O.V. Mingalev, Yu.P. Maltsev (Polar Geophysical Institute, Apatity)
The interchange instability criterion by
Kadomtsev is applied to the configurations with a minimum in the magnetic
field radial distribution. The magnetospheric plasma is shown to be unstable
in the region where the field decreases sufficiently fast toward the field
line curvature center. The growth time of the instability for a number
of the reported minimum B profiles is several tens of seconds.
CURRENT STATE AND DEVELOPMENT OF TOMOGRAPHY TECHNIQUE IN THE ROY PROJECT
Yu.I. Galperin 1, L.M. Zelenyi
1, M.V. Veselov 1, I.V. Silin 2, V. Kunitsyn
2, J. Buchner 3, B. Nikutowski 3, T. Wiegelmann
3
1 Space Research Institute
of Russian Academy of Sciences, Moscow, Russia
2 Faculty of Physics, Moscow
State University, Moscow, Russia
3 Max Planck Institut fur
Aeronomie, Katlenburg-Lindau, Germany
The ROY Project is aimed at studying of
previously unexplored small-scale phenomena within the so called "diffusion
region" where strong plasma turbulence and magnetic "reconnection" occur.
To study these phenomena multi-point measurements are essential at scales
down to ion Larmor radius and lower. The aim of these measurements is to
determine spatial scales of plasma turbulence, characteristic amplitudes
and velocities of plasma and magnetic field inhomogeneities.The orbit with
an apogee ~12Re, a perigee ~5000 km and inclination 62.5 degrees is selected
to provide the optimal coverage of the key magnetospheric regions. The
project includes a group of satellites consisting of the main (BASE) satellite
and 4 subsatellites at distances 10-300 (1000) km. The BASE satellite is
equipped with omnidirectional emitting MF-antennas, the full set of particle,
field and wave plasma diagnostic instrumentation. The subsatellites will
have thrusters to control orbital configuration. They will perform comprehensive
in situ plasma measurements. One of the original experiments of ROY mission
is radio tomographic reconstruction of plasma density cross-sections. The
method is based on the radio waves dispersion in plasma. To avoid the probing
wave distortion its frequency should be higher than 100 kHz. The bearing
wave frequency can be as high as 1 MHz. The reconstruction resolution of
the plasma density is limited by the Fresnel zone diameter. For ROY configuration
it makes ~30 km. The following configuration for the mission was proposed:
all the subsatellites are placed along plasma streamline so that the angle
between the rays from BASE to the first and the last subsatellite makes
at least 100 degrees. All the satellites will be kept almost in one plane.
A series of numerical simulations were performed in order to determine
the quality of reconstructions of various electron density profiles. In
our work we used results of the 3D kinetic simulations of reconnection
processes. The reconstructed electron density distribution is represented
as a piece-planar function and the integral problem is reduced to a system
of algebraic equations (inversion system). When the number of measurements
is higher than the number of grid points in density profile the inversion
system is over-determined. It was discovered that the solutions of inversion
system in over- and under-determined cases are very close.
PENETRATION OF THE MAGNETIC AND ELECTRIC FIELDS FROM THE SOLAR WIND INTO THE MAGNETOSPHERE
O.A. Ryzhova (Kola Branch of the Petrozavodsk
University, Apatity)
Yu.P. Maltsev (Polar Geophysical Institute,
Apatity)
If the solar wind plasma were perfectly
conductive its magnetic and electric fields would not penetrate into the
magnetosphere. It is well known that the scale time of penetration of the
dawn-to-dusk electric field into the magnetosphere is smaller than 1 hour.
The estimates show that such a small time suggests extremely small magnetic
Reynolds number not exceeding 10, the latter value being ten orders smaller
than that predicted by the classical conductivity model. The effective
conductivity of the solar wind thus appears to be very low. We calculated
the penetration of the electric and magnetic fields from weakly conductive
plasma into a non-conductive sphere. When the plasma conductivity tends
to zero the magnetic field penetrates into the sphere completely, but the
extent of the electric field penetration tends to 75%.
SIMPLE MODEL OF THE MAGNETOSPHERIC MAGNETIC FIELD
A.A. Ostapenko, Yu.P. Maltsev (Polar Geophysical Institute, Apatity)
A magnetic field model is suggested for
distances up to 40 Earth's radii. The model depends on the dipole tilt
angle, Dst and Kp indices, solar wind dynamic pressure, and IMF vertical
component. An advantage of this model over the Tsyganenko-96 model is much
simpler field presentation as well as better agreement with observations.
