利用地基GPS数据研究2006年12月电离层磁暴现象

利用中国大陆全球定位GPS台网数据和中国周边地区国际IGS站数据，研究了2006年12月中旬的 磁暴对中国大陆上空电离层的影响。结果显示,该磁暴对中国大陆上空电离层的影响并不显著。     

Contribution of domain rotation to the magnetic susceptibility of spherical two-domain particles of magnetite

Summary. Starting with a simplified picture of the presumed magnetization configuration in a two-domain sphere of magnetite, the initial susceptibility due to rotation of the magnetization in the domains has been calculated. In particles between 100 and 300 nm in diameter the calculated susceptibility for randomly oriented particles drops rapidly from about 6 to a little over 3, which is the value to be expected for large multidomain particles. The results agree well with the available experimental results and imply that in magnetite particles in this size range the low field susceptibility is dominated by the domain rotation and that wall motion is effectively inhibited.     

The radial structure of hot one-temperature accretion flows with advection

Considering nonthermal e^±-pair production, this paper is focused on the radial structure of hot one-temperature accretion flows with advection under the condition of small viscous parameter ( = 0.1) and low mass-accretion rates. Self-similar relations of hot flow with advection have been adopted. The authors have used a scheme, in which the two regions of accretion flow are calculated separately and then joined together. Some typical features of hot flow with advection have been confirmed, and several new results obtained: there exists a critical radius r_cr; the local cooling rate is inversely proportional to the square of the mass of the central object; the e^±-pair process affects significantly the radiation of hot flows with advection.     

Thermosolutal-convective instability in a stellar atmosphere

The thermosolutal-convective instability of a stellar atomsphere is studied in the presence of suspended particles. The criteria for monotonic instability are derived and are found to hold good also in the presence of uniform rotation and uniform magnetic field on the thermosolutal-convective instability. The thermosolutal-convective instability of a stellar atmosphere is also studied in the presence of suspended particles and radiative transfer effects and the criteria for monotonic instability are obtained in terms of source function.     

Microstructural, chemical and textural records during growth of snowball garnet

The growth history of two populations of snowball garnet from the Lukmanier Pass area (central Swiss Alps) was examined through a detailed analysis of three-dimensional geometry, chemical zoning and crystallographic orientation. The first population, collected in the hinge of a chevron-type fold, shows an apparent rotation of 360°. The first 270° are characterized by spiral-shaped inclusion trails, gradual and concentric Mn zoning and a single crystallographic orientation, whereas in the last 90°, crenulated inclusion trails and secondary Mn maxima centred on distinct crystallographic garnet domains are observed. Microstructural, geochemical and textural data indicate a radical change in growth regime between the two growth sequences. In the first 270°, growth occurred under rotational non-coaxial flow, whereas in the last 90°, garnet grew under a non-rotational shortening regime. The second population, collected in the limb of the same chevron-type fold structure, is characterized by a spiral geometry that does not exceed 270° of apparent rotation. These garnet microstructures do not record any evidence for a modification of the stress field during garnet growth. Concentric Mn zoning as well as a single crystallographic orientation are observed for the entire spiral. Electron backscatter diffraction data indicate that nearly all central domains in the snowball garnet are characterized by one [001] axis oriented (sub-)parallel to the symmetry axis and by another [001] axis oriented (sub-)parallel to the orientation of the internal foliation. These features suggest that the crystallographic orientation across the garnet spiral is not random and that a relation exists among the symmetry axis, the internal foliation and the crystallographic orientation.     

In-situ particle acceleration in extragalactic radio hot spots: observations meet expectations

We discuss, in terms of particle acceleration, the results from optical VLT observations of hot spots associated with radio galaxies. On the basis of observational and theoretical grounds, the following is shown. (i) Relatively low radio-radio power hot spots are the optimum candidates for being detected at optical waves. This is supported by an unprecedented optical detection rate of 70 per cent out of a sample of low radio power hot spots. (ii) The shape of the synchrotron spectrum of hot spots is mainly determined by the strength of the magnetic field in the region. In particular, the break frequency, related to the age of the oldest electrons in the hot spots, is found to increase with decreasing synchrotron power and magnetic field strength. Both observational results are in agreement with an in-situ particle acceleration scenario.     

Estimation of Fe3+ from electron microprobe analyses: observations on calcic amphibole and chlorite

ABSTRACT Metabasites and metagreywackes from the Pelona and Rand Schists of southern California were analysed using three different electron microprobes. For all three instruments, the estimated Fe³⁺ contents of calcic amphibole, chlorite and epidote are positively correlated. For some samples, there is an additional correlation between high estimated Fe³⁺ and the presence of magnetite. These results imply that microprobe analyses can be used to discern relative differences in Fe³⁺. However, microprobe data and calculations on the sensitivity of the correction procedures to systematic analytical errors indicate that estimated values of Fe³⁺ are not significant in an absolute sense. Thus, estimates of Fe³⁺ are meaningful when comparing samples analysed with a single microprobe, but must be used with caution when comparing analyses obtained on more than one probe.