Coordinated Satellite And Ground-based Observations Of Magnetic Reconnections On The Dayside Magnetopause

The dayside magnetopause boundary layer is the key region for the solar wind-magnetosphere coupling and interaction. Solar wind plasma can easily cross this region to transfer mass, momentum and energy into the magnetosphere. One of the most important ways of these transferring processes is the magnetic reconnection. Based on the good geographic locations of magnetic conjugate between Chinese Zhongshan Station in Antarctic and Yellow River Station in Arctic, this thesis coordinated Cluster/Double Star (TC-1 and TC-2), Super Dual Auroral Radar Network (SuperDARN) and EISCAT radar observations for five selected cases of the magnetic reconnections on the dayside magnetopause during southward or northward interplanetary magnetic field (IMF). The five cases were analyzed in some detail for trying to reveal the evolutions and physical characteristic of the flux transfer events (FTEs) originated by the magnetic reconnections on the dayside magnetopause.Under southward IMF (BZ<0) condition, this thesis analyzed the observations of the flux gate magnetometer (FGM) and PEACE instruments onboard the Cluster/TC-1 Spacecraft, and the EISCAT and SuperDARN radars between 11:48 and 13:00 UT on 1 April 2004, 09:00 and 12:00 UT on 11 February 2004, and 12:00 and 12:40 UT on 13 March 2004. The magnetic field data are expressed in local boundary normal coordinates (LMN), which have been found by performing minimum variance analysis (MVA) on the local magnetopause crossing of Cluster 3 and TC-1. Combining with the electron spectrograms data from the PEACE instrument onboard Cluster/TC-1, it is shown that a series of FTEs, which originated from the low-latitude magnetic reconnections on the dayside magnetopause, was observed before and after the magnetopause crossing of Cluster/TC-1. These FTEs appeared quasi-periodically.We applied the four-spacecraft techniques of"Minimum Directional Derivative (or Difference)"(MDD) and"Spatio-temporal Difference"(STD) to calculate the dimension, motion and scale of these FTEs. With a quasi-2-D structure and a scale of 0.60~1.05RE with the current density reaching as high as about 10-7A/m2, the inferred northwardly reconnected flux tubes for these FTEs are shown to move northward, duskward (or downward) and tailward, which consistent with the expected motion of the reconnected magnetic flux tubes by running the Cooling model. It is found that there was one pair of FTEs which might be originated from the same reconnection X-line (the FTE connected to the northern cusp was observed by Cluster, and the one connected to the southern cusp was observed by TC-1) for the case of 11 February 2004. Using the Cooling model to predict the motions of the above pair of FTEs and comparing the expected motion with the motion observed by Cluster, this thesis inferred the motion of FTE measured by TC-1, and found that the speed and scale of the FTEs were increasing with its tailward motion.The motions of these FTEs are good corresponding with the"poleward-moving radar auroral forms"(PMRAFs) (or"pulsed ionospheric flows"(PIFs)) observed by CUTLASS (or Stokkseyri) SuperDARN radar, and also corresponding with the bursts of poleward flow and low-energy electron precipitation recorded by the EISCAT radars. Furthermore, the motion direction of the FTEs observed by Cluster/TC-1 and the expected flux tubes predicted by Cooling model are temporally correlated with clear velocity enhancements in the ionospheric convections conjugate measured by SuperDARN radar in both hemispheres. The duration of these velocity enhancements imply that the evolution time of the FTEs is about 4-8 minutes from its origin on magnetopause to its addition into the polar cap. However, the ionospheric response time was different in each hemisphere. This suggests the reconnection site is located southward (or northward) of the subsolar region.Under northward IMF (BZ>0) condition, this thesis also analyzed the simultaneous observations of the FGM and PEACE instruments onboard the Cluster Spacecraft, the CUTLASS SuperDARN radar and the all sky imager at Chinese Yellow River Station in Ny-?lesund, Arctic during 09:00-10:00 UT on 26 March 2004 and 09:00-14:00 UT on 11 January 2005. Combining the magnetic field data expressed in LMN coordinates with the electron spectrograms data from the PEACE instrument onboard Cluster 1, it is shown that a series of high-latitude lobe reconnection signatures were observed, with clear accelerating and mixing of magnetosheath and magnetospheric plasma populations. These magnetic reconnection signatures might be originated by the high-latitude/lobe reconnection on the dayside magnetopause. A series of"equator-ward moving radar auroral forms"(EMRAFs) and enhanced sunward flows were observated by CUTLASS SuperDARN radar. The durations of the flow enhancements is about 8 minutes, suggested that the evolution time of the magnetic lobe reconnections is about 8 minutes from its origin on magnetopause to its addition into the polar cap. The optical aurora measurements showed that the observational ionospheric region was good response to the magnetopause reconnections. The regions of the aurora brightening were much dependent on the IMF clock angle. The low-altitude particle precipitation, observed by the Defense Meteorological Satellite Program (DMSP) F13, are presented to show the intense magnetosheath-like electron precipitation and a stepped ion dispersion signature, which are the good response to the pulse magnetopause reconnections (FTEs) and the boundary structure crossing. The plasma flow measurements by F13 were consistent with the motion of the FTE (originated by lobe reconnection) observed by Cluster and the trending of the aurora motions in the corresponding regions of the observation from the all sky imager at Chinese Yellow River Station.The magnetic reconnections on the dayside magnetopause and their dynamic effect are quite complicated. This thesis only detailedly analyzed and studied five typical cases. Although this thesis revealed some new structures and phenomena, and formed some new understanding, the global configurations of the magnetic reconnections on the dayside magnetopause, the 3-D geometry structure of magnetic reconnections, and the ionosperic response to the dayside magnetic reconnection in polar region still remain to be further analyzed and studied.