ...889..187S
Altcode: 2019arXiv191202319S
We examine 172 Å ultra-high-resolution images of a solar plage region
from the High-Resolution Coronal Imager, version 2.1 (Hi-C 2.1, or Hi-C)
rocket flight of 2018 May 29. Over its five minute flight, Hi-C resolved
a plethora of small-scale dynamic features that appear near noise level
in concurrent Solar Dynamics Observatory (SDO) Atmospheric Imaging
Assembly (AIA) 171 Å images. For 10 selected events, comparisons with
AIA images at other wavelengths and with Interface Region Imaging
Spectrograph (IRIS) images indicate that these features are cool
(compared to the corona) ejections. Combining Hi-C 172 Å, AIA 171 Å,
IRIS 1400 Å, and Hα, we see that these 10 cool ejections are similar
to the Hα "dynamic fibrils" and Ca II "anemone jets" found in earlier
studies. The front of some of our cool ejections are likely heated,
showing emission in IRIS 1400 Å. On average, these cool ejections
have approximate widths 3"2 ± 2"1, (projected) maximum heights and
velocities 4"3 ± 2"5 and 23 ± 6 km s-1, and lifetimes 6.5
± 2.4 min. We consider whether these Hi-C features might result from
eruptions of sub-minifilaments (smaller than the minifilaments that
erupt to produce coronal jets). Comparisons with SDO's Helioseismic and
Magnetic Imager (HMI) magnetograms do not show magnetic mixed-polarity
neutral lines at these events' bases, as would be expected for true
scaled-down versions of solar filaments/minifilaments. But the features'
bases are all close to single-polarity strong-flux-edge locations,
suggesting possible local opposite-polarity flux unresolved by HMI. Or
it may be that our Hi-C ejections instead operate via the shock-wave
mechanism that is suggested to drive dynamic fibrils and the so-called
type I spicules.
Title: Early Results from the Solar-Minimum 2019 Total Solar Eclipse
Authors: Pasachoff, J. M.; Lockwood, C. A.; Inoue, J. L.; Meadors,
E. N.; Voulgaris, A.; Sliski, D.; Sliski, A.; Reardon, K. P.; Seaton,
D. B.; Caplan, R. M.; Downs, C.; Linker, J. A.; Sterling, A. C.
Bibcode: 2020AAS...23535903P
Altcode:
We report on first results from our observations in Chile on July
2, 2019, that revealed the extreme-solar-minimum corona, with only
equatorial streamers and with visible polar plumes. We have observations
in clear skies from our three observing sites: (1) The Cerro Tololo
Inter-American Observatory, 7,240-foot altitude, 2 min 6 sec; (2)
La Higuera, centerline, 2,500-foot altitude, 2 min 35 sec totality;
(3) La Serena, sea level, 2 min 15 sec totality. Prominences on the
limb provided orientation and coordination with spacecraft observations
from NOAA's GOES-R Solar Ultraviolet Imager (SUVI) and the Atmospheric
Imaging Assembly (AIA) on NASA's Solar Dynamics Observatory (SDO). The
double-diamond ring at second contact will extend our determination of
a new IAU-recommended value of the solar diameter through comparison
with models taking into account the precise lunar profile. Our coronal
spectra from slitless spectrographs, from CTIO, showed the Fe XIV 530.3
nm green line substantially weaker than the Fe X 637.4 nm red line,
corresponding to the relatively low coronal temperature at this phase
of the solar-activity cycle. On the spectra we also detected the weak
coronal emission line of Ar X at 553.3 nm, as we also detected at
the previous total solar eclipse of August 21, 2017, in the USA. We
show a comparison of the eclipse observation with a prediction of the
structure of the corona from an MHD model, carried out by Predictive
Science Inc. (PSI). We consider the lines of sight to NASA's Parker
Solar Probe at the times of total eclipses, when we can examine the
coronal imaging in terms of electron density to compare with the in
situ measurements. We received major support from grant AGS-903500
from the Solar Terrestrial Program, Atmospheric and Geospace Sciences
Division, U.S. National Science Foundation. The CTIO site was courtesy
of Associated Universities for Research in Astronomy (AURA). We had
additional student support from the Massachusetts NASA Space Grant
Consortium; Sigma Xi; the Global Initiatives Fund at Williams College;
and the University of Pennsylvania. PSI was supported by AFOSR, NASA,
and NSF. ACS received support from the NASA/HGI program, and from
the MSFC Hinode project. AV thanks the mathematician Christophoros
Mouratidis for his help with the data reduction of the spectra.
Title: Early results from the solar-minimum 2019 total solar eclipse
Authors: Pasachoff, Jay M.; Lockwood, Christian A.; Inoue, John L.;
Meadors, Erin N.; Voulgaris, Aristeidis; Sliski, David; Sliski, Alan;
Reardon, Kevin P.; Seaton, Daniel B.; Caplan, Ronald M.; Downs, Cooper;
Linker, Jon A.; Schneider, Glenn; Rojo, Patricio; Sterling, Alphonse C.
Bibcode: 2020IAUS..354....3P
Altcode:
We observed the 2 July 2019 total solar eclipse with a variety of
imaging and spectroscopic instruments recording from three sites
in mainland Chile: on the centerline at La Higuera, from the Cerro
Tololo Inter-American Observatory, and from La Serena, as well
as from a chartered flight at peak totality in mid-Pacific. Our
spectroscopy monitored Fe X, Fe XIV, and Ar X lines, and we imaged Ar
X with a Lyot filter adjusted from its original H-alpha bandpass. Our
composite imaging has been compared with predictions based on modeling
using magnetic-field measurements from the pre-eclipse month. Our
time-differenced sites will be used to measure motions in coronal
streamers.
Title: SunPy v1.0, the community-developed, free and open-source
solar data analysis environment for Python.
Authors: Christe, S.; Barnes, W. T.; Bobra, M.; Freij, N.; Hayes,
L.; Ireland, J.; Mumford, S.; Pérez-Suárez, D.; Ryan, D.; Shih,
A. Y.; Chanda, P.; Glogowski, S.; Hewett, R.; Hughitt, V. K.; Hill,
A.; Hiware, K.; Inglis, A.; Kirk, M. S.; Konge, S.; Mason, J. P.;
Maloney, S.; Park, J.; Pereira, T. J.; Reardon, K.; Savage, S. L.;
Yadav, T.; Taylor, G.; Stansby, D.; Jain, Y.; Sipocz, B.; Rajulapati,
C. R.; Panda, A.
Bibcode: 2019AGUFMSH41C3309C
Altcode:
The SunPy project facilitates and promotes the use and development
of several community-led, free, and open source data analysis
software packages for solar physics based on the scientific Python
environment. The project achieves this goal by developing and
maintaining the sunpy core package and supporting an ecosystem of
affiliated packages. The SunPy project is pleased to announce the 1.0
release of the sunpy package. This new release is the first stable
release of the packages and includes several important new features
such as improved data downloading capabilities, a large enhancement in
coordinate and coordinate transformations capabilities, new map utility
functions, and a new logging functionality amongst others. This talk
will present how the sunpy package can be used for solar data analysis
and discuss the roadmap for package.
Title: Solar Chromospheric Temperature Diagnostics: A Joint ALMA-Hα
Analysis
Authors: Molnar, Momchil E.; Reardon, Kevin P.; Chai, Yi; Gary, Dale;
Uitenbroek, Han; Cauzzi, Gianna; Cranmer, Steven R.
Bibcode: 2019ApJ...881...99M
Altcode: 2019arXiv190608896M
We present the first high-resolution, simultaneous observations of
the solar chromosphere in the optical and millimeter wavelength
ranges, obtained with the Atacama Large Millimeter Array (ALMA)
and the Interferometric Bidimensional Spectrometer at the Dunn Solar
Telescope. In this paper we concentrate on the comparison between the
brightness temperature observed in ALMA Band 3 (3 mm; 100 GHz) and the
core width of the Hα 6563 Å line, previously identified as a possible
diagnostic of the chromospheric temperature. We find that in the area
of plage, network and fibrils covered by our field of view, the two
diagnostics are well correlated, with similar spatial structures
observed in both. The strength of the correlation is remarkable,
given that the source function of the millimeter radiation obeys local
thermodynamic equilibrium, while the Hα line has a source function that
deviates significantly from the local Planck function. The observed
range of ALMA brightness temperatures is sensibly smaller than the
temperature range that was previously invoked to explain the observed
width variations in Hα. We employ analysis from forward modeling
with the Rybicki-Hummer (RH) code to argue that the strong correlation
between Hα width and ALMA brightness temperature is caused by their
shared dependence on the population number n 2 of the first
excited level of hydrogen. This population number drives millimeter
opacity through hydrogen ionization via the Balmer continuum, and
Hα width through a curve-of-growth-like opacity effect. Ultimately,
the n 2 population is regulated by the enhancement or lack
of downward Lyα flux, which coherently shifts the formation height
of both diagnostics to regions with different temperature, respectively.
Title: Disentangling Chromospheric Temperatures and Dynamics with
ALMA and IBIS
Authors: Reardon, Kevin P.; Molnar, Momchil; Chai, Yi; Hofmann, Ryan
Bibcode: 2019AAS...23431103R
Altcode:
The chromosphere is highly structured in density, dynamics, and
temperature. Unfortunately, it can be difficult to disentangle the
different contributions of these physical conditions to our current
set of observable diagnostics. With the advent of high-resolution
observations of the millimeter continuum with the Atacama Large
Millimeter Array (ALMA), we have a new tool to probe the chromospheric
temperature structure. By combining these observations with similar
observations in other visible, infrared, and UV lines, we are
better able to disentangle the thermal and dynamical behavior of the
chromosphere. In this talk, we discuss the results of combining ALMA
images with imaging spectroscopy from the Interferometric Bidimensional
Spectrometer (IBIS). We find evidence that spectral-line parameters
of Hα and Ca II are closely correlated with the ALMA brightness
temperatures. We have performed spectral inversions employing multiple
diagnostics to retrieve typical atmospheric conditions in our field of
view. We discuss how this joint analysis changes our understanding of
chromospheric dynamics and the interpretation of the observed spectral
intensities. Finally, we explore how these results can guide future
observations of the chromosphere from both ALMA and DKIST.
Title: New technique to measure the cavity defects of Fabry-Perot
interferometers
Authors: Greco, V.; Sordini, A.; Cauzzi, G.; Reardon, K.; Cavallini, F.
Bibcode: 2019A&A...626A..43G
Altcode: 2019arXiv190501393G
Context. Several astronomical instruments, for both nighttime and
solar use, rely on tunable Fabry-Perot interferometers (FPIs). Knowing
the exact shape of the etalons' cavity is crucial for assessing the
overall instrumental transmission profile and its possible variations
during the tuning process.
Aims: We aim to define and test
a technique to accurately measure the cavity defects of air-spaced
FPIs, including distortions due to the spectral tuning process that
are typical of astronomical observations. We further aim to develop a
correction technique to maintain the shape of the cavity as constant as
possible during the spectral scan. These are necessary steps to optimize
the spectral transmission profile of a two-dimensional spectrograph
(polarimeter) using one or more FPIs in series, and to ensure that
the spectral transmission profile remains constant during typical
observing conditions.
Methods: We devised a generalization of the
techniques developed for the so-called phase-shifting interferometry to
the case of FPI. This measuring technique is applicable to any given FPI
that can be tuned via changing the cavity spacing (z-axis), and can be
used for any etalon regardless of the coating' reflectivity. The major
strength of our method is the ability to fully characterize the cavity
during a spectral scan, allowing for the determination of scan-dependent
modifications of the plates. We have applied the measuring technique to
three 50 mm diameter interferometers, with cavity gaps ranging between
600 μm and 3 mm, coated for use in the visible range.
Results:
The technique developed in this paper allows us to accurately and
reliably measure the cavity defects of air-spaced FPIs, and of their
evolution during the entire spectral scan. Our main, and unexpected,
result is that the relative tilt between the two FPI plates varies
significantly during the spectral scan, and can dominate the cavity
defects; in particular, we observe that the tilt component at the
extremes of the scan is sensibly larger than that at the center of
the scan. Exploiting the capability of the electronic controllers to
set the reference plane at any given spectral step, we then develop
a correction technique that allows the minimization of the tilt
during a complete spectral scan. The correction remains highly stable
over long periods, well beyond the typical duration of astronomical
observations. Movies attached to Figs. 6 and 13 are available at https://www.aanda.org
Title: Propagation and Coupling of Waves between the Photosphere
and Chromosphere in the Presence of Sunspots
Authors: Stauffer, Johnathan; Reardon, Kevin
Bibcode: 2019shin.confE.126S
Altcode:
Understanding the propagation of plasma waves through the solar
atmosphere is an important part of constraining the energy budget
which must give rise to coronal and chromospheric heating. In this
study, we examine how the behavior of waves traveling between the
solar phosophere and chromosphere are modulated by the presence of two
sunspot regions: an isolated sunspot without a penumbra, and a complex,
multi-spot active region (NOAA AR 11158). Using the Interferometric
BIdimensional Spectropolarimeter (IBIS) at the Dunn Solar Telescope
(DST), these regions were observed in the continuum and in three
spectral lines (Na 5896 Å, Fe 7090 Å, and Ca 8542 Å) chosen to span
the photosphere and chromosphere. In addition, these regions were
simultaneously observed in the molecular CO lines at 4.65 µm using
the by the McMath-Pierce telescope at Kitt Peak Observatory. Together,
these data mark the first time that these CO molecular lines have
been observed simultaneously with other chromospheric and photospheric
spectral lines in high spatial and temporal resolution. These molecular
lines are indicative of cool plasma in the lower chromosphere, and
allow us to probe the thermal structure of the atmosphere in the
presence of these propagating waves. The correspondence of the cool
pockets observed with CO with other chromospheric structures can also
be compared with MHD models of similar regions in order to test the
ability of these models to replicate the temperature structure of
the solar atmosphere. In the future, the results presented here may
inform future observations from DKIST, which will be able to observe
these CO lines in unprecedented spatial and spectral resolution with
the Cryogenic Near-Infrared Spectro-Polarimeter (Cryo-NIRSP).
Title: High frequency chromospheric observations with IBIS and ALMA
Authors: Molnar, Momchil Emil; Reardon, Kevin; Cranmer, Steven
Bibcode: 2019shin.confE.148M
Altcode:
The heating mechanism sustaining the quiet chromosphere is still
unknown and is an area of active research (Kalkofen 2007). A possible
explanation for the chromospheric heating conundrum is the dissipation
of high-frequency waves permeating the chromosphere. However, there
are few studies of this frequency regime (above 30 mHz) with full
spectral scanning to derive proper Doppler velocity fields in the
chromosphere. We present observations of the power spectrum of the
Doppler velocities in the chromosphere from the DST at Sunspot, NM. We
used the IBIS instrument with a novel reduction technique to derive
chromospheric Doppler velocities in the spectral lines of H-alpha and Ca
II 8542 with cadences of about 3.5 seconds for a full spectral scan. We
find that the power spectrum of the measured velocities follow a power
law ubiquitous in our field of view up to 60 mHz. The power law index
is coherent for similar chromospheric regions. We find comparable power
law in the power spectrum of the temperature variation in simultaneous
observations with ALMA of the same region. This power law could be a
signature of turbulent cascade leading to the dissipation of energy of
these high frequency perturbations at small scales. However, this is
an unexpected result as the extended formation region of these resonant
chromospheric lines smears out the spectral signatures produced by short
wavelength perturbations in the atmosphere. To explain the presence of
high-frequency energy in the power spectra we study the transmission
function of the wave perturbations through the solar atmosphere with
the RH code. This exploratory study could be greatly improved with the
DKI Solar Telescope, which would enable us to resolve smaller scales
in the solar atmosphere as well as measure velocities at higher cadence
and better precision.
Title: The DKI Solar Telescope
Authors: Reardon, Kevin
Bibcode: 2019shin.confE.232R
Altcode:
The DKI Solar Telescope (DKIST) will begin initial scientific
operations in the summer of 2020. It is designed to perform, in part,
as a coronagraph, taking detailed images and spectra of the low solar
corona. Given the four-meter aperture, excellent coronagraphic site,
and broad range of diagnostics, it will be a transformational facility,
permitting detailed studies of the velocities, magnetic field, and
fine-scale structuring of the off-limb corona. I will describe the
observational capabilities of DKIST, especially related to coronal
diagnostics. I will then review some the techniques that can be used
to process and analyze the DKIST data stream. I will show examples
of techniques for image reconstruction, used to improve the spatial
resolution of the recorded data, and for extracting useful information
from time-series data cubes.
Title: Solar Ultraviolet Bursts
Authors: Young, Peter R.; Tian, Hui; Peter, Hardi; Rutten, Robert J.;
Nelson, Chris J.; Huang, Zhenghua; Schmieder, Brigitte; Vissers, Gregal
J. M.; Toriumi, Shin; Rouppe van der Voort, Luc H. M.; Madjarska, Maria
S.; Danilovic, Sanja; Berlicki, Arkadiusz; Chitta, L. P.; Cheung, Mark
C. M.; Madsen, Chad; Reardon, Kevin P.; Katsukawa, Yukio; Heinzel, Petr
Bibcode: 2018SSRv..214..120Y
Altcode: 2018arXiv180505850Y
The term "ultraviolet (UV) burst" is introduced to describe small,
intense, transient brightenings in ultraviolet images of solar active
regions. We inventorize their properties and provide a definition
based on image sequences in transition-region lines. Coronal signatures
are rare, and most bursts are associated with small-scale, canceling
opposite-polarity fields in the photosphere that occur in emerging flux
regions, moving magnetic features in sunspot moats, and sunspot light
bridges. We also compare UV bursts with similar transition-region
phenomena found previously in solar ultraviolet spectrometry and
with similar phenomena at optical wavelengths, in particular Ellerman
bombs. Akin to the latter, UV bursts are probably small-scale magnetic
reconnection events occurring in the low atmosphere, at photospheric
and/or chromospheric heights. Their intense emission in lines with
optically thin formation gives unique diagnostic opportunities
for studying the physics of magnetic reconnection in the low solar
atmosphere. This paper is a review report from an International Space
Science Institute team that met in 2016-2017.
Title: Modeling wave energy transport using a 3D MHD simulation
of AR12683
Authors: Tarr, Lucas; Linton, Mark; Reardon, Kevin; Shetye, Juie;
Verwichte, Erwin
Bibcode: 2018tess.conf20544T
Altcode:
We use the 3D Magnetohydrodynamic code LARE to model wave transport
within NOAA Active Region 12683. The simulation extends vertically
from the photosphere to the low corona and includes gravitational
stratification and a steep transition region to a high temperature
corona. AR12683 consists of a leading negative polarity sunspot
followed by an extended region of plage, and had little X-ray
activity during the time period we study. Given that, we use a
potential field, extrapolated from HMI data, for the initial 3D
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</use> </g> </svg> observations taken with the Goode
Solar Telescope at Big Bear Solar Observatory revealed interesting
propagating disturbances near the sunspot, which will be reported
on elsewhere. In this work, we focus on the general properties of
wave propagation through the region by introducing compressive wave
packets at the lower boundary, mimicking convective forcing. We then
use the techniques developed in Tarr, Linton, & Leake, ApJ 2017,
to track wave energy, mode conversion, and shock formation as the wave
packets propagate through the simulation. By varying the wave packet
injection location, we can isolate photospheric source locations for
disturbances seen higher up in the chromosphere and low corona, and
understand the important role of mode conversion in the transfer of
wave energy throughout the realistically structured atmosphere.
Title: Absorption Spectroscopy of Mercury's Exosphere During the
2016 Solar Transit
Authors: Schmidt, C. A.; Leblanc, F.; Reardon, K.; Killen, R. M.;
Gary, D. E.; Ahn, K.
Bibcode: 2018LPICo2047.6022S
Altcode:
Solar transits of Mercury provide a rare opportunity to study the
exosphere in absorption and a valuable analog to transiting exoplanet
studies. This presentation will characterize the sodium exosphere
during the 2016 transit.
Title: SunPy: Python for Solar Physics
Authors: Bobra, M.; Inglis, A. R.; Mumford, S.; Christe, S.; Freij,
N.; Hewett, R.; Ireland, J.; Martinez Oliveros, J. C.; Reardon, K.;
Savage, S. L.; Shih, A. Y.; Pérez-Suárez, D.
Bibcode: 2017AGUFMSH51C2508B
Altcode:
SunPy is a community-developed open-source software library for
solar physics. It is written in Python, a free, cross-platform,
general-purpose, high-level programming language which is being
increasingly adopted throughout the scientific community. SunPy aims to
provide the software for obtaining and analyzing solar and heliospheric
data. This poster introduces a new major release, SunPy version 0.8. The
first major new feature introduced is Fido, the new primary interface to
download data. It provides a consistent and powerful search interface
to all major data providers including the VSO and the JSOC, as well as
individual data sources such as GOES XRS time series. It is also easy
to add new data sources as they become available, i.e. DKIST. The
second major new feature is the SunPy coordinate framework. This
provides a powerful way of representing coordinates, allowing simple
and intuitive conversion between coordinate systems and viewpoints of
different instruments (i.e., Solar Orbiter and the Parker Solar Probe),
including transformation to astrophysical frames like ICRS. Other new
features including new timeseries capabilities with better support
for concatenation and metadata, updated documentation and example
gallery. SunPy is distributed through pip and conda and all of its
code is publicly available (sunpy.org).
Title: SunPy 0.8 - Python for Solar Physics
Authors: Inglis, Andrew; Bobra, Monica; Christe, Steven; Hewett,
Russell; Ireland, Jack; Mumford, Stuart; Martinez Oliveros, Juan
Carlos; Perez-Suarez, David; Reardon, Kevin P.; Savage, Sabrina;
Shih, Albert Y.; Ryan, Daniel; Sipocz, Brigitta; Freij, Nabil
Bibcode: 2017SPD....4811506I
Altcode:
SunPy is a community-developed open-source software library for
solar physics. It is written in Python, a free, cross-platform,
general-purpose, high-level programming language which is being
increasingly adopted throughout the scientific community. Python is
one of the top ten most often used programming languages, as such
it provides a wide array of software packages, such as numerical
computation (NumPy, SciPy), machine learning (scikit-learn), signal
processing (scikit-image, statsmodels) to visualization and plotting
(matplotlib, mayavi). SunPy aims to provide the software for obtaining
and analyzing solar and heliospheric data. This poster introduces
a new major release of SunPy (0.8). This release includes two major
new functionalities, as well as a number of bug fixes. It is based on
1120 contributions from 34 unique contributors. Fido is the new primary
interface to download data. It provides a consistent and powerful search
interface to all major data sources provides including VSO, JSOC, as
well as individual data sources such as GOES XRS time series and and is
fully pluggable to add new data sources, i.e. DKIST. In anticipation of
Solar Orbiter and the Parker Solar Probe, SunPy now provides a powerful
way of representing coordinates, allowing conversion between coordinate
systems and viewpoints of different instruments, including preliminary
reprojection capabilities. Other new features including new timeseries
capabilities with better support for concatenation and metadata, updated
documentation and example gallery. SunPy is distributed through pip
and conda and all of its code is publicly available (sunpy.org).
Title: Exploratory study of the chromosphere with ALMA
Authors: Molnar, Momchil E.; Reardon, Kevin
Bibcode: 2017shin.confE.163M
Altcode:
We will present an exploratory study of the dynamics of the
chromospheric network and internetwork with the Atacama Large
Milimeter/submilimeter Array (ALMA). ALMA is an interferometric array
of sixty six 12-meter and 7-meter dishes in Chile, which recently
started observing the Sun. The radiation detected with ALMA is formed
through free-free emission in the chromosphere and can be interpreted
as brightness temperature. The ALMA observations were conducted on
the 23rd April 2017 simultaneously with the support of the DST (IBIS,
ROSA and FIRS instruments), IRIS and Hinode. Using the unprecedented
high cadence ( 2 seconds) and high angular resolution of the ALMA
observations we can study in detail the heating mechanisms in the
chromosphere, including the role of steepening acoustic waves. We will
present preliminary results from our observations of the shock-driven
turbulence in the chromosphere, as we extend previous work by Reardon
et al. (2008) up to higher frequencies and new diagnostics.
Title: Absorption by Mercury's Exosphere During the May 9th, 2016
Solar Transit.
Authors: Schmidt, C.; Reardon, K.; Killen, R. M.; Gary, D. E.; Ahn, K.;
Leblanc, F.; Baumgardner, J. L.; Mendillo, M.; Beck, C.; Mangano, V.
Bibcode: 2016AGUFM.P53B2198S
Altcode:
Observations of Mercury during a solar transit have the unique property
that line absorption may be used to retrieve the exosphere's column
density at all points above the terminator simultaneously. We report
on measurements during the 9 May 2016 transit with the Dunn Solar
Telescope (Interferometric BIdimensional Spectropolarimeter: IBIS &
Horizontal Spectrograph: HSG) and the Big Bear Solar Observatory (Fast
Imaging Solar Spectrograph: FISS). The sodium exosphere was observed
via Fabry-Perot imaging with IBIS in 9 mA increments, and with FISS at
a dispersion of 17 mA/pixel by scanning the spectrograph slit over the
planet's disk. A search for potassium D line absorption was performed
using slit spectroscopy with HSG at a resolution of R 270,000. In each
instrument, exposures of 20-40 ms and adaptive optics enable spatial
structure to be resolved on sub-arcsecond scales. The line profiles at
every spatial bin are divided by a shifted and scaled reference spectrum
in order to isolate the exosphere's absorption from line absorption in
the solar atmosphere and structures inherent to granulation. Analysis
of these data sets is ongoing, but preliminary findings clearly show
the densest column of sodium near the poles and the content at dawn
enhanced several times with respect to dusk. Such is consistent with
2003 transit results taken at the same Mercury season (Schleicher et
al., 2004), however the data volumes herein permit a more in-depth
study in which time-dependence of the exosphere may be considered.
Title: The DKIST Data Center: Meeting the Data Challenges for
Next-Generation, Ground-Based Solar Physics
Authors: Davey, A. R.; Reardon, K.; Berukoff, S. J.; Hays, T.; Spiess,
D.; Watson, F. T.; Wiant, S.
Bibcode: 2016AGUFMSH34A..04D
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST) is under construction
on the summit of Haleakalā in Maui, and scheduled to start
science operations in 2020. The DKIST design includes a four-meter
primary mirror coupled to an adaptive optics system, and a flexible
instrumentation suite capable of delivering high-resolution optical
and infrared observations of the solar chromosphere, photosphere, and
corona. Through investigator-driven science proposals, the facility
will generate an average of 8 TB of data daily, comprised of millions
of images and hundreds of millions of metadata elements. The DKIST Data
Center is responsible for the long-term curation and calibration of data
received from the DKIST, and for distributing it to the user community
for scientific use. Two key elements necessary to meet the inherent
big data challenge are the development of flexible public/private
cloud computing and coupled relational and non-relational data storage
mechanisms. We discuss how this infrastructure is being designed to
meet the significant expectation of automatic and manual calibration of
ground-based solar physics data, and the maximization the data's utility
through efficient, long-term data management practices implemented
with prudent process definition and technology exploitation.
