同轴源原子氧地面模拟装置及其性能

叙述了同轴源原子氧模拟装置的基本工作原理和装置的各组成单元及其功能;介绍了装置性能的测量方法及结果。结果表明：装置产生的原子氧能量可以控制在５ｅＶ～１０ｅＶ;原子氧的束流强度约为４×１０１５个／ｃｍ２·ｓ;原子氧束中氧离子的含量小于０．１％。     

Variability of spectra in large solar energeticparticle events

Using data from the Solar Isotope Spectrometer on the Advanced Composition Explorer obtained during 36large solar energetic particle events (SEPs) that occurred during 1997–2002 we have examined the spectral characteristics of oxygen and iron. Based on the shape of the oxygen spectrum during the decay phase following the peak in particle intensity, each SEP event was categorized as either exponential (7 events) or power law (29 events). We find that the exponential events were typically the larger events (in terms of peak oxygen intensity) and had Fe/0 ratios that strongly decreased with increasing energy.Event-averaged Fe/0 ratios (integrated over 12 to 60 MeV/nucleon) were at or below coronal abundances for nearly all these events, while the ratios obtained in the power law events were typically enhanced over coronal values. The majority of the power law events had the same spectral index for both 0 and Fe resulting in an Fe/0 ratio independent of energy. However 6 of the 29 power law events had Fe/0 ratios that increased with increasing energy due to an Fe spectral index less negative than that of 0. We consider simple diffusion theory in an effort to understand the nature of these events and obtain preliminary but promising results.     

地球磁层极尖区场向电子事件期间能量特性研究

根据Cluster卫星2001年9月30日在北半球极尖区观测到的一次强扰动场向电子事件数据,分析研究了这次事件期间场向电子的能量特性,讨论了场向电子对太阳风能量向磁层的传输和磁层-电离层耦合过程中能量传输的作用.分析认为,这次电子扰动事件期间电子速度和密度都具有很强的扰动变化,电子速度增加是一个主要特点.本次事件中低能段5~200eV和500~1500eV内的能谱分析结果表明,上行电子通量大于下行电子通量,上行电子主要来源于电离层,说明电离层上行电子在本次事件中具有非常活跃的作用.根据电离层中带电粒子的能量特征分析结果可知,这次事件中电离层起源的上行电子在上行过程中得到了加速.关于加速机制问题还有待深入研究.      

Onset study of impulsive solar energetic particleevents

Impulsive solar energetic particle (SEP) events are associated with impulsive X-ray flares, energetic electrons,and enhanced heavy ion abundances. Using instruments on ACE, we have examined the composition and origin of twelve impulsive SEP events from November 1997 to June 2000. All selected impulsive SEP events have enhanced ³He/⁴He ratios compared with the solar wind values. The range of ³He/⁴He ratios varies from 0.01 to 7.8. By assuming scatter-free propagation at zero degree pitch-angle, we fitted the minimum particle path lengths (from 1.2 to 1.4 AU, as expected), and estimated the ion event release time back at the Sun to within better than 30 minutes in most cases. We found only four events in which the release times agree for both 38–50 keV electrons and <1 MeV/nucleon ions. Five of our events have significant differences (>40 minutes) between the electron and ion onset times, all with ions injected later. Three impulsive ion events have no association with any impulsive electron event. Seven events have associated solar electromagnetic signatures (Type III radio bursts and/or X-ray flares).     

Ionospheric losses of Venus in the solar wind

The nature of ionospheric losses from Venus is of essential importance for understanding the ionosphere dynamics of this unmagnetized planet. A plausible mechanism that can explain the escape of charged particles involves the solar wind interaction with the upper atmospheric layers of Venus. The hydrodynamic approach proposed for plasma expansion in the present study comprises two populations of positive ions and the neutralizing electrons, which interact with the solar wind electrons and protons. The fluid equations describing the plasma are solved numerically using a self-similar approach. The behavior of plasma density, velocity, and electric potential, as well as their reliance upon solar wind parameters have been examined. It is found that for noon midnight sites, the oxygen ion-to-electron relative density may be the main factor to enhance the ionic loss. However, the other parameters, like hydrogen density and solar wind density and velocity seem to do not stimulate the runaway ions. For lower dawn-dusk region, the plasma are composed of hydrogen and oxygen ions as well as electrons, but for higher altitudes only hydrogen ions and electrons are encountered. All ionic densities play an important role either to reduce or boost the ionic loss. The streaming solar wind velocity has no effect on the plasma escaping for lower altitudes, but it reduces the expansion at higher altitudes.     

