Author name code: goode
ADS astronomy entries on 2022-09-14
author:"Goode, Philip R."
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Title: Earth's Albedo 1998-2017 as Measured From Earthshine
Authors: Goode, P. R.; Pallé, E.; Shoumko, A.; Shoumko, S.;
Montañes-Rodriguez, P.; Koonin, S. E.
Bibcode: 2021GeoRL..4894888G
Altcode:
The reflectance of the Earth is a fundamental climate parameter
that we measured from Big Bear Solar Observatory between 1998
and 2017 by observing the earthshine using modern photometric
techniques to precisely determine daily, monthly, seasonal, yearly
and decadal changes in terrestrial albedo from earthshine. We find
the inter-annual fluctuations in albedo to be global, while the
large variations in albedo within individual nights and seasonal
wanderings tend to average out over each year. We measure a gradual,
but climatologically significant ∼0.5 W/m2 decline in the
global albedo over the two decades of data. We found no correlation
between the changes in the terrestrial albedo and measures of solar
activity. The inter-annual pattern of earthshine fluctuations are
in good agreement with those measured by CERES (data began in 2001)
even though the satellite observations are sensitive to retroflected
light while earthshine is sensitive to wide-angle reflectivity. The
CERES decline is about twice that of earthshine.
Title: The National Science Foundation's Daniel K. Inouye Solar
Telescope — Status Update
Authors: Rimmele, T.; Woeger, F.; Tritschler, A.; Casini, R.; de Wijn,
A.; Fehlmann, A.; Harrington, D.; Jaeggli, S.; Anan, T.; Beck, C.;
Cauzzi, G.; Schad, T.; Criscuoli, S.; Davey, A.; Lin, H.; Kuhn, J.;
Rast, M.; Goode, P.; Knoelker, M.; Rosner, R.; von der Luehe, O.;
Mathioudakis, M.; Dkist Team
Bibcode: 2021AAS...23810601R
Altcode:
The National Science Foundation's 4m Daniel K. Inouye Solar Telescope
(DKIST) on Haleakala, Maui is now the largest solar telescope in the
world. DKIST's superb resolution and polarimetric 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 flares and coronal mass ejections. Five
instruments, four of which provide highly sensitive measurements
of solar magnetic fields, including the illusive magnetic field of
the faint solar corona. The DKIST instruments will produce large and
complex data sets, which will be distributed through the NSO/DKIST Data
Center. DKIST has achieved first engineering solar light in December
of 2019. Due to COVID the start of the operations commissioning phase
is delayed and is now expected for fall of 2021. We present a status
update for the construction effort and progress with the operations
commissioning phase.
Title: On the sequence of deformable mirrors in MCAO: findings from
an on-sky, closed-loop experiment
Authors: Schmidt, Dirk; Gorceix, Nicolas; Goode, Philip
Bibcode: 2020SPIE11448E..42S
Altcode:
We performed an on-sky MCAO experiment using 4 deformable mirrors
(DMs) to analyze the relevance of their sequence to the residual
wavefront error. Two DMs were conjugate to 4 and 8 km. The other two
DMs were placed in pupil images upstream and downstream of the 4-km
and 8-km mirrors. At any time, both high altitude DMs were active but
only one pupil DM was active while the other one stayed flat. Firstly,
we found that the MCAO control loops using either pupil DM were stable
and robust. Dynamic misregistration, which was present for the first
pupil DM, was not an immediate problem for the controller. We did not
notice an apparent difference when repeatedly switching between the
pupil DMs during the operation. A closer analysis of the contrast in
the corrected images and AO telemetry indicates an advantage when the
pupil correction was applied with the DM that was downstream of the
high-altitude DMs. This finding is consistent in several data recorded
at different days. The difference, however, is small. A more detailed
analysis is probably needed to rule out error sources potentially not
considered herein to draw a final conclusion on the optimal sequence
of DMs in MCAO and its practical relevance.
Title: CYRA: the cryogenic infrared spectrograph for the Goode Solar
Telescope in Big Bear
Authors: Yang, Xu; Cao, Wenda; Gorceix, Nicolas; Plymate, Claude;
Shumoko, Sergey; Bai, XianYong; Penn, Matt; Ayres, Thomas; Coulter,
Roy; Goode, Philip R.
Bibcode: 2020SPIE11447E..AGY
Altcode: 2020arXiv200811320Y
CYRA (CrYogenic solar spectrogRAph) is a facility instrument of the
1.6-meter Goode Solar Telescope (GST) at the Big Bear Solar Observatory
(BBSO). CYRA focuses on the study of the near-infrared solar spectrum
between 1 and 5 microns, an under-explored region which is not only
fertile ground for photospheric magnetic diagnostics but also allows a
unique window into the chromosphere lying atop the photosphere. CYRA is
the first-ever fully cryogenic spectrograph in any solar observatory
with its two predecessors, on the McMath-Pierce and Mees Telescopes,
being based on warm optics except for the detectors and order
sorting filters. CYRA is used to probe magnetic fields in various
solar features and the quiet photosphere. CYRA measurements will
allow new and better 3D extrapolations of the solar magnetic field
and will provide more accurate boundary conditions for solar activity
models. The superior spectral resolution of 150,000 and better allows
enhanced observations of the chromosphere in the carbon monoxide (CO)
spectral bands and will yield a better understanding of energy transport
in the solar atmosphere. CYRA is divided into two optical sub-systems:
The Fore-Optics Module and the Spectrograph. The Spectrograph is
the heart of the instrument and contains the IR detector, grating,
slits, filters, and imaging optics all in a cryogenically cooled
Dewar (cryostat). The sensor is a 2048 by 2048 pixel HAWAII 2 array
produced by Teledyne Scientific and Imaging, LLC. The cryostat interior
and the readout electronics are maintained at 90 Kelvin by helium
refrigerant-based cryo-coolers, while the IR array is cooled to 30
Kelvin. The Fore-Optics Module de-rotates and stabilizes the solar
image, provides scanning capabilities and transfers the GST image
to the Spectrograph. CYRA has been installed and is undergoing its
commissioning phase. This paper reports on the design, implementation,
and operation of CYRA in detail. The preliminary scientific results
have been highlighted as well.
Title: The Daniel K. Inouye Solar Telescope - Observatory Overview
Authors: Rimmele, Thomas R.; Warner, Mark; Keil, Stephen L.; Goode,
Philip R.; Knölker, Michael; Kuhn, Jeffrey R.; Rosner, Robert R.;
McMullin, Joseph P.; Casini, Roberto; Lin, Haosheng; Wöger, Friedrich;
von der Lühe, Oskar; Tritschler, Alexandra; Davey, Alisdair; de Wijn,
Alfred; Elmore, David F.; Fehlmann, André; Harrington, David M.;
Jaeggli, Sarah A.; Rast, Mark P.; Schad, Thomas A.; Schmidt, Wolfgang;
Mathioudakis, Mihalis; Mickey, Donald L.; Anan, Tetsu; Beck, Christian;
Marshall, Heather K.; Jeffers, Paul F.; Oschmann, Jacobus M.; Beard,
Andrew; Berst, David C.; Cowan, Bruce A.; Craig, Simon C.; Cross,
Eric; Cummings, Bryan K.; Donnelly, Colleen; de Vanssay, Jean-Benoit;
Eigenbrot, Arthur D.; Ferayorni, Andrew; Foster, Christopher; Galapon,
Chriselle Ann; Gedrites, Christopher; Gonzales, Kerry; Goodrich, Bret
D.; Gregory, Brian S.; Guzman, Stephanie S.; Guzzo, Stephen; Hegwer,
Steve; Hubbard, Robert P.; Hubbard, John R.; Johansson, Erik M.;
Johnson, Luke C.; Liang, Chen; Liang, Mary; McQuillen, Isaac; Mayer,
Christopher; Newman, Karl; Onodera, Brialyn; Phelps, LeEllen; Puentes,
Myles M.; Richards, Christopher; Rimmele, Lukas M.; Sekulic, Predrag;
Shimko, Stephan R.; Simison, Brett E.; Smith, Brett; Starman, Erik;
Sueoka, Stacey R.; Summers, Richard T.; Szabo, Aimee; Szabo, Louis;
Wampler, Stephen B.; Williams, Timothy R.; White, Charles
Bibcode: 2020SoPh..295..172R
Altcode:
We present an overview of the National Science Foundation's Daniel
K. Inouye Solar Telescope (DKIST), its instruments, and support
facilities. The 4 m aperture DKIST provides the highest-resolution
observations of the Sun ever achieved. The large aperture of
DKIST combined with state-of-the-art instrumentation provide the
sensitivity to measure the vector magnetic field in the chromosphere
and in the faint corona, i.e. for the first time with DKIST we will
be able to measure and study the most important free-energy source
in the outer solar atmosphere - the coronal magnetic field. Over its
operational lifetime DKIST will advance our knowledge of fundamental
astronomical processes, including highly dynamic solar eruptions
that are at the source of space-weather events that impact our
technological society. Design and construction of DKIST took over two
decades. DKIST implements a fast (f/2), off-axis Gregorian optical
design. The maximum available field-of-view is 5 arcmin. A complex
thermal-control system was implemented in order to remove at prime
focus the majority of the 13 kW collected by the primary mirror and
to keep optical surfaces and structures at ambient temperature, thus
avoiding self-induced local seeing. A high-order adaptive-optics
system with 1600 actuators corrects atmospheric seeing enabling
diffraction limited imaging and spectroscopy. Five instruments, four
of which are polarimeters, provide powerful diagnostic capability
over a broad wavelength range covering the visible, near-infrared,
and mid-infrared spectrum. New polarization-calibration strategies
were developed to achieve the stringent polarization accuracy
requirement of 5×10−4. Instruments can be combined and
operated simultaneously in order to obtain a maximum of observational
information. Observing time on DKIST is allocated through an open,
merit-based proposal process. DKIST will be operated primarily in
"service mode" and is expected to on average produce 3 PB of raw
data per year. A newly developed data center located at the NSO
Headquarters in Boulder will initially serve fully calibrated data to
the international users community. Higher-level data products, such as
physical parameters obtained from inversions of spectro-polarimetric
data will be added as resources allow.
Title: Magnetic Field Dynamics and Varying Plasma Emission in Large
Scale Coronal Loops
Authors: Yurchyshyn, V.; Sahin, S.; Goode, P. R.; Kumar, P.; Kilcik,
A.; Ahn, K.; Yang, X.
Bibcode: 2019AGUFMSH11C3399Y
Altcode:
We studied the evolution of magnetic fields at footpoints of two warm
coronal loops observed on 5 May 2016 in NOAA AR 12542 (Loop I) and
17 Dec 2015 in NOAA AR 12470 (Loop II). These loops were connecting
a plage region with sunspot periphery (Loop I) and a sunspot umbra
(Loop II). We used Solar Dynamics Observatory (SDO) and Goode Solar
Telescope (GST) data to describe the phenomenon and understand its
causes. The study indicates loop brightening episodes were associated
with magnetic flux emergence and cancellation processes observed in
SDO's Helioseismic and Magnetic Imager (HMI) and GST's Near InfraRed
Imaging Spectrapolarimeter (NIRIS) data. The observed activity was
driven by magnetic reconnection between small-scale emerging dipoles
and large-scale pre-existing fields, suggesting that the reconnection
occurred in the lower chromosphere at the edge of an extended plage
region, where the loops were rooted. We suggest that plasma, evaporated
during these reconnection events, gradually filled the loops and as it
cooled the visible density front propagated from one footpoint of the
loop to another at a rate of 90-110 km/s. This study also indicates
that at least some of the bright loops seen in SDO Atmospheric Imaging
Assembly images rooted in sunspot umbra may be heated due to magnetic
activity taking place at the remote (non-sunspot) footpoint.
Title: From Clear to DKIST: advancing solar MCAO from 1.6 to 4 meters
Authors: Schmidt, Dirk; Marino, Jose; Gorceix, Nicolas; Rimmele,
Thomas; Johnson, Luke; Berkefeld, Thomas; Goode, Philip
Bibcode: 2018SPIE10703E..26S
Altcode:
The MCAO pathfinder Clear on the 1.6-meter Goode Solar Telescope
has been enabling us to advance solar MCAO from early conceptual
demonstrations to science grade wide-field image correction. We report
on recent improvements to the control loop and we comment on issues
such as the co-aligning of wavefront sensors and deformable mirrors and
the sensitivity of wavefront sensor gains. Further, we comment on the
challenges to wavefront sensing and the control system architecture
faced when scaling up to a 4-meter aperture. Finally, we present an
early concept of the future MCAO upgrade for the Daniel K. Inouye
Solar Telescope.
Title: Status of the Daniel K. Inouye Solar Telescope: unraveling
the mysteries the Sun.
Authors: Rimmele, Thomas R.; Martinez Pillet, Valentin; Goode, Philip
R.; Knoelker, Michael; Kuhn, Jeffrey Richard; Rosner, Robert; Casini,
Roberto; Lin, Haosheng; von der Luehe, Oskar; Woeger, Friedrich;
Tritschler, Alexandra; Fehlmann, Andre; Jaeggli, Sarah A.; Schmidt,
Wolfgang; De Wijn, Alfred; Rast, Mark; Harrington, David M.; Sueoka,
Stacey R.; Beck, Christian; Schad, Thomas A.; Warner, Mark; McMullin,
Joseph P.; Berukoff, Steven J.; Mathioudakis, Mihalis; DKIST Team
Bibcode: 2018AAS...23231601R
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 address many of the fundamental problems
in solar and stellar astrophysics, including the origin of stellar
magnetism, the mechanisms of coronal heating and drivers of the
solar wind, flares, coronal mass ejections and variability in solar
and stellar output. DKIST will also address basic research aspects of
Space Weather and help improve predictive capabilities. In combination
with synoptic observations and theoretical modeling DKIST will unravel
the many remaining mysteries of the Sun.The construction of DKIST is
progressing on schedule with 80% of the facility complete. Operations
are scheduled to begin early 2020. DKIST will replace the NSO
facilities on Kitt Peak and Sac Peak with a national facility with
worldwide unique capabilities. The design allows DKIST to operate as
a coronagraph. Taking advantage of its large aperture and infrared
polarimeters DKIST will be capable to routinely measure the currently
illusive 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. Achieving this resolution
is critical for the ability to observe magnetic structures at their
intrinsic, fundamental scales. Five instruments will be available at
the start of operations, four of which will provide highly sensitive
measurements of solar magnetic fields throughout the solar atmosphere
- from the photosphere to the corona. The data from these instruments
will be distributed to the world wide community via the NSO/DKIST data
center located in Boulder. We present examples of science objectives
and provide an overview of the facility and project status, including
the ongoing efforts of the community to develop the critical science
plan for the first 2-3 years of operations.
Title: High-resolution Observations of a White-light Flare with
Goode Solar Telescope
Authors: Yurchyshyn, Vasyl; Kumar, Pankaj; Abramenko, Valentyna; Xu,
Yan; Goode, Philip R.; Cho, Kyung-Suk F.
Bibcode: 2018tess.conf21702Y
Altcode:
Using high resolution data from the Goode Solar Telescope (GST)
we studied the fine spatial and temporal structure of an M1.3 white
light (WL) flare, which was one of the three homologous solar flares
(C6.8, M1.3, and M2.3) observed in a close proximity to the west solar
limb. The RHESSI photon spectra for the M1.3 flare showed strongly
accelerated electrons with energies above 100 keV. Comparison of
HXR photon spectra for the three flares suggests that either thermal
energy of order of 1030 ergs and/or high energy electrons
(>50 keV) are necessary to produce a WL flare. The strong and
compact WL cores were ≈0.15 Mm across with an area of about
1014 cm2 . The observed TiO enhancements are
not normally distributed and are structured by the magnetic field of
the penumbra. Several of the TiO cores were not co-spatial with the Hα
emission, which suggests that the TiO and chromospheric emission did not
originate in the same chromospheric volume as some models suggest. We
thus conclude that fine temporal and spatial structure of the WL flare
was largely defined by the associated magnetic fields, which favors
the direct heating models, where the flare energy is directly deposited
in the temperature minimum region by the accelerated electrons.
Title: The NST observation of a small loop eruption in He I D3 line
on 2016 May 30
Authors: Kim, Yeon-Han; Xu, Yan; Bong, Su-Chan; Lim, Eunkyung; Yang,
Heesu; Park, Young-Deuk; Yurchyshyn, Vasyl B.; Ahn, Kwangsu; Goode,
Philip R.
Bibcode: 2017SPD....4810505K
Altcode:
Since the He I D3 line has a unique response to a flare impact on the
low solar atmosphere, it can be a powerful diagnostic tool for energy
transport processes. In order to obtain comprehensive data sets for
studying solar flare activities in D3 spectral line, we performed
observations for several days using the 1.6m New Solar Telescope of
Big Bear Solar Observatory (BBSO) in 2015 and 2016, equipped with
the He I D3 filter, the photospheric broadband filter, and Near IR
imaging spectrograph (NIRIS). On 2016 May 30, we observed a small
loop eruption in He I D3 images associated with a B class brightening,
which is occurred around 17:10 UT in a small active region, and dynamic
variations of photospheric features in G-band images. Accordingly,
the cause of the loop eruption can be magnetic reconnection driven by
photospheric plasma motions. In this presentation, we will give the
observation results and the interpretation.
Title: High-resolution Observations of a White-light Flare with NST
Authors: Yurchyshyn, V.; Kumar, P.; Abramenko, V.; Xu, Y.; Goode,
P. R.; Cho, K. -S.; Lim, E. -K.
Bibcode: 2017ApJ...838...32Y
Altcode:
Using high-resolution data from the New Solar Telescope, we studied
fine spatial and temporal details of an M1.3 white-light (WL) flare,
which was one of three homologous solar flares (C6.8, M1.3, and M2.3)
observed in close proximity to the west solar limb on 2014 October 29
in NOAA active region 12192. We report that the TiO WL flare consists of
compact and intense cores surrounded by less intense spatial halos. The
strong and compact WL cores were measured to be ≈ 0.2 Mm across,
with an area of about 1014 cm2. Several TiO
features were not cospatial with Hα flare ribbons and were displaced
toward the disk center by about 500 km, which suggests that the TiO
and Hα radiation probably did not originate in the same chromospheric
volume. The observed TiO intensity enhancements are not normally
distributed and are structured by the magnetic field of the penumbra.
Title: Clear widens the field for observations of the Sun with
multi-conjugate adaptive optics
Authors: Schmidt, Dirk; Gorceix, Nicolas; Goode, Philip R.; Marino,
Jose; Rimmele, Thomas; Berkefeld, Thomas; Wöger, Friedrich; Zhang,
Xianyu; Rigaut, François; von der Lühe, Oskar
Bibcode: 2017A&A...597L...8S
Altcode:
The multi-conjugate adaptive optics (MCAO) pathfinder Clear
on the New Solar Telescope in Big Bear Lake has provided the
first-ever MCAO-corrected observations of the Sun that show a
clearly and visibly widened corrected field of view compared to
quasi-simultaneous observations with classical adaptive optics (CAO)
correction. Clear simultaneously uses three deformable mirrors, each
conjugated to a different altitude, to compensate for atmospheric
turbulence. While the MCAO correction was most effective over an
angle that is approximately three times wider than the angle that was
corrected by CAO, the full 53'' field of view did benefit from MCAO
correction. We further demonstrate that ground-layer-only correction
is attractive for solar observations as a complementary flavor of
adaptive optics for observational programs that require homogenous
seeing improvement over a wide field rather than diffraction-limited
resolution. We show illustrative images of solar granulation and
of a sunspot obtained on different days in July 2016, and present a
brief quantitative analysis of the generalized Fried parameters of
the images. The movies associated to Fig. 1 are available at http://www.aanda.org
Title: High Resolution He I 10830 AA Narrow-band Imaging of an
M-class Flare. I - Analysis of Sunspot Dynamics during Flaring
Authors: Wang, Ya; Su, Yingna; Hong, Zhenxiang; Zeng, Zhicheng; Ji,
Kaifan; Goode, Philip R.; Cao, Wenda; Ji, Haisheng
Bibcode: 2016ApJ...833..250W
Altcode:
In this paper, we report our first-step results of high resolution
He I 10830 Å narrow-band imaging (bandpass: 0.5 Å) of an M1.8 class
two-ribbon flare on 2012 July 5. The flare was observed with the 1.6
m aperture New Solar Telescope at Big Bear Solar Observatory. For
this unique data set, sunspot dynamics during flaring were analyzed
for the first time. By directly imaging the upper chromosphere,
running penumbral waves are clearly seen as an outward extension
of umbral flashes; both take the form of absorption in the 10830 Å
narrow-band images. From a space-time image made of a slit cutting
across a flare ribbon and the sunspot, we find that the dark lanes
for umbral flashes and penumbral waves are obviously broadened after
the flare. The most prominent feature is the sudden appearance of an
oscillating absorption strip inside the ribbon when it sweeps into the
sunspot’s penumbral and umbral regions. During each oscillation,
outwardly propagating umbral flashes and subsequent penumbral waves
rush out into the inwardly sweeping ribbon, followed by a return
of the absorption strip with similar speed. We tentatively explain
the phenomena as the result of a sudden increase in the density
of ortho-helium atoms in the area of the sunspot being excited by
the flare’s extreme ultraviolet illumination. This explanation is
based on the observation that 10830 Å absorption around the sunspot
area gets enhanced during the flare. Nevertheless, questions are still
open and we need further well-devised observations to investigate the
behavior of sunspot dynamics during flares.
Title: High resolution He I 10830 angstrom narrow-band imaging of
an M-class flare.I-analysis of sunspot dynamics during flaring
Authors: Wang, Ya; Su, Yingna; Hong, Zhenxiang; Zeng, Zhicheng; Ji,
Kaifan; Goode, Philip R.; Cao, Wenda; Ji, Haisheng
Bibcode: 2016usc..confE..38W
Altcode: 2016arXiv161009227W
We report our first-step results of high resolution He I 1083
nm narrow-band imaging of an M 1.8 class two-ribbon flare on July
5,2012. The flare was observed with the 1.6 meter aperture New Solar
Telescope at Big Bear Solar Observatory. For this unique data set,
sunspot dynamics during flaring were analyzed for the first time. By
directly imaging the upper chromosphere, running penumbral waves
are clearly seen as an outward extention of umbral flashes, both
take the form of absorption in our 1083 nm narrow-band images. From
a space-time image made of a slit cutting across the ribbon and the
sunspot, we find that dark lanes for umbral flashes and penumbral waves
are obviously broadened after the flare. The most prominent feature
is the sudden appearance of an oscillating absorption strip inside
one ribbon of the flare when it sweeps into sunspot's penumbral and
umbral regions. During each oscillation, outwardly propagating umbral
flashes and subsequent penumbral waves rush out into the inwardly
sweeping ribbon, followed by a returning of the absorption strip with
similar speed. We tentatively explain the phenomenon as the result of
a sudden increase in the density of ortho-Helium atoms in the area of
the sunspot area being excited by the flare's EUV illumination. This
explanation is based on the obsevation that 1083 nm absorption in the
sunspot area gets enhanced during the flare. Nevertheless, questions are
still open and we need further well-devised observations to investigate
the behavior of sunspot dynamics during flares.
Title: Progress with multi-conjugate adaptive optics at the Big Bear
Solar Observatory
Authors: Schmidt, Dirk; Gorceix, Nicolas; Marino, Jose; Zhang, Xianyu;
Berkefeld, Thomas; Rimmele, Thomas R.; Goode, Philip R.
Bibcode: 2016SPD....47.0813S
Altcode:
The MCAO system at BBSO is the pathfinder system for a future system
at the 4-meter DKIST. It deploys three DMs, one in the pupil and two in
higher altitudes. The design allows to move the latter independently to
adapt to the turbulence profile within about 2-9 km.The optical path has
been improved in 2015, and has shown satisfying solar images. The MCAO
loop was able to improve the wavefront error across the field slightly
compared to classical AO.We will report on the latest improvements,
on-Sun results and motivate the design of the system.
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: Earth's albedo variations 1998-2014 as measured from
ground-based earthshine observations
Authors: Palle, E.; Goode, P. R.; Montañés-Rodríguez, P.; Shumko,
A.; Gonzalez-Merino, B.; Martinez-Lombilla, C.; Jimenez-Ibarra, F.;
Shumko, S.; Sanroma, E.; Hulist, A.; Miles-Paez, P.; Murgas, F.;
Nowak, G.; Koonin, S. E.
Bibcode: 2016GeoRL..43.4531P
Altcode: 2016arXiv160405880P
The Earth's albedo is a fundamental climate parameter for understanding
the radiation budget of the atmosphere. It has been traditionally
measured not only from space platforms but also from the ground for
16 years from Big Bear Solar Observatory by observing the Moon. The
photometric ratio of the dark (earthshine) to the bright (moonshine)
sides of the Moon is used to determine nightly anomalies in the
terrestrial albedo, with the aim of quantifying sustained monthly,
annual, and/or decadal changes. We find two modest decadal scale
cycles in the albedo, but with no significant net change over the 16
years of accumulated data. Within the evolution of the two cycles,
we find periods of sustained annual increases, followed by comparable
sustained decreases in albedo. The evolution of the earthshine albedo
is in remarkable agreement with that from the Clouds and the Earth's
Radiant Energy System instruments, although each method measures
different slices of the Earth's Bond albedo.
Title: Resolving the Fan-spine Reconnection Geometry of a Small-scale
Chromospheric Jet Event with the New Solar Telescope
Authors: Zeng, Zhicheng; Chen, Bin; Ji, Haisheng; Goode, Philip R.;
Cao, Wenda
Bibcode: 2016ApJ...819L...3Z
Altcode: 2016arXiv160204237Z
Jets are ubiquitously present in both quiet and active regions on the
Sun. They are widely believed to be driven by magnetic reconnection. A
fan-spine structure has been frequently reported in some coronal jets
and flares, and has been regarded as a signature of ongoing magnetic
reconnection in a topology consisting of a magnetic null connected by
a fan-like separatrix surface and a spine. However, for small-scale
chromospheric jets, clear evidence of such structures is rather
rare, although it has been implied in earlier works that showed an
inverted-Y-shaped feature. Here we report high-resolution (0.″16)
observations of a small-scale chromospheric jet obtained by the New
Solar Telescope (NST) using 10830 Å filtergrams. Bi-directional flows
were observed across the separatrix regions in the 10830 Å images,
suggesting that the jet was produced due to magnetic reconnection. At
the base of the jet, a fan-spine structure was clearly resolved by
the NST, including the spine and the fan-like surface, as well as the
loops before and after the reconnection. A major part of this fan-spine
structure, with the exception of its bright footpoints and part of the
base arc, was invisible in the extreme ultraviolet and soft X-ray images
(observed by the Atmosphere Imaging Assembly and the X-Ray Telescope,
respectively), indicating that the reconnection occurred in the upper
chromosphere. Our observations suggest that the evolution of this
chromospheric jet is consistent with a two-step reconnection scenario
proposed by Török et al.
Title: Simultaneous observations of Ellerman bombs by NST and IRIS
Authors: Kim, Y. H.; Yurchyshyn, V.; Cho, I. H.; Lee, J.; Park, Y. D.;
Yang, H.; Ahn, K.; Goode, P.
Bibcode: 2015AGUFMSH31B2413K
Altcode:
In this study, we present the simultaneous observations of Ellerman
bombs made by New Solar Telescope (NST) of Big Bear Solar Observatory
(BBSO) and Interface Region Imaging Spectrograph (IRIS) in space. The
data obtained during joint NST-IRIS observations on 30 and 31 in July
2014. We observed two representative events on both days. The first
one was a relatively weak Ellerman bomb occurred around 19:20 UT on
30 July 2014. IRIS observed this event by sit-and-stare mode thus we
analyzed high cadence spectral data and slit-jaw data simultaneously. We
found that this event was a hot explosion that occurred by magnetic
reconnection in the lower atmosphere of the Sun. The second event
was quite strong Ellerman bomb (20:20 UT on 31 July 2014) that is
well observed by NST FISS (Fast Imaging Solar Spectrograph), while
there was no IRIS spectral data. We had IRIS slit-jaw data only. The
Ellerman bomb was clearly coincident with the IRIS brightening at the
same location. Since the Ellerman bombs are usually believed to occur
in the photosphere with no coronal emission, it should be explained its
higher atmospheric emission in IRIS data. We will present the result
of simultaneous observations by IRIS and NST instruments and discuss
physical connection between Ellerman bombs and IRIS brightenings.
Title: Filtering the interaction matrix in an adaptive optics system
Authors: Zhang, Xianyu; Gorceix, Nicolas; Goode, Philip
Bibcode: 2015aoel.confE..30Z
Altcode:
No abstract at ADS
Title: Simultaneous observation of a hot explosion by NST and IRIS
Authors: Kim, Yeon-Han; Yurchyshyn, Vasyl; Bong, Su-Chan; Cho, Il-Hyun;
Cho, Kyung-Suk; Lee, Jaejin; Lim, Eun-Kyung; Park, Young-Deuk; Yang,
Heesu; Ahn, Kwangsu; Goode, Philip R.; Jang, Bi-Ho
Bibcode: 2015ApJ...810...38K
Altcode:
We present the first simultaneous observations of so-called “hot
explosions” in the cool atmosphere of the Sun made by the New Solar
Telescope (NST) of Big Bear Solar Observatory and the Interface Region
Imaging Spectrograph (IRIS) in space. The data were obtained during
the joint IRIS-NST observations on 2014 July 30. The explosion of
interest started around 19:20 UT and lasted for about 10 minutes. Our
findings are as follows: (1) the IRIS brightening was observed in
three channels of slit-jaw images, which cover the temperature range
from 4000 to 80,000 K; (2) during the brightening, the Si iv emission
profile showed a double-peaked shape with highly blue and redshifted
components (-40 and 80 km s-1) (3) wing brightening occurred
in Hα and Ca ii 8542 Å bands and related surges were observed in both
bands of the NST Fast Imaging Solar Spectrograph (FISS) instrument;
(4) the elongated granule, seen in NST TiO data, is clear evidence of
the emergence of positive flux to trigger the hot explosion; (5) the
brightening in Solar Dynamics Observatory/Atmospheric Imaging Assembly
1600 Å images is quite consistent with the IRIS brightening. These
observations suggest that our event is a hot explosion that occurred
in the cool atmosphere of the Sun. In addition, our event appeared as
an Ellerman bomb (EB) in the wing of Hα, although its intensity is
weak and the vertical extent of the brightening seems to be relatively
high compared with the typical EBs.
Title: Acoustic Waves Generated by Impulsive Disturbances in a
Gravitationally Stratified Medium
Authors: Chae, Jongchul; Goode, Philip R.
Bibcode: 2015ApJ...808..118C
Altcode:
Even though it is well-known from observations of the Sun that
three-minute period chromospheric oscillations persist in the
internetwork quiet regions and sunspot umbrae, until now their
origin and persistence has defied clear explanation. Here we provide
a clear and simple explanation for it with a demonstration of how
such oscillations at the chromosphere's cutoff frequency naturally
arise in a gravitationally stratified medium when it is disturbed. The
largest-wavenumber vertical components of a chromospheric disturbance
produce the highest-frequency wave packets, which propagate out of
the disturbed region at group speeds that are close to the sound
speed. Meanwhile, the smallest-wavenumber components develop into
wave packets of frequencies close to the acoustic cutoff frequency
that propagate at group speeds that are much lower than the sound
speed. Because of their low propagation speed, these low-frequency wave
packets linger in the disturbed region and nearby, and thus, are the
ones that an observer would identify as the persistent, chromospheric
three-minute oscillations. We emphasize that we can account for the
power of the persistent chromospheric oscillations as coming from the
repeated occurrence of disturbances with length scales greater than
twice the pressure scale height in the upper photosphere.
Title: The Earthshine Network: an update 1998-2013
Authors: Martínez-Lombilla, C.; Pallé, E.; Montañés-Rodríguez,
P.; Jiménez-Ibarra, F.; González-Merino, B.; Goode, P.; Shoumko,
A.; Miles-Páez, P.; Nowak, G.; Murgas, F.; Sanromá, E.; Shoumko, S.
Bibcode: 2015hsa8.conf..655M
Altcode:
The amount of energy coming into the Earth's climate system is
the combination of two parameters: solar constant, and Earth's
albedo (or reflectance). Our main goal in this work is to record an
absolutely-calibrated global albedo time series. The albedo can be
determined by alternative observations of the bright and dark sides of
the Moon. The bright side tells us the amount of sunlight received in
the Earth and the Moon. On the other hand, the dark side of the Moon --
called ``earthshine" or ``ashen light" -- provides information about
the global reflectance of the Earth. This is a long-term astronomical
study with an interdisciplinary approach, that contributes to increase
our knowledge about climate and cloud coverage at planetary scale. To
this end we are building a global network, with telescopes in different
locations around the world, in order to increase the precision of
our data. More telescopes means better time and spatial coverage of
the Earth. At this moment we have three stations in EEUU, Spain, and
Ukraine. In this work, we present the albedo's temporal variability in
the data that we have taken along the past fifteen years (1998--2013).
Title: Active Region Coronal Rain Event Observed by the Fast Imaging
Solar Spectrograph on the NST
Authors: Ahn, Kwangsu; Chae, Jongchul; Cho, Kyung-Suk; Song, Donguk;
Yang, Heesu; Goode, Philip R.; Cao, Wenda; Park, Hyungmin; Nah,
Jakyung; Jang, Bi-Ho; Park, Young-Deuk
Bibcode: 2014SoPh..289.4117A
Altcode: 2014SoPh..tmp...98A
The Fast Imaging Solar Spectrograph (FISS) is being operated on the New
Solar Telescope of the Big Bear Solar Observatory. It simultaneously
records spectra of Hα and Ca II 8542 Å lines, and this dual-spectra
measurement provides an estimate of the temperature and nonthermal
speed components. We observed a loop structure in AR 11305 using the
FISS, SDO/AIA, and STEREO/EUVI in 304 Å, and found plasma material
falling along the loop from a coronal height into the umbra of a
sunspot, which accelerated up to 80 km s−1. We also
observed C2 and C7 flare events near the loop. The temperature of the
downflows was in the range of 10 000 - 33 000 K, increasing toward
the umbra. The temperature of the flow varied with time, and the
temperature near the footpoint rose immediately after the C7 flare,
but the temperature toward the umbra remained the same. There seemed
to be a temporal correlation between the amount of downflow material
and the observed C-class flares. The downflows decreased gradually soon
after the flares and then increased after a few hours. These high-speed
red-shift events occurred continuously during the observations. The
flows observed on-disk in Hα and Ca II 8542 Å appeared as fragmented,
fuzzy condensed material falling from the coronal heights when seen
off-limb with STEREO/EUVI at 304 Å. Based on these observations,
we propose that these flows were an on-disk signature of coronal rain.
Title: AO-308: the high-order adaptive optics system at Big Bear
Solar Observatory
Authors: Shumko, Sergey; Gorceix, Nicolas; Choi, Seonghwan; Kellerer,
Aglaé; Cao, Wenda; Goode, Philip R.; Abramenko, Volodymyr; Richards,
Kit; Rimmele, Thomas R.; Marino, Jose
Bibcode: 2014SPIE.9148E..35S
Altcode:
In this paper we present Big Bear Solar Observatory's (BBSO) newest
adaptive optics system - AO-308. AO-308 is a result of collaboration
between BBSO and National Solar Observatory (NSO). AO-308 uses a 357
actuators deformable mirror (DM) from Xinetics and its wave front sensor
(WFS) has 308 sub-apertures. The WFS uses a Phantom V7.3 camera which
runs at 2000 Hz with the region of interest of 416×400 pixels. AO-308
utilizes digital signal processors (DSPs) for image processing. AO-308
has been successfully used during the 2013 observing season. The system
can correct up to 310 modes providing diffraction limited images at
all wavelengths of interest.
Title: Control and operation of the 1.6 m New Solar Telescope in
Big Bear
Authors: Varsik, J.; Plymate, C.; Goode, P.; Kosovichev, A.; Cao,
W.; Coulter, R.; Ahn, K.; Gorceix, N.; Shumko, S.
Bibcode: 2014SPIE.9147E..5DV
Altcode:
The 1.6m New Solar Telescope (NST) has developed a modern and
comprehensive suite of instruments which allow high resolution
observations of the Sun. The current instrument package comprises
diffraction limited imaging, spectroscopic and polarimetric instruments
covering the wavelength range from 0.4 to 5.0 microns. The instruments
include broadband imaging, visible and near-infrared scanning
Fabry-Perot interferometers, an imaging spectropolarimeter,
a fast visible-light imaging spectrograph, and a unique new
scanning cryogenic infrared spectrometer/spectropolarimeter
that is nearing completion. Most instruments are operated with
a 308 subaperture adaptive optics system, while the thermal-IR
spectrometer has a correlation tracker. This paper reports on the
current observational programs and operational performance of the
telescope and instrumentation. The current control, data processing,
and archiving systems are also briefly discussed.
Title: Optical design of the Big Bear Solar Observatory's
multi-conjugate adaptive optics system
Authors: Zhang, Xianyu; Gorceix, Nicolas; Schmidt, Dirk; Goode,
Philip R.; Cao, Wenda; Rimmele, Thomas R.; Coulter, Roy
Bibcode: 2014SPIE.9148E..50Z
Altcode:
A multi-conjugate adaptive optics (MCAO) system is being built for the
world's largest aperture 1.6m solar telescope, New Solar Telescope,
at the Big Bear Solar Observatory (BBSO). The BBSO MCAO system employs
three deformable mirrors to enlarge the corrected field of view. In
order to characterize the MCAO performance with different optical
configurations and DM conjugated altitudes, the BBSO MCAO setup also
needs to be flexible. In this paper, we present the optical design of
the BBSO MCAO system.
Title: New Vector Spectropolarimetry of Sunspots near 4000nm
Authors: Penn, Matthew J.; Coulter, Roy; Goode, Philip R.
Bibcode: 2014AAS...22411201P
Altcode:
Magnetic sensitivity of spectral lines increases as the product of the
wavelength and the Lande g-factor. While the most magnetically sensitive
spectral line known is the Mg I 12318nm line, and observations are often
made near 1600nm, little work has been done using solar spectral lines
near 4000nmWe report on new solar spectropolarimetric observations at
these wavelengths, made at the NSO McMath-Pierce facility with the NAC
and at the NJIT New Solar Telescope using CYRA. Several photospheric
absorption lines have been used to map a sunspot magnetic field,
and molecular line Zeeman splitting has also been observed. Several
"negative-g" molecular lines are seen, and an atomic line shows
unusual profiles.
Title: High Resolution Observations of Chromospheric Jets in
Sunspot Umbra
Authors: Yurchyshyn, Vasyl B.; Abramenko, Valentyna; Kosovichev,
Alexander G.; Goode, Philip R.
Bibcode: 2014AAS...22432301Y
Altcode:
Recent observations of sunspot's umbra suggested that it may be finely
structured at a sub-arcsecond scale representing a mix of hot and cool
plasma elements. In this study we report the first detailed observations
of the umbral spikes, which are cool jet-like structures seen in the
chromosphere of an umbra. The spikes are cone-shaped features with
a typical height of 0.5-1. Mm and a width of about 0. Mm. Their life
time ranges from 2 to 3 ~min and they tend to re-appear at the same
location. The preliminary analysis indicates that the spikes are not
associated with photospheric umbral dots and they rather tend to
occur above darkest parts of the umbra, where magnetic fields are
strongest. The spikes exhibit up and down oscillatory motions and
their spectral evolution suggests that they might be driven by upward
propagating shocks generated by photospheric oscillations. It is worth
noting that triggering of the running penumbral waves seems to occur
during the interval when the spikes reach their maximum height.
Title: High Resolution Observations of Chromospheric Jets in
Sunspot Umbra
Authors: Yurchyshyn, V.; Abramenko, V.; Kosovichev, A.; Goode, P.
Bibcode: 2014ApJ...787...58Y
Altcode: 2014arXiv1404.7444Y
Recent observations of a sunspot's umbra have suggested that it may
be finely structured on a subarcsecond scale representing a mix of hot
and cool plasma elements. In this study, we report the first detailed
observations of umbral spikes, which are cool jet-like structures seen
in the chromosphere of an umbra. The spikes are cone-shaped features
with a typical height of 0.5-1.0 Mm and a width of about 0.1 Mm. Their
lifetime ranges from 2 to 3 minutes and they tend to re-appear at
the same location. The spikes are not associated with photospheric
umbral dots and they instead tend to occur above the darkest parts of
the umbra where magnetic fields are strongest. The spikes exhibit up
and down oscillatory motions and their spectral evolution suggests
that they might be driven by upward propagating shocks generated by
photospheric oscillations. It is worth noting that triggering of the
running penumbral waves seems to occur during the interval when the
spikes reach their maximum height.
Title: Helioseismology in the 1980s and 1990s
Authors: Goode, Philip R.
Bibcode: 2014IAUS..301..117G
Altcode:
Over more than twenty years, Wojtek Dziembowski and I collaborated on
nearly fifty papers, which were concentrated in helioseismology through
the 1980s and 1990s, but extended early into the new century. In this
review, I discuss the most significant results of this collaboration
and some of the underlying sociology that contributed to the intensity
and longevity of our collaboration. Our work began with placing limits
on the Sun's buried magnetic field and ended with extracting from the
solar-cycle dependent oscillation frequency changes the roles (and net
result) of competing dynamical drivers of changes in the solar diameter.
Title: Concept for Solar Multi-Conjugate Adaptive Optics at Big
Bear Observatory
Authors: Langlois, Maud; Moretto, Gil; Béchet, Clémentine; Montilla,
Icíar; Tallon, Michel; Goode, Philip; Gorceix, Nicolas; Shumko, Sergey
Bibcode: 2013aoel.confE..62L
Altcode:
Solar observations are performed over an extended field of view and
the isoplanatic patch over which conventional adaptive optics (AO)
provides diffraction limited resolution is a severe limitation. The
development of multi-conjugate adaptive optics (MCAO) for the large
aperture solar telescopes ranging from 1.6 to 4 metres diameters is
extremely important. The Sun is an ideal object for the development
of MCAO since solar structure provides multiple "guide stars" in any
desired configuration. We propose a concept for a new MCAO system at
Big Bear Observatory. This MCAO system uses three deformable mirrors
conjugated to the telescope entrance pupil and to two layers in the
upper atmosphere. We present the detailed analysis of the performance
of this system for large range of elevations as required in solar
observations by using the Fractal Iterative Method (FrIM), which
incorporates wide field correlating Shack-Hartmann wavefront sensors.
Title: Optical Set-Up and Design for Solar Multi-conjugate Adaptive
Optics at the 1.6m New Solar Telescope, Big Bear Solar Observatory
Authors: Moretto, Gil; Langlois, Maud; Goode, Philip; Gorceix, Nicolas;
Shumko, Sergey
Bibcode: 2013aoel.confE..61M
Altcode:
The Sun is an ideal target for the development and application of
Multi-Conjugate Adaptive Optics (MCAO). A solar MCAO system is being
developed by the Big Bear Solar Observatory, for the 1.6m New Solar
Observatory, with the purpose of extending the corrected science field
of view to 1.00Arcmin. A preliminary optical set-up, design and optical
performance for such a system is presented and discussed here.
Title: Temperature of Solar Prominences Obtained with the Fast Imaging
Solar Spectrograph on the 1.6 m New Solar Telescope at the Big Bear
Solar Observatory
Authors: Park, Hyungmin; Chae, Jongchul; Song, Donguk; Maurya, Ram
Ajor; Yang, Heesu; Park, Young-Deuk; Jang, Bi-Ho; Nah, Jakyoung; Cho,
Kyung-Suk; Kim, Yeon-Han; Ahn, Kwangsu; Cao, Wenda; Goode, Philip R.
Bibcode: 2013SoPh..288..105P
Altcode:
We observed solar prominences with the Fast Imaging Solar Spectrograph
(FISS) at the Big Bear Solar Observatory on 30 June 2010 and 15 August
2011. To determine the temperature of the prominence material, we
applied a nonlinear least-squares fitting of the radiative transfer
model. From the Doppler broadening of the Hα and Ca II lines, we
determined the temperature and nonthermal velocity separately. The
ranges of temperature and nonthermal velocity were 4000 - 20 000 K and
4 - 11 km s−1. We also found that the temperature varied
much from point to point within one prominence.
Title: Velocities and Temperatures of an Ellerman Bomb and Its
Associated Features
Authors: Yang, Heesu; Chae, Jongchul; Lim, Eun-Kyung; Park, Hyungmin;
Cho, Kyuhyoun; Maurya, Ram Ajor; Song, Donguk; Kim, Yeon-Han; Goode,
Philip R.
Bibcode: 2013SoPh..288...39Y
Altcode:
We investigated the velocity and temperature characteristics of an
Ellerman bomb (EB) and its associated features based on observations
made with the Fast Imaging Solar Spectrograph (FISS) and a broadband
TiO filter of the 1.6 meter New Solar Telescope at Big Bear Solar
Observatory. In the TiO images of the photospheric level, we found a
granular cell expanding in two opposite directions near the site of the
EB. When one end of this granule reached the EB site, the transverse
speed of the tip of the expanding granule rapidly decreased and the EB
brightened. The wings of the Hα profile of the EB indicated that the
EB was blueshifted up to 7 km s−1. About 260 s after the EB
brightening, a surge was seen in absorption and varied from a blueshift
of 20 km s−1 to a redshift of 40 km s−1 seen
in the Hα and Ca II 8542 Å lines. From the Doppler absorption width
of the two lines determined by applying the cloud model, we estimated
the mean temperature of the surge material to be about 29000 K and the
mean speed of nonthermal motion to be about 11 km s−1. We
discuss the physical implications of our results in terms of magnetic
reconnection and processes related to it.
Title: Fast Imaging Solar Spectrograph of the 1.6 Meter New Solar
Telescope at Big Bear Solar Observatory
Authors: Chae, Jongchul; Park, Hyung-Min; Ahn, Kwangsu; Yang, Heesu;
Park, Young-Deuk; Nah, Jakyoung; Jang, Bi Ho; Cho, Kyung-Suk; Cao,
Wenda; Goode, Philip R.
Bibcode: 2013SoPh..288....1C
Altcode: 2012SoPh..tmp..248C
For high resolution spectral observations of the Sun - particularly
its chromosphere, we have developed a dual-band echelle spectrograph
named Fast Imaging Solar Spectrograph (FISS), and installed it in a
vertical optical table in the Coudé Lab of the 1.6 meter New Solar
Telescope at Big Bear Solar Observatory. This instrument can cover any
part of the visible and near-infrared spectrum, but it usually records
the Hα band and the Ca II 8542 Å band simultaneously using two CCD
cameras, producing data well suited for the study of the structure and
dynamics of the chromosphere and filaments/prominences. The instrument
does imaging of high quality using a fast scan of the slit across the
field of view with the aid of adaptive optics. We describe its design,
specifics, and performance as well as data processing
Title: Infrared Observations from the New Solar Telescope at Big Bear
Authors: Goode, Philip R.; Cao, Wenda
Bibcode: 2013SoPh..287..315G
Altcode:
The 1.6 m clear aperture solar telescope in Big Bear is operational and
with its adaptive optics (AO) system it provides diffraction limited
solar imaging and polarimetry in the near-infrared (NIR). While the AO
system is being upgraded to provide diffraction limited imaging at bluer
wavelengths, the instrumentation and observations are concentrated in
the NIR. The New Solar Telescope (NST) operates in campaigns, making it
the ideal ground-based telescope to provide complementary/supplementary
data to SDO and Hinode. The NST makes photometric observations in Hα
(656.3 nm) and TiO (705.6 nm) among other lines. As well, the NST
collects vector magnetograms in the 1565 nm lines and is beginning
such observations in 1083.0 nm. Here we discuss the relevant NST
instruments, including AO, and present some results that are germane
to NASA solar missions.
