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*–ì˜a“c Šî°[1], Œüˆä —˜“T[1], ŸNˆä ‹œ[2]
“ŒŠC‘åŠw@HŠw•”@q‹ó‰F’ˆŠw‰È[2]
Plasma Characteristics within Three Type Structures of dayside Magnetopause Current Layer under Northward and Southward IMF
*Motoharu Nowada[1]
,Toshifumi Mukai [1],Tohru Sakurai [2]
Institute of Space and Astronautical Science[1]
Department of Aeronautics and Astronautics, Tokai Univ.[2]
Although hot and cold plasmas (ion and electron) originated from both magnetosphere and magnetosheath coexist within or more inner side of dayside magnetopause current layer (MPCL), these plasmas are not always mixing constantly. The condition of mixture varies due to IMF orientation and the location of dayside MPCL. Then, we noticed whether the low energy ion and electron from the magnetosheath are mixing with the magnetospheric plasmas in outer edge of magnetosphere and found that three types for plasma mixing exist. From this result, we categorized 64 plasma energy - time spectrograms (E-t diagram) when GEOTAIL was crossing the dayside MPCL during 1.5 years from August 1995 to February 1997 into three plasma structures by mixing type of cold plasma in outer magnetosphere. Before categorizing data, we defined the criteria of the typical plasma energy (temperature) range of ion (Ti) and electron (Te) in the magnetosheath and magnetosphere (not shown). Moreover, when population more than 30 [Counts/Samples] of both ion and electron from the magnetosheath was observed in outer edge of magnetosphere on E-t diagram, we identified that the magnetosheath cold plasmas were mixing with the magnetospheric hot plasmas. Under these criteria, collected 64 samples are categorized into three plasma structures (Type-I,-II and -III). In addition to this, using the magnetic field and plasma moment data during same term when E-t diagrams were collected, we examined how the plasma particle and energy were transported within three type dayside MPCL and whether these transports really varies due to the IMF Bz orientation. These results were shown with a following figure. Regardless of the IMF orientation, the low energy plasma less than 500 [keV] within three-type dayside MPCL were almost transported tailward (-Vm). In Type-I and -III MPCL, however, this cold plasma was transported sunward (+Vm) in the cases of both northward and southward IMF. This result indicates that the magnetic reconnection that took place when IMF was northward or southward plays an important roll for the formation of plasma structure at the dayside MPCL. But the reconnection did not always concern to the MPCL plasma structure formation as shown in the case of Type-II MPCL. In the presentation of this meeting, we will also discuss about the thickness of three types dayside MPCL.
