A.G. Demekhov (Institute of Applied Physics, 46, Ulyanov st., 603600, Nizhny Novgorod, Russia)

The mutual influence of pair interactions, such as charge exchange reactions and Coulomb collisions, and cyclotron wave-particle interactions in the ring current (RC) is considered. A dynamical self-consistent model including a bounce-averaged kinetic equation for the ion pitch angle distribution function and the equation for the wave spectral intensity is employed.

Temporal evolution of the ion distribution function and the wave spectrum with account of slow variations of the energetic ion source and the background plasma density is discussed. These variations represent important factors of the RC evolution during the main and recovery phases of a magnetic storm. It will be shown that (1) charge exchange reactions provide an anisotropy which can give rise to the cyclotron instability at a storm recovery phase when the external source of energetic ions is weak, and (2) combined action of pair and collective interactions significantly reduces the lifetime of the RC protons.

G.A. Mikhailova, Yu.M. Mikhailov, O.V. Kapustina (Institute of Terrestrial Magnetism, Ionosphere and Radiowave Propagation, Russian Academy of Science. Troitsk, Moscow region, 142092, Russia)

The results of digital processing of auroral hiss and whistler data, registered on Intercosmos 24 satellite on ~1000 km height at the pass over Novaya Zemlya island 17 minutes later the moment of the underground nuclear explosion have been presented. In result of power acoustic influence on the ionosphere and the magnetosphere abrupt increasing (~20 dB) of the intensity VLF hiss has been detected in narrow band of invariant latitudes (~3.9 degrees), including the disturbance source. Spectral power density was modulated with space intervals ~100 and 23 km. Simultaneously in the plasmasphere in wide latitudes interval from 50 up to 30 degrees the several groups of the whistlers with unusually number of echoes (>37) has been registered. One hop whistler of these groups had the same dispersion, and the time interval between the echoes was constant and equal 2.9+-0.2 sec.

A.G. Kolesnik, N.S. Panamarev (Siberian Phisio-Technical Institute, 634050, Russia, Tomsk, Revolutions 1)

In the present work one of heavily developped in last is considered time of mechanisms of shaping of dynamic spectra and generations ultra low-frequency (ELF) electromagnetic noise as atmospheric, and magnetospheric of an origin. It is based on the supposition, that on spectra electromagnetic oscillations in ionosphere essential influence natural resonance systems - a ionosphere alfvens resonator and resonator derivated by a surface of the Earth and low layers ionosphere. Influence of a resonator Earth-ionosphere on shaping of dynamic spectra ultra low-frequency electromagnetic oscillations is investigated by the analysis appropriate electrodynamic model.

Using an electrodynamic model a structure, consisting from spherical of a resonator enclosed by a non-stationary medium, conductivity which is periodic function of time, is shown, that dependence from time of a solution of the equations of the Maxwell should satisfy to the equation the Mathieu, the factors of which depend as on electrodynamic parameters ionosphere and from own frequencies of a resonator, derivated by a surface of the Earth and by low layers ionosphere. From the theory of the equations the Mathieu is known, that stable the solution exists only under certain conditions, which in our case depend on resonance properties of a nappe Earth-ionosphere. Functional dependence between spectra is thus determined electromagnetic oscillations in ionosphere and resonance properties of a resonator Earth-ionosphere.

N.G. Kleimenova, O.V. Kozyreva (Institute of the Earth Physics, Moscow 123810, Russia)

M. Bitterly, J. Bitterly (Ecole et Observatoire des Sciences de la Terra, Strasbourg 67084,France)

The comparison of the digital ground observations of the ipcl type of geomagnetic pulsations (T ~ 3-15 min) near polar cusp latitudes with night isolated substorm showed these pulsations suddenly disappear in time of the substorm onset. These results have been observed by studing of the ground observations at Dumont D'Urville (cusp latitudes) and Narssarssuaq (auroral zone) stations. The effect was stronger in summer season than in the winter. The same result has been obtained for two another pairs of longitude separated stations: Sodankyla (night side, auroral zone) - Cambridge Bay (day side, polar cusp) and College (night side, auroral zone) - Godhavn (day side, polar cusp). The described effect confirms the influence of substorm development to the day side cusp dynamics and location.