On compositional variations of heavy ions during solar particle events

Intensity-time profiles of protons, alpha particles, and heavy ions (C, O, Fe) in the MeV/nucleon energy range have been analyzed for one solar particle event following the solar flare on September 23, 1978. The data have been obtained with the wide angle double dE/dx-E sensor of the Max-Planck-Institut/University of Maryland experiment onboard ISEE-3. We found time variations in the iron to helium ratio of up to 2 orders of magnitude and a significant variation of the O/He ratio during this event, whereas the C/O-ratio at the same energy/nucleon appears to be time independent. We investigated the influence of a rigidity dependent mean free path in interplanetary space and of rigidity dependent coronal propagation on heavy ion ratios during solar particle events. We found that both the magnitude and time scale of the ratio changes during the September 23 event cannot be explained by rigidity dependent interplanetary or coronal propagation alone. These ratio changes are probably caused by multiple injection at the sun.     

伴随磁层稳态对流的磁暴及磁暴期间环电流的特征

参考活跃的磁层稳态对流标准，选取了2001—2017年12个伴随磁层稳态对流的磁暴，研究发现这些磁暴存在以下共性:有长达约10h的漫长主相；其SYM-H存在一个最小值的平台期，约持续3～10h；这些磁暴发生时，部分环电流持续位于昏侧，其持续时间和行星际磁场分量B_z的稳定南向驱动时间相等.此外，这些磁暴发生时，其平台期的环电流离子的寿命为2.4～5.5h，比一般的大磁暴事件中离子寿命长，且其寿命与平台期长短没有明显关系.伴随稳态对流的大磁暴发生时，环电流离子寿命长，环电流衰减慢，推测是稳态对流期间能量持续而稳定注入磁层导致的.      

Relative fluxes of shock and prompt peaks in SEP event time profiles

Peak fluxes are an important property of gradual solar energetic particle (SEP) event time profiles from both astro/heliophysical and applications perspectives. However, the peak flux in an event may occur at the event onset, or at the time of the interplanetary shock arrival (the ESP or energetic storm particles). This makes an important difference in the interpretation of the peak flux, and in any attempts to characterize or model it. This paper describes a study of SEP data sets from ACE, IMP-8 and GOES toward determining the relative properties of these peak fluxes for protons with energies near 1, 10, and 50 MeV. The results suggest that for gradual events with both peaks, the ESP peak often dominates at 1 MeV energies and is dominant about half the time at 10 MeV. Moreover, the prompt peak fluxes can be used to estimate the shock peak (ESP event) up to days ahead, especially in the lower energy range.     

The connection between space weather and Single Event Upsets in polar low earth orbit satellites

Space weather is driven and modulated by the activity in the Sun. Space weather events have the potential to inflict critical damage to space systems. Nowadays, space assets are essential in our basic needs, such as communications, cell phone networks, navigation systems, television and internet. Hence, understanding space weather dynamics and its effects on spacecraft is crucial for satellites engineers and satellite operators, in order to prevent and mitigate its impacts.In the last decade our Sun has erupted several times causing dozens of space weather events. Some of these led to satellite malfunctions and outages lasting from mere hours, up to days and weeks. This research is focused on two different space weather events, March 7–8, 2012, and September 6–10, 2017, that occurred during the last ten years and caused satellite anomalies that are related to an increase in the single event upsets rate. Single event upset is a bit flip in a memory device due to high energy particle interaction with the device sensitive volume. During these two periods, Eros B, a low Earth orbiting polar satellite detected an increased rate of single event upsets on two of its processing computers when the high energy proton flux was elevated. On both occasions X-class flares were detected, and the increased single event upsets count rate in Eros B took place only after the 100 MeV protons flux was three orders of magnitude above the background levels. In this research, Israeli satellite anomalies that were detected are first demonstrated.     

Effect of heavy ions on bacterial spores.

Inactivation of B. subtilis spores has been studied using accelerated He, C, N, O and Ne ions. The energy dependence of the inactivation cross sections for heavy ions was very weak and the mean cross sections for carbon ions (0.6-4.7 MeV/amu), nitrogen ions (0.6-4.1 MeV/amu), oxygen ions (0.8-1.1 MeV/amu), and neon ions (2.2-3.7 MeV/amu) were found to be about 0.22, 0.23, 0.26, and 0.33 micrometer2 , respectively. Analysis was carried out along lines similar to Katz's target theory but the parameters were chosen so that they have an experimental basis.     

Imaging of reconnection processes in hard X-rays

The Hard X-ray Spectrometer aboard the SMM detected several events of energy release late in the development of two-ribbon flares. One such event, at 21:12 UT on 21 May, 1980 (～ 20 min after the flare onset and 15 min after the peak of the impulsive phase) is studied in detail. The site of new brightening first became visible in hard X-rays (> 22 keV) and only afterwards showed up at lower energies. It was clearly located high in the corona so that one can identify it with energy release at the tops of newly formed post-flare loops. Thus, if the Kopp and Pneuman model of the loop formation is adopted, we may have imaged here a reconnection process in the solar corona. An attempt is made to estimate physical parameters at the reconnection site.     

