Observations of auroral kilometric radio emission on the <Emphasis Type="Italic">Interball-1</Emphasis> satellite in the active Sun period 1999–2000

Results of almost two years (January 1999–October 2000) of continuous observations of auroral kilometric radio emission with the instrument AKR-X onboard the high-apogee satellite of the Earth Interball-1 are presented. The observations were conducted at the growth stage (in 1999) and in the maximum (2000) of solar activity within the 100–1500 kHz frequency band. The results of AKR detection in the vicinity of the maximum of its spectrum at a frequency of 252 kHz are presented. Both similarity (for example, the character of global directivity) and important differences from the AKR emission observed during the solar activity minimum [5] are found. Together with very high sporadicity, strong seasonal changes in the intensity are typical for the emission. It is completely absent in the spring-summer period in the Northern Hemisphere and is strongly suppressed in this period in the Southern Hemisphere. Probable nature of these features of AKR is discussed.     

Fluxes of low-energy particles in quiet periods of solar activity and the <Emphasis Type="Italic">MgII</Emphasis> index

Low fluxes of protons with energies 0.3–10 MeV were studied during 21–23 solar cycles as a function of the MgII index using the data of the instruments CPME, EIS (IMP8), and EPHIN (SOHO). It has been shown that a) during quiet time of solar activity the fluxes of protons (background protons) have a positive correlation with the MgII index value throughout the solar cycle, b) specific features of variations of the MgII index during the solar minima of 1986–1987 and 1996–1997 can be considered, as well as variations of background fluxes of low energy charged particles, to be manifestations of the 22-year magnetic cycle of the Sun, and c) periods of the lowest value of the MgII index are also characterized by the smaller values of the ratio of intensities of protons and helium nuclei than in other quiet periods. A hypothesis is put forward that acceleration in a multitude of weak solar flares is one of the sources of background fluxes of low energy particles in the interplanetary space.     

Estimates of disturbances of space vehicle orbits in the upper ionosphere prior to strong earthquakes

Estimates of drag characteristics of the space vehicles with orbit heights of 450–540 and 700–900 km before and after strong (with a magnitude M ≥ 6.5) crust earthquakes of 2000–2006 are presented. The method of estimation of seismic orbital effects is presented using as an example the small Mozhaets-4 spacecraft. Two weeks prior to earthquakes, variations in the drag of low-orbital spacecraft increase. 3–6 days prior to strong crust earthquakes with epicenters on the land, the drag of low-orbit spacecraft in the upper atmosphere increases. The effect of increased viscosity of the neutral component of the atmosphere at spacecraft heights 3–6 days prior to strong crust earthquakes is consistent with the results of studies of disturbances in the ionization density variations in the ionospheric F region prior to earthquakes. No anomalies are found in the day of the earthquake. In the future, it is proposed to use elements of space debris for diagnostics of seismic orbital effects and disturbances of the upper atmosphere.     

Observation of Terrestrial gamma-ray flashes in the RELEC space experiment on the <Emphasis Type="Italic">Vernov</Emphasis> satellite

The RELEС scientific payload of the Vernov satellite launched on July 8, 2014 includes the DRGE spectrometer of gamma-rays and electrons. This instrument comprises a set of scintillator phoswich-detectors, including four identical X-ray and gamma-ray detector with an energy range of 10 kev to 3 MeV with a total area of ~500 cm² directed to the atmosphere, as well as an electron spectrometer containing three mutually orthogonal detector units with a geometric factor of ~2 cm² sr. The aim of a space experiment with the DRGE instrument is the study of fast phenomena, in particular Terrestrial gamma-ray flashes (TGF) and magnetospheric electron precipitation. In this regard, the instrument provides the transmission of both monitoring data with a time resolution of 1 s, and data in the event-by-event mode, with a recording of the time of detection of each gamma quantum or electron to an accuracy of ~15 μs. This makes it possible to not only conduct a detailed analysis of the variability in the gamma-ray range, but also compare the time profiles with the results of measurements with other RELEC instruments (the detector of optical and ultraviolet flares, radio-frequency and low-frequency analyzers of electromagnetic field parameters), as well as with the data of ground-based facility for thunderstorm activity. This paper presents the first catalog of Terrestrial gamma-ray flashes. The criterion for selecting flashes required in order to detect no less than 5 hard quanta in 1 ms by at least two independent detectors. The TGFs included in the catalog have a typical duration of ~400 μs, during which 10–40 gamma-ray quanta were detected. The time profiles, spectral parameters, and geographic position, as well as a result of a comparison with the output data of other Vernov instruments, are presented for each of candidates. The candidate for Terrestrial gamma-ray flashes detected in the near-polar region over Antarctica is discussed.     

