789 research outputs found
Low energy particle fluxes in the geomagnetic tail
Low energy particle fluxes in geomagnetic tail, and plasma sheet relation to auroral ova
Low energy electrons in the magnetosphere as observed by OGO-1 and OGO-3
Low energy electrons in magnetosphere as observed by OGO satellite
Towards a relativistic statistical theory
In special relativity the mathematical expressions, defining physical
observables as the momentum, the energy etc, emerge as one parameter (light
speed) continuous deformations of the corresponding ones of the classical
physics. Here, we show that the special relativity imposes a proper one
parameter continuous deformation also to the expression of the classical
Boltzmann-Gibbs-Shannon entropy. The obtained relativistic entropy permits to
construct a coherent and selfconsistent relativistic statistical theory [Phys.
Rev. E {\bf 66}, 056125 (2002); Phys. Rev. E {\bf 72}, 036108 (2005)],
preserving the main features (maximum entropy principle, thermodynamic
stability, Lesche stability, continuity, symmetry, expansivity, decisivity,
etc.) of the classical statistical theory, which is recovered in the classical
limit. The predicted distribution function is a one-parameter continuous
deformation of the classical Maxwell-Boltzmann distribution and has a simple
analytic form, showing power law tails in accordance with the experimental
evidence.Comment: Physica A (2006). Proof correction
Magnetic reconnection with anomalous resistivity in two-and-a-half dimensions I: Quasi-stationary case
In this paper quasi-stationary, two-and-a-half-dimensional magnetic
reconnection is studied in the framework of incompressible resistive
magnetohydrodynamics (MHD). A new theoretical approach for calculation of the
reconnection rate is presented. This approach is based on local analytical
derivations in a thin reconnection layer, and it is applicable to the case when
resistivity is anomalous and is an arbitrary function of the electric current
and the spatial coordinates. It is found that a quasi-stationary reconnection
rate is fully determined by a particular functional form of the anomalous
resistivity and by the local configuration of the magnetic field just outside
the reconnection layer. It is also found that in the special case of constant
resistivity reconnection is Sweet-Parker and not Petschek.Comment: 15 pages, 4 figures, minor changes as compared to the 1st versio
2D stationary resistive MHD flows: borderline to magnetic reconnection solutions
We present the basic equations for stationary, incompressible resistive MHD
flows in two dimensions. This leads to a system of differential equations for
two flux functions, one elliptic partial differential equation
(Grad-Shafranov-like) for the magnetic flux function and one for the stream
function of the flow. In these equations two potentials appear: one potential
is a generalized pressure. The second potential couples the magnetic and the
flow shear components of the system. With the restriction to flux or at least
line conserving flows one has to solve a modified Ohm's law. For the two
dimensional case these are two coupled differential equations, which represent
the borderline between the resistive but flux conserving (or line conserving)
case, and that of reconnective solutions. We discuss some simplified solutions
of these equations.Comment: 5 pages, 2 figures, Advances in Space Research (in press
Observations of low energy electrons with the OGO-A satellite.
Massachusetts Institute of Technology. Dept. of Physics. Thesis. 1966. Ph.D.Bibliography: leaves 117-129.Ph.D
Self-similar solution of fast magnetic reconnection: Semi-analytic study of inflow region
An evolutionary process of the fast magnetic reconnection in ``free space''
which is free from any influence of outer circumstance has been studied
semi-analytically, and a self-similarly expanding solution has been obtained.
The semi-analytic solution is consistent with the results of our numerical
simulations performed in our previous paper (see Nitta et al. 2001). This
semi-analytic study confirms the existence of self-similar growth. On the other
hand, the numerical study by time dependent computer simulation clarifies the
stability of the self-similar growth with respect to any MHD mode. These
results confirm the stable self-similar evolution of the fast magnetic
reconnection system.Comment: 15 pages, 7 figure
The VOISE Algorithm: a Versatile Tool for Automatic Segmentation of Astronomical Images
The auroras on Jupiter and Saturn can be studied with a high sensitivity and
resolution by the Hubble Space Telescope (HST) ultraviolet (UV) and
far-ultraviolet (FUV) Space Telescope spectrograph (STIS) and Advanced Camera
for Surveys (ACS) instruments. We present results of automatic detection and
segmentation of Jupiter's auroral emissions as observed by HST ACS instrument
with VOronoi Image SEgmentation (VOISE). VOISE is a dynamic algorithm for
partitioning the underlying pixel grid of an image into regions according to a
prescribed homogeneity criterion. The algorithm consists of an iterative
procedure that dynamically constructs a tessellation of the image plane based
on a Voronoi Diagram, until the intensity of the underlying image within each
region is classified as homogeneous. The computed tessellations allow the
extraction of quantitative information about the auroral features such as mean
intensity, latitudinal and longitudinal extents and length scales. These
outputs thus represent a more automated and objective method of characterising
auroral emissions than manual inspection.Comment: 9 pages, 7 figures; accepted for publication in MNRA
Magnetic Reynolds number dependence of reconnection rate and flow structure of the self-similar evolution model of fast magnetic reconnection
This paper investigates Magnetic Reynolds number dependence of the
``self-similar evolution model'' (Nitta et al. 2001) of fast magnetic
reconnection. I focused my attention on the flow structure inside and around
the reconnection outflow, which is essential to determine the entire
reconnection system (Nitta et al. 2002). The outflow is consist of several
regions divided by discontinuities, e.g., shocks, and it can be treated by a
shock-tube approximation (Nitta 2004). By solving the junction conditions
(e.g., Rankine-Hugoniot condition), the structure of the reconnection outflow
is obtained. Magnetic reconnection in most astrophysical problems is
characterized by a huge dynamic range of its expansion ( for typical
solar flares) in a free space which is free from any influence of external
circumstances. Such evolution results in a spontaneous self-similar expansion
which is controlled by two intrinsic parameters: the plasma- and the
magnetic Reynolds number. The plasma- dependence had been investigated in
our previous paper. This paper newly clarifies the relation between the
reconnection rate and the inflow structure just outside the Petschek-like slow
shock: As the magnetic Reynolds number increases, strongly converging inflow
toward the Petschek-like slow shock forms, and it significantly reduces the
reconnection rate.Comment: 16 pages. to appear in ApJ (2006 Jan. 20 issue
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