Near-Equatorial Electrons as Measured onboard the MirSpace Station

Some results of studying the electrons with energies of tens to hundreds of keV at the low and near- equatorial geomagnetic latitudes by using the instruments Sprut-V and Ryabina-2 onboard the Mirspace station in 1991 are presented. It is found that at L< 1.2 the enhanced electron fluxes are sporadically detected, being localized within three longitudinal intervals, 180° W–0°–15° E, 90°– 120° E, and 160° E–180°–135° W. The most intense electron fluxes are observed at the lower edge of the near-equatorial boundary of the inner radiation belt on longitudes of the South Atlantic Anomaly between 14 and 20 h MLT. The occurrence of electron bursts does not depend on the geomagnetic disturbance level. A hardening of the electron spectra is observed near the geomagnetic equator. At L< 1.1, the more energetic particles are located closer to the geomagnetic equator. The results are compared with the data on the low-frequency waves and fields at low and near-equatorial latitudes obtained by the Ariel-4and San Marco Dsatellites, as well as by the spacecraft and ground-based observations of the thunderstorm global distribution. The thunderstorms are considered as a possible source of electron production near the geomagnetic equator.     

Observation of the Near Plasma Sheet,Ring Current,and Energetic Electrons from Radiation Belts at a Geosynchronous Orbit,March 11–25, 1992

The dynamics of near plasma sheet electrons and ions (E 0.1–12.4 keV), ring current protons (E _i 41–133 keV), and energetic electrons from the Earth's radiation belts (E _e 97–1010 keV) is considered using the data from the Gorizont-34and Gorizont-35geosynchronous satellites from March 11–25, 1992. Peculiarities of this period are a long (more than 4 days) interval of the northward interplanetary magnetic field (B _z> 0) and a high-speed stream of the solar wind with an enhanced particle density. The SC and compression of the magnetosphere to the geosynchronous orbit (GMC) preceded this interval. Under quiet and moderately disturbed geomagnetic conditions and under a prolonged northward interplanetary magnetic field, we observed a significant decrease of fluxes and softening of spectra of the electron component of plasma in the energy ranges of 0.1–12.4 keV and 97–1010 keV, and of the ion component of plasma at energies of 0.1–4 keV, while the intensity of 5–12.4 keV ion fluxes increases by about one order of magnitude. The peculiarities of distributions of energetic particle fluxes observed in the period under consideration can be associated with significant variations of the convection conditions and a decreased or fully suppressed injection of energetic electrons into the geosynchronous orbit region.     

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.     

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.     

Features of wave excitation of the electrostatic ion cyclotron type in the auroral ionosphere

Broadband electrostatic noise in the auroral ionosphere can be identified as a version of waves of an electrostatic ion cyclotron type, excited by plasma instability resulting from an inhomogeneous distribution of wave energy density. Broadband waves are generated due to both electric field inhomogeneities and plasma density inhomogeneities. The effect of the form of the distribution of electric field and plasma density inhomogeneities on the excitation of instabilities is studied. Also there is shown the role of the characteristic scale of inhomogeneities in the generation of electrostatic ion cyclotron waves due to the development of instability of this kind. The study of these issues, which are important for understanding the processes in the auroral region, is the subject of this paper. The work presents also a comparison of numerical results obtained using both satellite data and model approximations.     

Gravitationally Perturbed Elastic Waves in the Hidden Ocean of Europa

The frequency spectrum of joint hydro-elastic vibrations of the ice surface of the ocean and liquid is analyzed taking into account the proper gravity field of Europa, one of Jupiter’s moons. It is shown how the methods developed for analysis of the vibration stability of earth buildings are used to study seismic properties of the natural Jupiter satellite Europa. Numerical estimates show that when studying the electromagnetic effects and seismic properties of this satellite one should take into account hydro-elastic characteristics due to the closeness of the corresponding frequency spectra.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 209–214.Original Russian Text Copyright © 2005 by Dokuchaev.     

Sources of Plasma Troughs in the Midlatitude and Subauroral Topside Ionosphere

The data of observations of plasma density in the large-scale ionospheric trough by the ion trap onboard the Kosmos-900 satellite on April 15, 1977, are presented. They enable one to understand both the general configuration and the fine details of the trough. There are sharp gradients of density (especially, in the subtroughs) superimposed on the less prominent variations of density in the main trough, which are characteristic of the average pattern of the trough. It was demonstrated that one of the possible mechanisms of forming the troughs(i.e., plasma cavities) is the electrostatic instability of plasma in the topside ionosphere.     

Observations of the Auroral Kilometric Radiation onboard the Interball-1 satellite in 1995–1997

Results of two-year (August 1995–July 1997) continuous observations of the auroral kilometric radiation (AKR) in the AKR-X experiment on board the high-apogee Interball-1 satellite are presented. Observations were carried out in the minimum of solar activity in a frequency range of 100–1500 kHz. The most effective detections of AKR occurred near the maximum of its spectrum at a frequency of 252 kHz and also at a frequency of 500 kHz. The data obtained made it possible to study in more detail the character of AKR global directivity, its frequency dependence, and some other parameters of the emission. These data are interpreted qualitatively in the context of the emission mechanism caused by cyclotron maser instability.     