Title: Solar dynamics imaging system a back-end instrument for the
proposed NLST
Authors: Ramesh, K. B.; Vasantharaju, N.; Pruthvi, H.; Reardon, K.
Bibcode: 2016ExA....42..271R
Altcode: 2016ExA...tmp...24R
The Solar Dynamics Imaging System (SDIS) will be one of the focal
plane instruments operated at the National Large Solar Telescope
(NLST). The prime objective of the instrument is to obtain high
spatial and temporal resolution images of the region of interest on the
Sun in the wavelength range from 390 nm to 900 nm. The SDIS provides
filtergrams using broad-band filters while preserving the Strehl ratio
provided by the telescope. Furthermore, the SDIS is expected to provide
observations that allow image reconstruction to extract wave front
information and achieve a homogenous image quality over the entire FOV.
Title: The 2016 Transit of Mercury Observed from Major Solar
Telescopes and Satellites
Authors: Pasachoff, Jay M.; Schneider, Glenn; Gary, Dale; Chen, Bin;
Sterling, Alphonse C.; Reardon, Kevin P.; Dantowitz, Ronald; Kopp,
Greg A.
Bibcode: 2016DPS....4811705P
Altcode:
We report observations from the ground and space of the 9 May 2016
transit of Mercury. We build on our explanation of the black-drop
effect in transits of Venus based on spacecraft observations of the 1999
transit of Mercury (Schneider, Pasachoff, and Golub, Icarus 168, 249,
2004). In 2016, we used the 1.6-m New Solar Telescope at the Big Bear
Solar Observatory with active optics to observe Mercury's transit at
high spatial resolution. We again saw a small black-drop effect as 3rd
contact neared, confirming the data that led to our earlier explanation
as a confluence of the point-spread function and the extreme solar
limb darkening (Pasachoff, Schneider, and Golub, in IAU Colloq. 196,
2004). We again used IBIS on the Dunn Solar Telescope of the Sacramento
Peak Observatory, as A. Potter continued his observations, previously
made at the 2006 transit of Mercury, at both telescopes of the sodium
exosphere of Mercury (Potter, Killen, Reardon, and Bida, Icarus 226,
172, 2013). We imaged the transit with IBIS as well as with two RED
Epic IMAX-quality cameras alongside it, one with a narrow passband. We
show animations of our high-resolution ground-based observations along
with observations from XRT on JAXA's Hinode and from NASA's Solar
Dynamics Observatory. Further, we report on the limit of the transit
change in the Total Solar Irradiance, continuing our interest from
the transit of Venus TSI (Schneider, Pasachoff, and Willson, ApJ 641,
565, 2006; Pasachoff, Schneider, and Willson, AAS 2005), using NASA's
SORCE/TIM and the Air Force's TCTE/TIM. See http://transitofvenus.info
and http://nicmosis.as.arizona.edu.Acknowledgments: We were glad for
the collaboration at Big Bear of Claude Plymate and his colleagues of
the staff of the Big Bear Solar Observatory. We also appreciate the
collaboration on the transit studies of Robert Lucas (Sydney, Australia)
and Evan Zucker (San Diego, California). JMP appreciates the sabbatical
hospitality of the Division of Geosciences and Planetary Sciences of
the California Institute of Technology, and of Prof. Andrew Ingersoll
there. The solar observations lead into the 2017 eclipse studies,
for which JMP is supported by grants from the NSF AGS and National
Geographic CRE.
Title: Petascale cyberinfrastructure for ground-based solar physics:
approach of the DKIST data center
Authors: Berukoff, S.; Hays, T.; Reardon, K.; Spiess, DJ; Watson,
F.; Wiant, S.
Bibcode: 2016SPIE.9913E..1FB
Altcode:
The Daniel K Inouye Solar Telescope, under construction in Maui,
is designed to perform high-resolution spectropolarimetric visible
and infrared measurements of the Sun, and will annually produce 3 PB
of data, via 5x108 images and 2x1011 metadata
elements requiring calibration, long-term data management, and open and
free distribution. After briefly describing the DKIST and its instrument
suite, we provide an overview of functions that the DKIST Data Center
will provide, and focus on major challenges in its development. We
conclude by discussing approach and mention some technologies that
the Data Center team is using to develop a petascale computational
and data storage resource to support this unique world-class DKIST
facility and support its long-term scientific and operational goals.
Title: Tracing the Chromospheric and Coronal Magnetic Field with AIA,
IRIS, IBIS, and ROSA Data
Authors: Aschwanden, Markus J.; Reardon, Kevin; Jess, Dave B.
Bibcode: 2016ApJ...826...61A
Altcode: 2016arXiv160202119A
The aim of this study is to explore the suitability of
chromospheric images for magnetic modeling of active regions. We
use high-resolution images (≈ 0\buildrel{\prime\prime}\over{.}
2{--}0\buildrel{\prime\prime}\over{.} 3), from the Interferometric
Bidimensional Spectrometer in the Ca II 8542 Å line, the Rapid
Oscillations in the Solar Atmosphere instrument in the Hα 6563 Å
line, the Interface Region Imaging Spectrograph in the 2796 Å line,
and compare non-potential magnetic field models obtained from those
chromospheric images with those obtained from images of the Atmospheric
Imaging Assembly in coronal (171 Å, etc.) and in chromospheric (304
Å) wavelengths. Curvi-linear structures are automatically traced in
those images with the OCCULT-2 code, to which we forward-fitted magnetic
field lines computed with the Vertical-current Approximation Nonlinear
Force Free Field code. We find that the chromospheric images: (1)
reveal crisp curvi-linear structures (fibrils, loop segments, spicules)
that are extremely well-suited for constraining magnetic modeling; (2)
that these curvi-linear structures are field-aligned with the best-fit
solution by a median misalignment angle of {μ }2≈ 4^\circ
-7° (3) the free energy computed from coronal data may underestimate
that obtained from cromospheric data by a factor of ≈ 2-4, (4) the
height range of chromospheric features is confined to h≲ 4000 km,
while coronal features are detected up to h = 35,000 km; and (5) the
plasma-β parameter is β ≈ {10}-5{--}{10}-1
for all traced features. We conclude that chromospheric images reveal
important magnetic structures that are complementary to coronal
images and need to be included in comprehensive magnetic field models,
something that is currently not accomodated in standard NLFFF codes.
Title: Calibration development strategies for the Daniel K. Inouye
Solar Telescope (DKIST) data center
Authors: Watson, Fraser T.; Berukoff, Steven J.; Hays, Tony; Reardon,
Kevin; Speiss, Daniel J.; Wiant, Scott
Bibcode: 2016SPIE.9910E..1GW
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST), currently under
construction on Haleakalā, in Maui, Hawai'i will be the largest solar
telescope in the world and will use adaptive optics to provide the
highest resolution view of the Sun to date. It is expected that DKIST
data will enable significant and transformative discoveries that will
dramatically increase our understanding of the Sun and its effects on
the Sun-Earth environment. As a result of this, it is a priority of
the DKIST Data Center team at the National Solar Observatory (NSO)
to be able to deliver timely and accurately calibrated data to the
astronomical community for further analysis. This will require a process
which allows the Data Center to develop calibration pipelines for all of
the facility instruments, taking advantage of similarities between them,
as well as similarities to current generation instruments. There will
also be a challenges which are addressed in this article, such as the
large volume of data expected, and the importance of supporting both
manual and automated calibrations. This paper will detail the current
calibration development strategies being used by the Data Center team at
the National Solar Observatory to manage this calibration effort, so as
to ensure delivery of high quality scientific data routinely to users.
Title: Calibration development strategies for the Daniel K. Inouye
Solar Telescope (DKIST) Data Center
Authors: Watson, Fraser; Reardon, Kevin P.; Berukoff, Steven J.;
Hays, Tony; Wiant, Scott; Spiess, DJ
Bibcode: 2016SPD....4730902W
Altcode:
As telescopes have grown larger and data rates have increased, so have
the challenges in providing reliable and accurate calibration strategies
for transforming raw data into useful science-ready outputs. The
Daniel K. Inouye Solar Telescope (DKIST) will be the largest solar
telescope in the world and will use adaptive optics to provide the
highest resolution view of the Sun. Its data acquisition rates will
be in the hundreds of thousands of frames per day, and it will deliver
an average of 12TB of raw solar data on a daily basis. DKIST data will
enable significant and transformative discoveries that will dramatically
increase our understanding of the Sun and its effects on the Sun-Earth
environment. As such, it is a priority of the DKIST Data Center team at
the National Solar Observatory (NSO) to be able to deliver timely and
accurately calibrated data to the astronomical community for further
analysis.The facility will execute a variety of investigator-driven
observing programs, which will produce day-to-day variations in
the types of acquired data. In combination with large data rates
and limited personnel, this will require some degree of automation
to be incorporated into the calibration workflows to facilitate
the generation of scientifically useful data. The heterogeneity of
the data and the unpredictable variations in the seeing conditions
(on timescales of seconds or minutes) introduce complexity, which
requires a self-adapting, extensible calibration pipeline to provide
sufficient automation to the process. Our knowledge of the instrument
performance and telescope characteristics will grow as the telescope
begins operations, and continuously through the facility lifetime. The
automated calibration pipelines will be capable of modification
and improvement to incorporate the new information about the DKIST
system, as well as potential improvements provided by the DKIST user
community.This poster will detail the calibration development strategies
being used by the Data Center team at the NSO to manage this calibration
effort, in order to deliver timely and accurately calibrated data to
the DKIST user community, with as much scientific value as possible.
Title: Construction Status and Early Science with the Daniel K. Inouye
Solar Telescope
Authors: McMullin, Joseph P.; Rimmele, Thomas R.; Warner, Mark;
Martinez Pillet, Valentin; Craig, Simon; Woeger, Friedrich; Tritschler,
Alexandra; Berukoff, Steven J.; Casini, Roberto; Goode, Philip R.;
Knoelker, Michael; Kuhn, Jeffrey Richard; Lin, Haosheng; Mathioudakis,
Mihalis; Reardon, Kevin P.; Rosner, Robert; Schmidt, Wolfgang
Bibcode: 2016SPD....4720101M
Altcode:
The 4-m Daniel K. Inouye Solar Telescope (DKIST) is in its seventh
year of overall development and its fourth year of site construction
on the summit of Haleakala, Maui. The Site Facilities (Utility
Building and Support & Operations Building) are in place with
ongoing construction of the Telescope Mount Assembly within. Off-site
the fabrication of the component systems is completing with early
integration testing and verification starting.Once complete this
facility will provide the highest sensitivity and resolution for study
of solar magnetism and the drivers of key processes impacting Earth
(solar wind, flares, coronal mass ejections, and variability in solar
output). The DKIST will be equipped initially with a battery of first
light instruments which cover a spectral range from the UV (380 nm)
to the near IR (5000 nm), and capable of providing both imaging and
spectro-polarimetric measurements throughout the solar atmosphere
(photosphere, chromosphere, and corona); these instruments are being
developed by the National Solar Observatory (Visible Broadband Imager),
High Altitude Observatory (Visible Spectro-Polarimeter), Kiepenheuer
Institute (Visible Tunable Filter) and the University of Hawaii
(Cryogenic Near-Infrared Spectro-Polarimeter and the Diffraction-Limited
Near-Infrared Spectro-Polarimeter). Further, a United Kingdom consortium
led by Queen's University Belfast is driving the development of high
speed cameras essential for capturing the highly dynamic processes
measured by these instruments. Finally, a state-of-the-art adaptive
optics system will support diffraction limited imaging capable of
resolving features approximately 20 km in scale on the Sun.We present
the overall status of the construction phase along with the current
challenges as well as a review of the planned science testing and the
transition into early science operations.
Title: Challenges and Rewards in Ground-Based Observing
Authors: Reardon, Kevin P.
Bibcode: 2016SPD....4740802R
Altcode:
DKIST will be largest ground-based project in solar physics, and
will offer access and data to the whole community. In pursuit of
exciting science, many users may have their first encounters with
high-resolution, ground-based solar observations. New facilities, space
or ground-based, all bring particular signatures in their data. While
tools or processed datasets might serve to minimize such non-solar
signatures, it is nonetheless important for users to understand the
impacts on observation planning, the nature of the corrections applied,
and any residual effects on their data.In this talk I will review some
of the instrumental and atmospheric signatures that are important for
ground-based observing, in particular in planning for the potential
capabilities of the DKIST Data Center. These techniques include image
warping, local PSF deconvolution, atmospheric dispersion correction,
and scattered light removal. I will present examples of data sets
afflicted by such problems as well as some of the algorithms used in
characterizing and removing these contributions. This will demonstrate
how even with the challenges of observing through a turbulent
atmosphere, it is possible to achieve dramatic scientific results.
Title: Petascale Computing for Ground-Based Solar Physics with the
DKIST Data Center
Authors: Berukoff, Steven J.; Hays, Tony; Reardon, Kevin P.; Spiess,
DJ; Watson, Fraser; Wiant, Scott
Bibcode: 2016SPD....4720502B
Altcode:
When construction is complete in 2019, the Daniel K. Inouye Solar
Telescope will be the most-capable large aperture, high-resolution,
multi-instrument solar physics facility in the world. The telescope
is designed as a four-meter off-axis Gregorian, with a rotating Coude
laboratory designed to simultaneously house and support five first-light
imaging and spectropolarimetric instruments. At current design, the
facility and its instruments will generate data volumes of 3 PB per
year, and produce 107-109 metadata elements.The
DKIST Data Center is being designed to store, curate, and process this
flood of information, while providing association of science data
and metadata to its acquisition and processing provenance. The Data
Center will produce quality-controlled calibrated data sets, and make
them available freely and openly through modern search interfaces and
APIs. Documented software and algorithms will also be made available
through community repositories like Github for further collaboration and
improvement.We discuss the current design and approach of the DKIST Data
Center, describing the development cycle, early technology analysis
and prototyping, and the roadmap ahead. We discuss our iterative
development approach, the underappreciated challenges of calibrating
ground-based solar data, the crucial integration of the Data Center
within the larger Operations lifecycle, and how software and hardware
support, intelligently deployed, will enable high-caliber solar physics
research and community growth for the DKIST's 40-year lifespan.
Title: Next-generation solar data and data services from the Daniel
K. Inouye Solar Telescope
Authors: Berukoff, S.; Reardon, K.; Rimmele, T.
Bibcode: 2015ASPC..495...91B
Altcode: 2015adass..24...91B
The Daniel K. Inouye Solar Telescope (DKIST), when completed, will
be the largest, most capable solar telescope in the world. Currently
under construction on the summit of Haleakala on Maui, the DKIST will
enable foundational insights into the physics of the Sun's photosphere,
chromosphere, and corona. Its suite of first-light instruments will
produce approximately 25TB of raw and processed data per day, with
bursts up to 50TB. These data rates will require a scalable, flexible
data and computing architecture that enables and promotes inquiry and
discovery. We describe the challenges faced by managing DKIST data
and provide an overview of the proposed data center architecture
and resources that will allow users to fully exploit this unique
world-class facility.
Title: Daniel K. Inouye Solar Telescope: Overview and Status
Authors: Rimmele, Thomas; McMullin, Joseph; Warner, Mark; Craig,
Simon; Woeger, Friedrich; Tritschler, Alexandra; Cassini, Roberto;
Kuhn, Jeff; Lin, Haosheng; Schmidt, Wolfgang; Berukoff, Steve; Reardon,
Kevin; Goode, Phil; Knoelker, Michael; Rosner, Robert; Mathioudakis,
Mihalis; DKIST TEAM
Bibcode: 2015IAUGA..2255176R
Altcode:
The 4m Daniel K. Inouye Solar Telescope (DKIST) currently under
construction on Haleakala, Maui will be the world’s largest solar
telescope. Designed to meet the needs of critical high resolution and
high sensitivity spectral and polarimetric observations of the sun,
this facility will perform key observations of our nearest star that
matters most to humankind. DKIST’s superb resolution and sensitivity
will enable astronomers to unravel many of the mysteries the Sun
presents, including the origin of solar magnetism, the mechanisms of
coronal heating and drivers of the solar wind, flares, coronal mass
ejections and variability in solar output. The all-reflecting, off-axis
design allows the facility to observe over a broad wavelength range and
enables DKIST to operate as a coronagraph. In addition, the photon flux
provided by its large aperture will be capable of routine and precise
measurements of the currently elusive coronal magnetic fields. The
state-of-the-art adaptive optics system provides diffraction limited
imaging and the ability to resolve features approximately 20 km on
the Sun. Five first light instruments, representing a broad community
effort, will be available at the start of operations: Visible Broadband
Imager (National Solar Observatory), Visible Spectro-Polarimeter (High
Altitude Observatory), Visible Tunable Filter (Kiepenheuer Institute,
Germany), Diffraction Limited NIR Spectro-Polarimeter (University
of Hawaii) and the Cryogenic NIR Spectro-Polarimeter (University of
Hawaii). High speed cameras for capturing highly dynamic processes
in the solar atmosphere are being developed by a UK consortium. Site
construction on Haleakala began in December 2012 and is progressing
on schedule. Operations are scheduled to begin in 2019. We provide an
overview of the facility, discuss the construction status, and present
progress with DKIST operations planning.
Title: Science-Ready Data Production in the DKIST Data Center
Authors: Reardon, Kevin; Berukoff, Steven; Hays, Tony; Spiess, DJ;
Watson, Fraser
Bibcode: 2015IAUGA..2258326R
Altcode:
The NSO's new flagship solar observatory, the four-meter Daniel
K. Inouye Solar Telescope is under construction on Halekalala, Hawaii
and slated for first light in 2019. The facility will operate an initial
suite of five complementary spectroscopic and polarimetric instruments,
with up to 11 detectors running simultaneously at typical cadences of
5-30 frames per second, or more. The instruments will generate data
of notable volume, dimensionality, cardinality, and diversity. The
facility is expected to record several hundred million images per year,
for a total data volume in excess of 4 petabytes.Beyond the crucial
informatics infrastructure necessary to transport, store, and curate
this deluge of data, there are significant challenges in developing the
robust calibration workflows that can autonomously process the range of
data to generate science-ready datasets for a heterogeneous and growing
community. Efforts will be made to improve our ability to compensate for
the effects of the Earth's atmosphere, to identify and assess instrument
and facility contributions to the measured signal, and to use of quality
and fitness-of-use metrics to characterize and advertise datasets.In
this talk, we will provide an overview of the methods and tools we
are using to define and evaluate the calibration workflows. We will
review the type of datasets that may be made available to scientists at
the time of the initial operations of DKIST, as well as the potential
mechanisms for the search and delivery of those data products. We will
also suggest some of the likely secondary data products that could
possibly be developed successively in collaboration with the community.
Title: Building Petascale Cyberinfrastructure and Science Support
for Solar Physics: Approach of the DKIST Data Center
Authors: Berukoff, Steven; Reardon, Kevin; Hays, Tony; Spiess, DJ;
Watson, Fraser
Bibcode: 2015IAUGA..2257546B
Altcode:
When construction is complete in 2019, the Daniel K. Inouye Solar
Telescope will be the most-capable large aperture, high-resolution,
multi-instrument solar physics facility in the world. The telescope
is designed as a four-meter off-axis Gregorian, with a rotating Coude
laboratory designed to simultaneously house and support five first-light
imaging and spectropolarimetric instruments. At current design, the
facility and its instruments will generate data volumes of 5 PB,
produce 108 images, and 107-109
metadata elements annually. This data will not only forge new
understanding of solar phenomena at high resolution, but enhance
participation in solar physics and further grow a small but vibrant
international community.The DKIST Data Center is being designed to
store, curate, and process this flood of information, while augmenting
its value by providing association of science data and metadata to
its acquisition and processing provenance. In early Operations,
the Data Center will produce, by autonomous, semi-automatic, and
manual means, quality-controlled and -assured calibrated data sets,
closely linked to facility and instrument performance during the
Operations lifecycle. These data sets will be made available to the
community openly and freely, and software and algorithms made available
through community repositories like Github for further collaboration
and improvement.We discuss the current design and approach of the DKIST
Data Center, describing the development cycle, early technology analysis
and prototyping, and the roadmap ahead. In this budget-conscious era,
a key design criterion is elasticity, the ability of the built system
to adapt to changing work volumes, types, and the shifting scientific
landscape, without undue cost or operational impact. We discuss our
deep iterative development approach, the underappreciated challenges
of calibrating ground-based solar data, the crucial integration of the
Data Center within the larger Operations lifecycle, and how software and
hardware support, intelligently deployed, will enable high-caliber solar
physics research and community growth for the DKIST's 40-year lifespan.
Title: The Fast Filament Eruption Leading to the X-flare on 2014
March 29
Authors: Kleint, Lucia; Battaglia, Marina; Reardon, Kevin; Sainz Dalda,
Alberto; Young, Peter R.; Krucker, Säm
Bibcode: 2015ApJ...806....9K
Altcode: 2015arXiv150400515K
We investigate the sequence of events leading to the solar X1 flare
SOL2014-03-29T17:48. Because of the unprecedented joint observations of
an X-flare with the ground-based Dunn Solar Telescope and the spacecraft
IRIS, Hinode, RHESSI, STEREO, and the Solar Dynamics Observatory, we can
sample many solar layers from the photosphere to the corona. A filament
eruption was observed above a region of previous flux emergence, which
possibly led to a change in magnetic field configuration, causing
the X-flare. This was concluded from the timing and location of the
hard X-ray emission, which started to increase slightly less than a
minute after the filament accelerated. The filament showed Doppler
velocities of ∼2-5 km s-1 at chromospheric temperatures
for at least one hour before the flare occurred, mostly blueshifts,
but also redshifts near its footpoints. Fifteen minutes before the
flare, its chromospheric Doppler shifts increased to ∼6-10 km
s-1 and plasma heating could be observed before it lifted
off with at least 600 km s-1 as seen in IRIS data. Compared
to previous studies, this acceleration (∼3-5 km s-2) is
very fast, while the velocities are in the common range for coronal
mass ejections. An interesting feature was a low-lying twisted second
filament near the erupting filament, which did not seem to participate
in the eruption. After the flare ribbons started on each of the second
filament’s sides, it seems to have untangled and vanished during the
flare. These observations are some of the highest resolution data of
an X-class flare to date and reveal some small-scale features yet to
be explained.
Title: The DKIST Data Center: Challenges and Opportunities Ahead
Authors: Berukoff, Steven; Reardon, Kevin; Hays, Tony; Spiess, DJ
Bibcode: 2015TESS....140201B
Altcode:
The four-meter Daniel K. Inouye Solar Telescope is currently under
construction on Haleakalā, Hawai´i, with completion planned in
2019. When fully operational, DKIST will routinely generate 10-20
TB of data and 10^8 metadata elements per day. These data will be
transported to the DKIST Data Center at NSO headquarters in Boulder
for storage, processing, and distribution. The initial output from the
Data Center is expected to be high-quality calibrated data sets, with
corrections applied to the level achievable for each acquired dataset
(with variations due to seeing conditions and experiment design,
among others). The processed data, along with the software code and
full data description, will be made openly available to investigators
and interested users. A key aspect of the design of the DKIST Data
Center is its scalability, flexibility, and extensibility. Within
an overview of the status of the Data Center development and plans,
we will comment on lessons learned thus far in conceiving, designing,
and prototyping a petascale informatics facility dedicated to generating
high-quality calibrated data sets.
Title: Chromospheric Rapid Blueshifted Excursions Observed with IBIS
and their Association with Photospheric Magnetic Field Evolution
Authors: Deng, Na; Chen, Xin; Liu, Chang; Jing, Ju; Tritschler,
Alexandra; Reardon, Kevin P.; Lamb, Derek A.; Deforest, Craig E.;
Denker, Carsten; Wang, Shuo; Liu, Rui; Wang, Haimin
Bibcode: 2015ApJ...799..219D
Altcode: 2014arXiv1412.4038D
Chromospheric rapid blueshifted excursions (RBEs) are suggested to
be the disk counterparts of type II spicules at the limb and believed
to contribute to the coronal heating process. Previous identification
of RBEs was mainly based on feature detection using Dopplergrams. In
this paper, we study RBEs on 2011 October 21 in a very quiet region at
the disk center, which were observed with the high-cadence imaging
spectroscopy of the Ca II 8542 Å line from the Interferometric
Bidimensional Spectrometer (IBIS). By using an automatic spectral
analysis algorithm, a total of 98 RBEs are identified during an 11
minute period. Most of these RBEs have either a round or elongated
shape, with an average area of 1.2 arcsec2. The detailed
temporal evolution of spectra from IBIS makes possible a quantitative
determination of the velocity (~16 km s-1) and acceleration
(~400 m s-2) of Ca II 8542 RBEs, and reveals an additional
deceleration (~-160 m s-2) phase that usually follows the
initial acceleration. In addition, we also investigate the association
of RBEs with the concomitant photospheric magnetic field evolution,
using coordinated high-resolution and high-sensitivity magnetograms
made by Hinode. Clear examples are found where RBEs appear to be
associated with the preceding magnetic flux emergence and/or the
subsequent flux cancellation. However, further analysis with the aid
of the Southwest Automatic Magnetic Identification Suite does not
yield a significant statistical association between these RBEs and
magnetic field evolution. We discuss the implications of our results
in the context of understanding the driving mechanism of RBEs.
Title: DKIST: Observing the Sun at High Resolution
Authors: Tritschler, A.; Rimmele, T. R.; Berukoff, S.; Casini, R.;
Craig, S. C.; Elmore, D. F.; Hubbard, R. P.; Kuhn, J. R.; Lin, H.;
McMullin, J. P.; Reardon, K. P.; Schmidt, W.; Warner, M.; Woger, F.
