3,604 research outputs found
Drift waves in the corona: heating and acceleration of ions at frequencies far below the gyro frequency
In the solar corona, several mechanisms of the drift wave instability can
make the mode growing up to amplitudes at which particle acceleration and
stochastic heating by the drift wave take place. The stochastic heating, well
known from laboratory plasma physics where it has been confirmed in numerous
experiments, has been completely ignored in past studies of coronal heating.
However, in the present study and in our very recent works it has been shown
that the inhomogeneous coronal plasma is, in fact, a perfect environment for
fast growing drift waves. As a matter of fact, the large growth rates are
typically of the same order as the plasma frequency. The consequent heating
rates may exceed the required values for a sustained coronal heating by several
orders of magnitude. Some aspects of these phenomena are investigated here. In
particular the analysis of the particle dynamics within the growing wave is
compared with the corresponding fluid analysis. While both of them predict the
stochastic heating, the threshold for the heating obtained from the single
particle analysis is higher. The explanation for this effect is given.Comment: To appear in MNRAS (2010
New features of ion acoustic waves in inhomogeneous and permeating plasmas
It is generally accepted that the ion acoustic (IA) wave in plasmas
containing ions and electrons with the same temperature is of minor importance
due to strong damping of the wave by hot resonant ions. In this work it will be
shown that the IA wave is susceptible to excitation even in plasmas with hot
ions when both an electromagnetic transverse wave and a background density
gradient are present in the plasma, and in addition the wave is in fact
unstable (i.e., growing) in the case of permeating homogeneous plasmas. The
multi-component fluid theory is used to describe the IA wave susceptibility for
excitation in inhomogeneous plasmas and its coupling with electromagnetic
waves. The growing IA wave in permeating homogeneous plasmas is described by
the kinetic theory. In plasmas with density and temperature gradients the IA
wave is effectively coupled with the electromagnetic waves. In comparison to
ordinary IA wave in homogeneous plasma, the Landau damping of the present wave
is much smaller, and to demonstrate this effect a simple but accurate fluid
model is presented for the Landau damping. In the case of permeating plasmas, a
kinetic mechanism for the current-less IA wave instability is presented, with a
very low threshold for excitation as compared with ordinary
electron-current-driven kinetic instability. Such growing IA waves can
effectively heat plasma in the upper solar atmosphere by a stochastic heating
mechanism presented in the work. The results of this work suggest that the IA
wave role in the heating of the solar atmosphere (chromosphere and corona)
should be reexamined
Response to Comment of Shukla and Akbari-Moghanjoughi
Shukla and Akbari-Moghanjoughi have {\it corrected} their Comment (see their
version 1 on `arXiv:1207.7029v1) to EPL on our work [1] after receiving our
Response from the Editors of EPL. We have a pleasant duty at hand to present
our second Response to their second version of the Comment. It is hoped that
this response adds strength to our plea {\it for a common sense} [1] on quantum
description of plasmas.Comment: Submitted to EP
The universally growing mode in the solar atmosphere: coronal heating by drift waves
The heating of the plasma in the solar atmosphere is discussed within both
frameworks of fluid and kinetic drift wave theory. We show that the basic
ingredient necessary for the heating is the presence of density gradients in
the direction perpendicular to the magnetic field vector. Such density
gradients are a source of free energy for the excitation of drift waves. We use
only well established basic theory, verified experimentally in laboratory
plasmas. Two mechanisms of the energy exchange and heating are shown to take
place simultaneously: one due to the Landau effect in the direction parallel to
the magnetic field, and another one, stochastic heating, in the perpendicular
direction. The stochastic heating i) is due to the electrostatic nature of the
waves, ii) is more effective on ions than on electrons, iii) acts predominantly
in the perpendicular direction, iv) heats heavy ions more efficiently than
lighter ions, and v) may easily provide a drift wave heating rate that is
orders of magnitude above the value that is presently believed to be sufficient
for the coronal heating, i.e., J/(ms) for active
regions and J/(ms) for coronal holes. This heating
acts naturally through well known effects that are, however, beyond the current
standard models and theories.Comment: To appear in MNRA
Current-less solar wind driven dust acoustic instability in cometary plasma
A quantitative analysis is presented of the dust acoustic wave instability
driven by the solar and stellar winds. This is a current-less kinetic
instability which develops in permeating plasmas, i.e.., when one quasi-neutral
electron-ion wind plasma in its propagation penetrates through another
quasi-neutral plasma which contains dust, electrons and ions
Inclusive searches for squarks and gluinos with the ATLAS detector
Despite the absence of experimental evidence, weak scale supersymmetry
remains one of the best motivated and studied Standard Model extensions. This
report summarises recent ATLAS results on inclusive searches for supersymmetric
squarks and gluinos, including third generation squarks produced in the decay
of gluinos. Results are presented for both R-parity conserving and R-parity
violating scenarios, with final states containing jets with and without missing
transverse momentum, light leptons, taus or photons.Comment: Proceedings for the LHCP 2014 conferenc
Features of ion acoustic waves in collisional plasmas
The effects of friction on the ion acoustic (IA) wave in fully and partially
ionized plasmas are studied. In a quasi-neutral electron-ion plasma the
friction between the two species cancels out exactly and the wave propagates
without any damping. If the Poisson equation is used instead of the
quasi-neutrality, however, the IA wave is damped and the damping is dispersive.
In a partially ionized plasma, the collisions with the neutrals modify the IA
wave beyond recognition. For a low density of neutrals the mode is damped. Upon
increasing the neutral density, the mode becomes first evanescent and then
reappears for a still larger number of neutrals. A similar behavior is obtained
by varying the mode wave-length. The explanation for this behavior is given. In
an inhomogeneous plasma placed in an external magnetic field, and for
magnetized electrons and un-magnetized ions, the IA mode propagates in any
direction and in this case the collisions make it growing on the account of the
energy stored in the density gradient. The growth rate is angle dependent. A
comparison with the collision-less kinetic density gradient driven IA
instability is also given.Comment: The following article has been accepted by Physics of Plasmas. After
it is published, it will be found at http://pop.aip.org
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