Observational evidence for non-equilibrium ionization in the solar corona

We investigate whether temperature sensitive EUV line ratios can be used as observational signatures for the presence of non-equilibrium ionization in transition region plasma. We compute the total intensity of some EUV lines of carbon and oxygen expected from coronal loop models with a steady-state flow and which are known to have significant departures from ionization equilibrium, selecting lines whose intensity ratios are useful for deducing the electron temperature in the coronal plasma. We calculate the intensity ratios with and without the approximation of ionization equilibrium, in order to determine the effects of any deviations from equilibrium on the numerical values of the line ratios examined.     

Manifestation of magnetic reconnection in coronal streamer current sheets

We investigate the possibility of observing the effects of magnetic reconnection inside a current sheet forming in a coronal streamer in the extended corona. In particular we study the possibility to observe with the UVCS of SOHO the excitation of the tearing instability in the current sheet.     

复杂可修系统可信度建模中任务维修度计算的统计推断方法

在设定每一部件的致命性故障率为常数并在确定出各部件任务修复时间置信上限的基础上,通过对可能发生的多次致命性故障事件的概率状态描述,得到了部件故障率与系统可信度的定量关系,进而依据这一可信度的建模原理归纳出不考虑任务修复时间的具体分布类型时复杂可修串联系统可信度的计算方法,同时也给出了任务维修度的统计推断表达式;最后,以典型的 ４ 部件串联可修系统为例,探讨了致命性故障次数、允许任务修复时间、部件任务修复时间的不同置信上限等的变化对系统可信度的影响,并论证了系统可靠性、维修性和保障性与可信度的关系。     

The Composition of the Solar Wind in Polar Coronal Holes

The solar wind charge state and elemental compositions have been measured with the Solar Wind Ion Composition Spectrometers (SWICS) on Ulysses and ACE for a combined period of about 25 years. This most extensive data set includes all varieties of solar wind flows and extends over more than one solar cycle. With SWICS the abundances of all charge states of He, C, N, O, Ne, Mg, Si, S, Ar and Fe can be reliably determined (when averaged over sufficiently long time periods) under any solar wind flow conditions. Here we report on results of our detailed analysis of the elemental composition and ionization states of the most unbiased solar wind from the polar coronal holes during solar minimum in 1994–1996, which includes new values for the abundance S, Ca and Ar and a more accurate determination of the ²⁰Ne abundance. We find that in the solar minimum polar coronal hole solar wind the average freezing-in temperature is ∼1.1×10⁶ K, increasing slightly with the mass of the ion. Using an extrapolation method we derive photospheric abundances from solar wind composition measurements. We suggest that our solar-wind-derived values should be used for the photospheric ratios of Ne/Fe=1.26±0.28 and Ar/Fe=0.030±0.007.     

Johannes Geiss’ Investigations of Solar, Heliospheric and Interstellar Matter

Johannes Geiss is a world leader and foremost expert on measurements and interpretation of the composition of matter that reveals the history, present state, and future of astronomical objects. With his Swiss team he was first to measure the composition of the noble gases in the solar wind when in the late 1960s he flew the brilliant solar wind collecting foil experiments on the five Apollo missions to the moon. Always at the forefront of the art of composition measurements, he with his colleagues determined the isotopic and elemental composition of the solar wind using instruments characterized by innovative design that have provided the most comprehensive record of the solar wind composition under all solar wind conditions at all helio-latitudes. He discovered heavy interstellar pickup ions, from which the composition of the neutral gas of the Local Interstellar Cloud is determined, and the “Inner Source” of pickup ions. Johannes Geiss played a key role both in the in-situ measurements and modeling of molecular ions in comets, and the interpretation of these data. He and co-workers measured the composition of plasmas in the magnetospheres of Earth and Jupiter. Here we highlight Johannes Geiss’ many discoveries and seminal contributions to our knowledge of the composition of matter of the Sun, solar wind, interstellar gas, early universe, comets and magnetospheres.     

An Update on Ultra-Heavy Elements in Solar Energetic Particles above 10 MeV/Nucleon

Measurements below several MeV/nucleon from Wind/LEMT and ACE/ULEIS show that elements heavier than Zn (Z=30) can be enhanced by factors of ∼100 to 1000, depending on species, in ³He-rich solar energetic particle (SEP) events. Using the Solar Isotope Spectrometer (SIS) on ACE we find that even large SEP (LSEP) shock-accelerated events at energies from ∼10 to >100 MeV/nucleon are often very iron rich and might contain admixtures of flare seed material. Studies of ultra-heavy (UH) SEPs (with Z>30) above 10 MeV/nucleon can be used to test models of acceleration and abundance enhancements in both LSEP and ³He-rich events. We find that the long-term average composition for elements from Z=30 to 40 is similar to standard solar system values, but there is considerable event-to-event variability. Although most of the UH fluence arrives during LSEP events, UH abundances are relatively more enhanced in ³He-rich events, with the (34<Z<40)/O ratio on average more than 50 times higher in ³He-rich events than in LSEP events. At energies >10 MeV/nucleon, the most extreme event in terms of UH composition detected so far took place on 23 July 2004 and had a (34<Z<40)/O enhancement of ∼250–300 times the standard solar value.     

Long-Term Fluences of Solar Energetic Particles from H to Fe

Data from ACE and GOES have been used to measure Solar Energetic Particle (SEP) fluence spectra for H, He, O, and Fe, over the period from October 1997 to December 2005. The measurements were made by four instruments on ACE and the EPS sensor on three GOES satellites and extend in energy from ∼0.1 MeV/nuc to ∼100 MeV/nuc. Fluence spectra for each species were fit by conventional forms and used to investigate how the intensities, composition, and spectral shapes vary from year to year.     

The Surface of Mercury as Seen by Mariner 10

The Mariner 10 spacecraft made three flyby passes of Mercury in 1974 and 1975. It imaged a little less than half of the surface and discovered Mercury had an intrinsic magnetic field. This paper briefly describes the surface of Mercury as seen by Mariner 10 as a backdrop to the discoveries made since then by ground-based observations and the optimistic anticipation of new discoveries by MESSENGER and BepiColombo spacecraft that are scheduled for encounter in the next decade.     

Outflow Velocities at the Base of a Polar Coronal Hole During the 1998 Total Eclipse

Polar coronal holes represent the most convincing site from which the high-speed solar wind originates. Here we report high-accuracy Doppler shifts measured in the O VI (1037.6 Å) line obtained by SUMER on SOHO inside an interplume region within the south polar coronal hole. We infer limits on the outflow velocity and draw hints about the flow geometry.     

舰载机机舰电磁兼容性适配技术研究

机舰适配性是舰载飞机总体设计的核心内容之一。近年来,随着不同作战用途舰载机及舰载无人机的上舰服役,舰机总体单位对机舰电磁兼容适配越来越重视,随着多种舰载机编队协同作战,机舰平台频谱资源愈发紧张,机舰电磁兼容性问题越来越突出,机舰电磁兼容适配性的影响也愈发突出,频谱不兼容导致的问题严重影响舰载机的作战性能。尤其是以无线电测控链为主要通信方式的舰载无人机,飞机测控系统布置在母舰上,无论是电磁安全问题,还是电磁频谱兼容问题都将更加突出。主要闸述舰载机,尤其是舰载无人作战飞机上舰后,从舰载机机舰电磁兼容适配的主要需求为切人点,从机舰作为一体化装备的角度,阐明了机舰电磁兼容适配设计的诸多要素。依据如何更好地发挥作战能力的原则,对机舰电磁兼容适配设计做了较为系统的描述。