Abstract: This paper examines a possible mechanism for the initiation of coronal mass ejections by means of the eruption of magnetic flux beneath a closed magnetic structure analogous to a coronal helmet structure. Anumerical computation shows that such an eruption deforms the helmet structure into an expanding bright "loop", followed by a dark cavity due to the expansion of the erupted magnetic field. The morphology and the internal structure of the loop are mainly determined by the background magnetic field whereas its ejective speed is largely controlled by the rate of flux ejection. The present model identifies the loop-like mass ejections with the above plasma structures moving with the frozen-in magnetic field and it may well explain some general properties of such ejections.
Abstract: Two-dimensional hydrodynamic description is used to study how the solar wind parameters observed at 1 AU, are influenced by the different conditions near the sun and interplanetary corotating interactions. The results show that a perturbation of velocity rather than temperature or density in the propagation region beyond 0.1 AU imposed much greater influence to the solar wind structure.It is unlikely that the corotating interaction would result in the anticorrelation between the solar wind velocity and Mach number as shown by the statistical values averaged over the solar cycle 20.
Abstract: An analysis of the properties of soft and hard X-ray flux distribution in solar flares observed by GOESand SMMsatellites shows that there are two distinct kinds of solar flare, i.e. the prominent thermal and non-thermal events. The main characteristics for these two kinds of event are: (1) the prominent thermal event is consisted of gradual type flares, while the prominent non-thermal event is impulsive ones; (2) the energy spectrum of hard X-ray is relatively "soft" for the prominent thermal event and "hard" for the non-thermal event; (3) the releasing rate of non-thermal energy for the prominent non-thermal event is 3-10 times larger than that for the thermal events; (4) for the prominent thermal event it seems that the slower is the evolution of flares, the larger is the peak flux of soft X-rays; (5) the prominent thermal and non-thermal events constitute respectively 40% and 60% of the solar flares. Finally, the possible mechanism responsible for the prominent thermal and non-thermal events is discussed.
Abstract: In this paper, a statistical analysis is made on VHF/UHF amplitude scintillations and VHFfast Faraday rotation fluctuations by the recordings of the 136 MHz beacon signal from the Japanese satellite ETS-II at 130.0°Eand the 714 MHz television signal from Soviet geostationary station-T at 99.0°Eobtained at Wuchang during the period September 1988 through May 1989. It is shown that nighttime scintillations appear to have an essentially equatorial nature toward the time of maximum solar activity, and the occurrence of VHF/UHF scintillations reaches its' maximum near two equinoxes. The irregularities producing these phenomena seem to drift from west to east with a speed of about 14 m/s in the pre-midnight hours and of about 90 m/s in the post-midnight hours.
Abstract: The observation results of Iss-b satellite show that ionospheric ion abundances vary with longitudes. The most realistic ionospheric electron density models are selected to trace whistler rays of low latitudes in 130°Eand 114°Emeridian planes. The computational results show that the longitudinal variations of vertical gradients of electron density controlled by [O+] , [He+] and [H+] result in the longitudinal effect of whistler propagation. Low latitude whistlers in 130°Esatisfy the penetrating condition |μsinδ |≤1 better than that in 114°E. It is found that the influence of longitudinal variation of vertical gradients of electron density controlled by ion abundances is greater than that of horizontal gradients of electron density controlled by equatorial anomaly. The observed whistler occurrence rates at Wuchang (30.5°N Geog., 114.6°E; 19.3°N Geom) and Kagoshima (31.5°N, 130.8°E; 20.5°N) are in good agreement with the theoretical predictions in this paper.
Abstract: Based on the analysis about the effects on the visibility function caused by the Faraday rotation, the multi-source observations and the errors in path difference compensation, it is confirmed, in this paper, that only the phase induced by the ionospheric irregularities with scale sizes larger than the base line length, is proportional to the base line length, and is characterized by rapid time variations. Then a statistical method to extract informations about ionosphere from metre wave radio astronomical observations is provided, and the character of this method is analysed, some statistical examples are given also.
Abstract: In this paper, resonant reflection of the ordinary wave propagating perpendicular to background magnetic field by periodic standing wave of plasma density is studied. The resonant reflection mechanism is able to explain strong scattering of VHF/UHF radar in ESF conditions.
Abstract: The northern crest of the equatorial anomaly covers Southern China, therefore, the investigation of the ionospheric features of equatorial anomaly at crest is the key for understanding ionospheric characteristics over China. In this paper, 6 related topics are reviewed: 1. Day-to-day variations and the post sunset enhancement of the equatorial anomaly; 2. The movement of the crest; 3. Longitudinal structure of the equatorial anomaly; 4. Intensitive scintillation and fast Faraday fading caused by bubble effects; 5. The ionization ledges in the topside ionosphere and the neutral anomaly; 6. Low-latitude electron precipitation, which is symmetric to the magnetic equator.
Abstract: Using the data of 100 kHz low frequency radio wave (Loran-Csignal), the nighttime integral electron density in the ionosphere below 100 km at low latitude are calculated, and the cause of this variations are analyzed under various magnetic disturbances during 1986-1987.The results show: In the lower ionosphere at low latitudes, the nighttime variations of electron density are related to geomagnetic disturbances. The electron density are smaller, and changing following geomagnetic disturbance in one or two days during geomagnetic quiet days. The electron density are larger during and after magnetic storms. The fluctuation of the integral electron density in this region can be one order greater, it reaches peak value in 2-3 days after a magnetic storm. The bremsstrahlung radiation produced by the precipitating electrons may be a main factor which causes the nighttime variations of electron density in the lower ionosphere at low latitudes.
Abstract: During taking the solar Ha monochromatic images by CCD system, some regular interference fringes often appeared on the image. Afeasible method of getting a pure image of the interference fringes and removing the interference fringes from Hα solar image in realtime in the process of collecting image is presented in this paper.
