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.     

Geomagnetic effect of launches and flights of large spacecraft

The results of observations of variations in the geomagnetic field that accompanied launches and flights of rockets of different types have been analyzed. The launches were performed in 2002–2010 from different space launch facilities of the world (237 events in total), and variations in the range of periods 1–1000 s were studied. Measurements were performed near the city of Kharkov (distance from the spaceports ranges from 1500 to 9500 km). Statistical analysis and spectral estimations have been made, and three groups of disturbances were revealed. Time delays and disturbance durations increased with increasing distance from spaceports. Typical periods were equal to 6 to 14 min, while amplitudes varied in the range 1–3 nT.     

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.     

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.     

Disturbance in the lower ionosphere that accompanied the reentry of the Chelyabinsk cosmic body

The paper describes quasi-periodic and aperiodic variations in the phase and amplitude of radio waves of LF and VLF ranges, which accompanied the flight and explosion of the Chelyabinsk meteoroid. Quasi-periodic variations in the phase have been explained by the generation of acoustic-gravity waves in the atmosphere, which modulate the electron density in the ionosphere and the phase of radio waves. Aperiodic variations in the phase and amplitude of radio waves are associated with an increase in the electron density in the lower ionosphere (at altitudes of 65–70 km). This increase was most likely caused by the interactions of subsystems in the Earth–atmosphere–ionosphere–magnetosphere system or, more correctly, by the precipitation of high-energy electrons from the magnetosphere into the lower ionosphere, which was stimulated by the flight and explosion of a cosmic body. According to the estimates, the density of the flux of electrons with energies of 100 KeV should be on the order of 106 m^–2 s^–1.     

Storm deviations of the geomagnetic trap core from dipole configuration deduced from data on relativistic electrons

Satellite data on the position of maximum L _m of the belt of relativistic electrons during strong storms, obtained at low altitudes (∼500 km) and at high altitudes (near the geomagnetic equator plane), are compared (L is the McIlwain parameter). Both at low and high altitudes the maximum of the storm belt of relativistic electrons is formed on the outer edge of the ring current. It is shown that the geomagnetic field can substantially deviate from dipole configuration not only at the geomagnetic trap periphery, but at its core as well (at L ∼ 2.5–3.5), and these deviations are nonlinear. Simultaneous measurements of the fluxes of relativistic electrons at low and high altitudes can serve for estimation of the real shape of magnetic field lines at L < 4 during geomagnetic disturbances.     

The Influence of artificial plasma irregularities on the propagation of VLF waves in the Earth’s magnetosphere

In the framework of the approximation of geometric optics, the peculiarities of VLF-wave propagation in the Earth’s ionosphere and magnetosphere during the creation of large-scale artificial plasma irregularities by heating facilities such as HAARP and “Sura” in the ionosphere are studied. For calculation of ray trajectories, the profile of the concentration and ion composition of plasma is taken by calculating the SAMI2 ionospheric model, which was modified to take the influence on the ionosphere of the HF emissions of heating facilities into account. As a result of the influence of the heating facilities on the ionosphere, a region could occur with an increased plasma concentration that is stretched out along the geomagnetic field (up to heights on the order of the Earth’s radius) with small dimensions across the field (～1°). The ray trajectories of waves that propagate from heights of about 100 km from different initial points in the region where such a disturbance has been created with different initial inclination angles of the wave normal are studied in this paper. Both lightning discharges and modulated HF heating of the ionosphere could be the sources of such waves. It is shown on the basis of the performed analysis that the presence of such disturbances in density can lead to a substantial changes in wave-propagation trajectories, in particular, to efficient channeling of VLF waves in the disturbance region and an increase in the interval of the initial propagation angles of waves, which can reach the ionosphere in the opposite hemisphere.     

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.     

Statistical study of interplanetary condition effect on geomagnetic storms

Based on the archive OMNI data for the period 1976–2000 an analysis has been made of 798 geomagnetic storms with D _st < −50 nT and their interplanetary sources-large-scale types of the solar wind: CIR (145 magnetic storms), Sheath (96), magnetic clouds MC (62), and Ejecta (161). The remaining 334 magnetic storms have no well-defined sources. For the analysis, we applied the double method of superposed epoch analysis in which the instants of the magnetic storm beginning and minimum of D _st index are taken as reference times. The well-known fact that, independent of the interplanetary source type, the magnetic storm begins in 1–2 h after a southward turn of the IMF (B _z < 0) and both the end of the main phase of a storm and the beginning of its recovery phase are observed in 1–2 h after disappearance of the southward component of the IMF is confirmed. Also confirmed is the result obtained previously that the most efficient generation of magnetic storms is observed for Sheath before MC. On the average parameters B _z and E _y slightly vary between the beginning and end of the main phase of storms (minimum of D _st and D _st ^* indices), while D _st and D _st ^* indices decrease monotonically proportionally to integral of B _z and E _y over time. Such a behavior of the indices indicates that the used double method of superposed epoch analysis can be successfully applied in order to study dynamics of the parameters on the main phase of magnetic storms having different duration.     