磁层氧离子向磁鞘泄漏的机制和效应

１９９７年 １月 １０日磁暴期间， Ｇｅｏｔａｉｌ卫星在向阳侧的磁鞘中观测到了磁层氧离子突增事件．这些氧离子的出现和磁鞘中存在很强的南向行星际磁场有关．事件期间向阳面发生了准静态的磁重联，氧离子流存在由北向南的速度分量．通量突增过程具有逆向和正向能量色散现象，磁层内部只有氧离子有可能被梯度漂移输送到重联区，所以只有氧离子在磁鞘中持续地被观测到．估计氧离子的逃逸速率为 ０．６１× １０２３／ｓ，大约为环电流氧离子输入率的 ３３％．大量的环电流氧离子由磁层跑到了磁鞘，导致环电流指数 ＡＳＹ－Ｈ呈现明显的非对称性．     

“风云一号（B）”卫星探测到的太阳质子事件

我国“风云一号(B)”气象卫星于1990年9月3日发射入轨,该星载有粒子成分监测器,用来探测空间粒子辐射环境,其中包括测量太阳耀斑时产生的太阳质子事件及其重粒子丰度;银河宇宙线异常成分与强度;内辐射带磁异常区的粒子通量及重粒子成分,“风云一号(B)”卫星运行半年来,我们已获取了上述有关的粒子辐射资料,在卫星上获得这些资料在我国尚属首次,本文主要分析观测到的太阳质子事件。     

On small active region filaments,fibrils and surges

High resolution Hα images and magnetograms (0.2 arc s) of an active region were obtained in alternating time series at 42 s cadences using the Swedish 1-m Solar Telescope on 2004 August 21. The Hα filtergrams reveal an active region filament and surges consisting of thread-like structures which have widths similar to the widths of chromospheric fibrils, both recorded down to the resolution limit in the best images. All observed structures in the active region appear highly dynamic. Fibrils show counterstreaming strongly resembling the counterstreaming threads in filaments.     

EUV imaging of near-Venus space

Japan’s Venus Climate Orbiter (the Planet-C spacecraft) will be launched in 2008 and will reach an orbit in the ecliptic plane around Venus in 2009. We propose two eXtreme UltraViolet (XUV) imagers to take global two-dimensional snapshots of near-Venus space, including the Venus ionosphere and the interaction region between the solar wind plasma and the Venus ionospheric plasma. The imagers detect the resonantly scattering emissions of oxygen ions (O II 83.4 nm) and atoms (O I 130.3 nm), neutral helium (He I 58.4 nm), and hydrogen (H Ly-α 121.6 nm). Scientific goals are to investigate mechanisms of momentum and mass transfer across the ionopause, of convection in the upper atmosphere and ionosphere, and of atmospheric escape. Especially, we emphasize that sequential images of the O II 83.4-nm emission will enable us to understand temporal evolution of the vortex produced by the Kelvin–Helmholtz (K–H) instability. Though the wave structure due to the K–H instability is generated also at the terrestrial magnetopause, oxygen ions are too tenuous to detect the emission. On the other hand, at the Venus ionopause oxygen ions have enough density to image the resonance emission, i.e., the Venus ionosphere plays a role as a space laboratory for plasma physics.     

Propagation of energetic particles in the solar wind

The characteristics of solar energetic particle events as observed in interplanetary space depend on many physical processes acting at the source and during the transport from the source to the observer. These processes, such as acceleration at the Sun and the propagation near the Sun and in interplanetary space depend, in general, on both the particle velocity and rigidity. Thus, the evaluation of both the nuclear charge and/or atomic mass and the ionic charge of heavy ions turns out to be essential for the interpretation of the physical parameters observed, such as the energy spectra and the compositional variations during individual solar energetic particle events. In this paper recent results on the direct determination of the charge states of He, C, O, and Fe will be summarized. Using these results the compositional variations during individual solar particle events will be discussed. It will be shown that ratio changes by a factor of ～ 10 during the onset phase of solar particle events, as frequently observed, could be explained not only by rigidity dependent interplanetary propagation, but also by rigidity dependent diffusive propagation in the corona. However, there is now increasing experimental evidence that also other processes, such as compositional variations at the source and discontinuities of the interplanetary magnetic field, separating two different particle populations, may be important. Thus the picture emerges that these variations do not have a unique explanation but rather that each event has to be investigated individually.     

