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.     

Monitoring of the time and spatial distribution of neutron-flux spectral density outside the Russian segment of the <Emphasis Type="Italic">International Space Station</Emphasis> based on data from the BTN-Neutron space experiment

Results of measurements of neutron-flux spectral density in the vicinity of the International Space Station (ISS) based on BTN-Neutron space experimental data acquired in 2007–2014 have been presented in this paper. It has been shown that, during the flight of the ISS over different regions of the Earth’s surface, neutron flux in the energy range of 0.4 eV–15 MeV varies from 0.1 n/sm²/s in equatorial regions to 50 n/sm²/s in the South Atlantic anomaly region. The measurements were used to estimate the contribution of the neutron component to the overall exposure dose rate. The total contribution of fast neutrons is about 0.1–0.4 μ Zv/h above the equator area and more than 50 μ Zv/h above the South Atlantic anomaly region. A data analysis of BTN-Neutron data also showed that the time profile of neutron flux has long-periodic variations. It was found that, under the influence of Galactic cosmic rays (GCRs), modulation during 24th solar cycle neutron flux changed almost twofold (above high latitude regions). Maximum values of neutron flux were observed in January 2010 and minimum values were observed in January 2014.     

Plasma irregularities in unstable outer ionosphere according to the Intercosmos-Bulgaria-1300 satellite data

The results of the satellite low-latitude and mid-latitude measurements of the disturbed plasma concentration, electron temperature, and quasi-stable electric field at heights of ～900 km after sunset are discussed. It is shown that the sharp fronts of changes in the electron temperature and plasma density observed in the experiment onboard the Intercosmos-Bulgaria-1300 satellite in the low-latitude (and equatorial) outer ionosphere can be related to damping of the oscillations of plasma electrons at local decreases of the plasma density (plasma “pits”) and formation of the vortex plasma structures at density and temperature gradients, which promotes conservation of ionosphere irregularities and makes the fronts of concentration variations steeper. Nonmonotonic variations in the plasma conductivity for the ionosphere currents in unstable plasma can be a cause of observed nonmonotonic disturbances of the vertical component of the “constant” electric field.     

Sporadic structures in equatorial ionosphere as revealed from GPS occultation data

A method for monitoring of sporadic formations in the lower ionosphere by use of the amplitude and phase variations of decimeter radio waves in the occultation trans-ionospheric link GPS satellite — LEO CHAMP satellite is described. Typical variations of the amplitude and phase of the occultation signal, caused by layered formations in the lower ionosphere, are considered. Parameters of sporadic structures measured during period of especially strong solar flashes from October 25 till November 9, 2003, are described. Results of statistical analysis of the occurrence frequency of sporadic layers, their altitude distribution, and thickness are presented. The electron density distribution in the lower ionosphere in the equatorial zone is estimated.     

Magnetospheric signatures of auroral disturbances during the passage of the solar wind’s CIR and sheath regions

Based on Polar satellite data, the authors have studied the auroral disturbances that arose during the passage by the Earth of compressed plasma regions formed in front of high-speed solar wind streams (the CIR region) and in front of magnetic clouds (the Sheath region). The aurorae observed by the Polar satellite possessed basic signatures of a substorm: a localized onset and expansion toward the pole and westward and eastward. However, in these cases they had a very large size in longitude and latitude and occupied a very large area. All disturbances observed by the Polar satellite during the Sheath and CIR regions of the solar wind in December of 1996, in 1997–1998, and in 2000 were analyzed. Eight events during disturbance development in the ionosphere, when the Geotail satellite was located in the plasma sheet of the magnetospheric tail, were selected. It is shown that in all selected cases some typical signatures of substorm development in the magnetospheric tail were observed, namely: (1) fast plasma flows (flow reversal, i.e., from tailwards to Earthwards) and (2) a sharp decrease of the total pressure, which followed an interval of total pressure increase. One can draw the conclusion that in the CIR and Sheath regions with a high solar wind density, substorm disturbances of a specific type are observed, with large latitudinal and longitudinal size (sometimes occupying the entire polar cap).     

Penetration of solar cosmic rays into the Earth’s magnetosphere on January 28, 2012

Results of the comparative analysis of the dynamics of SCR fluxes with energies of 1–100 MeV in the interplanetary environment according to the data of the ACE and Wind spacecraft and within the Earth’s magnetosphere according to the data of the GOES-15 and Electro-L satellites in the region of geostationary orbits, and POES-19 and Meteor-M1 in the region of polar caps during two increases in SCR of January 19–31, 2012, are presented. It is shown that the decrease in the efficiency of SCR penetration into the Earth’s magnetosphere in the region of the orbits under study on January 28, 2012, is related to the passage of the Earth’s magnetosphere through the interplanetary environment structure with a quasi-radial interplanetary magnetic field and a small pressure of the solar wind.     