P.A. Bespalov (Institute of Applied Physics RAS, 46 Ulyanov st., 603600 Nizhny Novgorod, Russia)

Often, VLF emissions are characterized by the spectral form repetition with typical periods in three time intervals: 10-300 s, 2-6 s and 0,1-1 s. Now, there are appropriate models of generating quasiperiodic and chorus VLF emissions with the periods 10-100 s and 0,1-1 s, respectively. In this report, the problem of short periodic VLF emissions with typical periods 2-6 s is studied in more detail.

We studed a self-consistent problem of the interaction between electromagnetic VLF emission and electron radiation belts without ordinary simplifications because the electromagnetic pulse duration can be comparable with the variational time of the distribution function. We took into account both the linear dispersion in the nonuniform magnetospheric resonator and the cyclotron amplification variation during the pulse as a result of the wave-particle interaction. If the energetic electron distribution function has appropriate form, the consolidation of emission in packets reduces the dissipation of electromagnetic energy, and these processes can give a gain in energy. Consequently, the effective saturation of dissipation leads to rather short electromagnetic pulses. The sing of the spectrum inclination coincides with the sing of separated whistler inclination.

The cause of the excitation of short periodic VLF emissions is connected with the compensation of the dispersion signal transformation and the quasilinear evolution of the cyclotron instability increment as a result of the evolution of the distribution function during the electromagnetic pulse. The separated spectral elements are similar to whistlers. But, in contrast with multihop whistlers, they do not have the typical spectral form evolution from one signal to the other.

Acknowledgments. This work is supported by the Russian Foundation of Fundamental Researches (grant No. 98-02-16236).

M.I. Beloglazov (Polar Geophysical Institute, Apatity, Russia)

G.F. Remenets (Institute of Radiophysics, University of St.-Peterburg, Russia)

V.P. Nemirov (Physics department, University of St.-Peterburg, Russia)

In present paper the following VLF disturbances which we associate with the relativistic electron precipitations have been investigated: 20.10.85, 10.50-11.04-12.10UT; 23.10.85, 08.48-09.10-11.30UT; 25.03.86, 09.30-10.40-17.00UT; 27.03.86, 12.35-13.50-19.30UT; 22.04.86, 12.15-17.00-22.00UT; 23.04.86, 18.20-19.10-20.20UT; 05.05.86, 07.30-08.22-09.40UT. The intermediate time moments correspond to the VLF disturbance maximums. These disturbances have been selected according to the following characteristics sign that is the qualitative similarity in time behaviour (with minimums) of the amplitudes and phases for all radio signals in the range 10-14 kHz and for the middle zone of a radio source (880km). For these pointed disturbances the VLF inverse problems for some time moments including the disturbance maximums have been solved. The input data of the problems are the experimental amplitude and phase variations of the radio signals for a trace Aldra-Apatity completely located in auroral zone. To solve the VLF inverse problem we performed the minimization of a functional containing the differences of the experimental and calculated data, which were the radio signal relative amplitude and phase changes for three frequencies. VLF inverse problem has been solved in the set of unmonotonous electron concentration profiles [1] which approximate additional ionization process in upper atmosphere due to relativistic electrons below ionospheric D-region. Two minimization parameters z1 and BETA define such electron concentration profile Ne(z) to which corresponds the homogeneous conductivity between the heights Z0 and Z1 (two junction points of a function Ne(z)). The upper part of a profile (higher than z0) are identical to the undisturbed auroral daytime profile with z0=62 km. A parameter BETA is the increment of the lower part of the profile below the height z1. The parameters of the effective profiles obtained from the minimization and the corresponding effective heights h of the earth-ionosphere waveguide are given in theTable.

Anomalous attenuation of radio signal amplitudes (up to 8 times) during REPs of 20.10.85, 25.03.86, 27.03.86, 22.04.86, 23.04.86 resulted in effective heights in range 30-35 km. In the analysed cases of the electron precipitations we must state the uniqueness of the qualitative result relative to the unmonotony of effective profiles gained (with negative values of a BETA). The unmonotony is caused by a the reflection of the sporadic layer of ionization below the ionospheric D-region. Thus the analysis has confirmed the statement about relativistic electron (with energies more than 300 keV) precipitations along the radio trace investigated, which caused such anomalous ionization lower than 55-50 km during VLF disturbances considered.

[1] Remenets G.F. Unique ground VLF monitoring of relativistic electron precipitations // Problems of Geospace. - Austria, Vienna: Austrian Academy of Sci. Press, 1997. P. 273-278.