Title: Characteristic Length of Energy-containing Structures at the
Base of a Coronal Hole
Authors: Abramenko, V. I.; Zank, G. P.; Dosch, A.; Yurchyshyn, V. B.;
Goode, P. R.; Ahn, K.; Cao, W.
Bibcode: 2013ApJ...773..167A
Altcode: 2013arXiv1307.4421A
An essential parameter for models of coronal heating and fast solar
wind acceleration that rely on the dissipation of MHD turbulence is
the characteristic energy-containing length λ of the
squared velocity and magnetic field fluctuations (u 2
and b 2) transverse to the mean magnetic field inside a
coronal hole (CH) at the base of the corona. The characteristic length
scale directly defines the heating rate. We use a time series analysis
of solar granulation and magnetic field measurements inside two CHs
obtained with the New Solar Telescope at Big Bear Solar Observatory. A
data set for transverse magnetic fields obtained with the Solar Optical
Telescope/Spectro-Polarimeter on board the Hinode spacecraft was
utilized to analyze the squared transverse magnetic field fluctuations
b_t^2. Local correlation tracking was applied to derive the squared
transverse velocity fluctuations u 2. We find that for u
2 structures, the Batchelor integral scale λ varies in
a range of 1800-2100 km, whereas the correlation length sigmav and
the e-folding length L vary between 660 and 1460 km. Structures for
b_t^2 yield λ ≈ 1600 km, sigmav ≈ 640 km, and L ≈ 620 km. An
averaged (over λ, sigmav, and L) value of the characteristic length
of u 2 fluctuations is 1260 ± 500 km, and that of b_t^2
is 950 ± 560 km. The characteristic length scale in the photosphere
is approximately 1.5-50 times smaller than that adopted in previous
models (3-30 × 103 km). Our results provide a critical
input parameter for current models of coronal heating and should yield
an improved understanding of fast solar wind acceleration.
Title: The New Solar Telescope (NST): What’s Next ?
Authors: Cao, Wenda; Goode, P. R.; NST Team
Bibcode: 2013SPD....4440006C
Altcode:
The 1.6 m, off-axis, clear aperture New Solar Telescope (NST) has been
in regular operation in Big Bear Solar Observatory since 2009. The
NST is the first facility class solar telescope built in the U.S. in
a generation, which already offers a significant improvement in
ground-based high angular resolution capabilities. This presentation
reports the up-to-date progress on the NST and its 2nd generation
instruments including the AO system (AO-308), the Near-InfraRed Imaging
Spectro-polarimeter (NIRIS), the Visible Imaging Spectrometer (VIS),
and the Cryogenic Infrared Spectrograph (CYRA).
Title: Observation of a Non-radial Penumbra in a Flux Emerging Region
under Chromospheric Canopy Fields
Authors: Lim, Eun-Kyung; Yurchyshyn, Vasyl; Goode, Philip; Cho,
Kyung-Suk
Bibcode: 2013ApJ...769L..18L
Altcode:
The presence of a penumbra is one of the main properties of a mature
sunspot, but its formation mechanism has been elusive due to a lack
of observations that fully cover the formation process. Utilizing the
New Solar Telescope at the Big Bear Solar Observatory, we observed
the formation of a partial penumbra for about 7 hr simultaneously at
the photospheric (TiO; 7057 Å) and the chromospheric (Hα - 1 Å)
spectral lines with high spatial and temporal resolution. From this
uninterrupted, long observing sequence, we found that the formation of
the observed penumbra was closely associated with flux emergence under
the pre-existing chromospheric canopy fields. Based on this finding,
we suggest a possible scenario for penumbra formation in which a
penumbra forms when the emerging flux is constrained from continuing
to emerge, but rather is trapped at the photospheric level by the
overlying chromospheric canopy fields.
Title: Dynamics of Chromospheric Upflows and Underlying Magnetic
Fields
Authors: Yurchyshyn, V.; Abramenko, V.; Goode, P.
Bibcode: 2013ApJ...767...17Y
Altcode: 2013arXiv1303.4766Y
We used Hα-0.1 nm and magnetic field (at 1.56μ) data obtained with
the New Solar Telescope to study the origin of the disk counterparts to
type II spicules, so-called rapid blueshifted excursions (RBEs). The
high time cadence of our chromospheric (10 s) and magnetic field
(45 s) data allowed us to generate x-t plots using slits parallel
to the spines of the RBEs. These plots, along with potential field
extrapolation, led us to suggest that the occurrence of RBEs is
generally correlated with the appearance of new, mixed, or unipolar
fields in close proximity to network fields. RBEs show a tendency
to occur at the interface between large-scale fields and small-scale
dynamic magnetic loops and thus are likely to be associated with the
existence of a magnetic canopy. Detection of kinked and/or inverse
"Y"-shaped RBEs further confirm this conclusion.
Title: NIRIS: The Second Generation Near-Infrared Imaging
Spectro-polarimeter for the 1.6 Meter New Solar Telescope
Authors: Cao, W.; Goode, P. R.; Ahn, K.; Gorceix, N.; Schmidt, W.;
Lin, H.
Bibcode: 2012ASPC..463..291C
Altcode:
The largest aperture solar telescope, the 1.6 m New Solar Telescope
(NST) has been installed at the Big Bear Solar Observatory
(BBSO). To take full advantage of the NST's greatest potential, we
are upgrading the routinely operational InfraRed Imaging Magnetograph
(IRIM) to its second generation, the NIRIS (Near-InfraRed Imaging
Spectropolarimeter). NIRIS will offer unprecedented high resolution
spectroscopic and polarimetric imaging data of the solar atmosphere
from the deepest photosphere through the base of the corona. With the
aid of the BBSO adaptive optics (AO) system, the spatial resolution
will be close to the diffraction limit of the NST. The spectroscopic
cadence will reach one second, while polarimetric measurements,
including Stokes I, Q, U, V profiles, remain at a better than 10
s cadence. Polarization sensitivity is expected to be reach ∼
10-4Ic. NIRIS will cover a broad spectral
range from 1.0 to 1.7μm, with particular attention to two unique
spectral lines: the Fe I 1565 nm doublet has already proven to be
the most sensitive to Zeeman effect for probing the magnetic field
in the deepest photosphere; the He I 1083 nm multiplet is one of the
best currently available diagnostic of upper chromospheric magnetic
fields that allows one to map the vector field at the base of the
corona. NIRIS will be built on dual Fabry-Pérot Interferometers (FPIs),
each of which has an aperture of 100 mm. The larger aperture of FPIs
allows the available field-of-view up to one and half minutes with a
spectral power of ∼ 105.
Title: The 1.6 m Off-Axis New Solar Telescope (NST) in Big Bear
Authors: Goode, P. R.; Cao, W.
Bibcode: 2012ASPC..463..357G
Altcode:
The New Solar Telescope (NST) in Big Bear is the first facility-class
solar telescope built in the US in a generation, and it has an
off-axis design as is planned for the Advanced Technology Solar
Telescope (ATST). The NST is in regular operation with adaptive optics
(AO) correcting the light currently feeding photometric and near-IR
polarimetric systems, as well as an imaging spectrograph. Here we show
the high resolution capabilities of the NST. As well, we sketch our
plans for, and reasoning behind the next generation NST instrumentation.
Title: Construction of the Advanced Technology Solar Telescope -
A Progress Report.
Authors: Rimmele, T. R.; Keil, S.; McMullin, J.; Goode, P. R.;
Knoelker, M.; Kuhn, J. R.; Rosner, R.; ATST Team
Bibcode: 2012IAUSS...6E.206R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) will be the most
powerful solar telescope and the world's leading ground-based resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun's output. The ATST
will provide high resolution and high sensitivity observations of the
dynamic solar magnetic fields throughout the solar atmosphere, including
the corona at infrared wavelengths. With its 4 m aperture, ATST will
resolve magnetic features at their intrinsic scales. A high order
adaptive optics system delivers a corrected beam to the initial set of
five state-of-the-art, facility class instrumentation located in the
coude laboratory facility. Photopheric and chromospheric magnetometry
is part of the key mission of four of these instruments. Coronal
magnetometry and spectroscopy will be performed by two of these
instruments at infrared wavelengths. The ATST project has transitioned
from design and development to its construction phase. Site construction
is expected to begin in the first half of 2012. The project has awarded
design and fabrication contracts for major telescope subsystems. A
robust instrument program has been established and all instruments
have passed preliminary design reviews or critical design reviews. A
brief summary of the science goals and observational requirements of
the ATST will be given, followed by a summary of the project status of
the telescope and discussion of the approach to integrating instruments
into the facility.
Title: Investigation of Small-Scale Turbulent MHD Phenomena Using
Numerical Simulations and NST Observations
Authors: Kitiashvili, I.; Abramenko, V.; Goode, P. R.; Kosovichev,
A.; Mansour, N.; Wray, A.; Yurchyshyn, V.
Bibcode: 2012IAUSS...6E.104K
Altcode:
Recent progress in observational capabilities and numerical modeling
have provided unique high-resolution information demonstrating
complicated dynamics and structures of turbulent flows and magnetic
field on the Sun. The realistic approach to numerical simulations is
based on physical first principles and takes into account compressible
fluid flow in a highly stratified magnetized medium, 3D multi-bin
radiative energy transfer between fluid elements, a real-gas equation
of state, ionization, and excitation of all abundant species, magnetic
effects and sub-grid turbulence. We present new results of 3D radiative
MHD simulations of the upper solar convection zone and chromosphere
that reveal a fundamental role of small-scale vortex dynamics, and
compare the numerical results and predictions with observational
results from the 1.6 m clear aperture New Solar Telescope (NST) at
Big Bear Observatory. In particular, we investigate formation and
dynamics of ubiquitous small-scale vortex tubes mostly concentrated
in the intergranular lanes and their role in magnetic structuring
and acoustic emission of the Sun. These whirlpool-like flows are
characterized by very strong horizontal shear velocities (7 - 11 km/s)
and downflows (~7 km/s), and are accompanied by sharp decreases in
temperature, density and pressure at the surface. High-speed whirlpool
flows can attract and capture other vortices, penetrate into the low
chromosphere, and form stable magnetic flux tubes. The simulations also
reveal a strong connection between acoustic wave excitation events and
the dynamics of vortex tubes. In this talk, we will discuss different
aspects of small-scale turbulent dynamics of the low atmosphere from the
high-resolution simulations in comparison with recent NST observations,
and the strategy for future synergies of numerical simulations and
observations with large aperture solar telescopes.
Title: Energy-Containing Length Scale at the Base of a Coronal Hole:
New Observational Findings
Authors: Abramenko, V.; Dosch, A.; Zank, G. P.; Yurchyshyn, V.; Goode,
P. R.
Bibcode: 2012AGUFMSH33D2253A
Altcode:
Dynamics of the photospheric flux tubes is thought to be a key
factor for generation and propagation of MHD waves and magnetic
stress into the corona. Recently, New Solar Telescope (NST, Big
Bear Solar Observatory) imaging observations in helium I 10830 Å
revealed ultrafine, hot magnetic loops reaching from the photosphere
to the corona and originating from intense, compact magnetic field
elements. One of the essential input parameters to run the models of
the fast solar wind is a characteristic energy-containing length scale,
lambda, of the dynamical structures transverse to the mean magnetic
field in a coronal hole (CH) in the base of the corona. We used NST
time series of solar granulation motions to estimate the velocity
fluctuations, as well as NST near-infrared magnetograms to derive
the magnetic field fluctuations. The NST adaptive optics corrected
speckle-reconstructed images of 10 seconds cadence were an input for the
local correlation tracking (LCT) code to derive the squared transverse
velocity patterns. We found that the characteristic length scale for
the energy-carrying structures in the photosphere is about 300 km,
which is two orders of magnitude lower than it was adopted in previous
models. The influence of the result on the coronal heating and fast
solar wind modeling will be discussed.; Correlation functions calculated
from the squared velocities for the three data sets: a coronal hole,
quiet sun and active region plage area.
Title: Construction of the Advanced Technology Solar Telescope
Authors: Rimmele, T. R.; Keil, S.; McMullin, J.; Knölker, M.; Kuhn,
J. R.; Goode, P. R.; Rosner, R.; Casini, R.; Lin, H.; Tritschler,
A.; Wöger, F.; ATST Team
Bibcode: 2012ASPC..463..377R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) will be the most
powerful solar telescope and the world's leading ground-based resource
for studying solar magnetism that controls the solar wind, flares,
coronal mass ejections and variability in the Sun's output. The
project has entered its construction phase. Major subsystems have
been contracted. As its highest priority science driver ATST shall
provide high resolution and high sensitivity observations of the
dynamic solar magnetic fields throughout the solar atmosphere,
including the corona at infrared wavelengths. With its 4m aperture,
ATST will resolve features at 0.″03 at visible wavelengths and
obtain 0.″1 resolution at the magnetically highly sensitive near
infrared wavelengths. A high order adaptive optics system delivers a
corrected beam to the initial set of state-of-the-art, facility class
instrumentation located in the Coudé laboratory facility. The initial
set of first generation instruments consists of five facility class
instruments, including imagers and spectro-polarimeters. The high
polarimetric sensitivity and accuracy required for measurements of
the illusive solar magnetic fields place strong constraints on the
polarization analysis and calibration. Development and construction
of a four-meter solar telescope presents many technical challenges,
including thermal control of the enclosure, telescope structure and
optics and wavefront control. A brief overview of the science goals
and observational requirements of the ATST will be given, followed by a
summary of the design status of the telescope and its instrumentation,
including design status of major subsystems, such as the telescope
mount assembly, enclosure, mirror assemblies, and wavefront correction
Title: 2nd ATST-EAST Workshop in Solar Physics: Magnetic Fields from
the Photosphere to the Corona
Authors: Rimmele, T. R.; Tritschler, A.; Wöger, F.; Collados Vera,
M.; Socas-Navarro, H.; Schlichenmaier, R.; Carlsson, M.; Berger, T.;
Cadavid, A.; Gilbert, P. R.; Goode, P. R.; Knölker, M.
Bibcode: 2012ASPC..463.....R
Altcode:
No abstract at ADS
Title: The relationship between the occurrence of type II spicules
and the dynamics of underlying magnetic fields
Authors: Yurchyshyn, V.; Abramenko, V.; Goode, P. R.
Bibcode: 2012AGUFMSH32A..05Y
Altcode:
Type II spicules are thought to be small-scale chromospheric
up-flows. When observed against the solar disk they can be identified
as rapid blue shifted events (or excursions, RBE, Rouppe van der
Voort et al.). While their nature is being questioned and their
associated driving mechanism remains elusive, these up-flows may be
instrumental in the processes of coronal heating and solar wind. We use
high resolution photospheric, chromospheric and magnetic field data
from the New Solar Telescope operating at Big Bear Solar Observatory
to further determine the properties of these events and refine the
role that they may play. We find that the majority of RBEs, occurring
around network clusters of bright points, can be linked to episodes
of small flux emergence, in particular appearance of opposite polarity
fields. Case studies further indicate that some of the RBEs appear to
have kink and inverted "Y" shaped roots. The data thus suggest that
magnetic reconnection may be responsible for at least some fraction
of observed RBEs. We will present these observations in details and
discuss possible implications.Sequence of H-alpha-0.075nm images
spanning 7 min showing evolution of RBE activity near a cluster
of network fields. The two yellow circles enclose the area where
multipolar fields rapidly appeared. Comparing panels 19:05:11 UT and
19:05:55 UT one may notice that a new magnetic dipole and a dark jet
appeared in the encircled area. The same is true about the encircled
area in 19:07:26UT panel. The RBE activity ceased as soon as the the
field of view was cleared from small-scale magnetic elements.
Title: Turbulent Pair Dispersion of Photospheric Bright Points
Authors: Lepreti, F.; Carbone, V.; Abramenko, V. I.; Yurchyshyn, V.;
Goode, P. R.; Capparelli, V.; Vecchio, A.
Bibcode: 2012ApJ...759L..17L
Altcode:
Observations of solar granulation obtained with the New Solar Telescope
of Big Bear Solar Observatory are used to study the turbulent pair
dispersion of photospheric bright points in a quiet-Sun area, a
coronal hole, and an active region plage. In all the three magnetic
environments, it is found that the pair mean-squared separation
Δ2(t) follows a power-law timescaling Δ2(t) ~ t
η in the range 10 s <~ t <~ 400 s. The power-law index
is found to be η ~= 1.5 for all the three investigated regions. It
is shown that these results can be explained in the same framework as
the classical Batchelor theory, under the hypothesis that the observed
range of timescales corresponds to a non-asymptotic regime in which the
photospheric bright points keep the memory of their initial separations.
Title: The 1.6 m off-axis New Solar Telescope (NST) in Big Bear
Authors: Goode, Philip R.; Cao, Wenda
Bibcode: 2012SPIE.8444E..03G
Altcode:
The 1.6-m New Solar Telescope (NST) has been used to observe the Sun
for more than three years with ever increasing capabilities as its
commissioning phase winds down. The NST is the first facility-class
solar telescope built in the U.S. in a generation, and it has
an off-axis design as is planned for the 4 m Advanced Technology
Solar Telescope. Lessons learned will be discussed. Current NST
post-focus instrumentation includes adaptive optics (AO) feeding
photometric and near-IR polarimetric sytems, as well as an imaging
spectrograph. On-going instrumentation projects will be sketched,
including Multi-Conjugate AO (MCAO), next generation (dual Fabry-
Perot) visible light and near-IR polarimeters and a fully cryogenic
spectrograph. Finally, recent observational results illustrating the
high resolution capabilities of the NST will be shown.
Title: Detection of Small-scale Granular Structures in the Quiet
Sun with the New Solar Telescope
Authors: Abramenko, V. I.; Yurchyshyn, V. B.; Goode, P. R.;
Kitiashvili, I. N.; Kosovichev, A. G.
Bibcode: 2012ApJ...756L..27A
Altcode: 2012arXiv1208.4337A
Results of a statistical analysis of solar granulation are presented. A
data set of 36 images of a quiet-Sun area on the solar disk center was
used. The data were obtained with the 1.6 m clear aperture New Solar
Telescope at Big Bear Solar Observatory and with a broadband filter
centered at the TiO (705.7 nm) spectral line. The very high spatial
resolution of the data (diffraction limit of 77 km and pixel scale of
0farcs0375) augmented by the very high image contrast (15.5% ± 0.6%)
allowed us to detect for the first time a distinct subpopulation of
mini-granular structures. These structures are dominant on spatial
scales below 600 km. Their size is distributed as a power law with an
index of -1.8 (which is close to the Kolmogorov's -5/3 law) and no
predominant scale. The regular granules display a Gaussian (normal)
size distribution with a mean diameter of 1050 km. Mini-granular
structures contribute significantly to the total granular area. They are
predominantly confined to the wide dark lanes between regular granules
and often form chains and clusters, but different from magnetic bright
points. A multi-fractality test reveals that the structures smaller
than 600 km represent a multi-fractal, whereas on larger scales the
granulation pattern shows no multi-fractality and can be considered
as a Gaussian random field. The origin, properties, and role of the
population of mini-granular structures in the solar magnetoconvection
are yet to be explored.
Title: First Simultaneous Detection of Moving Magnetic Features in
Photospheric Intensity and Magnetic Field Data
Authors: Lim, Eun-Kyung; Yurchyshyn, Vasyl; Goode, Philip
Bibcode: 2012ApJ...753...89L
Altcode: 2012arXiv1205.0574L
The formation and the temporal evolution of a bipolar moving magnetic
feature (MMF) was studied with high-spatial and temporal resolution. The
photometric properties were observed with the New Solar Telescope at
Big Bear Solar Observatory using a broadband TiO filter (705.7 nm),
while the magnetic field was analyzed using the spectropolarimetric
data obtained by Hinode. For the first time, we observed a bipolar
MMF simultaneously in intensity images and magnetic field data, and
studied the details of its structure. The vector magnetic field and the
Doppler velocity of the MMF were also studied. A bipolar MMF with its
positive polarity closer to the negative penumbra formed, accompanied by
a bright, filamentary structure in the TiO data connecting the MMF and
a dark penumbral filament. A fast downflow (<=2 km s-1)
was detected at the positive polarity. The vector magnetic field
obtained from the full Stokes inversion revealed that a bipolar MMF
has a U-shaped magnetic field configuration. Our observations provide
a clear intensity counterpart of the observed MMF in the photosphere,
and strong evidence of the connection between the MMF and the penumbral
filament as a serpentine field.
Title: Small Scale Field Emergence and Its Impact on Photospheric
Granulation
Authors: Yurchyshyn, V.; Ahn, K.; Abramenko, V.; Goode, P.; Cao, W.
Bibcode: 2012arXiv1207.6418Y
Altcode:
We used photospheric intensity images and magnetic field measurements
from the New Solar Telescope in Big Bear and Helioseismic Magnetic
Imager on board Solar Dynamics Observatory (SDO) to study the the effect
that the new small-scale emerging flux induces on solar granulation. We
report that emerging flux appears to leave different types of footprint
on solar granulation: i) diffuse irregular patches of increased
brightness, ii) well defined filament-like structures and accompanied
bright points, and iii) bright point-like features that appear inside
granules. We suggest that the type of the footprint depends on the
intensity of emerging fields. Stronger fields, emerging as a part of
large magnetic structure, create on the solar surface a well defined
filamentary pattern with bright points at the ends of the filaments,
while weak turbulent fields are associated with bright patches inside
the host granule.
Title: New solar telescope in Big Bear: evidence for super-diffusivity
and small-scale solar dynamos?
Authors: Goode, Philip R.; Abramenko, Valentyna; Yurchyshyn, Vasyl
Bibcode: 2012PhyS...86a8402G
Altcode:
The 1.6 m clear aperture New Solar Telescope (NST) in Big Bear Solar
Observatory (BBSO) is now providing the highest resolution solar data
ever. These data have revealed surprises about the Sun on small-scales
including the observation that bright points (BPs), which can be
used as proxies for the intense, compact magnetic elements that are
apparent in photospheric intergranular lanes. The BPs are ever more
numerous on ever smaller spatial scales as though there were no limit
to how small the BPs can be. Here we discuss high resolution NST data
on BPs that provide support for the ideas that a turbulent regime
of super-diffusivity dominates in the quiet Sun, and there are local
dynamos operating near the solar surface.
Title: Profiles of the daytime atmospheric turbulence above Big Bear
solar observatory
Authors: Kellerer, A.; Gorceix, N.; Marino, J.; Cao, W.; Goode, P. R.
Bibcode: 2012A&A...542A...2K
Altcode:
Context. Space weather has become acutely critical for today's
global communication networks. To understand its driving forces we
need to observe the Sun with high angular-resolution, and within
large fields-of-view, i.e. with multi-conjugate adaptive optics
correction.
Aims: The design of a multi-conjugate adaptive
optical system requires the knowledge of the altitude distribution of
atmospheric turbulence. We have therefore measured daytime turbulence
profiles above the New Solar Telescope (NST), on Big Bear Lake.
Methods: To this purpose, a wide-field wavefront sensor was installed
behind the NST. The variation of the wavefront distortions with
angular direction allows the reconstruction of the distribution of
turbulence.
Results: The turbulence is found to have three
origins: 1. a ground layer (<500 m) that contains 55-65% of the
turbulence, 2. a boundary layer between 1-7 km comprises 30-40% of
the turbulent energy, 3. and the remaining ~5% are generated in the
tropopause, which is above 12 km in summer and between 8 and 12 km in
winter.
Conclusions: A multi-conjugate adaptive optical system
should thus aim at correcting the ground turbulence, the center of
the boundary layer at roughly 3 km altitude and, eventually, the upper
boundary layer around 6 km altitude.
Title: Turbulent Kinetic Energy Spectra of Solar Convection from
NST Observations and Realistic MHD Simulations
Authors: Kitiashvili, I. N.; Abramenko, V. I.; Goode, P. R.;
Kosovichev, A. G.; Lele, S. K.; Mansour, N. N.; Wray, A. A.;
Yurchyshyn, V. B.
Bibcode: 2012arXiv1206.5300K
Altcode:
Turbulent properties of the quiet Sun represent the basic state of
surface conditions, and a background for various processes of solar
activity. Therefore understanding of properties and dynamics of this
`basic' state is important for investigation of more complex phenomena,
formation and development of observed phenomena in the photosphere and
atmosphere. For characterization of the turbulent properties we compare
kinetic energy spectra on granular and sub-granular scales obtained
from infrared TiO observations with the New Solar Telescope (Big Bear
Solar Observatory) and from 3D radiative MHD numerical simulations
('SolarBox' code). We find that the numerical simulations require a high
spatial resolution with 10 - 25 km grid-step in order to reproduce the
inertial (Kolmogorov) turbulence range. The observational data require
an averaging procedure to remove noise and potential instrumental
artifacts. The resulting kinetic energy spectra show a good agreement
between the simulations and observations, opening new perspectives for
detailed joint analysis of more complex turbulent phenomena on the Sun,
and possibly on other stars. In addition, using the simulations and
observations we investigate effects of background magnetic field,
which is concentrated in self-organized complicated structures in
intergranular lanes, and find an increase of the small-scale turbulence
energy and its decrease at larger scales due to magnetic field effects.
Title: Advanced Technology Solar Telescope Construction: Progress
Report
Authors: Rimmele, Thomas R.; McMullin, J.; Keil, S.; Goode, P.;
Knoelker, M.; Kuhn, J.; Rosner, R.; ATST Team
Bibcode: 2012AAS...22012202R
Altcode:
The 4m Advance Technology Solar Telescope (ATST) on Haleakala will be
the most powerful solar telescope and the world’s leading ground-based
resource for studying solar magnetism that controls the solar wind,
flares, coronal mass ejections and variability in the Sun’s
output. The ATST will provide high resolution and high sensitivity
observations of the dynamic solar magnetic fields throughout the solar
atmosphere, including the corona at infrared wavelengths. With its 4
m aperture, ATST will resolve magnetic features at their intrinsic
scales. A high order adaptive optics system delivers a corrected
beam to the initial set of five state-of-the-art, facility class
instrumentation located in the coude laboratory facility. Photopheric
and chromospheric magnetometry is part of the key mission of four
of these instruments. Coronal magnetometry and spectroscopy will be
performed by two of these instruments at infrared wavelengths. The
ATST project has transitioned from design and development to its
construction phase. Site construction is expected to begin in April
2012. The project has awarded design and fabrication contracts for major
telescope subsystems. A robust instrument program has been established
and all instruments have passed preliminary design reviews or critical
design reviews. A brief overview of the science goals and observational
requirements of the ATST will be given, followed by a summary of the
project status of the telescope and discussion of the approach to
integrating instruments into the facility. The National Science
Foundation (NSF) through the National Solar Observatory (NSO) funds
the ATST Project. The NSO is operated under a cooperative agreement
between the Association of Universities for Research in Astronomy,
Inc. (AURA) and NSF.
Title: Observation of Ultrafine Channels of Solar Corona Heating
Authors: Ji, Haisheng; Cao, Wenda; Goode, Philip R.
Bibcode: 2012ApJ...750L..25J
Altcode:
We report the first direct observations of dynamical events
originating in the Sun's photosphere and subsequently lighting up the
corona. Continuous small-scale, impulsive events have been tracked from
their origin in the photosphere on through to their brightening of the
local corona. We achieve this by combining high-resolution ground-based
data from the 1.6 m aperture New Solar Telescope (NST) at Big Bear Solar
Observatory (BBSO), and satellite data from the Atmospheric Imaging
Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The
NST imaging observations in helium I 10830 Å reveal unexpected
complexes of ultrafine, hot magnetic loops seen to be reaching from the
photosphere to the base of the corona. Most of these ultrafine loops
are characterized by an apparently constant, but surprisingly narrow
diameter of about 100 km all along each loop, and the loops originate
on the solar surface from intense, compact magnetic field elements. The
NST observations detect the signature of upward injections of hot plasma
that excite the ultrafine loops from the photosphere to the base of the
corona. The ejecta have their individual footpoints in the intergranular
lanes between the Sun's ubiquitous, convectively driven granules. In
many cases, AIA/SDO detects cospatial and cotemporal brightenings
in the overlying, million degree coronal loops in conjunction with
the upward injections along the ultrafine loops. Segments of some
of the more intense upward injections are seen as rapid blueshifted
events in simultaneous Hα blue wing images observed at BBSO. In sum,
the observations unambiguously show impulsive coronal heating events
from upward energy flows originating from intergranular lanes on the
solar surface accompanied by cospatial mass flows.
Title: Direct Observation of the Intensity Counterpart of Moving
Magnetic Features on the Photosphere and the Corresponding Vector
Magnetic Fields
Authors: Lim, Eunkyung; Yurchyshyn, V.; Goode, P.
Bibcode: 2012AAS...22020622L
Altcode:
The formation and the temporal evolution of a bipolar moving magnetic
feature (MMF) was studied with high spatio-temporal resolution. The
photometric properties were observed with the New Solar Telescope at
Big Bear Solar Observatory using a broadband TiO filter at 705.7nm,
while the magnetic field was analyzed using the Spectropolarimetric
data obtained by Hinode/SOT. From our high resolution, multi-wavelength
observation, we studied 1) the detailed structure of the intensity
counterpart in the photosphere of a bipolar MMF, 2) the vector magnetic
field and the Doppler velocity of the MMF in time. A bipolar MMF
having its positive polarity closer to the negative penumbra formed
being accompanied by a bright, filamentary structure in the TiO line
connecting the MMF and a dark penumbral filament. A fast downflow
was detected in the positive polarity region, where the filamentary
structure is seen to be brighter than its surroundings. The vector
magnetic field obtained from the full Stokes inversion reveals a
developing U-shaped magnetic dip between the poles of the bipolar
MMF. Our observations provide the most clear intensity counterpart
in the photosphere to the observed MMF, and strong evidence of the
connection between the MMF and the local penumbral filament as a
serpentine field.
Title: Calibration of data from InfraRed Imaging Magnetograph for
the New Solar Telescope
Authors: Ahn, Kwangsu; Cao, W.; Gorceix, N.; Goode, P. R.
Bibcode: 2012AAS...22020616A
Altcode:
The InfraRed Imaging Magnetograph (IRIM) takes advantage of the
high spatial resolution of New Solar Telescope (NST). It adopts a
rotating birefringent polymer to modulate polarization signals and
two Wollaston prisms as analyzer. Dual beam setup is used to minimize
the effect of image motion caused by seeing. Its field of view is 50"
x 25" and the wavelengths of operation are Fe I 15648 A and He I 10830
A. Due to the off-axis shape of the NST primary and secondary mirrors,
multiple calibration techniques should be combined to reconstruct the
original Stokes parameters. Here, we would like to introduce current
status of our calibration efforts and discuss how IRIM data can be
used for scientific purposes.
Title: Observational Signatures of the Small-Scale Dynamo in the
Quiet Sun
Authors: Abramenko, V.; Yurchyshyn, V.; Goode, P. R.
Bibcode: 2012ASPC..455...17A
Altcode:
The generation and diffusion of the magnetic field on the Sun is a key
mechanism responsible for solar activity on all spatial and temporal
scales—from the solar cycle down to the evolution of small-scale
magnetic elements in the quiet Sun. The solar dynamo operates as
a non-linear dynamical process and is thought to be manifest in two
types: as a global dynamo responsible for the solar cycle periodicity,
and as a small-scale turbulent dynamo responsible for the formation
of the magnetic carpet in the quiet Sun. Numerous MHD simulations of
solar turbulence did not yet reach a consensus as to the existence
of a turbulent dynamo on the Sun. At the same time, high-resolution
observations of the quiet Sun from Hinode instruments suggest
possibilities for the turbulent dynamo. Analysis of characteristics of
turbulence derived from observations would be beneficial in tackling
the problem. We analyze magnetic and velocity energy spectra as derived
from Hinode/SOT, SOHO/MDI, SDO/HMI and the New Solar Telescope (NST)
of Big Bear Solar Observatory (BBSO) to explore the possibilities for
the small-scale turbulent dynamo in the quiet Sun.
Title: Origin of Rapid Blueshifted Events in Coronal Holes
Authors: Yurchyshyn, Vasyl B.; Ahn, K.; Abramenko, V.; Goode, P.;
Cao, W.
Bibcode: 2012AAS...22042304Y
Altcode:
Clusters of photospheric bright points are surrounded by chromospheric
rosette-like structures. These rosettes, when observed in the far
off-band (-0.1nm) Halpha images often appear to consist of short living,
narrow rapid blueshifted events (RBEs). RBEs, in turn, are thought to
be disk counterparts of type II spicules (spicules II), detected in
Hinode data, which may be playing play an important role in coronal
heating since they are thought to supply mass to the solar corona. The
search for the origin of type II spicules was one of the main focus of
solar physics research in the recent years. Here we present our
findings on the possible driving mechanism of spicules II, which are
based on high resolution photospheric, chromospheric and magnetic field
data from the New Solar Telescope (NST) collected in a coronal hole. We
report that the majority of RBEs, occurring around a network cluster,
are associated with appearance of opposite polarity features within
the unipolar cluster fields, suggesting that magnetic reconnection
may be the driving mechanism. We will present these observations in
details and discuss possible implications.
Title: Observation of Hyperfine Channels of Solar Corona Heating
Authors: Cao, Wenda; Ji, H.; Goode, P. R.
Bibcode: 2012AAS...22042301C
Altcode:
We report here the first direct observations of dynamical events
originating in the sun’s cool photosphere and subsequently lighting
up the corona. Continuous impulsive events have been tracked from
their origin in the photosphere on through to their brightening
of the local corona. We achieve this by combining high resolution
ground-based data from the 1.6 meter aperture New Solar Telescope
(NST) at Big Bear Solar Observatory (BBSO),and satellite data from
the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics
Observatory (SDO). The NST observations in a narrow band absorption
line, Helium I 10830 Å, reveal unexpected complexes of hyperfine,
hot magnetic loops seen to be reaching from the photosphere to the
base of the corona. Most of these hyperfine loops are characterized
by an apparently constant, but surprisingly narrow diameter of about
100 km all along each loop, and the loops originate on the solar
surface from intense, small-scale magnetic field elements. The NST
observations detect upward injections of hot plasma that excite the
hyperfine loops from the photosphere to the base of the corona. The
ejecta have their individual footpoints in the intergranular lanes
between the sun’s ubiquitous, convectively driven granules. In
many cases, AIA/SDO detects co-spatial and co-temporal brightenings
in the overlying, million-degree coronal loops in conjunction with
the upward injections along the hyperfine loops. Segments of some
of the more intense upward injections are seen as rapid blue-shifted
events in simultaneous Hα blue wing images observed at BBSO. In sum,
the observations unambiguously show impulsive coronal heating events
from upward energy flows originating from intergranular lanes on the
solar surface accompanied by co-spatial mass flows.
Title: Observational Criteria For Small-scale Turbulent Dynamo In
The Solar Photosphere
Authors: Abramenko, Valentyna; Goode, P.; Yurchyshyn, V.
Bibcode: 2012AAS...22011002A
Altcode:
Generation and dispersal of the magnetic field on the Sun is a key
mechanism responsible for solar activity on all spatial and temporal
scales - from the solar cycle down to the evolution of small-scale
magnetic elements in the quiet Sun. The solar dynamo operates as
a non-linear dynamical process and is thought to be manifested
in two types: as a global dynamo responsible for the solar cycle
periodicity, and as a small-scale turbulent dynamo (SSTD) responsible
for the formation of magnetic carpet in the quiet Sun. Numerous MHD
simulations of the solar turbulence did not yet reach a consensus
as to the existence and role of SSTD on the Sun. At the same time,
high-resolution observations of the quiet Sun are capable to provide
certain criteria to prove or rule out SSTD. We suggest to probe four
possible criteria: i) mutual behaviour of the kinetic and magnetic power
spectra; ii) intermittency/multifractality of the magnetic field; iii)
smallest observed scale of magnetic flux tubes; iv) regime of magnetic
diffusivity on smallest observable scales. We analyse magnetic, velocity
and solar granulation data as derived from Hinode/SOT, SOHO/MDI, SDO/HMI
and the New Solar Telescope (NST) of Big Bear Solar Observatory (BBSO)
to explore the possibilities for SSTD in the quiet Sun.
Title: Properties of Umbral Dots as Measured from the New Solar
Telescope Data and MHD Simulations
Authors: Kilcik, A.; Yurchyshyn, V. B.; Rempel, M.; Abramenko, V.;
Kitai, R.; Goode, P. R.; Cao, W.; Watanabe, H.
Bibcode: 2012ApJ...745..163K
Altcode: 2011arXiv1111.3997K
We studied bright umbral dots (UDs) detected in a moderate size sunspot
and compared their statistical properties to recent MHD models. The
study is based on high-resolution data recorded by the New Solar
Telescope at the Big Bear Solar Observatory and three-dimensional (3D)
MHD simulations of sunspots. Observed UDs, living longer than 150 s,
were detected and tracked in a 46 minute long data set, using an
automatic detection code. A total of 1553 (620) UDs were detected
in the photospheric (low chromospheric) data. Our main findings
are (1) none of the analyzed UDs is precisely circular, (2) the
diameter-intensity relationship only holds in bright umbral areas, and
(3) UD velocities are inversely related to their lifetime. While nearly
all photospheric UDs can be identified in the low chromospheric images,
some small closely spaced UDs appear in the low chromosphere as a single
cluster. Slow-moving and long-living UDs seem to exist in both the low
chromosphere and photosphere, while fast-moving and short-living UDs
are mainly detected in the photospheric images. Comparison to the 3D
MHD simulations showed that both types of UDs display, on average, very
similar statistical characteristics. However, (1) the average number
of observed UDs per unit area is smaller than that of the model UDs,
and (2) on average, the diameter of model UDs is slightly larger than
that of observed ones.
Title: Magnetic and Kinetic Power Spectra as a Tool to Probe the
Turbulent Dynamo
Authors: Abramenko, V. I.; Yurchyshyn, V. B.; Goode, P. R.
Bibcode: 2011arXiv1112.2750A
Altcode:
Generation and diffusion of the magnetic field on the Sun is a key
mechanism responsible for solar activity on all spatial and temporal
scales - from the solar cycle down to the evolution of small-scale
magnetic elements in the quiet Sun. The solar dynamo operates as
a non-linear dynamical process and is thought to be manifest in two
types: as a global dynamo responsible for the solar cycle periodicity,
and as a small-scale turbulent dynamo responsible for the formation
of magnetic carpet in the quiet Sun. Numerous MHD simulations of the
solar turbulence did not yet reach a consensus as to the existence
of a turbulent dynamo on the Sun. At the same time, high-resolution
observations of the quiet Sun from Hinode instruments suggest
possibilities for the turbulent dynamo. Analysis of characteristics of
turbulence derived from observations would be beneficial in tackling
the problem. We analyse magnetic and velocity energy spectra as derived
from Hinode/SOT, SOHO/MDI, SDO/HMI and the New Solar Telescope (NST)
of Big Bear Solar Observatory (BBSO) to explore the possibilities for
the small-scale turbulent dynamo in the quiet Sun.
Title: Turbulent Diffusion in the Photosphere as Derived from
Photospheric Bright Point Motion
Authors: Abramenko, V. I.; Carbone, V.; Yurchyshyn, V.; Goode, P. R.;
Stein, R. F.; Lepreti, F.; Capparelli, V.; Vecchio, A.
Bibcode: 2011ApJ...743..133A
Altcode: 2011arXiv1111.4456A
On the basis of observations of solar granulation obtained with the
New Solar Telescope of Big Bear Solar Observatory, we explored proper
motion of bright points (BPs) in a quiet-sun area, a coronal hole, and
an active region plage. We automatically detected and traced BPs and
derived their mean-squared displacements as a function of time (starting
from the appearance of each BP) for all available time intervals. In all
three magnetic environments, we found the presence of a super-diffusion
regime, which is the most pronounced inside the time interval of 10-300
s. Super-diffusion, measured via the spectral index, γ, which is the
slope of the mean-squared displacement spectrum, increases from the
plage area (γ = 1.48) to the quiet-sun area (γ = 1.53) to the coronal
hole (γ = 1.67). We also found that the coefficient of turbulent
diffusion changes in direct proportion to both temporal and spatial
scales. For the minimum spatial scale (22 km) and minimum time scale
(10 s), it is 22 and 19 km2 s-1 for the coronal
hole and the quiet-sun area, respectively, whereas for the plage area
it is about 12 km2 s-1 for the minimum time
scale of 15 s. We applied our BP tracking code to three-dimensional
MHD model data of solar convection and found the super-diffusion with
γ = 1.45. An expression for the turbulent diffusion coefficient as
a function of scales and γ is obtained.
Title: Properties of Umbral Dots as Measured from the New Solar
Telescope Data and MHD Simulations
Authors: Yurchyshyn, V.; Kilcik, A.; Rempel, M.; Abramenko, V.; Kitai,
R.; Goode, P. R.; Cao, W.; Watanabe, H.
Bibcode: 2011sdmi.confE..86Y
Altcode:
We studied bright umbral dots (UDs) detected in the main sunspot
of AR NOAA 11108 and compare their statistical properties to a
state-of-the-art MHD model of a sunspot. The study is based on
high resolution data recorded on September 20, 2010 by the New Solar
Telescope (NST) at Big Bear Solar Observatory and 3D MHD simulations of
sunspots. The 46 min data set included photospheric (0.3nm TiO filter
centered at 705.7 nm) and chromospheric (0.025nm Hα Lyot filter)
adaptive optics corrected and speckle reconstructed images. Bright
UDs, living longer than 150 s, were detected and tracked using an
automatic UD detection code. Total 1553 (620) UDs were detected
in the photospheric (chromospheric) data. Our main findings are:
i) none of the analyzed UDs is of an exact circular shape, ii) the
diameter-intensity relationship only works for bright umbral areas, and
iii) UD velocities inversely related to their life time. Comparison of
photospheric and chromospheric data showed that nearly all photospheric
UDs can be identified in the chromospheric images. However, it appears
that some small closely spaced UDs appear in the chromospheric images
as a single cluster, which may lead to the underestimation of the total
number of detected chromospheric UDs. Also, while slow moving and long
living UDs seem to exist in both chromosphere and photosphere, fast
moving and short living ones are detected mainly in the photospheric
images. Comparison of model and observed data shows that both types
of UDs display very similar statistical characteristics. The main
difference between parameters of model and observed UDs is that i)
the average number of observed UDs per unit area is smaller than that
of the model UDs, and ii) on average, the diameter of model UDs is
slightly larger than that of observed ones.
Title: Photospheric Signatures of Granular-scale Flux Emergence and
Cancellation at the Penumbral Boundary
Authors: Lim, Eun-Kyung; Yurchyshyn, Vasyl; Abramenko, Valentyna;
Ahn, Kwangsu; Cao, Wenda; Goode, Philip
Bibcode: 2011ApJ...740...82L
Altcode: 2011arXiv1107.5254L
We studied flux emergence events of sub-granular scale in a solar
active region. The New Solar Telescope (NST) of the Big Bear Solar
Observatory made it possible to clearly observe the photospheric
signature of flux emergence with very high spatial (0farcs11 at 7057
Å) and temporal (15 s) resolution. From TiO observations with the
pixel scale of 0farcs0375, we found several elongated granule-like
features (GLFs) stretching from the penumbral filaments of a sunspot
at a relatively high speed of over 4 km s-1. After a
slender arched darkening appeared at the tip of a penumbral filament,
a bright point (BP) developed and quickly moved away from the filament,
forming and stretching a GLF. The size of a GLF was approximately
0farcs5 wide and 3'' long. The moving BP encountered nearby structures
after several minutes of stretching, and the well-defined elongated
shape of the GLF faded away. Magnetograms from the Solar Dynamics
Observatory/Helioseismic and Magnetic Imager and NST/InfraRed Imaging
Magnetograph revealed that those GLFs are photospheric indicators of
small-scale flux emergence, and their disappearance is related to
magnetic cancellation. From two well-observed events, we describe
detailed development of the sub-structures of GLFs and different
cancellation processes that each of the two GLFs underwent.
Title: Umbral Dynamics in the Near-infrared Continuum
Authors: Anđić, A.; Cao, W.; Goode, P. R.
Bibcode: 2011ApJ...736...79A
Altcode: 2011arXiv1105.1825A
We detected peaks of oscillatory power at 3 and ~6.5 minutes in the
umbra of the central sunspot of the active region NOAA AR 10707 in data
obtained in the near-infrared (NIR) continuum at 1565.7 nm. The NIR data
set captured umbral dynamics around 50 km below the τ500 =
1 level. The umbra does not oscillate as a whole, but rather in distinct
parts that are distributed over the umbral surface. The most powerful
oscillations, close to a period of ~6.5, do not propagate upward. We
noted a plethora of large umbral dots (UDs) that persisted for >=30
minutes and stayed in the same locations. The peaks of oscillatory
power above the detected UDs are located at 3 and 5 minute oscillations,
but are very weak in comparison with the oscillations of ~6.5 minutes.
Title: On the Origin of Intergranular Jets
Authors: Yurchyshyn, V. B.; Goode, P. R.; Abramenko, V. I.; Steiner, O.
Bibcode: 2011ApJ...736L..35Y
Altcode: 2011arXiv1106.5535Y
We observe that intergranular jets, originating in the intergranular
space surrounding individual granules, tend to be associated with
granular fragmentation, in particular, with the formation and evolution
of a bright granular lane (BGL) within individual granules. The BGLs
have recently been identified as vortex tubes by Steiner et al. We
further discover the development of a well-defined bright grain
located between the BGL and the dark intergranular lane to which it
is connected. Signatures of a BGL may reach the lower chromosphere
and can be detected in off-band Hα images. Simulations also indicate
that vortex tubes are frequently associated with small-scale magnetic
fields. We speculate that the intergranular jets detected in the New
Solar Telescope (NST) data may result from the interaction between
the turbulent small-scale fields associated with the vortex tube
and the larger-scale fields existing in the intergranular lanes. The
intergranular jets are much smaller and weaker than all previously known
jet-like events. At the same time, they appear much more numerous than
the larger events, leading us to the speculation that the total energy
release and mass transport by these tiny events may not be negligible in
the energy and mass-flux balance near the temperature minimum atop the
photosphere. The study is based on the photospheric TiO broadband (1.0
nm) filter data acquired with the 1.6 m NST operating at the Big Bear
Solar Observatory. The data set also includes NST off-band Hα images
collected through a Zeiss Lyot filter with a passband of 0.025 nm.
Title: Near-infrared Imaging Spectropolarimeter For The Nst
Authors: Cao, Wenda; Ahn, K.; Gorceix, N.; Shumko, S.; Coulter, R.;
Goode, P.
Bibcode: 2011SPD....42.0606C
Altcode: 2011BAAS..43S.0606C
The NST Near-Infrared Imaging Spectropolarimeter is one of the first
imaging solar spectro-polarimeters working in the near infrared
(NIR). It has been installed and commissioned in the Coude Lab of the
1.6-meter NST at Big Bear Solar Observatory (BBSO). This innovative
system, which includes a 2.5 nm interference filter, a unique 0.25
nm birefringent Lyot filter, and a Fabry-Perot etalon, is capable of
providing a bandpass as low as 0.01 nm over a field-of-view (FOV) of 50"
in a telecentric configuration. An NIR waveplate rotates ahead of M3
in the NST as the polarimeter modulator, and ahead of it a calibration
unit is located to reduce polarization cross-talk induced by subsequent
oblique mirrors. Dual-beam differential polarimetry is employed to
minimize seeing-induced spurious polarization. Based on the unique
advantages in IR window, the very capable NST with adaptive optics, it
will provide unprecedented solar spectro-polarimetry with high Zeeman
sensitivity (10-3Ic), high spatial resolution
(0.2"), and high cadence (15s). In this presentation, we discuss the
design, fabrication, and calibration, as well as showing the results
of the first light observations.
