A.I. Podgorny (Lebedev Institute of Physics RAN, Moscow, Russia)

During a solar flare the magnetic energy is transformed into the energy of radiation and the energy of plasma motion - coronal mass ejection. This ejection produced the disturbance in the interplanetary media, which caused the magnetospheric substorms. Initial energy release in the solar flare takes place high in the solar corona. The energy released explosively due to instability of the current sheet, which was created in the vicinity of the singular line of the coronal magnetic field. Numerical simulation [1] of current sheet creation for the solar flare May 30, 1991 showed the possibility of coronal mass ejection. The system of 3D MHD equations for compressible plasma with dissipative terms was solved for a magnetic field configuration corresponded to spots positions for the active region NOAA 6654 which produced the flare on May 30, 1991. The PERESVET code was used for solving MHD equations by an absolutely implicit scheme, which was solved by the iteration method.

Some new approaches were used. Calculations were carried out in several regions of different scales to separate physical effects from numerical ones. It is important for calculations in real active region with strong magnetic field gradient near the photosphere. The calculations permitted to find out types of disturbances on the photosphere which produced a strong current sheet. In the asymmetric field of the chosen active region the current sheet was turned at the large angle to the photosphere plane. The current sheet became almost vertical. So, the condition for coronal mass ejection appeared because of the force of magnetic tension which pushed plasma out of the sheet during its instability upward from the Sun.

[1] Podgorny A.I. and I.M. Podgorny. Solar Physics 182, 159 (1998).

I.M. Podgorny (Institute for Astronomy RAN, Moscow, Russia)

The term "solar flare" was introduced in 1946 by H. Newton as a name of the phenomena, which consisted in appearance of a burst of visible radiation in the Sun active region about 20 hours before the beginning of a magnetic storm on the Earth.

Since 1993 several papers proclaimed that appearance of substorms is independent of solar flares. They confirm that substorms are produced by transients, but solar mass ejection is not connected with the solar flare. Many observations data and results of numerical simulation show that this statement is unacceptable. It is shown that misunderstanding has occured, as the solar flares development does not always occur according to the same scenario. Sometimes a flare produces very strong solar mass ejection, but very weak visible radiation. In that case the appearance of some flares prior to a substorm can not be detected by visible radiation. The proposed mechanism of solar mass ejection is based on local chromospheric evaporation in fast electrons precipitation at the current sheet disruption or by local chromospheric heating by Pedersen current, which closes the upward and downward field aligned currents. In that case a post flare loop appears [1]. If powerful plasma streams from both legs of a loop meet on the loop top, an upward plasma jet is produced. The jet motion in the perpendicular magnetic field creates a vertical current sheet and solar plasma ejection from the Sun. Later, this current sheet becomes unstable. Results of numerical simulation are compared with Yohkoh soft x-rays measurements.

[1] A.I. Podgorny and I.M. Podgorny Astronom. Rep. 42, 116 (1998).

A.A. Galeev, A.M. Sadovski (Space Research Institute of Russian Academy of Sciences Moscow, Russia)

Axford and Mc Kenzie [1992] suggested that the energy released in impulsive reconnection events (``microflares'') generates high frequency Alfven waves with the period of the order of 1 second. The kinetic equation for spectral energy density of waves is derived in the random phase approximation. Solving this equation we find the wave spectrum with the power low ``-1'' in low frequency range which is matched to spectrum above the spectral brake with the power low ``-1.5''. No fitting parameters are required for this. The heating rate of the solar wind protons due to the dissipation of Alfven waves is obtained.

V.C. Roldugin, Yu.P. Maltsev, E.V. Vashenyuk, A.N. Vasiljev (Polar Geophysical Institute, Apatity, Russia)

Kh. Fadel (Institute of Space Physics, Kiruna, Sweden)

The variations of the first Schumann resonance frequency in Lovozero are investigated for three proton events on November 6, 1997, May 2 and May 8, 1998. It is found that during the peaks of the proton penetrations the frequency decreases by 0.15 Hz. It was observed also an increase of the frequency during the very intensive solar X-ray burst accompanying the proton flare on 6 November. The frequency decrease effect is explained by changes of dielectric permeability in the cavity Earth - ionosphere, especially in its part which is mainly responsible for the formation of the Schumann wave.

A.A. Lubchich (Polar Geophysical Institute, Apatity, Russia)

M.I.Pudovkin (Institute of Physics, State University St.Petersburg, Russia)

Reflection and transmission of small amplitude magnetohydrodynamic (MHD) waves of solar-wind origin through the Earth’s open magnetopause are studied. The open magnetopause with a nonzero normal component of magnetic field is assumed to be a rotational discontinuity. Transmission of MHD waves through the rotational discontinuity has been considered earlier. For instance, L.C.Lee (Planet. Space Sci., V.30, 1127, 1982) has studied the transmission of Alfvé n waves for a rotational discontinuity in which the magnetic field rotates by 180° across the boundary. Y.C.Kwok and L.C.Lee (J. Geophys. Res., V.89, 10697, 1984) have studied the transmission of any of the incident waves for any rotational discontinuity. However, correctness of the results obtained in the last paper (for example, existing of the very high amplification regions and non-zero amplitude of transmission entropy wave for the case of an incident non-entropy wave) is doubtful. We performed the more accurate consideration and got different results. We also found that for any incident wave, there is one reflected wave (usually, it is a fast magnetosonic wave, but under some specific conditions it can be a slow magnetosonic wave) and five transmitted waves (one fast magnetosonic wave, two slow magnetosonic waves, one Alfvé n wave and one entropy wave). The transmitted entropy wave appears only in the case of the incident entropy wave. Dependence of the transmission and reflection coefficients on the type of incident wave, the incident angle (all possible angles are included into the consideration), the orientation and strength of the ambient magnetic field is studied. In contrast to the result of Kwok and Lee, fluctuations are found to be amplified insignificantly across the rotational discontinuity.

На данных основаниях предложен и реализован способ оценки вклада частиц пенумбры в возрастания скоростей счёта нейтронных мониторов.

T.A. Hviuzova, S.V. Leontyev (Polar Geophysical Institute, Apatity, Russia)

The heliospheric current sheet (HCS) is registered as sector structure boundary. Investigations of the spectral characteristics of aurora during crossing the quiet and disturb HCS are shown: 1) Brightness of the green emission is increasing with the growth as velocity of the solar wind as the south component of IMF. However this increase is some quicker for the quiet HCS. 2) Probability of appearing and intensity of the 678.9 nm (1PGN₂) emission are increasing with growth of green emission intensity. 3) The emission (630.0/557.7) ratio describing the energy of precipitating electrons is equal to 0.4 for the quiet HCS and 0.6 for the disturb HCS on the average. This ratio is changing during the solar cycle and depending on the magnetic field of the Sun. 4) The comparison of the aurora characteristics for the quiet and disturb HCS shows the spectrum of precipitating electrons during the disturb HCS is bandwidther and softer.