Researches Of Substorm Onsetand Plasma Sheet Inner Boundary

The magnetospheric substorm is an important energy release process in the magnetosphere, which include ionospheric substorm, auroral substorm, magnetic substorm and thermospheric substorm. The plasma sheet (PS), located in the center of magnetotail, is an import source of hot plasma,. The injection of plasma sheet ions to the inner magnetosphere plays an important role during magnetospheric substorms and geomagnetic storms.The present thesis first the onset of substorm at the very beginning. The westward electrojet AL index, substorm electrojet AE index and field-aligned current AF index in 2004 are used to identify substorm onset times. The results are then compared with substorm auroral onsets. We found that if auroral onsets are chosen as zero time, then the average AL, AE, AF onset times are 0.5, 0.5, and -0.1 min. The most possible AL onset is at the same time as auroral onset, but that is 1 min before for AE and AF onsets. The substorm onsets got by geomagnetic indices get closer to auroral onset with more intense substorm activities. For the 5 super substorms, AL and AE onsets are both before auroral onset. It is indicated that for intense substorm, electrio jet will increase before auroral breakup.In the past, the theoretic studies of plasma sheet ion injections were all conducted by the adiabatic drift path theory in which the magnetic moments of particles are kept constant. We extend the previous particle drift theory described by constant magnetic moment in the (U,B) coordinate to the particle drift theory described by contant energy. Then, we discuss the characters of different energy particles'boundary between their open and close drift path and its variation with Kp index during their motions to the Earth. For high energy particles, the radial distance to the Earth of plasma sheet ions'boundary increase with increasing energy, and the distance in dawn side is much larger than that in dusk side. But for lower energy particles, such thing will completely change. The radial distance decreases with ion energy and the radial distance in dusk sector is larger than that in dawn side. Our simulation results also show that with the increase of Kp index, all boundaries of various energy particles in the plasma sheet move towards the Earth. But performances of ion boundaries in high and low energy ranges are different. For low energy particles, the inner boundary shape of ions almost keeps constant with the increase of Kp index. For high energy spartcile, their shapes change remarkably with Kp index. In two extreme cases, where, E=20keV, Kp=6 and E=10keV, Kp=3, the ion boundaries even show two different regions, one is the closed circle region around the Earth and the other is the isolated region in dawn side. The boundary of plasma sheet certain- energy-E particles is just the positions of energy-E point in various magnetic moments Alfven layer.Then, on the basis of the theory of particle dynamics, we simulated the variation of the plasma sheet inner boundary with Kp index by calculating the drift orbit of each particle. In the situation of static state fixed Kp, this method gets the same result as the former (U, B) coordinate translating method. But the value of our single particle drift orbit method is to simulate the dynamic variation of PSIB with the changing of Kp index. After all, the Kp index is changing all the time. Unless we can describe the dynamic change of the PSIB, the simulation results can't be compared with satellites'data accurately.As an observed confirmation of the simulation results, we researched the relation between geomagnetic activities and PSIB, using the data of TC-1's HIA in 2004-2005. It was found that the boundary is nearer to the earth with smaller AE/Kp values but further with larger AE/Kp, and most of the boundary points are in the range of 5-7 RE , just like our simulation results. At the same time we find that different phases of substorm can affect the boundary, too. Most boundary points are further away from the earth in quite time/increasing phase than in explosive/recovery phase.