Title: Sunspot Umbral Dots Detected with the New Solar Telescope
Authors: Kilcik, Ali; Yurchyshyn, V.; Abramenko, V.; Goode, P.; Cao, W.
Bibcode: 2011SPD....42.1901K
Altcode: 2011BAAS..43S.1901K
We present a study of bright umbral dots detected inside a large sunspot
of NOAA AR 11108. This study is based on high resolution data recorded
on September 20, 2010 with the New Solar Telescope (NST) at Big Bear
Solar Observatory. The data set, spanning 46 min, consists of a total
of 184 adaptive optics corrected and speckle reconstructed images
obtained with a 0.3 nm passband TiO filter centered on the 705.7 nm
spectral line. The image cadence is 15 s and the pixel size of 0.0375
arcsec. Bright umbral dots (UDs) were detected and tracked using
an automatic routine. Here we only focus on long living UDs (>150
s in life time) and a total of 513 such features were detected during
the observed period. We found that the average lifetime of a UD is 7.4
min and an average size is 0.34 arcsec. There is a tendency for larger
UDs to be brighter (and more circular). Many UDs are not of circular
shape. We will also present probability distribution of various physical
parameters and compare the results to similar earlier studies.
Title: Active Region High Velocity Events Observed by Fast Imaging
Solar Spectrograph on the NST
Authors: Ahn, Kwangsu; Chae, J.; Nah, J.; Park, H.; Jang, B.; Yang,
H.; Park, Y.; Cao, W.; Goode, P. R.
Bibcode: 2011SPD....42.1904A
Altcode: 2011BAAS..43S.1904A
The Fast Imaging Solar Spectrograph (FISS) is the only
spectrograph-based instrument on the NST that is currently
operational. With a high spectral resolution of 1.4 x 105
and simultaneous dual spectral band imaging, this instrument can
accurately determine the physical parameters of chromospheric features
--- filaments, jets and so on. Initial observations captured several
peculiar dynamic events that showed high line-of-sight velocities
of the order of 20 km s-1 in the vicinity of sunspots. We
expect that FISS will provide a better understanding of the physics
in the chromosphere with the aid of the unprecedentedly high spatial
resolution of NST.
Title: NST and Photospheric Fine -scale Structures Indicating the
Small Scale Flux Emergence in an Active Region
Authors: Lim, Eunkyung; Yurchyshyn, V.; Abramenko, V.; Goode, P.;
Ahn, K.
Bibcode: 2011SPD....42.0604L
Altcode: 2011BAAS..43S.0604L
We have studied very small-scale flux emergence events on granular
scales in a solar active region. The New Solar Telescope of Big Bear
Solar Observatory made it possible to clearly observe the photospheric
signature of flux emergence with a very high spatial (0".034/pixel) and
temporal (15s) resolution. From the TiO observations, we found several
elongated thread-like granules protruding from the penumbral filaments
of a sunspot at a relatively high speed of over 4km s-1. A slender
arched darkening protrudes from the tip of the penumbral filament, then
quickly stretches its length along the intergranular lane with a slight
bright point developing at the previously shaded leading edge. The size
of such granules is approximately 0".5 wide and 3” long, and their
stretching lasts for several minutes before contacting other magnetic
structures nearby. Magnetograms from HMI/SDO and IRIM/BBSO show that
such elongated granules are photospheric indicators of small-scale
flux emergence. The cancellation process is also described in detail
for two events that show different chromospheric signatures, such
as brightenings and jets during the cancellation. We speculate that
subsurface connectivity and the depth of the roots of magnetic field
are the main keys to determining different cancellation phenomena.
Title: The New Solar Telescope in Big Bear
Authors: Goode, Philip R.
Bibcode: 2011SPD....42.0601G
Altcode: 2011BAAS..43S.0601G
The 1.6 m clear aperture, off-axis solar telescope (the "NST") in Big
Bear Lake enjoyed first light in January 2009. In the Summer of 2009,
high resolution, speckle corrected observations were made in TiO and
Halpha. In the Summer of 2010, adaptive optics were implemented and the
first magnetograms were obtained. The NST is first new U.S. facility
class solar telescope in a generation. The NST has an off-axis Gregorian
configuration consisting of a parabolic primary, heat-stop, elliptical
secondary and diagonal flats. The focal ratio of the primary mirror
is f/2.4, and the final ratio is f/50. The working wavelength range
covers from 0.4 to 1.7 microns in the Coude Lab beneath the telescope
and all wavelengths including the far infrared before the entrance
window to the Coude Lab. Observational results will be introduced
including revealing granular-scale chromospheric jets with their origin
in the dark intergranular lanes, revealing bright lanes in granules,
demonstration of equipartition between photospheric magnetic fields
and plasma flow, and some unexpected results in the evolution of
bright points.
Title: New View on Quiet-Sun Photospheric Dynamics Offered by NST Data
Authors: Abramenko, Valentyna; Yurchyshyn, V.; Goode, P. R.
Bibcode: 2011SPD....42.0603A
Altcode: 2011BAAS..43S.0603A
Recent observations of the quiet sun photosphere obtained with the
1.6 meter New Solar telescope (NST) of Big Bear Solar observatory
(BBSO) delivered new information about photospheric fine structures
and their dynamics, as well as posing new questions. The 2-hour
uninterrupted data set of solar granulation obtained under excellent
seeing conditions on August 3, 2010 (with cadence of 10 sec) was the
basis for the study. Statistical analysis of automatically detected and
tracked magnetic bright points (MBPs) showed that the MBPs population
monotonically increases as their size decreases, down to 60-70 km. Our
analysis shows that if the smallest magnetic flux tubes exist, their
size is still smaller that 60-70 km, which impose strong restrictions on
the modeling of these structures. We also found that the distributions
of the MBP's size and lifetime do not follow a traditional Gaussian
distribution, typical for random processes. Instead, it follows a
log-normal distribution, typical for avalanches, catastrophes, stock
market data, etc. Our data set also demonstrated that a majority (98.6
%) of MBPs are short live (<2 min). This remarkable fact was not
obvious from previous studies because an extremely high time cadence
was required. The fact indicates that the majority of MBPs appear for a
very short time (tens of seconds), similar to other transient features,
for example, chromospheric jets. The most important point here is that
these small and short living MBPs significantly increase dynamics
(flux emergence, collapse into MBPs, and magnetic flux recycling)
of the solar surface magnetic fields.
Title: Response of Granulation to Small-scale Bright Features in
the Quiet Sun
Authors: Anđić, A.; Chae, J.; Goode, P. R.; Cao, W.; Ahn, K.;
Yurchyshyn, V.; Abramenko, V.
Bibcode: 2011ApJ...731...29A
Altcode: 2011arXiv1102.3404A
We detected 2.8 bright points (BPs) per Mm2 in the quiet
Sun with the New Solar Telescope at Big Bear Solar Observatory, using
the TiO 705.68 nm spectral line at an angular resolution ~0farcs1 to
obtain a 30 minute data sequence. Some BPs formed knots that were
stable in time and influenced the properties of the granulation
pattern around them. The observed granulation pattern within ~3''
of knots presents smaller granules than those observed in a normal
granulation pattern, i.e., around the knots a suppressed convection
is detected. Observed BPs covered ~5% of the solar surface and were
not homogeneously distributed. BPs had an average size of 0farcs22,
they were detectable for 4.28 minutes on average, and had an averaged
contrast of 0.1% in the deep red TiO spectral line.
Title: The New Solar Telescope in Big Bear: Polarimetry II
Authors: Cao, W.; Ahn, K.; Goode, P. R.; Shumko, S.; Gorceix, N.;
Coulter, R.
Bibcode: 2011ASPC..437..345C
Altcode:
IRIM (Infrared Imaging Magnetograph) is one of the first imaging solar
spectro-polarimeters working in the near infrared (NIR). IRIM is being
installed and commissioned in the Coudé Lab of the 1.6-meter New Solar
Telescope (NST) at Big Bear Solar Observatory (BBSO). This innovative
system, which includes a 2.5 nm interference filter, a unique 0.25
nm birefringent Lyot filter, and a Fabry-Pérot etalon, is capable of
providing a bandpass as low as 0.01 nm over a field-of-view of 50" in a
telecentric configuration. An NIR waveplate rotates ahead of M3 in the
NST as the polarimeter modulator, and ahead of it locates a calibration
unit to reduce polarization cross-talk induced by subsequent oblique
mirrors. Dual-beam differential polarimetry is employed to minimize
seeing-induced spurious polarization. Based on the unique advantages
in IR window, the very capable NST with adaptive optics, IRIM will
provide unprecedented solar spectro-polarimetry with high Zeeman
sensitivity (10-3Ic), high spatial resolution
(0.2"), and high cadence (15 s). In this paper, we discuss the design,
fabrication, and calibration of IRIM, as well as the results of the
first light observations.
Title: Time Distributions of Large and Small Sunspot Groups Over
Four Solar Cycles
Authors: Kilcik, A.; Yurchyshyn, V. B.; Abramenko, V.; Goode, P. R.;
Ozguc, A.; Rozelot, J. P.; Cao, W.
Bibcode: 2011ApJ...731...30K
Altcode: 2011arXiv1111.3999K
Here we analyze solar activity by focusing on time variations of
the number of sunspot groups (SGs) as a function of their modified
Zurich class. We analyzed data for solar cycles 20-23 by using Rome
(cycles 20 and 21) and Learmonth Solar Observatory (cycles 22 and 23)
SG numbers. All SGs recorded during these time intervals were separated
into two groups. The first group includes small SGs (A, B, C, H, and
J classes by Zurich classification), and the second group consists
of large SGs (D, E, F, and G classes). We then calculated small and
large SG numbers from their daily mean numbers as observed on the
solar disk during a given month. We report that the time variations
of small and large SG numbers are asymmetric except for solar cycle
22. In general, large SG numbers appear to reach their maximum in the
middle of the solar cycle (phases 0.45-0.5), while the international
sunspot numbers and the small SG numbers generally peak much earlier
(solar cycle phases 0.29-0.35). Moreover, the 10.7 cm solar radio
flux, the facular area, and the maximum coronal mass ejection speed
show better agreement with the large SG numbers than they do with
the small SG numbers. Our results suggest that the large SG numbers
are more likely to shed light on solar activity and its geophysical
implications. Our findings may also influence our understanding of
long-term variations of the total solar irradiance, which is thought
to be an important factor in the Sun-Earth climate relationship.
Title: The New Solar Telescope in Big Bear: Polarimetry I
Authors: Goode, P. R.; Cao, W.; Ahn, K.; Gorceix, N.; Coulter, R.
Bibcode: 2011ASPC..437..341G
Altcode:
We present here the near-term polarimetry plans for the 1.6 m clear
aperture, off-axis telescope in Big Bear. The first scientific data
were taken in the Summer of 2009 at the Nasmyth focus, and first
observations corrected by adaptive optics were taken in the Summer
of 2010. The first polarimetry for this telescope will be done in the
near infrared at 1.56 μm, which is close to the photospheric opacity
minimum. We show and explain reasons for the general layout of the
polarimetric hardware for the telescope.
Title: Development of the Fast Imaging Solar Spectrograph for 1.6
m New Solar Telescope
Authors: Nah, Ja-Kyoung; Chae, Jong-Chul; Park, Young-Deuk; Park,
Hyung-Min; Jang, Bi-Ho; Ahn, Kwang-Su; Yang, Hee-Su; Cho, Kyung-Suk;
Kim, Yeon-Han; Kim, Kwang-Dong; Cao, Wenda; Gorceix, Nicolas; Goode,
Philip. R.
Bibcode: 2011PKAS...26...45N
Altcode:
No abstract at ADS
Title: Maximum Coronal Mass Ejection Speed as an Indicator of Solar
and Geomagnetic Activities
Authors: Kilcik, A.; Yurchyshyn, V. B.; Abramenko, V.; Goode, P. R.;
Gopalswamy, N.; Ozguc, A.; Rozelot, J. P.
Bibcode: 2011ApJ...727...44K
Altcode: 2011arXiv1111.4000K
We investigate the relationship between the monthly averaged maximal
speeds of coronal mass ejections (CMEs), international sunspot number
(ISSN), and the geomagnetic Dst and Ap indices covering the 1996-2008
time interval (solar cycle 23). Our new findings are as follows. (1)
There is a noteworthy relationship between monthly averaged maximum CME
speeds and sunspot numbers, Ap and Dst indices. Various peculiarities
in the monthly Dst index are correlated better with the fine structures
in the CME speed profile than that in the ISSN data. (2) Unlike the
sunspot numbers, the CME speed index does not exhibit a double peak
maximum. Instead, the CME speed profile peaks during the declining
phase of solar cycle 23. Similar to the Ap index, both CME speed and
the Dst indices lag behind the sunspot numbers by several months. (3)
The CME number shows a double peak similar to that seen in the sunspot
numbers. The CME occurrence rate remained very high even near the
minimum of the solar cycle 23, when both the sunspot number and the
CME average maximum speed were reaching their minimum values. (4) A
well-defined peak of the Ap index between 2002 May and 2004 August was
co-temporal with the excess of the mid-latitude coronal holes during
solar cycle 23. The above findings suggest that the CME speed index may
be a useful indicator of both solar and geomagnetic activities. It may
have advantages over the sunspot numbers, because it better reflects
the intensity of Earth-directed solar eruptions.
Title: Fast Imaging Solar Spectrograph System in New Solar Telescope
Authors: Park, Y. -D.; Kim, Y. H.; Chae, J.; Goode, P. R.; Cho, K. S.;
Park, H. M.; Nah, J. K.; Jang, B. H.
Bibcode: 2010nspm.conf..189P
Altcode:
In 2004, Big Bear Solar Observatory in California, USA launched
a project for construction of the world's largest aperture solar
telescope (D = 1.6m) called New Solar Telescope(NST). University
of Hawaii (UH) and Korea Astronomy and Space Science Institute(KASI)
partly collaborate on the project. NST is a designed off-axis parabolic
Gregorian reflector with very high spatial resolution(0.07 arcsec
at 5000A) and is equipped with several scientific instruments such as
Visible Imaging Magnetograph (VIM), InfraRed Imaging Magnetograph IRIM),
and so on. Since these scientific instruments are focused on studies of
the solar photosphere, we need a post-focus instrument for the NST to
study the fine structures and dynamic patterns of the solar chromosphere
and low Transition Region (TR) layer, including filaments/prominences,
spicules, jets, micro flares, etc. For this reason, we developed and
installed a fast imaging solar spectrograph(FISS) system on the NST
withadvantages of achieving compact design with high spectral resolution
and small aberration as well as recording many solar spectral lines in
a single and/or dual band mode. FISS was installed in May, 2010 and now
we carry out a test observation. In this talk, we introduce the FISS
system and the results of the test observation after FISS installation.
Title: Photosphere-Chromosphere Connection as Derived from Nst
Observations
Authors: Yurchyshyn, V.; Abramenko, V.; Goode, P. R.
Bibcode: 2010AGUFMSH31C1807Y
Altcode:
Largest ground-based new solar telescope (NST) of Big Bear Solar
Observatory allows us to simultaneously observe photospheric
granulation with luxurious filigree of bright points (BPs) and
low/middle chromosphere in H- alpha spectral line. Excellent climate
conditions of Big Bear Valley, augmented with an adaptive optics system
and speckle-reconstruction applications produce diffraction limited
images. Recent observations (July- August 2010) showed that BPs visible
in the photosphere with the TiO filter (centered at a wavelength of
705.7 nm) are co-spatial with the BPs visible in the blue wind of
H-alpha line. As evidenced from these data, the H-alpha BPs, in turn,
are frequently at origin of small-scale chromospheric jets. These jets
are visible at all scales down to the smallest resolved features. As
long as photospheric BPs are co-spatial with the magnetic elements,
one might conclude that photospheric magnetic fields are relevant
to the chromospheric jet formation. NST Ha-0.13nm image acquired on
June 28, 2010. The dark features are upward directed flows that have
velocities up to 60km/sec seen against the background of photospheric
granulation with inclusions of BPs. The corresponding movie shows
reveals significant dynamics associated with these rosette like
structures stemming from clusters of BPs.
Title: Relationship between orientations of halo CMEs and the
underlying filament / active regions
Authors: Kilcik, A.; Yurchyshyn, V.; Abramenko, V.; Goode, P. R.
Bibcode: 2010AGUFMSH51C1684K
Altcode:
Coronal mass ejections (CMEs) are the most important objects of space
weather studies. Although they have been at focus of many studies for
a long time now, there are still many unanswered questions. Here we
focus on the possible relationship between the direction of CME rotation
and the prevailing magnetic twist of the CME's source region. We could
determine the predominant helicity for 45 filaments and active regions
that appeared on both hemispheres of the Sun. We thus further confirm
that 76% of all source regions in the southern hemisphere were “S”
shaped, while 79% of northern hemisphere events were reverse “S”
(“Z”) shaped. These ratios agree with the well known hemispheric
segregation rule. According to theoretical considerations, (Green,
et al. 2007; Lynch, et al. 2009) CMEs, associated with eruption of
“S” (“Z') shaped structures are expected to rotate clockwise
(counterclockwise). Here we report that 67% of all source regions in
the southern hemisphere showed a predominant twist that agreed with
the direction of rotation of the corresponding CMEs. In the northern
hemisphere this ration was 63%. These findings may significantly
improve our understanding of CME evolution and their connection to
magnetic clouds. They may are affect our ability to predict severity
of geomagnetic storms.
Title: Size and Life Time Distributions of Bright Points in the
Quiet Sun Photosphere
Authors: Abramenko, V.; Yurchyshyn, V.; Goode, P. R.
Bibcode: 2010AGUFMSH31C1806A
Altcode:
We present results of two-hour uninterrupted observations of solar
granulation obtained at excellent seeing conditions on August 3, 2010
with the largest ground-based new solar telescope (NST) operating
at Big Bear Solar observatory. Adaptive optics corrected data were
acquired with a broad-band TiO filter (centered at a wavelength of
705.7 nm). The time cadence was 10s and the pixel size was 0.0375
arcsec. Photospheric bright points (BPs) were automatically detected
and traced. We find that NST TiO BPs are co-spatial with those visible
in Hinode/SOT G-band images. In cases where Hinode/SOT detects one
large BP, NST shows several fully resolved BPs. Extended filigree
features running along intergranular lanes appear in NST images clearly
fragmented into separate BPs. The distribution function of the NST
BPs size is exponential and extends to the diffraction limit of NST
(77 km) without any saturation. The life time distribution function
follows a power law with an index of -1.9. About 98.6% of all detected
BPs live shorter than 120 s, and the most persistent BP lasted for
44 minutes. The size and the maximum intensity of BPs were found to
be proportional to the life time. Results are discussed in framework
of coronal heating and turbulent dynamo. Left - Hinode G-band image
obtained on 2010 August 3 at 12:22:11 UT (pixel size 0.109"). Right -
NST TiO image obtained on 2010 August 3 at 12:22:10 UT. Both images
cover the same area of 18.8" x 18.8" on the Sun. PDFs of the BPs
diameter calculated from NST TiO images (black) and from Hinode/SOT
G-band images (by Utz et al. 2009, blue).
Title: Statistical Distribution of Size and Lifetime of Bright Points
Observed with the New Solar Telescope
Authors: Abramenko, Valentyna; Yurchyshyn, Vasyl; Goode, Philip;
Kilcik, Ali
Bibcode: 2010ApJ...725L.101A
Altcode: 2010arXiv1012.1584A
We present results of 2 hr non-interrupted observations of solar
granulation obtained under excellent seeing conditions with the largest
aperture ground-based solar telescope—the New Solar Telescope
(NST)—of Big Bear Solar Observatory. Observations were performed
with adaptive optics correction using a broadband TiO filter in the
705.7 nm spectral line with a time cadence of 10 s and a pixel size
of 0farcs0375. Photospheric bright points (BPs) were detected and
tracked. We find that the BPs detected in NST images are cospatial with
those visible in Hinode/SOT G-band images. In cases where Hinode/SOT
detects one large BP, NST detects several separated BPs. Extended
filigree features are clearly fragmented into separate BPs in NST
images. The distribution function of BP sizes extends to the diffraction
limit of NST (77 km) without saturation and corresponds to a log-normal
distribution. The lifetime distribution function follows a log-normal
approximation for all BPs with lifetime exceeding 100 s. A majority
of BPs are transient events reflecting the strong dynamics of the
quiet Sun: 98.6% of BPs live less than 120 s. The longest registered
lifetime was 44 minutes. The size and maximum intensity of BPs were
found to be proportional to their lifetimes.
Title: Chromospheric Signatures of Small-scale Flux Emergence as
Observed with New Solar Telescope and Hinode Instruments
Authors: Yurchyshyn, V. B.; Goode, P. R.; Abramenko, V. I.; Chae,
J.; Cao, W.; Andic, A.; Ahn, K.
Bibcode: 2010ApJ...722.1970Y
Altcode: 2011arXiv1102.1034Y
With the ever-increasing influx of high-resolution images of the solar
surface obtained at a multitude of wavelengths, various processes
occurring at small spatial scales have become a greater focus of our
attention. Complex small-scale magnetic fields have been reported that
appear to have enough stored energy to heat the chromosphere. While
significant progress has been made in understanding small-scale
phenomena, many specifics remain elusive. We present here a detailed
study of a single event of disappearance of a magnetic dipole and
associated chromospheric activity. Based on New Solar Telescope Hα
data and Hinode photospheric line-of-sight magnetograms and Ca II
H images, we report the following. (1) Our analysis indicates that
even very small dipoles (elements separated by about 0farcs5 or less)
may reach the chromosphere and trigger non-negligible chromospheric
activity. (2) Careful consideration of the magnetic environment where
the new flux is deposited may shed light on the details of magnetic
flux removal from the solar surface. We argue that the apparent
collision and disappearance of two opposite polarity elements may
not necessarily indicate their cancellation (i.e., reconnection,
emergence of a "U" tube, or submergence of Ω loops). In our case, the
magnetic dipole disappeared by reconnecting with overlying large-scale
inclined plage fields. (3) Bright points (BPs) seen in off-band Hα
images are very well correlated with the Ca II H BPs, which in turn
are cospatial with G-band BPs. We further speculate that, in general,
Hα BPs are expected to be cospatial with photospheric BPs; however,
a direct comparison is needed to refine their relationship.
Title: Patterns of Flows in an Intermediate Prominence Observed
by Hinode
Authors: Ahn, Kwangsu; Chae, Jongchul; Cao, Wenda; Goode, Philip R.
Bibcode: 2010ApJ...721...74A
Altcode:
The investigation of plasma flows in filaments/prominences gives
us clues to understanding their magnetic structures. We studied
the patterns of flows in an intermediate prominence observed by
Hinode/SOT. By examining a time series of Hα images and Ca II H images,
we have found horizontal flows in the spine and vertical flows in
the barb. Both of these flows have a characteristic speed of 10-20 km
s-1. The horizontal flows displayed counterstreaming. Our
detailed investigation revealed that most of the moving fragments in
fact reversed direction at the end point of the spine near a footpoint
close to the associated active region. These returning flows may be
one possible explanation of the well-known counterstreaming flows
in prominences. In contrast, we have found vertical flows—downward
and upward—in the barb. Most of the horizontal flows in the spine
seem to switch into vertical flows when they approach the barb,
and vice versa. We propose that the net force resulting from a small
deviation from magnetohydrostatic equilibrium, where magnetic fields
are predominantly horizontal, may drive these patterns of flow. In the
prominence studied here, the supposed magnetohydrostatic configuration
is characterized by magnetic field lines sagging with angles of 13°
and 39° in the spine and the barb, respectively.
Title: Evidence of Filament Upflows Originating from Intensity
Oscillations on the Solar Surface
Authors: Cao, Wenda; Ning, Zongjun; Goode, Philip R.; Yurchyshyn,
Vasyl; Ji, Haisheng
Bibcode: 2010ApJ...719L..95C
Altcode:
A filament footpoint rooted in an active region (NOAA 11032) was well
observed for about 78 minutes with the 1.6 m New Solar Telescope at the
Big Bear Solar Observatory on 2009 November 18 in Hα ±0.75 Å. This
data set had high cadence (~15 s) and high spatial resolution (~0farcs1)
and offered a unique opportunity to study filament dynamics. As in
previous findings from space observations, several dark intermittent
upflows were identified, and they behave in groups at isolated locations
along the filament. However, we have two new findings. First, we
find that the dark upflows propagating along the filament channel are
strongly associated with the intensity oscillations on the solar surface
around the filament footpoints. The upflows start at the same time as
the peak in the oscillations, illustrating that the upflow velocities
are well correlated with the oscillations. Second, the intensity of
one of the seven upflows detected in our data set exhibits a clear
periodicity when the upflow propagates along the filament. The periods
gradually vary from ~10 to ~5 minutes. Our results give observational
clues on the driving mechanism of the upflows in the filament.
Title: Oscillatory Behavior in the Quiet Sun Observed with the New
Solar Telescope
Authors: Anđić, A.; Goode, P. R.; Chae, J.; Cao, W.; Ahn, K.;
Yurchyshyn, V.; Abramenko, V.
Bibcode: 2010ApJ...717L..79A
Altcode: 2010arXiv1007.0272A
Surface photometry of the quiet Sun has achieved an angular resolution
of 0farcs1 with the New Solar Telescope at Big Bear Solar Observatory,
revealing that a disproportionate fraction of the oscillatory events
appear above observed bright point-like structures. During the tracking
of these structures, we noted that the more powerful oscillatory events
are cospatial with them, indicating that observed flux tubes may be
the source of many observed oscillatory events.
Title: Repackaging and characterizing of a HgCdTe CMOS infrared
camera for the New Solar Telescope
Authors: Cao, Wenda; Coulter, Roy; Gorceix, Nicolas; Goode, Philip R.
Bibcode: 2010SPIE.7742E..20C
Altcode: 2010SPIE.7742E..55C
The 1.6-meter New Solar Telescope (NST) is currently the world's
largest aperture solar telescope. The NST is newly built at Big Bear
Solar Observatory (BBSO). Among other instruments, the NST is equipped
with several focal plane instruments operating in the near infrared
(NIR). In order to satisfy the diverse observational requirements of
these scientific instruments, a 1024 × 1024 HgCdTe TCM8600 CMOS camera
manufactured by Rockwell Scientific Company has been repackaged and
upgraded at Infrared Laboratories Inc. A new ND-5 dewar was designed to
house the TCM8600 array with a low background filter wheel, inverted
operation and at least 12 hours of hold time between fills. The
repackaged camera will be used for high-resolution NIR photometry
at the NST Nasmyth focus on the telescope and high-precision NIR
spectro-polarimetry in the NST Coudé Lab below. In March 2010, this
repackaged camera was characterized in the Coudé Lab at BBSO. This
paper presents the design of new dewar, the detailed process of
repackaging and characterizing the camera, and a series of test results.
Title: Nasmyth focus instrumentation of the New Solar Telescope at
Big Bear Solar Observatory
Authors: Cao, Wenda; Gorceix, Nicolas; Coulter, Roy; Wöger, Friedrich;
Ahn, Kwangsu; Shumko, Sergiy; Varsik, John; Coulter, Aaron; Goode,
Philip R.
Bibcode: 2010SPIE.7735E..5VC
Altcode: 2010SPIE.7735E.194C
The largest solar telescope, the 1.6-m New Solar Telescope (NST) has
been installed and is being commissioned at Big Bear Solar Observatory
(BBSO). It has an off-axis Gregorian configuration with a focal ratio
of F/52. Early in 2009, first light scientific observations were
successfully made at the Nasmyth focus, which is located on the east
side of the telescope structure. As the first available scientific
instruments for routine observation, Nasmyth focus instrumentation
(NFI) consists of several filtergraphs offering high spatial resolution
photometry in G-band 430 nm, Ha 656 nm, TiO 706 nm, and covering the
near infrared 1083 nm, 1.6 μm, and 2.2 μm. With the assistance of
a local correlation tracker system, diffraction limited images were
obtained frequently over a field-of-view of 70 by 70 after processed
using a post-facto speckle reconstruction algorithm. These data sets
not only serve for scientific analysis with an unprecedented spatial
resolution, but also provide engineering feedback to the NST operation,
maintenance and optimization. This paper reports on the design and the
implementation of NFI in detail. First light scientific observations
are presented and discussed.
Title: First light of the 1.6 meter off-axis New Solar Telescope at
Big Bear Solar Observatory
Authors: Cao, Wenda; Gorceix, Nicolas; Coulter, Roy; Coulter, Aaron;
Goode, Philip R.
Bibcode: 2010SPIE.7733E..30C
Altcode: 2010SPIE.7733E..93C
New Jersey Institute of Technology, in collaboration with the University
of Hawaii and the Korea Astronomy & Space Science Institute, has
successfully developed and installed a 1.6 m clear aperture, off-axis
New Solar Telescope (NST) at the Big Bear Solar Observatory. The NST
will be the largest aperture solar telescope in the world until the 4
m Advanced Technology Solar Telescope (ATST) and 4 m European Solar
Telescope (EST) begin operation in the next decade. Meanwhile, the
NST will be the largest off-axis telescope before the 8.4 m segmented
Giant Magellan Telescope (GMT) comes on-line. The NST is configured
as an off-axis Gregorian system consisting of a parabolic primary,
prime focus field stop and heat reflector, elliptical secondary and
diagonal flats. The primary mirror is made of Zerodur from Schott and
figured to a final residual error of 16 nm rms by Steward Observatory
Mirror Lab. The final focal ratio is f/52. The 180 circular opening in
the field stop defines the maximal square field-of-view. The working
wavelength range will cover 0.4 to 1.7 μm in the Coud´e Lab two
floors beneath the telescope, and all wavelengths including far infrared
at the Nasmyth focus on an optical bench attached to the side of the
telescope structure. First-light scientific observations have been
attained at the Nasmyth focus and in the Coud´e Lab. This paper
presents a detailed description of installation and alignment of the
NST. First-light observational results are also shown to demonstrate
the validity of the NST optical alignment.
Title: The NST: First results and some lessons for ATST and EST
Authors: Goode, P. R.; Coulter, R.; Gorceix, N.; Yurchyshyn, V.;
Cao, W.
Bibcode: 2010AN....331..620G
Altcode:
In January 2009, first light observations with the NST (New Solar
Telescope) in Big Bear Solar Observatory (BBSO) were made. NST has a
1.7 m primary with a 1.6 m clear aperture. First observational results
in TiO and Hα are shown and discussed. The NST primary mirror is the
most aspheric telescope mirror deployed to date. The NST is early in its
commissioning, and the plans for this phase will be sketched. Lessons
learned in building and implementing the NST are germane for the ATST
and EST telescopes and will be discussed. The NST has an off-axis
Gregorian configuration consisting of a parabolic primary, heat-stop,
elliptical secondary and diagonal flats. The focal ratio of the
primary mirror is f/2.4. The working wavelength range covers from 0.4
to 1.7 μm in the Coudé Lab beneath the telescope and all wavelengths
including the far infrared at the Nasmyth focus on the dome floor.
Title: Scientific instrumentation for the 1.6 m New Solar Telescope
in Big Bear
Authors: Cao, W.; Gorceix, N.; Coulter, R.; Ahn, K.; Rimmele, T. R.;
Goode, P. R.
Bibcode: 2010AN....331..636C
Altcode:
The NST (New Solar Telescope), a 1.6 m clear aperture, off-axis
telescope, is in its commissioning phase at Big Bear Solar Observatory
(BBSO). It will be the most capable, largest aperture solar telescope
in the US until the 4 m ATST (Advanced Technology Solar Telescope)
comes on-line late in the next decade. The NST will be outfitted with
state-of-the-art scientific instruments at the Nasmyth focus on the
telescope floor and in the Coudé Lab beneath the telescope. At the
Nasmyth focus, several filtergraphs already in routine operation
have offered high spatial resolution photometry in TiO 706 nm,
H\alpha 656 nm, G-band 430 nm and the near infrared (NIR), with the
aid of a correlation tracker and image reconstruction system. Also,
a Cryogenic Infrared Spectrograph (CYRA) is being developed to supply
high signal-to-noise-ratio spectrometry and polarimetry spanning
1.0 to 5.0 μm. The Coudé Lab instrumentation will include Adaptive
Optics (AO), InfraRed Imaging Magnetograph (IRIM), Visible Imaging
Magnetograph (VIM), and Fast Imaging Solar Spectrograph (FISS). A 308
sub-aperture (349-actuator deformable mirror) AO system will enable
nearly diffraction limited observations over the NST's principal
operating wavelengths from 0.4 μm through 1.7 μm. IRIM and VIM are
Fabry-Pérot based narrow-band tunable filters, which provide high
resolution two-dimensional spectroscopic and polarimetric imaging in
the NIR and visible respectively. FISS is a collaboration between BBSO
and Seoul National University focussing on chromosphere dynamics. This
paper reports the up-to-date progress on these instruments including an
overview of each instrument and details of the current state of design,
integration, calibration and setup/testing on the NST.
Title: Highest Resolution Observations of the Quietest Sun
Authors: Goode, Philip R.; Yurchyshyn, Vasyl; Cao, Wenda; Abramenko,
Valentyna; Andic, Aleksandra; Ahn, Kwangsu; Chae, Jongchul
Bibcode: 2010ApJ...714L..31G
Altcode:
Highest resolution observations made with the new 1.6 m aperture solar
telescope in Big Bear Solar Observatory during this time of historic
inactivity on the Sun reveal new insights into the small-scale dynamics
of the Sun's photosphere. The telescope's unprecedented resolution
enabled us to observe that the smallest scale photospheric magnetic
field seems to come in isolated points in the dark intergranular lanes,
rather than the predicted continuous sheets confined to the lanes, and
the unexpected longevity of the bright points implies a deeper anchoring
than predicted. Further, we demonstrated for the first time that the
photospheric plasma motion and magnetic fields are in equipartition
over a wide dynamic range, and both cascade energy to ever-smaller
scales according to classical Kolmogorov turbulence theory. Finally,
we discovered tiny jet-like features originating in the dark lanes that
surround the ubiquitous granules that characterize the solar surface.
Title: New Solar Telescope Observations of Magnetic Reconnection
Occurring in the Chromosphere of the Quiet Sun
Authors: Chae, Jongchul; Goode, P. R.; Ahn, K.; Yurchysyn, V.;
Abramenko, V.; Andic, A.; Cao, W.; Park, Y. D.
Bibcode: 2010ApJ...713L...6C
Altcode:
Magnetic reconnection is a process in which field-line connectivity
changes in a magnetized plasma. On the solar surface, it often
occurs with the cancellation of two magnetic fragments of opposite
polarity. Using the 1.6 m New Solar Telescope, we observed the
morphology and dynamics of plasma visible in the Hα line, which is
associated with a canceling magnetic feature (CMF) in the quiet Sun. The
region can be divided into four magnetic domains: two pre-reconnection
and two post-reconnection. In one post-reconnection domain, a small
cloud erupted, with a plane-of-sky speed of 10 km s-1,
while in the other one, brightening began at points and then tiny
bright loops appeared and subsequently shrank. These features support
the notion that magnetic reconnection taking place in the chromosphere
is responsible for CMFs.
Title: Automated Observations of the Earthshine
Authors: Goode, P. R.; Shoumko, S.; Pallé, E.; Montañés-Rodríguez,
P.
Bibcode: 2010AdAst2010E..26G
Altcode:
No abstract at ADS
Title: Vorticity of Granular Flows from NST Observations
Authors: Pevtsov, A. A.; Abramenko, V.; Yurchyshyn, V.; Goode, P. R.
Bibcode: 2009AGUFMSH53B..04P
Altcode:
We use observations taken with the New Solar Telescope (NST) at Big
Bear Solar Observatory, the world largest solar optical telescope with
diffraction limited spatial resolution of 0.06 arc seconds, to study
vorticity of granular flows in quiet Sun areas. We employ sequence
of images observed with TiO (705.7 nm) filter with time cadence
of 30 seconds. The atmospheric seeing effects were removed using
speckle-reconstruction technique. We compare vorticity of granular
flows and intergranular vortices, and discuss our findings in the
framework of surface (turbulent) dynamo.
Title: First Results from 1.6 m Off-Axis Solar Telescope in Big Bear
(Invited)
Authors: Goode, P. R.
Bibcode: 2009AGUFMSH53B..01G
Altcode:
In early 2009 at Big Bear Solar Observatory, first light science
observations were made with BBSO's NST (New Solar Telescope), which
has a 1.6m clear aperture (0.06” resolution at 500 nm). After
a brief introduction to some of the lessons learned in making the
telescope, first light observations in TiO, Halpha, G-Band and 1.56
micron lines will be introduced with detailed results presented in
other talks in this session, including joint observations with Hinode
and other satellites. The NST has an off-axis Gregorian configuration
consisting of a parabolic primary, heat-stop, elliptical secondary
and diagonal flats. The focal ratio of the primary mirror is f/2.4,
and the final ratio is f/50. The working wavelength range covers from
0.4 to 1.7 microns in the Coude Lab beneath the telescope and all
wavelengths including the far infrared at the Nasmyth focus on the
dome floor. Plans for the on-going commissioning phase will be sketched.
Title: Behavior of the Spines in a Quiescent Prominence Observed
by Hinode/SOT
Authors: Ning, Z.; Cao, W.; Goode, P. R.
Bibcode: 2009ApJ...707.1124N
Altcode:
We report the behaviors of the spines in a quiescent prominence
from the observations on 2008 January 15 made with Hinode/SOT in
Hα +0.076 Å, Hα-0.34 Å, and Ca II H line filters. Two spines (1
and 2) are visible in this event. In the spacetime plots of the Hα
and Ca II intensities, the two spines seem to gradually move closer
together, and finally merge, then separate again. Their behaviors are
separated into two kinds of typical motions. On the Doppler diagrams,
the spine 1 has a dominant redshift, and spine 2 favors a blueshift,
which reveals that the spines 1 and 2 firstly display the drifting
motions in opposite directions. The former is drifting northward, while
the latter drifts southward. Second, both spines display large-scale
oscillating motions. Their oscillating velocities, amplitudes, and
periods have average values of 3 km s-1, ±5 Mm, and 98
minutes, respectively, indicating a small-amplitude oscillation with a
long period. After the sinusoidal fitting, both spines almost exhibit
an antiphase oscillating motions. The spine 2 oscillates 135° ahead
of the spine 1. Such antiphase oscillations would reflect the coupling
of the transverse oscillations of the spines in this prominence.
Title: Periodicity of Twisting Motions in Sunspot Penumbral Filaments
Authors: Ning, Zongjun; Cao, Wenda; Goode, Philip R.
Bibcode: 2009SoPh..257..251N
Altcode:
We study the periodicity of twisting motions in sunspot penumbral
filaments, which were recently discovered from space (Hinode) and
ground-based (SST) observations. A sunspot was well observed for
97 minutes by Hinode/SOT in the G-band (4305 Å) on 12 November
2006. By the use of the time - space gradient applied to intensity
space - time plots, twisting structures can be identified in the
penumbral filaments. Consistent with previous findings, we find that
the twisting is oriented from the solar limb to disk center. Some of
them show a periodicity. The typical period is about ≈ four minutes,
and the twisting velocity is roughly 6 km s−1. However,
the penumbral filaments do not always show periodic twisting motions
during the time interval of the observations. Such behavior seems to
start and stop randomly with various penumbral filaments displaying
periodic twisting during different intervals. The maximum number of
periodic twists is 20 in our observations. Studying this periodicity can
help us to understand the physical nature of the twisting motions. The
present results enable us to determine observational constraints on
the twisting mechanism.
Title: Return Flows in a Counter-streaming Prominence
Authors: Ahn, Kwangsu; Chae, J.; Goode, P.
Bibcode: 2009SPD....40.1008A
Altcode:
It is known that the fine structures of filaments/prominences show
counter-streaming motion. We found that the counter-streaming could be
an outcome of return flows at the edge of filaments/prominences. We
picked an intermediate prominence that showed a dominant horizontal
motion. The trajectories of the plasma fragments in this prominence
showed that most of the plasma in this prominence changed their
direction near the edge of prominence structure. This implies that
the counter-streaming may be represented by plasma which move back and
forth along the horizontal magnetic field lines. We assumed that there
could be magnetic pillar-like structures near the edge, so that they
could increase magnetic pressure near the edge, pulling the plasma
back to the original position.
Title: Post-focus Instrumentation Of The NST
Authors: Cao, Wenda; Gorceix, N.; Andic, A.; Ahn, K.; Coulter, R.;
Goode, P.
Bibcode: 2009SPD....40.1803C
Altcode:
The NST (New Solar Telescope), 1.6 m clear aperture, off-axis
telescope, is in its commissioning phase at Big Bear Solar Observatory
(BBSO). It will be the most capable, largest aperture solar telescope
in the US until the 4 m ATST (Advanced Technology Solar Telescope)
comes on-line in the middle of the next decade. The NST will be
outfitted with state-of-the-art post-focus instrumentation, which
currently include Adaptive Optics system (AO), InfraRed Imaging
Magnetograph (IRIM), Visible Imaging Magnetograph (VIM), Real-time
Image Reconstruction System (RIRS), and Fast Imaging Solar Spectrograph
(FISS). A 308 sub-aperture (349-actuator Deformable Mirror) AO system
will enable diffraction limited observations over the NST's principal
operating wavelengths from 0.4 µm through 1.7 µm. IRIM and VIM
are Fabry-Perot based narrow-band tunable filter, which provide high
resolution two-dimensional spectroscopic and polarimetric imaging in
the near infrared and visible respectively. Using a 32-node parallel
computing system, RIRS is capable of performing real-time image
reconstruction with one image every minute. FISS is a collaboration
between NJIT and Seoul National University to focus on chromosphere
dynamics. This instruments would be installed this Summer as a part
of the NST commissioning and the implementation of Nysmyth focus
instrumentation. Key tasks including optical design, hardware/software
integration and subsequent setup/testing on the NST, will be presented
in this poster. First light images from the NST will be shown.
Title: Oscillatory Behavior and its Connection to Granulation
Authors: Andic, Aleksandra; Cao, W.; Goode, P. R.; Jess, D. B.
Bibcode: 2009SPD....40.0933A
Altcode:
Results are presented from two distinct sets of the observations to
further elucidate origin of, and the role of high frequency oscillations
in atmospheric dynamics. One set was performed using IBIS that
Observatorio Astrofisico di Arcetri developed. This 2D spectrograph
utilized the Fe I 709nm spectral line at the Dunn Solar telescope,
Sacramento Peak, of National Solar Observatory. This data set was
first speckle reconstructed. The second data set was obtained from
the same telescope using BBSO's IRIM with its Rockwell Near Infrared
Camera measuring the Fe 1565.7nm spectral line. It was determined
that the magnetic field has a significant role in propagation of
the oscillations, and our near infrared observations revealed new
insights into the oscillatory dynamics of the deep photosphere. Detailed
results will be presented.
Title: The Lunar Terrestrial Observatory: Observing the Earth using
photometers on the Moon’s surface
Authors: Pallé, E.; Goode, P. R.
Bibcode: 2009AdSpR..43.1083P
Altcode:
The Earth's albedo is one of the least studied fundamental climate
parameters. The albedo is a bi-directional variable, and there is a high
degree of anisotropy in the light reflected from a given terrestrial
surface. However, simultaneously observing from all points on Earth
at all reflecting angles is a practical impossibility. Therefore,
all measurements from which albedo can be inferred require assumptions
and/or modeling to derive a good estimate. Nowadays, albedo measurements
are taken regularly either from low Earth orbit satellite platforms
or from ground-based measurements of the earthshine from the dark
side of the Moon. But the results from these different measurements
are not in satisfactory agreement. Clearly, the availability of
different albedo databases and their inter-comparisons can help to
constrain the assumptions necessary to reduce the uncertainty of the
albedo estimates. In recent years, there has been a renewed interest
in the development of robotic and manned exploration missions to
the Moon. Returning to the Moon will enable diverse exploration
and scientific opportunities. Here we discuss the possibility of a
lunar-based Earth radiation budget monitoring experiment, the Lunar
Terrestrial Observatory, and evaluate its scientific and practical
advantages compared to the other, more standard, observing platforms. We
conclude that a lunar-based terrestrial observatory can enable advances
in Earth sciences, complementary to the present efforts, and to our
understanding of the Earth's climate.
Title: Interannual variations in Earth's reflectance 1999-2007
Authors: Pallé, E.; Goode, P. R.; Montañés-Rodríguez, P.
Bibcode: 2009JGRD..114.0D03P
Altcode: 2009JGRD..11400D03P
The overall reflectance of sunlight from Earth is a fundamental
parameter for climate studies. Recently, measurements of earthshine
were used to find large decadal variability in Earth's reflectance
of sunlight. However, the results did not seem consistent with
contemporaneous independent albedo measurements from the low Earth orbit
satellite, Clouds and the Earth's Radiant Energy System (CERES), which
showed a weak, opposing trend. Now more data for both are available,
all sets have been either reanalyzed (earthshine) or recalibrated
(CERES), and they present consistent results. Albedo data are also
available from the recently released International Satellite Cloud
Climatology Project flux data (FD) product. Earthshine and FD analyses
show contemporaneous and climatologically significant increases in
the Earth's reflectance from the outset of our earthshine measurements
beginning in late 1998 roughly until mid-2000. After that and to date,
all three show a roughly constant terrestrial albedo, except for the
FD data in the most recent years. Using satellite cloud data and Earth
reflectance models, we also show that the decadal-scale changes in
Earth's reflectance measured by earthshine are reliable and are caused
by changes in the properties of clouds rather than any spurious signal,
such as changes in the Sun-Earth-Moon geometry.
Title: Measurements of the Surface Brightness of the Earthshine with
Applications to Calibrate Lunar Flashes
Authors: Montañés-Rodríguez, Pilar; Pallé, Enric; Goode, P. R.
Bibcode: 2007AJ....134.1145M
Altcode:
We have used the large database of photometric observations of the
bright and dark portions of the face of the Moon from the Earthshine
Project at Big Bear Solar Observatory to determine the surface
brightness of the earthshine and its variations. Our purpose is to
make these observations appropriate for the calibration of lunar
flashes according to their magnitude. We have evaluated the daily,
seasonal, and annual changes in magnitude for our entire data set
and have also calibrated the surface brightness of the entire lunar
geography for several lunar phases by means of the observation of
lunar eclipses. We find variations between +12 and +17 mV
arcsec-2 with hourly changes upward of the order 0.25
mV arcsec-2, which are uniquely due to the
terrestrial meteorology. This rapid change in the terrestrial flux
reaching the Moon is usually neglected when calibrating the magnitude of
lunar impact events. We justify this using earthshine observations to
determine the brightness for the day, time, and selenographic location
of a given event in order to improve the accuracy of its brightness
calibration up to 0.25 mag.
Title: Shortwave forcing of the Earth's climate: Modern and historical
variations in the Sun's irradiance and the Earth's reflectance
Authors: Goode, P. R.; Pallé, E.