SAA域选划对天基探测卫星影响简析

通过仿真计算南大西洋异常区(SAA)高能粒子的通量与能量,分析不同通量阈值与能量阈值对SAA空间分布的影响,并以科学实验卫星为研究对象,对其历经SAA的时间百分比进行连续24 h和6个月的统计,获得了SAA对卫星常规运行的工作时间影响。结果表明:在50 MeV能量阈值条件下,500 cm~(-2)?s~(-1)较100 cm~(-2)?s~(-1)通量阈值对SAA空间分布的影响范围在纬度上相差约23.35%,经度上相差约27.06%,历经SAA时间上缩短约48.0%;在100 cm~(-2)?s~(-1)通量阈值条件下,150 MeV较50 MeV能量阈值对SAA空间分布的影响范围在纬度上相差约13.86%,经度上相差约17.29%,历经SAA时间上缩短约31.7%。     

Sporadic structures and small-scale irregularity in the nighttime polar ionosphere in the period of high solar activity according to the data of radio occultation measurements on satellite-to-satellite paths

Results of the analysis of 327 sessions of radio occultation on satellite-to-satellite paths are presented. The data are taken in the nighttime polar ionosphere in the regions with latitudes of 67°–88°, and in the period of high solar activity from October 26, 2003 to November 9, 2003. Typical ionospheric changes in the amplitude and phase of decimeter radio waves on paths GPS satellites-CHAMP satellite are presented. It is demonstrated that these data make it possible to determine characteristics of the sporadic E _s structures in the lower ionosphere at heights of 75–120 km. Histograms of distribution of the lower and upper boundaries, thickness, and intensity of the E _s structures are presented. Dispersion and spectra of amplitude fluctuations of decimeter radio waves caused by small-scale irregularity of the ionospheric plasma are analyzed. The relation of the polar E _s structures and intensity of small-scale plasma irregularity to various manifestations of solar activity is discussed. The efficiency of monitoring the ionospheric disturbances caused by shock waves of the solar wind by the radio occultation method on satellite-to-satellite paths is demonstrated.     

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.     

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.     

The range of Alfvénic turbulence scales in the topside auroral ionosphere

The minimal scale of the Alfvénic turbulence transverse to the external magnetic field in the topside auroral ionosphere is investigated using electric field observations of the FAST spacecraft (the resolution 512 s^–1). The events in which the power law form of the electric fluctuation spectra with a 2.0–2.5 slope (typical of Alfvénic turbulence) remains unchanged down to acoustic gyroradius ρ_s or ion gyroradius ρ_i local values are illustrated for the first time. In this case, the character of spectrum variation does not change at the electron inertial length λ_e, which is much larger than ρ_s and ρ_i for FAST altitudes (apogee ~4000 km). We have tried to explain this experimental fact by consideration of the known scenarios of the appearance of a small transverse scale in an Alfvénic perturbation. It has been noted that the effects of front steepening in an inertial Alfvén wave with a finite amplitude, which propagates at an angle smaller than (m_e/m_i)^1/2 with respect to the transverse direction, can result in small transverse scales comparable with acoustic gyroradius appearing in a perturbation.     

基于气相色谱法的电推进航天器氙气泄漏检测系统

为了能够对电推进航天器加注后的泄漏进行检测,对氙气泄漏检测方法和关键技术进行研究,研制了一套基于气相色谱法的氙气泄漏检测系统。试验结果表明,氙气体积分数在1×10-7~5×10-4之间时,系统可以定性定量判断氙气的真实泄漏量(1.0×10-5~5.0×10-2 Pa·m3·s-1);而当氙气体积分数超过5×10-4时,则应定性判断电推进系统有大泄漏(泄漏量10-2 Pa·m3·s-1)。检测系统能够满足电推进航天器加注后泄漏检测任务的要求。     

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.     

Optimization of radiation exposures during extravehicular activity using the effect of the West-East asymmetry of the fluxes of trapped protons

To estimate the protective properties of a space suit against cosmic radiation the dose rates were calculated for extravehicular activity in the ISS orbit for a number of representative points of critical organs of the human body. The screening functions of the Orlan-M space suit obtained by the authors earlier are used in the calculations. In addition, the effect of East-West asymmetry of the fluxes of high-energy protons trapped by the geomagnetic field is taken into account. It is shown that during passages through the South Atlantic Anomaly, choosing the optimal orientation of astronauts in relation to the cardinal directions, one can achieve for the most critical body organs a dose rate reduction by a factor of ∼1.5–1.8 (in the maximum of solar activity) and by a factor of ∼2–2.5 (in the solar activity minimum). The obtained results can serve for obtaining more accurate estimation of radiation risk for astronauts working in the Orlan-M space suit in the near-terrestrial orbits and for elaborating practical recommendations to reduce their radiation exposures.     

Relationship between the fluxes of relativistic electrons at geosynchronous orbit and the level of ULF activity on the Earth’s surface and in the solar wind during the 23rd solar activity cycle

We present the results of a cross-correlation analysis made on the basis of Spearman’s rank correlation method. The quantities to correlate are daily values of the fluence of energetic electrons at a geosynchronous orbit, intensities of ground and interplanetary ultra-low-frequency (ULF) oscillations in the Pc5 range, and parameters of the solar wind. The period under analysis is the 23rd cycle of solar activity, 1996–2006. Daily (from 6 h to 18 h of LT) magnetic data at two diametrically opposite observatories of the Intermagnet network are taken as ground-based measurements. The fluxes of electrons with energies higher than 2 MeV were measured by the geosynchronous GOES satellites. The data of magnetometers and plasma instruments installed on ACE and WIND spacecraft were used for analysis of the solar wind parameters and of the oscillations of the interplanetary magnetic field (IMF). Some results elucidating the role played by interplanetary ULF waves in the processes of generation of magneospheric oscillations and acceleration of energetic electrons are obtained. Among them are (i) high and stable correlation of ground ULF oscillations with waves in the solar wind; (ii) closer link of mean daily amplitudes of both interplanetary and ground oscillations with ‘tomorrow’ values of the solar wind velocity than with current values; and (iii) correlation of the intensity of ULF waves in the solar wind, normalized to the IMF magnitude, with fluxes of relativistic electrons in the magnetosphere.     

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.     

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.