Bibcode: 2015csss...18..933T
Altcode:
The 4-m aperture Daniel K. Inouye Solar Telescope (DKIST) formerly
known as the Advanced Technology Solar Telescope (ATST) and currently
under construction on Haleakalā (Maui, Hawai'i) will be the largest
solar ground-based telescope and leading resource for studying the
dynamic Sun and its phenomena at high spatial, spectral and temporal
resolution. Accurate and sensitive polarimetric observations at
high-spatial resolution throughout the solar atmosphere including the
corona is a high priority and a major science driver. As such the DKIST
will offer a combination of state-of-the-art instruments with imaging
and/or spectropolarimetric capabilities covering a broad wavelength
range. This first-light instrumentation suite will include: a Visible
Broadband Imager (VBI) for high-spatial and -temporal resolution
imaging of the solar atmosphere; a Visible Spectro-Polarimeter (ViSP)
for sensitive and accurate multi-line spectropolarimetry; a double
Fabry-Pérot based Visible Tunable Filter (VTF) for high-spatial
resolution spectropolarimetry; a fiber-fed 2D Diffraction-Limited Near
Infra-Red Spectro-Polarimeter (DL-NIRSP); and a Cryogenic Near Infra-Red
Spectro-Polarimeter (Cryo-NIRSP) for coronal magnetic field measurements
and on-disk observations of e.g. the CO lines at 4.7 microns. We
will provide a brief overview of the DKIST's unique capabilities to
perform spectroscopic and spectropolarimetric measurements of the solar
atmosphere using its first-light instrumentation suite, the status of
the construction project, and how facility and data access is provided
to the US and international community.
Title: The VAULT2.0 Observing Campaign: A Comprehensive Investigation
of the Chromosphere-Corona Interface at Sub-arcsecond scales
Authors: Vourlidas, A.; Korendyke, C.; Tun-Beltran, S. D.; Ugarte-Urra,
I.; Morrill, J. S.; Warren, H. P.; Young, P.; De Pontieu, B.; Gauzzi,
G.; Reardon, K.
Bibcode: 2014AGUFMSH41C4155V
Altcode:
We report the first results from an observing campaign in support of
the VAULT2.0 sounding rocket launch on September 30, 2014. VAULT2.0
is a Lya (1216Å) spectroheliograph capable of 0.3" (~250 km) spatial
resolution. The objective of the VAULT2.0 project is the study of
the chromosphere-corona interface. This interface has acquired renewed
emphasis over the last few years, thanks to high-resolution observations
from Hinode/SOT and EIS instruments and the Lya imaging from the two
VAULT flights. The observations have shown that the upper chromosphere
may play a more important role in heating the corona and in affecting
EUV observations that previously thought: (1) by supplying the mass
via Type-II spicules and, (2) by absorbing coronal emission. Many of
the required clues for further progress are located in sub-arcsecond
structures with temperatures between 10000 and 50000 K, a regime not
accessible by Hinode or SDO. Lyman-alpha observations are, therefore,
ideal, for filling in this gap. The observing campaign in support of
the VAULT2.0 is closely coordinated with the Hinode and IRIS missions
to study the mass/energy flow from the chromosphere to the corona with
joint observations of type-II spicules, and the magnetic connectivity
of coronal loops using the full imaging and spectral capabilities of
IRIS, Hinode and SDO. Several ground-based observatories also provide
important observations (IBIS, BBSO, SOLIS). The VAULT2.0 project is
funded by the NASA LCAS program.
Title: High-resolution Observations of the X-flare on 2014-03-29
Authors: Kleint, L.; Battaglia, M.; Krucker, S.; Reardon, K.; Sainz
Dalda, A.
Bibcode: 2014AGUFMSH31C..06K
Altcode:
We investigate the sequence of events leading to the X1 flare
SOL2014-03-29T17:48. Because of the unprecedented joint observations of
an X-flare with the ground-based Dunn Solar Telescope and the spacecraft
IRIS, Hinode, RHESSI, STEREO, and SDO, we can sample many solar layers
from the photosphere to the corona. We find that a filament eruption,
which was possibly caused by a thermal instability, was the cause of
this X-flare. The filament was rising in the chromosphere for at least
one hour before the flare occurred with a velocity of ∼2--5 km/s. 15
minutes before the flare, its chromospheric rise velocity increased to
∼6--10 km/s, before it lifted off with at least 600 km/s, as seen by
IRIS in the transition region. Doppler velocities from H-alpha images
reveal intriguing small scale flows along the filament and enable us to
derive its probable shape. An unusual feature was a low-lying twisted
flux rope near the filament, which did not participate in the filament
eruption. After the flare ribbons started on each of its sides, the
flux rope seems to have untangled and vanished during the flare. We
present a comprehensive overview of the flare, including polarimetric
and spectroscopic data at subarcsecond resolution.
Title: Next-generation Solar Data and Data Services from the Daniel
K. Inouye Solar Telescope
Authors: Berukoff, S. J.; Reardon, K.; Rimmele, T.
Bibcode: 2014AGUFMSH41C4162B
Altcode:
The Daniel K. Inouye Solar Telescope (DKIST), when completed in
2019, will be the largest, most capable, solar telescope in the
world. Currently under construction on the summit of Haleakalā on Maui,
the DKIST will enable foundational insights into the physics of the
Sun's photosphere, chromosphere, and corona. Its suite of first-light
instruments will produce approximately 25 TB of raw data per day,
with occasional bursts of 50TB per day. These high data rates will
require a scalable, flexible data and computing architecture that
enables and promotes scientific inquiry and discovery. We briefly
describe the DKIST data stream and then provide an overview of the
proposed data-center architecture and resources that will allow users
to fully exploit this world-class facility.
Title: Venus' thermospheric temperature field using a refraction
model at terminator : comparison with 2012 transit observations
using SDO/HMI, VEx/SPICAV/SOIR and NSO/DST/FIRS
Authors: Widemann, Thomas; Jaeggli, Sarah; Reardon, Kevin; Tanga,
Paolo; Père, Christophe; Pasachoff, Jay M.; Vandaele, Ann Carine;
Wilquet, Valerie; Mahieux, Arnaud; Wilson, Colin
Bibcode: 2014DPS....4630206W
Altcode:
The transit of Venus in June 2012 provided a unique case study of the
Venus' atmosphere transiting in front of the Sun, while at the same time
ESA's Venus Express orbiter observed the evening terminator at solar
ingress and solar egress.We report on mesospheric temperature at Venus'
morning terminator using SDO/HMI aureole photometry and comparison with
Venus Express. Close to ingress and egress phases, we have shown that
the aureole photometry reflects the local density scale height and the
altitude of the refracting layer (Tanga et al. 2012). The lightcurve of
each spatially resolved aureole element is fit to a two-parameter model
to constrain the meridional temperature gradient at terminator. Our
measurements are in agreement with the VEx/SOIR temperatures obtained
during orbit 2238 at evening terminator during solar ingress (46.75N -
LST = 6.075PM) and solar egress (31.30N - LST = 6.047PM) captured from
the Venus Express orbiter at the time Venus transited the Sun.We also
performed spectroscopy and polarimetry during the transit of Venus
focusing on extracting signatures of CO2 absorption. Observations were
taken during the first half of the transit using the Facility InfraRed
Spectropolarimeter (FIRS) on the Dunn Solar Telescope (DST). Although
the predicted CO2 transmission spectrum of Venus was not particularly
strong at 1565 nm, this region of the H-band often used in magnetic
field studies of the Sun's photosphere provides a particularly flat
solar continuum with few atmospheric lines. Sun-subtracted Venus limb
observations show intensity distribution of vibrational CO2 bands 221
2v+2v2+v3 at 1.571μm and 141 v1+4v2+v3 at 1.606μm.
Title: The Daniel K. Inouye Solar Telescope first light instruments
and critical science plan
Authors: Elmore, David F.; Rimmele, Thomas; Casini, Roberto; Hegwer,
Steve; Kuhn, Jeff; Lin, Haosheng; McMullin, Joseph P.; Reardon, Kevin;
Schmidt, Wolfgang; Tritschler, Alexandra; Wöger, Friedrich
Bibcode: 2014SPIE.9147E..07E
Altcode:
The Daniel K. Inouye Solar Telescope is a 4-meter-class all-reflecting
telescope under construction on Haleakalā mountain on the island of
Maui, Hawai'i. When fully operational in 2019 it will be the world's
largest solar telescope with wavelength coverage of 380 nm to 28 microns
and advanced Adaptive Optics enabling the highest spatial resolution
measurements of the solar atmosphere yet achieved. We review the
first-generation DKIST instrument designs, select critical science
program topics, and the operations and data handling and processing
strategies to accomplish them.
Title: Hα spectroscopy and multiwavelength imaging of a solar flare
caused by filament eruption
Authors: Huang, Z.; Madjarska, M. S.; Koleva, K.; Doyle, J. G.;
Duchlev, P.; Dechev, M.; Reardon, K.
Bibcode: 2014A&A...566A.148H
Altcode: 2014arXiv1405.2194H
Context. We study a sequence of eruptive events including filament
eruption, a GOES C4.3 flare, and a coronal mass ejection.
Aims:
We aim to identify the possible trigger(s) and precursor(s) of the
filament destabilisation, investigate flare kernel characteristics,
flare ribbons/kernels formation and evolution, study the interrelation
of the filament-eruption/flare/coronal-mass-ejection phenomena as
part of the integral active-region magnetic field configuration, and
determine Hα line profile evolution during the eruptive phenomena.
Methods: Multi-instrument observations are analysed including Hα
line profiles, speckle images at Hα - 0.8 Å and Hα + 0.8 Å from
IBIS at DST/NSO, EUV images and magnetograms from the SDO, coronagraph
images from STEREO, and the X-ray flux observations from Fermi and
GOES.
Results: We establish that the filament destabilisation
and eruption are the main triggers for the flaring activity. A
surge-like event with a circular ribbon in one of the filament
footpoints is determined as the possible trigger of the filament
destabilisation. Plasma draining in this footpoint is identified as
the precursor for the filament eruption. A magnetic flux emergence
prior to the filament destabilisation followed by a high rate of flux
cancellation of 1.34 × 1016 Mx s-1 is found
during the flare activity. The flare X-ray lightcurves reveal three
phases that are found to be associated with three different ribbons
occurring consecutively. A kernel from each ribbon is selected and
analysed. The kernel lightcurves and Hα line profiles reveal that the
emission increase in the line centre is stronger than that in the line
wings. A delay of around 5-6 min is found between the increase in the
line centre and the occurrence of red asymmetry. Only red asymmetry is
observed in the ribbons during the impulsive phases. Blue asymmetry
is only associated with the dynamic filament. Appendix A and
movie associated to Fig. A.4 are available in electronic form at http://www.aanda.org
Title: Chromospheric umbral dynamics
Authors: Reardon, Kevin P.; Vecchio, Antonio; Cauzzi, Gianna;
Tritschler, Alexandra
Bibcode: 2014AAS...22432304R
Altcode:
The chromosphere above sunspots is seen to undergo dynamical driving
from perturbations from lower layers of the atmosphere. Umbral
flashes have long been understood to be the result of acoustic shocks
due to the drop in density in the sunspot chromosphere. Detailed
observations of the umbral waves and flashes may help reveal the
nature of the sunspot structure in the upper atmosphere. We report
on high-resolution observations of umbral dynamics observed in the Ca
II 8542 line by IBIS at the Dunn Solar Telescope. We use a principal
component decomposition technique (POD) to isolate different components
of the observed oscillations. We are able to explore temporal and
spatial evolution of the umbral flashes. We find significant variation
in the nature of the flashes over the sunspot, indicating that the
chromospheric magnetic topology can strongly modify the nature of the
umbral intensity and velocity oscillations.
Title: Chromospheric Diagnostics from IRIS and DST
Authors: Cauzzi, Gianna; Reardon, Kevin P.; Jaeggli, Sarah A.;
Reid, Aaron
Bibcode: 2014AAS...22430201C
Altcode:
Using data obtained during a coordinated observing campaign in
September 2013, we compare the spectral and imaging diagnostics from
IRIS and the instruments at the Dunn Solar Telescope (DST). We focus
on a small active region observed for approximately one hour with IRIS
(NUV, FUV, and SJI) in conjunction with IBIS, FIRS, and ROSA from the
DST.In particular, we examine the line widths and intensities in the
different chromospheric lines (H-alpha, Ca II 8542, Mg II) and the
temporal evolution of these different diagnostics. This allows us to
better relate the views from new window provided by IRIS to previous
studies of the chromosphere.
Title: On the Naming and Dscovery of the Solar Chromosphere
Authors: Reardon, Kevin P.
Bibcode: 2014AAS...22420304R
Altcode:
The chromosphere was discovered by Lockyer and Janssen in 1868,
and named by Lockyer. It is often stated that his motivation
for associating this region of the solar atmosphere with "color"
was because of its bright red appearance at eclipses due to the
predominance of H-alpha. However, Lockyer had never seen a total
solar eclipse at the time he gave the name and does not appear to
have provided this justification himself. It is more likely that the
"color" refers to the plethora of different colored emission lines
he saw and identified with his spectrograph.I also discuss the Padre
Angelo Secchi's observation of the 1860 eclipse in Spain, His accurate
description of the chromosphere as a complete, theretofore unseen
layer enveloping the Sun predates Lockyer and Janssen by eight years.
Title: Challenges for the DKIST Data Center
Authors: Reardon, Kevin P.; Rimmele, Thomas R.
Bibcode: 2014AAS...22421843R
Altcode:
Processing the large volumes of complex, multi-instrument, ground-based
data generated at the DKIST will require implementation of algorithms
and tools at a level not previously achieved for high-resolution,
ground-based solar telescopes. We discuss some the goals of the
data reduction pipelines for DKIST, including the different types
of calibrations that would (optimally) be applied to the acquired
data. We highlight some of the particular challenges for ground-based
data, including seeing effects, atmospheric dispersion, and rapid
changes in instrumental calibrations. We will describe a possible
software framework for the implementation of the pipelines, as well
as point out some areas for community input or VSO integration in the
development process.
Title: Venus' thermospheric temperature field using a refraction
model at terminator : comparison with 2012 transit observations
using SDO/HMI and NSO/DST/FIRS
Authors: Widemann, Thomas; Tanga, Paolo; Père, Christophe; Jaeggli,
Sarah; Reardon, Kevin; Pasachoff, Jay M.
Bibcode: 2014EGUGA..1612916W
Altcode:
The transit of Venus in June 2012 provided a unique case study of an
Earth-size planet's atmosphere transiting in front of its parent star
at 0.7AU, while at the same time ESA's Venus Express orbiter observed
the evening terminator at solar ingress and solar egress. We report
on mesospheric temperature at Venus' morning terminator using SDO/HMI
aureole photometry and comparison with Venus Express. Close to ingress
and egress phases, we have shown that the aureole photometry reflects
the local density scale height and the altitude of the refracting layer
(Tanga et al. 2012). The lightcurve of each spatial resolution element
of the aureole is compared to a two-parameter model to constrain the
meridional temperature gradient along the terminator. Our measurements
are in agreement with the VEx/SOIR temperatures obtained during
orbit 2238 at evening terminator during solar ingress (46.75N - LST
= 6.075PM) and solar egress (31.30N - LST = 6.047PM) captured from
the Venus Express orbiter at the time Venus transited the Sun for
Earth-based observers. We also performed spectroscopy and polarimetry
during the transit of Venus focusing on extracting signatures of
CO2 absorption. Observations were taken during the first half of the
transit using the Facility InfraRed Spectropolarimeter on the Dunn
Solar Telescope. Although the predicted CO2 transmission spectrum
of Venus was not particularly strong at 1565 nm, this region of the
H-band often used in magnetic field studies of the Sun's photosphere
provides a particularly flat solar continuum with few atmospheric and
molecular lines. Sun-subtracted Venus limb observations show intensity
distribution of vibrational CO2 bands 221 2v + 2ν2 + ν3 at 1.571um and
141 ν1 + 4ν2 + ν3 at 1.606um. Data independently allow to constrain
temperature as well as cross-terminator thermospheric winds.
Title: The Solar Chromosphere Observed at 1 Hz and 0.''2 Resolution
Authors: Lipartito, Isabel; Judge, Philip G.; Reardon, Kevin; Cauzzi,
Gianna
Bibcode: 2014ApJ...785..109L
Altcode: 2014arXiv1401.4474L
We recently reported extremely rapid changes in chromospheric fine
structure observed using the IBIS instrument in the red wing of
Hα. Here, we examine data obtained during the same observing run
(2010 August 7), of a mature active region NOAA 11094. We analyze
more IBIS data including wavelength scans and data from the Solar
Dynamics Observatory, all from within a 30 minute interval. Using a
slab radiative transfer model, we investigate the physical nature of
fibrils in terms of tube-like versus sheet-like structures. Principal
Component Analysis shows that the very rapid Hα variations in the
line wings depend mostly on changes of line width and line shift,
but for Ca II 854.2 the variations are dominated by changes in column
densities. The tube model must be rejected for a small but significant
class of fibrils undergoing very rapid changes. If our wing data arise
from the same structures leading to "type II spicules," our analysis
calls into question much recent work. Instead, the data do not reject
the hypothesis that some fibrils are optical superpositions of plasma
collected into sheets. We review how Parker's theory of tangential
discontinuities naturally leads to plasma collecting into sheets,
and show that the sheet picture is falsifiable. Chromospheric fine
structures seem to be populated by both tubes and sheets. We assess the
merits of spectral imaging versus slit spectroscopy for future studies.
Title: Observations of the Black-Drop Effect at the 2012 Transit
of Venus
Authors: Rogoszinski, Zeeve; Pasachoff, J. M.; Babcock, B. A.;
Schneider, G.; Reardon, K. P.
Bibcode: 2014AAS...22324716R
Altcode:
We observed the 2012 transit of Venus from several locations,
including the Mees Solar Observatory of the University of Hawaii on
Maui; the Dunn Solar Telescope at the Sacramento Peak Observatory of
the National Solar Observatory in Sunspot, NM; and the Big Bear Solar
Observatory of the New Jersey Institute of Technology in California. Our
observations, mainly directed at the study of Venus's atmosphere, also
included high-resolution views of the black-drop effect. Historically,
the black-drop effect proved to be a daunting anomaly for measuring
the path length of Venus across the Sun’s surface with sufficient
time accuracy to allow satisfactory measurement of the astronomical
unit. Therefore, this phenomenon set back the accurate calculations
for centuries of the size and scale of the solar system. In this
paper, we discuss data taken with the New Solar Telescope at the Big
Bear Observatory and with the IBIS on the Dunn Solar Telescope. We
show the evolution of isophotes as a function of time to demonstrate
various limb effects during second and third contacts. Schneider,
Pasachoff, and Golub (Icarus 168. 249-256, 2004) have shown that the
black-drop effect as seen in a transit of Mercury resulted from both the
point-spread function of the telescope and the extreme limb-darkening
effect at the region of the solar limb where the black-drop effect is
demonstrated, and the current paper extends the analysis to the recent
transit of Venus. As they showed, and as is verified here, Venus's
atmosphere plays no role in the black-drop effect. ZR (Vassar '14)
was a Keck Northeast Astronomy Consortium Summer Fellow at Williams
College, supported by an NSF/REU grant to the Keck Northeast Astronomy
Consortium. This research used the following tools: IDL/IDP3, ImageJ,
and DS9. For obtaining the data at the Big Bear Solar Observatory,
we thank Vasyl Yurchyshyn. Special thanks goes to Dr. Steven Souza
for his support. The 2012 observations were obtained with a grant from
the Committee for Research and Exploration of the National Geographic
Society.
Title: Future Diagnostic Capabilities: The 4-meter Daniel K. Inouye
Solar Telescope
Authors: Berger, Thomas; Reardon, Kevin; Elmore, David; Woeger,
Friedrich; Tritschler, Alexandra; Rimmele, Thomas
Bibcode: 2014cosp...40E.294B
Altcode:
We discuss the observational capabilities of the Daniel K. Inouye
Solar Telescope (DKSIT), formerly known as the Advanced Technology
Solar Telescope (ATST), currently under construction on Haleakala
Mountain on the island of Maui, Hawaii, with first light anticipated
in mid-2019. The DKIST will be a 4-meter aperture Gregorian telescope
with advanced environmental control and adaptive optics capable of
producing diffraction-limited resolution in visible light of 0.03"
or about 20 km in the solar photosphere. The first light instrument
suite will include the Visible Broadband Imager (VBI), an interference
filter-based instrument capable of 30 Hz imaging of photospheric and
chromospheric magnetic structures in the 380 to 800 nm wavelength
range. All VBI images will be reconstructed in near-real-time using
the KISIP speckle reconstruction algorithm adapted to the DKIST
optical and AO configuration. The Visible Spectropolarimeter (ViSP)
instrument being fabricated by the High Altitude Observatory (HAO) will
enable high-precision slit-spectropolarimetery in any three spectral
regions from 380 to 900 nm. The ViSP instrument will be the highest
precision spectropolarimeter ever produced with a spatial resolution
of approximately 40 km at 600 nm and temporal resolution of 10s to
achieve 1e-03 polarimetric precision. The Visible Tunable Filter (VTF)
instrument under fabrication at the Kiepenheuer Institute for Solar
Physics (KIS) is a triple-etalon Fabry-Perot imaging spectropolarimeter
instrument capable of diffraction limited measurements of the Fe I
630.2 nm and Ca II 854.2 nm spectral lines for Doppler and magnetic
measurements in the photosphere and chromosphere, respectively. The
VTF will also enable the highest spatial and temporal resolution
observations yet achieved in the H-alpha line for detailed studies of
chromospheric dynamics in response to photospheric magnetic drivers. The
Diffraction-Limited Near-IR Spectropolarimeter (DL-NiRSP) and the
Cryogenic Near-IR Spectropolarimeter (Cryo-NiRSP) instruments, both
under fabrication at the University of Hawaii, will enable polarimetric
and spectroscopic investigations in the largely unexplored infra-red
spectral region. The DL-NiRSP will span 900 nm to 2.5 microns in
wavelength and include a novel fiber-optic "Integral Field Unit"
(IFU) for true imaging spectropolarimetry in three simultaneous
spectral regions over a variable field of view. This instrument
will enable revolutionary measurements of prominence magnetic fields
and will also, in the wider field mode, enable coronal polarimetric
studies. The Cryo-NiRSP instrument spans the 1--5 micron wavelength
range and will make near-diffraction limited 0.3" resolution slit-scan
measurements of the coronal magnetic field out to 1.3 solar radii
with temporal resolution measured in minutes. The DKIST facility
will undergo extensive polarimetric calibration to ensure that the
ultimate goal of 5e-04 polarimetic precision is obtainable under the
best conditions. All of the data from the DKIST will be transmitted
to the central DKIST data center in Boulder, Colorado where automated
reduction and calibration pipelines will rapidly provide the community
with calibrated data products for use in science investigations. The
DKIST will also be operated in a "Service Mode" access model in which
investigators will not be required to travel to the telescope to
accomplish their science observations.
Title: Data integration and analysis using the Heliophysics Event
Knowledgebase
Authors: Hurlburt, Neal; Reardon, Kevin
Bibcode: 2014cosp...40E1250H
Altcode:
The Heliophysics Event Knowledgebase (HEK) system provides an integrated
framework for automated data mining using a variety of feature-detection
methods; high-performance data systems to cope with over 1TB/day of
multi-mission data; and web services and clients for searching the
resulting metadata, reviewing results, and efficiently accessing the
data products. We have recently enhanced the capabilities of the HEK
to support the complex datasets being produced by the Interface Region
Imaging Spectrograph (IRIS). We are also developing the mechanisms to
incorporate descriptions of coordinated observations from ground-based
facilities, including the NSO's Dunn Solar Telescope (DST). We will
discuss the system and its recent evolution and demonstrate its ability
to support coordinated science investigations.
Title: Comet C/2012 S1 (ISON): Observations of the Dust Grains from
SOFIA and of the Atomic Gas from NSO Dunn and McMath-Pierce Solar
Telescopes (Invited)
Authors: Wooden, D. H.; Woodward, C. E.; Harker, D. E.; Kelley, M. S.;
Sitko, M.; Reach, W. T.; De Pater, I.; Gehrz, R. D.; Kolokolova,
L.; Cochran, A. L.; McKay, A. J.; Reardon, K.; Cauzzi, G.; Tozzi,
G.; Christian, D. J.; Jess, D. B.; Mathioudakis, M.; Lisse, C. M.;
Morgenthaler, J. P.; Knight, M. M.
Bibcode: 2013AGUFM.P24A..07W
Altcode:
Comet C/2012 S1 (ISON) is unique in that it is a dynamically new comet
derived from the Oort cloud reservoir of comets with a sun-grazing
orbit. Infrared (IR) and visible wavelength observing campaigns were
planned on NASA's Stratospheric Observatory For Infrared Astronomy
(SOFIA) and on National Solar Observatory Dunn (DST) and McMath-Pierce
Solar Telescopes, respectively. We highlight our early results. SOFIA
(+FORCAST [1]) mid- to far-IR images and spectroscopy (~5-35 μm)
of the dust in the coma of ISON are to be obtained by the ISON-SOFIA
Team during a flight window 2013 Oct 21-23 UT (r_h≈1.18 AU). Dust
characteristics, identified through the 10 μm silicate emission
feature and its strength [2], as well as spectral features from
cometary crystalline silicates (Forsterite) at 11.05-11.2 μm, and
near 16, 19, 23.5, 27.5, and 33 μm are compared with other Oort cloud
comets that span the range of small and/or highly porous grains (e.g.,
C/1995 O1 (Hale-Bopp) [3,4,5] and C/2001 Q4 (NEAT) [6]) to large and/or
compact grains (e.g., C/2007 N4 (Lulin) [7] and C/2006 P1 (McNaught)
[8]). Measurement of the crystalline peaks in contrast to the broad
10 and 20 μm amorphous silicate features yields the cometary silicate
crystalline mass fraction [9], which is a benchmark for radial transport
in our protoplanetary disk [10]. The central wavelength positions,
relative intensities, and feature asymmetries for the crystalline
peaks may constrain the shapes of the crystals [11]. Only SOFIA can
look for cometary organics in the 5-8 μm region. Spatially resolved
measurements of atoms and simple molecules from when comet ISON is
near the Sun (r_h< 0.4 AU, near Nov-20--Dec-03 UT) were proposed
for by the ISON-DST Team. Comet ISON is the first comet since comet
Ikeya-Seki (1965f) [12,13] suitable for studying the alkalai metals Na
and K and the atoms specifically attributed to dust grains including
Mg, Si, Fe, as well as Ca. DST's Horizontal Grating Spectrometer
(HGS) measures 4 settings: Na I, K, C2 to sample cometary organics
(along with Mg I), and [O I] as a proxy for activity from water [14]
(along with Si I and Fe I). State-of-the-art instruments that will also
be employed include IBIS [15], which is a Fabry-Perot spectral imaging
system that concurrently measures lines of Na, K, Ca II, or Fe, and ROSA
(CSUN/QUB) [16], which is a rapid imager that simultaneously monitors Ca
II or CN. From McMath-Pierce, the Solar-Stellar Spectrograph also will
target ISON (320-900 nm, R~21,000, r_h<0.3 AU). Assuming survival,
the intent is to target ISON over r_h<0.4 AU, characteristic of
prior Na detections [12,13,17,18,19]. References: [1] Adams, J.D., et
al. 2012, SPIE, 8446, 16; [2] Kelley, M.S., Wooden, D.H. 2009, PSS, 57,
1133; [3] Harker et al. 2002, ApJ, 580, 579; [4] Hayward et al. 2000,
ApJ, 538, 428; [5] Hadamcik, E., Levasseur-Regourd, A.C. 2003, JQSRT,
79-80, 661; [6] Wooden, D.H. 2004, ApJL, 612, L77; [7] Woodward et
al. 2011, AJ, 141, 181; [8] Kelley et al. 2010, LPSC, 41, #2375;
[9] Kelley, M.S. et al. 2011, AAS, 211, 560; [10] Wooden, D.H. 2008,
SSRv, 138, 75; [11] Lindsay et al. 2013, ApJ, 766, 54; [12] Preston,
G. W. 1967, ApJ, 147, 718; [13] Slaughter, C.D. 1969, AJ, 74, 929;
[14] McKay et al. 2012, Icarus, 222, 684; [15] Cavallini, F., 2006,
Solar Phys., 236, 415; [16] Jess et al., 2010, Solar Phys, 261, 363;
[17] Watanabe, J-I. et al. 2003, ApJ, 585, L159; [18] Leblanc, F. et
al. 2008, A&A, 482, 293; [19] Fulle, M. et al. 2013, ApJL, 771, L21
Title: Spectral Signatures of Penumbral Transients
Authors: Reardon, K.; Tritschler, A.; Katsukawa, Y.