Bibcode: 2007JASTP..69.1556G
Altcode: 2007JATP...69.1556G
Changes in the Earth's radiation budget are driven by changes in the
balance between the thermal emission from the top of the atmosphere
and the net sunlight absorbed. The shortwave radiation entering
the climate system depends on the Sun's irradiance and the Earth's
reflectance. Often, studies replace the net sunlight by proxy measures
of solar irradiance, which is an oversimplification used in efforts to
probe the Sun's role in past climate change. With new helioseismic data
and new measures of the Earth's reflectance, we can usefully separate
and constrain the relative roles of the net sunlight's two components,
while probing the degree of their linkage. First, this is possible
because helioseismic data provide the most precise measure ever of the
solar cycle, which ultimately yields more profound physical limits on
past irradiance variations. Since irradiance variations are apparently
minimal, changes in the Earth's climate that seem to be associated
with changes in the level of solar activity—the Maunder Minimum
and the Little Ice age for example—would then seem to be due to
terrestrial responses to more subtle changes in the Sun's spectrum of
radiative output. This leads naturally to a linkage with terrestrial
reflectance, the second component of the net sunlight, as the carrier
of the terrestrial amplification of the Sun's varying output. Much
progress has also been made in determining this difficult to measure,
and not-so-well-known quantity. We review our understanding of these
two closely linked, fundamental drivers of climate.
Title: Sun's Direct and Indirect Role in Climate Change
Authors: Goode, P. R.
Bibcode: 2007AGUSMGP54A..02G
Altcode:
Broadly, the Earth's climate is driven by the Sun's output, the
Earth's reflectance and the Earth's thermal emission. Of these three
fundamental climate variables, the Earth's reflectance is the least
well-studied. In fact, variations in reflectance are being implicitly
ignored when solar cycle variables are treated as proxies for the
net sunlight reaching Earth. Variations in the solar irradiance have
been precisely measured for more than a quarter century combining
observations from various satellites, and here we review the physical
reasons why the Sun's irradiance variations over a solar cycle, as well
as over longer historical times have climatologically insignificant
variations. So, why are there terrestrial signatures of the solar cycle
in climate records, or periods like the Maunder Minimum corresponding
to times when the Sun was less active? If the variations of irradiance
over the most recent solar cycles were typical, then changes in the
net sunlight reaching Earth is a logical source of the terrestrial
signatures of solar variability. Here, the relevant component of the
net sunlight is the much less well-studied global reflectance of the
Earth. Small variations in the Sun's output could be amplified in the
much less well-studied terretrial albedo. We review our knowledge of
the Earth's reflectance from terrestrial measurements of the earthshine
and discuss future plans for measurements of terrestrial reflectance.
Title: Solar Constant or Terrestrial Reflectance -- Which Changes
More?
Authors: Goode, P. R.
Bibcode: 2007AGUSM.A51D..08G
Altcode:
The net energy reaching Earth varies over the solar cycle and longer
timescales. The net depends on the solar constant and terrestrial
reflectance, but which matters more for climate change? Here, we
review our current knowledge of variations of the solar constant
from ground-based observations, as well as helioseismic and other
satellite data. These place tight limits on the range of variability
of the historical Sun. On the other hand, earthshine measurements of
the Earth's reflectance over a solar cycle imply variations in net
energy deposition that are about an order of magnitude larger than
those resulting from the changing solar constant. Connections between
changes in the solar constant and Earth's reflectance will be discussed
to probe the origin of the terrestrial footprint of the solar cycle,
as well as the origin of periods like parts of the Maunder Minimum
when the Sun was less active and the Earth was cooler.
Title: Vegetation Signature in the Observed Globally Integrated
Spectrum of Earth Considering Simultaneous Cloud Data: Applications
for Extrasolar Planets
Authors: Montañés-Rodríguez, Pilar; Pallé, E.; Goode, P. R.;
Martín-Torres, F. J.
Bibcode: 2006ApJ...651..544M
Altcode: 2006astro.ph..4420M
A series of missions will be launched over the next few decades that
will be designed to detect and characterize extrasolar planets around
nearby stars. These missions will search for habitable environments and
signs of life (biosignatures) in planetary spectra. The vegetation's
``red edge,'' an enhancement in the Earth's spectrum near 700 nm when
sunlight is reflected from greenery, is often suggested as a tool
in the search for life in terrestrial-like extrasolar planets. Here,
through ground-based observations of the Earth's spectrum, satellite
observations of clouds, and an advanced atmospheric radiative-transfer
code, we determine the temporal evolution of the vegetation signature
of Earth. We find a strong correlation between the evolution of
the spectral intensity of the red edge and changes in the cloud-free
vegetated area over the course of observations. This relative increase
for our single day corresponds to an apparent reflectance change of
about 0.0050+/-0.0005 with respect to the mean albedo of 0.25 at 680 nm
(2.0%+/-0.2%). The excellent agreement between models and observations
motivated us to probe more deeply into the red-edge detectability
using real cloud observations at longer timescales. Overall, we
find the evolution of the red-edge signal in the globally averaged
spectra to be weak, and only attributable to vegetation changes when
the real land and cloud distributions for the day are known. However,
it becomes prominent under certain Sun-Earth-Moon orbital geometries
that are applicable to the search for life in extrasolar planets. Our
results indicate that vegetation detection in Earth-like planets will
require a considerable level of instrumental precision and will be a
difficult task, but not as difficult as the normally weak earthshine
signal might seem to suggest.
Title: First Light of the Near-Infrared Narrow-Band Tunable
Birefringent Filter at Big Bear Solar Observatory
Authors: Cao, Wenda; Hartkorn, Klaus; Ma, Jun; Xu, Yan; Spirock, Tom;
Wang, Haimin; Goode, Philip R.
Bibcode: 2006SoPh..238..207C
Altcode: 2006SoPh..tmp...53C
We discuss a near-infrared (NIR) narrow-band tunable birefringent
filter system newly developed by the Big Bear Solar Observatory
(BBSO). This is one of the first narrow-bandpass NIR filter systems
working at 1.56 μm which is used for the observation of the deepest
solar photosphere. Four stages of calcite were used to obtain a bandpass
of 2.5 Å along with a free spectral range (FSR) of 40 Å. Some unique
techniques were implemented in the design, including liquid crystal
variable retarders (LCVRs) to tune the bandpass in a range of ±100 Å,
a wide field configuration to provide up to 2° incident angle, and
oil-free structure to make it more compact and handy. After performing
calibration and characteristic evaluation at the Evans Facility of
the National Solar Observatory at Sacramento Peak (NSO/SP), a series
of high-resolution filtergrams and imaging polarimetry observations
were carried out with the Dunn Solar Telescope of NSO/SP and the
65-cm telescope of BBSO, in conjunction with the high-order adaptive
optics system and the Fabry-Pérot Interferometer (FPI). In this
paper, we describe the optical design and discuss the calibration
method. Preliminary observations show that it is capable of serving as
either a stand-alone narrow-band filter for NIR filtergram observations
or an order-sorting filter of a FPI applied to NIR two-dimensional
imaging spectro-polarimetry.
Title: Spectroscopy Of The Earth Observed As A Distant Planet
Authors: Montanes-Rodriguez, Pilar; Palle, E.; Goode, P. R.
Bibcode: 2006DPS....38.0405M
Altcode: 2006BAAS...38..487M
Since the discovery of the first planet outside the solar system,
the number of planet detections is increasing exponentially. Although
we have not been capable of detecting and exploring planets like our
own yet, challenging space missions are already being planned for
the next decades, and the discovery of earth-like planets is only a
matter of time. When the time arrives, one of our main concerns will
be to determine their degree of similarity with our own planet, and to
answer a more intriguing question for the humankind: if there is life on
them. An indication of complex life is the vegetation's red edge. Using
real cloud cover observations from satellite, we have unequivocally
detected the vegetation's signature in the Earth's globally averaged
spectrum. The signature is stronger when large vegetated regions of
the Earth are seen free of clouds. Our results show that, considering
the real cloud cover present in our planet, previous estimates of the
vegetation signal strength were over-optimistic.
Title: Progress on the 1.6-meter New Solar Telescope at Big Bear
Solar Observatory
Authors: Denker, C.; Goode, P. R.; Ren, D.; Saadeghvaziri, M. A.;
Verdoni, A. P.; Wang, H.; Yang, G.; Abramenko, V.; Cao, W.; Coulter,
R.; Fear, R.; Nenow, J.; Shoumko, S.; Spirock, T. J.; Varsik, J. R.;
Chae, J.; Kuhn, J. R.; Moon, Y.; Park, Y. D.; Tritschler, A.
Bibcode: 2006SPIE.6267E..0AD
Altcode: 2006SPIE.6267E..10D
The New Solar Telescope (NST) project at Big Bear Solar Observatory
(BBSO) now has all major contracts for design and fabrication in place
and construction of components is well underway. NST is a collaboration
between BBSO, the Korean Astronomical Observatory (KAO) and Institute
for Astronomy (IfA) at the University of Hawaii. The project will
install a 1.6-meter, off-axis telescope at BBSO, replacing a number
of older solar telescopes. The NST will be located in a recently
refurbished dome on the BBSO causeway, which projects 300 meters into
the Big Bear Lake. Recent site surveys have confirmed that BBSO is
one of the premier solar observing sites in the world. NST will be
uniquely equipped to take advantage of the long periods of excellent
seeing common at the lake site. An up-to-date progress report will
be presented including an overview of the project and details on the
current state of the design. The report provides a detailed description
of the optical design, the thermal control of the new dome, the optical
support structure, the telescope control systems, active and adaptive
optics systems, and the post-focus instrumentation for high-resolution
spectro-polarimetry.
Title: Diffraction-limited Polarimetry from the Infrared Imaging
Magnetograph at Big Bear Solar Observatory
Authors: Cao, Wenda; Jing, Ju; Ma, Jun; Xu, Yan; Wang, Haimin; Goode,
Philip R.
Bibcode: 2006PASP..118..838C
Altcode:
The Infrared Imaging Magnetograph (IRIM) system developed by Big Bear
Solar Observatory (BBSO) has been put into preliminary operation. It is
one of the first imaging spectropolarimeters working at 1565 nm and is
used for the observations of the Sun at its opacity minimum, exposing
the deepest photospheric layers. The tandem system, which includes a
4.2 nm interference filter, a unique 0.25 nm birefringent Lyot filter,
and a Fabry-Pérot etalon, is capable of providing a bandpass as low as
0.01 nm in a telecentric configuration. A fixed quarter-wave plate and
a nematic liquid crystal variable retarder are employed for analyzing
the circular polarization of the Zeeman components. The longitudinal
magnetic field is measured for the highly Zeeman-sensitive Fe I line
at 1564.85 nm (Landé factor g=3). The polarimetric data were taken
through a field of view of ~145''×145'' and
were recorded by a 1024×1024 pixel, 14 bit HgCdTe CMOS focal plane
array camera. Benefiting from the correlation tracking system and a
newly developed adaptive optics system, the first imaging polarimetric
observations at 1565 nm were made at the diffraction limit on 2005 July
1 using BBSO's 65 cm telescope. After comparing the magnetograms from
IRIM with those taken by the Michelson Doppler Imager on board SOHO,
it was found that all the magnetic features matched very well in both
sets of magnetograms. In addition, Stokes V profiles obtained from the
Fabry-Pérot etalon scan data provide access to both the true magnetic
field strength and the filling factor of the small-scale magnetic
flux elements. In this paper, we present the design, fabrication, and
calibration of IRIM, as well as the results of the first scientific
observations.
Title: The first light of the Infrared Imaging Magnetographat Big
Bear Solar Observatory
Authors: Cao, Wenda; Ma, J.; Jing, J.; Xu, Y.; Denker, C.; Wang, H.;
Goode, P.
Bibcode: 2006SPD....37.0612C
Altcode: 2006BAAS...38..227C
The InfraRed Imaging Magnetograph (IRIM) system developed by Big Bear
Solar Observatory (BBSO) has been put into preliminary operation. It
is one of the first imaging spectro-polarimeters working at 1565 nm,
and is used for the observations of the Sun at its opacity minimum,
exposing the deepest photospheric layers. The tandem system of a 4.2 nm
interference filter, an unique 0.25 nm birefringent Lyot filter and a
Fabry-Perot etalon is capable of providing a bandpass as low as 0.01
nm in a telecentric configuration. A fixed quarter wave plate and a
nematic liquid crystal variable retarder are employed for analyzing
the circular polarization of the Zeeman components. The longitudinal
magnetic field is measured for highly Zeeman-sensitive Fe I line at
1564.85 nm (Lande factor g = 3). The polarimetric data, with a field of
view (FOV) 145" × 145", were recorded by a 1024 × 1024 pixel, 14-bit
HgCdTe CMOS focal plane array camera. Benefiting from the Correlation
Tracking system (CT) and newly developed Adaptive Optics (AO) system,
the first imaging polarimetric observations at 1565 nm were made at the
diffraction limit on 1 July 2005 using BBSO's 65 cm telescope. After
comparing the magnetograms from IRIM with those taken by the Michelson
Doppler Imager (MDI) on board SOHO, it was found that all the magnetic
features matched very well in both sets of magnetograms. Also, Stokes
V profiles obtained from the Fabry-Perot etalon scanning data provide
access to both the true magnetic field strength and filling factor of
the small-scale magnetic flux elements. In this paper, we present the
design, fabrication, and calibration of IRIM, as well as the results
of the first scientific observations.
Title: Progress in the 1.6 m New Solar Telescope in Big Bear
Authors: Goode, Philip R.; NST Team
Bibcode: 2006SPD....37.3701G
Altcode:
Progress in building the NST (New Solar Telescope) will be reported. The
NST is a 1.6 m clear aperture, off-axis solar telescope. The telescope
is scheduled to see first light at Big Bear Solar Observatory (BBSO)
in April 2007, and is a joint effort of BBSO, the University of Hawaii,
the Korea Astronomy & Space Science Institute and the University of
Arizona.The telescope is off-axis to optimize low-contrast imaging, and
will have a 3 arcminute field of view. Figuring and testing the figure
of the large off-axis primary mirror presented unique problems. The NST
(New Solar Telescope) will have wavefront sensor controlled, real-time
active optics, and its light will feed BBSO's adaptive optics system,
which in turn feeds infrared and visible light Fabry-Perot based
polarimeters, as well as a real-time image processing system utilizing
parallel processing.The NST replaces the current 0.6 m solar telescope
at BBSO, and required a new, larger, vented dome with new thermal and
telescope control systems.The complementary value of the telescope
for upcoming space missions, such as SOLAR-B, STEREO and SDO will
be discussed.
Title: Robotic Earthshine Telescope
Authors: Goode, P.; Fear, R.; Nenow, J.; Spirock, T.
Bibcode: 2006AGUSM.A43D..15G
Altcode:
First results are reported from a robotic earthshine telescope. The
refracting telescope alternatively records the bright (moonshine)
and dark (earthshine) parts of the lunar face. It is the ratio of
the earthshine to moonshine from which the Earth's reflectance is
determined. Telescope design trade-offs are discussed. The novel
parts of the telescope include an automated rotating/translating
stage to block the moonshine when the earthshine is being measuring;
the telescope also functions like a coronagraph to minimize stray
light. Calibration of the robotic telescope against manually operated
telescopes is discussed. This is an essential step before deploying
a global network of earthshine robots.
Title: Sunshine, Earthshine and Climate
Authors: Goode, P.; Palle, E.; Montanes-Rodriguez, P.
Bibcode: 2006cosp...36.1446G
Altcode: 2006cosp.meet.1446G
Changes in the Earth s climate depend most basically on changes in the
Sun s output the Earth s reflectance and greenhouse gasses Using SoHO
helioseismic data a meaningful lower limit is found on solar irradiance
that implies the historical Sun can t be dimmer than the present Sun
Further the global earthshine photometric data from BBSO are used and
connected to cloud data to determine variations in the net sunlight
reaching Earth These suggest a significant decadal variation in the
net sunlight reaching Earth Spectroscopic earthshine data from Palomar
and NASA s IRTF tell us about the evolution of global greenhouse gasses
Title: The High Resolution 1.6 m Off-Axis Solar Telescope for BBSO -
The NST
Authors: Goode, P.
Bibcode: 2006cosp...36.1444G
Altcode: 2006cosp.meet.1444G
Progress in building the NST New Solar Telescope will be reported The
NST is a 1 6 m clear aperture off-axis solar telescope The telescope
is scheduled to see first light at Big Bear Solar Observatory BBSO in
April 2007 and is a joint effort of BBSO the University of Hawaii the
Korea Astronomy Space Science Institute and the University of Arizona
The telescope is off-axis to optimize low-contrast imaging and will
have a 3 arcminute field of view Figuring and testing the figure of
the large off-axis primary mirror presented unique problems The NST New
Solar Telescope will have wavefront sensor controlled real-time active
optics and its light will feed BBSO s adaptive optics system which in
turn feeds infrared and visible light Fabry-Perot based polarimeters
as well as a real-time image processing system utilizing parallel
processing The NST replaces the current 0 6 m solar telescope at BBSO
and required a new larger vented dome with new thermal and telescope
control systems The complementary value of the telescope for upcoming
space missions such as SOLAR-B STEREO and SDO will be discussed
Title: Lower Limit on Solar Irradiance Variation
Authors: Goode, P. R.
Bibcode: 2005AGUFMSH41A1109G
Altcode:
Helioseismic data reveal that the historical Sun cannot be any dimmer
than it is now at activity minimum. Changes in the frequencies of solar
oscillations are the most precise probe of irradiance variations over
the solar cycle. Using MDI data, Dziembowski and Goode (2005) showed
that f-mode changes arise from the direct effect of the evolving
magnetic activity, while p-mode changes are due to small, activity
induced changes in convective flows very near to the solar surface
(turbulent pressure). The f-modes also sharply limit the allowed field
growth with activity, and the limit is consistent with the observations
of Lin and Rimmele (1999). Combining MDI data with BBSO Ca II K, we
find the Sun is smooth at activity minimum and becomes increasingly
corrugated with rising activity. The overall physical picture is one in
which the Sun is hottest and smoothest at activity minimum, and becomes
cooler, more corrugated and irradiant with rising activity. Thus,
these results place a lower limit on irradiance variations, consistent
with current activity minima, and are roughly consistent with a picture
of Spruit (2000) and the behavior of faculae as reported by Berger et
al. (2005).
Title: The Visible--Light Magnetograph at the Big Bear Solar
Observatory: Hardware and Software
Authors: Shumko, S.; Abramenko, V.; Denker, C.; Goode, P.; Tritschler,
A.; Varsik, J.
Bibcode: 2005ASPC..347..509S
Altcode: 2005adass..14..509S
In this paper we report about the current status of the control and
acquisition software package developed to control the visible-light
imaging magnetograph (VIM) system at the Big Bear Solar Observatory
(BBSO). The instrument is designed to perform high-spatial and
high-temporal observations of the solar photosphere and chromosphere
utilizing the remodeled Coudé-feed of the 65 cm vacuum telescope.
Title: A Multi-Data Comparison of Shortwave Climate Forcing Changes
Authors: Palle, E.; Montanes-Rodriguez, P.; Goode, P. R.; Koonin,
S. E.; Wild, M.; Casadio, S.
Bibcode: 2005AGUFM.A43D0130P
Altcode:
Traditionally the earth's reflectance has been assumed to be roughly
constant, but large decadal variability, not reproduced by current
climate models, has been reported lately from a variety of sources. We
compare here the available datasets related to earth's reflectance,
in order to assess the observational constraints on the models. We find
a consistent picture among all datasets of an albedo decreased during
1985-2000 between 2-3 and 6-7 W/m2, which is highly climatologically
significant. The largest discrepancy among the datasets occurs
during 2000-2004, when several sets reveal an increasing trend in the
reflectance, while CERES observations show a steady decrease of about
2 W/m2. Additionally, analysis of the recently realeased ISCCP data
for 2000-2004 are presented. These later findings show a consistency
in long-term trends between earthshine reflectance measurements and
the global cloud properties and climate change.
Title: Earth's spectral albedo from 0.5 to 4.4 um
Authors: Montanes-Rodrig, P.; Palle, E.; Goode, P. R.; Koonin, S. E.
Bibcode: 2005AGUFMSA53B1175M
Altcode:
We have analyzed spectroscopic earthshine data to determine Earth's
nightly spectral albedos covering the visible, near and middle infrared
spectral ranges. Observations in the visible were undertaken from
Palomar Observatory with the spectrograph in the Palomar 60" telescope
and with the echelle spectrograph of the InfraRed Telescope Facility
(IRTF) on Mauna Kea in Hawaii. The observing runs were chosen near the
quarter moon to reduce the background glow produced by the moonshine
(bright side of the Moon). Although observations were taken on different
nights, the similarity of lunar phases and comparable cloud cover
conditions for the monitored part of the Earth's surface, allow us to
derive, for the first time, an apparent albedo of the Earth covering
the entire spectral range from 0.5 to 4.4 microns.
Title: A multi-data comparison of shortwave climate forcing changes
Authors: Pallé, E.; Montañés-Rodriguez, P.; Goode, P. R.; Koonin,
S. E.; Wild, M.; Casadio, S.
Bibcode: 2005GeoRL..3221702P
Altcode:
Traditionally the Earth's reflectance has been assumed to be roughly
constant, but large decadal variability, not reproduced by current
climate models, has been reported lately from a variety of sources. We
compare here the available data sets related to Earth's reflectance,
in order to assess the observational constraints on the models. We
find a consistent picture among all data sets of an albedo decreased
during 1985-2000 between 2-3 and 6-7 W/m2, which is highly
climatically significant. The largest discrepancy among the data sets
occurs during 2000-2004, when some present an increasing reflectance
trend, while CERES observations show a steady decrease of about 2
W/m2.
Title: Globally Integrated Measurements of the Earth's Visible
Spectral Albedo
Authors: Montañés-Rodriguez, P.; Pallé, E.; Goode, P. R.; Hickey,
J.; Koonin, S. E.
Bibcode: 2005ApJ...629.1175M
Altcode: 2005astro.ph..5084M
We report spectroscopic observations of the earthshine reflected from
the Moon. By applying our well-developed photometry methodology to
spectroscopy, we are able to precisely determine the Earth's reflectance
and its variation as a function of wavelength through a single night as
the Earth rotates. These data imply that planned regular monitoring of
earthshine spectra will yield valuable new inputs for climate models,
which would be complementary to those from the more standard broadband
measurements of satellite platforms. For our single night of reported
observations, we find that Earth's albedo decreases sharply with
wavelength from 500 to 600 nm, while being almost flat from 600 to
900 nm. The mean spectroscopic albedo over the visible is consistent
with simultaneous broadband photometric measurements. Unlike previous
reports, we find no evidence for either an appreciable ``red'' or
``vegetation'' edge in the Earth's spectral albedo, or for changes in
this spectral region (700-740 nm) over the 40° of Earth's rotation
covered by our observations. Whether or not the absence of a vegetation
signature in disk-integrated observations of the Earth is a common
feature awaits the analysis of more earthshine data and simultaneous
satellite cloud maps at several seasons. If our result is confirmed,
it would limit efforts to use the red edge as a probe for Earth-like
extrasolar planets. Water vapor and molecular oxygen signals in the
visible earthshine, and carbon dioxide and methane in the near-infrared,
are more likely to be powerful probes.
Title: Toward a global earthshine network: First results from two
stations
Authors: Pallé, E.; Goode, P. R.; Montañés-Rodriguez, P.; Koonin,
S. E.; Rumyantsev, V.
Bibcode: 2005GeoRL..3211803P
Altcode:
Big Bear Solar Observatory is building the world's first global
earthshine network to measure Earth's large-scale reflectance. Our first
remote station was deployed in late 2003 at the Crimean Astronomical
Observatory. Here we compare the data obtained from the two earthshine
stations, Crimea and Big Bear. We find that the retrieved quantities
from both stations are consistent and that the data may be easily
combined into a single data set expanding the temporal and geographical
coverage of our Earth reflectance measurements from California. We
also detail our plans and the expected coverage with a larger network
of stations.
Title: The New Solar Telescope at Big Bear Solar Observatory -
A Progress Report
Authors: Denker, C.; Cao, W.; Chae, J.; Coulter, R.; Kuhn, J. R.;
Marquette, W. H.; Moon, Y.; Park, Y.; Ren, D.; Tritschler, A.; Varsik,
J. R.; Wang, H.; Yang, G.; Shoumko, S.; Goode, P. R.
Bibcode: 2005AGUSMSP43A..07D
Altcode:
The New Solar Telescope (NST) is a new 1.6-meter, off-axis telescope
for the Big Bear Solar Observatory (BBSO) in California. The NST is
collaboration between BBSO, the Korean Astronomical Observatory (KAO)
and Institute for Astronomy (IfA) at the University of Hawaii. BBSO
is an ideal site for high-spatial resolution observations, since this
mountain-lake site provides consistent seeing conditions with extended
periods of excellent seeing from sunrise to sunset. These unique seeing
characteristics make BBSO ideally suited for combined high-resolution
campaigns and synoptic observations, which are essential for studies
of solar activity and space weather. In this progress report, we
present the latest information on the optical design, the optical
support structure, the telescope control system and the requisite
instrumentation for the telescope. Acknowledgements: This work has been
supported by NSF under grants ATM-0236945, ATM-0342560, MRI-0320540,
and Air Force DURIP F-49620-03-1-0271.
Title: Helioseismic Limits on Irradiance Variations
Authors: Goode, P. R.
Bibcode: 2005AGUSMSH22B..05G
Altcode:
Changes in the frequencies of solar oscillations are the most precise
probe of irradiance variations over the solar cycle. Using MDI data,
Dziembowski and Goode (2005) showed that f-mode changes arise from
the direct effect of the evolving magnetic activity, while p-mode
changes are due to small, activity induced changes in convective
flows very near to the solar surface (turbulent pressure). The
f-modes also sharply limit the allowed field growth with activity,
and the limit is consistent with the observations of Lin and Rimmele
(1999). Combining MDI data with BBSO Ca II K, we find the Sun is
smooth at activity minimum and becomes increasingly corrugated with
rising activity. The overall physical picture is one in which the Sun
is hottest and smoothest at activity minimum, and becomes cooler, more
corrugated and irradiant with rising activity. These results place a
lower limit on irradiance variations and are roughly consistent with
a picture of Spruit (2000).
Title: Sources of Oscillation Frequency Increase with Rising Solar
Activity
Authors: Dziembowski, W. A.; Goode, P. R.
Bibcode: 2005ApJ...625..548D
Altcode: 2005astro.ph..3266D
We analyze and interpret SOHO MDI data on oscillation frequency changes
between 1996 and 2004, focusing on differences between the activity
minimum and maximum of solar cycle 23. We study only the behavior of
the centroid frequencies, which reflect changes averaged over spherical
surfaces. Both the f-mode and p-mode frequencies are correlated with
general measures of the Sun's magnetic activity. However, the physics
behind each of the two correlations is quite different. We show
that for the f-modes the dominant cause of the frequency increase
is the dynamical effect of the rising magnetic field. The relevant
rise must occur in subphotospheric layers reaching to some 0.5-0.7
kG at a depth of about 5 Mm. However, the implied constraints also
require the field change in the atmosphere to be so small that it
has only a tiny dynamical effect on p-mode frequencies. For p-modes,
the most plausible explanation of the frequency increase is a less
than 2% decrease in the radial component of the turbulent velocity
in the outer layers. Lower velocity implies a lower efficiency of the
convective transport, hence lower temperature, which also contributes
to the p-mode frequency increase.
Title: High-Spatial-Resolution Imaging Combining High-Order Adaptive
Optics, Frame Selection, and Speckle Masking Reconstruction
Authors: Denker, Carsten; Mascarinas, Dulce; Xu, Yan; Cao, Wenda;
Yang, Guo; Wang, Haimin; Goode, Philip R.; Rimmele, Thomas
Bibcode: 2005SoPh..227..217D
Altcode:
We present, for the first time, high-spatial-resolution observations
combining high-order adaptive optics (AO), frame selection, and
post-facto image correction via speckle masking. The data analysis is
based on observations of solar active region NOAA 10486 taken with the
Dunn Solar Telescope (DST) at the Sacramento Peak Observatory (SPO) of
the National Solar Observatory (NSO) on 29 October 2003. The high Strehl
ratio encountered in AO corrected short-exposure images provides highly
improved signal-to-noise ratios leading to a superior recovery of the
object's Fourier phases. This allows reliable detection of small-scale
solar features near the diffraction limit of the telescope. Speckle
masking imaging provides access to high-order wavefront aberrations,
which predominantly originate at high atmospheric layers and are only
partially corrected by the AO system. In addition, the observations
provided qualitative measures of the image correction away from the
lock point of the AO system. We further present a brief inspection
of the underlying imaging theory discussing the limitations and
prospects of this multi-faceted image reconstruction approach in
terms of the recovery of spatial information, photometric accuracy,
and spectroscopic applications.
Title: Rapid Change of δ Spot Structure Associated with Seven
Major Flares
Authors: Liu, Chang; Deng, Na; Liu, Yu; Falconer, David; Goode,
Philip R.; Denker, Carsten; Wang, Haimin
Bibcode: 2005ApJ...622..722L
Altcode:
A large fraction of major flares occur in active regions that exhibit a
δ configuration. The formation and disintegration of δ configurations
is very important in understanding the evolution of photospheric
magnetic fields. In this paper we study the relationship between the
change in δ spot structures and associated major flares. We present
a new observational result that part of penumbral segments in the
outer δ spot structure decay rapidly after major flares; meanwhile,
the neighboring umbral cores and/or inner penumbral regions become
darker. Using white-light (WL) observations from the Transition Region
and Coronal Explorer (TRACE), we study the short-term evolution of δ
spots associated with seven major flares, including six X-class flares
and one M-class flare. The rapid changes, which can be identified in
the time profiles of WL mean intensity are permanent, not transient,
and thus are not due to flare emission. The co-aligned magnetic field
observations obtained with the Michelson Doppler Imager (MDI) show
substantial changes in the longitudinal magnetic field associated with
the decaying penumbrae and darkened central areas. For two events for
which vector magnetograms were available, we find that the transverse
field associated with the penumbral decay areas decreased while it
increased in the central darkened regions. Both events also show an
increase in the magnetic shear after the flares. For all the events,
we find that the locations of penumbral decay are related to flare
emission and are connected by prominent TRACE postflare loops. To
explain these observations, we propose a reconnection picture in which
the two components of a δ spot become strongly connected after the
flare. The penumbral fields change from a highly inclined to a more
vertical configuration, which leads to penumbral decay. The umbral
core and inner penumbral region become darker as a result of increasing
longitudinal and transverse magnetic field components.
Title: Traces of the Dynamic Current Sheet during a Solar Flare
Authors: Ji, Haisheng; Wang, Haimin; Goode, Philip R.; Jiang, Yunchun;
Yurchyshyn, V.
Bibcode: 2004ApJ...607L..55J
Altcode:
High-cadence and high-resolution time sequences of far Hα
off-band images provide a unique tool to study the evolution of
the fine structure of flare kernels. The fine structure contains
important information on flare topology and the triggering
mechanism. In this Letter, we concentrate on the rapid changes
of the relative positions of two conjugate flare footpoints. In
order to carry out this study with the highest physical precision,
we use rc=ΣrjIj/ΣIj
(Ij is the Hα brightness at rj) to compute the
centroid of an Hα bright kernel region caused by solar flares. Using
this, we probe the fine temporal structures connected to the distance
between the centroids of two conjugate kernels of an M2.3 flare. The
flare, which occurred on 2002 September 9 in NOAA Active Region 0105,
was observed at Big Bear Solar Observatory at the far off-band center
wavelength of H α-1.3 Å, with a cadence of ~40 ms. The flare was also
observed by RHESSI. The time profile of the separation distance shows
an excellent anticorrelation to that of the hard X-ray (HXR) emissions
in 25-50 keV, which exhibit a number of separate spikes (the linear
Pearson correlation coefficient is found to be ~-0.83). The separation
between the two centroids decreases at the rising periods of four HXR
spikes, then it increases after the peak time of the flare to show
the expected separation motion. The most obvious decreasing, which
occurred during the first HXR peak, was confirmed by corresponding
images. This implies that during the impulsive phases, the energy
transported from the corona is deposited increasingly inwardly between
the two kernels. This new and perhaps surprising tendency for the
energy deposition can be explained as being caused by current sheet
pinch motions, which, at the same time, enhance the magnetic energy
reconnection rate to produce the observed HXR spikes.
Title: Rapid Changes of Sunspot Structure Associated with Major
Flares in AR 10486
Authors: Liu, C.; Deng, N.; Qiu, J.; Goode, P. R.; Denker, C.; Wang, H.
Bibcode: 2004AAS...204.4705L
Altcode: 2004BAAS...36..737L
By tracing the change in TRACE white-light images, we find penumbral
segments decayed rapidly and permanently right after three X-class
solar flares. All of these three events occurred recently in NOAA
Active Region 10486, an X17 flare on 2003 October 28, an X10 flare
on 2003 October 29, and an X8.3 flare on 2003 November 2. For the X17
flare, the decaying penumbral segment is related to a section of one
of the two TRACE 1600Å ribbons, while for the X10 and X8.3 flares,
both to the 50-100 keV hard X-ray sources observed by RHESSI. We show
the changes of photospheric magnetic fields associated with these
penumbral decaying area by plotting the time profiles of magnetic flux
derived from MDI magnetograms. We also use the TRACE 195Å images to
understand the coronal environment. From all these observations, we
propose a possible explanation that magnetic fields change from a highly
inclined to a more vertical configuration after the flares, that is,
part of the penumbral magnetic field is converted into umbral fields.
Title: Changes in Earth's Reflectance over the Past Two Decades
Authors: Pallé, E.; Goode, P. R.; Montañés-Rodríguez, P.; Koonin,
S. E.
Bibcode: 2004Sci...304.1299P
Altcode:
We correlate an overlapping period of earthshine measurements of Earth's
reflectance (from 1999 through mid-2001) with satellite observations of
global cloud properties to construct from the latter a proxy measure
of Earth's global shortwave reflectance. This proxy shows a steady
decrease in Earth's reflectance from 1984 to 2000, with a strong
climatologically significant drop after 1995. From 2001 to 2003, only
earthshine data are available, and they indicate a complete reversal of
the decline. Understanding how the causes of these decadal changes are
apportioned between natural variability, direct forcing, and feedbacks
is fundamental to confidently assessing and predicting climate change.
Title: The New Solar Telescope at Big Bear Solar Observatory
Authors: Denker, C.; Marquette, W. H.; Varsik, J.; Wang, H.; Goode,
P. R.; Moretto, G.; Kuhn, J.; Coulter, R.
Bibcode: 2004AAS...204.6908D
Altcode: 2004BAAS...36R.795D
The New Solar Telescope (NST) at Big Bear Solar Observatory is
the replacement of the current 65 cm vacuum telescope. We present
the optical design of this novel off-axis telescope with a 1.6 m
clear aperture. The NST has been designed to exploit the excellent
seeing conditions at a lake-site observatory and provide data with a
spatial resolution close the telescope's diffraction limit from the
visible to the near-infrared (NIR) wavelength region. The post-focus
instrumentation is located in the Coudé-room, a new optical laboratory
below the observing floor, which also hosts a high-order adaptive optics
system. The main instruments are two imaging spectro-polarimeters for
visible and NIR observations and a real-time image reconstruction system
for visible-light multi-color photometry. This unique combination of
instruments will realize its full potential in the studies of active
region evolution and space weather forecasts.
Title: Observation of current sheet pinch in a solar flare
Authors: Ji, H.; Wang, H.; Goode, P. R.
Bibcode: 2004AAS...204.2702J
Altcode: 2004BAAS...36..693J
High-cadence and high-resolution time sequences of far H-alpha off-band
images provide a unique tool to study the evolution of the fine
structure of flare kernels. The fine structure contains important
information on flare topology and the triggering mechanism. In
this paper, we concentrate on the rapid changes of the relative
positions of two conjugate flare footpoints. In order to carry out
this study with the highest physical precision, we use rc
= Σ rj Ij / Σ Ij (Ij
is the H-alpha brightness at rj) to compute the centroid of
an H-alpha bright kernel region caused by solar flares. Using this, we
probe the fine temporal structures connected to the distance between the
centroids of two conjugate kernels of an M2.3 flare. The flare, which
occurred on 2002 September 9 in active region NOAA 0105, was observed at
Big Bear Solar Observatory (BBSO) at the far off-band center wavelength
of H-alpha - 1.3 Å, with a cadence of ∼ 40 ms. The flare was also
observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager
(RHESSI). The time profile of the separation distance shows an excellent
anti-correlation to that of the hard X-ray (HXR) emissions in 25 -
50 keV, which exhibit a number of separate spikes (The linear Pearson
correlation coefficient is found to be ∼ -0.83). The separation
between the two centroids decreases at the rising periods of four HXR
spikes, then it increases after the peak time of the flare to show
the expected separation motion. The most obvious decreasing, which
occurred during the first HXR peak, was confirmed by corresponding
images. This implies that during the impulsive phases, the energy
transported from the corona is deposited increasingly inwardly between
the two kernels. This new, and perhaps surprising tendency for the
energy deposition can be explained as being caused by current sheet
pinch motions, which, at the same time, enhance the magnetic energy
reconnection rate to produce the observed HXR spikes.
Title: Optical design for a new off-axis 1.7-m solar telescope (NST)
at Big Bear
Authors: Didkovsky, Leonid V.; Kuhn, Jeff R.; Goode, Philip R.
Bibcode: 2004SPIE.5171..333D
Altcode:
An optical design for a modern off-axis 1.6 m clear aperture solar
telescope - the NST (New Solar Telescope) is presented. The NST will
replace the 65 cm vacuum telescope at Big Bear Solar Observatory
(BBSO)in 2006. A high-order Adaptive optics (AO) system will deliver
light to the current and planned complement of BBSO instrumentation. The
NST will fully utilize the optical and dynamical range advantages of
its unobstructed (off-axis) pupil.
Title: Characteristic evaluation of a near-infrared Fabry-Perot
filter for the InfraRed Imaging Magnetograph (IRIM)
Authors: Cao, Wenda; Denker, Carsten J.; Wang, Haimin; Ma, J.; Qu,
M.; Wang, Jinshan; Goode, Philip R.
Bibcode: 2004SPIE.5171..307C
Altcode:
The InfraRed Imaging Magnetograph (IRIM) is a high temporal
resolution, high spatial resolution, high spectral resolving power,
and high magnetic sensitivity solar two-dimensional narrow-band
spectro-polarimeter working in the near infrared from 1.0 μm to
1.7 μm at Big Bear Solar Observatory (BBSO). It consists of an
interference filter, a polarization analyzer, a birefringent filter,
and a Fabry-Perot etalon. As the narrowest filter of IRIM, the infrared
Fabry-Perot plays a very important role in achieving the narrow band
transmission of ~ 10 pm and high throughput between 85% and 95% for
the full wavelength range, maintaining wavelength tuning ability
from 1.0 to 1.7 μm, and assuring stability and reliability. As
the third of a series of publications describing IRIM, this paper
outlines a set of methods to evaluate the near infrared Fabry-Perot
etalon. Two-dimensional characteristic maps of the near infrared
Fabry-Perot etalon, including the bandpass ▵λ, effective finesse
Feff, peak transmission τmax, along with a free
spectral range, flatness, roughness, and stability and repeatability
were obtained with laboratory equipment. These measured results will
benefit the optimization of IRIM design and observational mode of
the future.
Title: First results from the NSO/NJIT solar adaptive optics system
Authors: Rimmele, Thomas R.; Richards, Kit; Hegwer, Stephen; Fletcher,
Stephen; Gregory, Scott; Moretto, Gilberto; Didkovsky, Leonid V.;
Denker, Carsten J.; Dolgushin, Alexander; Goode, Philip R.; Langlois,
Maud; Marino, Jose; Marquette, William
Bibcode: 2004SPIE.5171..179R
Altcode:
The National Solar Observatory and the New Jersey Institute of
Technology have developed two 97 actuator solar adaptive optics
(AO) systems based on a correlating Shack-Hartmann wavefront sensor
approach. The first engineering run was successfully completed
at the Dunn Solar Telescope (DST) at Sacramento Peak, New Mexico
in December 2002. The first of two systems is now operational at
Sacramento Peak. The second system will be deployed at the Big Bear
Solar Observatory by the end of 2003. The correlating Shack-Hartmann
wavefront sensor is able to measure wavefront aberrations for
low-contrast, extended and time-varying objects, such as solar
granulation. The 97-actuator solar AO system operates at a loop
update rate of 2.5 kHz and achieves a closed loop bandwidth (0dB
crossover error rejection) of about 130 Hz. The AO system is capable
of correcting atmospheric seeing at visible wavelengths during median
seeing conditions at both the NSO/Sacramento Peak site and the Big Bear
Solar Observatory. We present an overview of the system design. The
servo loop was successfully closed and first AO corrected images were
recorded. We present first results from the new, high order AO system.
Title: Rapid Penumbral Decay following Three X-Class Solar Flares
Authors: Wang, H.; Liu, C.; Qiu, J.; Deng, N.; Goode, P. R.; Denker, C.
Bibcode: 2004ApJ...601L.195W
Altcode:
We show strong evidence that penumbral segments decayed rapidly and
permanently right after three X-class solar flares. Two of the three
events occurred very recently in NOAA Active Region 10486, an X17
flare on 2003 October 28 and an X10 flare on 2003 October 29. The
third X2.3 flare was observed in solar active region NOAA AR 9026 on
2000 June 6. The locus of penumbral decay is related to flare emission,
albeit with distinct differences for each event. We present difference
images highlighting the rapid changes between pre- and postflare states
of the flaring active region, which show distinct decaying penumbral
segments and neighboring umbral cores becoming darker. Because of the
lack of spectroscopic data, we cannot exclude the possibility that
the observed changes are due to changes in the temperature structure
of the flaring atmosphere, or to a corresponding reduction in opacity
for a section of both umbra and penumbra. However, we argue against
this possibility because the observed intensity changes are permanent,
not transient. We instead propose a possible explanation that magnetic
fields change from a highly inclined to a more vertical configuration
within approximately 1 hr after the flares; i.e., part of the penumbral
magnetic field is converted into umbral fields.
Title: The earthshine spectrum
Authors: Montañés Rodriguez, P.; Pallé, E.; Goode, P. R.; Hickey,
J.; Qiu, J.; Yurchyshyn, V.; Chu, M. C.; Kolbe, E.; Brown, C. T.;
Koonin, S. E.
Bibcode: 2004AdSpR..34..293M
Altcode:
Since 1998 the Earthshine Project has been a collaborative effort
between Big Bear Solar Observatory/New Jersey Institute of Technology
and California Institute of Technology. Cyclic spectroscopic
observations of the dark and bright sides of the moon (or earthshine
and moonshine, respectively) have been carried out in the visible
region at Palomar Observatory. From these data, the ratio of the
earthshine to moonshine characterizes the globally averaged Earth's
spectrum. Information concerning the search for extra-solar, terrestrial
planets can be also obtained from these observations.
Title: Helioseismic Probing of Solar Variability: The Formalism and
Simple Assessments
Authors: Dziembowski, W. A.; Goode, P. R.
Bibcode: 2004ApJ...600..464D
Altcode: 2003astro.ph.10095D
We derive formulae connecting the frequency variations in the spectrum
of solar oscillations to the dynamical quantities that are expected to
change over the solar activity cycle. This is done for both centroids
and the asymmetric part of the fine structure (so-called even-a
coefficients). We consider the near-surface, small-scale magnetic
and turbulent velocity fields, as well as horizontal magnetic fields
buried near the base of the convective zone. For the centroids we
also discuss the effect of temperature variation. We demonstrate that
there is a full, one-to-one correspondence between the expansion
coefficients of the fine structure and those of both the averaged
small-scale velocity and magnetic fields. Measured changes in the
centroid frequencies and the even-a coefficients over the rising
phase solar cycle may be accounted for by a decrease in the turbulent
velocity of order 1%. We show that the mean temperature decrease
associated with the net decrease in the efficiency of convective
transport may also significantly contribute to the increase of the
centroid frequencies. Alternatively, the increase may be accounted
for by an increase of the small-scale magnetic field of order 100 G,
if the growing field is predominantly radial. We also show that global
seismology can be used to detect a field at the level of a few times
105 G, if such a field were present and confined to a thin
layer near the base of the convective envelope.
Title: The Earthshine Project: update on photometric and spectroscopic
measurements
Authors: Pallé, E.; Montañés Rodriguez, P.; Goode, P. R.; Qiu,
J.; Yurchyshyn, V.; Hickey, J.; Chu, M. -C.; Kolbe, E.; Brown, C. T.;
Koonin, S. E.
Bibcode: 2004AdSpR..34..288P
Altcode:
The Earthshine Project is a collaborative effort between Big Bear
Solar Observatory (New Jersey Institute of Technology) and the
California Institute of Technology. Our primary goal is the precise
determination of a global and absolutely calibrated albedo of the Earth
and the characterization of its synoptic, seasonal and inter-annual
variability. Photometric observations of the Earth's reflectance have
been regularly carried out during the past 4 years. The up-to-date
synoptic, seasonal and long-term variation in the Earth's albedo
are reported in this paper, together with a comparison to model
albedos using modern cloud satellite data and Earth Radiation Budget
Experiment scene models. The Earth's albedo has a major role in
determining the Earth's climate. The possibility of a response of
this parameter to solar activity is also discussed. Simultaneously,
spectrometric observations of the earthshine have been carried out
at Palomar Observatory. The main goals and first results of those
observations are also presented.
Title: The New 1.7 m Off-Axis Solar Telescope (NST) Project: a Path
to Better Solar Science
Authors: Goode, P. R.; Didkovsky, L. V.; Kuhn, J.
Bibcode: 2003AGUFMSH42B0532G
Altcode:
Big Bear Solar Observatory (BBSO) of New Jersey Institute of Technology
is upgrading its 65 cm aperture vacuum telescope with a modern, off-axis
1.6 m clear aperture instrument - New Solar Telescope (NST). The NST
offers a significant incremental improvement in ground-based infrared
and visible light high angular resolution capabilities. It will fully
utilize the optical and dynamical range advantages of its unobstructed
(off-axis) pupil. The NST enhances our continuing program to understand
photospheric magneto-convection and chromospheric dynamics. This
new telescope will be the largest aperture solar telescope, and the
largest aperture off-axis telescope located in one of the best observing
sites. It will enable new, cutting edge science.
Title: Signature of an Avalanche in Solar Flares as Measured by
Photospheric Magnetic Fields
Authors: Abramenko, V. I.; Yurchyshyn, V. B.; Wang, H.; Spirock,
T. J.; Goode, P. R.
Bibcode: 2003ApJ...597.1135A
Altcode:
We analyzed time variations of turbulent parameters of the photospheric
magnetic field of four active regions obtained during the course of
major solar flares using longitudinal magnetograms from the Big Bear
Solar Observatory and from SOHO/MDI full-disk measurements. Analysis of
the data indicated that, before each flare, the degree of intermittency
of the magnetic field had been increasing for 6-33 minutes and reached
a maximum value approximately 3-14 minutes before the peak of the
hard X-ray emission for each event. This result seems to suggest the
existence in an active region of a turbulent phase prior to a solar
flare. We also found that the maximum of the correlation length of
the magnetic energy dissipation field tends to follow (or to occur
nearly simultaneously) with the peak of the hard X-ray emission. The
data suggest that the peak in the correlation length might be a trace
of an avalanche of coronal reconnection events. We discuss the results
in the framework of the concept of self-organized criticality.
Title: A New Method for Resolving the 180° Ambiguity in Solar
Vector Magnetograms
Authors: Moon, Y. -J.; Wang, Haimin; Spirock, Thomas J.; Goode, P. R.;
Park, Y. D.
