8,878 research outputs found
An apparent statistical relationship between polar heat budget and zonal circulation
Apparent statistical correlation between Arctic heat budget and zonal circulatio
Detection of 3-Minute Oscillations in Full-Disk Ly Emission During A Solar Flare
In this Letter we report the detection of chromospheric 3-minute oscillations
in disk-integrated EUV irradiance observations during a solar flare. A wavelet
analysis of detrended Lyman-alpha (from GOES/EUVS) and Lyman continuum (from
SDO/EVE) emission from the 2011 February 15 X-class flare (SOL2011-02-15T01:56)
revealed a 3-minute period present during the flare's main phase. The
formation temperature of this emission locates this radiation to the flare's
chromospheric footpoints, and similar behaviour is found in the SDO/AIA
1600\AA\ and 1700\AA\ channels, which are dominated by chromospheric continuum.
The implication is that the chromosphere responds dynamically at its acoustic
cutoff frequency to an impulsive injection of energy. Since the 3-minute period
was not found at hard X-ray energies (50-100 keV) in RHESSI data we can state
that this 3-minute oscillation does not depend on the rate of energization of
non-thermal electrons. However, a second period of 120 s found in both hard
X-ray and chromospheric emission is consistent with episodic electron
energization on 2-minute timescales. Our finding on the 3-minute oscillation
suggests that chromospheric mechanical energy should be included in the flare
energy budget, and the fluctuations in the Lyman-alpha line may influence the
composition and dynamics of planetary atmospheres during periods of high
activity.Comment: 6 pages, 5 figures. Accepted for publication in Astrophysics Journal
Letter
The spectral content of SDO/AIA 1600 and 1700 \AA\ filters from flare and plage observations
The strong enhancement of the ultraviolet emission during solar flares is
usually taken as an indication of plasma heating in the lower solar atmosphere
caused by the deposition of the energy released during these events. Images
taken with broadband ultraviolet filters by the {\em Transition Region and
Coronal Explorer} (TRACE) and {\em Atmospheric Imaging Assembly} (AIA 1600 and
1700~\AA) have revealed the morphology and evolution of flare ribbons in great
detail. However, the spectral content of these images is still largely unknown.
Without the knowledge of the spectral contribution to these UV filters, the use
of these rich imaging datasets is severely limited. Aiming to solve this issue,
we estimate the spectral contributions of the AIA UV flare and plage images
using high-resolution spectra in the range 1300 to 1900~\AA\ from the Skylab
NRL SO82B spectrograph. We find that the flare excess emission in AIA 1600~\AA\
is { dominated by} the \ion{C}{4} 1550~\AA\ doublet (26\%), \ion{Si}{1}
continua (20\%), with smaller contributions from many other chromospheric lines
such as \ion{C}{1} 1561 and 1656~\AA\ multiplets, \ion{He}{2} 1640~\AA,
\ion{Si}{2} 1526 and 1533~\AA. For the AIA 1700~\AA\ band, \ion{C}{1} 1656~\AA\
multiplet is the main contributor (38\%), followed by \ion{He}{2} 1640 (17\%),
and accompanied by a multitude of other, { weaker} chromospheric lines, with
minimal contribution from the continuum. Our results can be generalized to
state that the AIA UV flare excess emission is of chromospheric origin, while
plage emission is dominated by photospheric continuum emission in both
channels.Comment: Accepted for publication in ApJ Skylab NRL SO82B data used in this
work available at http://dx.doi.org/10.5525/gla.researchdata.68
Temperature dependent anisotropy of the penetration depth and coherence length in MgB$_2
We report measurements of the temperature dependent anisotropies
( and ) of both the London penetration depth
and the upper critical field of MgB. Data for
was obtained from measurements of
and on a single crystal sample using a tunnel diode
oscillator technique. was
deduced from field dependent specific heat measurements on the same sample.
and have opposite temperature dependencies, but
close to tend to a common value (). These results are in good agreement with theories
accounting for the two gap nature of MgBComment: 4 pages with figures (New version
RC J1148+0455 identification: gravitational lens or group of galaxies ?
