1,576 research outputs found
Dependence of EMIC wave parameters during quiet, geomagnetic storm, and geomagnetic storm phase times
As electromagnetic ion cyclotron (EMIC) waves may play an important role in radiation belt dynamics, there has been a push to better include them into global simulations. How to best include EMIC wave effects is still an open question. Recently many studies have attempted to parameterize EMIC waves and their characteristics by geomagnetic indices. However, this does not fully take into account important physics related to the phase of a geomagnetic storm. In this paper we first consider how EMIC wave occurrence varies with the phase of a geomagnetic storm and the SYM-H, AE, and Kp indices. We show that the storm phase plays an important role in the occurrence probability of EMIC waves. The occurrence rates for a given value of a geomagnetic index change based on the geomagnetic condition. In this study we also describe the typical plasma and wave parameters observed in L and magnetic local time for quiet, storm, and storm phase. These results are given in a tabular format in the supporting information so that more accurate statistics of EMIC wave parameters can be incorporated into modeling efforts
New solutions in 3D gravity
We study gravitational theory in 1+2 spacetime dimensions which is determined
by the Lagrangian constructed as a sum of the Einstein-Hilbert term plus the
two (translational and rotational) gravitational Chern-Simons terms. When the
corresponding coupling constants vanish, we are left with the purely Einstein
theory of gravity. We obtain new exact solutions for the gravitational field
equations with the nontrivial material sources. Special attention is paid to
plane-fronted gravitational waves (in case of the Maxwell field source) and to
the circularly symmetric as well as the anisotropic cosmological solutions
which arise for the ideal fluid matter source.Comment: Revtex, 21 pages, no figure
An efficient and positivity-preserving layer method for modeling radiation belt diffusion processes
An efficient and positivity-preserving layer method is introduced to solve the radiation belt diffusion equation and is applied to study the bounce resonance interaction between relativistic electrons and magnetosonic waves. The layer method with linear interpolation, denoted by LM-L (layer method-linear), requires the use of a large number of grid points to ensure accurate solutions. We introduce a monotonicity- and positivity-preserving cubic interpolation method to be used with the Milstein-Tretyakov layer method. The resulting method, called LM-MC (layer method-monotone cubic), can be used to solve the radiation belt diffusion equation with a much smaller number of grid points than LM-L while still being able to preserve the positivity of the solution. We suggest that LM-MC can be used to study long-term dynamics of radiation belts. We then develop a 2-D LM-MC code and use it to investigate the bounce resonance diffusion of radiation belt electrons by magnetosonic waves. Using a previously published magnetosonic wave model, we demonstrate that bounce resonance with magnetosonic waves is as important as gyroresonance; both can cause several orders of magnitude increase of MeV electron fluxes within 1ᅠday. We conclude that bounce resonance with magnetosonic waves should be taken into consideration together with gyroresonance
New Charged Dilaton Solutions in 2+1 Dimensions and Solutions with Cylindrical Symmetry in 3+1 Dimensions
We report a new family of solutions to Einstein-Maxwell-dilaton gravity in
2+1 dimensions and Einstein-Maxwell gravity with cylindrical symmetry in 3+1
dimensions. A set of static charged solutions in 2+1 dimensions are obtained by
a compactification of charged solutions in 3+1 dimensions with cylindrical
symmetry. These solutions contain naked singularities for certain values of the
parameters considered. New rotating charged solutions in 2+1 dimensions and 3+1
dimensions are generated treating the static charged solutions as seed metrics
and performing transformations.Comment: Latex. No figure
Gravitational Collapse of Phantom Fluid in (2+1)-Dimensions
This investigation is devoted to the solutions of Einstein's field equations
for a circularly symmetric anisotropic fluid, with kinematic self-similarity of
the first kind, in -dimensional spacetimes. In the case where the radial
pressure vanishes, we show that there exists a solution of the equations that
represents the gravitational collapse of an anisotropic fluid, and this
collapse will eventually form a black hole, even when it is constituted by the
phantom energy.Comment: 10 page
Newtonian versus relativistic nonlinear cosmology
Both for the background world model and its linear perturbations Newtonian
cosmology coincides with the zero-pressure limits of relativistic cosmology.
However, such successes in Newtonian cosmology are not purely based on Newton's
gravity, but are rather guided ones by previously known results in Einstein's
theory. The action-at-a-distance nature of Newton's gravity requires further
verification from Einstein's theory for its use in the large-scale nonlinear
regimes. We study the domain of validity of the Newtonian cosmology by
investigating weakly nonlinear regimes in relativistic cosmology assuming a
zero-pressure and irrotational fluid. We show that, first, if we ignore the
coupling with gravitational waves the Newtonian cosmology is exactly valid even
to the second order in perturbation. Second, the pure relativistic correction
terms start appearing from the third order. Third, the correction terms are
independent of the horizon scale and are quite small in the large-scale near
the horizon. These conclusions are based on our special (and proper) choice of
variables and gauge conditions. In a complementary situation where the system
is weakly relativistic but fully nonlinear (thus, far inside the horizon) we
can employ the post-Newtonian approximation. We also show that in the
large-scale structures the post-Newtonian effects are quite small. As a
consequence, now we can rely on the Newtonian gravity in analyzing the
evolution of nonlinear large-scale structures even near the horizon volume.Comment: 8 pages, no figur
Reversible reorganization of the chlorophyll-protein complexes of photosystem II in cyanobacterium cells in the dark ag
AbstractA new emission band at 673 nm was detected in the low-temperature fluorescence spectrum of dark-adapted cyanobacteria Gloeotrichia raciborski. The excitation spectrum of this band was close to the absorbance of the isolated reaction centre of photosystem II. The relative intensities of the bands of chlorophyll and pheophytin in this spectrum showed the relative concentrations of these pigments to be about 3:1. The intensity of the band increased with darkness (half-time about 2 h). Under illumination the band rapidly disappeared (half-time about 60 s). The appearance of a 673 nm band in the dark and its disappearance in the light were accompanied by a decrease, and, respectively, an increase in the fluorescence of the PS II band at 697 nm
Circular Semiclassical String solutions on Confining AdS/CFT Backgrounds
We study multiwrapped circular string pulsating in the radial direction of
AdS black hole. We compute the energy of this string as a function of a large
quantum number n. One then could associate it with energy and a quantum number
of states in the dual finite temperature {\cal N}=4 SYM theory as well as three
dimensional pure gauge theory. We observe that the n dependence of the energy
has a universal form. We have also considered pulsating string in the
background of the near-extremal D4-brane solution. Circular pulsating membrane
in M-theory on AdS_7\times S^4 has also been studied.Comment: 14 pages, latex, v2: typos corrected, refs. adde
Lorentz-CPT violation, radiative corrections and finite temperature
In this work we investigate the radiatively induced Chern-Simons-like terms
in four-dimensions at zero and finite temperature. We use the approach of
rationalizing the fermion propagator up to the leading order in the
CPT-violating coupling . In this approach, we have shown that although
the coefficient of Chern-Simons term can be found unambiguously in different
regularization schemes at zero or finite temperature, it remains undetermined.
We observe a correspondence among results obtained at finite and zero
temperature.Comment: To appear in JHEP, 10 pages, 1 eps figure, minor changes and
references adde
Aspects of Puff Field Theory
We describe some features of the recently constructed "Puff Field Theory,"
and present arguments in favor of it being a field theory decoupled from
gravity. We construct its supergravity dual and calculate the entropy of this
theory in the limit of large 't Hooft coupling. We also determine the leading
irrelevant operator that governs its deviation from N=4 super Yang-Mills
theory.Comment: 31 pages, 1 figur
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