Bibcode: 2013ApJ...779..143R
Altcode:
In this work we investigate the properties of penumbral transients
observed in the upper photospheric and chromospheric region above a
sunspot penumbra using two-dimensional spectroscopic observations
of the Ca II 854.21 nm line with a 5 s cadence. In our 30 minutes
of observations, we identify several penumbral-micro jets (PMJs)
with cotemporal observations from Dunn Solar Telescope/IBIS and
Hinode/SOT. We find that the line profiles of these PMJ events
show emission in the two wings of the line (±0.05 nm), but
little modification of the line core. These are reminiscent of
the line profiles of Ellerman bombs observed in plage and network
regions. Furthermore, we find evidence that some PMJ events have a
precursor phase starting 1 minute prior to the main brightening that
might indicate initial heating of the plasma prior to an acoustic or
bow shock event. With the IBIS data, we also find several other types
of transient brightenings with timescales of less than 1 minute that
are not clearly seen in the Hinode/SOT data. The spectral profiles and
other characteristics of these events are significantly different from
those of PMJs. The different appearances of all these transients are
an indicator of the general complexity of the chromospheric magnetic
field and underscore the highly dynamic behavior above sunspots. It
also highlights the care that is needed in interpreting broadband
filter images of chromospheric lines, which may conceal very different
spectral profiles, and the underlying physical mechanisms at work.
Title: Spatially Resolved Spectroscopic Observations of Na and K in
the Tail of Comet C/2011 L4 (PanSTARRS)
Authors: Cochran, Anita L.; Wooden, D. H.; McKay, A. J.; Cauzzi, G.;
Reardon, K.; Tozzi, G.
Bibcode: 2013DPS....4550205C
Altcode:
We used the Dunn Solar Telescope (DST) of The National Solar Observatory
to obtain spectroscopic observations of comet C/2011 L4 (PanSTARRS) on
13 and 14 March 2013. The DST has the advantage for comet observations
that one can observe the comet when it is close to the Sun. At the
time of our observations, comet PanSTARRS was at 0.31 and 0.32 AU
heliocentric distance. We used the Horizontal Spectrograph to observe
five different spectral regions of the coma. The resolving power was
50,000 - 60,000. The slit was 0.3 arcsec wide and 171 arcsec long. At
the comet's geocentric distance, the slit covered 1.43e5 km. The
comet was approximately centered on the slit. We observed strong
emissions from sodium (D1@589.592nm and D2@588.995nm) and potassium
(D1@770.108nm and D2@671.701nm), along with a weak continuum. Lithium
was not detected. The sodium was visible on the optocenter and the
tailward side of the comet and extended to the edge of the slit (i.e. at
least 70,000km tailward). It shifted redward at larger cometocentric
distances, attributable to the acceleration of sodium by solar radiation
pressure. The potassium was much weaker than the sodium and does not
appear to extend as far from the optocenter. In this paper, we will show
the distribution of these gases and compare their relative strengths. We
will discuss the effects of the different photodissociative lifetimes
of sodium and potassium and how they dictate what we observed.
Title: Characterization of a transiting exo-Venus : lessons from
the 2012 Transit
Authors: Widemann, Thomas; Jaeggli, S. A.; Reardon, K. P.; Tanga,
P.; Pasachoff, J. M.; Schneider, G.
Bibcode: 2013DPS....4511811W
Altcode:
The transit of Venus in June 2012 provided a unique chance to
view a well studied planetary atmosphere as we might see that of a
transiting exoplanet, through scattered and refracted illumination
of its parent star. We report on mesospheric temperature at Venus'
morning terminator using SDO/HMI aureole photometry and comparison with
Venus Express. Close to ingress and egress phases, we have shown that
the aureole photometry reflects the local density scale height and the
altitude of the refracting layer (Tanga et al. 2012). The lightcurve
of each spatial resolution element of the aureole is compared to a
two-parameter model to constrain the meridional temperature gradient
along the terminator. Our measurements are in agreement with the
VEx/SOIR temperatures obtained during orbit 2238 at evening terminator
during solar ingress (46.75N - LST = 6.075PM) and solar egress (31.30N -
LST = 6.047PM) as seen from the orbiter. Imaging data using IBIS/ROSA on
the Dunn Solar Telescope in the G-band (430 nm) are also presented. We
also performed spectroscopy and polarimetry during the transit of Venus
focusing on extracting signatures of CO2 absorption. Observations were
taken during the first half of the transit using the Facility InfraRed
Spectropolarimeter on the Dunn Solar Telescope. Although the predicted
CO2 transmission spectrum of Venus was not particularly strong at 1565
nm, this region of the H-band often used in magnetic field studies of
the Sun's photosphere provides a particularly flat solar continuum
with few atmospheric and molecular lines. Sun-subtracted Venus limb
observations show intensity distribution of vibro-rotational CO2 band
221 2ν + 2ν2 + ν3 at 1.571μm allowing for an additional constraint
on Venus' thermospheric temperature.
Title: Observation of neutral sodium above Mercury during the transit
of November 8, 2006
Authors: Potter, A. E.; Killen, R. M.; Reardon, Kevin P.; Bida, T. A.
Bibcode: 2013Icar..226..172P
Altcode:
We mapped the absorption of sunlight by sodium vapor in the exosphere
of Mercury during the transit of Mercury on November 8, 2006, using
the IBIS Interferometric BIdimensional Spectrometer at the Dunn Solar
Telescope operated by the National Solar Observatory at Sunspot, New
Mexico. The measurements were reduced to line-of-sight equivalent
widths for absorption at the sodium D2 line around the
shadow of Mercury. The sodium absorption fell off exponentially with
altitude up to about 600 km. However there were regions around north
and south polar-regions where relatively uniform sodium absorptions
extended above 1000 km. We corrected the 0-600 km altitude profiles
for seeing blur using the measured point spread function. Analysis of
the corrected altitude distributions yielded surface densities, zenith
column densities, temperatures and scale heights for sodium all around
the planet. Sodium absorption on the dawn side equatorial terminator was
less than on the dusk side, different from previous observations of the
relative absorption levels. We also determined Earthward velocities
for sodium atoms, and line widths for the absorptions. Earthward
velocities resulting from radiation pressure on sodium averaged 0.8
km/s, smaller than a prediction of 1.5 km/s. Most line widths were
in the range of 20 mA after correction for instrumental broadening,
corresponding to temperatures in the range of 1000 K.
Title: Statistical study of magnetic cancellations and on-disk
type-II spicules
Authors: Chen, Xin; Deng, N.; Lamb, D.; Jing, J.; Tritschler, A.;
Reardon, K. P.; Wang, H.
Bibcode: 2013SPD....44...04C
Altcode:
We present a study using coordinated observations of the Interferometric
BIdimensional Spectrometer (IBIS) at the Dunn Solar Telescope and
Hinode / Solar Optical Telescope of a quiet sun (QS) region near
disk center. Our goal is to analyze the relationship between the
cancellation of opposite magnetic polarities in the photosphere and
"Rapid Blueshifted Excursions" (RBEs) by comparing quasi-simultaneous
magnetograms and chromospheric Hα line profiles. On the one hand,
the RBEs are considered the on-disk counterpart of the type-II
spicules observed at the limb that are most likely caused by
magnetic reconnection on small scales. On the other hand, the
magnetic cancellation is a signature after small-scale reconnection
in the QS. We developed an automatic tracking algorithm for detecting
magnetic cancellation events in the photosphere, based on the existing
SWAMIS code which is good at tracking magnetic flux emergence. Our
code can find characteristics of each cancellation event and the
detected cancellation sites appear to outline the supergranular
network. Furthermore, another automatic tracking code for RBEs has been
developed for the spectroscopic observations obtained with IBIS. We
are able to show a statistical distribution of the properties of RBEs,
such as lifetime, shape, and line-of-sight velocity. Finally, using the
spatial and temporal tracking of both magnetic cancellation events and
RBEs, we find that there is no simple one-to-one correspondence. The
majority of RBEs are related to magnetic cancellation events, however
a subset of them are not.
Title: Enabling Science with the ATST Data Stream
Authors: Reardon, Kevin P.
Bibcode: 2013SPD....4440003R
Altcode:
The ATST will generate a large volume of data simultaneously
from multiple instruments. These data will have value both to the
investigators who design specific observational programs, and as
an archival dataset. The challenges in processing ground-based,
high-resolution observations are many, and the need to produce
robust processing pipelines for heterogeneous datasets compound the
difficulties. I will discuss some approaches for efficiently managing
these data and generating useful data products. I will also describe
opportunities for the community to contribute to the planning and
preparations for the ATST data stream.
Title: Velocity and Magnetic Field Distribution in a Forming Penumbra
Authors: Romano, P.; Frasca, D.; Guglielmino, S. L.; Ermolli, I.;
Tritschler, A.; Reardon, K. P.; Zuccarello, F.
Bibcode: 2013ApJ...771L...3R
Altcode:
We present results from the analysis of high-resolution
spectropolarimetric and spectroscopic observations of the solar
photosphere and chromosphere, obtained shortly before the formation of a
penumbra in one of the leading polarity sunspots of NOAA active region
11490. The observations were performed at the Dunn Solar Telescope of
the National Solar Observatory on 2012 May 28, using the Interferometric
Bidimensional Spectrometer. The data set is comprised of a 1 hr time
sequence of measurements in the Fe I 617.3 nm and Fe I 630.25 nm lines
(full Stokes polarimetry) and in the Ca II 854.2 nm line (Stokes I
only). We perform an inversion of the Fe I 630.25 nm Stokes profiles to
derive magnetic field parameters and the line-of-sight (LOS) velocity
at the photospheric level. We characterize chromospheric LOS velocities
by the Doppler shift of the centroid of the Ca II 854.2 nm line. We
find that, before the formation of the penumbra, an annular zone of
3''-5'' width is visible around the sunspot. In the photosphere, we
find that this zone is characterized by an uncombed structure of the
magnetic field although no visible penumbra has formed yet. We also
find that the chromospheric LOS velocity field shows several elongated
structures characterized by downflow and upflow motions in the inner
and outer parts of the annular zone, respectively.
Title: High-Cadence and High-Resolution Halpha Imaging Spectroscopy
of a Circular Flare's Remote Ribbon with IBIS
Authors: Deng, Na; Tritschler, A.; Jing, J.; Chen, X.; Liu, C.;
Reardon, K. P.; Denker, C.; Xu, Y.; Wang, H.
Bibcode: 2013SPD....4440404D
Altcode:
We present an unprecedented high-resolution halpha imaging
spectroscopic observation of a C4.1 flare taken with IBIS on 2011
October 22. The flare consists of a main circular ribbon that occurred
in a parasitic magnetic configuration and a remote ribbon that was
observed by the IBIS. Such a circular-ribbon flare with a remote
brightening is predicted in 3D fan-spine reconnection but so far has
been rarely reported. During the flare impulsive phase, we define
"core" and "halo" structures in the observed ribbon. Examining the
halpha emission spectra averaged in the flare core and halo areas,
we find that only those from the flare cores show typical nonthermal
electron beam heating characteristics. These characteristics include:
broad and centrally reversed emission spectra, excess emission in
the red wing with regard to the blue wing (i.e., red asymmetry),
and redshifted bisectors of the emission spectra. We also observe
rather quick timescales for the heating (30 s) and cooling (14--33
s) in the flare core locations. Therefore, we suggest that the flare
cores revealed by IBIS track the sites of electron beam precipitation
with exceptional spatial and temporal resolution. The flare cores
show two-stage motion (a parallel motion along the ribbon followed
by an expansion motion perpendicular to the ribbon) during the two
impulsive phases of the flare. Some cores jump quickly (30 km/s)
between discrete magnetic elements implying reconnection involving
different flux tubes. We observe a very high temporal correlation
(>0.9) between the integrated halpha and HXR emission during the
flare impulsive phase. A short time delay (4.6 s) is also found in the
halpha emission spikes relative to HXR bursts. The ionization timescale
of the cool chromosphere and the extra time taken for the electrons
to travel to the remote ribbon site may contribute to this delay.
Title: 1565 nm Observations of the transit of Venus, Proxy for a
Transiting Exoplanet
Authors: Jaeggli, Sarah A.; Reardon, K. P.; Pasachoff, J. M.;
Schneider, G.; Widemann, T.; Tanga, P.
Bibcode: 2013SPD....44..150J
Altcode:
The transit of Venus in June 2012 provided a unique chance to view its
atmosphere as we might see that of a transiting Cytherean exoplanet,
through scattered and refracted illumination from its parent star. We
performed spectroscopy and polarimetry during the transit of Venus
focusing on extracting signatures of CO2 absorption of Venus from the
solar spectrum. Although the predicted CO2 transmission spectrum of
Venus was not particularly strong at 1565 nm, this region of the H-band
often used in magnetic-field studies of the Sun's photosphere provides
a particularly flat solar continuum with few atmospheric and molecular
lines. Observations of Venus were taken throughout first contact
and on the solar disk using the Facility InfraRed Spectropolarimeter
on the Dunn Solar Telescope at the National Solar Observatory. The
transit also provided a unique opportunity to investigate instrumental
effects. In this poster we discuss initial results from the transit,
including estimates for an exoplanet detection of this kind, preliminary
comparison with atmospheric models, and the stray light properties
of the instrument. This work was performed in collaboration with the
Williams College Venus transit expedition, which was sponsored by Natl
Geog/Comm for Research and Exploration.
Title: First Results from the EUNIS 2013 Sounding Rocket Campaign
Authors: Daw, Adrian N.; Rabin, D. M.; Brosius, J. W.; Haas, J. P.;
Plummer, T.; Cauzzi, G.; Reardon, K. P.; Beck, C.
Bibcode: 2013SPD....4410501D
Altcode:
The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS)
sounding rocket launched 23 April 2013 at 17:30 UT, as part of a
campaign including co-ordinated observations with the Dunn Solar
Telescope/IBIS, Hinode/EIS, SoHO/CDS, RHESSI and SDO. EUNIS obtained
the highest-resolution observations of the solar spectrum from 52-63 nm
observed to date, as well as observations with the previously-flown
waveband from 30-37 nm. The broad spectral coverage of the EUV
observations includes emission lines of ionization stages from He I to
Fe XIX, and thus a wide temperature range of 0.025 to 10 MK. Absolute
radiometric calibration of EUNIS provides underflight calibration of
CDS, EIS and AIA. Spectra were obtained with a 1.3 s cadence as the
660-arcsec long slit was rastered across two different regions. The
observations captured a B-class flare in active region NOAA 11726 as
well as active regions 11723, 11724, off-limb, quiet sun and a coronal
hole. We discuss first results from anaysis of this rich and extensive
data set.
Title: High-cadence and High-resolution Hα Imaging Spectroscopy of
a Circular Flare's Remote Ribbon with IBIS
Authors: Deng, Na; Tritschler, Alexandra; Jing, Ju; Chen, Xin; Liu,
Chang; Reardon, Kevin; Denker, Carsten; Xu, Yan; Wang, Haimin
Bibcode: 2013ApJ...769..112D
Altcode: 2013arXiv1304.4171D
We present an unprecedented high-resolution Hα imaging spectroscopic
observation of a C4.1 flare taken with the Interferometric Bidimensional
Spectrometer (IBIS) in conjunction with the adaptive optics system
at the 76 cm Dunn Solar Telescope on 2011 October 22 in the active
region NOAA 11324. Such a two-dimensional spectroscopic observation
covering the entire evolution of a flare ribbon with high spatial (0.''1
pixel-1 image scale), cadence (4.8 s), and spectral (0.1 Å
step size) resolution is rarely reported. The flare consists of a main
circular ribbon that occurred in a parasitic magnetic configuration and
a remote ribbon that was observed by the IBIS. Such a circular-ribbon
flare with a remote brightening is predicted in three-dimensional
fan-spine reconnection but so far has been rarely studied. During
the flare impulsive phase, we define "core" and "halo" structures in
the observed ribbon based on IBIS narrowband images in the Hα line
wing and line center. Examining the Hα emission spectra averaged in
the flare core and halo areas, we find that only those from the flare
cores show typical nonthermal electron beam heating characteristics that
have been revealed by previous theoretical simulations and observations
of flaring Hα line profiles. These characteristics include broad and
centrally reversed emission spectra, excess emission in the red wing
with regard to the blue wing (i.e., red asymmetry), and redshifted
bisectors of the emission spectra. We also observe rather quick
timescales for the heating (~30 s) and cooling (~14-33 s) in the flare
core locations. Therefore, we suggest that the flare cores revealed by
IBIS track the sites of electron beam precipitation with exceptional
spatial and temporal resolution. The flare cores show two-stage
motion (a parallel motion along the ribbon followed by an expansion
motion perpendicular to the ribbon) during the two impulsive phases
of the flare. Some cores jump quickly (30 km s-1) between
discrete magnetic elements implying reconnection involving different
flux tubes. We observe a very high temporal correlation (gsim 0.9)
between the integrated Hα and hard X-rays (HXR) emission during the
flare impulsive phase. A short time delay (4.6 s) is also found in the
Hα emission spikes relative to HXR bursts. The ionization timescale
of the cool chromosphere and the extra time taken for the electrons
to travel to the remote ribbon site may contribute to this delay.
Title: Transit Observations of Venus's Atmosphere in 2012 from
Terrestrial and Space Telescopes as Exoplanet Analogs
Authors: Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.;
Penn, M. J.; Jaeggli, S. A.; Galayda, E.; Reardon, K. P.; Widemann,
T.; Tanga, P.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson, P. D.;
Dantowitz, R.
Bibcode: 2013AAS...22221701P
Altcode:
We extensively observed the 8 June 2012 transit of Venus from several
sites on Earth; we provide this interim status report about this and
about two subsequent ToVs observed from space. From Haleakala Obs., we
observed the entire June transit over almost 7 h with a coronagraph of
the Venus Twilight Experiment B filter) and with a RED Epic camera to
compare with simultaneous data from ESA's Venus Express, to study the
Cytherean mesosphere; from Kitt Peak, we have near-IR spectropolarimetry
at 1.6 µm from the aureole and during the disk crossing that compare
well with carbon dioxide spectral models; from Sac Peak/IBIS we have
high-resolution imaging of the Cytherean aureole for 22 min, starting
even before 1st contact; from Big Bear, we have high-resolution imaging
of Venus's atmosphere and the black-drop effect through 2nd contact;
and we had 8 other coronagraphs around the world. For the Sept 21 ToV
as seen from Jupiter, we had 14 orbits of HST to use Jupiter's clouds
as a reflecting surface to search for an 0.01% diminution in light and a
differential drop that would result from Venus's atmosphere by observing
in both IR/UV, for which we have 170 HST exposures. As of this writing,
preliminary data reduction indicates that variations in Jovian clouds
and the two periods of Jupiter's rotation will be too great to allow
extraction of the transit signal. For the December 20 ToV as seen from
Saturn, we had 22 hours of observing time with VIMS on Cassini, for
which we are looking for a signal of the 10-hr transit in total solar
irradiance and of Venus's atmosphere in IR as an exoplanet-transit
analog. Our Maui & Sac Peak expedition was sponsored by National
Geographic Society's Committee for Research and Exploration; HST data
reduction by NASA: HST-GO-13067. Some of the funds for the carbon
dioxide filter for Sac Peak provided by NASA through AAS's Small
Research Grant Program. We thank Rob Ratkowski of Haleakala Amateur
Astronomers; Rob Lucas, Aram Friedman, Eric Pilger, Stan Truitt,
and Steve Bisque/Software Bisque for Haleakala support/operations;
Vasyl Yurchyshyn and Joseph Gangestad '06 of The Aerospace Corp. at
Big Bear Solar Obs; LMSAL and Hinode science/operations team.
Title: Statistical Analysis of Small Ellerman Bomb Events
Authors: Nelson, C. J.; Doyle, J. G.; Erdélyi, R.; Huang, Z.;
Madjarska, M. S.; Mathioudakis, M.; Mumford, S. J.; Reardon, K.
Bibcode: 2013SoPh..283..307N
Altcode: 2013arXiv1301.1351N
The properties of Ellerman bombs (EBs), small-scale brightenings in
the Hα line wings, have proved difficult to establish because their
size is close to the spatial resolution of even the most advanced
telescopes. Here, we aim to infer the size and lifetime of EBs using
high-resolution data of an emerging active region collected using
the Interferometric BIdimensional Spectrometer (IBIS) and Rapid
Oscillations of the Solar Atmosphere (ROSA) instruments as well as
the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO). We develop an algorithm to track EBs through their
evolution, finding that EBs can often be much smaller (around 0.3″)
and shorter-lived (less than one minute) than previous estimates. A
correlation between G-band magnetic bright points and EBs is also
found. Combining SDO/HMI and G-band data gives a good proxy of the
polarity for the vertical magnetic field. It is found that EBs often
occur both over regions of opposite polarity flux and strong unipolar
fields, possibly hinting at magnetic reconnection as a driver of these
events.The energetics of EB events is found to follow a power-law
distribution in the range of a nanoflare (1022−25 ergs).
Title: Coordinated Observations of On-Disk Type II Spicules with
IBIS and Hinode
Authors: Chen, Xin; Deng, Na; Jing, Ju; Tritschler, Alexandria;
Reardon, Kevin; Wang, Haimin
Bibcode: 2013enss.confE.147C
Altcode:
Ubiquitous small-scale spicules/jets in the chromosphere are believed
to be an important ingredient contributing to coronal heating and
solar wind by supplying energy and mass upwards. In particular, type II
spicules discovered at the solar limb (De Pontieu et al. 2007) and their
highly probable chromospheric on disk counterpart "Rapid Blueshifted
Excursions" (RBEs; Langangen et al. 2008) have drawn much attention in
recent years. Their rapid heating, high speed upflow and association
with magnetic field indicate that the most possible underlying
driving mechanism is magnetic reconnection on small scales. In order
to understand the physical properties of these features, we carried
out a coordinated high resolution and high cadence observation of
chromospheric RBEs using the Interferometric BIdimensional Spectrometer
(IBIS) at the Dunn Solar Telescope and photospheric magnetic fields
using Hinode SOT/SP and SOT/NFI in October 2011. We identify RBEs based
on the IBIS observations, study their properties (velocity, density,
temperature etc.) by statistical analysis and show their relationship
with signatures of small-scale magnetic reconnection in the Hinode
magnetograms. Furthermore, we search for coronal counterpart of RBEs
from observations of the Atmospheric Imaging Assembly (AIA) onboard
the Solar Dynamics Observatory (SDO). References: De Pontieu, B. et
al. 2007, PASJ, 59, 655-662 Langangen, O. et al. 2008, ApJ, 679, L167
Title: Three 2012 Transits of Venus: From Earth, Jupiter, and Saturn
Authors: Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.;
Edelman, E.; Reardon, K.; Widemann, T.; Tanga, P.; Dantowitz, R.;
Silverstone, M. D.; Ehrenreich, D.; Vidal-Madjar, A.; Nicholson,
P. D.; Willson, R. C.; Kopp, G. A.; Yurchyshyn, V. B.; Sterling,
A. C.; Scherrer, P. H.; Schou, J.; Golub, L.; McCauley, P.; Reeves, K.
Bibcode: 2013AAS...22131506P
Altcode:
We observed the 2012 June 6/5 transit seen from Earth (E/ToV),
simultaneously with Venus Express and several other spacecraft
not only to study the Cytherean atmosphere but also to provide an
exoplanet-transit analog. From Haleakala, the whole transit was visible
in coronal skies; among our instruments was one of the world-wide Venus
Twilight Experiment's nine coronagraphs. Venus's atmosphere became
visible before first contact. SacPeak/IBIS provided high-resolution
images at Hα/carbon-dioxide. Big Bear's NST also provided
high-resolution observations of the Cytherean atmosphere and black-drop
evolution. Our liaison with UH's Mees Solar Observatory scientists
provided magneto-optical imaging at calcium and potassium. Solar
Dynamics Observatory's AIA and HMI, and the Solar Optical Telescope
(SOT) and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance
measurements with ACRIMSAT and SORCE/TIM, were used to observe the
event as an exoplanet-transit analog. On September 20, we imaged
Jupiter for 14 Hubble Space Telescope orbits, centered on a 10-hour
ToV visible from Jupiter (J/ToV), as an exoplanet-transit analog in
our own solar system, using Jupiter as an integrating sphere. Imaging
was good, although much work remains to determine if we can detect
the expected 0.01% solar irradiance decrease at Jupiter and the even
slighter differential effect between our violet and near-infrared
filters caused by Venus's atmosphere. We also give a first report on our
currently planned December 21 Cassini UVIS observations of a transit of
Venus from Saturn (S/ToV). Our E/ToV expedition was sponsored by the
Committee for Research and Exploration/National Geographic Society;
supplemented: NASA/AAS's Small Research Grant Program. We thank Rob
Ratkowski, Stan Truitt, Rob Lucas, Aram Friedman, and Eric Pilger
'82 at Haleakala, and Joseph Gangestad '06 at Big Bear for assistance,
and Lockheed Martin Solar and Astrophysics Lab and Hinode science and
operations teams for support for coordinated observations with NASA
satellites. Our J/ToV observations were based on observations made
with HST, operated by AURA, Inc., under NASA contract NAS 5-26555;
these observations are associated with program #13067.