Bibcode: 2003SoPh..217...79M
Altcode:
We present a new method to resolve the 180° ambiguity for solar
vector magnetogram measurements. The basic assumption is that the
magnetic shear angle (Δθ), which is defined as the difference
between the azimuth components of observed and potential fields,
approximately follows a normal distribution. The new method is
composed of three steps. First, we apply the potential field method
to determine the azimuthal components of the observed magnetic
fields. Second, we resolve the ambiguity with a new criterion:
−90°+ΔθmpleΔθle90°+Δθmp, where
Δθmp is the most probable value of magnetic shear angle
from its number distribution. Finally, to remove some localized field
discontinuities, we use the criterion Bt⋅Bmtge0,
where Bt and Bmt are an observed transverse field
and its mean value for a small surrounding region, respectively. For
an illustration, we have applied the new ambiguity removal method
(Uniform Shear Method) to a vector magnetogram which covers a highly
sheared region near the polarity inversion line of NOAA AR 0039. As a
result, we have found that the new ambiguity solution was successful
and removed spatial discontinuities in the transverse vector fields
produced in the magnetogram by the potential field method. It is
also found that our solution to the ambiguity gives nearly the same
results, for highly sheared vector magnetograms and vertical current
density distributions, of NOAA AR 5747 and AR 6233 as those of other
methods. The validity of the basic assumption for an approximate normal
distribution is demonstrated by the number distributions of magnetic
shear angle for the three active regions under consideration.
Title: Small-Scale Hα Dynamic Features Supported by Chromo Spheric
Magnetic Reconnection
Authors: Lee, Sangwoo; Yun, Hong Sik; Chae, Jongchul; Goode, Philip R.
Bibcode: 2003JKAS...36S..21L
Altcode:
No abstract at ADS
Title: 1.6 M Solar Telescope in Big Bear -- The NST
Authors: Goode, Philip R.; Denker, Carsten. J.; Didkovsky, Leonid I.;
Kuhn, J. R.; Wang, Haimin
Bibcode: 2003JKAS...36S.125G
Altcode:
No abstract at ADS
Title: Sunshine, Earthshine and Climate Change I. Origin of, and
Limits on Solar Variability
Authors: Goode, Philip R.; Dziembowski, W. A.
Bibcode: 2003JKAS...36S..75G
Altcode:
No abstract at ADS
Title: The Sun from Big Bear
Authors: Goode, Philip R.; Denker, Carsten; Wang, Haimin
Bibcode: 2003ASSL..288..137G
Altcode: 2003ASSL..287..437G
No abstract at ADS
Title: Sunshine, Earthshine and Climate Change: II. Solar Origins
of Variations in the Earth's Albedo
Authors: Goode, P. R.; Pallé, E.; Yurchyshyn, V.; Qiu, J.; Hickey,
J.; Rodriguez, P. Montañés; Chu, M. -C.; Kolbe, E.; Brown, C. T.;
Koonin, S. E.
Bibcode: 2003JKAS...36S..83G
Altcode:
No abstract at ADS
Title: 1.6 m Off-Axis Solar Telescope at Big Bear Solar Observatory
Authors: Goode, P. R.; BBSO/NJIT Team; Mees Solar Obs. /U. Hawaii Team
Bibcode: 2003SPD....34.2025G
Altcode: 2003BAAS...35..848G
New Jersey Institute of Technology (NJIT), in collaboration with the
University of Hawaii (UH), is upgrading Big Bear Solar Observatory
(BBSO) by replacing its principal, 65 cm aperture telescope with
a modern, off-axis 1.6 m clear aperture instrument from a 1.7 m
blank. The new telescope offers a significant incremental improvement
in ground-based infrared and high angular resolution capabilities,
and enhances our continuing program to understand photospheric
magneto-convection and chromospheric dynamics. These are the drivers
for what is broadly called space weather -- an important problem,
which impacts human technologies and life on earth. This New Solar
Telescope (NST) will use the existing BBSO pedestal, pier and
observatory building, which will be modified to accept the larger
open telescope structure. It will be operated together with our 10
inch (for larger field-of-view vector magnetograms, Ca II K and Hα
observations) and Singer-Link (full disk Hα , Ca II K and white light)
synoptic telescopes. The NST optical and software control design will be
similar to the existing SOLARC (UH) and the planned Advanced Technology
Solar Telescope (ATST) facility led by the National Solar Observatory
(NSO) -- all three are off-axis designs. The highest resolution
solar telescopes currently operating are in the sub-meter class, and
have diffraction limits which allow them to resolve features larger
than 100 km in size on the sun. They are often photon-starved in the
study of dynamic events because of the competing need for diffraction
limited spatial resolution, short exposure times to minimize seeing
effects, and high spectral resolution to resolve line profiles. Thus,
understanding many significant and dynamic solar phenomena remains
tantalizingly close, but just beyond our grasp. Research supported
in part by NASA grant NAG5-12782 and NSF grant ATM-0086999.
Title: Signature of Avalanche in Solar Flares as Measured by
Photospheric Magnetic Fields
Authors: Abramenko, V. I.; Yurchyshyn, V. B.; Wang, H.; Spirock,
T. J.; Goode, P. R.
Bibcode: 2003SPD....34.1507A
Altcode: 2003BAAS...35..831A
Turbulent/fractal parameters of the longitudinal magnetic field,
Bz, for four powerful solar flares were analyzed utilizing
the correlation length, l, of the magnetic energy dissipation
field and the scaling exponent, b, which characterizes the measure
of intermittency of the Bz structure. We select a set of
four two-ribbon flares, which were followed by coronal mass ejections,
for the study of magnetic structure. During the course of each flare,
we found a peak in b which was followed by a peak in l in all of the
cases studied in this paper. These two peaks were separated by the time
interval tl during which a rapid growth of the soft X-ray
and Hα flux occurred. The peak in b was preceded by a time period
tb during which b increased gradually. For all of the flares
tb was longer than the time interval tl. The
maximum of l occurred nearly simultaneously, within an accuracy of
about 2-5 minutes, with the maximum of the hard X-ray emission. For
the four flares considered in this paper, we concluded that the more
impulsive and/or more powerful a flare is, the shorter the b growth
time, tb, and the l growth time, tl, are. In
the framework of the theory of non-linear dissipative processes,
these results may be interpreted as follows. Before a solar flare
occurs there is a significant increase in the number of magnetic field
discontinuities (b increasing), which is followed by an avalanche
(increase of the correlation length) of magnetic energy dissipation
events. The avalanche event occupies the entire active region from the
corona to the photosphere. Our study indicates that the more abrupt
is the avalanche, the stronger and/or more impulsive a flare is. The
time profiles of an avalanche is either Gaussian, which satisfies
the logistic avalanche model, or exponential with an abrupt drop,
which satisfies the exponential avalanche model. The driving time,
tb, was longer than the avalanching time, tl,
for all of the events. This qualitatively agrees with the requirements
of the self-organized criticality theory. This work was supported
by NSF-ATM 0076602, 0205157, 9903515 and NASA NAG5-12782 grants.
Title: High-Resolution Infrared Filter System for Solar Spectroscopy
and Polarimetry
Authors: Cao, W.; Ma, J.; Wang, J.; Goode, P. R.; Wang, H.; Denker, C.
Bibcode: 2003SPD....34.2013C
Altcode: 2003BAAS...35..846C
We report on the design of an imaging filter system working at the
near infrared (NIR) of 1.56 μ m to obtain monochromatic images
and to probe weak magnetic fields in different layers of the deep
photosphere with high temporal resolution and spatial resolution at
Big Bear Solar Observatory (BBSO). This filter system consists of
an interference filter, a birefringent filter, and a Fabry-Pérot
etalon. As the narrowest filter system, the infrared Fabry-Pérot
plays an important role in achieving narrow band transmission and
high throughput, maintaining wavelength tuning ability, and assuring
stability and reliability. In this poster, we outline a set of methods
for the evaluation and calibration of the near infrared Fabry-Pérot
etalon. Two-dimensional characteristic maps of the near infrared
Fabry-Pérot etalon, including full-width-at-half-maximum (FWHM),
effective finesse, peak transmission, along with free spectral range,
flatness, roughness, stability and repeatability were obtained with lab
equipments. Finally, by utilizing these results, a detailed analysis
of the filter performance for the Fe I 1.5648 μ m and Fe I 1.5652 μ
m Zeeman sensitive lines is presented. These results will benefit the
design of NIR spectro-polarimeter of Advanced Technology Solar Telescope
(ATST).
Title: The Earthshine Project: Measuring the earth's albedo. Latest
results
Authors: Palle, E.; Montanes Rodriguez, P.; Goode, P. R.; Koonin,
S. E.; Qiu, J.
Bibcode: 2003EAEJA.....7730P
Altcode:
Since December 1998, photometric observations of the bright and dark
side of the Moon have been regularly carried out at Big Bear Solar
Observatory, with the aim of determining a precise and absolutely
calibrated global albedo of the Earth. The up-to-date synoptic,
seasonal and long term variation in the Earth's albedo are reported in
this paper, toghether with comparison with modelled albedo using modern
cloud satellite data and Earth Radiation Budget Experiment (ERBE) scene
models. The Earth's albedo has a major role in determining the Earth's
climate. During the past 4 years, a significant increasing trend in
the averaged Earth's reflectance has been detected in the observational
data. More scarce data from 1994 and 1995 allow us to take a longer-term
look at the Earth's albedo variability and the possibility of a response
of this parameter to solar activity is discussed. Simultaneously,
spectroscopic observations of the earthshine have been carried out at
Palomar Observatory. First results and comparison between the spectral
and photometric observations are also being presented.
Title: The Earthshine Spectrum
Authors: Montanes Rodriguez, P.; Palle, E.; Goode, P. R.; Koonin,
S. E.; Qiu, J.
Bibcode: 2003EAEJA.....7948M
Altcode:
Since 1998 the Earthshine Project has been a collaborative effort
between Big Bear Solar Observatory/New Jersey Institute of Technology
and the California Institute of Technology. Cyclic spectroscopic
observations of the dark and bright sides of the moon (or earthshine
and moonshine respectively) have been carried out in the visible range
at Palomar Observatory. The ratio of the earthshine to moonshine spectra
characterizes the globally averaged Earth's spectrum. These observations
allow us to study global averaged column densities for several trace
and non-trace atmospheric components. Revelant information concerning
to the search of extra-solar, terrestrial-like planets can be also
obtained from these observations.
Title: Magnetic Helicity Pumping by Twisted Flux Tube Expansion
Authors: Chae, Jongchul; Moon, Y. -J.; Rust, D. M.; Wang, Haimin;
Goode, Philip R.
Bibcode: 2003JKAS...36...33C
Altcode:
No abstract at ADS
Title: Optical design of high-order adaptive optics for the NSO Dunn
Solar Telescope and the Big Bear Solar Observatory
Authors: Ren, Deqing; Hegwer, Steven L.; Rimmele, Thomas; Didkovsky,
Leonid V.; Goode, Philip R.
Bibcode: 2003SPIE.4853..593R
Altcode:
The National Solar Observatory (NSO) and the New Jersey Institute of
Technology are jointly developing high order solar Adaptive Optics (AO)
to be deployed at both the Dunn Solar Telescope (DST) and the Big Bear
Solar Telescope (BBST). These AO systems are expected to deliver first
light at the end of 2003. We discuss the AO optical designs for both
the DST and the BBST. The requirements for the optical design of the
AO system are as follows: the optics must deliver diffraction-limited
imaging at visible and near infrared over a 190"×190" field of
view. The focal plane image must be flat over the entire field of view
to accommodate a long slit and fast spectrograph. The wave-front sensor
must be able to lock on solar structure such as granulation. Finally,
the cost for the optical system must fit the limited budget. Additional
design considerations are the desired high bandwidth for tip/tilt
correction, which leads to a small, fast and off-the-shelf tilt-tip
mirror system and high throughput, i.e., a minimal number of optical
surfaces. In order to eliminate pupil image wander on the wave-front
sensor, both the deformable mirror and tip-tilt mirror are located on
the conjugation images of the telescope pupil. We discuss the details
of the optical design for the high order AO system, which will deliver
high resolution image at the 0.39 - 1.6 μm wavelength range.
Title: IRIM: An Imaging Magnetograph for High-Resoultion Solar
Observations in the Near-Infrared
Authors: Denker, Carsten J.; Ma, J.; Wang, Jingshan; Didkovsky,
Leonid V.; Varsik, John R.; Wang, Haimin; Goode, Philip R.
Bibcode: 2003SPIE.4853..223D
Altcode:
The InfraRed Imaging Magnetograph (IRIM) is an innovative magnetograph
system for near-infrared (NIR)observations of the Sun. IRIM will
provide high spatial resolution (0.2" per pixel image scale), high
temporal resolution (1-2 minutes), moderate spectral resolution
(14.0 pm), and high magnetic sensitivity covering a substantial
field-of-view (FOV: 170" circular). The bandpass of the instrument
is reduced in three steps while still providing high transmission:
(1) a 4 nm interference filter, (2) a 0.25 nm Lyot-filter, and (3)
a 14.0 pm tunable Fabry-Perot etalon. The innovative NIR Lyot-filter
was developed at the New Jersey Institute of Technology (NJIT) and
is currently being assembled at Cambridge Research Instruments. It is
the first of its kind and provides a large angle of acceptance, thus
solving many problems encountered with dual Fabry-Perot systems. The
two-dimensional line profiles will be recorded by a 1024 × 1024 pixel,
12-bit Complex Metal Oxide Semiconductor (CMOS) focal plane array (FPA)
manufactured by Rockwell Scientific Imaging, which can obtain images
at a rate of 50 fps. IRIM will utilize the remodelled Coude-feed of
the 65 cm vacuum telescope at the Big Bear Solar Observatory (BBSO)
and will benefit from an image stabilization and correction system of
independently operating Correlation Tracking (CT) and Adaptive Optics
(AO) systems.
Title: Foreword (Local and global helioseismology)
Authors: Goode, Philip R.; Rodriguez, Pilar Montanes; Varsik, John
Bibcode: 2003ESASP.517D...9G
Altcode: 2003soho...12D...9G
No abstract at ADS
Title: Solar adaptive optics: a progress report
Authors: Rimmele, Thomas R.; Richards, Kit; Hegwer, Steven L.; Ren,
Deqing; Fletcher, S.; Gregory, Scott; Didkovsky, Leonid V.; Denker,
Carsten J.; Marquette, William; Marino, J.; Goode, Philip R.
Bibcode: 2003SPIE.4839..635R
Altcode:
We present a progress report of the solar adaptive optics (AO)
development program at the National Solar Observatory (NSO) and the
Big Bear Solar Observatory (BBSO). Examples of diffraction-limited
observations obtained with the NSO low-order solar adaptive optics
system at the Dunn Solar Telescope (DST) are presented. The design
of the high order adaptive optics systems that will be deployed at
the DST and the BBSO is discussed. The high order systems will provide
diffraction-limited observations of the Sun in median seeing conditions
at both sites.
Title: High-order adaptive optical system for Big Bear Solar
Observatory
Authors: Didkovsky, Leonid V.; Dolgushyn, Alexander; Marquette,
William; Nenow, Jeff; Varsik, John; Goode, Philip R.; Hegwer, Steven
L.; Ren, Deqing; Fletcher, Steve; Richards, Kit; Rimmele, Thomas;
Denker, Carsten J.; Wang, Haimin
Bibcode: 2003SPIE.4853..630D
Altcode:
We present a high-order adaptive optical system for the 26-inch vacuum
solar telescope of Big Bear Solar Observatory. A small elliptical
tip/tilt mirror is installed at the end of the existing coude
optical path on the fast two-axis tip/tilt platform with its resonant
frequency around 3.3 kHz. A 77 mm diameter deformable mirror with 76
subapertures as well as wave-front sensors (correlation tracker and
Shack-Hartman) and scientific channels for visible and IR polarimetry
are installed on an optical table. The correlation tracker sensor
can detect differences at 2 kHz between a 32×32 reference frame
and real time frames. The WFS channel detects 2.5 kHz (in binned
mode) high-order wave-front atmosphere aberrations to improve solar
images for two imaging magnetographs based on Fabry-Perot etalons in
telecentric configurations. The imaging magnetograph channels may work
simultaneously in a visible and IR spectral windows with FOVs of about
180×180 arc sec, spatial resolution of about 0.2 arc sec/pixel and
SNR of about 400 and 600 accordingly for 0.25 sec integration time.
Title: Imaging magnetographs for high-resolution solar observations
in the visible and near-infrared wavelength region
Authors: Denker, C.; Didkovsky, L.; Ma, J.; Shumko, S.; Varsik, J.;
Wang, J.; Wang, H.; Goode, P. R.
Bibcode: 2003AN....324..332D
Altcode:
The Coudé feed of the vacuum telescope (aperture D=65 cm) at the Big
Bear Solar Observatory (BBSO) is currently completely remodelled to
accommodate a correlation tracker and a high-order Adaptive Optics (AO)
system. The AO system serves two imaging magnetograph systems located at
a new optical laboratory on the observatory's 2nd floor. The
InfraRed Imaging Magnetograph (IRIM) is an innovative magnetograph
system for near-infrared (NIR) observations in the wavelength region
from 1.0 mu m to 1.6 mu m. The Visible-light Imaging Magnetograph
(VIM) is basically a twin of IRIM for observations in the wavelength
range from 550 nm to 700 nm. Both instruments were designed for high
spatial and high temporal observations of the solar photosphere and
chromosphere. Real-time data processing is an integral part of the
instruments and will enhance BBSO's capabilities in monitoring solar
activity and predicting and forecasting space weather.
Title: Seeing Characteristic at a Lake-Site Observatory
Authors: Denker, C.; Didkovsky, L.; Marquette, W. H.; Goode, P. R.;
Venkateswaran, K.; Rimmele, T. R.
Bibcode: 2003ASPC..286...23D
Altcode: 2003ctmf.conf...23D
No abstract at ADS
Title: High-order adaptive optical system for Big Bear Solar
Observatory
Authors: Didkovsky, L. V.; Denker, C.; Goode, P. R.; Wang, H.; Rimmele,
T. R.
Bibcode: 2003AN....324..297D
Altcode:
A high-order Adaptive Optical (AO) system for the 65 cm vacuum telescope
of the Big Bear Solar Observatory (BBSO) is presented. The Coudé-exit
of the telescope has been modified to accommodate the AO system and two
imaging magnetograph systems for visible-light and near infrared (NIR)
observations. A small elliptical tip/tilt mirror directs the light into
an optical laboratory on the observatory's 2mathrm {nd}
floor just below the observing floor. A deformable mirror (DM) with
77 mm diameter is located on an optical table where it serves two
wave-front sensors (WFS), a correlation tracker (CT) and Shack-Hartman
(SH) sensor for the high-order AO system, and the scientific channels
with the imaging magnetographs. The two-axis tip/tilt platform has a
resonance frequency around 3.3 kHz and tilt range of about 2 mrad,
which corresponds to about 25'' in the sky. Based on
32 x 32 pixel images, the CT detects image displacements between a
reference frame and real-time frames at a rate of 2 kHz. High-order
wave-front aberrations are detected in the SH WFS channel from slope
measurements derived from 76 sub-apertures, which are recorded with
1,280 x 1,024 pixel Complex Metal Oxide Semiconductor (CMOS) camera
manufactured by Photobit camera. In the 4 x 4 pixel binning mode,
the data acquisition rate of the CMOS device is more than 2 kHz. Both
visible-light and NIR imaging magnetographs use Fabry-Pérot etalons in
telecentric configurations for two-dimensional spectro-polarimetry. The
optical design of the AO system allows using small aperture prefilters,
such as interference or Lyot filters, and 70 mm diameter Fabry-Pérot
etalons covering a field-of-view (FOV) of about 180''
x 180''.
Title: Sources of the Solar p- and F-Mode Frequency Variations
Authors: Dziembowski, Wojciech A.; Goode, Philip R.
Bibcode: 2003IAUJD..12E..23D
Altcode:
We have derived formulae connecting the frequency variations both
centroids and the asymmetric part of the fine structure (the even-a
coefficients) in the the spectrum of solar oscillations to the dynamical
quantities that are expected to change over the solar activity cycle. We
considered the near-surface small-scale magnetic and turbulent velocity
fields as well as horizontal magnetic fields buried near the base of
the convective zone. Measured changes in the centroid frequencies
and the even even-a's over the solar cycle may be accounted for by a
decrease in the turbulent velocity of order percent going from activity
minimum to maximum. Alternatively the changes may be accounted for
by an increase of the small-scale magnetic field of order 100 G if
the growing field is predominantly radial. Both sources are localized
near photosphere. We also show discuss seismic evidence for stronger
field in deep layers. Showing that that global seismology would detect
a field at the level of a fraction of MG if such a field were present
and confined to a thin layer near the base of the convective envelope
Title: A Flare-Triggered Heating of a Quiescent Filament
Authors: Ji, H. S.; Wang, H.; Spirock, T. J.; Qiu, J.; Yang, G.;
Goode, P. R.
Bibcode: 2002SoPh..211..221J
Altcode:
Using data obtained with the 20-cm Hα full-disk telescope at Big Bear
Solar Observatory and Fe xii 195 Å EIT on SOHO, we analyze a sudden
disappearance event of a quiescent filament in detail. The filament was
located along the common boundary of the active regions NOAA 9672 (S19
E13) and NOAA 9673 (N03 E18). The filament disappeared during a time
interval between 17:59 UT and 19:47 UT on 22 October 2001 immediately
after the onset of a major flare, which occurred in the active region
NOAA 9672. At about 23:23 UT of the same day, the filament began to
reappear in Hα and, after about 15 hours, the filament recovered to its
steady state with its size being slightly smaller than that before its
disappearance. This filament disappearance event belongs to the thermal
type of sudden filament disappearances, which is caused by an input
of additional heat. The heating mechanism that leads to sudden thermal
disappearances of quiescent filaments is still not well understood. This
simple event, due to the explicit cause and effect relationship between
the flare and the disappearance of the filament, shows us that the
flare triggered some kind of heating mechanism which continued several
hours. The heat may come from the flare via heat conduction from its
ribbon or from the excitation of dissipating Alfvén waves. However,
from the data analysis, we conclude that the flare triggered an in-situ
heating, which is likely caused by magnetic reconnection.
Title: Control and Acquisition Software for the Visible-Light
Fabry-Pérot Interferometer at the Big Bear Solar Observatory
Authors: Shumko, Sergiy; Denker, Carsten J.; Varsik, John; Didkovsky,
Leonid V.; Marquette, William; Goode, Philip R.; Wang, Haimin
Bibcode: 2002SPIE.4848..483S
Altcode:
We describe our progress in the development of a software package to
control a Fabry-Pérot interferometer (FPI) at the Big Bear Solar
Observatory (BBSO). The FPI is a key part of our new Visible-Light
Imaging Magnetograph (VIM). We describe the software libraries
and methods that we use to develop the software. We also present
specifications and characteristics of this new instrument.
Title: Rapid Changes of Magnetic Fields Associated with Six X-Class
Flares
Authors: Wang, Haimin; Spirock, Thomas J.; Qiu, Jiong; Ji, Haisheng;
Yurchyshyn, Vasyl; Moon, Yong-Jae; Denker, Carsten; Goode, Philip R.
Bibcode: 2002ApJ...576..497W
Altcode:
In this paper, we present the results of the study of six X-class
flares. We found significant changes in the photospheric magnetic
fields associated with all of the events. For the five events in 2001,
when coronagraph data were available, all were associated with halo
coronal mass ejections. Based on the analyses of the line-of-sight
magnetograms, all six events had an increase in the magnetic flux
of the leading polarity of order of a few times 1020 Mx
while each event had some degree of decrease in the magnetic flux
of the following polarity. The flux changes are considered impulsive
because the ``changeover'' time, which we defined as the time to change
from preflare to postflare state, ranged from 10 to 100 minutes. The
observed changes are permanent. Therefore, the changes are not due
to changes in the line profile caused by flare emissions. For the
three most recent events, when vector magnetograms were available,
two showed an impulsive increase of the transverse field strength
and magnetic shear after the flares, as well as new sunspot area in
the form of penumbral structure. One of the events in this study was
from the previous solar cycle. This event showed a similar increase
in all components of the magnetic field, magnetic shear, and sunspot
area. We present three possible explanations to explain the observed
changes: (1) the emergence of very inclined flux loops, (2) a change
in the magnetic field direction, and (3) the expansion of the sunspot,
which moved some flux out of Zeeman saturation. However, we have no
explanation for the polarity preference; i.e., the flux of leading
polarity tends to increase while the flux of following polarity tends
to decrease slightly.
Title: Scaling Behavior of Structure Functions of the Longitudinal
Magnetic Field in Active Regions on the Sun
Authors: Abramenko, V. I.; Yurchyshyn, V. B.; Wang, H.; Spirock,
T. J.; Goode, P. R.
Bibcode: 2002ApJ...577..487A
Altcode:
In the framework of a refined Kolmogorov hypothesis, the scaling
behavior of the Bz-component of the photospheric
magnetic field is analyzed and compared with flaring activity in
solar active regions. We use Solar and Heliospheric Observatory
Michelson Doppler Imager, Huairou (China), and Big Bear measurements
of the Bz-component in the photosphere for nine active
regions. We show that there is no universal behavior in the scaling
of the Bz-structure functions for different active
regions. Our previous study has shown that scaling for a given active
region is caused by intermittency in the field, ɛ(B)(x),
describing the magnetic energy dissipation. When intermittency is
weak, the Bz field behaves as a passive scalar in the
turbulent flow, and the energy dissipation is largely determined by
the dissipation of kinetic energy in the active regions with low flare
productivity. However, when the field ɛ(B)(x) is highly
intermittent, the structure functions behave as transverse structure
functions of a fully developed turbulent vector field, and the scaling
of the energy dissipation is mostly determined by the dissipation of the
magnetic energy (active regions with strong flaring productivity). Based
on this recent result, we find that the dissipation spectrum of the
Bz-component is strongly related to the level of flare
productivity in a solar active region. When the flare productivity is
high, the corresponding spectrum is less steep. We also find that during
the evolution of NOAA Active Region 9393, the Bz dissipation
spectrum becomes less steep as the active region's flare activity
increases. Our results suggest that the reorganization of the magnetic
field at small scales is also relevant to flaring: the relative fraction
of small-scale fluctuations of magnetic energy dissipation increases
as an active region becomes prone to producing strong flares. Since
these small-scale changes seem to begin long before the start of a
solar flare, we suggest that the relation between scaling exponents,
calculated by using only measurements of the Bz-component,
and flare productivity of an active region can be used to monitor and
forecast flare activity.
Title: Flare Activity and Magnetic Helicity Injection by Photospheric
Horizontal Motions
Authors: Moon, Y. -J.; Chae, Jongchul; Choe, G. S.; Wang, Haimin;
Park, Y. D.; Yun, H. S.; Yurchyshyn, Vasyl; Goode, Philip R.
Bibcode: 2002ApJ...574.1066M
Altcode:
We present observational evidence that the occurrence of homologous
flares in an active region is physically related to the injection of
magnetic helicity by horizontal photospheric motions. We have analyzed
a set of 1 minute cadence magnetograms of NOAA AR 8100 taken over a
period of 6.5 hr by the Michelson Doppler Imager on board the Solar
and Heliospheric Observatory. During this observing time span, seven
homologous flares took place in the active region. We have computed
the magnetic helicity injection rate into the solar atmosphere by
photospheric shearing motions and found that a significant amount of
magnetic helicity was injected during the observing period. In a strong
M4.1 flare, the magnetic helicity injection rate impulsively increased
and peaked at the same time as the X-ray flux. The flare X-ray flux
integrated over the X-ray emission time strongly correlates with the
magnetic helicity injected during the flaring interval. The integrated
X-ray flux is found to be a logarithmically increasing function of
the injected magnetic helicity. Our results suggest that injection of
helicity and abrupt increase of helicity magnitude play a significant
role in flare triggering.
Title: Statistical Evidence for Sympathetic Flares
Authors: Moon, Y. -J.; Choe, G. S.; Park, Y. D.; Wang, Haimin;
Gallagher, Peter T.; Chae, Jongchul; Yun, H. S.; Goode, Philip R.
Bibcode: 2002ApJ...574..434M
Altcode:
Sympathetic flares are a pair of flares that occur almost simultaneously
in different active regions, not by chance, but because of some
physical connection. In this paper statistical evidence for the
existence of sympathetic flares is presented. From GOES X-ray flare
data, we have collected 48 pairs of near simultaneous flares whose
positional information and Yohkoh soft X-ray telescope images
are available. To select the active regions that probably have
sympathetic flares, we have estimated the ratio R of actual flaring
overlap time to random-coincidence overlap time for 38 active region
pairs. We have then compared the waiting-time distributions for the
two different groups of active region pairs (R>1 and R<1) with
corresponding nonstationary Poisson distributions. As a result, we
find a remarkable overabundance of short waiting times for the group
with R>1. This is the first time such strong statistical evidence
has been found for the existence of sympathetic flares. To examine
the role of interconnecting coronal loops, we have also conducted
the same analysis for two subgroups of the R>1 group: one with
interconnecting X-ray loops and the other without. We do not find any
statistical evidence that the subgroup with interconnecting coronal
loops is more likely to produce sympathetic flares than the subgroup
without. For the subgroup with loops, we find that sympathetic flares
favor active region pairs with transequatorial loops.
Title: Solar activity monitoring and forecasting capabilities at
Big Bear Solar Observatory
Authors: Gallagher, P. T.; Denker, C.; Yurchyshyn, V.; Spirock, T.;
Qiu, J.; Wang, H.; Goode, P. R.
Bibcode: 2002AnGeo..20.1105G
Altcode:
The availability of full-disk, high-resolution Ha
Title: What dynamic changes in the Sun drive the evolution of
oscillation frequencies through the activity cycle?
Authors: Goode, Philip R.; Dziembowski, W. A.
Bibcode: 2002ESASP.508...15G
Altcode: 2002soho...11...15G
The frequencies of solar oscillations (f- and p-modes) evolve through
the solar cycle. The changes are driven by some combination of changes
in the magnetic field, thermal structure and velocity field. It is
unclear what is the precise combination of the three. One way or
another, this thorny issue rests on an understanding of the response
of the solar structure to increased magnetic field, but this is
complicated. As well, we do not understand the origin of the sun's
irradiance increase with increasing magnetic activity. Until recently,
it seemed that an unphysically large magnetic field change was required
to account for the frequency evolution during the cycle. However,
the problem seems to have been solved (Dziembowski, Goode &
Schou 2001). Specifically, a small-scale magnetic field was considered
assuming uncorrelated field components - allowing the vertical component
to be statistically different from the two horizontal ones. It turns
out that a purely radial random field is the most economical, as well
as being more physically sensible for other reasons. Furthermore, the
solution might have a direct bearing on the origin of the irradiance
variation. We discuss recent results and the present state of our
knowledge.
Title: Scaling Behavior of Structure Functions of the Longitudinal
Magnetic Field in Active Regions on the Sun
Authors: Abramenko, V. I.; Yurchyshyn, V. B.; Wang, H.; Spirock,
T. J.; Goode, P. R.
Bibcode: 2002AAS...200.0309A
Altcode: 2002BAAS...34..643A
In the framework of a refined Kolmogorov's hypotheses, the scaling
behavior of the BZ--component of the photospheric magnetic
field is analyzed and compared with flaring activity in solar active
regions. We used SOHO/MDI, Huairou (China) and Big Bear measurements
of the Bz-component in the photosphere for nine active
regions. We show that there is no universal behavior in the scaling
of the Bz-structure functions for different active
regions. Scaling for a given active region is caused by intermittency
in the field, ǎrepsilon(B)(ěc x), of magnetic energy
dissipation. When intermittency is weak, the Bz-field
behaves as a passive scalar in the turbulent flow and the energy
dissipation is largely determined by the dissipation of kinetic energy
in active regions with low flare productivity. However, when the field
ǎrepsilon(B)(ěc x) is highly intermittent, the structure
functions behave as transverse structure functions of a fully developed
turbulent vector field and the scaling of the energy dissipation is
mostly determined by the dissipation of the magnetic energy (active
regions with strong flaring productivity). We found that the spectrum
of dissipation of the Bz component is strongly related
to the level of flare productivity of a solar active region. When
the flare productivity is high, the corresponding spectrum is less
steep. We also found that during the evolution of an NOAA AR 9393 the
Bz dissipation spectrum becomes less steep as the active
region's flare activity increases. We suggest that the relation between
scaling exponents and flare productivity of an active region enables
us to monitor and forecast flare activity using only measurements of
the Bz component of the photospheric magnetic field. This
work was supported in part by the Ukrainian Ministry of Science and
Education, NSF-ATM (0076602 and 0086999) and NASA (9682 and 9738)
grants. SOHO is a project of international cooperation between ESA
and NASA.
Title: The Origin of Mass, Magnetic Flux, and Magnetic Helicity in
a Solar Prominence
Authors: Chae, J.; Yun, H. S.; Moon, Y. -J.; Wang, H.; Goode, P.
Bibcode: 2002AAS...200.3715C
Altcode: 2002BAAS...34..697C
Solar prominences are cloud-like cool and dense plasma supported by
highly non-potential, and very likely twisted magnetic fields in the
corona against the gravity. Therefore, the supply of mass, magnetic
flux, and magnetic helicity is the necessary condition for the formation
of solar prominences. We have been doing a series of case studies on
the formation of a prominence in active region NOAA 8668. As a result,
we have found a series of jets in Hα and EUV at the region where
significant amounts of magnetic fluxes of opposite polarity canceled
each other. We also found the existence of non-differential-rotation
photospheric shearing motion that prevailed during the period of
prominence formation. Both the magnetic flux associated with flux
cancellation, and magnetic helicity injected by the shearing motion
were more than enough for the formation of the prominence. Our results
support that chromospheric magnetic reconnection is in charge of
supplying mass and magnetic flux, and photospheric shearing motion
is in charge of supplying magnetic helicity. This work was supported
by the US-Korea Cooperative Science Program (KOSEF 995-0200-002-2,
NSF INT-98-16267), the NASA grant NAG 5-10894 and the the National
Research Laboratory project M10104000059-01J000002500 and the BK21
project of the Korean Government.
Title: The Excitation of Solar Oscillations and Transient
Chromospheric Bright Points
Authors: Goode, P. R.
Bibcode: 2002AAS...200.5305G
Altcode: 2002BAAS...34Q.730G
The origin of the excitation of solar oscillations is reviewed, as well
as the seemingly common source of intermittant chromospheric bright
points. We review how solar oscillations are excited in seismic events
that occur very near the solar surface in the dark, inter-granular
lanes in a process that is associated with a catastrophic collapse
of the lanes in regions of vanishingly weak magnetic field. The key
observations measure the velocity field at several altitudes in the
photosphere, so that one can distinguish p-mode power from seismic event
power, since both have their power in the same region of the k-omega
diagram generally associated with p-modes. We discuss co-incident
observations of large seimic events and intermittant chromospheric
bright points that seem to reveal that the bright points occur above
large seismic events shortly after the events peak. This work was
supported by NASA-NAG5-9682 and NSF-ATM-00-86999.
Title: Magnetic Helicity Injection By Transient Photospheric Shear
Flows in Flares and Prominences
Authors: Yun, H. S.; Chae, J.; Moon, Y. -J.; Wang, H.; Goode, P. R.
Bibcode: 2002AAS...200.3716Y
Altcode: 2002BAAS...34..697Y
There has been increasing interest in magnetic helicity since it is
a well-conserved measure of the non-potentiality of solar magnetic
fields. Magnetic helicity in the solar corona may change when magnetic
helicity is transported either across the photosphere or out of the
Sun. Of our specific interest is the magnetic helicity change due to
transient shear flows in the photosphere. We have developed a method
of determining its rate from a time series of magnetograms, and have
applied it to several active regions. We present one example showing
that transient shear flows may inject significant amount of magnetic
helicity for several days during the formation of a prominence,
and other examples showing that magnetic helicity injection by
shear flows may occur impulsively during strong flares. We do not
know the physical nature of transient shear flows, but there is a
possibility that they may represent the photospheric velocity field
of low frequency, large-scale torsional Alfvén waves passing through
the solar surface. This work was supported by the US-Korea Cooperative
Science Program (KOSEF 995-0200-002-2, NSF INT-98-16267), and the the
National Research Laboratory project M10104000059-01J000002500 and
the BK21 project of the Korean Government.
Title: Flare Activity and Magnetic Helicity Injection By Photospheric
Horizontal Motions
Authors: Moon, Y. -J.; Chae, J.; Choe, G.; Wang, H.; Park, Y. D.;
Yun, H. S.; Yurchyshyn, V.; Goode, P. R.
Bibcode: 2002AAS...200.2002M
Altcode: 2002BAAS...34..673M
We present observational evidence that the occurrence of homologous
flares in an active region is physically related to the injection
of magnetic helicity by horizontal photospheric motions. We have
analyzed a set of 1 minute cadence magnetograms of NOAA AR 8100 taken
over a period of 6.5 hours by Michelson Doppler Imager (MDI) on board
Solar and Heliospheric Observatory (SOHO). During this observing time
span, seven homologous flares took place in the active region. We have
computed the magnetic helicity injection rate into the solar atmosphere
by photospheric shearing motions, and found that a significant amount
of magnetic helicity was injected during the observing period. In a
strong M4.1 flare, the magnetic helicity injection rate impulsively
increased and peaked at the same time as the X-ray flux did. The flare
X-ray flux integrated over the X-ray emission time strongly correlates
with the magnetic helicity injected during the flaring interval. The
integrated X-ray flux is found to be a logarithmically increasing
function of the injected magnetic helicity. Our results suggest that
injection of helicity and abrupt increase of helicity magnitude play
a significant role in flare triggering. This work has been supported
by NASA grants NAG5-10894 and NAG5-7837, by MURI grant of AFOSR, by
the US-Korea Cooperative Science Program (NSF INT-98-16267), by NRL
M10104000059-01J000002500 of the Korean government, and by the BK 21
project of the Korean government.
Title: Core and Large-Scale Structure of the 2000 November 24 X-Class
Flare and Coronal Mass Ejection
Authors: Wang, Haimin; Gallagher, Peter; Yurchyshyn, Vasyl; Yang,
Guo; Goode, Philip R.
Bibcode: 2002ApJ...569.1026W
Altcode:
In this paper, we present three important aspects of the X1.8 flare
and the associated coronal mass ejection (CME) that occurred on 2000
November 24: (1) The source of the flare is clearly associated with
a magnetic channel structure, as was noted in a study by Zirin &
Wang , which is due to a combination of flux emergence inside the
leading edge of the penumbra of the major leading sunspot and proper
motion of the sunspot group. The channel structure provides evidence for
twisted flux ropes that can erupt, forming the core of a CME, and may
be a common property of several superactive regions that have produced
multiple X-class flares in the past. (2) There are actually three flare
ribbons visible. The first can be seen moving away from the flare site,
while the second and third make up a stationary ribbon near the leader
spot. The moving ribbons could be due to a shock associated with the
erupting flux rope or due to the interaction of erupting rope and the
surrounding magnetic fields. In either case, the ribbon motion does
not fit the classical Kopp-Pneuman model, in which the separation
of ribbons is due to magnetic reconnection at successively higher
and higher coronal altitudes. (3) From the coronal dimming observed
with the EUV Imaging Telescope (EIT), the CME involved a much larger
region than the initial X-class flare. By comparing high-resolution
full-disk Hα and EIT observations, we found that a remote dimming
area is cospatial with the enhanced Hα emission. This result is
consistent with the recent model of Yokoyama & Shibata that some
dimming areas near footpoints may be due to chromospheric evaporation.
Title: The Earthshine project: Update on photometric and spectrometric
measurements
Authors: Palle, E.; Montanes Rodriguez, P.; Goode, P.; Koonin, S.;
Hickey, J.; Qiu, J.; Yurchysyn, V.
Bibcode: 2002cosp...34E.798P
Altcode: 2002cosp.meetE.798P
The Earthshine project is a collaborative effort between Big Bear
Solar Observatory (New Jersey Institute of Technology) and the
California Institute of Technology. Our primary goal is the precise
determination of a global and absolutely calibrated Earth's albedo
and the characterization of its synoptic, seasonal and inter-annual
variability. Photometric observations of the Earth's reflectance
have been regularly carried out during the past almost 4 years. The
up-to-date synoptic, seasonal and long term variation is the Earth's
albedo are reported in this paper, together with comparison with
modelled albedo using modern cloud satellite data end ERBE scene
models. The Earth's albedo has a major role in determining the Earth's
climate, and the possibility of a response of this parameter to solar
activity is also discussed. Simultaneously, spectrometric observations
of the earthshine have been carried out at Palomar Observatory. First
results and comparison between the spectral and photometric observations
are also being presented.
Title: Evolution of the sun's near-surface asphericities over the
activity cycle
Authors: Goode, P. R.; Didkovsky, L. V.; Libbrecht, K. G.; Woodard,
M. F.
Bibcode: 2002AdSpR..29.1889G
Altcode:
Solar oscillations provide the most accurate measures of cycle dependent
changes in the sun, and the Solar and Heliospheric Observatory/Michelson
Doppler Imager (MDI) data are the most precise of all. They give us
the opportunity to address the real challenge — connecting the MDI
seismic measures to observed characteristics of the dynamic sun. From
inversions of the evolving MDI data, one expects to determine the nature
of the evolution, through the solar cycle, of the layers just beneath
the sun's surface. Such inversions require one to guess the form of
the causal perturbation — usually beginning with asking whether
it is thermal or magnetic. Matters here are complicated because the
inversion kernels for these two are quite similar, which means that we
don't have much chance of disentangling them by inversion. However,
since the perturbation lies very close to the solar surface, one can
use synoptic data as an outer boundary condition to fix the choice. It
turns out that magnetic and thermal synoptic signals are also quite
similar. Thus, the most precise measure of the surface is required. We
argue that the most precise synoptic data come from the Big Bear
Solar Observatory (BBSO) Solar Disk Photometer (SDP). A preliminary
analysis of these data implies a magnetic origin of the cycle-dependent
sub-surface perturbation. However, we still need to do a more careful
removal of the facular signal to determine the true thermal signal.
Title: Dip-Like Magnetic Field Structure Seen in Solar Prominences
Authors: Yun, H. S.; Lee, S.; Chae, J.; Kim, J. H.; Park, Y. D.; Kim,
S. E.; Goode, P. R.; Wang, H.
Bibcode: 2002stma.conf..103Y
Altcode:
No abstract at ADS
Title: Earthshine: A Proposal To Build An Automatic System For
Observing Terrestrial Albedo.
Authors: Thejll, P.; Ulla, A.; Hanslmeier, A.; Chou, D. -Y.; Goode,
P.; Vazquez, M.; Belmonte, J. A.
Bibcode: 2002EGSGA..27.4058T
Altcode:
Terrestrial albedo data are important for climate model studies
because of the impor- tance albedo has on the net radiation budget
of the Earth. Direct measurements of the albedo are not common, and
there is no dataset with global coverage that offers an alternative
to data from satellite measurements. The satellite data, however, are
often from weather satellites that were not specifically designed to
guarantee long-term sen- sitivity stability in the imaging data, and
thus in the albedo data that can be derived from these. Therefore,
absolute calibration of terrestrial satellite albedo data is not
possible. The Earth reflects light onto the Moon proportional to
the albedo, and it is possible to measure from the Earth the so called
'earthshine' on the Moon, so accurately that a cost-effective system
for mean-terrestrial albedo monitoring can be built on the basis of
small robotic telescopes. We present a system for observation and
data-handling, that could provide data for albedo studies. The system
is intrinsically stable and would be able to produce data of long-term
stability so that questions related to the drift in satellite data
could be investigated in the future.
Title: The earthshine s spectra
Authors: Montanes Rodriguez, P.; Palle, E.; Goode, P.; Koonin, S.;
Hickey, J.; Qiu, J.; Yurchysyn, V.
Bibcode: 2002cosp...34E.810M
Altcode: 2002cosp.meetE.810M
The Earthshine project, was run by California Institute of Technology
(Caltech) between 1993 and 1995. Since 1998, it has been a collaborative
effort between Caltech and Big Bear Solar Observatory (BBSO)/New
Jersey Institute of Technology (NJIT). Our primary goal is the precise
determination of a global and absolutely calibrated Earth's albedo
and its synoptic, seasonal, and annual variability; as well as the
measurement and investigation of the resolved reflected spectrum of
the integrated Earth in the infrared region. The absorption in the
infrared region, mainly due to rotational and vibrational transitions
of the molecules, show the absorption bands of various telluric and
solar components allowing the analysis of the Earth's spectrum such as
it would be observed from the outer space. In this paper we present
preliminary results of spectroscopic observations, made at Palomar
Observatory with the 60-inch telescope's echelle spectrograph. They
targeted the visible and near infrared region of the electromagnetic
spectrum, and were performed in the spectral range (< 1μm) of the
bands of Oxygen A, Oxygen B, water and Hydrogen alpha (H). The first
three are typically terrestrial molecular bands. The fourth line, H,
is a solar line, used mainly for spectral calibration.
Title: Changes in Solar Oscillation Frequencies during the Current
Activity Maximum: Analysis and Interpretation
Authors: Dziembowski, W. A.; Goode, P. R.
Bibcode: 2002ASPC..259..476D
Altcode: 2002IAUCo.185..476D; 2002rnpp.conf..476D; 2001astro.ph..9344D
We describe systematic changes in the centroid frequencies and
the splitting coefficients as found using data from MDI on board
SOHO, covering cycle 23. The data allow us to construct a seismic
map of the evolving solar activity -- covering all latitudes. At
lower latitudes, the temporal evolution closely tracks that of {\it
butterfly diagram}. The additional information from higher latitudes
in the map is of a significant activity in the polar region, peaking
at activity minimum in 1996. The most plausible source of solar
oscillation frequency changes over the solar cycle is the evolution of
the radial component of the small-scale magnetic field. The amplitude
of the required mean field changes is about 100 G at the photosphere,
and increasing going inward.
Title: A Statistical Study for Two Classes of CMEs
Authors: Moon, Y.; Choe, G.; Park, Y.; Yang, G.; Wang, H.; Goode,
P.; Yashiro, S.; Gopalswamy, N.
Bibcode: 2001AGUFMSH12B0747M
Altcode:
MacQueen and Fisher (1983) noted the existence of two classes of CMEs;
flare-associated CMEs show the highest speeds with little acceleration,
wheras eruption-associated ones exhibit large accelerations. A
statistical study has been performed to examine the bimodality of CMEs
using the CME catalogue based on SOHO/LASCO observations from 1996 to
2000 by Yashiro and Michalek (2001). In the catalogue, we have used the
speed and acceleration data obtained from height-time plots with 2nd
order fits. We present the histogram of CME speed, the histogram of
CME acceleration, and their speed-acceleration diagram. We have also
conducted the same analysis for two different sets of data which have
both time and spatial association with GOES solar flares and filaments
activities (e.g., disappearing filaments), respectively. The filament
data were collected from the NGDC and Big Bear Solar Observatory. Major
results from this study are as follows. (1) The speed histogram for
all the CMEs has a major peaks near 300km/s but does not show any
double peaks. (2) Their acceleration histogram has a strong peak near
zero, even for the two data sets associated with solar flares and
filaments. (3) The number of CMEs with deceleration is comparable to
that of CMEs with acceleration. (4) Their acceleration distribution
has a maximum near zero regardless of their speed. (5) The ratio
of flare-associated ones to all the CMEs increases with CME speed,
wheras the ratio of filament-associated ones decreases. Finally we
compare our results with previous ones and discuss their implications
on the bimodality of CMEs.