Plasma Cavern Structure in the Ionosphere F Layer at the Geomagnetic Equator according to the Kosmos 900 Satellite Data

The observational data on the plasma density and electron component temperature in the region of the geomagnetic equator in the ionosphere F layer are presented. The measurements have been conducted by scientific equipment onboard the Kosmos 900 satellite (on August 7, 1979). A plasma cavern was observed in this region. It is shown that the formation of the cavern may be related to the attenuation of the electrostatic plasma instability and plasma vortices in the upper ionosphere at the geomagnetic equator.     

Time and energy characteristics of UV flashes in the atmosphere: Data of the <Emphasis Type="Italic">Universitetsky-Tatiana</Emphasis> satellite

Using a detector of near ultra-violet (UV) emission (wavelength range 300–400 nm) [1] onboard the Universitetsky-Tatiana satellite with an orbit height of 950 km and inclination of 81° we have detected and studied short UV flashes [2–5]. In this paper the observed UV flashes are classified according to the type of their time profiles, and the times of emission intensity rise and decay are investigated in every flash. Using the data on time profiles it turned out to be possible to estimate the flash energy in the atmosphere even in case of saturation of a signal measuring channel at the maximum of emission. The energy spectrum of observed flashes is estimated. Time and energy characteristics of the flashes are important for choosing a model of development of electric discharges in the upper atmosphere that are responsible for observed emission.     

Low Altitude Cusp–Cleft Region Signatures of Strong Geomagnetic Disturbances

The polar cusp being a region of the free access of the solar wind into the inner magnetosphere is also the site of turbulent plasma flow. The cusp area at low altitudes acts like a focus of a variety type of instability and disturbances from different regions of the Earth. Daily f ₀ F2 frequencies are discussed regarding the cusp position. The high time resolution wave measurements together with electron and ion energetic spectra measurements registered on the board the Freja satellite and Magion-3 and the electron density at the peak of f ₀ F2 layers collected from ground-based ionosonde measurements were used to study the response of ionospheric plasma within the cusp–cleft region to the strong geomagnetic storm. In this paper we present the response of the ionospheric plasma to the disturbed conditions seen in the topside wave measurements and in the ionospheric characteristics maps obtained from the ground-based VI network. The need of the cusp feature model for radio communication purposes is advocated.     

Shock–Acoustic Waves Generated during Rocket Launches and Earthquakes

Shock–acoustic waves generated during rocket launches and earthquakes are investigated by a method developed earlier for processing data from a global network of receivers of the GPS navigation system. Disturbances of the total electron content in the ionosphere accompanying the launches of the Proton, Soyuz, and Space Shuttle space vehicles from the Baikonur cosmodrome and Kennedy Space Center launch site in 1998–2000, as well as the earthquakes in Turkey on August 17 and November 12, 1999, were analyzed. It was shown that, regardless of the source type, the impulsive disturbance has the character of an N-wave with a period of 200–360 s and an amplitude exceeding background fluctuations under moderate geomagnetic conditions by a factor of 2–5 as a minimum. The elevation angle of the disturbance wave vector varies from 25° to 65°, and the phase velocity (900–1200 m/s) approaches the speed of sound at heights of the ionospheric F-region maximum. The source location corresponds to a segment of the booster trajectories at a distance of no less than 500–1000 km from the start position and to a flight altitude of no less than 100 km. In the case of earthquakes the source location approximately coincides with the epicenter.     

Statistical Correlation of the Rate of Failures on Geosynchronous Satellites with Fluxes of Energetic Electrons and Protons

A statistical comparison of failures on geosynchronous satellites in the maximum and during the decline of the 22nd solar cycle (1989–1994) with space weather parameters is carried out. A positive correlation of the rate of failures with the flux of relativistic electrons on the geosynchronous orbit and with the proton flux measured before the bow shock front is revealed. The significant positive correlation of the electron flux with the rate of failures is observed during the entire considered interval. The correlation coefficient varies in the solar activity cycle in coordination with the electron flux, and the maxima of the correlation coefficient are observed on the phase of decline of the cycle. A statistically significant positive correlation between the flux of protons with energy of more than 1 MeV and the rate of failures is revealed in the maximum of the solar cycle.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 186–193.Original Russian Text Copyright © 2005 by Romanova, Pilipenko, Yagova, Belov.     

A Study of Long-Wave Radio Bursts Observed in 2000 onboard the INTERBALL-1 Satellite

The bursts of long-wave radio emission in the 100–1500 kHz frequency band detected onboard the INTERBALL-1 satellite during strong chromosphere solar flares in 2000 are analyzed. The bursts exhibit large amplitude and duration. A comparison of the bursts with phenomena in the optical, x-ray, and radio bands is carried out.     