Title: The 2012 Transit of Venus: A Closer Look at the Cytherean
Aureole
Authors: Edelman, Eric; Pasachoff, J. M.; Schneider, G.; Babcock,
B. A.; Lu, M.; Reardon, K.; Widemann, T.; Tanga, P.; Dantowitz, R.
Bibcode: 2013AAS...22135304E
Altcode:
The 2012 Transit of Venus provided a new opportunity to study the
events that occur during the ingress and egress of transit in greater
detail. The Venus Twilight Experiment is a group that was formed to
analyze the twilight phenomena of Venus through close and careful
observation of planet’s 21st century transits. One particular object
of interest to this group is the Cytherean aureole, or the arc of light
caused by refraction of the Sun’s light through Venus’s upper
atmosphere. A goal associated with the study of this aureole is to
measure how the brightness of the atmosphere changes over time and as
a function of latitude on Venus with the use of the multitude of images
taken of the planet near the beginning and end of the transit. In order
to further along this goal, I was tasked with sorting, processing,
and aligning the images taken by the coronagraph used on the 2012
Williams College Transit of Venus Expedition at Haleakala, Hawaii. Our
observations through a B filter will be compared with observations
through VRI-filter observations from other coronagraphs in the set. This
was research was performed with the support of the Keck Northeast
Astronomy Consortium, sponsored by the NSF and the Keck foundation. The
expedition to Haleakala and Sac Peak was sponsored by the Committee
for Research and Exploration/National Geographic Society. Some funds
for the IBIS carbon-dioxide filter came from NASA/AAS's Small Research
Grant Program. We thank Rob Ratkowski, Stan Truitt, Rob Lucas, Aram
Friedman, and Eric Pilger '82 for assistance with Haleakala observing.
Title: Halpha Imaging Spectroscopy of a C-class flare with IBIS
Authors: Deng, N.; Tritschler, A.; Jing, J.; Chen, X.; Reardon, K.;
Liu, C.; Xu, Y.; Wang, H.
Bibcode: 2012IAUSS...6E.307D
Altcode:
We present a rare high cadence and high spatial resolution spectroscopic
observation of a C4.1 Flare taken with the Interferometric Bidimensional
Spectrometer (IBIS) in conjunction with the adaptive optics system at
the 76 cm Dunn Solar Telescope on 2011 October 22 in NOAA AR 11324. The
IBIS with a round FOV of 90" x 90" and 0.1"/pixel detector image scale
scanned the Halpha line from 6561.1 to 6563.8 Angstrom with 0.1 Angstrom
stepsize for 28 steps. Each scan takes about 4.8 s. The flare occurred
in a mixed polarity region with two parasite configurations. The
flare shows multiple bright ribbons in the chromosphere spreading
over a region of 120" x 60". IBIS observed a remote ribbon of the
flare and fully covered its temporal evolution. The Halpha emission
integrated over this ribbon area exhibits several bursts over four
minutes during the flare impulsive phase that are temporally correlated
with the subpeaks of RHESSI hard X-ray (HXR) light curves. During the
strong bursts of the Halpha emission, we observe a central reversal
patten in the Halpha line core, which is believed to be a signature of
nonthermal process caused by direct electron precipitation. The line
core shows blueward shift that increases with the Halpha emission,
which might be related to chromospheric evaporation. The Halpha
emission is stronger in the red wing than in the blue wing during the
strong bursts. Substructures within the ribbon are also identified. A
bright core feature that is 30% brighter than the entire ribbon moves
at an apparent velocity of about 30 km/s within the ribbon during the
strongest burst of Halpha emission co-temporal with a strong subpeak of
HXR. The bright core disappeared in the decay phase of the flare. We
suggest that this running bright core feature tracks the site of
electron precipitation.
Title: The IBIS Mosaic
Authors: Cauzzi, G.; Reardon, K.
Bibcode: 2012IAUSS...6E.511C
Altcode:
Existing and planned instrumentation for large solar telescopes is
tailored to exploit the high spatial resolution affordable with such
facilities. However, the typical instrumental tradeoffs restrict the
field-of-view accessible at once to rather small areas (well below
100" diameter): this represents a serious impediment for study of
the active Sun, where large scale magnetic connectivity is of much
relevance. Mosaicking offers a possibility to obtain high-resolution
observations over a large FOV, but the technique has been only
sparsely utilized at ground-based, optical telescopes. In this poster
we report on an investigation of the feasibility and utility of mosaic
observations with a state-of-the-art facility, the Interferometric
BIdimensional Spectrometer instrument (IBIS) installed at the Dunn
Solar Telescope (NSO). We obtained a 3 x 3 mosaic, covering the full
AR NOAA 11092 for a total field in excess of 4' x 4', sampling both
photospheric and chromospheric lines. We report on the methods utilized
for observation and assembly of the data cubes, and some preliminary
comparisons with simultaneous observations from other instruments.
Title: The Source of 3 Minute Magnetoacoustic Oscillations in
Coronal Fans
Authors: Jess, D. B.; De Moortel, I.; Mathioudakis, M.; Christian,
D. J.; Reardon, K. P.; Keys, P. H.; Keenan, F. P.
Bibcode: 2012ApJ...757..160J
Altcode: 2012arXiv1208.3194J
We use images of high spatial, spectral, and temporal resolution,
obtained using both ground- and space-based instrumentation, to
investigate the coupling between wave phenomena observed at numerous
heights in the solar atmosphere. Analysis of 4170 Å continuum images
reveals small-scale umbral intensity enhancements, with diameters
~0farcs6, lasting in excess of 30 minutes. Intensity oscillations
of ≈3 minutes are observed to encompass these photospheric
structures, with power at least three orders of magnitude higher
than the surrounding umbra. Simultaneous chromospheric velocity and
intensity time series reveal an 87° ± 8° out-of-phase behavior,
implying the presence of standing modes created as a result of
partial wave reflection at the transition region boundary. We find a
maximum waveguide inclination angle of ≈40° between photospheric
and chromospheric heights, combined with a radial expansion factor
of <76%. An average blueshifted Doppler velocity of ≈1.5 km
s-1, in addition to a time lag between photospheric and
chromospheric oscillatory phenomena, confirms the presence of upwardly
propagating slow-mode waves in the lower solar atmosphere. Propagating
oscillations in EUV intensity are detected in simultaneous coronal
fan structures, with a periodicity of 172 ± 17 s and a propagation
velocity of 45 ± 7 km s-1. Numerical simulations reveal that
the damping of the magnetoacoustic wave trains is dominated by thermal
conduction. The coronal fans are seen to anchor into the photosphere
in locations where large-amplitude umbral dot (UD) oscillations
manifest. Derived kinetic temperature and emission measure time series
display prominent out-of-phase characteristics, and when combined with
the previously established sub-sonic wave speeds, we conclude that
the observed EUV waves are the coronal counterparts of the upwardly
propagating magnetoacoustic slow modes detected in the lower solar
atmosphere. Thus, for the first time, we reveal how the propagation
of 3 minute magnetoacoustic waves in solar coronal structures is a
direct result of amplitude enhancements occurring in photospheric UDs.
Title: Observation of Neutral Sodium above Mercury During the Transit
of November 8, 2006
Authors: Potter, Andrew E.; Killen, R. M.; Reardon, K. P.; Bida, T. A.
Bibcode: 2012DPS....4441001P
Altcode:
We mapped the absorption of sunlight by sodium vapor in the exosphere of
Mercury during the transit of Mercury on November 8, 2006, using the
IBIS Interferometric BIdimensional Spectrometer at the Dunn solar
telescope operated by the National Solar Observatory at Sunspot,
New Mexico. The measurements were reduced to line-of-sight equivalent
widths for absorption at the sodium D2 line, and mapped in thirty degree
increments around the shadow of Mercury. We observed north and south
polar enhancements of sodium absorption. The sodium absorptions fell
off exponentially with altitude up to about 600 km, and we analyzed
the altitude distributions to determine surface densities, zenith
column densities, temperatures and scale heights for sodium. The
average surface concentration of sodium atoms was about 900 atoms/cm3,
and the average zenith column density was 0.8 x 1010 atoms/cm2. The
average temperature was about 1100 K, with excursions to 1750 and
700 K. The 2003 transit was observed by Schleicher et al. [2004],
using instrumentation similar to that employed for this research. They
reported the appearance of a streamer-like feature extending a thousand
kilometers above the north polar region, and a similar but smaller
feature above the south polar region. Our observations did not detect
similar features. They observed considerably more sodium absorption
over the dawn terminator than over the dusk terminator. In contrast,
we observed slightly larger sodium absorption on the dawn relative
to the dusk side. The difference might be due to the slow advance
of the dawn terminator at during the 2006 transit (0.13 degrees/day)
relative to the 2003 transit (3.27 degrees/day). Reference Schleicher,
H.; Wiedemann, G.; Wöhl, H.; Berkefeld, T.; Soltau, D. (2004),
Detection of neutral sodium above Mercury during the transit on 2003
May 7. Astronomy and Astrophysics, 425, 1119-1124
Title: The 2012 Transit of Venus for Cytherean Atmospheric Studies
and as an Exoplanet Analog
Authors: Pasachoff, Jay M.; Schneider, G.; Babcock, B. A.; Lu, M.;
Reardon, K. P.; Widemann, T.; Tanga, P.; Dantowitz, R.; Willson,
R.; Kopp, G.; Yurchyshyn, V.; Sterling, A.; Scherrer, P.; Schou, J.;
Golub, L.; Reeves, K.
Bibcode: 2012DPS....4450806P
Altcode:
We worked to assemble as complete a dataset as possible for the
Cytherean atmosphere in collaboration with Venus Express in situ
and to provide an analog of spectral and total irradiance exoplanet
measurements. From Haleakala, the whole transit was visible in
coronal skies; our B images showed the evolution of the visibility
of Venus's atmosphere and of the black-drop effect, as part of the
Venus Twilight Experiment's 9 coronagraphs distributed worldwide
with BVRI. We imaged the Cytherean atmosphere over two minutes before
first contact, with subarcsecond resolution, with the coronagraph and
a separate refractor. The IBIS imaging spectrometer at Sacramento
Peak Observatory at H-alpha and carbon-dioxide also provided us
high-resolution imaging. The NST of Big Bear Solar Observatory
also provided high-resolution vacuum observations of the Cytherean
atmosphere and black drop evolution. Our liaison with UH's Mees Solar
Observatory scientists provided magneto-optical imaging at calcium
and potassium. Spaceborne observations included the Solar Dynamics
Observatory's AIA and HMI, and the Solar Optical Telescope (SOT)
and X-ray Telescope (XRT) on Hinode, and total-solar-irradiance
measurements with ACRIMSAT and SORCE/TIM, to characterize the
event as an exoplanet-transit analog. Our expedition was sponsored
by the Committee for Research and Exploration/National Geographic
Society. Some of the funds for the carbon-dioxide filter for IBIS were
provided by NASA through AAS's Small Research Grant Program. We thank
Rob Lucas, Aram Friedman, and Eric Pilger '82 for assistance with
Haleakala observing, Rob Ratkowski of Haleakala Amateur Astronomers
for assistance with equipment and with the site, Stan Truitt for the
loan of his Paramount ME, and Steve Bisque/Software Bisque for TheSky
X controller. We thank Joseph Gangestad '06 of Aerospace Corp., a
veteran of our 2004 expedition, for assistance at Big Bear. We thank
the Lockheed Martin Solar and Astrophysics Laboratory and Hinode
science and operations teams for planning and support.
Title: Assymetry in the Polar Mesosphere Revealed by the 2012 Venus
Transit Aureole
Authors: Widemann, Thomas; Tanga, P.; Reardon, K. P.; Limaye, S.;
Wilson, C.; Vandaele, A.; Wilquet, V.; Mahieux, A.; Robert, S.;
Pasachoff, J. M.; Schneider, G.
Bibcode: 2012DPS....4450808W
Altcode:
Close to ingress and egress phases, the fraction of Venus disk projected
outside the solar photosphere appears outlined by an irregular thin
arc of light called the "aureole." We have shown that the deviation
due to refraction and the aureole intensity are related to the local
density scale height and the altitude of the refraction layer (Tanga
et al. 2012). Since the aureole brightness is the quantity that can be
measured during the transit, an appropriate model allows us to determine
both parameters. We now compare this model developed for the 2004
data to the first results of 2012 campaign. Ingress pictures of NASA's
SDO/HMI observations, OP-OCA/VTE coronagraph observations at Haleakala
and Lowell stations, and Dunn/IBIS observations at Sacramento Peak, NM,
show latitudinal structure of the aureole during the ingress phase of
the Venus transit. For the HMI data, the temporal cadence is 3.75 sec
and the pixel scale is 0.5 arcsec/pixel. The polar region, significantly
brighter in initial phases due to the larger scale height of the polar
mesosphere, appears consistently offset toward morning terminator by
about 15 deg. latitude, peaking at 75N at 6:00 local time. This result
reflects local latitudinal structure in the polar mesosphere, either in
temperature or aerosol altitude distribution. Relation with ESA / Venus
Express / SOIR simultaneous measurements and dynamical interpretation
will be discussed at the meeting. Tanga et al. 2012, Icarus 218, 207-219
Title: Conceptual design of the data handling system for the European
Solar Telescope
Authors: Ermolli, Ilaria; Cauzzi, Gianna; Collados, Manuel; Paletou,
Frederic; Reardon, Kevin; Aboudarham, Jean; Cirami, Roberto; Cosentino,
Rosario; Del Moro, Dario; Di Marcantonio, Paolo; Giorgi, Fabrizio;
Lafon, Martine; Pietropaolo, Ermanno; Romano, Paolo
Bibcode: 2012SPIE.8448E..1SE
Altcode:
We present an overview of the conceptual design of the data handling
unit of the ECS, the Control System for the European Solar Telescope
(EST). We will focus on describing the critical requirements for this
unit resulting from the overall design of the telescope, together with
its architecture and the results of the feasibility analysis carried
out to date.
Title: Evidence for Sheet-like Elementary Structures in the Sun's
Atmosphere?
Authors: Judge, Philip G.; Reardon, Kevin; Cauzzi, Gianna
Bibcode: 2012ApJ...755L..11J
Altcode:
Narrow, thread-like structures in the Sun's chromosphere are currently
understood to be plasma guided along narrow tubes of magnetic flux. We
report on 1 s cadence imaging spectroscopic measurements of the Hα
line with the IBIS Fabry-Pérot instrument at the Dunn Solar Telescope,
obtained +0.11 nm from line center. Rapid changes grossly exceeding
the Alfvén speed are commonly seen along the full extent of many
chromospheric threads. We argue that only an optical superposition
effect can reasonably explain the data, analogous to striations of
curtains blowing in the wind. Other explanations appear to require
significant contrivances to avoid contradicting various aspects of
the data. We infer that the absorbing plasma exists in two-dimensional
sheet-like structures within the three-dimensional magnetofluid, related
perhaps to magnetic tangential discontinuities. This interpretation
demands a re-evaluation of basic assumptions about low-β solar plasmas,
as advocated by Parker, with broader implications in astrophysics
and plasma physics. Diverse, high-cadence observations are needed to
further define the relationship between magnetic field and thermal
fine structure.
Title: Helium D3 at High Resolution
Authors: Reardon, Kevin P.
Bibcode: 2012AAS...22020301R
Altcode:
We present high-resolution observations of the Helium D3 (587.6 nm)
line obtained with the IBIS imaging spectrometer at the Dunn Solar
Telescope. The D3 line is observed both on-disk and off-limb in a
variety of solar features. These observations reveal that structures
in this line are both finely structured (at our resolution limit of
0.2 arcsec) and highly dynamic. We use the observed spectral profiles
to derive information on the local atmospheric properties. We compare
the appearance of the D3 line with features seen in simultaneous Hα
and Ca II 854.2 nm chromospheric observations, as well as SDO/AIA
images of the transition region and corona. The fibrils observed in
the He D3 line provide useful information on connectivity from the
chromospheric layers up into the corona.
Title: The IBIS Mosaic - A Broad View Of The Solar Atmosphere
Authors: Reardon, Kevin P.; Cauzzi, G.
Bibcode: 2012AAS...22020111R
Altcode:
We present a unique set of observations spanning the photosphere and
chromosphere with a large field-of-view (4 x 4 arcminutes) ,high-spatial
resolution (0.1"/pixel), and full spectral profiles (R ∼ 200,000). The
data were obtained with the IBIS imaging spectrometer at the NSO/Dunn
Solar Telescope on August 3, 2010 using a mosaic technique to tile an
active region and surrounding areas. Spectral profiles were obtained
in the chromospheric Hα, CaII 854.2 nm, and He I D3 lines, as well as
photospheric FeI 543.4 nm. Combining this dataset with simultaneous
SDO/AIA and SDO/HMI images and magnetic field measurements allow a
highly comprehensive view of an entire volume of the solar atmosphere
from photosphere to corona. The wealth of information is used to
explore the nature of the chromospheric fibrillar structures and their
relationship with the overlying corona.
Title: Evidence for Two Separate But Interlaced Components of the
Chromospheric Magnetic Field
Authors: Muglach, Karin; Reardon, K.; Wang, Y.; Warren, H.
Bibcode: 2012AAS...22012403M
Altcode:
Chromospheric fibrils are generally thought to trace out horizontal
magnetic fields that fan out from flux concentrations in the
photosphere. A high-resolution (0.2") image taken in the core of the
Ca II 854.2 nm line shows the dark fibrils within an active region
remnant as fine, looplike features that are aligned parallel to each
other and have lengths on the order of a supergranular diameter ( 30
Mm). Comparison with a line-of-sight magnetogram confirms that the
fibrils are centered above intranetwork areas, with one end rooted
just inside the neighboring plage or strong unipolar network
but the other endpoint less clearly defined. Focusing on a particular
arcade-like structure lying entirely on one side of a filament channel
(large-scale polarity inversion), we find that the total amount of
positive-polarity flux underlying this ``fibril arcade'' is 50 times
greater than the total amount of negative-polarity flux. Thus, if the
fibrils represent closed loops, they must consist of very weak fields
(in terms of flux density), which are interpenetrated by a more vertical
field that contains most of the flux. This surprising result suggests
that the fibrils in unipolar regions connect the network to the nearby
intranetwork flux, while the bulk of the network flux is diverted
upward into the corona and connects to remote regions of the opposite
polarity. We conclude that the chromospheric field near the edge of
the network has an interlaced structure resembling that in sunspot
penumbrae, with the fibrils representing the low-lying horizontal flux
that remains trapped within the highly nonpotential chromospheric layer.
Title: ATST Data Distribution and Analysis
Authors: Reardon, Kevin P.
Bibcode: 2012AAS...22032305R
Altcode:
The Advanced Technology Solar Telescope will be a key research
facility for solar physics in the coming decade. ATST will produce
large volumes of data covering the full solar atmosphere. The objective
is to turn this stream of images and spectra into well-calibrated data
products useful for the broad solar physics community. Some of the data
processing challenges include managing the tens of terabytes of data
that can be produced on a daily basis, the correction of distortions
produced by the terrestrial atmosphere, and the extraction of physical
parameters from the high-resolution observations. We will describe
the approaches we will take in addressing these issues, as well as
the ways in which the ATST data can be integrated with other data
resources and made available through the VSO.
Title: X-Ray Searches for Solar Axions
Authors: Hudson, H. S.; Acton, L. W.; DeLuca, E. E.; Hannah, I. G.;
Reardon, K.; Van Bibber, K.
Bibcode: 2012ASPC..455...25H
Altcode: 2012arXiv1201.4607H
Axions generated thermally in the solar core can convert nearly directly
to X-rays as they pass through the solar atmosphere via interaction with
the magnetic field. The result of this conversion process would be a
diffuse centrally-concentrated source of few-keV X-rays at disk center;
it would have a known dimension, of order 10% of the solar diameter, and
a spectral distribution resembling the blackbody spectrum of the solar
core. Its spatial structure in detail would depend on the distribution
of mass and field in the solar atmosphere. The brightness of the source
depends upon these factors as well as the unknown coupling constant
and the unknown mass of the axion; this particle is hypothetical and
no firm evidence for its existence has been found yet. We describe the
solar magnetic environment as an axion/photon converter and discuss
the upper limits obtained by existing and dedicated observations from
three solar X-ray observatories: Yohkoh, RHESSI, and Hinode.
Title: High Cadence and High Resolution Halpha Imaging Spectroscopy
of a C4.1 Flare with IBIS
Authors: Deng, Na; Tritschler, A.; Jing, J.; Chen, X.; Reardon, K.;
Liu, C.; Xu, Y.; Wang, H.
Bibcode: 2012AAS...22020449D
Altcode:
We present a rare high cadence and high spatial resolution spectroscopic
observation of a C4.1 Flare taken with the Interferometric Bidimensional
Spectrometer (IBIS) in conjunction with the adaptive optics system at
the 76cm Dunn Solar Telescope on 2011 October 22 in NOAA AR11324. The
IBIS with a round FOV of 90"X90" and 0.1"/pix detector image scale
scanned the Halpha line from 6561.1 to 6563.8 A with 0.1 A stepsize for
28 steps. Each scan takes about 4.8s. The flare occurred in a mixed
polarity region with two parasite configurations. The flare shows
multiple bright ribbons in the chromosphere spreading over a region
of 120"X60". IBIS observed a remote ribbon of the flare and fully
covered its temporal evolution. The Halpha emission integrated over
this ribbon area exhibits several bursts over four minutes during the
flare impulsive phase that are temporally correlated with the subpeaks
of RHESSI hard X-ray (HXR) light curves. During the strongest burst of
the Halpha emission, we observe a central reversal patten in the Halpha
line core, which is believed to be a signature of nonthermal process
caused by direct electron precipitation. The line core shows blueward
shift that increases with the Halpha emission, which might be related
to chromospheric evaporation. The line width also increases with the
emission. The Halpha emission is stronger in the red wing than in the
blue wing during the strong bursts. Substructures within the ribbon are
also identified. A bright core feature that is 30% brighter than the
entire ribbon moves at an apparent velocity of about 30 km/s within
the ribbon during the strongest burst of Halpha emission co-temporal
with a strong subpeak of HXR. The bright core disappeared in the decay
phase of the flare. We suggest that this running bright core feature
tracks the site of electron precipitation.
Title: Coordinated Observations Of On-disk Type II Spicules With
IBIS And Hinode
Authors: Chen, Xin; Na, D.; Jing, J.; Tritschler, A.; Reardon, K.;
Wang, H.
Bibcode: 2012AAS...22020310C
Altcode:
Ubiquitous small-scale spicules/jets in the chromosphere are believed
to be an important ingredient contributing to coronal heating and
solar wind by supplying energy and mass upwards. In particular, type II
spicules discovered at the solar limb (De Pontieu et al. 2007) and their
highly probable chromospheric on disk counterpart "Rapid Blueshifted
Excursions" (RBEs; Langangen et al. 2008) have drawn much attention in
recent years. Their rapid heating, high speed upflow and association
with magnetic field indicate that the most possible underlying
driving mechanism is magnetic reconnection on small scales. In order
to understand the physical properties of these features, we carried
out a coordinated high resolution and high cadence observation of
chromospheric RBEs using the Interferometric BIdimensional Spectrometer
(IBIS) at the Dunn Solar Telescope and photospheric magnetic fields
using Hinode SOT/SP and SOT/NFI in October 2011. Different targets near
disk center were observed, such as quite sun and active regions. For
each target region, both Halpha and Ca II 854.2 nm lines were scanned
by IBIS with high-spatial ( 0.1 arcsec/pixel, with adaptive optics),
high-temporal ( 6s) and moderate-spectral ( 0.1 angstrom) resolution. At
the same time Hinode/SP and NFI pointing at the same area providing the
geometry and time evolution of photospheric magnetic fields, such as
flux emergence, convergence and cancellation on small spatial scales. We
identify RBEs based on the IBIS observations, study their properties
(velocity, density, temperature and statistical distribution) and search
for signatures of small-scale magnetic reconnection in the Hinode
magnetograms. The poster will show the details of the temporal and
spatial relation between chromospheric RBEs and photospheric magnetic
field activities. References: De Pontieu, B. et al. 2007,
PASJ, 59, 655-662 Langangen, O. et al. 2008, ApJ, 679, L167
Title: New insight on the coupling of the solar atmosphere from
imaging spectroscopy
Authors: Reardon, K.; Cauzzi, G.
Bibcode: 2012decs.confE..20R
Altcode:
We present spectrally resolved, high-resolution observations of
chromospheric diagnostics obtained with IBIS covering a full active
region. In particular, the data includes the first high-resolution
observations of the He I D3 line (587.6 nm), a subordinate of the more
famous HeI 1083.0 nm line, showing loops and other structures on the
solar disk at the 150 km diffraction limit. The large FOV of our data
allows a meaningfully comparison with the SDO full disk observations
to investigate the coupling between different portions of the solar
atmosphere and the topology of the chromospheric magnetic field. The
relationship between the chromospheric signatures and the SDO 304 Å and
171 Å emission provides intriguing hints to the existence of low-lying
loops at TR temperatures effectively disconnected from the corona.
Title: Data handling and control of the European Solar Telescope
Authors: Ermolli, I.; Bettonvil, F.; Cauzzi, G.; Cavaller, L.;
Collados, M.; Di Marcantonio, P.; Grivel, C.; Paletou, F.; Romano,
P.; Aboudarham, J.; Cirami, R.; Cosentino, R.; Giorgi, F.; Lafon,
M.; Laforgue, D.; Reardon, K.; Sliepen, G.
Bibcode: 2012MSAIS..19..380E
Altcode:
We describe some aspects of the facility operation that have been
considered for the design of the data handling and control of the
European Solar Telescope. The main sub-systems of the EST relevant for
the control are summarized, together with some information on current
solar data models.
Title: Evidence for Two Separate but Interlaced Components of the
Chromospheric Magnetic Field
Authors: Reardon, K. P.; Wang, Y. -M.; Muglach, K.; Warren, H. P.
Bibcode: 2011ApJ...742..119R
Altcode:
Chromospheric fibrils are generally thought to trace out low-lying,
mainly horizontal magnetic fields that fan out from flux concentrations
in the photosphere. A high-resolution (~0farcs1 pixel-1)
image, taken in the core of the Ca II 854.2 nm line and covering
an unusually large area, shows the dark fibrils within an active
region remnant as fine, looplike features that are aligned parallel
to each other and have lengths comparable to a supergranular
diameter. Comparison with simultaneous line-of-sight magnetograms
confirms that the fibrils are centered above intranetwork areas
(supergranular cell interiors), with one end rooted just inside the
neighboring plage or strong unipolar network but the other endpoint
less clearly defined. Focusing on a particular arcade-like structure
lying entirely on one side of a filament channel (large-scale polarity
inversion), we find that the total amount of positive-polarity flux
underlying this "fibril arcade" is ~50 times greater than the total
amount of negative-polarity flux. Thus, if the fibrils represent closed
loops, they must consist of very weak fields (in terms of total magnetic
flux), which are interpenetrated by a more vertical field that contains
most of the flux. This surprising result suggests that the fibrils in
unipolar regions connect the network to the nearby intranetwork flux,
while the bulk of the network flux links to remote regions of the
opposite polarity, forming a second, higher canopy above the fibril
canopy. The chromospheric field near the edge of the network thus has
an interlaced structure resembling that in sunspot penumbrae.
