Magnetospheric Physics in China:2014—2015

In the past two years, much progress is made in magnetospheric physics by using the data of Double Star Program, Cluster, THEMIS, RBSP, Swarm missions etc., or by computer simulations. This paper briefly reviews these works based on papers selected from the 191 publications from January 2014 to December 2015. The subjects cover various sub-branches of magnetospheric physics, including geomagnetic storm, magnetospheric substorm, magnetic reconnection, solar windmagnetosphere-ionosphere interaction, radiation belt, outer magnetosphere, magnetotail, plasmasphere, geomagnetic field, auroras and currents.      

Magnetospheric Physics in China: 2012–2014

In the past two years, many progresses have been made in magnetospheric physics by using the data of Double Star Program, Cluster, THEMIS and RBSP missions, or by computer simulations. This paper briefly reviews these works based on papers selected from the 126 publications from March 2012 to March 2014. The subjects cover various sub-branches of magnetospheric physics,including geomagnetic storm, magnetospheric substorm and magnetic reconnection.     

Magnetospheric physics in China: 2008—2010

In the past two years, most of the works on magnetospheric physics were made by using the data of Double Star Program and Cluster missions. However some works were still conducted by computer simulation or using the data from other space missions and ground geomagnetic observations. This paper briefly review these previous works based on papers selected from the 28 publications from April 2008 to April 2010. The subjects covered various sub-branches of magnetospheric physics, including geomagnetic storm, magnetospheric substorm and etc.      

Recent Progresses of Magnetospheric Physics in China: 2010-2011

In the past two years, many progresses are made in magnetospheric physics by using either the data of Double Star Program, Cluster and THEMIS missions, or by computer simulations. This paper briefly reviews these works based on papers selected from the 80 publications from April 2010 to April 2011. The subjects covered various sub-branches of magnetospheric physics, including geomagnetic storm, magnetospheric substorm, etc.      

The role of scientific ballooning for exploration of the magnetosphere

The magnetosphere is explored in situ by satellites, but measurements near the low altitude magnetospheric boundary by rockets, balloons and groundbased instruments play a very significant role. The geomagnetic field provides a frame with anisotropic wave and particle propagation effects, enabling remote sensing of the distant magnetosphere by means of balloon-borne and groundbased instruments. Examples will be given of successful studies, with coordinated satellite and balloon observations, of substorm, pulsation and other phenomena propagating both along and across the geomagnetic field. Continued efforts with sophisticated balloon-borne instrumentations should contribute substantially to our understanding of magnetospheric physics.     

The automatic detection of geomagnetic-storm sudden commencements

Storm Sudden Commencements (SSCs) are sharp offsets in the global geomagnetic field H component which accompany some geomagnetic storms. SSC signatures, which are a strong function of geographic location and local time, are usually explained as the result of magnetospheric and ionospheric responses to a compression caused by propagating discontinuities in the solar wind. The Space Environment Services Center (SESC) in Boulder, Colorado, has recently instituted an SSC ‘alarm’ to alert both forecasters and customers of potential geomagnetic storm conditions. The present software design looks for rapid change, coincidental within one minute, in the H-components among any two of the three magnetometers received in real-time at the SESC. These are the Boulder magnetometer, and the magnetometers on board the GOES geosynchronous satellites located at 75° and 135° West Longitude. The results are not yet satisfactory and offer some clues toward a better understanding of the physics of SSCs.     

Variation of energetic particle precipitation with local magnetic time

The detailed study of the precipitation of magnetospheric particles into the atmosphere is complicated by the rather complex spatial configuration of the precipitation region and its variability with geomagnetic activity. In this paper we will introduce polar oval coordinates and apply them to POES observations of 30 keV to 2.5 MeV electrons and comparable protons to illustrate the dependence of particle precipitation on local time and geomagnetic activity. These coordinates also allow an easy separation of the spatial precipitation patterns of solar and magnetospheric particles. The results indicate that (a) the spatial precipitation pattern of energetic magnetospheric electrons basically follows the pattern of the field parallel Birkeland currents up to MeV energies and (b) at least in the mesosphere the influence of magnetospheric electrons is comparable to the one of solar electrons. Implications for modeling of atmospheric chemistry will be sketched.     

MAGNETOSPHERIC PHYSICS IN CHINA:2000-2002

This brief report presents the latest advances of the magnetospheric physics researches in China during the period of 2000-2002, made independently by Chinese space physicists and through international cooperation. The related areas cover almost every aspect of magnetospheric physics.     

Geomagnetic transmission disturbances and heavy-ion fluences observed in low Earth orbit during the solar energetic particle events of October 1989.

The large solar energetic particle (SEP) events and simultaneous large geomagnetic disturbances observed during October 1989 posed a significant, rapidly evolving space radiation hazard. Using data from the GOES-7, NOAA-10, IMP-8 and LDEF satellites, we determined the geomagnetic transmission, heavy ion fluences, mean Fe ionic charge state, and effective radiation hazard observed in low Earth orbit (LEO) for these SEPs. We modeled the geomagnetic transmission by tracing particles through the combination of the internal International Geomagnetic Reference Field (IGRF) and the Tsyganenko (1989) magnetospheric field models, extending the modeling to large geomagnetic disturbances. We used our results to assess the radiation hazard such very large SEP events would pose in the anticipated 52 degrees inclination space station orbit.     