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.     

Effects of small-scale plasma disturbance on the IKB-1300 spacecraft potential

The potential of the Intercosmos-Bulgaria-1300 (IKB-1300) satellite launched to a circular orbit at an altitude ～900 km was measured with several instruments. Care was taken to equalize the potential along the satellite surface. The satellite was placed inside the conducting screen and the solar cells had a metal coating. The satellite potential slightly varied along the trajectory and in the typical case it was “?2”B that corresponds to 5 kTe/e. While the satellite crossed the auroral zone small-scale fluctuations of plasma and field parameters, known as shocks, were recorded. In this region a sharp decrease of the satellite negative potential is often observed. In this case the potential variations well correlate with the increasing flux of energetic electrons. The observed variations can be explained by secondary electron emission from the satellite surface.     

The Earth's Magnetosphere Response to Solar Wind Events according to the INTERBALL Project Data

The results of studying the interaction of two types of the solar wind (magnetic clouds and solar wind of extremely low density) with the Earth's magnetosphere are discussed. This study is based of the INTERBALL space project measurements and on the other ground-based and space observations. For moderate variations of the solar wind and interplanetary magnetic field (IMF) parameters, the response of the magnetosphere is similar to its response to similar changes in the absence of magnetic clouds and depends on a previous history of IMF variations. Extremely large density variations on the interplanetary shocks, and on leading and trailing edges of the clouds result in a strong deformation of the magnetosphere, in large-scale motion of the geomagnetic tail, and in the development of magnetic substorms and storms. The important consequences of these processes are: (1) the observation of regions of the magnetosphere and its boundaries at great distances from the average location; (2) density and temperature variations in the outer regions of the magnetosphere; (3) multiple crossings of geomagnetic tail boundaries by a satellite; and (4) bursty fluxes of electrons and ions in the magnetotail, auroral region, and the polar cap. Several polar activations and substorms can develop during a single magnetic cloud arrival; a greater number of these events are accompanied, as a rule, by the development of a stronger magnetic storm. A gradual, but very strong, decrease of the solar wind density on May 10–12, 1999, did not cause noticeable change of geomagnetic indices, though it resulted in considerable expansion of the magnetosphere.     

Pulsating aurora and quasiperiodic VLF hiss in the auroral zone morning sector: The event of December 30, 2011

The spatial–temporal variations in aurora and VLF emissions during an weak intensification in the auroral zone morning sector on December 30, 2011, have been analyzed. The event was accompanied by a negative bay (~70 nT) in the X component of the magnetic field at ground stations in northern Scandinavia. At the recovery phase of this bay, the precipitation zone moved and VLF emission frequency simultaneously increased over ten minutes, which may indicate that waves and precipitating electrons had a common source. VLF noise bursts in the 600–1000 Hz band with a characteristic modulation scale of ~10 s and the corresponding aurora intensifications localized in the ~100 km region were observed during the following ten minutes, which also confirms that recorded waves are related to electron precipitation. This correspondence of the pulsating aurora periods and VLF noise modulation has been revealed for the first time. The role of VLF wave generation processes during the cyclotron interaction with electrons in the magnetosphere and the propagation of these waves from the magnetosphere to the observation point are discussed.     

Plasma flow disturbances in the magnetospheric plasma sheet during substorm activations

We have considered variations in fields and particle fluxes in the near-Earth plasma sheet on the THEMIS-D satellite together with the auroral dynamics in the satellite-conjugate ionospheric part during two substorm activations on December 19, 2014 with K _p = 2. The satellite was at ~8.5R_E and MLT = 21.8 in the outer region of captured energetic particles with isotropic ion fluxes near the convection boundary of electrons with an energy of ~10 keV. During substorm activations, the satellite recorded energetic particle injections and magnetic field oscillations with a period of ~90 s. In the satellite-conjugate ionospheric part, the activations were preceded by wavelike disturbances of auroral brightness along the southern azimuthal arc. In the expansion phase of activations, large-scale vortex structures appeared in the structure of auroras. The sudden enhancements of auroral activity (brightening of arcs, auroral breakup, and appearance of NS forms) coincided with moments of local magnetic field dipolarization and an increase in the amplitude Pi2 of pulsations of the B_z component of the magnetic field on the satellite. Approximately 30–50 s before these moments, the magnetosphere was characterized by an increased rate of plasma flow in the radial direction, which initiated the formation of plasma vortices. The auroral activation delays relative to the times when plasma vortices appear in the magnetosphere decreased with decreasing latitude of the satellite projection. The plasma vortices in the magnetosphere are assumed to be responsible for the observed auroral vortex structures and the manifestation of the hybrid vortex instability (or shear flow ballooning instability) that develops in the equatorial magnetospheric plane in the presence of a shear plasma flow in the region of strong pressure gradients in the Earthward direction.     