variations of the atmospheric chemical composition in the earths’s polar regions after solar proton flare on July 14, 2000 (photochemical simulation)

Altitude—temporal cross-sections q(z, t) of atmospheric ionization rates by solar protons above the polar regions were calculated using the GOES-10 satellite data on solar proton fluxes for the period of solar proton flare (SPF) on July 14, 2000. The values of q(z, t) were used further in calculations of variations of the atmospheric chemical composition during the flare in the northern and southern polar regions (70°N and 70°S) by two different 1D photochemical models of the atmosphere (neutral and charged components). The calculation results have shown considerable variation of the ozone content after SPF: a decrease of [O3] was about 80% at altitudes of 65–75 km above northern and 25% in the layer of 55–65 km above the southern polar region. Such decrease of the ozone content is a result of reactions with [NO] and [OH] whose concentrations have grown substantially during SPF. According to calculations, the increase of electron concentration during SPF has reached 3–4 orders of magnitude at altitudes of 50–80 km. A comparison of the calculation results with the observational data on [NO], [NO2], and [O3] from the UARS and HALOE satellites for 70°N have shown a good qualitative correspondence, however, for variations of nitric oxides there are quantitative discrepancies.     

Investigation of oxygen O2(a1Δg) emission on the nightside of Venus: Nadir data of the VIRTIS-M experiment of the Venus Express mission

The paper is devoted to studies of the oxygen 1.27 μm emission on the Venus nightside using nadir measurements with the imaging spectrometer VIRTIS. A map of the emission distribution in coordinates latitude-local time is drawn for the southern hemisphere, equatorial region, and low latitudes of the northern hemisphere on the basis of observations in the period from June 2006 to January 2008 (more than 600 runs). As it has been noted before, strong spatial and time variations of the emission were observed. Two maxima of the emission are found: the first one (expected) is observed near the antisolar point, and the second one (near 23:00 LT) is seen at latitudes of 30°–60° in the southern hemisphere. The average value of the emission intensity measured according to the nadir data is 1.0 ± 0.4 MR. The emission with the intensity exceeding the average one by a factor of 2–3 was detected at different times almost over the entire nightside of the southern hemisphere.     

Sunspot oscillations as derived from the <Emphasis Type="Italic">SOHO</Emphasis>/MDI magnetograms

As a result of processing long (up to 144 h) series of sunspot magnetograms obtained on the SOHO (Solar and Heliospheric Observatory) spacecraft with the MDI (Michelson Doppler Imager) instrument it is shown that the mode with a period of 800–1300 min is a limiting low-frequency oscillation mode of the magnetic field of a sunspot as a whole. Its period is essentially and nonlinearly depends on the sunspot magnetic field strength. In addition to this mode, higher harmonics are also revealed in the sunspot oscillation spectra in the bands 40–45, 60–80, 135–170, 220–250, and 480–520 min. The oscillation power in these bands monotonically and rapidly decreases with increasing frequency, which is characteristic for overtones arising due to the nonlinear nature of oscillations. The limiting oscillation mode stably exists in sunspots for 1.5–2 days, which coincides with the average lifetime of a supergranular cell. The mode with the period of 35–48 h observed in the power spectrum is not an eigen mode of sunspots, because its period is independent of its magnetic field strength. Probably, it occurs as a quasiperiod of an external exciting force caused by disturbances from supergranular cells surrounding the sunspot.     