Circulation of energetic ions of terrestrial origin in the magnetosphere

Energetic ion composition measurements have now been performed from earth orbiting satellites for more than a decade. As early as 1972 we knew that energetic (keV) ions of terrestrial origin represented a non-negligible component of the storm time ring current. We have now assembled a significant body of knowledge concerning energetic ion composition throughout much of the earth's magnetosphere. We know that terrestrial ions are a common component of the hot equatorial magnetospheric plasma in the ring current and the plasma sheet out to ? 23 R_E. During periods of enhanced geomagnetic activity this component may become dominant. There is also clear evidence that the terrestrial component (specifically O⁺) is strongly dependent on solar cycle. Terrestrial ion source, transport, and acceleration regions have been identified in the polar auroral region, over the polar caps, in the magnetospheric boundary layers, and within the magnetotail lobes and plasma sheet boundary layer. Combining our present knowledge of these various magnetospheric ion populations, it is concluded that the primary terrestrial ion circulation pattern associated with enhanced geomagnetic activity involves direct injection from the auroral ion acceleration region into the plasma sheet boundary layer and central plasma sheet. The observed terrestrial component of the magnetospheric boundary layer and magnetotail lobes are inadequate to provide the required influx. They may, however, contribute significantly to the maintenence of the plasma sheet terrestrial ion population, particularly during periods of reduced geomagnetic activity. It is further concluded, on the basis of the relative energy distributions of H⁺ and O⁺ in the plasma sheet, that O⁺ probably contributes significantly to the ring current population at energies inaccessible to present ion composition instrumentation (? 30 keV).     

Magnetospheric Physics in China:2002-2004

This brief report presents the latest advances of the magnetospheric physics researches in China during the period of 2002-2004. The progress of the magnetospheric space mission DSP is given in another dedicated paper of this issue.     

磁层－电离层电动耦合与中纬地磁指数的变化

本文探讨磁层一电离层耦合过程内中纬地磁指数的变化特点，并与极光电集流和赤道电集流（指数）变化相比较．相关分析和时序叠加分析均表明，高、中、低纬地磁指数变化可归结为磁层一电离层电动耦合的统一物理图象．有Ｒ事件的磁暴主相初期和无Ｒ事件的磁扰期内，赤道电集流和中纬地磁指数的变化各不相同．这再次证明，耦合分析中将磁层源扰动的直接穿透作用与经电离层内动力过程的效应二者加以区分和综合研究是很重要的．     

磁层-电离层电动耦合与中纬地磁指数的变化

本文探讨磁层一电离层耦合过程内中纬地磁指数的变化特点,并与极光电集流和赤道电集流(指数)变化相比较。相关分析和时序叠加分析均表明,高、中、低纬地磁指数变化可归结为磁层一电离层电动耦合的统一物理图象。有R事件的磁暴主相初期和无R事件的磁扰期内,赤道电集流和中纬地磁指数的变化各不相同。这再次证明,耦合分析中将磁层源扰动的直接穿透作用与经电离层内动力过程的效应二者加以区分和综合研究是很重要的。      

The Earth’s magnetosphere response to interplanetary medium conditions on January 21–22, 2005 and on December 14–15, 2006

The Earth’s magnetosphere response to interplanetary medium conditions on January 21–22, 2005 and on December 14–15, 2006 has been studied. The analysis of solar wind parameters measured by ACE spacecraft, of geomagnetic indices variations, of geomagnetic field measured by GOES 11, 12 satellites, and of energetic particle fluxes measured by POES 15, 16, 17 satellites was performed together with magnetospheric modeling based in terms of A2000 paraboloid model. We found the similar dynamics of three particle populations (trapped, quasi-trapped, and precipitating) during storms of different intensities developed under different external conditions: the maximal values of particle fluxes and the latitudinal positions of the isotropic boundaries were approximately the same. The main sources caused RC build-up have been determined for both magnetic storms. Global magnetospheric convection controlled by IMF and substorm activity driven magnetic storm on December 14–15, 2006. Extreme solar wind pressure pulse was mainly responsible for RC particle injection and unusual January 21, 2005 magnetic storm development under northward IMF during the main phase.     

