Ionospheric index of solar activity based on the data of measurements of the spacecraft signals characteristics

The method for estimating an ionospheric index of solar-activity (IISA) based on the processing of spacecraft radio signals is suggested. The IISA values have been obtained by comparison between the measured and calculated variations of radio-signal characteristics. To calculate the variations of radio-signal characteristics, the straight rays approximation and the solar-activity index (Wolf numbers W and/or values of F_10.7 solar flux) as a control parameter of the ionospheric model have been used. The suggested method was tested using spacecraft radio signals from the radio-navigation system “CIKADA”. The reduced differences of phases (ΔΦ) for frequencies 150 and 400 MHz were measured and the same characteristics were calculated by integration along the ray of radio-wave propagation between the receiver and the satellite. The IRI-95 has been used as a background ionospheric model. The satellite co-ordinates were determined using the orbit parameters recorded in the navigation messages. Minimization of the difference measured and calculated ΔΦ using arbitrary time steps, or during whole time intervals of observation, gives the IISA corresponding the satellite pass. Daily IISA values were obtained by averaging over all communication contacts during a day (20–30 passes). Testing this approach based on the measurements during March/April 1997, 1998, shows that on magnetically quiet days differences between IISA and the primary solar activity indices are about 5%.     

‘Digging-up’ Utopia? Space, practice and land use heritage

In this paper we explore history and heritage mobilised to do service for marginalized interests. We discuss how resources, such as, place, texts, artefacts and practice are drawn upon to forward particular political interests. Touching on recent work in non-representational theory we suggest that more attention be paid to the micro-politics of doing and link more formal action to that of ‘everyday’ practice. The examples used show how particular actors draw on history and heritage to advance their positions and how their performances reinforce claims based on alternative practices. The examples used illustrate how this involves the notion of ‘reclaiming’ historical action, historical texts and historical place. In particular how this relates to land and specifically in this paper the metaphor, representation and practice of ‘digging’.     

Rethinking the ‘domus’ in domestic violence: homelessness, space and domestic violence in South Africa

An examination of domestic violence and where it takes place provides significant insight into debates about the meaning of home. It is argued here that discussions of domestic violence could make more use of feminist geographers’ and development theorists’ analyses of the home. Examining the experiences of homeless and insecurely housed women in Durban, the paper aims to explore ideas of ‘home’ implicit in much research on domestic violence and argues that these ideas require further examination. The paper focuses on three assumptions about the home (in experiences of domestic violence); namely, the home as a formal material space, the home as private, and the domicile as home. In conclusion the paper argues for a more nuanced understanding of home.     

‘Making space’ in Cairo: Expatriate movements and spatial practices

This paper examines what it means to be an ‘expatriate’ in Cairo through the lens of movement and space-making. Inquiring into a set of migrant (im)mobilities, spatial practices, relations, and imaginations, it argues that as a ‘spatialised’ identity category ‘expatriate’ narrates and enacts migratory privileges linked to wider hierarchies of social difference. It contributes to a growing literature examining the social and political dimensions of ‘expatriate’ migration and further engages scholarship thinking space and movement in relational and socio-historical terms. Rather than denoting an easily distinguishable group of migrants, ‘expatriate’ emerged as a contingent and ambiguous category of practice. As such, ‘expatriate’ stands in a productive relationship with privileged movement and socio-spatial processes. Like other migrants, respondents skillfully navigated the global differences in wealth, power and status they were presented with. Yet, unlike many other migrants, they did so from a privileged position within the global power-geometries of international migration. Migrants’ personal geographies were further shaped by how bodies were racialised and gendered in entangled, intersecting and sometimes counter-intuitive ways. This diversity and complexity of ‘expatriate’ geographies highlights the necessity of intersectional and situated analyses of privilege.     

High-Energy Astronomy From The International Space Station

The European Space Agency, ESA, is currently studying 3 high-energy astronomy missions that use the International Space Station (ISS). These are Lobster-ISS, an all-sky imaging X-ray monitor, the Extreme Universe Space Observatory (EUSO) which will study the highest energy cosmic rays by using the Earth's atmosphere as a giant detector and XEUS — the X-ray Evolving Universe Spectroscopy Mission, a potential successor to ESA's XMM-Newton X-ray observatory. These first 2 missions will he attached to the external platforms on the Columbus module, while XEUS will visit the ISS to attach additional X-ray mirrors to enlarge the original 4.5 m diameter mirrors to the 10 m diameter required to observed redshifted iron lines from massive black holes in the early Universe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Characteristics of ≥ 290 keV magnetosheath ions

We performed a statistical analysis of 290–500 keV ion data obtained by IMP-8 during the years 1982–1988 within the earth’s magnetosheath and analysed in detail some time periods withdistinct ion bursts. These studies reveal the following characteristics for magnetosheath 290–500 keV energetic ions: (a) the occurrence frequency and the flux of ions increase with increasing geomagnetic activity as indicated by the Kp index; the occurrence frequency was found to be as high as P ≥ 42% for Kp ≥ 2, (b) the occurrence frequency in the dusk magnetosheath was found to be slightly dependent on the local time and ranged between ≈30% and ≈46% for all Kp values; the highest occurrence frequency was detected near the dusk magnetopause (21 LT), (c) the high energy ion bursts display a dawn-dusk asymmetry in their maximum fluxes, with higher fluxes appearing in the dusk magnetosheath, and (d) the observations in the dusk magnetosheath suggest that there exist intensity gradients of energetic ions from the bow shock toward the magnetopause. The statistical results are consistent with the concept that leakage of magnetospheric ions from the dusk magnetopause is a semi-permanent physical process often providing the magnetosheath with high energy (290–500 keV) ions.     