3D ANN DAYSIDE MAGNETOPAUSE MODEL: APPLICATION FOR SUBSOLAR POINT AND CUSP DYNAMICS
A.V. Dmitriev and A.V. Suvorova
(Skobeltsyn Institute of Nuclear Physics,
Moscow State University, Moscow, Russia)
The code of 3D Artificial Neutral Network
Model of Dayside Magnetopause is applied for description of the dynamics
of subsolar point and cusp region under different solar wind and interplanetary
magnetic field conditions. The dependence of the subsolar point location
on the dynamic pressure and IMF Bz- and By- components is expressed in
the form of modified logistic function which permits to describe three
different regimes of magnetopause formation controlled by IMF Bz-component.
The dynamics of the cusp region extension in longitudes and latitudes is
presented. Effects of "dimple" formation in the region of the subsolar
point and the cusp disappearance under strong negative Bz (<-10nT) are
described.
О ГАМИЛЬТОНОВСКОМ ФОРМАЛИЗМЕ ДЛЯ ГИДРОДИНАМИЧЕСКИХ МОДЕЛЕЙ ПЛАЗМЫ
В.П. Козелов (Полярный геофизический институт, Апатиты)
Обсуждаются трудности обычно используемого
в гидродинамических моделях плазмы гамильтоновского формализма, рассматривающего
сплошную среду, как систему с континуальным числом степеней свободы. Предлагается
в гидродинамических моделях использовать канонический формализм для описания
движения отдельной жидкой частицы, имеющей конечное число (двенадцать)
степеней свободы. Показаны преимущества такого подхода и его связь со стандартным.
Выписаны лагранжианы и канонические уравнения для многокомпонентной плазмы,
холловской и электронной магнитных гидродинамик.
STUDY OF THE CUSP/CLEFT STRUCTURES BY HF RADAR AND INTERBALL-1, 2
V.L. Khalipov 1,L.V. Shestakova
1,R.A. Kovrazhkin 2, S.P. Savin 2, J.A.
Sauvaud 3, A.E. Stepanov 1,S.K. Rybchuk 1,
G.A. Vladimirova 2
1 Institute of Cosmophysical
Research and Aeronomy, Yakutsk
2 Space Research Institute,
Moscow
3 CESR-CNRS, Toulouse
The data of INTERBALL Tail and Auroral
satellites on electron and ion precipitations and oblique reflections from
HF sounding station with horizontal rhombic antenna in Tixie Bay (130 deg.E,
L=5.6) are analyzed. Two kinds of radio reflections are observed in the
ionograms when the daytime cusp/cleft region is sounded by the ionozonde.
(1) Oblique radio reflections, with pronounced delay due to the abrupt
latitude ionization gradient in the F - region connected with the equatorward
edge of the daytime polar cusp. (2) Oblique radio reflections without any
delay (often multiple), originating from intense scattering in the region
of the discrete auroral arcs in the daytime auroral region. These characteristic
reflections are compared with patterns of particle precipitations and field
disturbances measured aboard the satellites.
SOME ION DISPERSION SIGNATURE FEATURES EXPLAINED WITH A SIMPLE MODEL
M.Yu. Goncharova (Polar Geophysical Institute, Apatity, Russia)
The ion dispersion signatures observed
at the low-altitude satellites often show features which make difficult
their recognition, classification and measurements: the absence of the
high-energy portion of the precipitating particles, the dependence of the
lower energy cutoff shape on the removed intensity level, the overlapping
injections etc.. Simple model for the ion dispersion signature instantly
detected within a small latitude range is calculated. Some of the observed
dispersion features can be explained with it.
EVALUATION OF DEGREE OF THE PLASMA SHEET ION PRESSURE ANISOTROPIES
S.V. Dubyagin, M.V. Kubyshkina, V.A. Sergeev
(Institute of Physics, State University,
St. Petersburg, St. Petergof, Russia)
To evaluate the ion pressure anisotropy,
we compare the values of pressure in the ionospheric and equatorial parts
of the field line. Ionospheric values were computed from NOAA low-orbital
satellite measurements and compared with the model-based pressure estimates
and empirical formulas. Three different techniques of projection of the
plasma pressure measurements from plasma sheet to low altitude have been
used, each based on large statistics. From these comparisons we found that
in the plasma sheet at geocentric distances 9-20 Re the pressure values
at near-Earth and equatorial parts of the field line generally agree to
within 15%. Reasonable agreement of plasma sheet current computed from
pressure gradient and from model, as well as an agreement between experimental
and model-based estimates of plasma pressure indicate that the Ampere force
is mostly balanced by the gradient of the scalar pressure.
ACCRETION MAGNETIZED PLASMA ON THE GRAVITATIONAL CENTER
S.A. Dyadechkin, V.S. Semenov
(Institute of Physics, State University,
St. Petersburg, St. Petergof, Russia)
Magnetic field frozen in protoclouds appreciably
affect on formation and evolution of young stellar objects (YSO). Many
effects in the vicinity of YSO are associated with magnetic field (e.g.
bipolar flows, optical jets).
