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.     

Peculiarities of long-wave radio bursts from solar flares preceding strong geomagnetic storms

Radio bursts in the frequency range of 100–1500 kHz, recorded in 1997–2000 on the INTERBALL-1 satellite during the solar flares preceding the strong geomagnetic storms with D _st < ?100 nT, are analyzed in this paper. The observed long-wave III-type radio bursts of solar origin at frequencies of 1460 and 780 kHz were characterized by large values of the flux S _f = 10^?15 ?10^?17 W/m² Hz and duration longer than 10 min. The rapid frequency drift of a modulated radio burst continued up to a frequency of 250 kHz, which testified that the exciting agent (a beam of energetic electrons) propagated from the Sun to the Earth. All such flares were characterized by the appearance of halo coronal mass ejections, observed by the LASCO/SOHO, and by the presence of a southward B_z-component of the IMF, measured on the ACE and WIND spacecraft. In addition, shortly after radio bursts, the INTERBALL-1 satellite has recorded the fluxes of energetic electrons with E > 40 keV.     

Hectometer radio bursts and energetic electrons during solar flares according to observations onboard the Interball-1 satellite

Radio bursts in the frequency range 100–1500 kHz and fluxes of energetic electrons with energies of 20–450 keV recorded onboard the Interball-1 satellite during prominent chromospheric flares on the Sun are studied. The time of propagation of the electrons to the Earth is estimated using the method of comparison of the moments of the beginning of radio emission generation during the explosive phase of the flare and the arrival of the accelerated electrons to the Earth.     

Bursts of geomagnetic pulsations in the frequency range 0.2-5 Hz excited by large changes of the solar wind pressure

We present the results of studying the magnetospheres’s response to sharp changes of the solar wind flow (pressure) based on observations of variations of the ions flux of the solar wind onboard the Inreball-1 satellite and of geomagnetic pulsations (the data of two mid-latitude observatories and one auroral observatory are used). It is demonstrated that, when changes of flow runs into the magnetosphere, in some cases short (duration ~ < 5 min) bursts of geomagnetic pulsations are excited in the frequency range Δf~ 0.2–5 Hz. The bursts of two types are observed: noise bursts without frequency changes and wide-band ones with changing frequency during the burst. A comparison is made of various properties of these bursts generated by pressure changes at constant velocity of the solar wind and by pressure changes on the fronts of interplanetary shock waves at different directions of the vertical component of the interplanetary magnetic field.     

Acceleration of solar cosmic rays and the fine spectral structure of type II radio bursts

On the basis of data, obtained by means of the ground-based solar service RSTN (Radio Solar Telescope Network) and the geostationary satellite system GOES, the relationship between the solar cosmic rays (SCR) intensity I _p with the proton energy E _p > 1 MeV and parameters of meter-decameter type II radio bursts in the frequency range of 25–180 MHz is studied. The process of proton acceleration by shock waves was characterized by the frequency drift velocity of radio bursts V _mII and the relative difference between radio emission frequencies at the first two harmonics b. It is shown that the coefficient of correlation between I _p and b increases with E _p growing from 0.40 to 0.70, while a similar coefficient between I _p and V _mII does not exceed 0.30. Indications in favor of the two-stage SCR acceleration model are obtained.     

Observations of the auroral hectometric radio emission onboard the <Emphasis Type="Italic">INTERBALL-1</Emphasis> satellite

The results of five-year (1995–2000) continuous observations of the auroral radio emission (ARE) in the hectometric wavelength range on the high-apogee INTERBALL-1 satellite are presented. Short intense bursts of the auroral hectometric radio emission (AHR) were observed at frequencies of 1463 and 1501 kHz. The bursts were observed predominantly at times when the terrestrial magnetosphere was undisturbed (in the quiet Sun period), and their number decreased rapidly with increasing solar activity. The bursts demonstrated seasonal dependence in the Northern and Southern hemispheres (dominating in the autumn-winter period). Their appearance probably depends on the observation time (UT). A qualitative explanation of the AHR peculiarities is given.     

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.     