Electromagnetic Pulse in the Magnetosphere Generated by Impulsive Current near the Lower Boundary of the Ionosphere

A solution to the problem of current spreading is constructed in the case of relaxation of electric charges, which have arisen in the mesosphere for one reason or other. These currents penetrate into the conductive region with anisotropic conductivity of the D- and E-layers of the ionosphere, being transformed to a MHD-wave that propagates into the magnetosphere. Based on this solution, the form and spectrum of the generated MHD signal are calculated for Alfvenic and magnetosonic modes coming out to the ionosphere and magnetosphere. Electric charges and currents can arise, for example, in the space between a thunderstorm cloud and the ionosphere, or between the shock wave from a ground explosion and the ionosphere. Some signal parameters accepted in the model are close to those expected for high-altitude electric discharges of the Red Sprite type. The conditions are determined under which the Alfven impulse with an amplitude of up to 100 nT propagates in the magnetosphere above high-altitude discharge of this type. Such an impulse was recorded by the AUREOL-3 satellite after the ground explosion MASSA-1. Recently, this impulse was hypothesized to originate as a result of a high-altitude electric discharge. The hypothesis on a similar MHD pulse allows one to explain in a semiquantitative way the short burst of electron field-aligned acceleration observed by the DE-2 satellite over the Debbie hurricane. The high-altitude atmospheric discharge of this type can be a powerful, though short-time and local, source of electrons with kiloelectronvolt energies at low and middle latitudes. One could expect that such an effect causes a modified character of the so-called Trimpi-effect (a short-term disturbance of propagation of VLF waves in the ionosphere), and thus, it can be observable.     

INTERBALL-1 Observations of the Kilometric “Continuum” of the Earth's Magnetosphere

The electromagnetic radio-frequency emission of the inner region of the Earth's plasmasphere discovered recently by the GEOTAIL satellite [4] and referred to as the kilometric continuum was observed by the INTERBALL-1 satellite (1995–2000) in the 100–500 kHz band in the AKR-X experiment. During a period of low solar activity (1995–1997), this continuum was found leaving the inner plasmasphere at geocentric distances of 2–4R _E as isolated pencil-like (1°–6°) beams located in the magnetic equator plane. During a time of high solar activity (1999–2000), the occurrence of the emission was extremely rare (it was observed only at a considerable fall of this activity). If detected, at the same geocentric distances (2–4R _E) the continuum demonstrated a strongly variable and perturbed character, as well as a considerably larger extension of the beam over the geomagnetic latitude (10°–20° and more). In addition, quasi-periodic (QP) signals, similar to the observed QP emissions of Jupiter, were sometimes detected in this period. The probable nature of the observed features of the kilometric continuum is briefly discussed.     

Possible Origin of Ultralow-Frequency Whistlers

The sonographic analysis of records of ultralow-frequency emissions recorded by the induction magnetometer at the Mirnyi observatory (Antarctica) in 1981–1985 has revealed the presence of a special class of signals in the frequency band 0.25–5 Hz having a characteristic dispersion reminiscent of the dynamic spectra of LHR-whistlers observed in the VLF band. The ULF whistlers are observed, as a rule, at morning and evening hours of local time at moderate values of the K _p-index (0 < K _p < 4). The analysis of the frequency–time behavior of observed signals shows that the canalized propagation of short broadband pulses as magnetosonic waves in the layered medium, for example, in the magnetospheric current sheet can serve as a possible cause of the dispersion. Such sporadic phenomena on the magnetopause as microreconnections or FTE-events may be sources of these pulses.     

Radio Occultation Measurements of the Radio Wave Absorption and the Sulfuric Acid Vapor Content in the Atmosphere of Venus

The results of the determination of centimeter ( = 5 cm) radio waves absorption in the radio occultation experiments, carried out using the Venera-15and Venera-16spacecraft, are presented. The altitude distribution of the absorber substance is analyzed. The absorbing layer is shown to exist at altitudes of 64 to 58 km in the near-polar regions of the planet. At middle latitudes such an absorbing layer was not found. In the altitude range from 56 to 46 km the radio wave absorption by the sulfuric acid (H₂SO₄) vapor is observed. The content of the sulfuric acid vapor is shown to increase with decreasing altitude: in the mid-latitude region at altitudes of 56.7 and 53 km it equals 5 and 20 ppm, respectively, and at polar latitudes the same content of H₂SO₄vapor is observed at altitudes of 51.2 and 47 km, respectively. A comparison of these results with the data of radio wave absorption in the = 13 cm band, obtained in the Pioneer Venus Orbiterradio occultation experiments, leads to the conclusion that the obtained values of the sulfuric acid vapor content well agree in the regions of overlap of the data.     

An Empirical Model of the Radiation Belt of Helium Nuclei

Based on satellite data, we present the results of modeling the spatial and energy distributions of integral fluxes of He nuclei (α particles) with E > 1, 2, 4, and 7 MeV at L = 1.1–6.6 in a broad range of B/B ₀ (E is the kinetic energy of particles, L is the drift shell parameter, and B/B ₀ is the magnetic field ratio). Some ways of practically applying the model are considered. The results of calculation of α-particle fluxes for a circular orbit with a height of 300 km and an inclination of 50° are presented.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 4, 2005, pp. 243–247.Original Russian Text Copyright © 2005 by Getselev, Sosnovets, Kovtyukh, Dmitriev, Podzolko, Vlasova, Reizman.     

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.