1,030 research outputs found
Quantum number dimensional scaling analysis for excited states of multielectron atoms
A new dimensional scaling method for the calculation of excited states of
multielectron atoms is introduced. By including the principle and orbital
quantum numbers in the dimension parameter, we obtain an energy expression for
excited states including high angular momentum states. The method is tested on
He, Li, and Be. We obtain good agreement with more orthodox quantum mechanical
treatments even in the zeroth order.Comment: Submitted to Physical Review A, 13 pages, 6 Table
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
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&
Three-dimensional numerical simulation of magnetohydrodynamic-gravity waves and vortices in the solar atmosphere
With the adaptation of the FLASH code we simulate magnetohydrodynamic-gravity
waves and vortices as well as their response in the magnetized
three-dimensional (3D) solar atmosphere at different heights to understand the
localized energy transport processes. In the solar atmosphere strongly
structured by gravitational and magnetic forces, we launch a localized velocity
pulse (in horizontal and vertical components) within a bottom layer of 3D solar
atmosphere modelled by initial VAL-IIIC conditions, which triggers waves and
vortices. The rotation direction of vortices depends on the orientation of an
initial perturbation. The vertical driver generates magnetoacoustic-gravity
waves which result in oscillations of the transition region, and it leads to
the eddies with their symmetry axis oriented vertically. The horizontal pulse
excites all magnetohydrodynamic-gravity waves and horizontally oriented eddies.
These waves propagate upwards, penetrate the transition region, and enter the
solar corona. In the high-beta plasma regions the magnetic field lines move
with the plasma and the temporal evolution show that they swirl with eddies. We
estimate the energy fluxes carried out by the waves in the magnetized solar
atmosphere and conclude that such wave dynamics and vortices may be significant
in transporting the energy to sufficiently balance the energy losses in the
localized corona. Moreover, the structure of the transition region highly
affects such energy transports, and causes the channelling of the propagating
waves into the inner corona.Comment: 11 Pages, 12 Figures, Accepted for the publication in MNRA
Impulsively Generated Linear and Non-linear Alfven Waves in the Coronal Funnels
We present simulation results of the impulsively generated linear and
non-linear Alfv\'en waves in the weakly curved coronal magnetic flux-tubes
(coronal funnels) and discuss their implications for the coronal heating and
solar wind acceleration. We solve numerically the time-dependent
magnetohydrodynamic (MHD) equations to obtain the temporal signatures of the
small (linear) and large-amplitude (non-linear) Alfv\'en waves in the model
atmosphere of expanding open magnetic field configuration (e.g., coronal
funnels) by considering a realistic temperature distribution. We compute the
maximum transversal velocity of both linear and non-linear Alfv\'en waves at
different heights in the coronal funnel, and study their response in the solar
corona during the time of their propagation. We infer that the pulse-driven
non-linear Alfv\'en waves may carry sufficient wave energy fluxes to heat the
coronal funnels and also to power the solar wind that originates in these
funnels. Our study of linear Alfv\'en waves show that they can contribute only
to the plasma dynamics and heating of the funnel-like magnetic flux-tubes
associated with the polar coronal holes.Comment: 16 pages of the text and 3 figure
On Thermal-Pulse-Driven Plasma Flows in Coronal Funnels as Observed by Hinode/EUV Imaging Spectrometer (EIS)
Using one-arcsecond-slit scan observations from the Hinode/EUV Imaging
Spectrometer (EIS) on 05 February 2007, we find the plasma outflows in the open
and expanding coronal funnels at the eastern boundary of AR 10940. The Doppler
velocity map of Fe XII 195.120 A shows that the diffuse close-loop system to be
mostly red-shifted. The open arches (funnels) at the eastern boundary of AR
exhibit blue-shifts with a maximum speed of about 10-15 km/s. This implies
outflowing plasma through these magnetic structures. In support of these
observations, we perform a 2D numerical simulation of the expanding coronal
funnels by solving the set of ideal MHD equations in appropriate VAL-III C
initial temperature conditions using the FLASH code. We implement a rarefied
and hotter region at the footpoint of the model funnel, which results in the
evolution of slow plasma perturbations propagating outward in the form of
plasma flows. We conclude that the heating, which may result from magnetic
reconnection, can trigger the observed plasma outflows in such coronal funnels.
This can transport mass into the higher corona, giving rise to the formation of
the nascent solar wind.Comment: 17 Pages; 7 Figure
Torsional Alfven Waves in Solar Magnetic Flux Tubes of Axial Symmetry
Aims: Propagation and energy transfer of torsional Alfv\'en waves in solar
magnetic flux tubes of axial symmetry is studied. Methods: An analytical model
of a solar magnetic flux tube of axial symmetry is developed by specifying a
magnetic flux and deriving general analytical formulae for the equilibrium mass
density and a gas pressure. The main advantage of this model is that it can be
easily adopted to any axisymmetric magnetic structure. The model is used to
simulate numerically the propagation of nonlinear Alfv\'en waves in such 2D
flux tubes of axial symmetry embedded in the solar atmosphere. The waves are
excited by a localized pulse in the azimuthal component of velocity and
launched at the top of the solar photosphere, and they propagate through the
solar chromosphere, transition region, and into the solar corona. Results: The
results of our numerical simulations reveal a complex scenario of twisted
magnetic field lines and flows associated with torsional Alfv\'en waves as well
as energy transfer to the magnetoacoustic waves that are triggered by the
Alfv\'en waves and are akin to the vertical jet flows. Alfv\'en waves
experience about 5 % amplitude reflection at the transition region. Magnetic
(velocity) field perturbations experience attenuation (growth) with height is
agreement with analytical findings. Kinetic energy of magnetoacoustic waves
consists of 25 % of the total energy of Alfv\'en waves. The energy transfer may
lead to localized mass transport in the form of vertical jets, as well as to
localized heating as slow magnetoacoustic waves are prone to dissipation in the
inner corona.Comment: 12 pages; 12 Figures, Astron. Astrophys. (A&A); Comment :
High-resolution images will be appeared with the final pape
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