Connection between the discrete auroral structures drifting equatorward during the substorm expansion phase and the energetic particle injections at the geostationary orbit

The formation of an auroral bulge with a bright dynamical arc at its polar boundary is one of the main manifestations of the magnetospheric substorm expansion phase at the ionospheric level. At the same time, the region of discrete aurora broadens not only polewards but equatorwards as well. The discrete forms of auroras moving equatorwards form a dynamical equatorial boundary of the auroral bulge shifting together with them. The paper presents a spatial-time comparison of the drifting discrete auroras to the injection of energetic particles at the geostationary orbit. It is shown that bursts in the fluxes of energetic particles at the LANL geostationary satellites located in the same sector of MLT correspond to the majority of drifting discrete auroral structures observed by the all-sky camera. In the cases when the bursts in the fluxes are absent, the minimum latitude reached by the auroral structures at the equatorward drift is higher than the ionospheric projection of the geostationary orbit. A possible relation of the drifting discrete auroras to the plasma stream jets in the plasma sheet is discussed.     

Large and Fast Variations of Parameters in the Magnetosheath: 3. Amplitudes and Transverse Profiles of Low and High Frequency Variations of the Plasma and Magnetic Field

We present the results of experimental studies of high frequency (with periods of seconds and tens of seconds) and low frequency (with periods of minutes and tens of minutes) large variations of the ion flux and magnetic field magnitude in the magnetosheath. It is shown that, on average, the relative amplitudes of these variations are approximately two times higher than similar values characteristic for the undisturbed solar wind. The averaged spatial profile of these values and their variations across the magnetosheath is obtained, as are the dependencies of normalized plasma fluxes and their variations on the place of entrance of a given plasma element into the magnetosheath. Using one particular example, a good coincidence between the time profiles of ion fluxes measured aboard two spacecraft separated by a distance of 10R _E along the magnetosheath is demonstrated.     

Theory of type III radio bursts in the interplanetary space: I. Derivation of permittivity tensor for the system consisting of electron beam and solar wind plasma

The tensor of permittivity for the system “electron beam - plasma of the interplanetary space” is derived in the approximation of geometrical optics. The problem is one-dimensional; all parameters such as density of the beam and of the solar wind plasma, and the induction of the interplanetary magnetic field are assumed to be dependent only on the distance to the Sun. The beam is generated by an active region during a solar flare, and it is a source of radio bursts of type III in the interplanetary space. The tensor of permittivity was obtained to close field equations by a material equation. On the basis of these equations it becomes possible to study theoretically the amplitude-frequency characteristics of the radio bursts as disturbances of the above-described beam-plasma system.     

A method to ensure energy security of satellite communication systems

A method is substantiated to ensure energy security for the satellite communication systems (SCS) at a close position of the radio interception receiver. This is done by lowering the carrier frequency down to f ₀ = 60…80 MHz and by applying spaced measurements with n ≥ 4 receiving antennas.     

Quasiperiodic oscillations of the sub-mHz band in near-sun plasma according to the coherent radio occultation data

In 2013 and 2015, investigations of the internal solar wind were carried out using the method of two-frequency radio sounding by signals from the Mars Express European spacecraft. The values of the S- and X-bands’ frequency and the differential frequency were registered with a sampling rate of 1s at the American and European networks of ground-based tracking stations. The spatial distribution of the frequency fluctuation’s level has been studied. It has been shown that the intensity of frequency fluctuation considerably decreases at high heliolatitudes. In some radio sounding sessions, quasiperiodic oscillations of sub-mHz band have been observed in the temporal spectra of frequency fluctuations; they are supposed to be associated with the density inhomogeneities, the sizes of which are close to the turbulence outer scale.     