Acceleration and losses of energetic protons and electrons during magnetic storm on August 30–31, 2004

Variations of particle fluxes during a moderate magnetic storm on August 30–31, 2004 are analyzed in this paper using measurements on low-orbit polar satellites CORONAS-F and SERVIS-1. The Earth’s radiation belts were filled at this time by enhanced flux of energetic particles accelerated a month ago during magnetic storms on July 23–27. The analysis has shown that even during a moderate magnetic storm a set of several adiabatic and non-adiabatic processes is observed, which leads to acceleration or release of particles and acts selectively depending on the energy range and charge of particles.     

Quantitative characteristics of long-term changes in parameters of the upper atmosphere of the earth over the 1966–1992 period

On the basis of the long series of mass-spectrometer measurements conducted in rocket experiments during 1966–1992 period, long-term changes in the structural parameters of the upper atmosphere within the 100–160 km height interval at equatorial, middle, and high latitudes of the Northern Hemisphere of the Earth are quantitatively estimated. At all latitudes statistically significant negative trends are revealed in the turbopause height, temperature of the neutral atmosphere, and atomic oxygen concentration. Since the contribution to the obtained quantitative estimates of the trends caused by long-term solar-induced factors does not exceed 15–20%, a conclusion is drawn on the anthropogenic nature of the changes having occurred in the upper atmosphere.     

Contribution of solar cosmic rays to the formation of the Earth’s proton radiation belt

The significance of the contribution of solar protons to fluxes of trapped radiation in the Earth’s outer radiation belt (L > 2) is estimated for various phases of solar activity. In periods of high solar activity, proton fluxes with the energy 1–5 MeV at L = 2–3 for the bulk of time have SCR as a source, during a minimum of solar activity, trapped proton fluxes are determined by the conventional diffusive mechanism under the action of sudden IMF impulses.     

Relative occurrence rate and geoeffectiveness of large-scale types of the solar wind

We investigate the relative occurrence rate for various types of the solar wind and their geoeffectiveness for magnetic storms with Dst < —50 nT. Both integrated effect for the entire time 1976–2000 and variations during this period of 2.5 cycles of solar activity are studied As raw data for the analysis we have used the catalog of large-scale types of the solar wind for the period 1976-2000 (see ftp://ftp.iki.rssi.ru/omni/) created by us with the use of the OMNI database (http://omni.web.gsgc.nasa.gov) [1] and described in detail in [2]. The average annual numbers of different type of events are as follows: 124 ±81 for the heliospheric current sheet (HCS), 8 ±6 for magnetic clouds (MC), 99 ±38 for Ejecta, 46 ±19 for Sheath before Ejecta, 6 ±5 for Sheath before MC, and 63 ±15 for CIR. The measurements that allowed one to determine a source in the solar wind were available only for 58% of moderate and strong magnetic storms (with index Dst < —50 nT) during the period 1976–2000. Magnetic clouds (MC) are shown to be the most geoeffective (~61%). The CIR events and Ejecta with Sheath region are three times less geoeffective (~20–21 %). Variations of occurrence rate and geoeffectiveness of various types of the solar wind in the solar cycle are discussed.     

Flux and isotopic composition of helium in the ancient solar wind

The isotopic composition and concentrations of helium are investigated in 9 samples taken from different depths of a soil column delivered by the Luna-24 mission. It is demonstrated that, with allowance made for random errors, the isotopic composition of helium remains invariable. The concentrations of helium are subject to considerable variations, the increases and decreases relative to the average value reaching a factor of 1.5–2. Assuming that the full length of the soil column was formed due to long-term accumulation of lunar clastic rocks (regolith), based on measurements of cosmogenic isotopes, a method of determining the rate of regolith accumulation has been developed, as well as a method of determining the age of the column soil samples. It is found that the rate of regolith accumulation is variable, and it changes over the column length within the limits (0.2–0.8 cm)/10⁶ years. The range of the time for formation of the investigated part of the column is 100–600 million years. The observed decreases of concentration (at 250 and 600 million years) can be associated with both solar and lunar processes. In particular, a possibility of diffusion losses of helium due to the mechanism of jump-like diffusion is discussed, and diffusion parameters are found. A comparison of time periods of the observed variations in the solar wind with paleontological epochs and periods is made.     