Kornilov I.A., Kornilova T.A. (Polar Geophysical Institute, Murmansk region, Apatity, 184200, Russia)

Pudovkin M.I., Kornilov O.I. (Institute of Physics, University of St-Petersburg, St-Petersburg, 198904, Russia)

Turunen T., Kultima J., Manninen J. (Sodankyla Geophysical Observatory, FIN-99600, Sodankyla, Finland)

On the base of TV auroral data and VLF emissions synchronously recorded during Russian-Finnish observational campaigns 1993-1997 the relationship between auroral breakups of different strength and VLF hiss in frequency band 200 Hz-5 kHz has been investigated. An analysis of 58 video records of auroral breakups and dynamic spectra of VLF-hiss has shown that two different types of breakups exist. Onset of the first type correlates with the appearance of intensive VLF hiss, though detailed time structure of hiss not always repeats the flashers of auroral arcs. Hiss was not detected for the second type of breakups. Comparison of some breakup characteristics such as an amplitude of magnetic perturbations, poleward expansion, lifetime of an active arcs and their longitude size demonstrated that breakups, correlated with VLF hiss are the ordinary ones, i.e. they lead to the full-scale substorm development, and the second type are pseudobreakups. Using riometric data it has been shown that hiss correlating breakups are accompanied by significant ionospheric absorption (1-3 db), no absorption were found for the second type breakups.

Kornilov I.A., Lubchich A.A. (Polar Geophysical Institute, Apatity, Murmansk region, 184200, Russia)

Statistical investigation by two different methods - shift correlation functions and epoch superposition analysis has been carried out for more than 100 hours of synchronous records of pulsating aurora and VLF emissions. It was shown that time sector 00h-07h LT can be subdivided for three time intervals. For those intervals fine time structure of pulsations and VLF emissions, relationship with magnetic pulsations, details of correlation between optical pulsations and chorus are quit different. In comparison with previous results on X-ray pulsations, the energy of precipitating particles, mechanisms of optical pulsations and VLF emissions generation are discussed.

I.A. Kornilov (Polar Geophysical Institute, Apatity, Murmansk region, 184200, Russia)

Analysis of integrated dynamic spectra of VLF emissions revealed emission intensifications on some frequencies looking like a stable frequency periodic structure on VLF spectrum with main frequencies about 250-400 Hz. Detailed study has shown that these periodic structure is a product of fundamental frequency very close to 50 Hz. The main differences between effect observed and normal power line harmonics usually visible on VLF dynamic spectra are large (about 50%) harmonic spectral broadening and absence of spectral power decreasing with increasing of harmonic number. Periodic spectral structures were found only for quiet time intervals and pseudobreakups, but not for the ordinary breakups. During pseudobreakup activisations on some frequencies of that periodic structure weak intensifications identified like a chorus elements were found. Careful correlation analysis revealed that stimulated chorus are accompanied by very weak auroral flashers with time delay about 1-2 sec. (aurora lead chorus).

D.L. Pasmanik, V.Y. Trakhtengerts (Institute of Applied Physics RAS, Nizhny Novgorod, Russia)

Formation of a zone of energetic electron precipitation during magnetic storm as they enter the region of enhanced background plasma density is analysed in the framework of the quasilinear theory of the cyclotron instability. As a source of energetic particles the magnetic drift following their injection at the nightside of the magnetosphere is considered. In contrast to previously performed analysis [1] the case of arbitrary initial distribution of energetic particles over energy is studied. As basic equations the set of self-consistent equations of quasilinear theory of cyclotron instability, including the equations for distribution function of energetic electrons and spectral density of whistler mode waves is used. The distribution function of energetic electrons is found. The dependencies of trapped and precipitating electron fluxes, electron energetic spectrum and whistler wave spectrum over longitudinal coordinate is analysed. Results obtained can be used for interpretation of experimental data on energetic electron precipitation at the evening side of magnetosphere on the recovery phase of magnetic storm.

This work was supported by the Russian Foundation for Basic Research, grant No. 96-02-16473a.

[1] D.L.Pasmanik, V.Y.Trakhtengerts, A.G.Demekhov, A.A.Lyubchich, E.E.Titova, T.Yahnina, M.J.Rycroft, J.Manninen, T.Turunen, A quantitative model for cyclotron wave-particle interactions at the plasmapause, Annales Geophysicae, 1997(in press).

Musatenko S.I. (Astronomical Observatory Kyiv State University)