三结太阳电池高能电子损伤模拟及仿真分析

利用wx AMPS软件构建了高效Ga In P/Ga As/Ge太阳电池的中电池模型,并对电池抗辐照性能进行模拟研究。模拟发现,当辐照缺陷密度较小时,缺陷对中电池的电性能影响较小;当缺陷密度较大时,电性能的下降与电子注量值的对数成正比。计算电池的I-V和量子效率谱(QE曲线)可知,电池电性能的下降直接对应于量子效率的下降、饱和暗电流的增强以及并联电阻的衰降。模拟结果与试验结果的对比显示,在各子电池均匀损伤的假定下,1 Me V电子辐照的缺陷引入率约为0.81。     

Modeling the Modification of the Nighttime High-Latitude F-Region by Powerful HF Radiowaves

A mathematical model of the high-latitude F-region, taking the ionospheric plasma convection into account, is used for modeling a response of the auroral F-region to irradiation by powerful high-frequency (HF) radiowaves. The model enables us to calculate the time variations in the profiles of the electron concentration, the velocity of positive ions, and the ion and electron temperatures in the part of a magnetic-flux tube moving over an artificial ionospheric heater under the action of a convective electric field. The modeling was carried out for a part of the magnetic flux tube intersecting the F-layer irradiated by the Norwegian heater at Tromsö when it is located near the midnight magnetic meridian. The calculations were made for the equinox conditions under the high solar and low geomagnetic activity. The results of our modeling show that substantial variations in the profiles of the electron temperature, the velocity of positive ions, and the electron concentration can be produced in the nighttime high-latitude F-layer due to HF heating. The perturbation caused by a 20 s rectangular pulse should exist for about 20 min at the level of the F-layer maximum. The disturbed plasma volume can leave the region irradiated by the heater and move away for over 500 km within the above-mentioned time period.     

“嫦娥一号”卫星观测近月太阳风离子特征

"嫦娥一号"卫星的太阳风离子探测器(SWIDs)的科学目标是研究太阳风与月球的相互作用以及相应的近月空间等离子体环境。文章利用"嫦娥一号"卫星SWIDs探测器在2007年12月30日的观测数据对近月太阳风等离子体环境,包括向阳侧太阳风离子、"拾起"离子以及在月球尾迹边界处的太阳风离子的特征进行分析,得到以下主要观测结果:1)在慢速太阳风中观测到双峰结构,分别为太阳风中的氢离子和二价氦离子;2)在行星际磁场具有明显昏向(+By)分量期间,在月球向阳侧持续观测到有月表散射或反射后被拾起的太阳风离子;3)与入射的太阳风离子不同,这些拾起的太阳风离子具有明显的角度分布特征;4)在行星际磁场昏向(晨向)期间,太阳风中的氢离子在月球尾迹北半球的边界处呈现减速(加速)特征并进入尾迹;而并未发现氦离子进入尾迹的特征。"嫦娥一号"卫星的这些观测数据对于认识近月空间等离子体环境有着重要的意义。     

磁力矩器对星外等离子体分布影响分析

文章通过计算某型号磁力矩器工作时产生的磁场,分析了等离子体在磁力矩器磁场中的运动状态,计算了电子在磁力矩器周围的密度分布。结果显示:在磁力矩器工作时,周围电子密度将增大,最大可为正常密度的10倍。密度增大的区域尺寸在轴向上略大于磁力矩器的长度,越靠近磁力矩器的两端电子密度越小,形成一个“凹陷”;径向上主要在半径小于4 m的范围内。在此区域应避免摆放对带电粒子敏感的部组件。     

Motion and transport of solar cosmic rays in heliospheric traps: The event on January 28–31, 2001

The results of studying the enhancement of solar cosmic ray fluxes on January 28?C31, 2001 in a wide energy range are presented using the ACE spacecraft data. A comparative analysis of temporal variations of the fluxes of charged particles and of the interplanetary medium parameters (interplanetary magnetic field and solar wind) has been performed on the basis of the ??reflection?? model of motion, accumulation, and modulation of cosmic rays. It is shown that a magnetic trap for solar cosmic rays was created by a plasma stream and flare ejection from an active region in the western part of the solar disk. Particles of low energies (<10 MeV) were captured inside the trap; the dispersion of distribution of particles with different energies inside the trap being determined by its complicated magnetic structure. The power-low dependence of the time of maximum for the flux of particles on their energy is found, and softer energy spectrum inside the trap is explained.     