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. Original Russian Text ? V.A. Sadovnichy, M.I. Panasyuk, S.Yu. Bobrovnikov, N.N. Vedenkin, N.A. Vlasova, G.K. Garipov, O.R. Grigorian, T.A. Ivanova, V.V. Kalegaev, P.A. Klimov, A.S. Kovtyukh, S.A. Krasotkin, N.V. Kuznetsov, S.N. Kuznetsov, E.A. Muravyeva, I.N. Myagkova, N.N. Pavlov, R.A. Nymmik, V.L. Petrov, M.V. Podzolko, V.V. Radchenko, S.Ya. Reisman, I.A. Rubinshtein, M.O. Riazantseva, E.A. Sigaeva, E.N. Sosnovets, L.I. Starostin, A.V. Sukhanov, V.I. Tulupov, B.A. Khrenov, V.M. Shakhparonov, V.N. Sheveleva, A.V. Shirokov, I.V. Yashin, V.V. Markelov, N.N. Ivanov, V.N. Blinov, O.Yu. Sedykh, V.P. Pinigin, A.P. Papkov, E.S. Levin, V.M. Samkov, N.N. Ignatiev, V.S. Yamnikol, 2007, published in Kosmicheskie Issledovaniya, 2007, vol. 45, No. 4, pp. 291–305.     

Space-time structure of ion-cyclotron waves in the topside ionosphere as observed onboard the <Emphasis Type="Italic">ST</Emphasis>-<Emphasis Type="Italic">5</Emphasis> satellites

Results of observations of ion-cyclotron (IC) waves onboard the ST-5 satellites in the topside ionosphere (heights from a few hundred up to thousands of km) are presented. In this project, three identical micro-satellites were located during three months in 2006 in almost identical orbits with distances between them from first thousands to hundreds of km. All ion-cyclotron wave packets detected by two-three probes were observed at crossing one and the same latitude, which manifests their narrow localization in latitude with a characteristic scale from the first tens to 100 km. In no event IC waves were recorded with comparable amplitudes by all three satellites. At the same time, in the case of ST-5 flight near the ground-based induction magnetometer, a long emission in the same frequency range on the ground corresponded to a burst of IC waves in the topside ionosphere. This can indicate to the fact that an IC instability develops not continuously, but in the pulsing regime with a characteristic time of up to ∼10 min. A change in the rotation direction when a satellite crosses the wave structure is a characteristic feature of the polarization structure of registered transverse waves. The detected effects are discussed from the point of view of the existing models of generation and waveguide propagation of IC waves.     

Some features of solar cosmic ray penetration into the Earth’s magnetosphere

We compared fluxes of the 1–100 MeV solar energetic particles (SEP) measured in the interplanetary medium (ACE) and in the magnetosphere (Universitetsky-Tatiana, POES—in polar caps, and GOES-11—at geosynchronous orbit) during several SEP events of 2005–2006. Peak intensities of the SEP fluxes inside and outside the magnetosphere were compared for each event. It is shown that observed inside-outside difference depends mainly on direction of interplanetary magnetic field (IMF), on degree of the SEP anisotropy (pitch-angle distribution) in IMF, and on distance of the dayside magnetopause from the Earth.     

