15,583 research outputs found
An analytical model of prominence dynamics
Solar prominences are magnetic structures incarcerating cool and dense gas in
an otherwise hot solar corona. Prominences can be categorized as quiescent and
active. Their origin and the presence of cool gas (~K) within the hot
(~K) solar corona remains poorly understood. The structure and dynamics
of solar prominences was investigated in a large number of observational and
theoretical (both analytical and numerical) studies. In this paper, an analytic
model of quiescent solar prominence is developed and used to demonstrate that
the prominence velocity increases exponentially, which means that some gas
falls downward towards the solar surface, and that Alfven waves are naturally
present in the solar prominences. These theoretical predictions are consistent
with the current observational data of solar quiescent prominences.Comment: Update Final Journal Print Version along with other Metadat
Seiberg-Witten map and Galilean symmetry violation in a non-commutative planar system
An effective U(1) gauge invariant theory is constructed for a non-commutative
Schrodinger field coupled to a background U(1)_{\star} gauge field in
2+1-dimensions using first order Seiberg-Witten map. We show that this
effective theory can be cast in the form of usual Schrodinger action with
interaction terms of noncommutative origin provided the gauge field is of
``background'' type with constant magnetic field. The Galilean symmetry is
investigated and a violation is found in the boost sector. We also consider the
problem of Hall conductivity in this framework.Comment: REVTeX, 4 pages, Title changed, Paper shortened, Appendix removed, A
new section on Galilean symmetry adde
Origin of gamma-ray emission in the shell of Cassiopeia A
Non-thermal X-ray emission from the shell of Cassiopeia A (Cas A) has been an
interesting subject of study, as it provides information about relativistic
electrons and their acceleration mechanisms in the shocks. Chandra X-ray
observatory revealed the detailed spectral and spatial structure of this SNR in
X-rays. The spectral analysis of Chandra X-ray data of Cas A shows unequal flux
levels for different regions of the shell, which can be attributed to different
magnetic fields in those regions. Additionally, the GeV gamma-ray emission
observed by Large Area Telescope on board Fermi Gamma Ray Space Telescope
showed that the hadronic processes are dominating in Cas A, a clear signature
of acceleration of protons. In this paper we aim to explain the GeV-TeV
gamma-ray data in the context of both leptonic and hadronic scenario. We
modeled the multi-wavelength spectrum of Cas A. We use synchrotron emission
process to explain the observed non-thermal X-ray fluxes from different regions
of the shell. These result in estimation of the model parameters, which are
then used to explain TeV gamma-ray emission spectrum. We also use hadronic
scenario to explain both GeV and TeV fluxes simultaneously. We show that a
leptonic model alone cannot explain the GeV-TeV data. Therefore, we need to
invoke a hadronic model to explain the observed GeV-TeV fluxes. We found that
although pure hadronic model is able to explain the GeV-TeV data, a
lepto-hadronic model provides the best fit to the data.Comment: Accepted in A&
Interacting spinor and scalar fields in Bianchi type-I Universe filled with viscous fluid: exact and numerical solutions
We consider a self-consistent system of spinor and scalar fields within the
framework of a Bianchi type I gravitational field filled with viscous fluid in
presence of a term. Exact self-consistent solutions to the
corresponding spinor, scalar and BI gravitational field equations are obtained
in terms of , where is the volume scale of BI universe. System of
equations for and \ve, where \ve is the energy of the viscous fluid,
is deduced. Some special cases allowing exact solutions are thoroughly studied.Comment: 18 pages, 6 figure
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