Concentration of ions in the topside ionosphere as measured onboard the <Emphasis Type="Italic">DEMETER</Emphasis> satellite: Morphology and dependence on solar and geomagnetic activity

Variations in concentration of ions H⁺, He⁺, and O⁺ are studied at a height of about 700 km using the data of continuous observations onboard the DEMETER satellite at the decline and in the minimum of solar activity from 2004 to 2008. Latitudinal distributions, seasonal behavior, and irregular variations in ion concentrations and their dependence on solar and geomagnetic activity are considered. Within this altitude range, for the first time an analysis is performed of the dataset of many-year continuous observations in both hemispheres from the equatorial to subauroral latitudes. This made it possible to describe the seasonal and irregular variations of the concentrations of main ion species with better time and spatial resolution than in the available empirical models. The dependence of concentrations of three types of ions on solar and geomagnetic activity is studied at time scales from several days to several years, and it is shown that the anti-phase change in concentrations of O⁺ and light ions known from publications is partly a result of mutual dependence of solar and geomagnetic activity and is observed only at time scales beginning from several months. At time scales from several days to several weeks, variations in the concentration of O⁺ and light ions are governed mainly by solar and geomagnetic activity, respectively.     

Possible role of electrostatic potential in formation of sharp boundaries of small-scale and middle-scale solar wind structures

Sharp boundaries of small-scale and middle-scale structures of the solar wind are an essential part of a turbulized solar wind. Such boundaries are observed near the Earth’s orbit as sharp and large-amplitude changes of parameters (in particular, ion density) of the solar wind. In this paper, the observed phenomena are briefly described, and an account of their basic properties and specific features is given. Using the kinetic approach, a possible theoretical mechanism is suggested in order to explain some peculiarities in the formation of these structures.     

Effect of large and sharp changes of solar wind dynamic pressure on the earths’s magnetosphere: analysis of several events

The magnetosphere and ionosphere response to arrival of large changes of the solar wind dynamic pressure with sharp fronts to the Earth is considered. It is shown that, under an effect of an impulse of solar wind pressure, the magnetic field at a geosynchronous orbit changes: it grows with increasing solar wind pressure and decreases, when the solar wind pressure drops. Energetic particle fluxes also change: on the dayside of the magnetosphere the fluxes grow with arrival of an impulse of solar wind dynamic pressure, and on the nightside the response of energetic particle fluxes depends on the interplanetary magnetic field (IMF) direction. Under the condition of negative Bz-component of the IMF on the nightside of the magnetosphere, injections of energetic electron fluxes can be observed. It is shown, that large and fast increase of solar wind pressure, accompanied by a weakly negative Bz-component of the IMF, can result in particless’ precipitation on the dayside of the auroral oval, and in the development of a pseudobreakup or substorm on the nightside of the oval. The auroral oval dynamics shows that after passage of an impulse of solar wind dynamic pressure the auroral activity weakens. In other words, the impulse of solar wind pressure in the presence of weakly negative IMF can not only cause the pseudobreakup/substorm development, but control this development as well.     

Quasiperiodic VLF emissions: Analysis of periods on different timescales

The properties of quasiperiodic (QP), extremely low-frequency (ELF), and very low-frequency (VLF) emissions detected at a ground-based station in northern Finland between 15:00 UT and 22:00 UT on December 24, 2011 were studied. Characteristic periods in the spectra of QP emissions at different timescales and their dynamics during the considered event were analyzed. Two types of period variations of the QP emissions were observed: a regular increase of periods on timescales of 1 min to 2.5 min and appreciable period variations on a timescale of 1–10 min during substorms. These period variations are explained based on the properties of a self-oscillating cyclotron-instability regime in the magnetosphere. The analysis of the fine structure of the spectra of QP elements indicated that short-periodic modulations with periods of approximately 3 and 6 s were detected in the low-frequency part of the spectrum (f < 2.5 kHz) and in the high-frequency part of the spectrum (f > 2.5 kHz), respectively. The 6 s period corresponded to the period of two-hop propagation of whistling atmospherics. The presence of this short-periodic modulation may be related to the passive mode locking in a magnetospheric cyclotron maser.