Title: Helioseismic Role of Polar Fields
Authors: Varsik, J. R.; Goode, P. R.; Dziembowski, W. A.; Didkovsky,
L.; Woddard, M. F.
Bibcode: 2001AAS...199.8801V
Altcode: 2001BAAS...33.1433V
We examine the relationship between the change of helioseismic
frequencies at high latitudes during the solar cycle and the change
in the solar polar magnetic field. Helioseismic data from SOHO/MDI
are used to construct a helioseismic butterfly diagram, that is,
the total contributions, binned by latitude, of the p-mode splittings
decomposed into Legendre polynomials. We cover the period of the rise
of Cycle 23. We compare the frequency change contributions to polar
field strengths, in latitude bins, obtained from BBSO polar field
observations. Also we examine the residual intensity variations,
binned by latitude from the BBSO solar disk photometer.
Title: Orientation of the Magnetic Fields in Interplanetary Flux
Ropes and Solar Filaments
Authors: Yurchyshyn, Vasyl B.; Wang, Haimin; Goode, Philip R.; Deng,
Yuanyong
Bibcode: 2001ApJ...563..381Y
Altcode:
Coronal mass ejections (CMEs) are often associated with erupting
magnetic structures or disappearing filaments. The majority of CMEs
headed directly toward the Earth are observed at 1 AU as magnetic
clouds-the region in the solar wind where the magnetic field strength
is higher than average and there is a smooth rotation of the magnetic
field vectors. The three-dimensional structure of magnetic clouds can
be represented by a force-free flux rope. When CMEs reach the Earth,
they may or may not cause magnetic storms, alter Earth's magnetic field,
or produce the phenomena known as auroras. The geoeffectiveness of a
solar CME depends on the orientation of the magnetic field in it. Two
M-class solar flares erupted on 2000 February 17. The second flare
occurred near a small active region, NOAA Active Region 8872. This
eruption was accompanied by a halo CME. However, the February 17 CME did
not trigger any magnetic activity when it arrived at the Earth. Another
powerful flare, on 2000 July 14, was also associated with a halo CME,
which caused the strongest geomagnetic activity of solar cycle 23. Using
ACE measurements of the interplanetary magnetic fields, we study the
orientation of the magnetic flux ropes in both sets of magnetic clouds
and compare them with the orientation of the solar magnetic fields
and disappearing filaments. We find that the direction of the axial
field and helicity of the flux ropes are consistent with those of
the erupted filaments. Thus, the geoeffectiveness of a CME is defined
by the orientation and structure of the erupted filament and by its
magnetic helicity as well. We also suggest that the geoeffectiveness
of a CME can be forecasted using daily full-disk Hα and Yohkoh images
and MDI magnetograms as well.
Title: Inter-Active Region Connection of Sympathetic Flaring on 2000
February 17
Authors: Wang, Haimin; Chae, Jongchul; Yurchyshyn, Vasyl; Yang, Guo;
Steinegger, Michael; Goode, Philip
Bibcode: 2001ApJ...559.1171W
Altcode:
We have analyzed high-resolution Hα full disk data from Big
Bear Solar Observatory (BBSO); magnetograph and EUV data from the
Michelson Doppler Imager, Large Angle and Spectrometric Coronagraph,
and Extreme Ultraviolet Imaging Telescope on board SOHO; and Yohkoh
soft X-ray data of 2000 February 17. Two sympathetic M-class solar
flares erupted in succession in NOAA Active Region 8869 and 8872,
respectively. The eruption from AR 8872 was followed by an extremely
symmetric halo coronal mass ejection (CME). We demonstrate the loop
activation, which appears to be the consequence of the first flare in
AR 8869 and the cause of the second flare in AR 8872. The activation
started in the form of a surge just after a filament eruption and its
associated flare in AR 8869. The surge quickly turned into a set of
disturbances that propagated at a speed of about 80 km s-1
toward the other active region AR 8872. The second flare followed in
less than an hour after the arrival of the disturbances at AR 8872. The
moving disturbances appeared in absorption in both Hα and EUV 195
Å images. The disturbances may represent mass transfer, which had
a significant velocity component perpendicular to the field lines
and, hence, caused the transport of field lines. In this case, the
disturbances may be considered to be a special kind of surge, which we
may call a ``sweeping closed-loop surge.'' We also demonstrated large
area dimmings associated with the CME in three active regions. The
dimming started from AR 8869 and AR 8872 and was extended to AR 8870,
which was on the opposite side of the solar equator. We believe that
both the activation of inter-active region loops and the large-scale
dimming are the signatures of large-scale restructuring associated
with the CME.
Title: The Formation of a Prominence in Active Region NOAA
8668. I. SOHO/MDI Observations of Magnetic Field Evolution
Authors: Chae, Jongchul; Wang, Haimin; Qiu, Jiong; Goode, Philip R.;
Strous, Louis; Yun, H. S.
Bibcode: 2001ApJ...560..476C
Altcode:
We have studied the evolution of the photospheric magnetic field in
active region NOAA 8668 for 3 days while the formation of a reverse
S-shaped filament proceeded. From a set of full-disk line-of-sight
magnetograms taken by the Michelson Doppler Imager (MDI) on board
the Solar and Heliospheric Observatory (SOHO), we have found a
large canceling magnetic feature that was closely associated with
the formation of the filament. The positive flux of the magnetic
feature was initially 1.5×1021 Mx and exponentially
decreased with an e-folding time of 28 hr throughout the period of
observations. We also have determined the transverse velocities of
the magnetic flux concentrations in the active region by applying
local correlation tracking. As a result, a persistent pattern of shear
motion was identified in the neighborhood of the filament. The shear
motion had a speed of 0.2-0.5 km s-1 and fed negative
magnetic helicity of -3×1042 Mx2 into the
coronal volume during an observing run of 50 hr at an average rate
of -6×1040 Mx2 hr-1. This rate is
an order of magnitude higher than the rate of helicity change due to
the solar differential rotation. The magnetic flux of the field lines
created by magnetic reconnection and the magnetic helicity generated
by the photospheric shear motion are much more than enough for the
formation of the filament. Based on this result, we conjecture that the
filament formation may be the visible manifestation of the creation
of a much bigger magnetic structure that may consist of a flux rope
and an overlying sheared arcade.
Title: Parameters of the Turbulent Magnetic Field in the Solar
Photosphere: Power Spectrum of the Line-of-Sight Field
Authors: Abramenko, V. I.; Yurchyshyn, V. B.; Wang, H.; Goode, P. R.
Bibcode: 2001ARep...45..824A
Altcode:
Ground-based (Big Bear Solar Observatory) and extra-atmospheric
(SOHO/MDI) measurements of the photospheric line-of-sight magnetic field
of one active and two quiet regions are used to calculate power spectra
of the field, taking into account the characteristic function for the
diffraction limit of the telescope resolution. At high frequencies, the
physically meaningful linear interval in the spectrum extends to a wave
number of k=4.6 Mm-1 (spatial scale l=1.4 Mm) for the quiet regions and
k=3.35 Mm-1 (l=1.9 Mm) for the active region. A high-frequency spectral
break at k≥3 Mm-1 is associated with the characteristic telescope
function; the position of the break and the spectral slope beyond the
break do not reflect the turbulent state of the field. As the field
recording improves, the break shifts toward higher frequencies. The
spectral indices in the physically meaningful linear interval are
substantially different for the active and quiet regions: in the active
region (NOAA 8375), the spectrum behaves as E(k)≈k -1.7 (very close
to the Kolmogorov index, -5/3) in the interval 0.78≤k≤3.35 Mm-1,
while in the quiet regions E(k)≈k -1.3 for 0.77≤k≤4.57 Mm-1. This
difference can be explained by the additional effect of a small-scale
turbulent dynamo in the unperturbed photosphere. In this case, this
mechanism can generate at least 6% of the magnetic energy of the
photospheric line-of-sight field in quiet regions.
Title: Magnetic Power Spectra Derived from Ground and Space
Measurements of the Solar Magnetic Fields
Authors: Abramenko, V.; Yurchyshyn, V.; Wang, H.; Goode, P. R.
Bibcode: 2001SoPh..201..225A
Altcode:
We study magnetic power spectra of active and quiet regions by using
Big Bear Solar Observatory and SOHO/MDI measurements of longitudinal
magnetic fields. The MDI power spectra were corrected with Gaussian
Modulation Transfer Function. We obtained reliable magnetic power
spectra in the high wave numbers range, up to k=4.6 Mm−1,
which corresponds to a spatial scale l=1.4 Mm. We find that the
occurrence of the spectral discontinuity at high wave numbers,
k≥3 Mm−1, largely depends on the spatial resolution
of the data and it appears at progressively higher wave numbers as
the resolution of the data improves. The spectral discontinuity in
the raw spectra is located at wave numbers about 3 times smaller
than wave numbers, corresponding to the resolution of the data, and
about 1.5-2.0 times smaller in the case of the noise- and-resolution
corrected spectra. The magnetic power spectra for active and quiet
regions are different: active-region power spectra are described as
∼k−1.7, while in a quiet region the spectrum behaves
as ∼k−1.3. We suggest that the difference can be
due to small-scale dynamo action in the quiet-Sun photosphere. Our
estimations show that the dynamo can generate more than 6% of the
observed magnetic power.
Title: Does the Sun Shrink with Increasing Magnetic Activity?
Authors: Dziembowski, W. A.; Goode, P. R.; Schou, J.
Bibcode: 2001ApJ...553..897D
Altcode: 2001astro.ph..1473D
We have analyzed the full set of Solar and Heliospheric Observatory
(SOHO) Michelson Doppler Imager (MDI) f- and p-mode oscillation
frequencies from 1996 to date in a search for evidence of solar radius
evolution during the rising phase of the current activity cycle. Just
as Antia et al. in 2000, we find that a significant fraction of the
f-mode frequency changes scale with frequency and that if these are
interpreted in terms of a radius change, it implies a shrinking Sun. Our
inferred rate of shrinkage is about 1.5 km yr-1, which is
somewhat smaller than found by Antia et al. We argue that this rate
does not refer to the surface but, rather, to a layer extending roughly
from 4 to 8 Mm beneath the visible surface. The rate of shrinking may
be accounted for by an increasing radial component of the rms random
magnetic field at a rate that depends on its radial distribution. If
it were uniform, the required field would be ~7 kG. However, if it
were inwardly increasing, then a 1 kG field at 8 Mm would suffice. To
assess contribution to the solar radius change arising above 4 Mm, we
analyzed the p-mode data. The evolution of the p-mode frequencies may be
explained by a magnetic field growing with activity. Our finding here
is very similar to that of Goldreich et al. (1991). If the change were
isotropic, then a 0.2 kG increase, from activity minimum to maximum,
is required at the photosphere, which would grow to about 1 kG at
1 Mm. If only the radial component of the field were to increase,
then the requirement for the photospheric field increase is reduced
to a modest 60-90 G. A relative decrease in temperature of the order
of 10-3 in the subphotospheric layers, or an equivalent
decrease in the turbulent energy, would have a similar effect to the
required inward growth of magnetic field change. The implications
of the near-surface magnetic field changes depend on the anisotropy
of the random magnetic field. If the field change is predominantly
radial, then we infer an additional shrinking at a rate between 1.1
and 1.3 km yr-1 at the photosphere. If, on the other hand,
the increase is isotropic, we find a competing expansion at a rate of
2.3 km yr-1. In any case, variations in the Sun's radius
in the activity cycle are at the level of 10-5 or less and,
hence, have a negligible contribution to the irradiance variations.
Title: Asymmetric Behavior of Hα Footpoint Emission during the
Early Phase of an Impulsive Flare
Authors: Qiu, Jiong; Ding, Ming D.; Wang, Haimin; Gallagher, Peter T.;
Sato, Jun; Denker, Carsten; Goode, Philip R.
Bibcode: 2001ApJ...554..445Q
Altcode:
We study the impulsive phase of a C9.0 solar flare using high temporal
and spatial resolution Hα images from Big Bear Solar Observatory (BBSO)
in conjunction with high-cadence hard X-ray (HXR) observations from
Yohkoh. During the early impulsive phase, HXR emission emerged from
two kernels K1 and K2 which were connected by coronal loops observed
in soft X-ray (SXR) images from Yohkoh. In Hα, the initial rise was
observed in one flare kernel K2, which was followed within 10 s by
enhanced emission in the associated kernel K1. Such a significant
asymmetry was not observed at HXR wavelengths. Our analysis shows
that the asymmetric Hα footpoint emission cannot be explained by the
magnetic mirroring effect in which strong field footpoints show lower
precipitation rates. Instead, we study this phenomenon by investigating
the atmospheric response of the lower chromosphere to nonthermal
beam heating. From numerical simulations, it is suggested that a cool
atmosphere does not respond rapidly to beam impact, which may explain
the missing Hα emission at K1 during the early impulsive phase. At K2,
the early-phase atmosphere may be preferentially heated resulting in
the Hα emission rapidly following the HXR emission. This is due to
the fact that K2 is a compact source which received persistent energy
deposition and consequent heating in a confined area during the early
phase. K1, on the other hand, is a diffused source which therefore
experienced a lower heating rate per unity area. We propose a scenario
in which the flare loop consists of multiple magnetic ``threads''
connecting the compact footpoint K2 with the diffuse footpoint K1.
Title: On the Fast Fluctuations in Solar Flare Hα Blue Wing Emission
Authors: Ding, M. D.; Qiu, Jiong; Wang, Haimin; Goode, Philip R.
Bibcode: 2001ApJ...552..340D
Altcode:
Fine temporal structures in hard X-ray and microwave emissions of
solar flares have been known for many years. Recent observations with
high time and spatial resolution revealed that emissions in the wings
of Hα could also exhibit fast (subsecond) fluctuations. We argue
that such fluctuations are physically related to the small-scale
injection of high-energy electrons. We explore this through numerical
calculations. The energy equation and the equations for energy-level
populations in hydrogen, in particular including the nonthermal
collisional excitation and ionization rates, are solved simultaneously
for an atmosphere impacted by a short-lived electron beam. We
determine the temporal evolution of the atmospheric temperature,
the atomic level populations, and the Hα line intensity. We find
that although the background Hα wing emission is mainly formed in
the photosphere, the fast fluctuations are probably produced in the
chromosphere, which is penetrated by ~20 keV electrons. To yield
Hα wing fluctuations of amplitude comparable to the observations,
a mean energy flux of ~(1-2)×1011 ergs cm-2
s-1 is required for the electron beam, if one adopts a
Gaussian macrovelocity of 25 km s-1. Such a burst contains a
total energy of 1025-1026 ergs. These parameters
are compatible with elementary flare bursts.
Title: Helioseismic Constraints on Rotation and Magnetic Fields in
the Solar Core
Authors: Goode, Philip R.
Bibcode: 2001SoPh..200..343G
Altcode:
In recent years, more and more precise measurements have been made
of solar oscillation frequencies and line widths. From space, the
Solar and Heliospheric Observatory/Michelson Doppler Imager (MDI)
data has led to much progress. From the ground, networks, like Global
Oscillation Network Group (GONG), Taiwanese Oscillation Network (TON),
and Birmingham Solar Oscillations Network (BiSON) have also led to
much progress. The sharpened and enriched oscillation spectrum of
data have been critically complemented by advances in the treatments
of the opacities and the equation of state. All of this has led to a
significantly more precise probing of the solar core. Here we discuss
the progress made and suggest how the core may be better probed with
seismic data on-hand. In particular, we review our knowledge of the
rotation and structure of the core. We further argue that much may
be learned about the core by exploiting the line width data from the
aforementioned sources. Line-width data can be used to place sharper
constraints on core properties, like the degree to which the Sun
rotates on a single axis and the upper limit on magnetic fields that
may be buried in the core.
Title: Earthshine observations of the Earth's reflectance
Authors: Goode, P. R.; Qiu, J.; Yurchyshyn, V.; Hickey, J.; Chu,
M. -C.; Kolbe, E.; Brown, C. T.; Koonin, S. E.
Bibcode: 2001GeoRL..28.1671G
Altcode:
Regular photometric observations of the moon's “ashen light”
(earthshine) from the Big Bear Solar Observatory (BBSO) since December
1998 have quantified the earth's optical reflectance. We find large
(∼5%) daily variations in the reflectance due to large-scale weather
changes on the other side of the globe. Separately, we find comparable
hourly variations during the course of many nights as the earth’s
rotation changes that portion of the earth in view. Our data imply
an average terrestrial albedo of 0.297±0.005, which agrees with
that from simulations based upon both changing snow and ice cover and
satellite-derived cloud cover (0.296±0.002). However, we find seasonal
variations roughly twice those of the simulation, with the earth being
brightest in the spring. Our results suggest that long-term earthshine
observations are a useful monitor of the earth's albedo. Comparison
with more limited earthshine observations during 1994-1995 show a
marginally higher albedo then.
Title: Magnetic Power Spectra Derived From Photospheric Magnetic
Fields
Authors: Abramenko, V. I.; Yurchyshyn, V.; Wang, H.; Goode, P. R.
Bibcode: 2001AGUSM..SP41C04A
Altcode:
We study magnetic power spectra of active and quiet regions by using
Big Bear Solar Observatory and SOHO/MDI measurements of longitudinal
magnetic fields. The MDI power spectra were corrected with Gaussian
Modulation Transfer Function. We obtained reliable magnetic power
spectra in the high wave numbers range, up to k=4.6 Mm-1,
which corresponds to a spatial scale l=1.4 Mm. We find that the
occurrence of the spectral discontinuity at high wavenumbers, k >=
3 Mm-1, largely depends on the spatial resolution of the data
and it appears at progressively higher wave numbers as the resolution
of the data improves. The spectral discontinuity in the raw spectra
is located at wave numbers about 3 times smaller than wavenumbers,
corresponding to the resolution of the data, and about 1.5 -- 2.0 times
smaller in the case of the noise-and-resolution corrected spectra. The
magnetic power spectra for active and quiet regions are different:
active region power spectra are described as ~ k-1.7,
while in a quiet region the spectrum behaves as ~ k-1.3. We
suggest, that the difference can be due to small-scale dynamo action
in the quiet sun photosphere. Our estimations show that the dynamo
can generate more than 6% of the observed magnetic power.
Title: Photospheric Diameter Measurements and Variations in the
Solar Luminosity
Authors: Goode, P. R.
Bibcode: 2001AGUSM..SP31B06G
Altcode:
The size of the Sun and its temporal variation, if any, have been of
historical interest. Recently, helioseismic (SOHO/MDI) and photometric
(Solar Disk Monitor) data have been used to show that the photospheric
radius is about 300 km smaller than what had been the standard for a
quarter century. The change in the Sun's size through the solar cycle
has also been carefully studied. From Solar Diameter Monitor data
covering the decline of cycle 21, Brown and Christensen-Dalsgaard
(1998) determined that the average annual radii are consistent to
within their measurement errors of about 40 km. SOHO/MDI data covering
the rising phase of cycle 23 have been used to show the upper limit on
annual changes is an order of magnitude smaller. Such values imply a
negligible contribution of the radius change to the variation of the
Sun's irradiance. We use SOHO/MDI data to discuss the relative roles,
in the radius changes, of the magnetic field's growth with increasing
activity, and/or a relative decrease in subphotospheric temperature
and/or an equivalent decrease in the turbulent energy.
Title: Inter-Active Region Connection of Sympathetic Flaring on 2000
February 17
Authors: Wang, H.; Chae, J.; Yurchyshyn, V.; Yang, G.; Steinegger,
M.; Goode, P. R.
Bibcode: 2001AGUSM..SP42A03W
Altcode:
We have analyzed high resolution Hα full disk data from Big Bear
Solar Observatory (BBSO), magnetograph and EUV data from MDI, LASCO
and EIT on board SOHO, and Yohkoh soft X-ray data of February 17,
2000. Two sympathetic M-class solar flares erupted in succession
in NOAA 8869 and 8872, respectively. The eruption from AR 8872 was
followed by an extremely symmetric halo CME. We demonstrate a new
kind of loop activation, which appears to be the consequence of
the first flare in AR 8869 and the cause of the second flare in
AR 8872. The activation started in the form of a surge just after
a filament eruption and its associated flare in AR 8869. The surge
quickly turned into a set of disturbances that propagated at a speed of
about 80 km/s toward the other active region AR 8872. The second flare
followed in less than an hour after the arrival of the disturbances
at AR 8872. The moving disturbances appeared in absorption in both
Hα and EUV 195A images. The disturbances may represent mass transfer
which had a significant velocity component perpendicular to the field
lines and, hence, caused the transport of field lines. In this case,
the disturbances may be considered to be a special kind of surge,
which we may call a "sweeping closed-loop surge". Alternatively, the
disturbances may represent fronts of compressive magnetohydrodynamic
waves that were driven by the surge. We also demonstrated large area
dimmings associated with the CME in three active regions. The dimming
started from ARs 8869 and 8872, and was extended to AR 8870 which was
on the opposite side of the solar equator. We believe that both the
activation of inter-active region loops and the large scale dimming are
the signatures of large scale re-structuring associated with the CME.
Title: Orinetation of the Magnetic Fields in Interplanetary Flux
Ropes and Solar Filaments
Authors: Yurchyshyn, V.; Wang, H.; Goode, P. R.; Deng, Y.
Bibcode: 2001AGUSM..SH61A02Y
Altcode:
Coronal mass ejections are often associated with erupting magnetic
structures or disappearing filaments. Majority of CMEs headed directly
toward the earth are observed at 1AU as magnetic clouds --- region in
the solar wind where the magnetic field strength is higher than average
and smooth rotation of the magnetic field vectors. The 3D structure
of magnetic clouds can be represented by force-free flux rope. When a
CME reaches the earth, it may or may not cause magnetic storms, alter
Earth's magnetic field or produce the phenomena known as auroras. The
geoeffectiveness of a solar CME depends on the orientation of the
magnetic field in it. Two M-class solar flares erupted on February
17, 2000. The second flare occurred near a small active region NOAA
8872. The eruption was accompanied by a halo CME. However the February
17 CME did not trigger any magnetic activity at the time it arrived at
the earth. Another powerful flare on July 14, 2000 was also associated
with a halo CME, which caused strongest geomagnetic activity in the
solar cycle 23. Using ACE measurements of the interplanetary magnetic
fields we study the orientation of the magnetic flux ropes in both
magnetic clouds and compare it to the orientaion of solar magnetic
fields and disappearing filaments. We find that the direction of
the axial filed in the flux ropes and their helicity are consistent
with the direction of the axial field and helicity of the erupted
filaments. Thus, the geoeffectiveness of a CME is defined by the
orientation and structure of the erupted filament and by its magnetic
helicity as well. We also suggest that geoeffectiveness of a CME can
be forecasted using daily full disk Hα and Yohkoh images and MDI
magnetograms as well.
Title: On the Correlation Between the Orientation of Moving Magnetic
Features and the Large-Scale Twist of Sunspots
Authors: Yurchyshyn, V.; Wang, H.; Goode, P. R.
Bibcode: 2001AGUSM..SP41C03Y
Altcode:
We present new results on the nature of moving magnetic features
(MMFs) deduced from Big Bear Solar Observatory observations of the
longitudinal magnetic fields of two large solar spots. MMFs are small
magnetic bipoles that move outward, across the moat of an eroding
sunspot. We find that MMFs are not randomly oriented. To wit, in 21
out of 28 (75%) MMF pairs, the magnetic element having the polarity
of the sunspot was located farther from the sunspot. Furthermore,
there is a correlation between the orientation of the bipole and that
of the twist in a sunspot. For the two nearly round sunpots we studied,
we found that the bipoles were rotated counterclockwise in the case of a
clockwise twisted sunspot and clockwise for a spot with counterclockwise
twist. We also found a correlation between the orientation of MMF
bipole and the amount of twist in the spot. The MMF bipoles around
the highly twisted sunspot are oriented nearly tangential to the edge
of the sunspot; while in the slightly twisted sunspot the bipoles are
oriented nearly radially, so that they point back to the spot.
Title: Results from the Big Bear Solar Observatory's New Digital
Vector Magnetograph
Authors: Spirock, T. J.; Denker, C.; Varsik, J.; Shumko, S.; Qiu,
J.; Gallagher, P.; Chae, J.; Goode, P.; Wang, H.
Bibcode: 2001AGUSM..SP51B06S
Altcode:
During the past several years the Big Bear Solar Observatory has
been involved in an aggressive program to modernize the observatory's
instrumentation. At the forefront of this effort has been the upgrade
of the observatory's digital vector magnetograph (DVMG), which has been
recently integrated into the observatory's daily observing program. The
DVMG, which is mounted on the observatory's 25 cm vacuum refractor,
is a highly sensitive, high cadence magnetograph which studies the
FeI line at 630.1 nm. An easy to use GUI observing tool has been
written to aid instrument development and data acquisition. This
tool automatically calibrates the data and generates near real-time
vector magnetograms which will aid space weather forecasting and the
support of space weather missions. Also, our plan is to integrate the
DVMG data into the HESSI Synoptic Archive. The very sensitive quiet
Sun magnetograms, produced by the DVMG, will aid the study of small
scale magnetic reconnection at the intranetwork level and its possible
contribution to the coronal heating problem. Quiet sun longitudinal and
active region vector magnetograms will be presented. Image quality,
such as bias, cross-talk, noise levels and sensitivity, will be
discussed in addition to the improvements gained in post processing
such as image selection and image alignment.
Title: Infrared Magnetograph at Big Bear Solar Observatory
Authors: Goode, Philip
Bibcode: 2001STIN...0215955G
Altcode:
With the support of DURIP funding, we have developed the hardware
leading to the world's only filter-based magnetograph for the near
IR. The heart of such a system includes a Fabry-Perot filter following
a prefilter which is sufficiently narrow to ensure that it knocks out
all the side bands of the Fabry-Perot (i.e. the filter's pass band is
narrower than the free spectral range of the Fabry Perot) . The required
IR Fabry-Perot system exists; we have purchased one from the Queens-gate
with DURIP funds. Nonetheless, there are no such magnetographs, at
present, for measuring the evolution of magnetic fields in IR.
Title: On the Correlation between the Orientation of Moving Magnetic
Features and the Large-Scale Twist of Sunspots
Authors: Yurchyshyn, Vasyl B.; Wang, Haimin; Goode, Philip R.
Bibcode: 2001ApJ...550..470Y
Altcode:
We present new results on the nature of moving magnetic features
(MMFs) deduced from Big Bear Solar Observatory observations of the
longitudinal magnetic fields of two large solar spots. MMFs are small
magnetic bipoles that move outward across the moat of an eroding
sunspot. We find that MMFs are not randomly oriented. To wit, in 21
out of 28 (75%) MMF pairs, the magnetic element having the polarity
of the sunspot was located farther from the sunspot. Furthermore,
there is a correlation between the orientation of the bipole and that
of the twist in a sunspot. For the two nearly round sunpots we studied,
we found that the bipoles were rotated counterclockwise in the case of a
clockwise twisted sunspot and clockwise for a spot with counterclockwise
twist. We also found a correlation between the orientation of MMF
bipole and the amount of twist in the spot. The MMF bipoles around
the highly twisted sunspot are oriented nearly tangential to the edge
of the sunspot, while in the slightly twisted sunspot the bipoles are
oriented nearly radially so that they point back to the spot.
Title: Small Magnetic Bipoles Emerging in a Filament Channel
Authors: Chae, Jongchul; Martin, Sara F.; Yun, H. S.; Kim, Junghoon;
Lee, Sangwoo; Goode, Philip R.; Spirock, Tom; Wang, Haimin
Bibcode: 2001ApJ...548..497C
Altcode:
Observations have shown that quiescent prominences or filaments have a
hemispheric magnetic pattern of chirality. Motivated by the question
of whether the filament chirality is of subsurface origin or not,
we have studied small magnetic bipoles that emerged in a quiescent
filament channel at latitude N45°. During our 5 day observing run,
performed in 1999 October, a huge filament erupted and reformed shortly
in the same filament channel. Using high-cadence, long-integration
line-of-sight magnetograms taken at Big Bear Solar Observatory, we
identified a total of 102 bipoles that showed an average total flux
of 2.8×1019 Mx, an average separation of 7400 km at the
time of full development, and an emergence rate of 430 hr-1
per the entire solar surface area. These properties indicate that most
of the bipoles are ephemeral regions. The most important finding in
the present study is that the magnetic axes of the bipoles emerging in
the filament channel are systematically oriented; a negative (trailing)
pole is observed to be located preferentially to the south-east of its
companion positive (leading) pole. This preferred orientation does not
match either the Hale law of active region orientation or a theory that
attributes the axial field of a filament to emerging bipoles. We propose
two possible subsurface field configurations of bipoles consistent with
the observed preferential orientation and discuss physical implications
of our results for understanding filament magnetic fields.
Title: The new global high-resolution Hα network: preliminary
results on the chromospheric differential rotation
Authors: Steinegger, M.; Denker, C.; Goode, P. R.; Marquette, W. H.;
Varsik, J.; Wang, H.; Otruba, W.; Freislich, H.; Hanslmeier, A.; Luo,
G.; Chen, D.; Zhang, Q.
Bibcode: 2001ESASP.464..315S
Altcode: 2001soho...10..315S
A new global network for high-resolution Hα full-disk observations of
the sun has been established at the Big Bear Solar Observatory (U.S.A.),
the Kanzelhöhe Solar Observatory (Austria), and the Yunnan Astronomical
Observatory (China). Each of the three stations have a 2K×2K pixel CCD
detector available to monitor the sun with a spatial resolution of 1
arcsec per pixel and a cadence of at least 1 image per minute. Having
high-cadence data from three observing stations available enables us to
accurately track solar rotation rates and meridional motions by local
correlation (LCT) and feature tracking techniques. This includes, e.g.,
tracking over several days the motions around active regions. After
an overview of the new Hα network and its scientific objectives, we
present and discuss the first preliminary results of the determination
of the chromospheric differential rotation by LCT from a high-cadence
time-series of Hα full-disk images. The obtained equatorial rotation
rate of 13.3044 deg/day (2.6876 μrad/s) agrees well with the values
obtained by other authors. Finally, we briefly outline our future
plans for the continuation of this work.
Title: The Big Bear Solar Observatory's Digital Vector Magnetograph
Authors: Spirock, T.; Denker, C.; Chen, H.; Chae, J.; Qiu, J.; Varsik,
J.; Wang, H.; Goode, P. R.; Marquette, W.
Bibcode: 2001ASPC..236...65S
Altcode: 2001aspt.conf...65S
No abstract at ADS
Title: Synoptic Observations of the Sun from Big Bear Solar
Observatory (CD-ROM Directory: contribs/goode)
Authors: Goode, P. R.; Denker, C.; Marquette, W. H.; Wang, H.
Bibcode: 2001ASPC..223..656G
Altcode: 2001csss...11..656G
No abstract at ADS
Title: A Rapid Change in Magnetic Connectivity Observed Before
Filament Eruption and Its Associated Flare
Authors: Kim, Jung-Hoon; Yun, H. S.; Lee, Sangwoo; Chae, Jongchul;
Goode, Philip R.; Wang, Haimin
Bibcode: 2001ApJ...547L..85K
Altcode:
To gain insight to the cause of filament eruptions and flares on
the Sun, we observed a filament that erupted in active region NOAA
8597. The observations consisted of Hα filtergrams at three wavelengths
(line center and +/-0.5 Å) and line-of-sight magnetograms. All
were taken on 1999 June 24 at Big Bear Solar Observatory. We found
from the time sequence of Hα images that the filament eruption was
preceded by a rapid change in connectivity in a bundle of filament
threads. The thread bundle was initially sharply curved near its one
end of the filament and suddenly flipped and then became straight in
the new orientation. The flipped segment of the thread bundle swept
over a 100''×50'' area on the solar surface in
about half an hour. At the latter stage of the connectivity change,
we observed a downward draining of material along the thread bundle
that had a transverse component of 50 km s-1. After that,
the filament body split into two parallel parts, one part erupted
while the other part remained, and the two-ribbon flare occurred. We
also found canceling magnetic features in the vicinity of the initial
location of the thread end, which displayed a flux decrease during the
Hα connectivity change. Our results show clear and direct evidence
that magnetic reconnection takes place in the low atmosphere prior to
eruption. This preeruption reconnection seems to be very different
from a posteruption coronal reconnection, which is believed to lead
to a two-ribbon flare.
Title: Dynamics of Quiet Sun Magnetic Fields
Authors: Denker, C.; Spirock, T.; Varsik, J. R.; Chae, J.; Marquette,
W. H.; Wang, H.; Goode, P. R.
Bibcode: 2001ASPC..236..463D
Altcode: 2001aspt.conf..463D
No abstract at ADS
Title: Multi-Wavelength Observations of Solar Fine-Structure with
High Spatial Resolution (CD-ROM Directory: contribs/denker)
Authors: Denker, C.; Spirock, T. J.; Jefferies, S. M.; Chen, H.;
Marquette, W. H.; Wang, H.; Goode, P. R.
Bibcode: 2001ASPC..223..607D
Altcode: 2001csss...11..607D
No abstract at ADS
Title: Ultraviolet and Hα Emission in Ellerman Bombs
Authors: Qiu, Jiong; Ding, Ming D.; Wang, Haimin; Denker, Carsten;
Goode, Philip R.
Bibcode: 2000ApJ...544L.157Q
Altcode:
We present the first high-cadence time profiles of Ellerman bombs
(EBs) at two wavelengths, 1.3 Å in the blue wing of the Hα line and
the UV continuum at 1600 Å, and study their temporal correlation. Our
results demonstrate that 46 out of 75 EBs exhibit a good correlation at
the two wavelengths with a correlation coefficient greater than 50%,
suggesting that a common energy release produces emission at the two
wavelengths. We also find that the EBs with strong Hα emission tend
to show a good Hα-UV correlation but that the weakly correlated or
noncorrelated EBs are usually weak in Hα emission. More than half of
the Hα-UV well-correlated EBs are located at the boundaries of unipolar
magnetic areas; the others are located at, or close to, the magnetic
inversion lines. However, the majority of the weakly or noncorrelated
EBs are located at the magnetic inversion lines. Our results suggest
that the physical mechanisms and the energy distributions are quite
different in different types of EBs and that heating in the photosphere
and temperature minimum region is very important for producing EBs. The
high-cadence observations of EBs also confirm unambiguously that the
light curves of EBs generally demonstrate a fast rise and a fast decay,
with an average e-fold rising/decaying time of about 1 minute, which
distinguishes EBs from the flare phenomenon.
Title: High-Cadence Observations of an Impulsive Flare
Authors: Wang, Haimin; Qiu, Jiong; Denker, Carsten; Spirock, Tom;
Chen, Hangjun; Goode, Philip R.
Bibcode: 2000ApJ...542.1080W
Altcode:
No abstract at ADS
Title: Infrared Studies of Solar Convection
Authors: Goode, Philip
Bibcode: 2000STIN...0137723G
Altcode:
This ASSERT grant was to support the Ph.D. work of Tom Spirock who is
a native of New Jersey. Tom will finish his Ph.D. this year, thanks
in large part to ASSERT support. His work was to build an infrared
magnetograph and use it for scientific work. Solar magnetic fields are
concentrated in flux tubes, and appear on different scales: sunspots,
pores (small sunspots without penumbra) and magnetic network flux
elements. The magnetic network elements are the detritus of decaying
active regions and play an important part in the solar cycle. They
are very long lived.
Title: Magnetic Topology in 1998 November 5 Two-Ribbon Flare as
Inferred from Ground-based Observations and Linear Force-free Field
Modeling
Authors: Yurchyshyn, V. B.; Wang, H.; Qiu, J.; Goode, P. R.; Abramenko,
V. I.
Bibcode: 2000ApJ...540.1143Y
Altcode:
We analyzed the three-dimensional structure of the linear force-free
magnetic field. A longitudinal magnetogram of Active Region NOAA
8375 has been used as the photospheric boundary condition. The 1998
November 5 2B/M8.4 two-ribbon flare can be explained in the framework
of quadrupolar reconnection theory: the interaction of two closed
magnetic loops that have a small spatial angle. The energy derived from
soft X-ray telescope (SXT)/Yohkoh data (3-6×1030 ergs)
is 1 order of magnitude higher than the lower limit of flare energy
predicted by Melrose's model. The latter estimation was made using
the linear force-free extrapolation. It was suggested that, taking
into account the nonlinear character of the observed magnetic field,
we can increase the lower limit of the magnetic energy stored in the
studied magnetic configuration. The revealed magnetic configuration
allows us to understand the observed location and evolution of the flare
ribbons and the additional energy released during the gradual phase
of the flare, as well. Besides, reconnection of closed magnetic loops
can logically explain the connection between a two-ribbon flare and a
giant X-ray postflare arch, which usually is observed after the flare
onset. We emphasize that unlike the Kopp and Pneuman configuration,
the model discussed here does not necessarily require destabilization
and opening of the magnetic field.
Title: High-Resolution Hα Observations of Proper Motion in NOAA 8668:
Evidence for Filament Mass Injection by Chromospheric Reconnection
Authors: Chae, Jongchul; Denker, Carsten; Spirock, Tom J.; Wang,
Haimin; Goode, Philip R.
Bibcode: 2000SoPh..195..333C
Altcode:
There have been two different kinds of explanations for the source
of cool material in prominences or filaments: coronal condensations
from above and cool plasma injections from below. In this paper, we
present observational results which support filament mass injection
by chromospheric reconnection. The observations of an active filament
in the active region NOAA 8668 were performed on 17 August 1999 at a
wavelength of Hα−0.6 Å using the 65 cm vacuum reflector, a Zeiss Hα
birefringent filter, and a 12-bit SMD digital camera of Big Bear Solar
Observatory. The best image was selected every 12 s for an hour based
on a frame selection algorithm. All the images were then co-aligned and
corrected for local distortion due to the seeing. The time-lapse movie
of the data shows that the filament was undergoing ceaseless motion. The
Hα flow field has been determined as a function of time using local
correlation tracking. Time-averaged flow patterns usually trace local
magnetic field lines, as inferred from Hα fibrils and line-of-sight
magnetograms. An interesting finding is a transient flow field in a
system of small Hα loops, some of which merge into the filament. The
flow is associated with a cancelling magnetic feature which is located
at one end of the loop system. Initially a diverging flow with speeds
below 10 km s−1 is visible at the flux cancellation
site. The flow is soon directed along the loops and accelerated up
to 40 km s−1 in a few minutes. Some part of the plasma
flow then merges into and moves along the filament. This kind of
transient flow takes place several times during the observations. Our
results clearly demonstrate that reconnection in the photosphere and
chromosphere is a likely way to supply cool material to a filament,
as well as re-organizing the magnetic field configuration, and, hence,
is important in the formation of filaments.
Title: Measuring Seeing from Solar Scintillometry and the Spectral
Ratio Technique
Authors: Goode, P. R.; Wang, H.; Marquette, W. H.; Denker, C.
Bibcode: 2000SoPh..195..421G
Altcode:
In principle, the optical transfer function can be described by a
single parameter, the Fried parameter r0, which reveals
the net effect of the turbulence along the line of sight. We present
measurements of the Fried parameter obtained from the spectral ratio
technique and compare them to data from solar scintillometry and
from angle-of-arrival fluctuations. The measurements were performed
at the Big Bear Solar Observatory (BBSO) in 1997 and 1998 - before
and after a series of steps were taken to reduce dome seeing. The
results show that the dome seeing was considerably reduced and now
approaches the seeing conditions measured outside the dome. The Fried
parameter as measured by the spectral ratio technique now frequently
exceeds r0=10 cm at our lake site observatory. Accounting
for the remaining dome and window seeing, the scintillometer and the
angle-of-arrival data imply the potential for an r0>20
cm for BBSO during days of good seeing.
Title: Signatures of the Rise of Cycle 23
Authors: Dziembowski, W. A.; Goode, P. R.; Kosovichev, A. G.; Schou, J.
Bibcode: 2000ApJ...537.1026D
Altcode:
During the rise of Cycle 23, we have found a sizable, systematic
evolution of the Solar and Heliospheric Observatory/Michelson Doppler
Imager solar oscillation frequencies implying significant changes in the
spherically symmetric structure of the Sun's outer layers as well as in
its asphericity up to a P18 Legendre distortion. We conducted
a search for corresponding asymmetries in Ca II K data from Big Bear
Solar Observatory. We found tight temporal and angular correlations of
the respective asphericities up through P10. This result
emphasizes the role of the magnetic field in producing the frequency
changes. We carried out inversions of the frequency differences and
the splitting coefficients assuming that the source of the evolving
changes is a varying stochastic magnetic field. With respect to the
most recent activity minimum, we detected a significant perturbation in
the spherical part at a depth of 25-100 Mm, which may be interpreted
as being a result of a magnetic perturbation, <B2>,
of about (60KG)2 and/or a relative temperature perturbation
of about 1.2×10-4. Larger, although less statistically
significant, perturbations of the interior structure were found in
the aspherical distortion.
Title: Comparison of the 1998 April 29 M6.8 and 1998 November 5
M8.4 Flares
Authors: Wang, Haimin; Goode, Philip R.; Denker, Carsten; Yang, Guo;
Yurchishin, Vasyl; Nitta, Nariaki; Gurman, Joseph B.; St. Cyr, Chris;
Kosovichev, Alexander G.
Bibcode: 2000ApJ...536..971W
Altcode:
We combined, and analyzed in detail, the Hα and magnetograph data
from Big Bear Solar Observatory (BBSO), full-disk magnetograms from
the Michelson Doppler Imager (MDI) on board Solar and Heliospheric
Observatory (SOHO), coronagraph data from the Large Angle Spectrometric
Coronagraph (LASCO) of SOHO, Fe XII 195 Å data from the Extreme
ultraviolet Imaging Telescope (EIT) of SOHO, and Yohkoh soft X-ray
telescope (SXT) data of the M6.8 flare of 1998 April 29 in National
Oceanic and Atmospheric Administration (NOAA) region 8375 and the
M8.4 flare of 1998 November 5 in NOAA region 8384. These two flares
have remarkable similarities:1. Partial halo coronal mass ejections
(CMEs) were observed for both events. For the 1998 April 29 event,
even though the flare occurred in the southeast of the disk center,
the ejected material moved predominantly across the equator, and the
central part of the CME occurred in the northeast limb. The direction
in which the cusp points in the postflare SXT images determines the
dominant direction of the CMEs.2. Coronal dimming was clearly observed
in EIT Fe XII 195 Å for both but was not observed in Yohkoh SXT for
either event. Dimming started 2 hr before the onset of the flares,
indicating large-scale coronal restructuring before both flares.3. No
global or local photospheric magnetic field change was detected from
either event; in particular, no magnetic field change was found in the
dimming areas.4. Both events lasted several hours and, thus, could be
classified as long duration events (LDEs). However, they are different
in the following important aspects. For the 1998 April 29 event,
the flare and the CME are associated with an erupting filament in
which the two initial ribbons were well connected and then gradually
separated. SXT preflare images show the classical S-shape sheared
configuration (sigmoid structure). For the 1998 November 5 event, two
initial ribbons were well separated, and the SXT preflare image shows
the interaction of at least two loops. In addition, no filament eruption
was observed. We conclude that even though these two events resulted
in similar coronal consequences, they are due to two distinct physical
processes: eruption of sheared loops and interaction of two loops.
Title: The Dynamics of the Excitation of Solar Oscillations
Authors: Strous, Louis H.; Goode, Philip R.; Rimmele, Thomas R.
Bibcode: 2000ApJ...535.1000S
Altcode:
We investigate seismic events, bursts of seismic waves that are
generated locally just below the solar surface and that we detect
traveling up through the photosphere. We identify a few thousand
seismic events by their traveling wave character and find that they
are associated with continuum darkening and downflow and have an
extent of on average about 10-15 minutes and 1 Mm. Their birth rate
is about 8×10-16 m-2 s -1. The
observed upwardly traveling seismic flux in the average event
(as derived from velocities in the p-mode region of k-ω space) is
followed after about 3 minutes by some reflected downward flux. Only
a small fraction of the energy generated in the hypocenter of the
event below the surface travels straight up for us to see. The bulk
of the generated energy is directed or reflected downward, and is
eventually transformed into p-modes. The seismic events at the surface
contain about 1.5×1019 J of seismic energy each, which
corresponds to an average flux level of about 8.5 kW m-2
over the whole surface. The total energy flow is likely more than an
order of magnitude greater, and is then in the same ballpark as the
estimate of Libbrecht for the power required to sustain the p-mode
spectrum. We find a roughly linear relation between the peak seismic
flux and the peak downward convective velocity associated with each
seismic event, which does not fit the highly nonlinear relations found
theoretically by Lighthill and Goldreich & Kumar for stochastic
excitation by turbulent convection, but does fit the monopole source
deduced by Nigam & Kosovichev from a study of the p-mode spectrum.
Title: Extreme-Ultraviolet Flare Loop Emissions in an Eruptive Event
Authors: Qiu, Jiong; Wang, Haimin; Chae, Jongchul; Goode, Philip R.
Bibcode: 2000SoPh..194..269Q
Altcode:
The TRACE/BBSO joint campaign on 27 September 1998 observed an eruptive
flare event which lasted for half an hour. The observation covered
several ultraviolet (UV) and extreme-ultraviolet (EUV) lines and Hα
center and off-band emissions with very high spatial resolution. We find
the EUV emissions in different stages of the flare display different
characteristics. (1) During the `pre-flare' phase, when the SXR output
was weak, we observed simultaneous impulsive HXR peak at 25-100
keV and strong EUV emission. (2) In the impulsive phase, when Hα,
UV and SXR emissions were rising to the maxima, the EUV emission was
very weak. (3) During the main phase, when SXR emission was decaying,
a peak in the EUV emission was observed which was substantially delayed
by 7 min compared to emissions from other wavelengths. Based on our
observations, we propose that the `pre-flare' phase in this event was
a separate energy release process rather than a mere pre-cursor of the
flare, and it is likely that the `pre-flare' EUV emission was due to
weak in situ heating of low-lying coronal loops. The mechanism of the
EUV emission in the main phase is investigated. It is suggested that
the delayed EUV emission may come from cooling of SXR loops.
Title: Energy Release in an Impulsive Flare
Authors: Qiu, J.; Wang, H.; Yurchyshyn, V. B.; Goode, P. R.;
BBSO/NJIT Team
Bibcode: 2000SPD....31.0258Q
Altcode: 2000BAAS...32..821Q
We analyze the multi-spectral observations on an impulsive short-lived
flare event, and demonstrate that the flare consisted of several
flaring components with different evolution profiles, morphologies,
energy spectra, and magnetic configurations. These observations suggest
that the magnetic energy was released in this event in several ways. (1)
Two hard X-ray components were observed by Yohkoh HXT. One component was
brightened and reached its emission maximum more slowly than the other
component by > 15 seconds, and the spectrum of the slow component
was much softer than the fast component. The coordinated high resolution
ground-based observations from Big Bear Solar Observatory (BBSO) further
demonstrate that these two hard X-ray components were each co-aligned
with complicated Hα and magnetic field structures. Therefore, the two
hard X-ray components should come from different magnetic reconnection
processes at different locations. (2) Accompanying the flare, we find
both hot and cool mass ejections. The cool mass ejection was related
to the fast-varying non-thermal flare component, while the hot mass
ejection was related to the flare component which exhibited a strong
heating process. The hot mass ejection, or bright surge, also led
to a long-lasting (for at least a few hours) bright EUV loop. Such
observation offers a strong evidence that both pre-flare and post-flare
heating of the chromospheric material occurred at the root of the
bright surge. (3) We study the magnetic field configurations of the
flare components, and propose that both the non-thermal and thermal
components of the flare, together with the cool and hot surges, were
produced by the magnetic reconnection of the large scale over-lying
open field lines with the low-lying magnetic loops, while the gradual
and thermal flare components and bright surge were located in the area
of magnetic quadrupolar structures where moving magnetic features and
flux cancellation were observed. The observations suggest that the
proper motions in the region of the quadrupolar structure may enhance
electric current along the separatrix and neutral point, and produce
heating via current dissipation in the quadrupolar areas in the lower
atmosphere both before and after the fast reconnection occurred.