Stability of stationary and time-varying nongyrotropic particle distributions

The ubiquity of nongyrotropic particle populations in space plasmas warrants the study of their characteristics, in particular their stability. The unperturbed nongyrotropic distribution functions in homogeneous media without sources and sinks (closed phase space) must be rotating and time-varying (TNG), whereas consideration of open phase spaces allows for the occurrence of homogeneous and stationary distributions (SNG). The free energy brought about by the introduction of gyrophase organization in a particle population can destabilize otherwise thoroughly stable magnetoplasmas (or, a fortiori, enhance pre-existing gyrotropic instabilities) and feed intense wave growth both in TNG and SNG environments: The nongyrotropic (electron or ion) species can originate unstable coupling among the gyrotropic characteristic waves. The stability properties of these two types of homogeneous nongyrotropy shall be contrasted for parallel (with respect to the ambient magnetic field) and perpendicular propagation, and their potential role as wave activity sources shall be illustrated resorting to solutions of the appropriate dispersion equations and numerical simulations.     

Compressional wave events in the dawn plasma sheet observed by Interball-1

Compressional waves with periods greater than 2 min (about 10–30 min) at low geomagnetic latitudes, namely compressional Pc5 waves, are studied. The data set obtained with magnetometer MIF-M and plasma analyzer instrument CORALL on board the Interball-1 are analyzed. Measurements performed in October 1995 and October 1996 in the dawn plasma sheet at −30 R_E ≤ X_GSM and |Z_GSM| ≤ 10 R_E are considered. Anti-phase variations of magnetic field and ion plasma pressures are analyzed by searching for morphological similarities in the two time series. It is found that longitudinal and transverse magnetic field variations with respect to the background magnetic field are of the same order of magnitude. Plasma velocities are processed for each time period of the local dissimilarity in the pressure time series. VeloCity disturbances occur mainly transversely to the local field line. The data reveal the rotation of the veloCity vector. Because of the field line curvature, there is no fixed position of the rotational plane in the space. These vortices are localized in the regions of anti-phase variations of the magnetic field and plasma pressures, and the vortical flows are associated with the compressional Pc5 wave process. A theoretical model is proposed to explain the main features of the nonlinear wave processes. Our main goal is to study coupling of drift Alfven wave and magnetosonic wave in a warm inhomogeneous plasma. A vortex is the partial solution of the set of the equations when the compression is neglected. A compression effect gives rise to a nonlinear soliton-like solution.     

Latitudinal and longitudinal dispersion of energetic auroral protons

Using a collision by collision model from Lorentzen et al., the latitudinal and longitudinal dispersion of single auroral protons are calculated. The proton energies varies from 1 to 50 keV, and are released into the atmosphere at 700 km altitude. The dipole magnetic field has a dip-angle of 8 degrees. Results show that the main dispersion region is at high altitudes (300–350 km) and occurs during the first few charge exchange collisions. As the proton travels further down the atmosphere the mean free path becomes smaller, and as a result the spreading effect will not be as pronounced. This means that the first few charge exchange collisions fully determines the width of both the latitudinal and longitudinal dispersion. The volume emission rate was calculated for energies between 1 and 50 keV, and it was found that dayside auroral hydrogen emissions rates were approximately 10 times weaker than nightside emission rates. Simulations were also performed to obtain the dependence of the particle dispersion as a function of initial pitch-angle. It was found that the dispersion varies greatly with initial pitch-angle, and the results are summarized in two tables; a main and an extreme dispersion region.     

利用并行计算方法实现地震活动速率变化参数Z值的空间扫描处理及其计算效能评价

近30多年的研究表明,地震平静可能是中长期的地震前兆现象,而地震平静的内在特征体现了地震活动速率的变化. Z 检验法是检验地震活动速率变化应用最为广泛的方法之一,其度量值即 Z 值. 由于 Z 值空间扫描中采用等地震数的空间扫描窗口,每个空间扫描窗口的大小通常都是变化的,这样带来了大计算量的问题,因此,本文在自行组建的4节点PC机群上实现了 Z 值空间扫描的并行化处理. 初步测试结果说明,并行化处理中获取了很高的加速比和并行计算效率,可以将此种方法应用于其他地震活动性参数的空间扫描处理.