A. V. Bogomolov

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.

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.

Dynamics and Energetics of the Thermal and Nonthermal Components in the Solar Flare of January 20, 2005, Based on Data from Hard Electromagnetic Radiation Detectors Onboard the CORONAS-F Satellite

Based on data from the SONG and SPR-N multichannel hard electromagnetic radiation detectors onboard the CORONAS-F space observatory and the X-ray monitors onboard GOES satellites, we have distinguished the thermal and nonthermal components in the X-ray spectrum of an extreme solar flare on January 20, 2005. In the impulsive flare phase determined from the time of the most efficient electron and proton acceleration, we have obtained parameters of the spectra for both components and their variations in the time interval 06:43–06:54 UT. The spectral index in the energy range 0.2–2 MeV for a single-power-law spectrum of accelerated electrons is shown to have been close to 3.4 for most of the time interval under consideration. We have determined the time dependence of the lower energy cutoff in the energy spectrum of nonthermal photons Eγ0(t) at which the spectral flux densities of the thermal and nonthermal components become equal. The power deposited by accelerated electrons into the flare volume has been estimated using the thick-target model under two assumptions about the boundary energy E0 of the electron spectrum: (i) E0 is determined by Eγ0(t) and (ii) E0 is determined by the characteristic heated plasma energy (≈5kT (t)). The reality of the first assumption is proven by the fact that plasma cooling sets in at a time when the radiative losses begin to prevail over the power deposited by electrons only in this case. Comparison of the total energy deposited by electrons with a boundary energy Eγ0(t) with the thermal energy of the emitting plasma in the time interval under consideration has shown that the total energy deposited by accelerated electrons at the beginning of the impulsive flare phase before 06:47 UT exceeds the thermal plasma energy by a factor of 1.5–2; subsequently, these energies become approximately equal and are ∼(4–5) × 1030 erg under the assumption that the filling factor is 0.5–0.6.

Experiment on the Vernov satellite: Transient energetic processes in the Earth’s atmosphere and magnetosphere. Part I: Description of the experiment

The program of physical studies on the Vernov satellite launched on July 8, 2014 into a polar (640 × 830 km) solar-synchronous orbit with an inclination of 98.4° is presented. We described the complex of scientific equipment on this satellite in detail, including multidirectional gamma-ray detectors, electron spectrometers, red and ultra-violet detectors, and wave probes. The experiment on the Vernov satellite is mainly aimed at a comprehensive study of the processes of generation of transient phenomena in the optical and gamma-ray ranges in the Earth’s atmosphere (such as high-altitude breakdown on runaway relativistic electrons), the study of the action on the atmosphere of electrons precipitated from the radiation belts, and low- and high-frequency electromagnetic waves of both space and atmospheric origin.

Hard X-ray Radiation from Solar Flares in the Second Half of 2001: Preliminary Results of the SPR-N Experiment Onboard the Coronas-F Satellite

The first results of the experiment with the SPR-N hard X-ray (20–100 keV) polarimeter onboard the Coronas-F observatory (the experiment started on August 15, 2001) are presented. Hard X-ray radiation was detected from several solar flares. The spectral and temporal parameters were determined and the polarization was estimated. Comparison with the GOES observations of thermal X-ray radiation shows that hard X-ray bursts occur at the growth phase of the thermal radiation and that they are associated with the bremsstrahlung of energetic electrons precipitating into the solar atmosphere.

Electron flux variations at altitudes of 600–800 km in the second half of 2014. preliminary results of an experiment using RELEC equipment onboard the satellite VERNOV

The results of measurements of fluxes and spectra carried out using the RELEC (relativistic electrons) equipment onboard the VERNOV satellite in the second half of 2014 are presented. The VERNOV satellite was launched on July 8, 2014 in a sun-synchronous orbit with an altitude from 640 to 830 km and an inclination of 98.4°. Scientific information from the satellite was first received on July 20, 2014. The comparative analysis of electron fluxes using data from RELEC and using experimental data on the electron detection by satellites Elektro-L (positioned at a geostationary orbit) and Meteor-M no. 2 (positioned at a circular polar orbit at an altitude of about 800 km as the VERNOV satellite) will make it possible to study the spatial distribution pattern of energetic electrons in near-Earth space in more detail.

The academic Chibis-M microsatellite

This paper describes the scientific goals and design developments of the Chibis microsatellite platform and the Groza scientific equipment, which are aimed at studying new physical mechanisms of high-altitude electrical discharges in the atmosphere. A description of the Groza scientific equipment is presented, which is a united flying instrument that determines the basic requirements for the Chibis-M microsatellite. The problems of ground training of the space experiment, methods of launching the microsatellite in the ISS infrastructure into orbit, and command and telemetry control in flight, as well as the first scientific results, are presented.

Correlation between the Earth’s outer radiation belt dynamics and solar wind parameters at the solar minimum according to EMP instrument data onboard the CORONAS-Photon satellite

The study of variations in the electron flux in the outer Earth radiation belt (ERB) and their correlations with solar processes is one of the important problems in the experiment with the Electron-M-Peska instrument onboard the CORONAS-Photon solar observatory. Data on relativistic and subrelativistic electron fluxes obtained by the Electron-M-Peska in 2009 have been used to study the outer ERB dynamics at the solar minimum. Increases in outer ERB relativistic electron fluxes, observed at an height of 550 km after weak magnetic disturbances induced by high-velocity solar wind arriving to the Earth, have been analyzed. The geomagnetic disturbances induced by the high-velocity solar wind and that resulted in electron flux variations were insignificant: there were no considerable storms and substorms during that period; however, several polar ground-based stations observed an increase in wave activity. An assumption has been made that the wave activity caused the variations in relativistic electron fluxes.

Stereoscopic Observations of Solar Flares Made Onboard the 2001 Mars Odyssey Spacecraft and CORONAS-F Satellite

The results of observations of solar hard radiation recorded by two spacecraft—2001 Mars Odyssey and CORONAS-F—which were located in the vicinity of Mars and Earth, respectively, are discussed. The HEND instrument, developed at the Space Research Institute of the Russian Academy of Sciences, recorded photons with energies ranging from 80 keV to 2 MeV, and the SPR and SONG instruments, developed at the Skobeltsyn Research Institute of Nuclear Physics of the Moscow State University, detected radiation in the energy interval from 15 keV to 100 MeV. The rising of the sunspot group 10486 in late October 2003, which had been observed from Martian orbit before it was seen from the Earth’s surface, is analyzed in detail. In this case, observations made from directions that differ by 24° showed a close-to-24 h advance for the detection of hard radiation of flares. Stereoscopic observations of M-class flares near the limb show that the overwhelming part of radiation with energies above 80 keV arises at heights that do not exceed 7–10 thousand km. Also reported are the results of observations of the powerful flare on August 25, 2001, by the two devices, which complement each other substantially. The processes resulting in the formation of high-energy radiation of solar flares are discussed.

The Solar Flare of November 4, 2001, and Its Manifestations in Energetic Particles from Coronas-F Data

Based on X-ray, gamma-ray, and charged-particle measurements with several instruments onboard the Coronas-F satellite and on ACE and GOES experimental data presented on the Internet, we investigate the parameters of the solar flare of November 4, 2001, and the energetic-particle fluxes produced by it in circumterrestrial space. The increase in relativistic-electron fluxes for about 1.5 days points to a moving source (shock front). The structure of the energetic-particles fluxes in the second half of November 5, 2001, can be explained by the passage of the coronal mass ejection that was ejected on November 1, 2001, and that interacted with the shock wave from the flare of November 4, 2001.