Title: Earthshine and the Earth's Reflectivity
Authors: Goode, P. R.; Hickey, J.; Qiu, J.; Yurchyshyn, V. B.; Koonin,
S. E.; Brown, T.; Kolbe, E.; Chu, M.
Bibcode: 2000SPD....3102121G
Altcode: 2000BAAS...32..833G
The earth's climate is driven by the net sunlight reaching
the earth, which depends on the solar irradiance and the earth's
reflectivity. Changes in the the solar irradiance have been well-studied
for twenty years, but the degree of variation in the earth's albedo
is not so clear. We have been measuring the earthshine from Big Bear
Solar Observatory (BBSO) since December 1998. Earthshine, or "ashen
light", is sunlight reaching the eye of a nighttime observer after
being successively reflected from the day side of the earth, and the
dark face of the moon. The ratio of reflected light from the dark
part of the moon to that from the bright part provides an absolutely
calibrated, large scale measure of the earth's albedo. We have solved
the long-standing problem of determining the scattering of sunlight
from the moon as a function of lunar phase. Earthshine measurements
of the earth's albedo are complementary to those from satellites. We
find the earth's albedo varies by 20% with season, and by as much at
5% from night to night. We put contemporaneous cloud cover data into
a scene model and calculate a good agreement with our observations,
but we also find some interesting differences. Using the scene model
and monthly averaged cloud cover data from ISCCP, we find between 1986
and 1990 (solar minimum to near solar maximum) that the change in the
net irradiance into the climate system is several times larger from
the varying albedo than from the varying solar irradiance. The two
changes are in phase.
Title: Orientation of Emerging Bipoles in a Filament Channel
Authors: Chae, J.; Goode, P. R.; Spirock, T. J.; Wang, H.; Martin,
S. F.; Yun, H. S.; Kim, Jung-Hoon; Lee, Sangwoo
Bibcode: 2000SPD....31.0405C
Altcode: 2000BAAS...32R.835C
Observations have shown that quiescent prominences or filaments have
a hemispheric magnetic pattern of chirality or handedness. Motivated
by the question of whether the filament chirality is of sub-surface
origin or not, we have studied magnetic bipoles emerging in a quiescent
filament channel at latitude N45° . During our 5 day observing run
performed in 1999 October, a huge filament erupted and another began to
form in the same filament channel. Using high cadence deep line-of-sight
magnetograms, we identified a total of 102 small emerging bipoles,
which display the following statistical properties: 1) an average flux
of 1.2x 1019 Mx and an average separation of 7200 km; 2) an
inferred global emergence frequency of 600 hr-1 all over the
solar surface; and 3) a preferred orientation that a negative (trailing)
pole is located at the south-east of the companion positive (leading)
pole. The majority of the bipoles appear to be ephemeral regions which
are systematically smaller than those previously studied with Kitt
Peak full disk daily magnetograms. The preferred orientation of these
bipoles differs greatly from both the filament axial field direction
and the active region polarity law. We conclude that factors other than
the Hale polarity law are the cause of asymmetry in the orientation of
small bipoles having total magnetic fluxes below 2 x 1019 Mx.
Title: First Observations with the Global High-Resolution H-alpha
Network
Authors: Varsik, J. R.; Steinegger, M.; Denker, C.; Goode, P. R.;
Wang, H.; Luo, G.; Chen, D.; Zhang, Q.; Otruba, W.; Hanslmeier, A.;
Freislich, H.
Bibcode: 2000SPD....3102108V
Altcode: 2000BAAS...32..830V
We are in the final stages of establishing a three-site global network
for continuous full disk H-alpha observations based on our experience
with making high-resolution full disk H-alpha observations at Big
Bear Solar Observatory. Utilizing existing telescopes at Big Bear
Solar Observatory (USA), Kanzelhoehe Solar Observatory (Austria),
and Yunnan Astronomical Observatory (China), the three stations are
each equipped with 2K X 2K CCD detectors and will monitor the Sun at a
1 minute cadence. We expect to monitor the emergence of each new flux
region to obtain an unbiased data set in order to understand why some
regions grow to super-activity while most decay quickly, as well as a
more complete and uniform set of flare observations. We also expect
to implement automatic detection of filament eruptions. Having high
cadence data from three observing stations will also increase the
accuracy of solar rotation rates as determined by feature tracking
techniques. We will show the first data sets from the new network.
Title: Center-to-Limb Variations of Small-Scale Magnetic Features
Authors: Denker, C.; Spirock, T. J.; Wang, H.; Goode, P. R.
Bibcode: 2000SPD....31.0804D
Altcode: 2000BAAS...32R.840D
During August/September 1999, we observed continuum images in the
visible (520 nm) and infrared (1600 nm) of various active regions
during their limb-to-limb passage. The images were obtained with the
65 cm vacuum reflector of the Big Bear Solar Observatory and speckle
masking has been applied to obtain almost diffraction limited images
of small-scale magnetic features such as pores, magnetic knots, and
faculae. The infrared images were taken with a new 320 x 240 pixel,
12-bit, 30 fps InGaAs CCD camera. The continuum images are complemented
by videomagnetograms obtained at Ca I (610.3 nm) with the 25 cm vacuum
refractor. We present the first results of a comprehensive study on
the relationship of magnetic field strength and continuum contrast
of small-scale magnetic features as a function of disk position. The
underlying mechanism of small-scale flux tubes is of particular
importance for solar irradiance variations over the 11 year solar
activity cycle.
Title: High Cadence Flare Observations
Authors: Wang, H.; Qiu, J.; Denker, C.; Spirock, T. J.; Chen, H.;
Goode, P. R.
Bibcode: 2000SPD....31.1406W
Altcode: 2000BAAS...32..847W
We analyzed high cadence observations of a C5.7 flare of 1999 August
23 at Big Bear Solar Observatory (BBSO). The observing wavelength was
1.3 Angstroms in the blue wing of Hα line. The observations were made
with a 12-bit SMD camera with a cadence of 33 ms and an image scale of
0.3'' pixel-1. In addition, the time profile of hard X-rays
obtained by BATSE (with the cadence of 1.024 s) and BBSO high resolution
magnetograms are compared with Hα observations to understand detailed
particle precipitations of this event. The important results are:
(1) In Hα -1.3 Angstroms, three flare kernels were observed in the
early phase of the flare. The flare started in a non-magnetic area at
the magnetic neutral line. We may have detected the top of a low-lying
loop which was the initial energy release site. While the other two
kernels may be the footpoints of another overlying flare loop formed
after the magnetic reconnection. (2) We analyzed the temporal behavior
of the three flare kernels in the impulsive phase when hard X-ray
emission was significant. We found that during a 7 s period, the Hα
-1.3 Angstroms brightenings at one of the footpoints showed very good
temporal correlation with the hard X-ray flux variation. Therefore,
from the spatially resolved Hα offband observations, we identified
this flare kernel as the source of hard X-ray emission. (3) From the
footpoint which exhibited best correlation with the HXR, the Hα -1.3
Angstroms emission showed high frequency fluctuation in a time scale
of a few tenths of a second. The amplitude of the fluctuation was more
than three times above the noise. Such fluctuation was not evident in
other flare kernels which did not show good correlation with the hard
X-ray emission. Therefore, the observed high frequency fluctuation
might be the real signature of fine temporal structure related to the
HXR elementary bursts.
Title: Magnetic Topology in November 5, 1998 Two-Ribbon Flare as
Inferred from Ground-Based Observations and Linear Force-Free Field
Modeling
Authors: Yurchyshyn, V. B.; Wang, H.; Qiu, J.; Goode, P. R.; Abramenko,
V. I.
Bibcode: 2000SPD....31.0153Y
Altcode: 2000BAAS...32..810Y
We analyzed the 3D structure of the linear force-free magnetic field in
an active region. A longitudinal magnetogram of AR NOAA 8375 has been
used as the photospheric boundary condition. The Nov 5, 1998 2B/M8.4
two-ribbon flare can be explained in the framework of quadrupolar
reconnection theory: the interaction of two closed magnetic loops which
have a small spatial angle. The energy derived from SXT/YOHKOH data (3
- 6 x 1030 ergs) is one order of magnitude higher than the
lower limit of flare energy predicted by Melrose's model. The latter
estimation was made using the linear force-free extrapolation. It is
suggested that by taking into account the non-linear character of the
observed magnetic field we can increase the lower limit of the magnetic
energy stored in the studied magnetic configuration. The revealed
magnetic configuration allows us to understand the observed location
and evolution of the flare ribbons and the additional energy released
during the gradual phase of the flare, as well. Also, the reconnection
of closed magnetic loops can logically explain the connection between
a two-ribbon flare and the giant X-ray post-flare arch which usually
is observed after flare onset. We emphasize that unlike the Kopp and
Pneuman configuration, the model discussed here doesn't necessarily
need destabilization and opening of the magnetic field. This work was
supported in part by NSF-ATM (97-14796) and NASA (NAG5-4919) grants.
Title: Observational Evidence for Magnetic Dips in Solar Prominences
Authors: Lee, Sangwoo; Yun, H. S.; Kim, Jung-Hoon; Chae, J.; Goode,
P. R.; Choe, G. S.
Bibcode: 2000SPD....31.0148L
Altcode: 2000BAAS...32R.809L
It has been a long-standing mystery in the study of the Sun how cool and
dense plasma material in prominences can be supported against gravity. A
common wisdom has been to assume magnetic field configurations with
magnetic dips which supply an upward magnetic tension. A number of
proposed theoretical models have regarded magnetic dips as a supporting
mechanism of the dense plasma material. Nevertheless, the existence
of magnetic dips in prominences has a scant observational underpinning
mainly because of the difficulty in determining 3-D magnetic fields in
prominences. For the first time, we report observational evidence for
magnetic dips based on the mass motion seen in prominences. We have
found an oscillatory overshooting out of a prominence body, which is
very naturally explained as mass motion along dipped magnetic field
lines sagging under gravity.
Title: A Rapid Magnetic Connectivity Change Observed Before a
Filament Eruption
Authors: Kim, Jung-Hoon; Yun, H. S.; Lee, Sangwoo; Chae, J.; Goode,
P. R.
Bibcode: 2000SPD....31.0267K
Altcode: 2000BAAS...32Q.823K
It has been a mystery what causes a solar prominence eruption. To get an
insight on this problem, we observed an active region filament eruption
in Hα lines (line center, +/- 0.5 { Angstroms}) and longitudinal
magnetograms at Big Bear Solar Observatory. The cadence is about 1
minute each for Hα and magnetogram. During 8 hours of observing run,
we covered complete phases of the filament eruption and an associated
two-ribbon flare. From Hα movies, we found a rapid connectivity
change in a filament thread before its eruption. The thread was
initially highly curved. It suddenly became straightened due to the
rotation of its end. The duration of change was about 30 minutes and
the rotated thread swept 100{\arcsec}x50{\arcsec} area on the solar
surface. After this connectivity change, the filament body split into
two parts, one part erupted, and the two-ribbon flare occurred. Being
associated with the connectivity change, transverse mass motion of about
50 km/s was observed in Hα along the newly connected field lines, and
a cancelling magnetic feature was observed in the vicinity where the
connectivity changed. Flux cancellation began before the connectivity
change, and continued while the connectivity change proceeded. Within 2
hours, the flux decreased by the amount of about 2.0x 1020
Mx. These observational results clearly give direct evidence that
magnetic reconnection takes place prior to eruption. This reconnection
is distinct from the post-eruption reconnection which is believed to
lead to the two-ribbon flare.
Title: First Results from the Big Bear Solar Observatory's Digital
Vectormagnetograph
Authors: Spirock, T. J.; Denker, C.; Chen, H.; Qui, J.; Goode, P. R.;
Wang, H.
Bibcode: 2000SPD....3102109S
Altcode: 2000BAAS...32..830S
During the past three years, the Big Bear Solar Observatory has begun an
aggressive program to upgrade the observatory's instrumentation. In the
forefront of this effort is the development of a highly sensitive, high
cadence, filter based, digital vector magnetograph for the observatory's
10" vacuum-refractor to replace the old video magnetograph to improve
our measurements of the FeI line at 6301A. The hardware is being
replaced by a 512 x 512, 12-bit, 30 frames per second CCD camera and
high quality polarization optics. In addition, software tools are
being written to aid instrument development by quickly evaluating
images (bias, cross talk, etc.) and to generate near real-time vector
magnetograms, which will aid space weather forecasting and the support
of space weather missions. Data acquisition, data calibration and flat
fielding methods will be discussed and quiet sun and active region
magnetograms will be presented.
Title: Active Region Loops Observed with SUMER on Board the SOHO
Authors: Chae, Jongchul; Wang, Haimin; Qiu, Jiong; Goode, Philip R.;
Wilhelm, Klaus
Bibcode: 2000ApJ...533..535C
Altcode:
We study the emission and dynamical characteristics of transition region
temperature plasmas in magnetic loops by analyzing a high-resolution,
limb observation of the active region NOAA 7962. The observations were
performed by the Solar Ultraviolet Measurements of Emitted Radiation
(SUMER) instrument on board the Solar and Heliospheric Observatory
(SOHO). The SUMER observation produced a set of raster scans of the
region, in the four lines, H I Lyβ λ1025, O VI λλ1032, 1038,
and C II λ1037. The data are used to construct intensity, velocity,
and line width maps of the active region, from which more than 10
well-resolved loops are identified and classified into four different
groups. We determine several physical parameters of the loops in each
group such as diameter, length, temperature, line-of-sight plasma
velocity, and nonthermal line broadening. Our results indicate that
both kinds of temperature variations exist in active region loops:
variations from loop to loop and variations along each loop. It is
also found that there is a distinction between stationary loops and
dynamic loops. The dynamic loops have large bulk motions and large
nonthermal line broadenings. Some of the dynamic loops display large
velocity shears with the sign of line-of-sight velocities changing
across the loop axes. These velocity shears appear to represent
rotational motions around the loop axes with velocities of up to 50 km
s-1. There are indications that nonthermal line broadening
is the result of magnetohydrodynamic turbulence inside the loops. Based
on our observations, we postulate that when loops erupt, some of the
kinetic and magnetic energy cascades down to turbulent energy which
would be dissipated as heat.
Title: Non-axisymmetric oscillations of roAp stars
Authors: Bigot, L.; Provost, J.; Berthomieu, G.; Dziembowski, W. A.;
Goode, P. R.
Bibcode: 2000A&A...356..218B
Altcode:
We calculate the effect of a strong dipole magnetic field on
non-axisymmetric oscillations for roAp stars, with a typical range of
photospheric magnetic fields B_p [0.5-1.5] kG. As Dziembowski &
Goode (1996), we find that the oscillations are strongly affected by
such magnetic fields in two different ways. The first one concerns the
stability of modes, which are damped due to dissipation by Alfvénic
waves. It leads to a small imaginary part of the frequency, about
(1-15mu Hz). The real part of the frequencies is also affected and is
greater in the presence of magnetic field, with a shift of about 1-20 mu
Hz. We find that these shifts are strongly influenced by the geometry of
the mode, i.e. the value of the degree l, as it has already been shown
by Dziembowski & Goode (1996), and also by m, the azimuthal degree,
with a significant amplitude. The magnetic field, because it breaks
the spherical symmetry of the problem, raises partially the (2 l +1)
degeneracy of frequency in m. We find that the shift of both the real
and imaginary parts is always greater than in the case of axisymmetric
oscillations (m=0), except for sectoral modes (l=m), for which the
imaginary part is smaller. The second effect of large magnetic fields
is to complicate the mode identification. The perturbations cannot
be represented by pure single spherical harmonic, but by a series of
harmonics due to the angular dependence of the Lorentz force. It is
shown that this mixing of spherical harmonics also depends on the value
of m. However, our calculations do not explain the observed selection
of dipole modes in roAp stars, aligned with the magnetic axis, since
they do not minimize energy losses due to Alfvénic waves.
Title: Minifilament Eruption on the Quiet Sun. I. Observations at
Hα Central Line
Authors: Wang, Jingxiu; Li, Wei; Denker, Carsten; Lee, Chikyin; Wang,
Haimin; Goode, Philip R.; McAllister, Alan; Martin, Sara F.
Bibcode: 2000ApJ...530.1071W
Altcode:
The eruption of miniature filaments on the quiet Sun has been analyzed
from time sequences of digital Hα filtergrams obtained at Big Bear
Solar Observatory during 1997 September 18-24. The 2 days with the
best image quality were selected for this initial study. During
13 hr of time-lapse observations on these 2 days, in an effective
640''x480'' area of quiet Sun close to the disk
center, 88 erupting miniature filaments were identified. On average,
these small-scale erupting filaments have a projected length of 19,000
km, an observed ejection speed of 13 km s-1, and a mean
lifetime of 50 minutes from first appearance through eruption. The
total mass and kinetic energy involved in a miniature filament
eruption is estimated to be 1013 g and 1025
ergs, respectively. They are distinguished from macrospicules by the
same criteria that large-scale filaments, before and during eruption,
are distinguished from surges. Prior to eruption, one end, both ends,
or the midsection of a miniature filament is superposed over a polarity
reversal boundary on line-of-sight magnetograms. We conclude that
miniature filaments are the small-scale analog to large-scale filaments.
Title: Magnetic Topology in November 5, 1998 Two-Ribbon Flare as
Inferred from Ground-Based Observations and Linear Force-Free Field
Modeling
Authors: Yurchyshyn, V.; Wang, H.; Qiu, J.; Goode, P. R.; Abramenko,
V. I.
Bibcode: 2000ESASP.463..463Y
Altcode: 2000sctc.proc..463Y
No abstract at ADS
Title: An Overview of the New Global High-Resolution H-alpha Network
Authors: Steinegger, M.; Hanslmeier, A.; Otruba, W.; Freislich, H.;
Denker, C.; Goode, P. R.; Marquette, W. M.; Varied, J.; Wang, H.;
Luo, G.; Chen, D.; Zhang, Q.
Bibcode: 2000HvaOB..24..179S
Altcode:
In this paper we give a brief overview of the new global high resolution
H-alpha network which was recently established between the Big Bear
Solar Observatory (USA), the Kanzelhoehe Solar Observatory (Austria),
and the Yunnan Astronomical Observatory (China). A short description
of the sites, instruments, and the scientific aims, as well as some
sample data are presented.
Title: Comparison of Transient Network Brightenings and Explosive
Events in the Solar Transition Region
Authors: Chae, Jongchul; Wang, Haimin; Goode, Philip R.; Fludra,
Andrzej; Schühle, Udo
Bibcode: 2000ApJ...528L.119C
Altcode:
The relation between transient network brightenings, known as blinkers,
and explosive events is examined based on coordinated quiet Sun
observations in the transition region line O V λ630 recorded by
the Coronal Diagnostic Spectrometer (CDS), in the transition region
line Si IV λ1402 recorded by the Solar Ultraviolet Measurements of
Emitted Radiation (SUMER) instrument, and in photospheric magnetograms
taken by the Big Bear Solar Observatory videomagnetograph. From these
observations, we find that (1) explosive events, which are traditionally
defined as features with very broad UV line profiles, tend to keep
away from the centers of network brightenings and are mostly located
at the edges of such brightenings, (2) CDS blinkers consist of many
small-scale, short-lived SUMER ``unit brightening events'' with a
size of a few arcseconds and a lifetime of a few minutes, and most
importantly (3) each SUMER unit brightening event is characterized by
a UV line profile that is not as broad as those of explosive events,
but still has significantly enhanced wings. Our results imply that,
like explosive events, individual unit brightening events involve high
velocities, and, hence, blinkers may have the same physical origin
as explosive events. It is likely that transient network brightenings
and explosive events are both due to magnetic reconnection--but with
different magnetic geometries.
Title: On the Correlation between the Orientation of Moving Magnetic
Features and the Large-Scale Twist of Sunpots
Authors: Yurchyshyn, V.; Wang, Haimin; Goode, Philip R.
Bibcode: 2000ESASP.463..459Y
Altcode: 2000sctc.proc..459Y
No abstract at ADS
Title: The New Global High-Resolution Hα Network: First Observations
and First Results
Authors: Steinegger, M.; Denker, C.; Goode, P. R.; Marquette, W. H.;
Varsik, J.; Wang, H.; Otruba, W.; Freislich, H.; Hanslmeier, A.; Luo,
G.; Chen, D.; Zhang, Q.
Bibcode: 2000ESASP.463..617S
Altcode: 2000sctc.proc..617S
No abstract at ADS
Title: Counter-streaming Mass Flow and Transient Brightening in
Active Region Loops
Authors: Qiu, Jiong; Wang, Haimin; Chae, Jongchul; Goode, Philip R.
Bibcode: 1999SoPh..190..153Q
Altcode:
An active region loop system was observed in a decaying active region
for three hours by TRACE and BBSO in a joint campaign on September
27, 1998. Continuous mass motion was seen in Hα offband filtergrams
throughout the three hours, and some UV loops were exhibited transient
brightenings. We find that: (1) cool material was flowing along the
loops at a speed of at least 20 km s−1. Further, in Hα red
and blue wings, we see mass motion along different loops in opposite
directions. This is the first report of a counter-streaming pattern
of mass motion in an Hα loop system. (2) Transient brightenings
of different UV loops at different times were observed at C iv 1550
Å. These brightened UV loops were located in the same region and at
the same altitudes as the Hα loops. The observations show a clear
correlation between the transient brightenings of UV loops and mass
motion in Hα loops. (3) Both footpoints of the loop system were
located in regions of mixed magnetic polarities. Frequent micro-flares
at one footpoint of the loops with small-scale brightenings spreading
along the loop leg were observed before the brightening and rising
of one C iv loop. Similar to the case of a filament, the continuous
mass motion along the loops seems important for maintaining the cool
Hα loop system at coronal height. There may be an indication that the
mass motion in cool Hα loops and the correlated transient brightening
of the active region loops were due to the small-scale chromospheric
magnetic reconnection at the footpoint regions of the loop system.
Title: Studies of Microflares and C5.2 flare of 27 September 1998
Authors: Wang, Haimin; Chae, Jongchul; Qiu, Jiong; Lee, Chik-Yin;
Goode, Philip R.
Bibcode: 1999SoPh..188..365W
Altcode:
On 27 September 1998, Big Bear Solar Observatory (BBSO) and Transition
Region and Coronal Explorer (TRACE) coordinated observations from
16:00 to 19:00 UT to study properties of microflares in AR NOAA
No. 8340. Fortuitously, a C5.2 flare occurred at 16:30 UT in this active
region. Hα and magnetograph movies were obtained at BBSO; C iv 1550
Å, Fe ix 171 Å, and Fe xii 195 Å movies were obtained by TRACE;
both with a cadence about 1 min. In this paper, we concentrate on the
study of magnetic properties of 70 C iv microflares, as well as their
relationship to the C5.2 flare. We obtained the following results: (1)
We found two kinds of microflares: microflares of transient brightenings
with a time scale of 1 to 5 min (impulsive events) and microflares
lasting half an hour or longer (persistent events). Ninety percent of
the microflares are impulsive events. Most of the event in this category
are associated with well defined magnetic neutral lines, but some are
found in non-neutral line areas. All of seven persistent events are
found at parasitic magnetic configurations with inclusions of small
magnetic flux within dominant magnetic flux of opposite polarity. (2)
More than a third of the impulsive microflares occurred near the C5.2
flare site indicating that a local instability is responsible for both
the C5.2 flare and microflares. This indirectly supports the avalanche
theory of flare energy release, which implies that a big flare may be
spatially associated with many small flares.
Title: Extreme-Ultraviolet Jets and Hα Surges in Solar Microflares
Authors: Chae, J.; Qiu, J.; Wang, H.; Goode, P. R.
Bibcode: 1999AAS...194.7906C
Altcode: 1999BAAS...31..963C
We analyzed simultaneous EUV data from the Transition Region And
Coronal Explorer (TRACE) and Hα data from Big Bear Solar Observatory
(BBSO). In the active region studied, we found several EUV jets that
repeatedly occurred where pre-existing magnetic flux was canceled by
newly emerging flux of opposite polarity. The jets look like, but are
usually smaller and shorter lived than Yohkoh soft X-ray jets. The EUV
jets have a typical size of 4000-10,000 km, a transverse velocity of
50-100 km s(-1) , and a lifetime of 2-4 minutes. Each of the jets was
ejected from a loop-like bright EUV emission patch at the moment when
the patch reached its peak emission. We also found dark Hα surges
that are correlated with these jets. A careful comparison, however,
revealed that the Hα jets are not cospatial with the EUV jets. Instead,
the EUV jets are are identified with bright jetlike features in the Hα
line center, which are distinct from dark surges. Our results support
a picture in which Hα surges and EUV jets represent different kinds
of plasma ejection --- cool and hot plasma ejections along different
field lines --- which must be dynamically connected to each other. We
emphasize the importance of observed flux cancellation and a small
erupting filament in understanding the acceleration mechanisms of EUV
jets and Hα surges. This work is partially supported by NSF under
grant ATM-97-14796 and NASA under grants NAG5-4919, NAG5-7349, and
NAG5-7350 to BBSO.
Title: Study of Umbral Dots at 1.6 Micron
Authors: Wang, J. S.; Wang, H.; Denker, C.; Spirock, T.; Goode, P.
Bibcode: 1999AAS...194.9305W
Altcode: 1999BAAS...31R.989W
We used a 320 by 240 InGaAs IR camera and a broadband filter centered at
1.565 micron to carry out a sequence of near IR observations at Big Bear
Solar Observatory. The target is a delta sunspot and our objective is
to study the properties of umbral dots in the opacity minimum. Because
of the lower scattering light in IR, we can resolve the very center of
the umbra. We discuss the contrasts, sizes, lifetimes and proper motions
of umbral dots observed in IR and compared with visible observations.
Title: Ultraviolet Flare Loop Systems in an Eruptive Event
Authors: Qiu, J.; Wang, H.; Chae, J.; Lee, C.; Goode, P. R.
Bibcode: 1999AAS...194.7904Q
Altcode: 1999BAAS...31..963Q
The BBSO/TRACE joint campaign on September 27, 1998 observed an
eruptive flare event which lasted for half an hour. The observation
covered several ultraviolet lines from transition region and Hα
line center and off-band emissions from chromosphere with high
spatial resolution which allows detailed study on the flare plasma
at wide temperature range. Various flare loop systems are found in
the active region depicting different scenarios of the event. The
flare was started by low atmosphere explosive reconnection which
triggered vehement loop eruption, heating of both large scale and
low-lying pre-existent loops, and mass ejection of both hot (up to
10(6) K) and cool (10(4) K) plasmas. Due to reconnection of open field
lines, new flaring loop archade was formed after the eruption and was
clearly seen in EUV emissions. From high resolution UV, EUV and Hα
filtergrams, fine structure of both low-lying and coronal loops can be
identified. The multi-wavelength observations on this event enable us
to distinguish different mechanisms of energy transfer in different
loop systems displaying different radiative and dynamic behaviours,
and to investigate the early stage of the flare when lower atmosphere
instability is essential in triggering the major flare and the relation
between lower and higher atmospheres is complex. This work is supported
by NSF under grants ATM-9628862 and ATM-9713359, and NASA under grants
NAG5-5036 and NAG5-7085, and ONR under grant N00014-97-1-1037.
Title: New Vectormagnetographs at the Big Bear Solar Observatory
Authors: Spirock, T. J.; Denker, C.; Wang, J.; Chen, H.; Wang, H.;
Goode, P. R.
Bibcode: 1999AAS...194.7607S
Altcode: 1999BAAS...31R.957S
During the past two years, the Big Bear Solar Observatory has begun an
aggressive program to upgrade the observatory's instrumentation. In
the forefront of this effort are improvements to the current
vectormagnetograph and the development of two new vectormagnetographs
systems - one in visible light and one in near infra red. In the
first case, the current filter-based video-magnetograph, on the 10"
vacuum-refractor, is being replaced by a 1k by 1k, 12-bit, 15 frames pre
second CCD camera, and higher quality polarization optics to improve
our measurments using the CaI line at 6103 Angstroms. Secondly, a
Fabry-Perot based imaging magnetograph with a spacial resolution of
0.15 arc-sec per pixel having a temporal resolution of approximately
1 min. for the Stokes-V and approximately 4 min. for the full Stokes
vector with a band-pass of 80m Angstroms is being developed for the
26" vacuum-reflector to scan the FeI line at 6302.5 Angstroms. In the
near infra red, an automated spectrograph based vectormagnetograph,
using a 12-bit, 320 by 240, 30 frames per second InGaAs CCD camera,
is being developed to study the FeI lines at 1.56485 microns and
1.56529 microns. Current plans and the status of each instrument will
be discussed and test results will be presented.
Title: Large-Scale Structures of Solar Flares
Authors: Denker, C.; Marquette, W.; Wang, H.; Goode, P. R.;
Johannesson, A.
Bibcode: 1999AAS...194.2207D
Altcode: 1999BAAS...31..860D
Since December 1997, the Big Bear Solar Observatory (BBSO) has
provided daily, contrast enhanced, Hα full disk images of unsurpassed
quality, temporal resolution of about 30 s, and spatial resolution of
about 2 arcsec which allow us to study the evolution of small-scale
structures and low-contrast features. This data set has the right
qualities to allow us to study large-scale phenomena associated with
major solar flares such as Moreton waves, transient brightening of
the Hα network, filament eruptions and disappearances. In 1998, 31
flares of magnitude M3.0 or larger were observed by the Geosynchronous
Operational Environmental Satellites (GOES). Eight of them occurred
during the typical observing hours at BBSO and seven were actually
covered by Hα full disk observations presented here. We provide a
detailed description of various chromospheric disturbances initiated by
the flares, the influence of magnetic fields on their appearance, and
their association with coronal mass ejections. This work was supported
by ONR under grant N00014-97-1-1037, by NSF under grant ATM 97-14796,
and by NASA under grant NAG 5-4919 and NAG 5-7350.
Title: Studies of Microflares and C5.2 Flare of September 27, 1998
Authors: Wang, H.; Qiu, J.; Chae, J.; Lee, C.; Goode, P.
Bibcode: 1999AAS...194.7907W
Altcode: 1999BAAS...31..964W
On September 27, 1998, Big Bear Solar Observatory (BBSO) and Transition
Region and Coronal Explorer (TRACE) coordinated observations from
16:00 to 19:00 UT to study properties of microflares on AR NOAA
#8340. Fortuitously, a C5.2 flare occurred at 16:30UT in this active
region. Hα and magnetograph movies were obtained at BBSO; CIV 1550
Angstroms, FeIX 171 Angstroms, and FeXII 195 Angstroms movies were
obtained by TRACE; both with a cadence about 1 minute. In this
paper, we concentrate on the study of magnetic properties of 70
CIV microflares, as well as their relationship to the C5.2 flare. We
obtained the following results: (1) We found two kinds of microflares:
(a) microflares of transient brightenings with a time scale of
1 to 5 minutes (impulsive events). 90% of the microflares are of
this form. Most of the events in this category are associated with
well defined magnetic neutral lines, although a few of them are not
located near a neutral line; and (b) microflares lasting half an hour
or longer (persistent events). Seven events in three clusters belong to
this category. All three sites are associated with a dominant magnetic
polarity plus a very small element of opposite polarity. (2) More than
a third of the impulsive microflares occurred near the C5.2 flare site
indicating that a local instability is responsible for both the C5.2
flare and microflares. This indirectly support the avalanche theory of
flare energy release, which predicts that a big flare may be associated
with many small flares. Based on the morphologies of those events, we
postulate that the persistent events may be due to loop interaction;
while impulsive events may be associated with sheared loop structure.
Title: Solar Asphericities from BBSO Synoptic Data and MDI Splittings
Authors: Goode, P. R.; Dziembowski, W. A.; Marquette, W.
Bibcode: 1999AAS...194.4205G
Altcode: 1999BAAS...31..882G
Beneath the photosphere, on average the Sun is almost a perfect
sphere. Historically, the main photospheric asymmetry studied has been
the magnetic activity cycle as reflected in the Maunder butterfly
diagram. In recent years, more subtle signatures of asymmetries
varying with the solar cycle have been found. We have used temporal
averages of BBSO synoptic maps from the activity minimum which has just
ended to extract the low degree Legendre dependence of the data. We
present preliminary comparisons of the degree of correlation between
these Legendre coefficients varying through the solar cycle with the
temporally corresponding low degree Legendre coefficents from MDI
splitting data to enable us to garner another perspective, the role
of the magnetic field in the Sun's cycle dependent asphericity.
Title: Acoustic Imaging in Helioseismology
Authors: Chou, Dean-Yi; Chang, Hsiang-Kuang; Sun, Ming-Tsung; LaBonte,
Barry; Chen, Huei-Ru; Yeh, Sheng-Jen; TON Team; Tang, Heng-Tai; Shiu,
Wei-Cheng; Chen, Yi-Liang; Jimenez, Antonio; Rabello-Soares, Maria
Cristina; Ai, Guoxiang; Wang, Gwo-Ping; Goode, Philip; Marquette,
William; Ehgamberdiev, Shuhrat; Khalikov, Shukur
Bibcode: 1999ApJ...514..979C
Altcode:
The time-variant acoustic signal at a point in the solar interior can
be constructed from observations at the surface, based on the knowledge
of how acoustic waves travel in the Sun: the time-distance relation
of the p-modes. The basic principle and properties of this imaging
technique are discussed in detail. The helioseismic data used in
this study were taken with the Taiwan Oscillation Network (TON). The
time series of observed acoustic signals on the solar surface is
treated as a phased array. The time-distance relation provides the
phase information among the phased array elements. The signal at any
location at any time can be reconstructed by summing the observed
signal at array elements in phase and with a proper normalization. The
time series of the constructed acoustic signal contains information on
frequency, phase, and intensity. We use the constructed intensity to
obtain three-dimensional acoustic absorption images. The features in
the absorption images correlate with the magnetic field in the active
region. The vertical extension of absorption features in the active
region is smaller in images constructed with shorter wavelengths. This
indicates that the vertical resolution of the three-dimensional images
depends on the range of modes used in constructing the signal. The
actual depths of the absorption features in the active region may be
smaller than those shown in the three-dimensional images.
Title: Extreme-Ultraviolet Jets and Hα Surges in Solar Microflares
Authors: Chae, Jongchul; Qiu, Jiong; Wang, Haimin; Goode, Philip R.
Bibcode: 1999ApJ...513L..75C
Altcode:
We analyzed simultaneous EUV data from the Transition Region and Coronal
Explorer and Hα data from Big Bear Solar Observatory. In the active
region studied, we found several EUV jets that repeatedly occurred where
pre-existing magnetic flux was ``canceled'' by newly emerging flux of
opposite polarity. The jets look like Yohkoh soft X-ray jets, but are
smaller and shorter lived than X-ray jets. They have a typical size
of 4000-10,000 km, a transverse velocity of 50-100 km s-1,
and a lifetime of 2-4 minutes. Each of the jets was ejected from a
looplike bright EUV emission patch at the moment that the patch reached
its peak emission. We also found dark Hα surges that are correlated
with these jets. A careful comparison, however, revealed that the Hα
surges are not cospatial with the EUV jets. Instead, the EUV jets are
identified with bright jetlike features in the Hα line center. Our
results support a picture in which Hα surges and EUV jets represent
different kinds of plasma ejection--cool and hot plasma ejections along
different field lines--which must be dynamically connected to each
other. We emphasize the importance of observed flux cancellation and
a small erupting filament in understanding the acceleration mechanisms
of EUV jets and Hα surges.
Title: Magnetic Effects on Stellar Oscillations
Authors: Bigot, L.; Provost, J.; Berthomieu, G.; Dziembowski, W. A.;
Goode, P. R.
Bibcode: 1999RoAJ....9S.129B
Altcode:
We calculate the effect of a strong dipole magnetic field (0.5-1.5 kG)
on stellar oscillations. To do this, we adopt a boundary layer approach,
by taking into account the dynamical effect of the magnetic field only
in a very thin layer, at the star surface. The magnetic field leads to
a damping of oscillations due to Alfvénic wave losses of energy. It
appears then an imaginary part of the frequency (~1-15 ?Hz) and a shift
of the real part (~1-15 ?Hz). The mode identification is complicated:
since the Lorentz force depends on the colatitude, one must represent
the oscillations by a linear combination of. We tackled non-axisymmetric
oscillations (m0) and then generalized the result of Dziembowski and
Goode (1996). These magnetic effects strongly depend on the geometric
nature of the mode (degree and azimuthal order m). We apply our
calculatio ns to roAp stars, whose oscillations appear essentially
as dipole modes ( = 1, m = 0) aligned with the magnetic axis. This
work does not explain this geometrical preference, since it does not
minimize Alfvénic losses of energy. However, it shows that one must
take into account the magnetic field to identify modes in roAp stars.
Title: Synoptic Hα Full-Disk Observations of the Sun from Big
Bear Solar Observatory - I. Instrumentation, Image Processing,
Data Products, and First Results
Authors: Denker, C.; Johannesson, A.; Marquette, W.; Goode, P. R.;
Wang, H.; Zirin, H.
Bibcode: 1999SoPh..184...87D
Altcode:
The Big Bear Solar Observatory (BBSO) has a long tradition of synoptic
full-disk observations. Synoptic observations of contrast enhanced
full-disk images in the Ca ii K-line have been used with great success
to reproduce the H i Lα irradiance variability observed with the
Upper Atmosphere Research Satellite (UARS). Recent improvements in
data calibration procedures and image- processing techniques enable us
now to provide contrast enhanced Hα full-disk images with a spatial
resolution of approximately 2'' and a temporal resolution of up to 3
frames min−1.
Title: Properties of Sunspots and Pores
Authors: Denker, C.; Spirock, T.; Goode, P.; Wang, H.
Bibcode: 1999ASPC..183..124D
Altcode: 1999hrsp.conf..124D
No abstract at ADS
Title: MDI Signs of the Rise of Cycle 23
Authors: Goode, P. R.; Dziembowski, W. A.
Bibcode: 1999soho....9E..60G
Altcode:
We find sizeable, systematic changes in solar oscillation frequencies
implying significant changes in the spherically symmetric structure
of the Sun's outer layers, as well as in its asphericity through
a P18 Legendre distortion. We conducted a search for corresponding
asymmetries in Ca II K data from BBSO. We found tight temporal and
angular correlations of the respective asphericities up through
P10. This result emphasizes the direct role of the magnetic field in
producing the frequency changes. We carried out inversions of the
frequency differences and the splitting coefficients assuming that
the source of the evolving changes is a varying stochastic magnetic
field. With respect to the most recent activity minimum, we detected
a significant perturbation in the spherical part at a depth of 25-100
Mm which may be interpreted as being due to magnetic field changes of
about 40 KG and/or relative temperature perturbations of 6x105. Further,
we found somewhat less significant evidence for a shallower, asymmetric
perturbation.
Title: The Excitation of Solar Oscillations -- Observations and
Simulations
Authors: Goode, P.; Strous, L.; Rimmele, T.; Stein, R.; Nordlund, Å.
Bibcode: 1999ASPC..183..456G
Altcode: 1999hrsp.conf..456G
No abstract at ADS
Title: The Excitation of Solar Oscillations
Authors: Strous, Louis H.; Goode, Philip R.; Rimmele, Thomas R.
Bibcode: 1999soho....9E..81S
Altcode:
We investigate seismic events, bursts of seismic waves that are
generated locally just below the solar surface and that we detect
travelling up through the photosphere. We identify 646 seismic events,
which are associated with intergranular lanes and have an extent
of on average about 10 minutes and 3 Mm. Their birth rate is about
10-16 m-2 s-1. The observed upwardly travelling seismic flux in the
average event (as derived from velocities in the p-mode region of
k-omega space) is followed after about 5 minutes by some reflected
downward flux. Only some of the energy generated in the hypocenter of
the event below the surface travels up for us to see. We propose that
this energy is converted into surface (f-mode-like) waves, while the
unseen, initially downward going energy is eventually transformed
into p-modes. The seismic events at the surface contain about 5 *
1019 J of seismic energy each, which corresponds to an average
flux level of about 4 kW/m2 over the whole surface. The initially
downward directed energy flow is likely substantially greater, and
is then in the same ballpark as the estimate of Libbrecht (1988) for
the power required to sustain the p-mode spectrum. We find a roughly
linear relation between the peak seismic flux and the peak downward
convective velocity associated with each seismic event, which is
not equal to the v8 relation found theoretically by Lighthill (1952)
for stochastic excitation by turbulent convection.
Title: Solar Cycle Onset Seen in SOHO Michelson Doppler Imager
Seismic Data
Authors: Dziembowski, W. A.; Goode, P. R.; di Mauro, M. P.; Kosovichev,
A. G.; Schou, J.
Bibcode: 1998ApJ...509..456D
Altcode:
We have analyzed time changes in centroid frequencies and multiplet
frequency splittings of solar oscillations determined with the Michelson
Doppler Imager instrument (MDI) on SOHO. The data were divided into
five consecutive 72 day sets covering the period from 1996 May 1
through 1997 April 25. We have detected a significant trend in the
a4 and a6 frequency splitting coefficients,
which reflects a decrease in the P4 distortion (described by
the fourth-degree Legendre polynomial of colatitude) and an increase
in the P6 distortion. The rise of the latter distortion
seems to coincide precisely with the rise in the number of new cycle
sunspots. Such sharp and detailed clues to activity onset are new and do
not exist in splitting data from the rising phase of the last cycle. The
relative differences among the solar radii inferred from the f-mode
frequencies from the five sets (at most 6 × 10-6 or 4 km)
are formally significant, reaching a minimum during the observed period.
Title: New Digital Magnetograph At Big Bear Solar Observatory
Authors: Wang, H.; Denker, C.; Spirock, T.; Goode, P. R.; Yang, S.;
Marquette, W.; Varsik, J.; Fear, R. J.; Nenow, J.; Dingley, D. D.
Bibcode: 1998SoPh..183....1W
Altcode:
A new digital magnetograph system has been installed and tested at
Big Bear Solar Observatory. The system uses part of BBSO's existing
videomagnetograph (VMG) system: a quarter wave plate, a ferro-electric
liquid crystal to switch polarizations, and a 0.25 Å bandpass Zeiss
filter tuned at Ca i 6103 Å. A new 256×256 pixels, 12-bit Dalsa
camera is used as the detector and as the driver to switch the liquid
crystal. The data rate of the camera is 90 frames s−1. The camera
is interfaced to a Pentium-166 PC with a μTech imaging board for data
acquisition and analysis. The computer has 128 MByte of RAM, and up to
700 live images can be stored in memory for quick post-exposure image
processing (image selection and alignment). We have significantly
improved the sensitivity and spatial resolution over the old BBSO
VMG system. In particular: (1) New digital image data are in 12 bits
while the video signal is digitized as 8 bits. Polarizations weaker
than 1% can not be detected by a single pair subtraction in the video
system. The digital system can detect a polarization signal of about
0.3% by a single pair subtraction. (2) Data rate of the digital system
is 90 frames s−1, that of the video system is 30 frames s−1. So
the time difference between two polarizations is reduced in the new
system. Under good seeing conditions, the data rate of 90 frames
s−1 ensures that most of the wavefront distortions are `frozen'
and fairly closely the same for the left and right circular polarized
image pairs. (3) Magnetograms are constructed after image selection
and alignment. We discuss the characteristics of this new system. We
present the results of our first tests to reconstruct magnetograms with
speckle interferometric techniques. We also present some preliminary
results on the comparison of facular/micropore contrasts and magnetic
field structure. The experiment with this small detector lays ground
for a larger format digital magnetograph system at BBSO, as well as
a future Fabry-Pérot system, which will be able to scan across the
spectral line.
Title: On the accuracy of helioseismic determination of solar helium
abundance
Authors: Richard, O.; Dziembowski, W. A.; Sienkiewicz, R.; Goode,
Philip R.
Bibcode: 1998A&A...338..756R
Altcode:
The Helium abundance in the solar envelope is one of the most important
seismic observables. We investigate the accuracy of its determination
taking into account uncertainties in the data and in the inversion
procedure. Our best value for the helium abundance in the photosphere is
Ysun=0.248. The estimated uncertainty of 0.002 is dominated
by uncertainties in the inversion. This does not account for possibly
larger inaccuracies in the thermodynamical data.
Title: Chromospheric Upflow Events Associated with Transition Region
Explosive Events
Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip
R.; Schühle, Udo
Bibcode: 1998ApJ...504L.123C
Altcode:
Transition region explosive events are considered to be a manifestation
of small-scale magnetic reconnection ubiquitously occurring--even in
the quiet Sun. In this paper, we report a close association between
transition region explosive events and chromospheric upflow events seen
in Hα. From a comparison of the Big Bear Solar Observatory (BBSO)
Hα spectrograph data and the Solar and Heliospheric Observatory
(SOHO) / Solar Ultraviolet Measurements of Emitted Radiation (SUMER)
data, we found a succession of chromospheric upflow events at sites
where repeated explosive events occurred. Individual chromospheric
events appear as compact dark features that are best visible in
Hα-0.5 Å and that have a size of 2"-3" and a lifetime of 1-2
minutes. They are characterized by an upward motion of 15-30 km
s-1, a temperature of 104 K, a mass density
of 1×10-13 g, and a nonthermal velocity less than 10
km s-1. Unlike spicules, which display descending motion
following their ascending phase, these upflow events are not followed
by noticeable redshifts. ``Hα jets'' at -1.0 Å studied by Wang et
al. appear to be a special case of this kind of chromospheric upflow
event. The physical characteristics of chromospheric upflow events and
their close association with transition region explosive events suggest
that chromospheric upflow events may be the manifestation of cool plasma
material flowing into magnetically diffusive regions, while explosive
events represent hot plasma material flowing out of the same regions.
Title: Photospheric Magnetic Field Changes Associated with Transition
Region Explosive Events
Authors: Chae, Jongchul; Wang, Haimin; Lee, Chik-Yin; Goode, Philip
R.; Schühle, Udo
Bibcode: 1998ApJ...497L.109C
Altcode:
From a comparison of the Solar and Heliospheric Observatory SUMER
spectral data and a time series of Big Bear Solar Observatory
magnetograms, we present observational clues to the physical origin of
transition region explosive events. First, explosive events rarely occur
in the interior of strong magnetic flux concentrations but rather are
preferentially found in regions with weak and mixed polarity fluxes that
display magnetic neutral lines. Second, the majority of explosive events
happen during the ``cancellation'' of photospheric magnetic flux. Third,
there is a strong tendency for explosive events to occur repeatedly, as
bursts, while local photospheric magnetic flux continuously decreases
because of cancellation. These results strongly support the idea that
transition region explosive events are a manifestation of magnetic
reconnection occurring in the quiet Sun. Furthermore, one may infer from
the third result that the explosive events represent repetitive fast
magnetic reconnections in the transition region, which are initiated
by slow magnetic reconnections occurring beneath.