Title: Nonpotentiality of Chromospheric Fibrils in NOAA Active
Regions 11092 and 9661
Authors: Jing, Ju; Yuan, Yuan; Reardon, Kevin; Wiegelmann, Thomas;
Xu, Yan; Wang, Haimin
Bibcode: 2011ApJ...739...67J
Altcode:
In this paper, we present a method to automatically segment
chromospheric fibrils from Hα observations and further identify their
orientation. We assume that chromospheric fibrils are aligned with the
magnetic field. By comparing the orientation of the fibrils with the
azimuth of the embedding chromospheric magnetic field extrapolated from
a potential field model, the shear angle, a measure of nonpotentiality,
along the fibrils is readily deduced. Following this approach, we make
a quantitative assessment of the nonpotentiality of fibrils in two NOAA
active regions (ARs): (1) the relatively simple AR 11092, observed with
very high resolution by Interferometric Bidimensional Spectrometer,
and (2) a β-γ-δ AR 9661, observed with median resolution by Big
Bear Solar Observatory before and after an X1.6 flare.
Title: Nonpotentiality of Chromospheric Fibrils in the Active Regions
NOAA 9661 and NOAA 11092
Authors: Jing, Ju; Yuan, Y.; Reardon, K.; Wiegelmann, T.; Deng, N.;
Xu, Y.; Wang, H.
Bibcode: 2011SPD....42.1738J
Altcode: 2011BAAS..43S.1738J
We have developed a method to automatically segment chromospheric
fibrils from Halpha observations and further identify their
orientation. We assume that chromospheric fibrils are magnetic
field-aligned. By comparing the orientation of the fibrils with the
azimuth of the embedding chromospheric magnetic field extrapolated
from the photosphere or chromosphere with the help of a potential
field model, the shear angle, a measure of nonpotentiality, along
the fibrils is readily deduced. Following this approach, we make
a quantitative assessment of the nonpotentiality of fibrils in the
active region NOAA 9661 and NOAA 11092. The spatial distribution and
the histogram of the shear angle along fibrils are presented.
Title: Turbulence in the solar chromosphere and its role in small
scale energy deposition
Authors: Lepreti, F.; Carbone, V.; Vecchio, A.; Reardon, K.;
Capparelli, V.; Rossi, C.
Bibcode: 2010AGUFMSH11B1650L
Altcode:
The line-of-sight velocity fluctuations in the solar chromosphere are
studied. The velocities are obtained from imaging spectral scans in the
chromospheric line Ca II 854.2 nm, acquired at high spatial resolution
with the Interferometric BIdimensional Spectrometer (IBIS) in the
quiet Sun. Nearly power law tails above the acoustic cutoff frequency
in the chromospheric velocity power spectra are found. The probability
density function of chromospheric velocity increments are non-Gaussian
and asymmetric. Intermittency is much larger in the network than in
fibril and internetwork regions. These results suggest that the small
scale velocity fluctuations in the solar chromosphere are the result
of a turbulent cascade generated from acoustic oscillations near the
cutoff frequency. An estimate of the energy flux towards small scales
is given on the basis of third order structure functions of velocity
increments and the possible role of the turbulent cascade for small
scale energy deposition and chromospheric heating is discussed.
Title: Data handling and control for the European Solar Telescope
Authors: Ermolli, Ilaria; Bettonvil, Felix; Cauzzi, Gianna; Cavaller,
Lluis; Collados, Manuel; Di Marcantonio, Paolo; Paletou, Frederic;
Romano, Paolo; Aboudarham, Jean; Cirami, Roberto; Cosentino, Rosario;
Giorgi, Fabrizio; Lafon, Martine; Laforgue, Didier; Reardon, Kevin;
Sliepen, Guus
Bibcode: 2010SPIE.7740E..0GE
Altcode: 2010SPIE.7740E..13E
We introduce the concepts for the control and data handling systems of
the European Solar Telescope (EST), the main functional and technical
requirements for the definition of these systems, and the outcomes
from the trade-off analysis to date. Concerning the telescope control,
EST will have performance requirements similar to those of current
medium-sized night-time telescopes. On the other hand, the science
goals of EST require the simultaneous operation of three instruments
and of a large number of detectors. This leads to a projected data
flux that will be technologically challenging and exceeds that of
most other astronomical projects. We give an overview of the reference
design of the control and data handling systems for the EST to date,
focusing on the more critical and innovative aspects resulting from
the overall design of the telescope.
Title: Imaging performance of multi-etalon bidimensional spectrometers
Authors: Righini, A.; Cavallini, F.; Reardon, K. P.
Bibcode: 2010A&A...515A..85R
Altcode:
Aims: In recent years, several new solar and nighttime
panoramic spectrometers based on Fabry-Perot interferometers have
been successfully developed. In this paper we evaluate the imaging
performance of the two types of mountings that have been adopted,
telecentric and classic, in particular trying to understand which one
might be more suitable for future large-aperture solar telescopes.
Methods: Numerical code was written to simulate the behavior of such
spectrometers, on the basis of the theory of Fourier optics. This code
was used to simulate different instrument configurations and was tested
on previous results obtained either analytically or numerically by
other authors.
Results: Calculations of the system MTF and Strehl
ratios show that both mountings may perform very close to theoretical
expectations. However, gap irregularities in the interferometers
may alter the optical quality of the monochromatic images. In the
case of the classical mounting in a collimated beam, it is possible
to partially compensate for the resulting errors in the wavefront
emerging from the interferometers with a suitable phase plate. We also
performed an observational test of the optical quality delivered by
the IBIS interferometer installed at the Dunn Solar Telescope of the
National Solar Observatory, with the results substantially confirming
the calculations.
Conclusions: It follows from our results
that both mountings may be efficiently used for solar bidimensional
spectroscopy. The final choice depends on the tradeoff between factors
such as image quality, field of view, and acceptable wavelength shift.
Title: Delving into the Chromosphere: New Observational Tools
Authors: Reardon, Kevin P.; Cauzzi, G.; Tritschler, A.; Uitenbroek, H.
Bibcode: 2010AAS...21630503R
Altcode:
The chromosphere lies at the boundary between the near-equilibrium
photosphere and the hot, expanding corona. This region combines both
large interconnecting magnetic structures, and fine-scaled dynamics into
an intriguingly complex whole. Studying this behavior is a significant
observational challenge, requiring sizable fields of view (60-90")
sampled at high spatial (< 0.3") and temporal resolution (< 30
seconds), with full spectral information in multiple lines. We will
describe how instruments based on Fabry-Perot interferometers have
recently begun to routinely deliver such observations. We will review
some of the most exciting results obtained and the deeper insights
they have provided into the characteristics of the solar chromosphere.
Title: SDO Data Access Via The Virtual Solar Observatory
Authors: Hill, Frank; Gurman, J.; Martens, P.; Bogart, R.; Davey, A.;
Hourcle, J.; Suarez Sola, F.; Hughitt, K.; Spencer, J.; Reardon, K.;
Amezcua, A.
Bibcode: 2010AAS...21640218H
Altcode: 2010BAAS...41Q.876H
The launch of SDO brings not only the prospect of new solar physics
discoveries, but also a flood of data. The sustained data rate of
150 Mbs (about 1.6 TB per day) is the highest yet produced by a
solar physics observatory, and the handling of the data requires new
methods. One approach is to distribute the data storage and request
system over a number of distinct sites to reduce the bandwidth
requirements at a single location. The VSO, in conjunction with the
Joint Science and Operations Center (JSOC) at Stanford and a network of
partial archive sites currently at CfA, NSO, ROB, and MPIS, is now able
to provide metadata search and data retrieval services for the SDO AIA
and HMI instruments. EVE data will also be included in the future. This
talk will describe how SDO data can be accessed via the VSO.
Title: The Quiet Solar Atmosphere Observed and Simulated in Na
I D1
Authors: Leenaarts, J.; Rutten, R. J.; Reardon, K.; Carlsson, M.;
Hansteen, V.
Bibcode: 2010ApJ...709.1362L
Altcode: 2009arXiv0912.2206L
The Na I D1 line in the solar spectrum is sometimes
attributed to the solar chromosphere. We study its formation in
quiet-Sun network and internetwork. We first present high-resolution
profile-resolved images taken in this line with the imaging
spectrometer Interferometric Bidimensional Spectrometer at the Dunn
Solar Telescope and compare these to simultaneous chromospheric images
taken in Ca II 8542 Å and Hα. We then model Na I D1
formation by performing three-dimensional (3D) non-local
thermodynamic equilibrium profile synthesis for a snapshot from a
3D radiation-magnetohydrodynamics simulation. We find that most Na I
D1 brightness is not chromospheric but samples the magnetic
concentrations that make up the quiet-Sun network in the photosphere,
well below the height where they merge into chromospheric canopies,
with aureoles from 3D resonance scattering. The line core is sensitive
to magneto-acoustic shocks in and near magnetic concentrations, where
shocks occur deeper than elsewhere, and may provide evidence of heating
deep within magnetic concentrations.
Title: Fabry-Pérot Versus Slit Spectropolarimetry of Pores and
Active Network: Analysis of IBIS and Hinode Data
Authors: Judge, Philip G.; Tritschler, Alexandra; Uitenbroek, Han;
Reardon, Kevin; Cauzzi, Gianna; de Wijn, Alfred
Bibcode: 2010ApJ...710.1486J
Altcode: 2010arXiv1001.0561J
We discuss spectropolarimetric measurements of photospheric (Fe I
630.25 nm) and chromospheric (Ca II 854.21 nm) spectral lines in and
around small magnetic flux concentrations, including a pore. Our
long-term goal is to diagnose properties of the magnetic field
near the base of the corona. We compare ground-based two-dimensional
spectropolarimetric measurements with (almost) simultaneous space-based
slit spectropolarimetry. We address the question of noise and crosstalk
in the measurements and attempt to determine the suitability of Ca II
measurements with imaging spectropolarimeters for the determination
of chromospheric magnetic fields. The ground-based observations
were obtained 2008 May 20, with the Interferometric Bidimensional
Spectrometer (IBIS) in spectropolarimetric mode operated at the Dunn
Solar Telescope at Sunspot, NM. The space observations were obtained
with the Spectro-Polarimeter of the Solar Optical Telescope aboard the
Japanese Hinode satellite. The agreement between the near-simultaneous
co-spatial IBIS and Hinode Stokes-V profiles at 630.25 nm is
excellent, with V/I amplitudes compatible to within 1%. The IBIS QU
measurements are affected by residual crosstalk from V, arising from
calibration inaccuracies, not from any inherent limitation of imaging
spectroscopy. We use a Principal Component Analysis to quantify the
detected crosstalk. QU profiles with V crosstalk subtracted are in
good agreement with the Hinode measurements, but are noisier owing to
fewer collected photons. Chromospheric magnetic fields are notoriously
difficult to constrain by polarization of Ca II lines alone. However,
we demonstrate that high cadence, high angular resolution monochromatic
images of fibrils in Ca II and Hα, seen clearly in IBIS observations,
can be used to improve the magnetic field constraints, under conditions
of high electrical conductivity. Such work is possible only with time
series data sets from two-dimensional spectroscopic instruments such
as IBIS, under conditions of good seeing.
Title: Chromospheric Structure and Dynamics. From Old Wisdom to
New Insights
Authors: Tritschler, A.; Reardon, K.; Uitenbroek, H.
Bibcode: 2010MmSAI..81..533T
Altcode: 2010MmSAI..81..533R
No abstract at ADS
Title: Dual-Line Spectral Imaging of the Chromosphere
Authors: Cauzzi, G.; Reardon, K.; Rutten, R. J.; Tritschler, A.;
Uitenbroek, H.
Bibcode: 2010ASSP...19..513C
Altcode: 2010mcia.conf..513C
Hα filtergrams are notoriously difficult to interpret, "beautiful
to view but not fit for analysis." We try to remedy this by using
the IBIS bi-dimensional spectrometer at the Dunn Solar Telescope at
NSO/Sacramento Peak to compare the quiet-sun chromosphere observed in
Hα to what is observed simultaneously in Ca II 854.2 nm, sampling both
lines with high angular and spectral resolution and extended coverage
of space, time, and wavelength. Per (x, y, t) pixel we measured the
intensity and Dopplershift of the minimum of each line's profile at
that pixel, as well as the width of their inner chromospheric cores. A
paper submitted to A&A (December 2008) compares these measurements
in detail.
Title: Service-Mode Observations for Ground-Based Solar Physics
Authors: Reardon, K. P.; Rimmele, T.; Tritschler, A.; Cauzzi, G.;
Wöger, F.; Uitenbroek, H.; Tsuneta, S.; Berger, T.
Bibcode: 2009ASPC..415..332R
Altcode: 2009arXiv0909.1522R
There are significant advantages in combining Hinode observations
with ground-based instruments that can observe additional spectral
diagnostics at higher data rates and with greater flexibility. However,
ground-based observations, because of the random effects of weather
and seeing as well as the complexities data analysis due to changing
instrumental configurations, have traditionally been less efficient
than satellite observations in producing useful datasets. Future large
ground-based telescopes will need to find new ways to optimize both
their operational efficiency and scientific output. We have begun
experimenting with service-mode or queue-mode observations at the Dunn
Solar Telescope using the Interferometric Bidimensional Spectrometer
(IBIS) as part of joint Hinode campaigns. We describe our experiences
and the advantag es of such an observing mode for solar physics.
Title: Turbulence and Intermittency in the Solar Chromosphere
Authors: Lepreti, F.; Reardon, K. P.; Carbone, V.; Vecchio, A.
Bibcode: 2009AGUFMSH41B1649L
Altcode:
We study the line-of-sight velocity fluctuations measured simultaneously
in a photospheric (Fe I 709.0 nm) and a chromospheric line (Ca II 854.2
nm). The velocities were obtained from imaging spectral scans acquired
at high spatial resolution with the Interferometric BIdimensional
Spectrometer (IBIS) covering an 80" diameter field in the quiet Sun. We
find nearly power law tails above the acoustic cutoff frequency in
the chromospheric velocity power spectra. The probability density
functions (PDFs) of chromospheric velocity increments are non-Gaussian
and asymmetric. Intermittency is much larger in the network than in
fibril and internetwork regions. These results suggest that the small
scale velocity fluctuations in the solar chromosphere are the result
of a turbulent cascade generated from acoustic oscillations near the
cutoff frequency. The role of this turbulent cascade for chromospheric
heating is also discussed.
Title: The solar chromosphere at high resolution with
IBIS. IV. Dual-line evidence of heating in chromospheric network
Authors: Cauzzi, G.; Reardon, K.; Rutten, R. J.; Tritschler, A.;
Uitenbroek, H.
Bibcode: 2009A&A...503..577C
Altcode: 2009arXiv0906.2083C
The structure and energy balance of the solar chromosphere remain
poorly known. We used the imaging spectrometer IBIS at the Dunn Solar
Telescope to obtain fast-cadence, multi-wavelength profile sampling
of Hα and Ca ii 854.2 nm over a sizable two-dimensional field of view
encompassing quiet-Sun network. We provide a first inventory of how the
quiet chromosphere appears in these two lines by comparing basic profile
measurements in the form of image displays, temporal-average displays,
time slices, and pixel-by-pixel correlations. We find that the two lines
can be markedly dissimilar in their rendering of the chromosphere,
but that, nevertheless, both show evidence of chromospheric heating,
particularly in and around network: Hα in its core width and Ca ii
854.2 nm in its brightness. We discuss venues for improved modeling.
Title: Spectropolarimetry of Ca II 8542: Probing the Chromospheric
Magnetic Field
Authors: Kleint, L.; Reardon, K.; Stenflo, J. O.; Uitenbroek, H.;
Tritschler, A.
Bibcode: 2009ASPC..405..247K
Altcode:
We present spectropolarimetric observations of the chromospheric Ca II
8542 and photospheric Fe I 6302 lines obtained with the Interferometric
Bidimensional Spectrometer (IBIS) at the Dunn Solar Telescope. The
high spatial resolution over a large field of view (FOV) allows us to
connect the observed profiles to the overall topology of the target
region. After suitable calibrations we can extract Stokes profiles
for each point in the FOV. The Stokes V profiles observed in the Ca II
line show a large variety of shapes, indicating widely varying vertical
behavior of the field strength, velocity, and temperature. We examine
the center-of-gravity method for determining a representative field
strength from the observed profiles and use it to directly compare
photospheric and chromospheric magnetic fields.
Title: The solar chromosphere at high resolution with
IBIS. III. Comparison of Ca II K and Ca II 854.2 nm imaging
Authors: Reardon, K. P.; Uitenbroek, H.; Cauzzi, G.
Bibcode: 2009A&A...500.1239R
Altcode: 2008arXiv0810.5260R
Aims: Filtergrams obtained in Ca II H, Ca II K, and Hα are often
employed as diagnostics of the solar chromosphere. The vastly disparate
appearance between the typical filtergrams in these different lines
calls into question the nature of what is actually being observed. We
investigate the lack of obvious structures of magnetic origin such as
fibrils and mottles in on-disk Ca II H and K images.
Methods: We
directly compare a temporal sequence of classical Ca II K filtergrams
with a co-spatial and co-temporal sequence of spectrally resolved
Ca II 854.2 images obtained with the Interferometric Bidimensional
Spectrometer (IBIS), considering the effect of both the spectral and
spatial smearing. We analyze the temporal behavior of the two series
by means of Fourier analysis.
Results: The lack of fine magnetic
structuring in Ca II K filtergrams, even with the narrowest available
filters, is due to observational effects, primarily contributions from
the bright, photospheric wings of the line that swamp the small and
dark chromospheric structures. Signatures of fibrils remain, however,
in the temporal evolution of the filtergrams, in particular with
the evidence of magnetic shadows around the network elements. The
Ca II K filtergrams do not appear, however, to properly reflect the
high-frequency behavior of the chromosphere. Using the same analysis,
we find no significant chromospheric signature in the Hinode/SOT Ca II
H quiet-Sun filtergrams.
Conclusions: The picture provided by Hα
and Ca II 854.2, which show significant portions of the chromosphere
dominated by magnetic structuring, appears to reflect the true and
essential nature of the solar chromosphere. Data that do not resolve
this aspect, whether spatially or spectrally, may misrepresent the
behavior the chromosphere.
Title: The Virtual Solar Observatory: Where Do We Go from Here?
Authors: Gurman, Joseph B.; Bogart, R.; Spencer, J.; Hill, F.; Suarez
Sola, I.; Reardon, K.; Hourcle, J.; Hughitt, K.; Martens, P.; Davey, A.
Bibcode: 2009SPD....40.1508G
Altcode:
The Virtual Solar Observatory (VSO) continues to add features in an
effort to broaden the ways in which it can be used to aid research. We
describe and demonstrate plans for SDO data access (see also the poster
Suarez-Sola et al.), multiple catalog access (Hourclé et al.), and
new capabilities of the IDL VSO_SEARCH function, as well as describing
future capabilities in development and under consideration. Since
the VSO is funded by the Solar Data Analysis Center (SDAC), which will
be undergoing a NASA Senior Review in July, we solicit community input
to help us prioritize this new work: what should we do with the limited
resources available?
Title: The Virtual Solar Observatory—A Resource for International
Heliophysics Research
Authors: Hill, Frank; Martens, Piet; Yoshimura, Keji; Gurman, Joseph;
Hourclé, Joseph; Dimitoglou, George; Suárez-Solá, Igor; Wampler,
Steve; Reardon, Kevin; Davey, Alisdair; Bogart, Richard S.; Tian,
Karen Q.
Bibcode: 2009EM&P..104..315H
Altcode: 2008EM&P..tmp...47H
The Virtual Solar Observatory (VSO) has been developed to allow
researchers, educators, and the general public to access data
and images from the major sources of on-line solar data. The VSO
substantially reduces the effort required to locate disparate data
sets, and removes the need for the user to locate the data and
learn multiple interfaces. The VSO provides a single interface to
about 60 geographically distributed data sets including space- and
ground-based sources. These data sets incorporate several physical
variables including magnetic field, intensity, Doppler velocity, etc.,
and all wavelengths from X-ray to radio. All layers of the sun, from
the interior to the corona, are included. In this paper we describe
the system and present the interface that the user will encounter. We
also discuss future enhancements planned for the system.
Title: The solar chromosphere at high resolution with
IBIS. II. Acoustic shocks in the quiet internetwork and the role of
magnetic fields
Authors: Vecchio, A.; Cauzzi, G.; Reardon, K. P.
Bibcode: 2009A&A...494..269V
Altcode: 2008arXiv0807.4966V
Context: The exact nature of the quiet solar chromosphere and
especially its temporal variation, are still subjects of intense
debate. One of the contentious issues is the possible role of the
magnetic field in structuring the quieter solar regions.
Aims:
We characterize the dynamics of the quiet inter-network chromosphere
by studying the occurrence of acoustic shocks and their relation with
the concomitant photospheric structure and dynamics, including small
scale magnetic structures.
Methods: We analyze a comprehensive
data set that includes high-resolution chromospheric (Ca ii 854.2
nm) and photospheric (Fe i 709.0 nm) spectra obtained with the IBIS
imaging spectrometer in two quiet-Sun regions. This is complemented by
high-resolution sequences of MDI magnetograms of the same targets. From
the chromospheric spectra we identify the spatio-temporal occurrence of
the acoustic shocks. We compare it with the photospheric dynamics by
means of both Fourier and wavelet analysis and study the influence of
magnetic structures on the phenomenon.
Results: Mid-chromospheric
shocks occur within the general chromospheric dynamics pattern of
acoustic waves propagating from the photosphere. In particular, they
appear as a response to underlying powerful photospheric motions
at periodicities nearing the acoustic cut-off, consistent with 1-D
hydrodynamical modeling. However, their spatial distribution within
the supergranular cells is highly dependent on the local magnetic
topology, both at the network and internetwork scale. We find that
large portions of the internetwork regions undergo very few shocks,
since they are “shadowed” by the horizontal component of the
magnetic field. The latter is betrayed by the presence of chromospheric
fibrils, observed in the core of the Ca ii line as slanted structures
with distinct dynamical properties. The shadow mechanism also appears
to operate on the very small scales of inter-network magnetic elements,
and provides for a very pervasive influence of the magnetic field even
in the quietest region analyzed.
Conclusions: The magnetic field
might play a larger role in structuring the quiet solar chromosphere
than normally assumed. The presence of fibrils highlights a clear
disconnection between the photospheric dynamics and the response of
the geometrically overlaying chromosphere. As these results hold for
a mid-chromospheric indicator such as the Ca ii 854.2 line, it is
expected that diagnostics formed in higher layers, such as UV lines
and continua, will be affected to a greater extent by the presence
of magnetic fields, even in quiet regions. This is relevant for the
chromospheric models that make use of such diagnostics.
Title: The Solar Chromosphere: Old Challenges, New Frontiers
Authors: Ayres, T.; Uitenbroek, H.; Cauzzi, G.; Reardon, K.; Berger,
T.; Schrijver, C.; de Pontieu, B.; Judge, P.; McIntosh, S.; White,
S.; Solanki, S.
Bibcode: 2009astro2010S...9A
Altcode:
No abstract at ADS
Title: Evidence for a Current Sheet above a Sunspot Umbra
Authors: Tritschler, A.; Uitenbroek, H.; Reardon, K.
Bibcode: 2008ApJ...686L..45T
Altcode:
We present observational evidence for the existence of a current
sheet in the chromosphere above a sunspot umbra based on high angular
resolution two-dimensional spectroscopic observations in the Ca II
854.21 nm line. In the core of this line we observe a very stable bright
ribbon-like structure separating magnetic field configurations that
connect to different parts of the active region. We make plausible
that the structure is a string of sheets carrying vertical currents
that result from dissipation when the different parts of the active
region are moved around in the photosphere. To our knowledge this is
the first direct observation of the heating caused by the dissipation
in such a current sheet in the chromosphere.
Title: Imaging Spectropolarimetry of the Photosphere and Chromosphere
with IBIS
Authors: Reardon, K.; Tritschler, A.; Uitenbroek, H.; et al.
Bibcode: 2008ESPM...12.2.31R
Altcode:
We present recent results based on high-resolution spectropolarimetry
using IBIS, a dual Fabry-Perot imaging spectrometer. We describe
the characteristics of the instrument and its capability to measure
the full Stokes vector in a range of photospheric and chromospheric
spectral lines. Since late 2006 IBIS has been regularly used in
spectropolarimetric mode and observations have included solar pores,
quiet sun network and internetwork areas, and the disk passage of active
regions NOAA 10941 and 10940. Measurements are primarily performed in
the Fe I 630.2 and the Ca II 854.2 nm lines to provide information on
both photospheric to chromospheric heights. We present results on the
highly dynamical nature of both the vertical and horizontal components
of quiet Sun magnetic fields. We also show the fine structure and
height variation of the magnetic field in a large sunspot.
Title: Speckle interferometry with adaptive optics corrected
solar data
Authors: Wöger, F.; von der Lühe, O.; Reardon, K.
Bibcode: 2008A&A...488..375W
Altcode:
Context: Adaptive optics systems are used on several advanced solar
telescopes to enhance the spatial resolution of the recorded data. In
all cases, the correction remains only partial, requiring post-facto
image reconstruction techniques such as speckle interferometry
to achieve consistent, near-diffraction limited resolution.
Aims: This study investigates the reconstruction properties of
the Kiepenheuer-Institut Speckle Interferometry Package (KISIP)
code, with focus on its phase reconstruction capabilities and
photometric accuracy. In addition, we analyze its suitability for
real-time reconstruction.
Methods: We evaluate the KISIP
program with respect to its scalability and the convergence of
the implemented algorithms with dependence on several parameters,
such as atmospheric conditions. To test the photometric accuracy of
the final reconstruction, comparisons are made between simultaneous
observations of the Sun using the ground-based Dunn Solar Telescope and
the space-based Hinode/SOT telescope.
Results: The analysis shows
that near real-time image reconstruction with high photometric accuracy
of ground-based solar observations is possible, even for observations in
which an adaptive optics system was utilized to obtain the speckle data.
Title: Acoustic Shocks in the Quiet Internetwork and the Role of
Magnetic Fields
Authors: Cauzzi, G.; Vecchio, A.; Reardon, K.
