18,760 research outputs found
New analytical and numerical models of solar coronal loop: I. Application to forced vertical kink oscillations
Aims. We construct a new analytical model of a solar coronal loop that is
embedded in a gravitationally stratified and magnetically confined atmosphere.
On the basis of this analytical model, we devise a numerical model of solar
coronal loops. We adopt it to perform the numerical simulations of its vertical
kink oscillations excited by an external driver. Methods. Our model of the
solar atmosphere is constructed by adopting a realistic temperature
distribution and specifying the curved magnetic field lines that constitute a
coronal loop. This loop is described by 2D, ideal magnetohydro- dynamic
equations that are numerically solved by the FLASH code. Results. The vertical
kink oscillations are excited by a periodic driver in the vertical component of
velocity, acting at the top of the photosphere. For this forced driver with its
amplitude 3 km/s, the excited oscillations exhibit about 1.2 km/s amplitude in
their velocity and the loop apex oscillates with its amplitude in displacement
of about 100 km. Conclusions. The newly devised analytical model of the coronal
loops is utilized for the numerical simulations of the vertical kink
oscillations, which match well with the recent observations of decay-less kink
oscillations excited in solar loops. The model will have further implications
on the study of waves and plasma dynamics in coronal loops, revealing physics
of energy and mass transport mechanisms in the localized solar atmosphere.Comment: 6 Pages; 5 Figures; A&
On the Asymmetric Longitudinal Oscillations of a Pikelner's Model Prominence
We present analytical and numerical models of a normal-polarity quiescent
prominence that are based on the model of Pikelner (Solar Phys. 1971, 17, 44 ).
We derive the general analytical expressions for the two-dimensional
equilibrium plasma quantities such as the mass density and a gas pressure, and
we specify magnetic-field components for the prominence, which corresponds to a
dense and cold plasma residing in the dip of curved magnetic-field lines. With
the adaptation of these expressions, we solve numerically the 2D, nonlinear,
ideal MHD equations for a Pikelner's model of a prominence that is initially
perturbed by reducing the gas pressure at the dip of magnetic-field lines. Our
findings reveal that as a result of pressure perturbations the prominence
plasma starts evolving in time and this leads to the antisymmetric
magnetoacoustic--gravity oscillations as well as to the mass-density growth at
the magnetic dip, and the magnetic-field lines subside there. This growth
depends on the depth of magnetic dip. For a shallower dip, less plasma is
condensed and vice-versa. We conjecture that the observed long-period
magnetoacoustic-gravity oscillations in various prominence systems are in
general the consequence of the internal pressure perturbations of the plasma
residing in equilibrium at the prominence dip.Comment: 24 Pages; 16 Figures; Solar Physic
Particle Production at CBM in a Thermal Model Approach
The Compressed Baryonic Matter (CBM) experiment planned at Facility for
Antiproton and Ion Research (FAIR) will provide a major scientific effort for
exploring the properties of strongly interacting matter in the high baryon
density regime. One of the important goal behind such experiment is to
precisely determine the equation of state (EOS) for the strongly interacting
matter at extreme baryon density. In this paper, we have used a thermal model
EOS incorporating excluded volume description for the hot and dense hadron gas
(HG). We then predict different particle ratios and the total multiplicity of
various hadrons in the CBM energy range i.e. from A GeV to A GeV lab
energies, which corresponds to A GeV and A GeV center-of-mass
energies. Our main emphasis is to estimate the strange particles enhancement as
well as increase in the net baryon density in CBM experiment. We have also
compared our results with the results obtained from various other theoretical
approaches existing in the literature such as hadron string dynamics (HSD)
model and ultra-relativistic quantum molecular dynamics (UrQMD) etc.Comment: 16 pages, 8 figure
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