Title: Contrast of Faculae at 1.6 Microns
Authors: Wang, Haimin; Spirock, Thomas; Goode, Philip R.; Lee, Chikyin;
Zirin, Harold; Kosonocky, Walter
Bibcode: 1998ApJ...495..957W
Altcode:
We followed Active Region NOAA 7981 from 1996 July 27 to 1996 August
7 at Big Bear Solar Observatory. During the region's limb-to-limb
passage, images at 1.6 μm, 6103 Å, and CaK, as well as line-of-sight
magnetograms were obtained every day to study the variation of
facular/plage contrast and its relationship to magnetic fields. Our
1.6 μm images were observed by a high-quality 320 × 240 PtSi/Si
detector, which produces extremely uniform images. Our data agree with
the early results of Foukal et al. in several aspects: (1) at 1.6 μm,
some faculae are dark at solar disk center and all become bright when
they are close to the limb; (2) the changeover occurs approximately
at cos θ = 0.5-0.7 (3) the threshold of magnetic flux required to
produce a dark structure at 1.6 μm is about 5 × 1018
Mx. Equally important, our result is different from that of Foukal et
al. on an important issue: among about 150 elements studied near the
disk center, only four of these IR dark faculae show no contrast in
the visible continuum. Other elements show dark contrasts in both 1.6
μm and the visible continuum, if there is sufficient resolution in
the data. However, darkening of weaker (lower flux) elements are more
obvious at IR and most bright points seen at red continuum disappear at
IR. These findings do confirm that 1.6 μm images reveal new aspects
of photospheric magnetic structure. In this paper, we also present a
quantitative relationship between the dark contrast of 1.6 μm faculae
and magnetic field strengths at the disk center, as well as the contrast
variation of IR faculae as a function of the disk position.
Title: On the Origin of Solar Oscillations
Authors: Goode, Philip R.; Strous, Louis H.; Rimmele, Thomas R.;
Stebbins, Robin T.
Bibcode: 1998ApJ...495L..27G
Altcode: 1998astro.ph..1008G
We have made high-resolution observations of the Sun in which we
identify individual sunquakes and see power from these seismic events
being pumped into the resonant modes of vibration of the Sun. A typical
event lasts about 5 minutes. We report the physical properties of
the events and relate them to theories of the excitation of solar
oscillations. We also discuss the local seismic potential of these
events.
Title: The Solar Activity Cycle
Authors: Goode, Philip R.
Bibcode: 1998ad...rept.....G
Altcode:
The three accomplishments are: (1) Observing the source of solar
oscillations and detailing the properties and uses of the seismic events
on the Sun, (2) The most accurate infrared observations made of the Sun
which reveal the true properties of solar faculae which is important in
efforts to understand the solar cycle variation of the Sun's luminosity,
and (3) Treatment of the seismic properties of the Sun's core which
seem to apply a deficiency in standard electro-weak physics. Also,
SOHO data were used to determine the seismic radius of the Sun.
Title: Synoptic Observing Programs at Big Bear Solar Observatory
Authors: Wang, Haimin; Goode, Philip R.
Bibcode: 1998ASPC..140..497W
Altcode: 1998ssp..conf..497W
No abstract at ADS
Title: Solar Asymmetries from SOHO/MDI Splitting Data
Authors: Goode, P. R.; Dziembowski, W. A.; DiMauro, M. P.; Kosovichev,
A. G.; Schou, J.
Bibcode: 1998ESASP.418..887G
Altcode: 1998soho....6..887G
No abstract at ADS
Title: Solar Asymmetries from SOHO/MDI Splitting Data
Authors: Dziembowski, W. A.; Goode, P. R.; Di Mauro, M. P.; Kosovichev,
A. G.; Schou, J.
Bibcode: 1998ESASP.418..887D
Altcode: 1998soho....6..887D
Systematic changes in p-mode frequencies through the solar cycle
have been discovered during the previous high activity phase. Most
significant changes were found in the even-a coefficients of
the fine structure in the oscillation spectra (Kuhn, 1988;
and Libbrecht and Woodard, 1990). We analyzed time changes in
frequencies determined with the SOHO/MDI instrument. The data were
divided into five 72-day sets covering (1) 5/1/96-7/11/96, (2)
7/12/96-9/21/96, (3) 9/22/96-12/2/96, (4) 12/3/96-2/12/97, and (5)
2/13/97-4/25/97. The splitting coefficients ak are defined by
nuvlosell,n,m-bar nuell,n = sum{k = 1}
ak {cal P}kell(m), where {cal P} are
are orthogonal polynomials (see Ritzwoller and Lavely 1991 and Schou,
et al. 1994). We analyzed behavior of the even order coefficients,
a2k, which arise from the respective, P2k
(cos θ), distortion of the Sun's structure. We found a significant
trend in behavior of the a4 and a6 coefficients,
which reflects a decrease of the P4 and an increase of the
P6 distortions. This trend is the same as seen in the BBSO
data (Libbrecht and Woodard, 1990) between 1986 and 1988 i.e. at the
onset of the previous activity phase. The trend in a2 is
not so apparent. The centroid frequencies, bar nuell,n, as
already reported by Kosovichev et al. (1998), exhibit small nonmonotonic
variations. The relative differences in solar radius inferred from the
f-mode frequencies in the five sets (at most 5 times 10-6)
are formally significant, but again there is no trend.
Title: Precise Determination of the Solar Helium Abundance by
Helioseismology
Authors: Richard, O.; Dziembowski, W. A.; Sienkiewicz, R.; Goode,
Philip R.
Bibcode: 1998ESASP.418..517R
Altcode: 1998soho....6..517R
Helium abundance in the solar envelope is one of the most important
seismic observables. We investigate the accuracy of its determination
taking into account uncertainties in data and in the inversion
procedure. Our best value for the helium abundance in the photosphere
is Yodot = 0.248. The estimated uncertainty of 0.002 is
dominated by uncertainties in the inversion. This does not account
for possibly larger inaccuracies in thermodynamical data.
Title: Local Helioseismology of the Sun's Seismic Events
Authors: Goode, P. R.
Bibcode: 1998IAUS..185..183G
Altcode:
We have made high resolution observations of the Sun in which we
identify individual sunquakes and see that the power from the quakes is
sufficient to drive the Sun's oscillation spectrum. These seismic events
originate in the dark intergranular lanes. Furthermore, we observed
that the seismic events were preceeded by a further darkening of an
already dark lane, and on the temporal leading edge of the seismic
event there is a still further, and more abrupt darkening. From this,
we argue that the excitation of the resonant modes was caused by the
occasional, catastrophic cooling and collapse of the lanes. We have
recently observed sunquake energy being directly pumped into the
resonant modes of vibration of the Sun. We also report the physical
properties of the events and relate them to theories of the excitation
of solar oscillations. We show that even a weak, local magnetic field
is sufficent to partially suppress the sunquakes. We discuss the
local helioseismic results focussing on regions of weak and very weak
magnetic fields.
Title: Determination of the Sun's Seismic Radius from the SOHO
Michelson Doppler Imager
Authors: Schou, J.; Kosovichev, A. G.; Goode, P. R.; Dziembowski, W. A.
Bibcode: 1997ApJ...489L.197S
Altcode:
Dopplergrams from the Michelson Doppler Imager (MDI) instrument on board
the SOHO spacecraft have been used to accurately measure frequencies of
the Sun's fundamental (f) mode in the medium angular degree range, l =
88--250. The comparison of these frequencies with the corresponding
frequencies of the standard solar models suggests that the apparent
photospheric solar radius (695.99 Mm) used to calibrate the models
should be reduced by approximately 0.3 Mm. The precise value of the
seismologically determined solar radius depends on the description
of the subsurface layer of superadiabatic convection. The discrepancy
between the "seismic" and apparent photospheric radii is not explained
by the known systematic errors in the helioseismic and photospheric
measurements. If confirmed, this discrepancy represents an interesting
new challenge to theories of solar convection and solar modeling.
Title: New Digital Magnetograph at Big Bear Solar Observatory
Authors: Wang, Haimin; Denker, Carsten; Spirock, Thomas; Yang, Shu;
Goode, Philip
Bibcode: 1997SPD....28.1503W
Altcode: 1997BAAS...29..919W
A new magnetograph system has been installed and tested at Big Bear
Solar Observatory. The system uses part of BBSO's existing VMG
system: a quarter wave plate, a Ferro-Electric Liquid Crystal to
switch polarizations, and a 0.25A bandpass Zeiss filter tuned at CaI
6103A. A 256 by 256 12-bit Dalsa camera is used as the detector and
as the driver to switch the liquid crystal. The data rate of the
camera is 90 frames/s. The camera is interfaced by a Pentium-166
with a Mutech imaging board for data acquisition and analyses. The
computer has 128mb of ram, up to 700 live images can be stored in the
memory for a quick post-exposure image processing (image selection and
alignment). We have improved the sensitivity and spatial resolution
significantly over the old BBSO VMG system for the following reasons:
(1) new digital image data is in 12 bits while the video signal is below
8 bits. Polarizations weaker than 1% can not be detected by a single
pair subtraction in the video system. The digital system can detect a
polarization signal below 0.1% by a single pair subtraction. (2) Data
rate of the digital system is 90 frames/s, that of the video system
is 30 frames/s. So the time difference between two polarizations is
reduced in the new system. Under good seeing conditions, the data rate
of 90 frames/s ensures that the wavefront distortions are "frozen"
and approximately the same for the left and right circular polarized
image pairs. (3) Magnetograms are constructed after image selection and
alignment. The same system has potential for further imaging processing,
e.g. image de-stretch, and speckle interferometry. Preliminary results
will be presented at the meeting.
Title: New Whole Earth Telescope observations of CD-24 7599: steps
towards delta Scuti star seismology
Authors: Handler, G.; Pikall, H.; O'Donoghue, D.; Buckley, D. A. H.;
Vauclair, G.; Chevreton, M.; Giovannini, O.; Kepler, S. O.; Goode,
P. R.; Provencal, J. L.; Wood, M. A.; Clemens, J. C.; O'Brien, M. S.;
Nather, R. E.; Winget, D. E.; Kleinman, S. J.; Kanaan, A.; Watson,
T. K.; Nitta, A.; Montgomery, M. H.; Klumpe, E. W.; Bradley, P. A.;
Sullivan, D. J.; Wu, K.; Marar, T. M. K.; Seetha, S.; Ashoka, B. N.;
Mahra, H. S.; Bhat, B. C.; Babu, V. C.; Leibowitz, E. M.; Hemar,
S.; Ibbetson, P. A.; Mashal, E.; Meistas, E. G.; Dziembowski, W. A.;
Pamyatnykh, A. A.; Moskalik, P.; Zola, S.; Pajdosz, G.; Krzesinski,
J.; Solheim, J. E.; Bard, S.; Massacand, C. M.; Breger, M.; Gelbmann,
M. J.; Paunzen, E.; North, P.
Bibcode: 1997MNRAS.286..303H
Altcode:
92h of new Whole Earth Telescope observations have been acquired for the
delta Scuti star CD-24 7599. All the seven pulsation modes reported by
Handler et al. are confirmed. However, significant amplitude variations
which are not caused by beating of closely spaced frequencies occurred
within two years. Analysing the combined data of both WET runs,
we detect six further pulsation modes, bringing the total number
up to 13. We also examine our data for high-frequency pulsations
similar to those exhibited by rapidly oscillating Ap stars, but we
do not find convincing evidence for variability in this frequency
domain. From new colour photometry and spectroscopy we infer that
CD-24 7599 is a hot main-sequence delta Scuti star with approximately
solar metallicity and vsini=52& plusmn2kms^-1. We cannot yet
propose a definite pulsation mode identification, but we report the
detection of a characteristic frequency spacing between the different
modes. We ascribe it to the simultaneous presence of l=1 and l=2
modes of consecutive radial order. A comparison of this frequency
spacing with frequencies of solar-metallicity models, as well as
stability analysis, allows us to constrain tightly the evolutionary
state of CD-24 7599. It is in the first half of its main-sequence
evolution, and has a mass of 1.85 +/-0.05 M_solar and a mean density of
rho^-=0.246+/-0.020rho^-_solar. This yields a seismological distance
of 650 +/- 70 pc, which is as accurate as distance determinations
for delta Scuti stars observed in clusters. Most of the pulsation
modes are pure p modes of radial order k=4-6, but the g_1 mode of
l=2 is likely to be excited and observed as well. Since a significant
contribution to this mode's kinetic energy comes from the outer part
of the convective core, CD-24 7599 becomes particularly interesting
for testing convective overshooting theories.
Title: Seismic sounding of the solar core: purging the corruption
from the Sun's magnetic activity.
Authors: Dziembowski, W. A.; Goode, P. R.
Bibcode: 1997A&A...317..919D
Altcode:
Probing the structure and rotation of the solar core is one of the
greatest challenges to helioseismology. We show that the seismic
information in the observed low degree solar oscillations which probe
the core is severely contaminated. This contamination arises from the
Sun's near surface magnetic activity. The effect on the oscillation
frequencies varies with the solar cycle-vanishing at solar minimum
and growing with increasing surface activity. We demonstrate that this
contamination can be quantified and removed after determining the fine
structure of the entire oscillation spectrum.
Title: Observation of the excitation of solar oscillations
Authors: Goode, Philip R.; Strous, Louis H.
Bibcode: 1996BASI...24..223G
Altcode:
No abstract at ADS
Title: The Seismic Structure of the Sun
Authors: Gough, D. O.; Kosovichev, A. G.; Toomre, J.; Anderson,
E.; Antia, H. M.; Basu, S.; Chaboyer, B.; Chitre, S. M.;
Christensen-Dalsgaard, J.; Dziembowski, W. A.; Eff-Darwich, A.;
Elliott, J. R.; Giles, P. M.; Goode, P. R.; Guzik, J. A.; Harvey,
J. W.; Hill, F.; Leibacher, J. W.; Monteiro, M. J. P. F. G.; Richard,
O.; Sekii, T.; Shibahashi, H.; Takata, M.; Thompson, M. J.; Vauclair,
S.; Vorontsov, S. V.
Bibcode: 1996Sci...272.1296G
Altcode:
Global Oscillation Network Group data reveal that the internal
structure of the sun can be well represented by a calibrated standard
model. However, immediately beneath the convection zone and at the
edge of the energy-generating core, the sound-speed variation is
somewhat smoother in the sun than it is in the model. This could be a
consequence of chemical inhomogeneity that is too severe in the model,
perhaps owing to inaccurate modeling of gravitational settling or to
neglected macroscopic motion that may be present in the sun. Accurate
knowledge of the sun's structure enables inferences to be made about
the physics that controls the sun; for example, through the opacity,
the equation of state, or wave motion. Those inferences can then be
used elsewhere in astrophysics.
Title: GONG Data: Implications for the Sun's Interior and Near
Surface Magnetic Field
Authors: Goode, P. R.; Dziembowski, W. A.; Rhodes, E. J., Jr.; Tomczyk,
S.; Schou, J.; GONG Magnetic Effects Team
Bibcode: 1996AAS...188.5307G
Altcode: 1996BAAS...28..904G
The solar oscillation spectrum and the fine structure in it from the
first complete month of GONG data have been used to place a limit
on the Sun's internal magnetic field. The limit is consistent with
the magnetic pressure being no more than 1/1000 of the gas pressure
between the Sun's deep interior and its surface. This conclusion is
consistent with earlier results. The GONG data are from a time near
magnetic activity minimum. The effect of the near surface magnetic
field on the fine structure in the oscillation spectrum reflects
a perturbation of quadrupole toroidal symmetry. This geometry also
dominated at the last activity minimum. The meaning of this result is
discussed. The near surface magnetic perturbation is not spherically
symmetric. This corrupts the results of inversions designed to probe
the Sun's deep interior. The solution to this problem is presented.
Title: Can we measure the rotation rate inside stars ?
Authors: Goupil, M. -J.; Dziembowski, W. A.; Goode, P. R.; Michel, E.
Bibcode: 1996A&A...305..487G
Altcode:
We examine the possibility of obtaining localized information on the
rotation rate inside stars through asteroseismic observations from
space. Attention is focused on δ Scuti stars where both opacity-driven
and solar-like turbulence-driven modes may be detected. Plausible sets
of modes with attendant rotational splitting data are deduced from
the results of linear stability calculations, effects of amplitude
averaging for modes with higher l's, and information gathered from
ground-based photometry. For such sets of modes, optimally localized
averaging kernels are constructed, and we show that fairly detailed
information about the behavior of the rotation rate can be obtained only
if opacity-driven modes like those anticipated are indeed detected. The
turbulence-driven modes are essentially irrelevant for probing rotation.
Title: Dark Lanes in Granulation and the Excitation of Solar
Oscillations
Authors: Rimmele, T. R.; Goode, P. R.; Strous, L. H.; Stebbins, R. T.
Bibcode: 1995ESASP.376b.329R
Altcode: 1995help.confP.329R; 1995soho....2..329R
No abstract at ADS
Title: Dark Lanes in Granulation and the Excitation of Solar
Oscillations
Authors: Rimmele, Thomas R.; Goode, Philip R.; Harold, Elliotte;
Stebbins, Robin T.
Bibcode: 1995ApJ...444L.119R
Altcode:
We made simultaneous, high-resolution observations of the Sun's
granulation and solar acoustic events in the photosphere. We find that
the acoustic events, which are a local by-product of the excitation
of solar oscillations (Goode, Gough, & Kosovichev 1992), occur
preferentially in the dark, intergranular lanes. At the site of
a typical acoustic event the local granulation becomes darker over
several minutes leading up to the event with a further, abrupt darkening
immediately preceding the peak of the event. Further, the stronger
the acoustic event the darker the granulation. Thus, the excitation of
solar oscillations seems more closely associated with the rapid cooling
occurring in the upper convection layer, rather than the overshooting of
turbulent convection itself. We find no substantial role for so-called
'exploding' granules in the excitation of solar oscillations.
Title: Updated Seismic Solar Model
Authors: Dziembowski, W. A.; Goode, Philip R.; Pamyatnykh, A. A.;
Sienkiewicz, R.
Bibcode: 1995ApJ...445..509D
Altcode:
Recently released low-l solar oscillation data from the BISON network
are combined with BBSO data to obtain an updated solar seismic model
of the Sun's interior. For the core, the solar seismic model from the
new data is more consistent with the current standard solar models
than our earlier seismic model. An astrophysical solution to the solar
neutrino problem fades away.
Title: Photospheric Wave Behavior
Authors: Stebbins, R. T.; Rimmele, T. R.; Goode, P. R.
Bibcode: 1995ASPC...76..354S
Altcode: 1995gong.conf..354S
No abstract at ADS
Title: Seismic Solar Model
Authors: Dziembowski, W. A.; Goode, P. R.; Pamyatnykh, A. A.;
Sienkiewicz, R.
Bibcode: 1995ASPC...76..124D
Altcode: 1995gong.conf..124D
No abstract at ADS
Title: Internal Structure and Rotation of the Sun
Authors: Goode, P. R.
Bibcode: 1995ESASP.376a.121G
Altcode: 1995soho....1..121G; 1995heli.conf..121G
Knowledge of the Sun's internal structure and rotation has
continuously improved. Driving this has been successive measurements
of more oscillation frequencies and splittings with ever-increasing
accuracy. This, in turn, has spurred improvements in solar models. After
reviewing current knowledge of the Sun's internal structure and
rotation, the author explores the new information anticipated from
the SOHO and GONG data.
Title: Seismic solar mode
Authors: Goode, P.
Bibcode: 1995HiA....10..326G
Altcode:
No abstract at ADS
Title: A Seismic Model of the Sun's Interior
Authors: Dziembowski, W. A.; Goode, Philip R.; Pamyatnykh, A. A.;
Sienkiewicz, R.
Bibcode: 1994ApJ...432..417D
Altcode:
We advance the method of frequency inversion revealing a more
accurate seismic sounding of the solar core. We show that with the
quoted observational errors, it is possible to achieve a precision of
approximately 10-3 in the sound speed determination through
most of the sun's interior. Only for r less than 0.05 solar radius is
the precision approximately 10-2. The accuracy of the density
and pressure determinations is only slightly worse. Such restrictions
impose significant constraints on the microscopic physical data, i.e.,
opacities, nuclear-reaction cross sections, and diffusion coefficients,
as well as on the solar age. The helioseimic age is consistent with
that from meteorites. The currently available data for low-degree
p-mode frequencies exhibit a scatter that is larger than the quoted
errors, and therefore the actual precision of seismic inferences is
less than what we report, especially for the solar core. We invert
p-mode data to obtain a solar seismic model. Comparisons of the solar
seismic model with current theoretical models shows a need for some
refinements within the framework of the standard solar model. Only
in the innermost part of the core (r less than 0.05 solar radius)
do we see a feature in the seismic sound speed that cannot easily be
accounted for by refinements of the model. But the reality of the
feature is by no means certain. We find no evidence supporting an
astrophysical solution to the solar neutrino problem.
Title: Internal Rotation of the Sun
Authors: Duvall, T. L., Jr.; Dziembowski, W.; Goode, P. R.; Gough,
D. O.; Harvey, J. W.; Leibacher, J. W.
Bibcode: 1994snft.book..414D
Altcode:
No abstract at ADS
Title: Observation of impulsive acoustic events and the excitation
of solar oscillations
Authors: Goode, Philip R.
Bibcode: 1993njit.rept.....G
Altcode:
A new set of observations has been made of the intensity and Doppler
shift in the 543.4 nm Fe I line consisting of 356 spatial points in a
row 1024 arc seconds long. For these observations, new data acquisition
software and new data reduction routines were developed. Wave number
versus frequency diagrams have been obtained at several altitudes
in the photosphere. It has been shown that the changes in the sun's
internal rotation over the sun's activity cycle occurs just above the
base of the convection zone. A seismic method has been developed to
directly determine the sun's internal angular momentum, and seismic
limits have been placed on the sun's internal magnetic field.
Title: Observation of Impulsive Acoustic Events and the Excitation
of Solar Oscillations
Authors: Restaino, Sergio R.; Stebbins, Robin T.; Goode, Philip R.
Bibcode: 1993ApJ...408L..57R
Altcode:
The 5 minute solar oscillation has been exploited in numerous seismic
studies in which internal properties of the sun have been inferred. It
is generally regarded that these modes are excited by turbulent
convection in the sun's outermost layers. We observe the oscillatory
wakes caused by impulsive events, related to those described in 1909
by Lamb. These correspond to the events modeled by Goode et al. (1992)
which they associate with excitation of the global 5-min oscillations.
Title: The Sun's Rotation Near the Interface Between its Convective
and Radiative Zones: 1986-1990
Authors: Goode, P. R.
Bibcode: 1993ASPC...46..545G
Altcode: 1993IAUCo.141..545G; 1993mvfs.conf..545G
No abstract at ADS
Title: The Sun's Internal Angular Momentum from Seismology
Authors: Dziembowski, W. A.; Goode, P. R.
Bibcode: 1993ASPC...42..225D
Altcode: 1993gong.conf..225D
No abstract at ADS
Title: The Sun's Internal Rotation during and after the 1986 Activity
Minimum
Authors: Goode, P. R.; Dziembowski, W. A.
Bibcode: 1993ASPC...42..217G
Altcode: 1993gong.conf..217G
No abstract at ADS
Title: Seismic Limits on the Sun's Internal Toroidal Field
Authors: Goode, P. R.; Dziembowski, W. A.
Bibcode: 1993ASPC...42..229G
Altcode: 1993gong.conf..229G
No abstract at ADS
Title: Observation of impulsive acoustic events and the excitation
of solar oscillations
Authors: Restaino, Sergio R.; Stebbins, Robin T.; Goode, Philip R.
Bibcode: 1992njit.rept.....R
Altcode:
The five-minute solar oscillation has been exploited in numerous seismic
studies in which internal properties of the Sun have been inferred. It
is generally regarded that these modes are excited by turbulent
convection in the Sun's outermost layers. The oscillatory wakes caused
by impulsive events were observed, matching those described by Lamb
(1909). These correspond to the events modeled by Goode, et al., which
they associate with excitation of the global five-minute oscillations.
Title: The Effect of an Inclined Magnetic Field on Solar Oscillation
Frequencies
Authors: Goode, Philip R.; Thompson, Michael J.
Bibcode: 1992ApJ...395..307G
Altcode:
The radiative interior of the sun could be hiding a large-scale magnetic
field, which might not be axisymmetric about the observed rotation
axis. Using helioseismic data, we estimate that the strength of any such
relic field must be less than about 30 MG, if the field is axisymmetric
about the rotation axis. The shape oblateness caused by a field at
this limiting strength is about 5-10 x 10 exp -6. Stronger fields can
be accommodated by the helioseismic data if they are inclined to the
rotation axis. We further conclude that the convention zone and at
least the outer part of the radiative interior rotate on the same axis.
Title: Effects of Differential Rotation on Stellar Oscillations:
A Second-Order Theory
Authors: Dziembowski, W. A.; Goode, Philip R.
Bibcode: 1992ApJ...394..670D
Altcode:
A complete formalism, valid through second order in differential
rotation, is developed and applied to calculate the frequencies of
stellar oscillations. The derivation is improved and the asymptotic
formulas for g-mode splittings are generalized. In application to
solar oscillations, it is found that the second-order effects are
dominated by distortion for l less than 500. Further, these effects
are sufficiently large that they must be accounted for in any effort to
seismically determine the sun's internal magnetic field. In the solar
oscillation spectrum, accidental degeneracies happen but cannot lead
to large frequency shifts. For evolved delta Scuti stars, calculated
spectra are dense, and, under the perturbing effect of rotation, members
of neighboring multiplets may overlap. The seismic potential of modes
of mixed p-mode and g-mode character is emphasized for these stars.
Title: Movies of Velocity and Acoustic Flux in the Solar Photosphere
Authors: Stebbins, R. T.; Restaino, S. R.; Goode, P. R.
Bibcode: 1992AAS...180.0605S
Altcode: 1992BAAS...24..737S
CCD images of FeI 5434 Angstroms line profiles have previously
been collected and analyzed for the average characteristics of wave
propagation in the photosphere. The previous analysis determined the
velocity at nine depths in the spectral line and 100 horizontal spatial
points spanning 70 arc sec. Time series of these velocity frames,
lasting 37 minutes, have been Fourier transformed and filtered to
pass the five minute modes of the Sun. Through the Hilbert transform
and the analytic signal, the instantaneous velocity amplitude and
phase were computed at every point in the three dimensional space
of altitude, horizontal slit position and time. These data have been
further processed to create color-contour maps of vertical acoustic
propagation at each time sample. Velocity amplitude, velocity phase,
kinetic energy density and acoustic flux are all mapped. Time series of
these maps have been assembled into a movie which shows the evolution of
vertical acoustic propagation. This movie is a complete visualization
of sound waves in the photosphere, based on observation. The amplitude
and kinetic energy density behaves as one might expect in the presence
of the solar p-modes. However, the phase and acoustic flux have
characteristic spatial and temporal scales which are very different
from the amplitude. For example, upward and downward flux may occur
in the same amplitude structure at different times, or at the same
time. These results are consistent with the localized model of p-mode
excitation advanced by Goode, Gough and Kosovichev.
Title: Localized Excitation of Solar Oscillations
Authors: Goode, Philip R.; Gough, Douglas; Kosovichev, Aleksandr G.
Bibcode: 1992ApJ...387..707G
Altcode:
Solar oscillation data are well described in terms of waves produced
by isolated expansive events occurring less than 200 km below the base
of the photosphere. The events last about 5 minutes.
Title: Rotation of the Sun's Core
Authors: Goode, Philip R.; Frohlich, Claus; Toutain, Thierry
Bibcode: 1992ASPC...27..282G
Altcode: 1992socy.work..282G
No abstract at ADS
Title: Does the Sun Rotate on a Single Axis?
Authors: Goode, Philip R.; Thompson, Michael J.
Bibcode: 1992ASPC...27..182G
Altcode: 1992socy.work..182G
No abstract at ADS
Title: Understanding the source of the solar activity cycle: Results
and prospects from helioseismology
Authors: Goode, Philip R.
Bibcode: 1992AIPC..267...85G
Altcode: 1992ecsa.work...85G
Helioseismic studies have revealed that the only sharp change in
the Sun's internal rotation occurs near the interface between the
convective zone and the radiative interior. This region is generally
regarded as the source of the solar activity cycle. Other helioseismic
clues to the properties of the interface concern the magnetic field
and the temporal stability of rotation there.
Title: Solar activity cycle
Authors: Goode, Philip
Bibcode: 1991njit.rept.....G
Altcode:
Work focused on describing the solar activity cycle's clock as
a torsional oscillator, and describing the origin of the 5 minute
oscillations, which are used as a seismic probe. It has been discovered
that the sun's rotation does not vary near the base of the convection
zone but may vary deeper down. The full equations for the torsional
oscillator have been developed and have been solved for certain
situations. It has been shown that the 5 minute oscillations are
driven by granular size explosive events. In observational work,
the observing set-up has been designed to capture the whole solar
disk. Data is now able to be collected in a production mode. Data
reduction programs also are in full operation. The basic behavior of
5 minute oscillations has been clearly seen. A search is underway for
the global organization of convection to determine if giant cells exist.
Title: Seismology for the Fine Structure in the Sun's Oscillations
Varying with Its Activity Cycle
Authors: Dziembowski, W. A.; Goode, Philip R.
Bibcode: 1991ApJ...376..782D
Altcode:
The symmetric part of the fine structure in the 1986 and 1988 solar
oscillation data of Libbrecht and Woodard (1990) is inverted to find
statistically significant evidence for a steady megagauss toroidal
field at the bottom of the convective envelope. The sizable amplitude
of a cycle-dependent near-surface perturbations, which is argued to
have its origin in the fibril field, is confirmed.
Title: What We Know about the Sun's Internal Rotation from Solar
Oscillations
Authors: Goode, Philip R.; Dziembowski, W. A.; Korzennik, S. G.;
Rhodes, E. J., Jr.
Bibcode: 1991ApJ...367..649G
Altcode:
In this paper, a uniform approach of inversion was used to determine
the internal rotation rate of the sun from each of the six available
sets of solar oscillation data, which included the data of Duvall et
al. (1986), Rhodes et al. (1987, 1990), Tomczyk (1988), Brown and Morrow
(1987), and Libbrecht (1989). The technique chosen for inverting the
solar oscillation data was the discretized least-squares technique. The
results indicate that the rotation rate of the sun in the equatorial
plane declines going inward between the surface and 0.6 of the radius
and that the polar rate increases going inward (i.e., the surfacelike
differential rotation decreases with depth).
Title: The Sun's Internal Differential Rotation from Helioseismology
Authors: Goode, P. R.
Bibcode: 1991LNP...380..157G
Altcode: 1991IAUCo.130..157G; 1991sacs.coll..157G; 1991LNP...380..155G
Well-confirmed helioseismic data from several groups using various
observational techniques at different sites have allowed us to determine
the differential rotation in the outer half of the Sun's interior. The
resulting rotation law is simple — the surface differential rotation
persists through much of the convection zone with a transition toward
solid body rotation beneath. To date there is no appealing evidence
for a rapidly rotating core. There is however, weak evidence for a
solar cycle dependence of the Sun's internal rotation.
Title: Solar-cycle dependence of the Sun's deep internal rotation
shown by helioseismology
Authors: Goode, Philip R.; Dziembowski, W. A.
Bibcode: 1991Natur.349..223G
Altcode:
HELIOSEISMOLOGY, the study of solar oscillations, yields information on
the Sun's internal rotation and magnetism which is of great importance
in understanding the 22-year solar cycle. We show here that helioseismic
data suggest that the Sun's internal rotation rate, at depths greater
than half the solar radius, has changed systematically during the most
recent cycle. There is no variation, however, in the rotation over
a range of intermediate solar radii covering the upper part of the
Sun's radiative interior and the lower part of the convective zone;
this intermediate region is where, according to the same helioseismic
data, an abrupt change in rotation rate with depth accompanies the
transition from convective to radiative structure. We suggest that the
modulation of the rotation rate in the Sun's interior could be caused
by a torsional oscillation, provided that a poloidal magnetic field
of kilogauss strength exists in the radiative interior.
Title: The internal rotation and magnetism of the Sun from its
oscillations.
Authors: Dziembowski, W. A.; Goode, Philip R.
Bibcode: 1991sia..book..501D
Altcode:
The study of solar oscillations has revealed knowledge of the internal
rotation of the Sun and something of its internal magnetic field. The
authors present the formalism needed to determine the internal rotation
from oscillation data. Equations are developed that describe centrifugal
distortion and results are given. They sketch the formalism required
to treat poloidal and toroidal magnetic fields inside the Sun. Results
are presented for a toroidal field concentrated near the base of the
convection zone and for assumed relic poloidal and toroidal fields in
the deep interior.
Title: A frequency analysis with 20-350 pHz accuracy of five years
of observations of the non-linear dipole oscillation in the rapidly
oscillating AP star HR 3831.
Authors: Kurtz, D. W.; Shibahashi, H.; Goode, P. R.
Bibcode: 1990MNRAS.247..558K
Altcode:
We have carried out 60 hr of high-speed photometric observations of
HR 3831 in 1986. The combination of these observations with the 135
hr of observations obtained in 1980/1981 and 43 hr of observations
obtained in 1985, for which the total time-span is 1937 d, allows
us to analyse the frequencies of the rapid oscillations of HR
3831 without alias ambiguities. We determine seven frequencies
(υ1-υ7) with 20-350 pHz accuracy. By examining
the relationship between the phase of the, oscillation and the
rotation phase, we confirm that the principal oscillation of HR 3831
is mainly due to a long-lived dipole eigenmode whose symmetry axis
is the magnetic axis which is oblique to the rotation axis of the
star. The basic pattern of the pulsation phase versus rotation phase
diagram has remained constant over the five years of observations. An
unexplained inequality of the phases, θ(υ2) ≠
θ(υ1,υ1, υ3), indicates that the
dipole mode is not purely a normal mode. We confirm that the three
first-harmonic frequencies observed in HR 3831 are exactly twice the
lowest three frequencies. We show that the high-frequency triplet is
not a quadrupole normal mode (l=2) induced by non-linear coupling to
the principal dipole mode (l=1); we also show that it is not simply
caused by the second-order term of a non-linear dipole mode. The
other newly determined frequency (υ7) is separated by the
rotation frequency from the second harmonic of the eigenfrequency of
dipole mode. We examine the possibility that υ7 may be
one component of the second harmonic of the principal dipole mode.
Title: Consistency in Trends in Helioseismic Data and Photospheric
Temperature Data through the Solar Cycle
Authors: Goode, Philip R.; Kuhn, J. R.
Bibcode: 1990ApJ...356..310G
Altcode:
Inversion confirms the apparent correlation between trends in the
helioseismic data and the photospheric temperature data. Although the
helioseismic data are noisy, the radial dependence in the results
appear to support a model of a cold or hot thermal shadow arising
from, perhaps, the dynamo magnetic field seated near the base of the
convection zone.
Title: Magnetic Field in the Sun's Interior from Oscillation Data
Authors: Dziembowski, Wojciek A.; Goode, P. R.
Bibcode: 1990ASSL..159..341D
Altcode: 1990insu.conf..341D; 1990IAUCo.121..341D
No abstract at ADS
Title: Has the sun's internal rotation changed through this activity
cycle ?
Authors: Goode, P. R.; Dziembowski, W. A.; Rhodes, E. J., Jr.;
Korzennik, S.
Bibcode: 1990LNP...367..349G
Altcode: 1990psss.conf..349G
The internal rotation of the Sun is determined from each of the
six available sets of solar oscillation splitting data. These data
span this activity cycle and best sample the region near the base of
the convection zone. Going inwards through the convection zone into
the outer radiative interior, the robust results are a decrease in
the rotation rate in the equatorial plane and a trend away from the
surface-like differential rotation toward solid body rotation. In
the equatorial plane of the radiative interior, the rotation rate
seems to systematically increase through the solar cycle. If true,
this suggests that the interior has a role in the activity cycle.
Title: The Toroidal Magnetic Field inside the Sun
Authors: Dziembowski, W. A.; Goode, Philip R.
Bibcode: 1989ApJ...347..540D
Altcode:
The seismology is developed which is needed to determine the internal
toroidal magnetic field of the sun from its oscillations. Applying
this seismology to the oscillation data of Libbrecht (1989). Evidence
was found for an axisymmetric quadrupole toroidal field of 2 + or -
1 MG centered near the base of the convection zone. This field has the
symmetry and location expected for the field fed by the solar dynamo
at its seat.
Title: Inferring the Sun's Internal Angular Velocity from Observed
p-Mode Frequency Splittings
Authors: Brown, Timothy M.; Christensen-Dalsgaard, Jorgen; Dziembowski,
Wojciech A.; Goode, Philip; Gough, Douglas O.; Morrow, Cherilynn A.
Bibcode: 1989ApJ...343..526B
Altcode:
The sun's internal solar velocity Omega is studied as a function of
latitude and radius using the solar oscillation data of Brown and
Morrow (1987). An attempt is made to separate robust inferences about
the sun from artifacts of the analysis. It is found that a latitudinal
variation of Omega similar to that observed at the solar surface exists
throughout the sun's convection zone and that the variation of Omega
with latitude persists to some extent even beneath the convection zone.
Title: The Radial Gradient in the Sun's Rotation
Authors: Dziembowski, W. A.; Goode, Philip R.; Libbrecht, K. G.
Bibcode: 1989ApJ...337L..53D
Altcode:
The solar oscillation data of Libbrecht (1989) are inverted, and it
is found that there is a sharp radial gradient in the sun's rotation
at the base of the convection zone. The existence of a sharp radial
gradient there may be used to suggest that it is the site of the dynamo
which drives the sunspot cycle.
Title: On the Expansion of the Rotational Eigenfrequencies in
Legendre Polynomials
Authors: Durney, Bernard R.; Hill, Frank; Goode, Philip R.
Bibcode: 1988ApJ...326..486D
Altcode:
In the context of helioseismology, it has become customary to fit
data using Δv(n, l, m) ≡ v(n, l, m) - v(n, l) = L ΣN
i=0 ai Pi(-m/L) (Duvall, Harvey,
and Pomerantz) where v is the frequency of the nth p-mode averaged
over m, the Pi are Legendre polynomials and L = [(l +
1)l]1/2. It is shown here that, instead, it is advantageous
to use the following expansion for v(n, l, m) - v(n, l): v(n, l, m) -
v(n, l) = m Σ N i=0 bi Pi
(m/L). In this case the bi's are simply related to the
coefficients which determine the angular velocity, leading to the
expectation that we can more accurately determine the internal rotation
of the Sun from the extant helioseismological data.
Title: The Magnetic Field Inside the Sun
Authors: Dziembowski, W.; Goode, P. R.
Bibcode: 1988IAUS..123..171D
Altcode:
Duvall, Harvey and Pomerantz (1986) reported the existence of a
"structural asymmetry" inside the Sun. The authors show here that
this asymmetry is not a consequence of the Sun's rotation. They
attribute the asymmetry, rather, to a toroidal magnetic field inside
the Sun. Consistency requires a field of about one megagauss located in
the lower part of the convection zone. Accounting for such a field would
wreak havoc on our understanding of the solar dynamo and convection.
Title: Waves in the Solar Photosphere
Authors: Stebbins, Robin; Goode, Philip R.
Bibcode: 1987SoPh..110..237S
Altcode:
Time-sequences of line profile data have been subjected to a unique
analysis which produces an amplitude and phase of the velocity and
intensity at several line depths for each time sample and spatial
point on the Sun. The data have been filtered to pass only the
frequencies and spatial wavenumbers of the 5-min band. Yet, a secondary
oscillation emerges, the phase of which propagates downward. Empirical
eigenfunctions for velocity and intensity are given, and the kinetic
energy flux is computed.
Title: The dynamical quadrupole moment of the sun.
Authors: Goode, P. R.
Bibcode: 1986mgm..conf.1573G
Altcode:
The unitless, dynamical quadrupole moment of the sun is
(1.7±0.4)×10-7, as determined from solar oscillation
data. This value is ten times too small to have an impact on the
agreement between the measured anomalous advance of the perihelion
of Mercury and that predicted by general relativity. The origin of
this result is reviewed and compared with that of an earlier, less
reliable determination.
Title: The internal rotation of the Sun.
Authors: Goode, Philip R.
Bibcode: 1986ASIC..169..237G
Altcode: 1986ssds.proc..237G
The internal rotation rate of the Sun has been calculated by Duvall,
et al. from the solar oscillation data of Duvall and Harvey. The origin
and implications of this result are reviewed and compared with those
of an earlier, less reliable determination.
Title: Asteroseismology for certain Ap stars.
Authors: Dziembowski, W.; Goode, Philip R.
Bibcode: 1986ASIC..169..441D
Altcode: 1986ssds.proc..441D
The discovery by Kurtz of phase coherent, rapid oscillations in certain
Ap stars holds great promise for the new field of asteroseismology. The
authors discuss a generalized oblique pulsator model for these stars
which allows to compare the effects of rotation and magnetism. A central
role for mode coupling and amplitude limitation in the observed period
doubling is suggested.
Title: Frequency splitting in AP stars
Authors: Dziembowski, W.; Goode, P. R.
Bibcode: 1985ApJ...296L..27D
Altcode:
The oblique pulsator model by Kurtz was generalized to account for the
observed properties of rapidly oscillating Ap stars. In this model,
which includes advection and an oblique magnetic field, the modes are
represented, in general, by a superposition of all spherical harmonics
having the appropriate degree, l. It is predicted that an observer
will report a mode splitting into (2l + 1)-frequency components
with the spacing equal to the rotation frequency of the star. The
relative amplitudes at these frequencies are predicted following from
a postulated selective excitation mechanism due to the field, and the
diagnostic potential of the data on these Ap stars is discussed.
Title: Fine structure of solar acoustic oscillations due to rotation.
Authors: Goode, P. R.; Dziembowski, W.
Bibcode: 1984sses.nasa..351G
Altcode: 1984sss..conf..351G
The nature of the fine structure of high order, low degree five minute
period solar oscillations following from various postulated forms of
spherical rotation is predicted. The first and second order effects
of rotation are included.
Title: Internal rotation of the Sun
Authors: Duvall, T. L., Jr.; Dziembowski, W. A.; Goode, P. R.; Gough,
D. O.; Harvey, J. W.; Leibacher, J. W.
Bibcode: 1984Natur.310...22D
Altcode:
The frequency difference between prograde and retrograde sectoral
solar oscillations is analysed to determine the rotation rate of
the solar interior, assuming no latitudinal dependence. Much of the
solar interior rotates slightly less rapidly than the surface, while
the innermost part apparently rotates more rapidly. The resulting
solar gravitational quadrupole moment is J2 = (1.7+/-0.4)
× 10-7 and provides a negligible contribution to current
planetary tests of Einstein's theory of general relativity.
Title: Simple asymptotic estimates of the fine structure in the
spectrum of solar oscillations due to rotation and magnetism
Authors: Dziembowski, W.; Goode, P. R.
Bibcode: 1984MmSAI..55..185D
Altcode:
Simple asymptotic formulae are presented and used to predict the effect
of rotation and magnetism on the fine structure in the spectrum of
solar oscillations. The authors compare the linear effect of rotation
on the fine structure to the quadratic effect of rotation. The
asymptotic formulae for the magnetically induced fine structure are
used to schematically determine the requisite field size to cause an
observable change in the structure and the nature of the change.
Title: Limits on the Sun's core magnetism from solar oscillations
Authors: Dziembowski, W.; Goode, P. R.
Bibcode: 1983Natur.305...39D
Altcode:
Many years ago Cowling1 discussed the possibility that
the Sun has a significant relic field. This field would have poloidal
and toroidal components, with the toroidal component being driven by
dynamo action on the poloidal component. The toroidal field would be
quadrupole in nature having opposite senses in the upper and lower
hemispheres. Subsequently, Dicke2 proposed that the solar
quadrupole moment is caused by a strong, inclined toroidal field with
a magnitude of ~6×107 G. Ulrich and Rhodes3
suggested that a poloidal field with a magnitude of 3 × 108
G was required to account for some of the properties of the 5-min period
oscillation. Whereas Mestel and Moss4 claimed that such
fields may not be sufficiently stable to endure. Hill et al.5
argued that solar oscillation data imply that a simple poloidal field
is much weaker than 3 × 108 G and Gough6 has
suggested that the toroidal field may be much weaker than the 6 ×
107 G postulated by Dicke2. Magnetic fields,
like rotation, produce a fine structure in solar oscillations. Their
effects should be detectable provided the fields are sufficiently
intense. Here we perform an analysis of oscillation data due to Hill et
al.5 to show that limits of a few megagauss can be placed
on poloidal and toroidal magnetic fields inside the Sun. A limit can
thereby also be placed on the part of the quadrupole moment of the Sun
due to magnetism. These fields are too weak to induce a quadrupole
moment much larger than that which would result if the Sun rotated
rigidly at the observed surface equatorial rate.
Title: Observation of five-minute-period gravity waves in the solar
photosphere
Authors: Stebbins, R. T.; Goode, Philip R.; Hill, Henry A.
Bibcode: 1983SoPh...82..163S
Altcode: 1983IAUCo..66..163S
Vertically propagating traveling waves have been observed in the
solar photosphere. These waves have a period of 278 ± 41 seconds
and a vertical phase velocity of about 2 km s-1. It is
noted that these waves also have approximately the same period as the
well-studied five-minute-period acoustic mode, which is evanescent in
the photosphere. The only consistent interpretation of the traveling
waves implies that they are gravity waves. About half the time the
gravity waves are outgoing, while the remainder of the time they
are ingoing.
Title: Preliminary Determination of the Sun's Gravitational Quadrupole
Moment from Rotational Splitting of Global Oscillations and its
Relevance to Tests of General Relativity
Authors: Hill, Henry A.; Bos, Randall J.; Goode, Philip R.
Bibcode: 1982PhRvL..49.1794H
Altcode:
The sun's internal angular velocity is estimated from observations
of rotational splitting of low-order, low-degree global oscillations
detected as fluctuations in the limb-darkening function. The inferred
rapid rotation implies a unitless grativational quadrupole moment,
J2, of (5.5+/-1.3)×10-6. When this result
is combined with two published planetary radar results, values of
0.987+/-0.006 and 0.991+/-0.006 are obtained for 13(2+2γ-β), a
quantity equal to 1 in the general theory of relativity.
Title: Observation of nonacoustic, 5 minute period, vertical traveling
waves in the photosphere of the sun
Authors: Hill, H. A.; Goode, P. R.; Stebbins, R. T.
Bibcode: 1982ApJ...256L..17H
Altcode:
Nonacoustic, radially propagating traveling waves have been observed in
the solar photosphere. These traveling waves have a period of 278 + or -
41 s. The vertical wavelength (approximately 500 km) and phase velocity
(approximately 2 km/s) of the waves are among their properties deduced
from the data. It is also observed that the waves have outgoing phase
part of the time and ingoing phase the remainder of the time. The
traveling waves are interpreted to be gravity waves. Their role in
the heating of the chromosphere is discussed.
Title: Solar pulsations and long-term solar variability
Authors: Goode, P. R.; Logan, J. D.; Hill, H. A.
Bibcode: 1981NASCP2191..229G
Altcode: 1981vsc..conf..229G
The seismology of the solar atmosphere is important in relating changes
in luminosity to variations in other observables. This approach
has already led to the identification of properties which were not
previously observed or recognized. Equally important results from
solar seismology are expected in the future.
Title: Observation of Photospheric Gravity Waves
Authors: Stebbins, R. T.; Goode, P. R.; Hill, H. A.
Bibcode: 1981BAAS...13..858S
Altcode:
No abstract at ADS