Statistical study of interplanetary condition effect on geomagnetic storms: 2. Variations of parameters

We investigate the behavior of mean values of the solar wind’s and interplanetary magnetic field’s (IMF) parameters and their absolute and relative variations during the magnetic storms generated by various types of the solar wind. In this paper, which is a continuation of paper [1], we, on the basis of the OMNI data archive for the period of 1976–2000, have analyzed 798 geomagnetic storms with D _st ≤ −50 nT and their interplanetary sources: corotating interaction regions CIR, compression regions Sheath before the interplanetary CMEs; magnetic clouds MC; “Pistons” Ejecta, and an uncertain type of a source. For the analysis the double superposed epoch analysis method was used, in which the instants of the magnetic storm onset and the minimum of the D _st index were taken as reference times. It is shown that the set of interplanetary sources of magnetic storms can be sub-divided into two basic groups according to their slowly and fast varying characteristics: (1) ICME (MC and Ejecta) and (2) CIR and Sheath. The mean values, the absolute and relative variations in MC and Ejecta for all parameters appeared to be either mean or lower than the mean value (the mean values of the electric field E _y and of the B _z component of IMF are higher in absolute value), while in CIR and Sheath they are higher than the mean value. High values of the relative density variation sN/〈N〉 are observed in MC. At the same time, the high values for relative variations of the velocity, B _z component, and IMF magnitude are observed in Sheath and CIR. No noticeable distinctions in the relationships between considered parameters for moderate and strong magnetic storms were observed.     

Variation of the trapped proton flux in the inner radiation belt of the earth as a function of solar activity

Fluxes of trapped protons with energies above 70 MeV measured onboard the NOAA-15 satellite during the 23rd solar activity cycle (from 1999 to 2006) are analyzed. Comparing to similar experimental data obtained for 1976–1996, regularities of changes in the proton flux at low drift shells (L = 1.14–1.20) of the Earths’s radiation belt caused by changes in the solar activity are discussed.     

High-energy gamma radiation of solar flares as an indicator of acceleration of energetic protons

Using the SONG detector onboard the CORONAS-F satellite, gamma-ray emission of high energies (>100 MeV) was recorded during four solar flares. In the sequential spectra of gamma rays the peculiarity caused by generation and decay of neutral pions was isolated, which made it possible to determine with a high accuracy the moments of appearance in the solar atmosphere of protons accelerated up to energies above 300 MeV.     

Development of auroral electrojets and low-latitude geomagnetic disturbances during strong magnetic storms on November 7–11, 2004

The influence of auroral electojets and solar wind parameters on variations in low-latitude geomagnetic disturbances and D _st during strong magnetic storms on November 7–8, 2004 with D _st ≈ −380 nT and on November 9–10, 2004 with D _st ≈ −300 nT is studied on the basis of global geomagnetic observations. It is found that the impulsive variations of the western electrojet intensity with a duration of Δt ≈ 1–2 h (probably, substorm disturbances) lead to positive low-latitude disturbances of ΔH at Φ′ ≈ 10°–30° and to disturbances of the same durations with an amplitude +ΔH ∼ 30–100 nT at latitudes of the polar cap (Φ′ ≈ 75°–80°). More durable (with Δt ≥ 10 h) convection electrojets whose centers are shifted to latitudes of ∼50°–55° in the process of storm development are the main cause of the increase in negative values of ΔH at low latitudes and D _st . It is shown that meridional dynamics of position of the center of electrojets and the equatorial boundary of the auroral oval is governed by variations (increase or decrease) in the intensity of negative values of the IMF B _z component. It is assumed that in these storms the intensification of the magnetospheric partially ring current closes the circuit to the ionosphere with the help of field-aligned currents at the equatorial boundary of the auroral oval is the main cause of the magnetic field depression at low latitudes.     

Investigation of Long-Wave Radio Bursts from Interball-1 Satellite Observations

Long-wave radio bursts recorded on the Interball-1 satellite in the frequency band 100–1500 kHz are analyzed. The events distinguished by large amplitude radio emission fluxes were selected. These bursts were identified with powerful solar flares, during which time fluxes of hard X-ray radiation, meter-wave radio bursts (types II and IV), and coronal transients were observed. Temporal profiles of the bursts are characterized by a quick drift in frequency and are typical for bursts of III and SA types. The instant of long-wave radio burst generation seems to correspond to the expansion phase of a flare.