Observations of corotating solar wind structures at radio sounding by signals of the <Emphasis Type="Italic">Rosetta</Emphasis> and <Emphasis Type="Italic">Mars Express</Emphasis> spacecraft

In the implementation of the space projects Rosetta and Mars Express, a large-scale series of experiments has been carried out on radio sounding circumsolar plasma by decimeter (S-band) and centimeter (X-band) signals of the Rosetta comet probe (from October 3 to October 31, 2010) and the Mars Express satellite of Mars (from December 25, 2010 to March 27, 2011). It was found that in the phase of ingress the spacecraft behind the Sun, the intensity of the frequency fluctuations increases in accordance with a power function whose argument is the solar offset distance of radio ray path, and when the spacecraft is removed from the Sun (the egress phase), frequency fluctuations are reduced. Periodic strong increases in the fluctuation level, exceeding by a factor of 3–12 the background values of this value determined by the regular radial dependences, are imposed on the regular dependences. It was found that increasing the fluctuations of radio waves alternates with the periodicity m × T or n × T, where m = 1/2, n = 1, аnd T is the synodic period of the Sun’s rotation (T ≈ 27 days). It was shown that the corotating structures associated with the interaction regions of different speed fluxes are formed in the area of solar wind acceleration and at distances of 6–20 solar radii already have a quasi-stationary character.     

Characteristics of thermal ion outflows in the polar cap according to data of the <Emphasis Type="Italic">Interball-2</Emphasis> satellite

Characteristics of polar wind fluxes at a height of ∼20000 km measured by the Hyperboloid mass-spectrometer installed onboard the Interball-2 satellite are presented in the paper. The characteristics are presented for the upwelling flows of ionospheric ions H⁺, He⁺, and O⁺ from the sunlit polar cap in the period of solar activity minimum. Orbit segments with minimal precipitation of magnetospheric ions and electrons were preliminarily selected, and the measurements where the fluxes of ions coming from the cusp/cleft were excluded as carefully as possible. Thus, the densities, field-aligned velocities, and temperatures of ions in the regions where fluxes of polar wind could be detected with the maximal probability degree are presented in the paper. It is found that cases when only H⁺ ions are reaching the detector are with high probability the polar wind outflows. Their characteristics agree well with the Tube-7 hydrodynamic model and are as follows: n ≈ 1.5 cm⁻³, V _∥ ∼ 21 km/s; T _∥ = 3500 K, and T _⊥ = 2000 K. In cases when He⁺ and O⁺ ions are also detected, the temperatures are substantially higher than the model ones, and the measured field-aligned velocities of O⁺ fluxes are several times higher than the model ones. Moreover, it was revealed that the polar wind outflows are predominantly observed in the polar cap regions where the polar rain fluxes are very small.     

Empirical model of pitch-angle distributions of trapped protons on the inner boundary of the Earth’s radiation belt

We have made a generalization of experimental data on the fluxes of trapped protons that were detected by various instruments on three low-orbit satellites (NOAA-17, Universitetskii-Tatiana, and CORONAS-F) during April of 2005. Based on these data, a new quantitative model is suggested to describe the fluxes of trapped protons. It allows one, using analytical expressions, to predict the fluxes of protons with energy from 30 keV to 140 MeV under quiet geomagnetic conditions in the period close to the solar activity minimum at drift shells L = 1.14–1.4. The suggested model establishes differential directional fluxes of protons as a function of pitchangle on the geomagnetic equator and takes into account the anisotropy of trapped particles on the lower boundary of the Earth’s radiation belt.     

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.     

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.     

Electrostatic Noise Spectrum at the Electron Cyclotron Frequency and Electromagnetic Emission in the Inhomogeneous Plasma of the Topside Ionosphere

Measurements of the wave emission of the topside ionosphere made onboard the APEX satellite using the electric component of the wave field in the 0.1–10 MHz frequency band are presented. At middle latitudes a wave intensity decrease was observed in the broad-band spectrum of the electrostatic noise at the electron cyclotron frequency. It is shown that a break in the spectrum of electrostatic modes at the electron cyclotron frequency (the absence of the plasma eigen-frequencies) may be a cause of the observed effect. The increase of the intensity at the electron cyclotron frequency in the ionospheric trough and at latitudes above the trough region as compared to middle latitudes may be explained by the capture by plasma irregularities of the electromagnetic emission of the auroral electron fluxes.__________Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 3, 2005, pp. 201–208.Original Russian Text Copyright © 2005 by Izhovkina, Prutensky, Pulinets, Kiraga, Klos, Rothkael.