太阳高能粒子观测特征经向分布统计

基于多卫星联合观测数据，筛选了2006年12月至2017年10月期间122个太阳高能粒子（SEP）事件及其伴随的日冕物质抛射（CME），分析了SEP事件属性随相对经度的变化、与CME属性之间相关性的经向分布以及与Fe/O比值的关联.研究结果显示:低Fe/O类事件的峰值通量I_p通常更高，伴随CME更大，但通量上升速度较慢，且其D_u（持续时间）和I_p与CME速度呈现更强的相关性；SEP特征时间T_O（CME爆发至SEP事件爆发）与T_R（SEP事件爆发至半峰值）随相对经度增加而增大，D_u与I_p随相对经度增加而减小，通量上升斜率K在±90°范围内自东向西递减；SEP事件属性与伴随CME属性的相关性随相对经度的改变有明显变化，在磁连接好的位置，T_O与CME速度等属性呈现负相关，T_R与CME速度等属性呈现正相关，D_u，I_p与CME速度之间的相关性更强.研究结果进一步表明，SEP事件观测属性既与CME参数相关，同时又具有很强的经度依赖性，在磁连接越好的位置卫星观测到的SEP事件强度越高，SEP观测参数受CME的影响越大，这对大型SEP事件的预报很有意义.此外，高Fe/O类SEP事件与CME相关性的减弱暗示了耀斑加速、种子粒子源等因素的影响.      

W掺杂对TiO2中氧空位形成能的影响

为研究Ti合金中常用的基体强化元素W对合金抗氧化性的作用,利用第一性原理方法计算了W掺杂对Ti合金氧化产物金红石TiO₂中氧空位形成能的影响。计算发现,W可以显著增大其近邻位置的氧空位的形成能,使其增大将近0.7 eV,这将有效抑制氧空位的产生以及环境中氧的渗透,对Ti合金的抗氧化性是有益的。同时研究了2个氧空位组成的不同构型的空位对,发现W同样可以增大氧空位对的形成能,但增加的数值平均到每个氧空位只有0.2 eV,即随着氧化的加剧和氧空位浓度的增加,W对抗氧化性能提高的效果减弱。电子态密度分析表明,对于不同构型的氧空位对,体系内的未配对电子分布在不同的能级水平,这导致了不同的空位形成能。     

Two sources of magnetosheath ions observed by Cluster in the mid-altitude polar cusp

Double cusps have been observed on a few occasions by polar orbiting spacecraft and ground-based observatories. The four Cluster spacecraft observed two distinct regions, showing characteristics of a double cusp, during a mid-altitude cusp pass on 7 August 2004. The Wind spacecraft detected a southward turning of the Interplanetary Magnetic Field (IMF) at the beginning of the cusp crossings and IMF–Bz stayed negative throughout. Cluster 4 observed a high energy step in the ion precipitation around 1 keV on the equatorward side of the cusp and a dense ion population in the cusp centre. Cluster 1, entering the cusp around 1 min later, observed only a partial ion dispersion with a low energy cutoff reaching 100 eV, together with the dense ion population in the cusp centre. About 9 min later, Cluster 3 entered the cusp and observed full ion dispersion from a few keV down to around 50 eV, together with the dense ion population in the centre of the cusp. The ion flow was directed poleward and eastward in the step/dispersion, whereas in the centre of the cusp the flow was directed poleward and westward. In addition the altitude of the source region of ion injection in the step/dispersion was found 50% larger than in the cusp centre. This event could be explained by the onset of dayside reconnection when the IMF turned southward. The step would be the first signature of component reconnection near the subsolar point, and the injection in the centre of the cusp a result of anti-parallel reconnection in the northern dusk side of the cusp. A three-dimensional magnetohydrodynamic (MHD) simulation is used to display the topology of the magnetic field and locate the sources of the ions during the event.     

Study of fast atoms in molecular gas plasma via emission spectroscopy

Fast atoms are generated in reactions of ions with the molecular gas in laboratory and astrophysical plasma. In hydrogen they are observed in the emission spectra via Excessive line broadening. Energetic atoms also occur in astrophysical plasma in hydrogen, nitrogen and oxygen. The proposal here is that low pressure discharges can be used to simulate the phenomena in certain space plasma. In this study, we have used a special configuration of the electrode system, to obtain energetic atoms in plasma of three types of diatomic gases (H₂, O₂, N₂). Emission spectroscopy was used to detect the atoms and measure their velocity. Energy analysis was performed to obtain atoms’ distributions and evaluate the mean energy of atoms. This was compared to the potential energy available from the electric field. The field acceleration model, previously established for hydrogen, was extended to nitrogen and oxygen. We suggest, that the same method of analysis can be applied for astrophysical plasma spectrum.