Study On The Plasma Injection In Magnetosphere

The plasma dispersionless injection is sudden increases of particle ?uxes invarious energy channels during the magnetospheric storm and substorm. Almostall of substorms are accompanied by the plasma injections, which are the mostcommon features of substorms and, more specifically, among the most reliableindicators of substorm onsets. Plasma injections play an important role in un-derstanding the substorm process.The following three aspects are studied in the thesis.1. Two components of drift velocity have been studied in dipole magneticfield, comparing with the results calculated in a dipole magnetic field and theVolland-Stern electric field. Generally, the azimuth component of velocity arecaused by the magnetic gradient and curvature e?ect. If the particle's energy islower than 100keV, the velocity along the azimuth direction caused by the electricfield can not be neglected. The lower energy the particle has, the more a?ectioncaused by electric field. The radial component of velocity mainly depends on theelectric field.Based on the radial injection, a method has been developed which allowsremote sensing of the plasma injection time and the radial distance of injectionboundaries by using measured energy dispersion and modeling particle driftswithin the Volland-Stern electric field and dipole magnetic field model. The radialdistance of the injection boundary deduced from a dispersion event observed byLANL-97A satellite on June. 14, 1998 is 7.1R_E,and the injection time agreeswell with the substorm onset time identified by the Polar Ultraviolet Imager.The method has been applied to an event happened at 22.9 UT on March. 11,1998, when both satellites (1991-080 and LANL-97A) observed the dispersionlesscharacter. The results indicate that the radial distance of injection source for50～75keV particles locate at 8.1R_E and 75～105keV particles locate at 7.9R_E atmagnetotail, they move earthward from magnetotail into inner magnetosphere at 22.5UT.2. The properties of proton (0eV4, Ex turns into zero at 11R_E.The dawn-dusk component of electric field is almost always duskward over themagnetic local time range from 18:00 to 06:00. E_y enhances for L< 6～7 and be- comes week gradually for L> 6～7. The convection electric field ?uctuates around0.4mV/m between L=9 and L=12.Comparing the observations and the results calculated from Volland-Sternelectric field model, Ex component dominates by the corotation electric fieldand the observation convection component does not agree well with the modelresults. The most important is that E_y increases monotonically with the shellvalue L, while the observations has been found that E_y should decrease at acertain distance, which locates at 6～7R_E identified in this work. According tothe di?erences between the observation and model test, we modify the Volland-Stern electric field, and discuss the physics means for the parameters in themodified expression.