Bibcode: 2008ESPM...12.2.37C
Altcode:
By using imaging spectroscopy in the CaII 854.2 nm line obtained with
IBIS over several quiet Sun regions, we present compelling evidence of
acoustic shocks occurring in the quiet chromosphere at the dominant
3-minute periodicity. The shocks present many of the characteristics
prescribed in 1-D hydrodynamics models, including a mostly vertical
propagation of the disturbance from regions of enhanced photospheric
velocity at periodicities close to the acoustic cut-off. Our most
interesting result, however, is the large influence that magnetic
structures exert on the development of chromospheric shocks. In
particular, shocks are essentially absent from extended regions
around magnetic network elements, creating the so-called "magnetic
shadows". These areas coincide with the presence of chromospheric
fibrils rooted in the network itself, that apparently absorb or
otherwise modify the upward propagating acoustic waves, inhibiting
the formation of shocks. Intriguingly, we also find a clear
reduction in the number of shocks observed in quiet internetwork areas
whenever small magnetic structures are seen in MDI HR maps. This is
true even when strong photospheric motions at the relevant periods
are present. This might imply the need to reevaluate the acoustic
contribution to the observed chromospheric "basal" flux.
Title: Chromospheric Counterparts of UV Explosive Events
Authors: Reardon, K.; Cauzzi, G.; Teriaca, L.; Pitterle, M.; Curdt, W.
Bibcode: 2008ESPM...12.2.17R
Altcode:
We present a study of a unique, multi-wavelength dataset of a quiet
sun region with the primary goal of studying explosive events at
chromospheric and transition region heights. Several hypotheses
have been made about the nature of the explosive events, however the
underlying mechanisms remain elusive due to their small spatial and
temporal scales. Several theoretical models predict an important
role for the chromosphere in the triggering of these events. To shed light on this issue, we have obtained a comprehensive
set of simultaneous high spatial, spectral, and temporal resolution
observations on April 18, 2007, combining both ground- and space-based
observatories. Most importantly, we carried out coordinated observations
with SUMER in the transition region Si IV 140.2 nm line together
with high-cadence IBIS imaging spectroscopy of the chromospheric CaII
854.2 nm line. This allows us to examine the chromospheric dynamics
and acoustic shocks that underlie the transition region events. We
also use SOT/NFI magnetograms to examine the relation of the explosive
events to the changes in the magnetic topology. The combined dataset
also includes Hinode/EIS rasters and Hinode/XRT images that provide
information on the higher-temperature coronal response.
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: Physical Properties of Chromospheric Structures in H-alpha
and and CaII 854.2 nm
Authors: Bostanci, Z. F.; Rutten, R., R. Jtenbroek, H.; Reardon, K.;
Cauzzi, G.
Bibcode: 2008ESPM...12.2.45B
Altcode:
Comprehensive studies of chromospheric structures are the key to
understanding their dynamics in different solar regimes and their
contribution in heating of the solar atmosphere. High spatial and
spectral resolution observations of a quiet chromospheric region
were obtained with the Interferometric BIdimensional Spectrometer
(IBIS) installed at the Dunn Solar Telescope (DST) of the National
Solar Observatory (NSO) on Sacramento Peak, USA. Chromospheric fibrils
that were observed simultaneously in the Balmer H? and CaII 854.2 nm
line are analysed using the cloud model technique to derive numerical
values for the standard cloud model parameters; optical thickness,
source function, Dopplerwidth and Dopplershift for the two lines,
enabling detailed comparison between these.
Title: Evidence of Shock-driven Turbulence in the Solar Chromosphere
Authors: Reardon, K. P.; Lepreti, F.; Carbone, V.; Vecchio, A.
Bibcode: 2008ApJ...683L.207R
Altcode: 2008arXiv0809.4243R
We study the acoustic properties of the solar chromosphere in the
high-frequency regime using a time sequence of velocity measurements
in the chromospheric Ca II 854.2 nm line taken with the Interferometric
Bidimensional Spectrometer (IBIS). We concentrate on quiet-Sun behavior,
apply Fourier analysis, and characterize the observations in terms of
the probability density functions (PDFs) of velocity increments. We
confirm the presence of significant oscillatory fluctuation power above
the cutoff frequency and find that it obeys a power-law distribution
with frequency up to our 25 mHz Nyquist limit. The chromospheric PDFs
are non-Gaussian and asymmetric, and they differ among the network,
fibril, and internetwork regions. This suggests that the chromospheric
high-frequency power is not simply the result of short-period waves
propagating upward from the photosphere but rather is the signature of
turbulence generated within the chromosphere from shock oscillations
near the cutoff frequency. The presence of this pervasive and broad
spectrum of motions in the chromosphere is likely to have implications
for the excitation of coronal loop oscillations.
Title: The Energy Flux of Internal Gravity Waves in the Lower Solar
Atmosphere
Authors: Straus, Thomas; Fleck, Bernhard; Jefferies, Stuart M.;
Cauzzi, Gianna; McIntosh, Scott W.; Reardon, Kevin; Severino, Giuseppe;
Steffen, Matthias
Bibcode: 2008ApJ...681L.125S
Altcode:
Stably stratified fluids, such as stellar and planetary atmospheres,
can support and propagate gravity waves. On Earth these waves,
which can transport energy and momentum over large distances and can
trigger convection, contribute to the formation of our weather and
global climate. Gravity waves also play a pivotal role in planetary
sciences and modern stellar physics. They have also been proposed
as an agent for the heating of stellar atmospheres and coronae, the
exact mechanism behind which is one of the outstanding puzzles in solar
and stellar physics. Using a combination of high-quality observations
and 3D numerical simulations we have the first unambiguous detection
of propagating gravity waves in the Sun's (and hence a stellar)
atmosphere. Moreover, we are able to determine the height dependence of
their energy flux and find that at the base of the Sun's chromosphere it
is around 5 kW m-2. This amount of energy is comparable to
the radiative losses of the entire chromosphere and points to internal
gravity waves as a key mediator of energy into the solar atmosphere.
Title: Search for High Velocities in the Disk Counterpart of Type
II Spicules
Authors: Langangen, Ø.; De Pontieu, B.; Carlsson, M.; Hansteen,
V. H.; Cauzzi, G.; Reardon, K.
Bibcode: 2008ApJ...679L.167L
Altcode: 2008arXiv0804.3256L
Recently, De Pontieu and coworkers discovered a class of spicules
that evolve more rapidly than previously known spicules, with rapid
apparent motions of 50-150 km s-1, thickness of a few 100
km, and lifetimes of order 10-60 s. These so-called type II spicules
have been difficult to study because of limited spatiotemporal and
thermal resolution. Here we use the IBIS instrument to search for the
high velocities in the disk counterpart of type II spicules. We have
detected rapidly evolving events, with lifetimes that are less than a
minute and often equal to the cadence of the instrument (19 s). These
events are characterized by a Doppler shift that only appears in the
blue wing of the Ca II IR line. Furthermore, the spatial extent,
lifetime, and location near network all suggest a link to type II
spicules. However, the magnitude of the measured Doppler velocity is
significantly lower than the apparent motions seen at the limb. We
use Monte Carlo simulations to show that this discrepancy can be
explained by a forward model in which the visibility on the disk of
the high-velocity flows in these events is limited by a combination
of line-of-sight projection and reduced opacity in upward propelled
plasma, especially in reconnection driven jets that are powered by a
roughly constant energy supply.
Title: Solar Chromospheric Dynamics: Onwards and Upwards
Authors: Cauzzi, G.; Reardon, K.; Rimmele, T.; Rutten, R.; Tritschler,
A.; Uitenbroek, H.; Woeger, F.
Bibcode: 2008AGUSMSP41B..03C
Altcode:
We present a study of chromospheric dynamics and its relation with the
driving photospheric magneto-convection in a variety of solar targets,
from quiet Sun to more active regions. To this end high resolution
observations were obtained in CaII 854.2 nm, Hα, and photospheric
FeI lines with the Interferometric BIdimensional Spectrometer (IBIS)
installed at the Dunn Solar Telescope of the NSO. The availability of
full spectroscopic information on extended fields of view allows us
to derive a comprehensive view of the intrinsically 3-D chromospheric
scene. A coherent picture is emerging that involves the propagation
and dissipation of photospheric acoustic waves into the chromospheric
layers, but selected and guided by the local and highly variable
magnetic topology. In particular, ubiquitous fibrilar structures,
apparently originating from even the smallest magnetic elements,
appear an integral part of the dynamic chromosphere.
Title: WHI Targeted Campaigns on Coronal Holes and Quiet Sun: High
Resolution Observations of the Lower Atmosphere With IBIS
Authors: Cauzzi, G.; Reardon, K. P.; Rimmele, T.; Tritschler, A.;
Uitebroek, H.; Woeger, F.; Deforest, C.; McIntosh, S.
Bibcode: 2008AGUSMSH51A..02C
Altcode:
The Interferometric BIdimensional Spectrometer (IBIS) is a dual
Fabry-Perot instrument installed at the Dunn Solar Telescope that allows
two-dimensional spectroscopic observations in a variety of spectral
lines. The IBIS/DST will participate in the WHI targeted campaigns
on coronal holes (April 3-9) and quiet Sun dynamics (April 10-16)
performing simultaneous high-resolution observations of the dynamics of
the photosphere and chromosphere in the coordinated targets. The aim is
to obtain insights on the role of the lower atmosphere's dynamics and
energetics into the structuring of the coronal plasma and, possibly,
into the origin of the solar wind. In this paper we will present the
observations obtained as well as first results, and attempt to relate
them with recent work performed on quiet Sun chromospheric dynamics.
Title: Evidence of Shock-Driven Turbulence in the Solar Chromosphere
Authors: Reardon, K.; Lepreti, F.; Carbone, V.; Vecchio, A.
Bibcode: 2008AGUSMSP21B..03R
Altcode:
We present observations of photospheric and chromospheric velocities
at high spatial resolution using the Interferometric Bidimensional
Spectrometer (IBIS). We study an area of quiet Sun and apply Fourier
analysis to the velocity time series. We confirm the presence of
significant power in the chromosphere above the cutoff frequency
and find that it obeys power-law distribution with frequency up to
our 25 mHz Nyquist limit. We further characterize the observations
in terms of Probability Density Functions (PDFs) and find that the
chromospheric PDFs are non-Gaussian and asymmetric. This suggests
that the chromospheric high-frequency power is probably not made up
of short-period waves propagating upward from the photosphere, but
rather is the signature of turbulence generated within the chromosphere
from shock oscillations near the cutoff frequency. The presence of
this pervasive and broad spectrum of motions in the chromosphere is
important for atmospheric modeling and is likely to have implications
for the excitation of coronal loop oscillations.
Title: Searching the X-ray Sun For Solar Axions
Authors: Hudson, Hugh S.; Acton, L. W.; DeLuca, E. E.; Hannah, I. G.;
Hurford, G. J.; Lin, R. P.; Reardon, K. P.; van Bibber, K.
Bibcode: 2008AAS...212.0402H
Altcode: 2008BAAS...40..193H
The axion is a hypothetical weakly-interacting elementary particle. The
solar core may produce a copious axion flux via the Primakoff
effect. This same process can also convert a tiny fraction of the
axions back into photons via interaction with the magnetic field
threading the solar atmosphere. The spectral signature of the emitted
X-rays is determined mainly by the temperature of the solar core, and
the spatial distribution also depends strongly on the solar magnetic
field in the back-conversion process. The X-ray intensity thus varies as
Gaγγ(∫BperpdL)2,
where Bperp is the perpendicular component of the
chromospheric and coronal magnetic field in the appropriate zone
for interaction and photon escape, and Gaγγ
is the (unknown) coupling constant, dependent on the (unknown) mass
of the axion. We describe observational tests suitable for solar
X-ray imagers and discuss projects now under way with Yohkoh/SXT,
RHESSI, and Hinode/XRT. The successful detection of axions would have
implications for basic physics and for cosmological dark matter. It
would also help us to characterize the ill-understood extension of the
solar magnetic field into the chromosphere and corona. We specifically
focus on applying the existing understanding of solar (and stellar)
magnetism to this problem.
Title: Characterization of Fabry-Perot interferometers and
multi-etalon transmission profiles. The IBIS instrumental profile
Authors: Reardon, K. P.; Cavallini, F.
Bibcode: 2008A&A...481..897R
Altcode:
Aims: Properly characterizing Fabry-Perot interferometers (FPI) is
essential for determining their effective properties and evaluating
the performance of the astronomical instruments in which they are
employed. Furthermore, in two-dimensional spectrographs where multiple
FPI are used in series, the actual distribution of plate separation
errors will be crucial for determining the resulting transmission
profiles. We describe techniques that address these issues utilizing
the FPI of IBIS, a solar bidimensional spectrometer installed at the
Dunn Solar Telescope.
Methods: A frequency-stabilized He-Ne
laser was used in three different optical layouts to measure the
spatially-resolved transmission of the FPI. Analyzing the shape and
wavelength shift of the observed profiles allows the characteristics of
the cavity errors and the interferometer coating to be determined.
Results: We have measured the spatial distribution of the large-scale
plate defects, which shows a steep radial trend, as well as the
magnitude of the small-scale microroughness. We also extracted
the effective reflectivity and absorption of the coating at the
laser line wavelength for both interferometers.
Conclusions:
These techniques, which are generally applicable to any Fabry-Perot
interferometer, provide the necessary information for calculating
the overall instrumental profile for any illuminated area of the
interferometer plates. Accurate knowledge of the spectral transmission
profile is important, in particular when using inversion techniques
or in comparing observations with simulated data.
Title: The solar chromosphere at high resolution with IBIS. I. New
insights from the Ca II 854.2 nm line
Authors: Cauzzi, G.; Reardon, K. P.; Uitenbroek, H.; Cavallini, F.;
Falchi, A.; Falciani, R.; Janssen, K.; Rimmele, T.; Vecchio, A.;
Wöger, F.
Bibcode: 2008A&A...480..515C
Altcode: 2007arXiv0709.2417C
Context: The chromosphere remains a poorly understood part of the solar
atmosphere, as current modeling and observing capabilities are still
ill-suited to investigating its fully 3-dimensional nature in depth. In
particular, chromospheric observations that can preserve high spatial
and temporal resolution while providing spectral information over
extended fields of view are still very scarce.
Aims: In this
paper, we seek to establish the suitability of imaging spectroscopy
performed in the Ca II 854.2 nm line as a means of investigating
the solar chromosphere at high resolution.
Methods: We utilize
monochromatic images obtained with the Interferometric BIdimensional
Spectrometer (IBIS) at multiple wavelengths within the Ca II 854.2 nm
line and over several quiet areas. We analyze both the morphological
properties derived from narrow-band monochromatic images and the
average spectral properties of distinct solar features such as network
points, internetwork areas, and fibrils.
Results: The spectral
properties derived over quiet-Sun targets are in full agreement with
earlier results obtained with fixed-slit spectrographic observations,
highlighting the reliability of the spectral information obtained
with IBIS. Furthermore, the very narrowband IBIS imaging reveals very
clearly the dual nature of the Ca II 854.2 nm line. Its outer wings
gradually sample the solar photosphere, while the core is a purely
chromospheric indicator. The latter displays a wealth of fine structures
including bright points akin to the Ca II H{2V} and K{2V} grains, and
as fibrils originating from even the smallest magnetic elements. The
fibrils occupy a large fraction of the observed field of view, even
in the quiet regions, and clearly outline atmospheric volumes with
different dynamical properties, strongly dependent on the local magnetic
topology. This highlights how 1D models stratified along the vertical
direction can provide only a very limited representation of the actual
chromospheric physics.
Conclusions: Imaging spectroscopy in the
Ca II 854.2 nm line currently represents one of the best observational
tools for investigating the highly structured and highly dynamical
chromospheric environment. A high-performance instrument such as IBIS
is crucial in achieving the necessary spectral purity and stability,
spatial resolution, and temporal cadence. Two movies are only
available in electronic form at http://www.aanda.org
Title: Two-dimensional Spectropolarimetry At The Dunn Solar Tower
Authors: Uitenbroek, Han; Tritshler, A.; Reardon, K.; Kleint, L.
Bibcode: 2007AAS...210.2605U
Altcode: 2007BAAS...39..324U
Measurement of the solar magnetic field within individual atmospheric
structures is a desirable, but persistently challenging goal, in
particular in chromospheric layers. Successful measurements over
different heights would provide an important contribution to our
understanding of the solar atmosphere and would provide valuable
input for theoretical modeling. We provide a short description of the
capabilities of the Interferometric BIdimensional Spectrometer (IBIS),
which has recently been upgraded to full Stokes capabilities. IBIS
is installed at the Dunn Solar Tower (DST) at the Sacramento Peak
observatory operated by NSO. Using IBIS we achieve high spatial
resolution over a large field of view in both the photosphere and
the chromosphere, which allows us to connect the observed profiles
to the overall topology of the target region. After performing
suitable calibrations for the telescope and instrument polarization
properties, we can extract Stokes profiles for each point in the
field of view. Stokes V profiles observed in the Ca II 854.2 nm line
show a large variety of forms, indicating widely varying vertical
behavior of the field strength, velocity, and temperature. We examine
the center-of-gravity method for determining a representative field
strength from the observed profiles looking at observations and
comparing with simulated profiles.
Title: Comparison of spatially and spectrally resolved solar data
with numerical simulations
Authors: Cauzzi, G.; Asensio Ramos, A.; Reardon, K. P.; Janssen, K.
Bibcode: 2007IAUS..239..138C
Altcode:
No abstract at ADS
Title: Acoustic Shocks in the Quiet Solar Chromosphere
Authors: Cauzzi, G.; Reardon, K. P.; Vecchio, A.; Janssen, K.;
Rimmele, T.
Bibcode: 2007ASPC..368..127C
Altcode:
We exploit the two-dimensional spectroscopic capabilities of the
Interferometric BIdimensional Spectrometer (IBIS) to study the
chromospheric Ca II 854.2 nm line and its temporal evolution in a quiet
region at the center of the solar disk. The Ca II 854.2 profiles in the
internetwork portion of the field of view clearly indicate the presence
of hydrodynamic shocks, occurring at frequencies above the acoustic
cut-off. The location and strength of such shocks perfectly map
the areas where large velocity power is found at frequencies of 5.5-8
mHz in a standard Fourier analysis. The shocks locations evidence a
sharp partition of the quiet area in regions of very distinct dynamical
behavior, highlighting the role of the local magnetic topology in
structuring the lower chromosphere. The portions of the field of view
where the photospheric field is very weak, and that are presumably
connected to distant magnetic structures (or open to the interplanetary
field), are the site of frequent shock occurrence. On the contrary, in
regions neighboring the magnetic network and harboring a more horizontal
configuration of the chromospheric magnetic field, shocks are heavily
suppressed, even if the photospheric field is essentially absent in
these areas as well. These latter regions, with much reduced velocity
power at frequencies of 5.5-8 mHz \citep[the ``magnetic shadows'' first
described in][]{gc-judge_01}, are spatially coincident with fibrilar
structures visible in the Ca II 854.2 line core intensity maps. We
finally argue that areas within and immediately surrounding the magnetic
network also display evidence of chromospheric shocks, but occurring at
periodicities of 4-6 minutes. Such slow shocks are stronger than those
occurring in field-free areas, as evidenced by the strong emission
in the inner blue-wing of the line. This is in agreement with recent
results claiming that magneto-acoustic shocks can develop in inclined
magnetic structures, acting as `portals' through which the powerful
low-frequency photospheric oscillations can leak into the chromosphere.
Title: Comparison of Ca II K and Ca II 8542 Å Images
Authors: Reardon, K. P.; Cauzzi, G.; Rimmele, T.
Bibcode: 2007ASPC..368..151R
Altcode:
We compare a time sequence of filtergrams obtained in the Ca II K line
with a series of spectrally resolved images obtained simultaneously
with the IBIS instrument in the Ca II 8542 Å line. Using the
narrowband IBIS images and a synthetic filter profile, we construct
simulated 8542 filtergrams that mimic the observed K2V
filtergrams. We observe that these filtergrams appear to contain
elements corresponding to both photospheric and chromospheric
structures. Intermediate scale patterns seen in the filtergrams may
simply be the result of the combination of a variety of structures
from different atmospheric levels. We analyze the Fourier power
spectra of the filtergrams and note that at frequencies well above
the acoustic cut-off value the observed power in the K2V
filtergrams seems to be predominantly photospheric in origin. The use
of Ca II H and K filtergrams to study the chromospheric behavior thus
may be inherently problematic. Narrowband images in the Ca II 8542 Å
line might provide a better source of information about chromospheric
behavior with little loss in spatial or temporal resolution.
Title: Photon Spectroscopy with Imaging X-Ray Instruments
Authors: Labonte, B. J.; Reardon, K. P.
Bibcode: 2007SoPh..240..387L
Altcode:
Individual X-ray photons in the keV energy range produce hundreds of
photoelectrons in a single pixel of a CCD array detector. The number
of photoelectrons produced is a linear function of the photon energy,
allowing the measurement of spectral information with an imaging
detector system. Most solar X-ray telescopes, such as Yohkoh/SXT and
Hinode/XRT, use CCD detectors in an integrating mode and are designed to
make temperature estimates from multiband filter photometry. We show how
such instruments can be used in a new way to perform a limited type of
this photon spectroscopy. By measuring the variance in intensity of a
series of repeated images through a single filter of an X-ray source,
the mean energy per detected photon can be determined. This energy
is related to the underlying coronal spectrum, and hence it can be
used to deduce the mean plasma temperature. We apply this technique to
data from the Yohkoh Soft X-Ray Telescope and compare the temperatures
obtained with this technique with the temperatures derived using the
standard filter ratio method for a postflare loop system. Given the
large dynamic range of the soft X-ray flux observed from the Sun,
we describe the requirements for a future instrument that would be
better suited to performing photon spectroscopy.
Title: Solar atmospheric oscillations and the chromospheric magnetic
topology
Authors: Vecchio, A.; Cauzzi, G.; Reardon, K. P.; Janssen, K.;
Rimmele, T.
Bibcode: 2007A&A...461L...1V
Altcode: 2006astro.ph.11206V
Aims:We investigate the oscillatory properties of the quiet solar
chromosphere in relation to the underlying photosphere, with particular
regard to the effects of the magnetic topology.
Methods: For the
first time we perform a Fourier analysis on a sequence of line-of-sight
velocities measured simultaneously in a photospheric (Fe I 709.0 nm)
and a chromospheric line (Ca II 854.2 nm). The velocities were obtained
from full spectroscopic data acquired at high spatial resolution with
the Interferometric BIdimensional Spectrometer (IBIS). The field of
view encompasses a full supergranular cell, allowing us to discriminate
between areas with different magnetic characteristics.
Results: We
show that waves with frequencies above the acoustic cut-off propagate
from the photosphere to upper layers only in restricted areas of
the quiet Sun. A large fraction of the quiet chromosphere is in fact
occupied by “magnetic shadows”, surrounding network regions, that
we identify as originating from fibril-like structures observed in
the core intensity of the Ca II line. We show that a large fraction
of the chromospheric acoustic power at frequencies below the acoustic
cut-off, residing in the proximity of the magnetic network elements,
directly propagates from the underlying photosphere. This supports
recent results arguing that network magnetic elements can channel
low-frequency photospheric oscillations into the chromosphere, thus
providing a way to input mechanical energy in the upper layers.
Title: High-resolution IBIS Observations and Comparison with 3D
Simulations
Authors: Cauzzi, G.; Asensio Ramos, A.; Reardon, K.; Janssen, K.
Bibcode: 2006ASPC..354...26C
Altcode:
We present first comparisons between high resolution observations of
the quiet photosphere, obtained with the Interferometric BIdimensional
Spectrometer (IBIS) in the non-magnetic Fe I 7090.4 Å spectral
line, and the synthetic spectrum calculated for a 3D snapshot of a
radiation-hydrodynamical simulation of the solar atmosphere. Together
with morphological comparisons between the synthetic images and the
observed ones at different wavelengths, we have carried out comparisons
between several observables. The simulations reproduce quite well
many of the observational properties of the high resolution IBIS data,
apart from the velocity distribution, that contains values quite larger
than observed.
Title: 3-D Structure of Sunspots Using Imaging Spectroscopy
Authors: Balasubramaniam, K. S.; Gary, G. A.; Reardon, K.
Bibcode: 2006ASPC..354..237B
Altcode:
We use the Interferometric BIdimensional Spectrometer (IBIS) of the
INAF/Arcetri Astrophysical Observatory and installed at the National
Solar Observatory (NSO) Dunn Solar Telescope, to understand the
structure of sunspots. Using the spectral lines Fe I 6301.5 Å, Fe II
7224.4 Å, and Ca II 8542.6 Å, we examine the spectroscopic variation
of sunspot penumbral and umbral structures at the heights of formation
of these lines. These high resolution observations were acquired on
2004 July 30 -- 31, of active region NOAA 10654, using the high order
NSO adaptive optics system. We map the spatio-temporal variation of
Doppler signatures in these spectral lines, from the photosphere to
the chromosphere. From a 70-minute temporal average of individual
32-second cadence Doppler observations we find that the averaged
velocities decrease with height. They are about 3.5 times larger in the
deeper photosphere (Fe II 7224.4 Å; height-of-formation ≈ 50 km)
than in the upper photosphere Fe I 6301.5 Å; height-of-formation
≈ 350 km), There is a remarkable coherence of Doppler signals
over the height difference of 300 km. From a high-speed animation
of the Doppler sequence we find evidence for what appears to be
ejection of high speed gas concentrations from edges of penumbral
filaments into the surrounding granular photosphere. The Evershed
flow persists a few arcseconds beyond the traditionally demarcated
penumbra-granulation boundary. We present these and other results and
discuss the implications of these measurements for sunspot models.
Title: The Effects of Atmospheric Dispersion on High-Resolution
Solar Spectroscopy
Authors: Reardon, Kevin P.
Bibcode: 2006SoPh..239..503R
Altcode: 2007astro.ph..1303R; 2006SoPh..tmp...89R
We investigate the effects of atmospheric dispersion on observations
of the Sun at the ever-higher spatial resolutions afforded by increased
apertures and improved techniques. The problems induced by atmospheric
refraction are particularly significant for solar physics because
the Sun is often best observed at low elevations, and the effect of
the image displacement is not merely a loss of efficiency, but the
mixing of information originating from different points on the solar
surface. We calculate the magnitude of the atmospheric dispersion
for the Sun during the year and examine the problems produced by this
dispersion in both spectrographic and filter observations. We describe
an observing technique for scanning spectrograph observations that
minimizes the effects of the atmospheric dispersion while maintaining
a regular scanning geometry. Such an approach could be useful for
the new class of high-resolution solar spectrographs, such as SPINOR,
POLIS, TRIPPEL, and ViSP.