Longitudinal variations of geomagnetic and ionospheric parameters in the Northern Hemisphere during magnetic storms according to multi-instrument observations

We present a joint analysis of longitude-temporal variations of ionospheric and geomagnetic parameters at middle and high latitudes in the Northern Hemisphere during the two severe magnetic storms in March and June 2015 by using data from the chains of magnetometers, ionosondes and GPS/GLONASS receivers. We identify the fixed longitudinal zones where the variability of the magnetic field is consistently high or low under quiet and disturbed geomagnetic conditions. The revealed longitudinal structure of the geomagnetic field variability in quiet geomagnetic conditions is caused by the discrepancy of the geographic and magnetic poles and by the spatial anomalies of different scales in the main magnetic field of the Earth. Variations of ionospheric parameters are shown to exhibit a pronounced longitudinal inhomogeneity with changing geomagnetic conditions. This inhomogeneity is associated with the longitudinal features of background and disturbed structure of the geomagnetic field. During the recovery phase of a storm, important role in dynamics of the mid-latitude ionosphere may belong to wave-like thermospheric disturbances of molecular gas, propagating westward for several days. Therefore, it is necessary to extend the time interval for studying the ionospheric effects of strong magnetic storms by a few days after the end of the magnetospheric source influence, while the disturbed regions in the thermosphere continues moving westward and causes the electron density decrease along the trajectories of propagation.     

Geomagnetic storm effects on the earth''s ozone layer

The study of the response of the terrestrial environment to the different forms of solar activity is a relevant task. Geomagnetic perturbations arise from the solar wind/magnetospheric coupling and major magnetic storms are caused by intense, long duration Southward interplanetary magnetic fields. This paper addresses reader's attention on possible effects induced by geomagnetic storms on the Earth's ozone layer by reporting a series of experimental results related to the topic. Difficulties connected with a right assessment of such kind of effects are described.     

Effects of geomagnetic storms on the bottomside ionospheric F region

The geomagnetic storm is a complex process of solar wind/magnetospheric origin. The variability of the ionospheric parameters increases substantially during geomagnetic storms initiated by solar disturbances. Various features of geomagnetic storm act at various altitudes in the ionosphere and neutral atmosphere. The paper deals with variability of the electron density of the ionospheric bottomside F region at every 10 km of altitude during intense geomagnetic storms with attention paid mainly to the distribution of the F1 region daytime ionisation. We have analysed all available electron density profiles from some European middle latitude stations (Chilton, Pruhonice, Ebro, Arenosillo, Athens) for 36 events that occurred in different seasons and under different levels of solar activity (1995–2003). Selected events consist of both depletion and increase of the F2 region electron density. For European higher middle and middle latitude the F1 region response to geomagnetic storm was found to be negative (decrease of electron density) independent on the storm effect on the F2 region. For lower middle latitude the F1 response is weaker and less regular. Results of the analysis also show that the maximum of the storm effect may sometimes occur below the height of the maximum of electron density (NmF2).     

A method for operative calculation of charged particle penetration into the LEO

We develop a simple method for calculating the effective vertical cutoff rigidity of charged particles, taking into account the Kp-index and the local time, on the basis of generalization of the results of extensive trajectory calculations for trial particles moving in the geomagnetic field. The vertical cutoff rigidities, calculated by the Tsyganenko-89 model, are presented as an International Geomagnetic Reference Field (IGRF) model calculated and thereafter corrected in accordance with the geomagnetic disturbance and local time conditions. The fits from the proposed method agree with the results of cutoff rigidity measurements carried out by satellites. The method is intended for applications using cutoff calculations, such as evaluating particle penetration of spatial boundaries, calculating magnetospheric transmissions for low-orbital spacecrafts flights and interpreting the results of orbital experiments.     

Ionospheric response to solar and magnetospheric protons during January 15–22, 2005: EAGLE whole atmosphere model results

We present an analysis of the ionosphere and thermosphere response to Solar Proton Events (SPE) and magnetospheric proton precipitation in January 2005, which was carried out using the model of the entire atmosphere EAGLE. The ionization rates for the considered period were acquired from the AIMOS (Atmospheric Ionization Module Osnabrück) dataset. For numerical experiments, we applied only the proton-induced ionization rates of that period, while all the other model input parameters, including the electron precipitations, corresponded to the quiet conditions. In January 2005, two major solar proton events with different energy spectra and proton fluxes occurred on January 17 and January 20. Since two geomagnetic storms and several sub-storms took place during the considered period, not only solar protons but also less energetic magnetospheric protons contributed to the calculated ionization rates. Despite the relative transparency of the thermosphere for high-energy protons, an ionospheric response to the SPE and proton precipitation from the magnetotail was obtained in numerical experiments. In the ionospheric E layer, the maximum increase in the electron concentration is localized at high latitudes, and at heights of the ionospheric F2 layer, the positive perturbations were formed in the near-equatorial region. An analysis of the model-derived results showed that changes in the ionospheric F2 layer were caused by a change in the neutral composition of the thermosphere. We found that in the recovery phase after both solar proton events and the enhancement of magnetospheric proton precipitations associated with geomagnetic disturbances, the TEC and electron density in the F region and in topside ionosphere/plasmasphere increase at low- and mid-latitudes due to an enhancement of atomic oxygen concentration. Our results demonstrate an important role of magnetospheric protons in the formation of negative F-region ionospheric storms. According to our results, the topside ionosphere/plasmasphere and bottom-side ionosphere can react to solar and magnetospheric protons both with the same sign of disturbances or in different way. The same statement is true for TEC and foF2 disturbances. Different disturbances of foF2 and TEC at high and low latitudes can be explained by topside electron temperature disturbances.