S. N. Kuznetsov

Solar and Heliospheric Phenomena in October-November 2003: Causes and Effects

We present new observational data on the phenomena of extremely high activity on the Sun and in the heliosphere that took place in October–November 2003. A large variety of solar and heliospheric parameters give evidence that the interval under consideration is unique over the entire observation time. Based on these data, comparing them with similar situations in the past and using available theoretical concepts, we discuss possible cause-and-effect connections between the processes observed. The paper includes the first results and conclusions derived by the collaboration “Solar Extreme Events-2003” organized in Russia for detailed investigations of these events. As a result of our consideration, it is beyond question that the physical causes of solar and heliospheric phenomena in October–November 2003 are not exclusively local and do not belong only to the active regions and solar atmosphere above them. The energy reservoirs and driving forces of these processes have a more global nature. In general, they are hidden from an observer, since ultimately their sources lie in the subphotospheric layers of the Sun, where changes that are fast and difficult to predict can sometimes take place (and indeed they do). Solar flares can serve as sufficiently good tracers of these sudden changes and reconstructions on the Sun, although one can still find other diagnostic indicators among the parameters of magnetic fields, motions of matter, and emission characteristics.

Magnetic storms in October 2003

Preliminary results of an analysis of satellite and ground-based measurements during extremely strong magnetic storms at the end of October 2003 are presented, including some numerical modeling. The geosynchronous satellites Ekspress-A2and Ekspress-A3, and the low-altitude polar satellites Coronas-F and Meteor-3M carried out measurements of charged particles (electrons, protons, and ions) of solar and magnetospheric origin in a wide energy range. Disturbances of the geomagnetic field caused by extremely high activity on the Sun were studied at more than twenty magnetic stations from Lovozero (Murmansk region) to Tixie (Sakha-Yakutia). Unique data on the dynamics of the ionosphere, riometric absorption, geomagnetic pulsations, and aurora observations at mid-latitudes are obtained.

CORONAS-F satellite: Tasks for study of particle acceleration

Abstract A low altitude satellite with polar orbit, namely CORONAS-F has been launched on July 31, 2001. We briefly list the possibilities of a complex instrument SKL, and on the basis of similar measurements by CORONAS-I we illustrate the possible tasks for magnetospheric studies. Such orbit allows to sample with relatively high time resolution the projection series of various magnetospheric regions to low altitudes and to indicate changes within.

Gamma-ray emission and neutrons from solar flares recorded by the SONG instrument in 2001–2004

The SONG instrument onboard the CORONAS-F satellite recorded gamma-ray emission with energy above 500 keV in 28 solar flares over three years of its in-orbit operation. According to the GOES classification, the X-ray importance of these flares lay within the range M1.4-X28. The gamma-ray energy recorded by SONG exceeded 4 MeV in 16 flares. Gamma-ray emission with energy up to 100 MeV was recorded in three events, more specifically, on August 25, 2001, October 28, 2003, and November 4, 2003. Increases in the count rate in the SONG channels that recorded neutrons with energies above 20 MeV were found during these three events. The energies of the recorded neutrons were estimated for the neutron increases. The time dependence of the neutron increases was compared with data from high-altitude ground-based neutron monitors that could, in principle, record the arrival of high-energy neutrons from the Sun. It should be noted that we detected series of flares with gamma-ray emission generated by the same active region (AR). The series in the last decade of August 2002 (AR NOAA 0069), the end of May 2003 (AR NOAA 0365), and the famous period of extreme solar activity in October–November 2003 associated with AR NOAA 0486 and AR NOAA 0501 are quite revealing. The catalog can be of use for future statistical and correlation analyses of solar flares.

First results of investigating the space environment onboard the Universitetskii-Tatyana satellite

The complex of scientific pay load installed onboard the research and educational Universitetskii-Tatyana microsatellite of Moscow State University is described. The complex is designed to study charged particles in the near-earth space and ultraviolet emissions of the atmosphere. Data of the measurements of charged particle fluxes in the microsatellite orbit are presented, spectra are calculated, and the dynamics of penetration boundaries for protons of solar cosmic rays (SCR) during geomagnetic disturbances in 2005 is investigated. Intensities of the ultraviolet emission are measured in the entire range of variation of the atmospheric irradiation, as well as intensities of auroras in the polar regions of the Northern and Southern hemispheres. The experimental data on flashes of ultraviolet radiation (transient light phenomena in the upper atmosphere) are considered, and some examples of oscillograms of their temporal development and their distribution over geographical coordinates are presented.