In the description of magnetohydrodynamics
(MHD) phenomena the concept of a magnetic flux tube frozen into the plasma
flow often plays an important role. We use here a method of introducing
lagrangian coordinates into MHD equations, which enable a convenient mathematical
formulation for the behaviour of flux tube. With the introduction of lagrangian
coordinate system co-moving with the flux tube the MHD equation of motion
reduces to a set of nonlinear string equation. The behaviour of flux tubes
can therefore be studied through solving the string equation.
Behaviour the string and free particle
in the gravitational field are very different. If the free particle has
non-zero aimed parameter gravitational center never can capture it, however
the string can be captured.
STRUCTURE OF AURORAL PRECIPITATIONS WITHIN DAYSIDE SECTOR
B.V. Rezenov, V.G. Vorobjev, G.V. Starkov
(Polar Geophysical Institute, Apatity, Russia)
Ya.I. Feldstein, L.I. Gromova (Institute
of Terrestrial Magnetism and Radiowave Propogation, Troitsk, Russia)
The dynamics of various auroral precipitations
into dayside sector from data of DMSP 6 and 7 satellite are investigated
for different magnetic levels. The variations of location of the auroral
precipitation boundary were compared to dynamics of the auroral oval and
diffuse luminosity. It is shown that auroral oval during the evening hours
is located on the boundary between hard (CPS) and soft (BPS) precipitations
regions and during the morning hours it is located in the equator part
of soft precipitations. The boundary of diffuse luminosity coincide with
the equator boundary of hard precipitation. This structure remains unchanged
for all levels of magnetic activity, but all the structure moves equatorwaerd,
with the magnetic activity increasing. We did not obtain the gap between
hard and soft precipitations, that has been obtain earlier by other investigators.
EFFECTS OF SELF-ORGANIZED CRITICALITY IN SOME GEOPHYSICAL PROBLEMS
D. I. Iudin 1, B. V. Kozelov
2, E. E. Titova 2, V. Yu. Trakhtengerts 3
1 Radiophysical Research
Institute, Nizhny Novgorod, Russia
2 Polar Geophysical Institute,
Apatity, Russia
3 Institute of Applied Physics,
Nizhny Novgorod, Russia
Recent studies have revealed certain features
of universal behaviour in many geophysical processes, which were called
self-organized criticality (SOK). The SOK effects arise in open systems
with sources and sinks of energy. They manifest themselves in the self-similarity
of dynamics at different spatio-temporal scales and in formation of universal
frequency spectra of the phenomena. As a rule, these peculiarities are
almost independent on the internal composition of the system under consideration.
In this report, we illustrate SOK effects by the fractal dynamics of atmospheric
electric discharges. We also discuss possible manifestations of SOK in
the cyclotron instability of the Earth's radiation belts.
DAYSIDE AURORAL TRANSIENT EVENTS: GLOBAL MORPHOLOGICAL FEATURES AND ASSOCIATED INTERPLANETARY MEDIUM SIGNATURE.
V.G. Vorobjev, O.I. Yagodkina (Polar
Geophysical Institute, Apatity, Russia)
D.G. Sibeck, C.-I. Meng (Applied Physics
Laboratory, Johns Hopkins University, Laurel, MD,USA)
We have analyzed morphological features of dayside auroral transient events (ATE) using images acquired from the ultraviolet imager (UVI) on board the Polar satellite. The UVI data set used for the investigation covers a time of about 5 winter months, from Dec. 3, 1996 to Feb. 28, 1997 and from Oct. 19 to Dec. 23 in 1997. During period under investigation we found 31 cases of the auroral transient events in the pre noon sector while only 12 events of auroral transients were registered in the after noon sector. Pre noon ATEs generally appear as the bright “spot” of auroral luminosity in 08-10 MLT sector at the latitudes between 74.50-76.50 CGL. Bright aurorae then quickly shifted westward and the poleward part of the bright spot contained the discrete aurorae moved poleward as well. Afternoon ATEs usually appear like a sudden intensification of aurorae in the 14-16 MLT sector at 75,50-78,50 CGL. Bright band of luminosity quickly extended eastward achieving in 15-20 min the longitude of 20-21 MLT at 700-720 CGL. Global features of auroral luminosity evolution during 5 SSC events have been investigated as well. We have analyzed the interplanetary medium conditions during the pre noon ATEs, the after noon ATEs and the SSCs registrations. In the paper the comparative characteristics both of morphological features of three auroral phenomena and the interplanetary magnetic field and solar wind plasma changes associated with different auroral events are presented.