INTERCHANGE INSTABILITY AT THE MINIMUM B CONFIGURATION

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.