Dayside magnetopause models

Abstract A review of empirical data-based models of the magnetopause and a comparative analysis are given with special attention to the dynamics of the dayside boundary. Recently different research groups have presented new magnetopause models as an alternative to the model of Roelof and Sibeck (1993, J. Geophys. Res. 94, 15, 125). All models have a greater parametric extent than the model of Roelof and Sibeck and allow prediction of the magnetopause location during extreme solar wind and IMF conditions. The models of Shue et al. (1997, J. Geophys. Res. 102, 9497–9511) and Kuznetsov et al. (1998) , developed using classic multi-factor regression analysis are two-dimensional and bivariate. The model of Dmitriev et al. (1999) created using artificial neural networks (ANNs) is three-dimensional and contains multiple parameters. A statistical study of Kuznetsov et al. confirmed by the ANN modeling of Dmitriev et al. has shown that the shape of dayside magnetopause has dawn–dusk asymmetry. The uncertainty in the determination of the dayside magnetopause position is practically the same for these models in spite of some discrepancies of the model results caused by different data sets, different assumptions and functional forms, different treatment methods of the models.

Polarization, Temporal, and Spectral Parameters of Solar Flare Hard X-rays as Measured by the SPR-N Instrument Onboard the CORONAS-F Satellite

The SPR-N polarimeter onboard the CORONAS-F satellite allows the X-ray polarization degree to be measured in energy ranges of 20–40, 40–60, and 60–100 keV. To measure the polarization, the method based on the Thompson scattering of solar X-ray photons in beryllium plates was used; the scattered photons were detected with a system of six CsI(Na) scintillation sensors. During the observation period from August 2001 to January 2005, the SPR-N instrument detected the hard X-rays of more than 90 solar flares. The October 29, 2003, event showed a significant polarization degree exceeding 70% in channels of E = 40–60 and 60–100 keV and about 50% in the 20-to 40-keV channel. The time profile of the polarization degree and the projection of the polarization plane onto the solar disk were determined. For 25 events, the upper limits of the part of polarized X-rays were estimated at 8 to 40%. For all the flares detected, time profiles (with a resolution of up to 4 s), hard X-ray radiation fluxes, and spectral index estimates were obtained.

Investigations of the space environment aboard the Universitetsky-Tat’yana and Universitetsky-Tat’yana-2 microsatellites

The first results obtained through the university small satellites program developed at Moscow State University (MSU) are presented. The space environment was investigated aboard two MSU microsatellites designed for scientific and educational purposes, Universitetsky-Tat’yana and Universitetsky-Tat’yana-2. The scientific equipment is described to study charged particles in near Earth space and atmospheric radiations in ultraviolet, red, and infrared optical wavelength ranges. The dynamic properties of fluxes of charged particles in microsatellite orbits are studied and findings are presented regarding specific parameters of solar proton penetration during the geomagnetic disturbances. Experimental results are considered concerning flashes of ultraviolet (UV), red (R), and infrared (IR) radiation that are transient light phenomena in the upper atmosphere. The space educational MSU program developed on the basis of the Universitetsky-Tat’yana projects is reviewed.

Solar wind magnetic field and pressure during magnetopause crossings at geosynchronous orbit

Abstract Solar wind dynamic pressure and the Bz component of the interplanetary magnetic field are analysed for time intervals from 1967–1993 when the magnetopause was observed at geosynchronous orbit (84 crossings). We conclude that: (1) when Bz>0 the pressure balance at the magnetopause corresponds to the gas dynamic theory and the shape of the magnetopause is well approximated by a parabolic model; (2) when −6 0; (3) under both Bz>0 and Bz

SOLAR WIND CONTROL OF THE MAGNETOPAUSE SHAPE AND LOCATION

S. N. KUZNETSOV and A. V. SUVOROVA Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow 119899, Russia Abstract--We made statistical studies of a large data set of magnetopause crossings, that were measured aboard many spacecraft. This data was matched with simultaneous solar wind parameters. We have quantified the magnetopause response to variations of solar wind dynamic pressures and interplanetary magnetic field intensities and orientation. We concluded that location of the subsolar point is a function of solar wind pressure alone when the z component interplanetary magnetic field (IMF Bz) > - 2 nT but it is a complex function of solar wind dynamic pressure and IMF Bz when Bz 0 nT (388 points), -2<Bz<0nT (207) and Bz< -2nT (207). We first studied correlations between the magneto- pause distance and five solar wind parameters (n, V,P,Bz,F) in each bin. We found that all of these parameters except the velocity have good correlations with R, and correlations with the density are similar but smaller than with the pressure. So we chose only two solar wind parameters, pressure and Bz, for our further analysis of the magnetopause shape. Figures 1-3 demonstrate the correlation co- efficients for pairs (R,P) and (R,Bz) vs angle. Each figure corresponds to a given Bz subset. One can see that R has the best correlation coefficient with dynamic pressure mainly for the nose part of the magnetopause (0 < 50 °) when Bz is northward. For 413