Subjects: Geosciences >> Space Physics submitted time 2017-01-22
Abstract： Based on an extremely disturbed field-aligned electrons event observed with Cluster in the northern cusp region on September 30, 2001, the energy features of the field-aligned electrons in the event was analyzed and the role of the field-aligned electrons on the solar wind energy transfer into the magnetosphere and on the magnetosphere-ionosphere coupling. The results show that the velocities and densities of the electrons have strong disturbances during the event, and the velocity is main factor to enhance the electron flux. The energy spectrum in the 5~200eV and 500~1500eV show that the up-flowing electron flux is higher than down-flowing, which means the up-flowing electrons are from the ionosphere and play a active role in this event. The features of the energy show that the ionospheric electrons have been accelerated during the up-flow. However, the physical mechanism still needs to be further studied.
Peer Review Status:
Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2017-01-22
Abstract： In this paper, the observational investigation shows that the blurred echoes traces, as the expression of occurrence of spread-F, are occurred on the day time at mid-latitude regions based on the analyses of the HF Doppler frequency shift data; Simultaneously, the other ionospheric disturbances accompanied with or immediately before or after or following spread-F are also recorded. The results show that there are several aspects of the characteristics of the daytime spread-F-like phenomena observed by the HF Doppler sounding as following: 1) occurrence time cover almost the whole daytime, such as: the time period of morning, from morning to noon and the time period of afternoon; 2) the morphological features are the blurred echoes traces (similar as the nighttime spread-F), the shifts of which tend to be positive, and sometimes are accompanied by traveling ionospheric disturbances (TIDs) that are not the characteristics of the one generated by typhoon; 3) duration time is much longer, the longest one lasts about five hours; 4) it appears accompanying with the other ionospheric disturbances such as TIDs, solar flare etc.. The characteristics show that the HF Doppler sounding is useful tool for detecting the daytime spread-F-like. Although the daytime spread echoes phenomenon occasionally occur and the occurrence rate is very low, the extensiveness of temporal and spatial distribution of the daytime spread-F-like implies that its effect on the space weather can not be ignored and its properties can not be replaced by the one of the usual spread-F. Therefore, the study of the daytime spread-F-like has very important significance.
Peer Review Status:Awaiting Review
Subjects: Geosciences >> Space Physics submitted time 2016-04-22
Abstract： Using the magnetic field data from Cluster spacecraft and the Interplanetary Magnetic Field (IMF) data from ACE spacecraft, the effect of IMF By component (IMF |By|<10nT) on the Field-Aligned Current (FAC) occurrence rate and density at the Plasma Sheet Boundary Layer (PSBL) in the magnetotail is investigated. 1657 FAC cases from July to October in 2001 and 2004 were selected for analysis. We present that the IMF By component plays a very important role in controlling the occurrence rate and density of the FAC in the PSBL in the magnetotail. The FAC occurrence is higher (about 55.6%) when the IMF By is positive compared with that when the IMF By is negative. When the IMF |By| is more than 4nT, the occurrence rate of FAC is about 77.4%. The FAC occurrence in the magnetotail has an obvious positive correlation with the IMF |By|, and when the IMF By is positive, this correlation is better. The FAC density also has an obvious positive correlation with the IMF |By|, and when the IMF By is positive, this correlation is better. The above results show that the IMF By component has strong control on the occurrence and density of the FAC cases in the magnetotail, and that the change of FAC is closely associated with the duskward IMF (the IMF By is positive).
Peer Review Status:Awaiting Review
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