The structure of the radio source RC B1146+052 of the ``Cold'' catalogue is
investigated by data of the MIT-GB-VLA survey at 4850 MHz. This source belongs
to the steep spectrum radio sources subsample of the RC catalogue. Its spectral
index is = -1.04. The optical image of this source obtained with 6m
telescope is analysed. The radio source center is situated in a group of 8
galaxies of about 24 in the R-filter. The possible explanations of the
complex structure of radio components are considered.Comment: 6 pages, 5 figures, uses psfig.sty. This was the poster as presented
on Gamow Memorial Internat. Conference GMIC'99 "Early Universe: Cosmological
Problems and Instrumental Technologies" in St.Petersburg, 23-27 Aug., 1999.
Submitted to Proceedings to be published in A&A Transaction
Relations between concurrent hard X-ray sources in solar flares
Context: Solar flares release a large fraction of their energy into
non-thermal electrons, but it is not clear where and how. Bremsstrahlung X-rays
are observed from the corona and chromosphere.
Aims: We aim to characterize the acceleration process by the coronal source
and its leakage toward the footpoints in the chromosphere. The relations
between the sources reflect the geometry and constrict the configuration of the
flare.
Methods: We studied solar flares of GOES class larger than M1 with three or
more hard X-ray sources observed simultaneously in the course of the flare. The
events were observed with the X-ray satellite RHESSI from February 2002 until
July 2005. We used imaging spectroscopy methods to determine the spectral
evolution of each source in each event. The images of all of the five events
show two sources visible only at high energies (footpoints) and one source only
visible at low energies (coronal or looptop source, in two cases situated over
the limb).
Results: We find soft-hard-soft behavior in both, coronal source and
footpoints. The coronal source is nearly always softer than the footpoints. The
footpoint spectra differ significantly only in one event out of five.
Conclusions: The observations are consistent with acceleration in the coronal
source and an intricate connection between the corona and chromosphere.Comment: accepted for publication in A&A, 11 pages, 9 figure
Teaching about Arms Control
Here at the Naval War College, in struggling to tie together our sessions on arms control and negotiation, we have finally settled on a simulation exercises. This game has proved to be a powerful synthesizer, and several players in various positions within Government and civilian academia have suggested we share this tool with others. Our purpose here is to describe the game in a manner so intriguing that our readers will want to use it
Detection of brain functional-connectivity difference in post-stroke patients using group-level covariance modeling
Functional brain connectivity, as revealed through distant correlations in
the signals measured by functional Magnetic Resonance Imaging (fMRI), is a
promising source of biomarkers of brain pathologies. However, establishing and
using diagnostic markers requires probabilistic inter-subject comparisons.
Principled comparison of functional-connectivity structures is still a
challenging issue. We give a new matrix-variate probabilistic model suitable
for inter-subject comparison of functional connectivity matrices on the
manifold of Symmetric Positive Definite (SPD) matrices. We show that this model
leads to a new algorithm for principled comparison of connectivity coefficients
between pairs of regions. We apply this model to comparing separately
post-stroke patients to a group of healthy controls. We find
neurologically-relevant connection differences and show that our model is more
sensitive that the standard procedure. To the best of our knowledge, these
results are the first report of functional connectivity differences between a
single-patient and a group and thus establish an important step toward using
functional connectivity as a diagnostic tool
Output Management for Agriculture?
Could agriculture learn to manage its output from some other industries? Some industries have experience in managing excess capacity. Agriculture might want to look at the alternative methods and their consequences
Profile of Women Incarcerated For Murder in Oklahoma
The present study addresses the need to increase our understanding of women incarcerated for violent crimes, especially murder, by developing a profile of women incarcerated for murder in Oklahoma. Compared to the United States as a whole, Oklahoma has one of the highest per capita rates of female incarceration. While women represent only five percent of the total prison population in the United States, they comprise twelve percent of Oklahoma\u27s prison population (Oklahoma Department of Corrections, 1989). Survey data of female inmates in Oklahoma are utilized to study the demographic 45 - characteristics as well as the current and past personal and family background factors of women incarcerated for murder. In addition, recommendations are offered to address the specific needs of women incarcerated for Murder
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