Title: The Interferometric Bidimensional Spectrometer (IBIS)
Authors: Cauzzi, Gianna; Cavallini, F.; Reardon, K.; Berrilli, F.;
Rimmele, T.; IBIS Team
Bibcode: 2006SPD....37.0608C
Altcode: 2006BAAS...38..226C
The Interferometric Bidimensional Spectrometer (IBIS) is an advanced
instrument for imaging spectroscopy installed at the Dunn Solar
Telescope at NSO/Sacramento Peak. The instrument has been constructed by
a consortium of italian institutes and allows for observations of the
photosphere and chromosphere at high spatial, spectral, and temporal
resolution. Such observations are essential for performing spatial
and spectral comparisons with numerical simulations. We will present
some of the performance characteristics of the instrument and show some
examples of the IBIS data. We will also show some initial results of the
recently tested polarimetric mode. IBIS is available for community use
as a facility instrument of NSO.IBIS has been funded by the Italian
Research Ministry (MIUR), the Italian Institute for Astrophysics
(INAF), and the Universities of Florence and Rome. Additional support
is provided by the National Solar Observatory.
Title: High Resolution Spectropolarimetry of Penumbral Formation
with IBIS
Authors: Reardon, Kevin; Casini, R.; Cavallini, F.; Tomczyk, S.;
Rouppe van der Voort, L.; Van Noort, M.; Woeger, F.; Socas Navarro,
H.; IBIS Team
Bibcode: 2006SPD....37.3503R
Altcode: 2006BAAS...38..260R
We present the results of first spectropolarimetric observations
made with the Interferometric Bidimensional Spectrometer (IBIS)
at the NSO/Dunn Solar Telescope. The use of narrowband imaging and
post-facto reconstruction techniques allows for observations close
to the diffraction limit of the vector magnetic field. We will show
observations of the the formation of an individual penumbral filament
around a small pore. We measure the magnetic field and velocity field
of the forming penumbral filament. The spectropolarimetric mode of
IBIS will be available to the community in the fall of 2006.
Title: Imaging Spectroscopy Of Sunspots Using IBIS
Authors: Balasubramaniam, K. S.; Gary, G. A.; Reardon, K.
Bibcode: 2006SPD....37.0712B
Altcode: 2006BAAS...38..229B
We use the Interferometric BIdimensional Spectrometer (IBIS) of
the INAF/Arcetri Astrophysical Observatory and installed at the
National Solar Observatory (NSO) Dunn Solar Telescope, to understand
the structure of sunspots. These high resolution observations were
acquired on 2004 July 30-31, of active region NOAA 10654, using the
high order NSO adaptive optics system. We map the spatio-temporal
variation of the penumbral Doppler signatures in three spectral
lines, FeI 6301.5 Å, FeII 7224.4 Å, and CaII 8542.6 Å, from the
photosphere to the chromosphere. From a 70-minute temporal average
of individual 32-second cadence Doppler observations we find that
the averaged velocities decrease with height, about 3.5 times larger
in the deeper photosphere (FeII 7224.4 Å height-of-formation ≈50
km) than in the upper photosphere FeI 6301.5 Å height-of-formation
≈350 km), There is a remarkable coherence of Doppler signals over
the height difference of 300 km. From a high-speed animation of the
Doppler sequence we find evidence for what appears to be ejection of
high speed gas concentrations from edges of penumbral filaments into
the surrounding granular photosphere. The Evershed flow persists a few
arcseconds beyond the traditionally demarcated penumbra-granulation
boundary. We present these and other results and discuss implications
of these measurements for sunspot models.
Title: High-resolution IBIS Observations and Comparison with 3D
Simulations .
Authors: Asensio Ramos, A.; Janssen, K.; Cauzzi, G.; Reardon, K.
Bibcode: 2006MSAIS...9...59A
Altcode:
High resolution observations of a very quiet region of the solar
surface have been obtained with IBIS (Interferometric BIdimensional
Spectrometer) in the non-magnetic Fe I 7090.4 Å spectral line. We
present a first comparison between the observed, spatially resolved,
spectral data and the simulated spectra in a 3D snapshot of a
radiation-hydrodynamical simulation of the solar atmosphere. Preliminary
results indicate that the simulations reproduce quite well many of
the observational properties of the high resolution IBIS data, even
though the simulations present a velocity distribution that contains
values quite larger than the observed ones.
Title: IBIS instrumental characteristics and first results
Authors: Cavallini, F.; Reardon, K.
Bibcode: 2006MSAIS...9...55C
Altcode:
The Interferometric BIdimensional Spectrometer (IBIS) was installed in
June 2003 at the DST/NSO, where it is used in conjuction with a high
order AO system. IBIS has since proved to be a reliable and versatile
instrument for performing high resolution observations in both the
photosphere and chromosphere. We describe here the instrument and its
performance characteristics especially with respect to the obtainable
spectral, temporal and spatial resolutions, providing examples of the
actual observations.
Title: Quiet Solar Photosphere: Comparisons of High Resolution
Observations with 3-D Simulations
Authors: Cauzzi, G.; Asensio Ramos, A.; Reardon, K.; Janssen, K.
Bibcode: 2005ESASP.600E..12C
Altcode: 2005dysu.confE..12C; 2005ESPM...11...12C
No abstract at ADS
Title: Photospheric and Chromospheric structure of Sunspots using
IBIS.
Authors: Balasubramaniam, K. S.; Gary, G. A.; Reardon, K.
Bibcode: 2005AGUSMSP11A..04B
Altcode:
We use the Interferometric BIdimensional Spectrometer (IBIS) of the
INAF/Arcetri Astrophysical Observatory and installed at the National
Solar Observatory's (NSO) Dunn Solar Telescope, to understand the
structure of sunspots. Using the spectral lines FeI 6301.5Å, FeII
7224.4Å and CaII 8542.6Å, we examine the spectroscopic variation of
sunspot penumbral and umbral structures about the heights of formation
of these lines. Simultaneous white-light imaging data helps us to
register and track the images. We map the spatio-temporal variation
of Doppler signatures in these spectral lines, from the photosphere
to the chromosphere, and discuss the implication of these variations
for sunspot models. These high resolution observations were acquired
on 2004 July 30-31, on a sunspot NOAA 10654, using the higher order
NSO adaptive optics system.
Title: A Solar Data Model for Use in Virtual Observatories
Authors: Reardon, K. P.; Bentley, R. D.; Messerotti, M.; Giordano, S.
Bibcode: 2004AAS...204.7003R
Altcode: 2004BAAS...36Q.796R
The creation of a virtual solar observatories relies heavily on the
merging of the metadata describing different datasets into a common
form so that it can be handled in a standard way for all associated
resources. In order to bring together the varied data descriptions
that already exist, it is necessary to have a common framework on
which all the different datasets can be represented. The definition of
this framework is done through a data model which attempts to provide
a simplified but realistic description of the various entities that
make up a data set or solar resource. We present the solar data
model which has been developed as part of the European Grid of Solar
Observations (EGSO) project. This model attempts to include many of
the different elements in the field of solar physics, including data
producers, data sets, event lists, and data providers. This global
picture can then be used to focus on the particular elements required
for a specific implementation. We present the different aspects of
the model and describe some systems in which portions of this model
have been implemented.
Title: IBIS Observations of Quiet Sun Photosphere - Velocity Structure
from Fe I 7090.4 Å
Authors: Janßen, Katja; Cauzzi, Gianna; Falchi, Ambretta; Cavallini,
Fabio; Reardon, Kevin
Bibcode: 2004IAUS..223..631J
Altcode: 2005IAUS..223..631J
In our contribution we introduce the new Interferometric BIdimensional
Spectrometer (IBIS) and present the first results on bisector velocities
of two dimensional spectral scans in FeI 7090.4 Å comparing granules
and intergranular regions.
Title: Recent results from IBIS
Authors: Cavallini, F.; Baffa, C.; Reardon, K.; Berrilli, F.;
Cantarano, S.; Egidi, A.
Bibcode: 2003MmSAI..74..796C
Altcode:
IBIS (Interferometric BIdimensional Spectrometer) is a new instrument
for solar bidimensional spectroscopy. It essentially consists
of two Fabry-Perot interferometers, piezo-scanned and capacity
servo-controlled, used in classic mount and in axial-mode, in series
with a set of narrow-band interference filters. This instrument will
operate on a large field of view (80") and on a large wavelength
range (580 - 860 nm), with high spectral, spatial and temporal
resolution. IBIS, developed to become one of the focal plane instruments
of THEMIS, has been completed in its essential form and some tests have
been already performed. It is now possible therefore to compare expected
with measured values of the more relevant instrumental parameters.
Title: The Italian solar data archives: national and European
perspectives
Authors: Messerotti, M.; Coretti, I.; Padovan, S.; Zlobec, P.;
Antonucci, E.; Cora, A.; Volpicelli, C. A.; Dimitoglou, G.; Reardon,
K.; Tripicchio, A.; Severino, G.; EGSO Team
Bibcode: 2003MmSAI..74..391M
Altcode:
We discuss the present status of the solar data archives geographically
distributed in the Italian Astronomical Observatories of the National
Institute for Astrophysics (INAF). In particular, we describe the
national project SOLARNET (SOLAR NETwork) aimed at federating all the
Italian solar archives as a distributed database, the first step toward
an Italian Virtual Solar Observatory (IVSO), and the European Grid
for Solar Observations (EGSO) project, which is under implementation
to construct the basis for a large solar archive federation based on
the Grid architecture to provide the scientific user with advanced
resources such as a solar feature catalogue.
Title: EGSO - The European Grid of Solar Observations
Authors: Reardon, K.; Antonucci, E.; Giordano, S.; Severino, G.;
Messerotti, M.; EGSO Team
Bibcode: 2003MmSAI..74..823R
Altcode:
The European Grid of Solar Observations (EGSO) project aims to
produce the framework for a coordinated community-wide resource for
obtaining and reducing solar observations. The EGSO will be capable of
sharing resources coming from all types of providers, while ensuring
scalability, security, and compatibility among all datasets. The user
will be provided with a customizable search interface from which to
simultaneously browse or data mine a range of solar and heliospheric
data archives. In essence, the EGSO will create the fabric of a virtual
solar observatory.
Title: Characterization of the IBIS Transmission Profile
Authors: Reardon, K.; Cavallini, F.
Bibcode: 2003MmSAI..74..815R
Altcode:
We describe the techniques used to characterize the components of
the IBIS instrument in the laboratory in order to determine the
operational performance of the completed instrument. In particular,
we have measured the surface and coating irregularities of the two
Fabry-Perot interferometers at the heart of IBIS. From this we construct
a theoretical transmission profile for the instrument and relate that
to the accuracy that can be obtained in measurements of the Sun.
Title: In-flight Calibration of the UVCS White Light Channel
Authors: Romoli, M.; Frazin, R. A.; Kohl, J. L.; Gardner, L. D.;
Cranmer, S. R.; Reardon, K.; Fineschi, S.
Bibcode: 2002ISSIR...2..181R
Altcode: 2002ESASR...2..181R; 2002rcs..conf..181R
The UVCS White Light Channel (WLC) is designed to measure the linearly
polarized radiance (pB) of the corona, in the wavelength band from 450
nm to 600 nm, in order to derive one of the fundamental parameters of
the solar corona: the electron density. This paper gives a thorough
description of the in-flight radiometric calibration of the WLC, which
uses the star α Leo and the planet Jupiter as transfer standards
and is based on calibrations of ground-based instruments. The
method for computing the polarized radiance from the measurements
is also described, together with the stray light and polarization
characterizations obtained from dedicated, in-flight measurements.
Title: Simultaneous Hα and X-ray Observations of Prominence Eruption
and Disappearance
Authors: Tonooka, H.; Matsumoto, R.; Miyaji, S.; Martin, S. F.;
Canfield, R. C.; Reardon, K.; McAllister, A.; Shibata, K.
Bibcode: 2000AdSpR..26..473T
Altcode:
Prominence eruptions or disappearances observed with an Hα limb
filtergraph can be classified into 3 categories, the eruptive
prominence, the quasi-eruptive prominence, and the disappearing
prominence. We investigated their mechanism by comparing the results
of simultaneous observations by Yohkoh SXT and Hα. We found that soft
X-ray features change in both eruptive prominences and quasieruptive
prominences, whereas no significant change takes place in disappearing
prominences.In one prominence eruption event soft X-ray cusp structure
suggests that the reconnection point is just below the Hα prominence
Title: The Eruptive Flare of 15 November 1991: Preflare Phenomena
Authors: Canfield, Richard C.; Reardon, Kevin P.
Bibcode: 1998SoPh..182..145C
Altcode:
We present and interpret observations of the preflare phase of the
eruptive flare of 15 November, 1991 in NOAA AR 6919. New flux emerged
in this region, indicated by arch filaments in Hα and increasing
vertical flux in vector magnetograms. With increasing frequency
before the eruption, transient dark Hα fibrils were observed that
crossed Hα bright plage and the magnetic inversion line to extend
from the region of flux emergence to the filament, whose eruption was
associated with the flare. These crossing fibrils were dynamic, and
were often associated with sites of propagating torsional motion. These
sites propagated from the region of flux emergence into the filament
flux system. We interpret these morphological and dynamic features in
terms of relaxation after magnetic reconnection episodes which create
longer field lines within the filament flux system, as envisioned in
the tether cutting model, and transfer twist to it, as well.
Title: Design Issues for HTML-Based Solar Archive Interfaces
Authors: Reardon, Kevin
Bibcode: 1998ASPC..155..292R
Altcode: 1998sasp.conf..292R
No abstract at ADS
Title: Whole Sun Catalog: Design and Implementation
Authors: Dimitoglou, G.; Mendiboure, C.; Reardon, K.; Sanchèz-Duarte,
L.
Bibcode: 1998ASPC..155..297D
Altcode: 1998sasp.conf..297D
No abstract at ADS
Title: The RISE-PSPT telescope operative at the OAR
Authors: Ermolli, I.; Fofi, M.; Torelli, M.; Reardon, K.
Bibcode: 1998MmSAI..69..631E
Altcode:
No abstract at ADS
Title: SXR Coronal Polar Jets and Recurrent Flashes
Authors: Koutchmy, S.; Hara, H.; Shibata, K.; Suematsu, Y.; Reardon, K.
Bibcode: 1998ASSL..229...87K
Altcode: 1998opaf.conf...87K
No abstract at ADS
Title: Soft X-Ray Features of Prominence Eruption and Disappearance
Authors: Tonooka, H.; Matsumoto, R.; Miyaji, S.; Martin, S. F.;
Canfield, R. C.; Reardon, K.; McAllister, A.; Shibata, K.
Bibcode: 1998ASSL..229..371T
Altcode: 1998opaf.conf..371T
No abstract at ADS
Title: Variation of the Solar Granulation Over the Cycle: Previous
Results and Future Observations
Authors: Roudier, Th.; Reardon, K.
Bibcode: 1998ASPC..140..455R
Altcode: 1998ssp..conf..455R
No abstract at ADS
Title: The Role of Data Archives in Synoptic Solar Physics
Authors: Reardon, Kevin
Bibcode: 1998ASPC..140..467R
Altcode: 1998ssp..conf..467R
The detailed study of solar cycle variations requires analysis of
recorded datasets spanning many years of observations, that is,
a data archive. The use of digital data, combined with powerful
database server software, gives such archives new capabilities
to provide, quickly and flexibly, selected pieces of information
to scientists. Use of standardized protocols will allow multiple
databases, independently maintained, to be seamlessly joined, allowing
complex searches spanning multiple archives. These data archives also
benefit from being developed in parallel with the telescope itself,
which helps to assure data integrity and to provide close integration
between the telescope and archive. Development of archives that can
guarantee long-term data availability and strong compatibility with
other projects makes solar-cycle studies easier to plan and realize.
Title: The Magneto-Optical Filter in Napoli: Perspectives and Test
Observations
Authors: Moretti, P. F.; Severino, G.; Cauzzi, G.; Reardon, K.;
Straus, T.; Cacciani, A.; Marmolino, C.; Oliviero, M.; Smaldone, L. A.
Bibcode: 1997ASSL..225..293M
Altcode: 1997scor.proc..293M
An observing station based on the Magneto-Optical-Filter (MOF)
technology is being installed at Osservatorio Astronomico di
Capodimonte, in Napoli. In this paper, the main characteristics and
goals of this new instrument are discussed, and several velocity and
magnetic observations from a test campaign are shown.
Title: X-ray photon spectroscopy with the YOHKOH Soft X-ray telescope
Authors: Labonte, B.; Reardon, K.
Bibcode: 1997SPD....28.0140L
Altcode: 1997BAAS...29..886L
Individual X-ray photons in the keV energy range produce hundreds of
photoelectrons in a single pixel of a CCD array detector. The number
of photoelectrons produced is a linear function of the photon energy,
allowing the measurement of spectral information with an imaging
detector system. The Yohkoh Soft X-ray Telescope uses a CCD in an
integrating mode and makes temperature estimates from multiband filter
photometry. We show how the SXT can be used in a new way to perform
a limited type of photon spectroscopy. By measuring the variance in
intensity through a single filter of an x-ray source on repeated SXT
images, the mean energy per detected photon can be determined. This
value is related to the underlying coronal spectrum, and hence can
be used to deduce the plasma temperature. We compare the results
of the temperatures derived using this new technique on a series of
SXT images of a post-flare loop system with the temperatures derived
using the standard flux-ratio method. We demonstrate that the bright
postflare loops really are cooler than the surrounding material, as
shown by Tsuneta et al. (1992). Given the large dynamic range of the
soft x-ray flux observed from the Sun, we describe the requirements for
a future instrument that would take advantage of photon spectroscopy.
Title: SXR Coronal Flashes.
Authors: Koutchmy, S.; Hara, H.; Suematsu, Y.; Reardon, K.
Bibcode: 1997A&A...320L..33K
Altcode:
We provide evidence for the existence of a new type of soft X-ray
(SXR) brightening event that we call coronal flashes. The phenomenon
was observed on deep time series taken with the SXT of Yohkoh in the
north polar coronal hole, near the sunspot minimum. Events last as
short as 1.5 mn and the corresponding SXR flux span the range of
energies, from single pixel brightenings corresponding to fluxes
of about 10^24^erg but barely surpassing the level of the noise,
to higher and more smeared multiple px brightenings still orders
of magnitude smaller than the known small SXR bright points and/or
transient brightenings. The typical occurrence rate of flashes is
1-event/arcmin^2^/5mn with a 1/2mn integration time. At least part of
the coronal flashes are recurrent and some of them could be associated
with a SXR jet; it is not clear what is their optical counterpart.
Title: ARTHEMIS: The Archive Project for the IPM and THEMIS
Authors: Reardon, K.; Severino, G.; Cauzzi, G.; Gomez, M. T.; Straus,
T.; Russo, G.; Smaldone, G.; Marmolino, C.
Bibcode: 1997ASPC..118..398R
Altcode: 1997fasp.conf..398R
We describe the plan for ARTHEMIS, the italian archive for THEMIS, from
the point of view of the prospective users of the archive. This archive
is designed to store the data from the Italian Panoramic Monochromator
(IPM) instrument installed on THEMIS as well as the full-disk images
obtained by the telescope. We break the expected users down into
seven categories: a) prospective IPM users; b) campaign planners; c)
data analysts, d) external collaborators; e) instrument monitors, f)
archival observers; and g) the general public.
Title: ARTHEMIS: The archive project for the Italian Panoramic
Monochromator
Authors: Reardon, K.; Severino, G.; Cauzzi, G.; Gomez, M. T.; Straus,
T.; Russo, G.; Smaldone, L. A.; Marmolino, C.
Bibcode: 1997MmSAI..68..499R
Altcode:
No abstract at ADS
Title: Coronal heating experiments of the Williams College Group at
Mukandgarh Fort, Rajasthan.
Authors: Pasachoff, J. M.; Babcock, B. A.; Diaz, S.; Reardon, K. P.;
Kutner, E. R.
Bibcode: 1997KodOB..13...75P
Altcode:
The authors report on the Williams College expedition to Mukandgarh
Fort, Rajasthan, for the total solar eclipse of 24 October 1995. The
main experiments were a search for 1 Hz oscillations in coronal loops
as an indication of magnetohydrodynamic theories of coronal heating
and a mapping of the coronal temperature through comparison of images
at specific ultraviolet wavelengths, measuring the difference between
the photospheric and coronal continuum. The authors also obtained a
variety of coronal images.
Title: H alpha Surges and X-Ray Jets in AR 7260
Authors: Canfield, Richard C.; Reardon, Kevin P.; Leka, K. D.; Shibata,
K.; Yokoyama, T.; Shimojo, M.
Bibcode: 1996ApJ...464.1016C
Altcode:
We discuss nine events, observed simultaneously as jets in X-rays and
surges in Hα, which are associated with moving magnetic bipoles. The
X-ray jets share many features with those discovered by Yohkoh in active
regions, emerging flux regions, and X-ray bright points (see paper by
Shibata et al.); in particular, they originate near one end of a pair of
small flaring loops. The Hα surges are adjacent to the X-ray jets. At
the bases of these surges we observe both blueshifts (initially) and
redshifts (1-2 minutes later). All the observed surges spin in a sense
consistent with the relaxation of the twist stored in the magnetic
fields of the moving magnetic bipoles. Newly discovered phenomena
include footpoint convergence and moving-blueshift features. We develop a model of the role of magnetic reconnection in these
events. This model explains the temporal and spatial relationship
between the jets and surges, the role of the moving bipoles, the
flaring X-ray loops and their converging Hα footpoints, the Hα
moving-blueshift features, the direction and amount of spin of the
surges, and the relative temporal development of the Hα redshifts
and blueshifts.
Title: H alpha Surges and X-ray Jets in AR7260
Authors: Canfield, R. C.; Reardon, K. P.; Leka, K. D.; Shibata, K.;
Yokoyama, T.; Shimojo, M.
Bibcode: 1996mpsa.conf...49C
Altcode: 1996IAUCo.153...49C
No abstract at ADS
Title: YOHKOH SXT Observations of Prominence Eruption and
Disappearance
Authors: Tonooka, H.; Matsumoto, R.; Miyaji, S.; Martin, S. F.;
Canfield, R. C.; Reardon, K.; McAllister, A.; Shibata, K.
Bibcode: 1996mpsa.conf..493T
Altcode: 1996IAUCo.153..493T
No abstract at ADS
Title: Study of the High-Frequency Coronal-Loop Oscillation Spectrum
at the 1994 Total Solar Eclipse
Authors: Pasachoff, J. M.; Babcock, B.; Diaz, J. S.; Reardon, K.;
Nichols-Kiley, R.
Bibcode: 1995AAS...18710106P
Altcode: 1995BAAS...27.1427P
We summarize results from observations made at the November 3, 1994,
total solar eclipse from the International Astronomical Union site
in Putre, Chile, through partly cloudy skies. We discuss the image
reduction and analysis of two simultaneous series of coronal images with
a cadence of 10 frames per second for a total time of 160 seconds. One
series of images was taken through a filter isolating the 530.3 nm
[Fe XIV] coronal green line and the other through a 10 nm filter in
the nearby K-corona continuum. After standard calibrations and image
alignment, we use Fourier analysis to search in the [Fe XIV] channel
for high-frequency ( 1 Hz) intensity oscillations in loops at the base
of the corona. Such oscillations are predicted as a result of density
fluctuations from the resonant absorption of high-frequency Alfven
waves. The dissipation of a significant amount of mechanical energy from
the photosphere into the corona through this mechanism could provide
sufficient energy to heat the corona. The observations were supported by
NSF ATM-9005194 and Education Division DUE-9351279 grants; the National
Geographic Society through their Committee on Research and Explorations
(grant: 5190-94), and the Keck Northeastern Astronomy Consortium.
Title: Coronal Heating Studies at the 1994 Total Eclipse
Authors: Pasachoff, J. M.; Babcock, B.; Reardon, K.
Bibcode: 1995pist.conf...18P
Altcode:
No abstract at ADS
Title: Coronal Loop Interaction Observed at Visible Wavelengths
Authors: Smartt, R. N.; Zhang, Z.; Kim, I. S.; Reardon, K. P.
Bibcode: 1994scs..conf..219S
Altcode: 1994IAUCo.144..219S
Brightening is observed to occur in regions where two loops come
into contact, with resultant heating of the common plasma volume,
and subsequent cooling. The observations show systematically that a
brightness maximum in the cooler (634 Å) line lags that of the hotter
(5303 Å) line. Coalescence is evident in that the brightness can extend
away from the overlapping region along the adjacent parts of the loops.
Title: Filament Tether Cutting Before a Major Eruptive Flare
Authors: Canfield, R. C.; Blais, K. A.; Reardon, K. P.; Acton, Loren;
Kurokawa, H.
Bibcode: 1994ASPC...68..411C
Altcode: 1994sare.conf..411C
No abstract at ADS
Title: The X Flare of 15 November, 1991: Preflare Flux Emergence,
Heating and Filament Eruption
Authors: Canfield, R. C.; Blais, K. A.; McClymont, A. N.; Metcalf,
T. R.; Reardon, K. P.; Wülser, J. -P.; Acton, L. W.; Kurokawa, H.;
Hirayama, T.
Bibcode: 1994xspy.conf..153C
Altcode:
No abstract at ADS
Title: Simultaneous IR and Visible Light Measurements of the Solar
Granulation
Authors: Keil, S.; Kuhn, J.; Lin, H.; Reardon, K.
Bibcode: 1994IAUS..154..251K
Altcode:
No abstract at ADS
Title: Coronal Images from the 1984 Solar Eclipse
Authors: Pasachoff, Jay M.; Reardon, Kevin P.; MacKenty, John W.
Bibcode: 1993SoPh..146..405P
Altcode:
We present digitized photographs of the white-light solar corona
taken during the total solar eclipse of 22-23 November, 1984, on both
calibrated black-and-white film and on color film. Conditions on site
in Hula, Papua New Guinea, were exceptionally clear. The color image
was used to produce an isophotal map of the inner corona, from which
a flattening coefficient of 0.23 was measured. The black-and-white
image was enhanced through a digital radial filter. Our images are the
best processed images available from the 1984 eclipse and so provide
important data for synoptic observations.
Title: Filament Tether Cutting Before a Major Eruptive Flare
Authors: Canfield, R. C.; Blais, K. A.; McClymont, A. N.; Metcalf,
T. R.; Reardon, K. P.; Wuelser, J. -P.; Acton, L. W.; Kurokawa, H.
Bibcode: 1993BAAS...25.1188C
Altcode:
No abstract at ADS
Title: High-Frequency Acoustic Waves in the Solar Atmosphere
Authors: Reardon, Kevin
Bibcode: 1991usra.conf..100R
Altcode:
No abstract at ADS