214 research outputs found
Solar wind modeling with the Alfven Wave Solar atmosphere Model driven by HMI-based Near-Real-Time maps by the National Solar Observatory
We explore model performance for the Alfven Wave Solar atmosphere Model
(AWSoM) with near-real-time (NRT) synoptic maps of the photospheric vector
magnetic field. These maps, produced by assimilating data from the Helioseismic
Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), use a
different method developed at the National Solar Observatory (NSO) to provide a
near contemporaneous source of data to drive numerical models. Here, we apply
these NSO-HMI-NRT maps to simulate three Carrington rotations (CRs): 2107-2108
(centered on 2011/03/07 20:12 CME event), 2123 (integer CR) and 2218--2219
(centered on 2019/07/2 solar eclipse), which together cover a wide range of
activity level for solar cycle 24. We show simulation results, which reproduce
both extreme ultraviolet emission (EUV) from the low corona while
simultaneously matching in situ observations at 1 au as well as quantify the
total unsigned open magnetic flux from these maps
Nonlinear force-free and potential field models of active-region and global coronal fields during the Whole Heliospheric Interval
Between 2008/3/24 and 2008/4/2, the three active regions NOAA active regions
10987, 10988 and 10989 were observed daily by the Synoptic Optical Long-term
Investigations of the Sun (SOLIS) Vector Spectro-Magnetograph (VSM) while they
traversed the solar disk. We use these measurements and the nonlinear
force-free magnetic field code XTRAPOL to reconstruct the coronal magnetic
field for each active region and compare model field lines with images from the
Solar Terrestrial RElations Observatory (STEREO) and Hinode X-ray Telescope
(XRT) telescopes. Synoptic maps made from continuous, round-the-clock Global
Oscillations Network Group (GONG) magnetograms provide information on the
global photospheric field and potential-field source-surface models based on
these maps describe the global coronal field during the Whole Heliospheric
Interval (WHI) and its neighboring rotations. Features of the modeled global
field, such as the coronal holes and streamer belt locations, are discussed in
comparison with extreme ultra-violet and coronagraph observations from STEREO.
The global field is found to be far from a minimum, dipolar state. From the
nonlinear models we compute physical quantities for the active regions such as
the photospheric magnetic and electric current fluxes, the free magnetic energy
and the relative helicity for each region each day where observations permit.
The interconnectivity of the three regions is addressed in the context of the
potential-field source-surface model. Using local and global quantities derived
from the models, we briefly discuss the different observed activity levels of
the regions.Comment: Accepted for publication in the Solar Physics Whole Heliospheric
Interval (WHI) topical issue. We had difficulty squeezing this paper into
arXiv's 15 Mb limit. The full paper is available here
ftp://gong2.nso.edu/dsds_user/petrie/PetrieCanouAmari.pd
Modeling FETCH Observations of 2005 May 13 CME
This paper evaluates the quality of CME analysis that has been undertaken
with the rare Faraday rotation observation of an eruption. Exploring the
capability of the FETCH instrument hosted on the MOST mission, a four-satellite
Faraday rotation radio sounding instrument deployed between the Earth and the
Sun, we discuss the opportunities and challenges to improving the current
analysis approaches.Comment: 33 pages, 24 figure
NON-STATIONARY PHOTOCONDUCTIVITY OF GaN NANOCOMPOSITES IN ARTIFICIAL OPAL MATRIX
Abstract It was recently proposed to use synthetic opals as a host matrix for obtaining 3D arrays of electronic nanodevice
3D evolution of a filament disappearance event observed by STEREO
A filament disappearance event was observed on 22 May 2008 during our recent
campaign JOP 178. The filament, situated in the southern hemisphere, showed
sinistral chirality consistent with the hemispheric rule. The event was well
observed by several observatories in particular by THEMIS. One day before the
disappearance, H observations showed up and down flows in adjacent
locations along the filament, which suggest plasma motions along twisted flux
rope. THEMIS and GONG observations show shearing photospheric motions leading
to magnetic flux canceling around barbs. STEREO A, B spacecraft with separation
angle 52.4 degrees, showed quite different views of this untwisting flux rope
in He II 304 \AA\ images. Here, we reconstruct the 3D geometry of the filament
during its eruption phase using STEREO EUV He II 304 \AA\ images and find that
the filament was highly inclined to the solar normal. The He II 304 \AA\ movies
show individual threads, which oscillate and rise to an altitude of about 120
Mm with apparent velocities of about 100 km s, during the rapid
evolution phase. Finally, as the flux rope expands into the corona, the
filament disappears by becoming optically thin to undetectable levels. No CME
was detected by STEREO, only a faint CME was recorded by LASCO at the beginning
of the disappearance phase at 02:00 UT, which could be due to partial filament
eruption. Further, STEREO Fe XII 195 \AA\ images showed bright loops beneath
the filament prior to the disappearance phase, suggesting magnetic reconnection
below the flux rope
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