1998 Fiscal Year Final Research Report Summary
Solar source of non-spiral interplanetary magnetic field
| Project/Area Number |
09640533
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Space and upper atmospheric physics
|
|---|
| Research Institution | Tohoku Institute of Technology |
|---|
Principal Investigator |
NAKAGAWA Tomoko Tohoku Institute of Technology Communication Engineering Associate Professor, 工学部・通信工学科, 助教授 (40222161)
|
|---|
| Project Period (FY) |
1997 – 1998
|
| Keywords | interplanetary magnetic field / interplanetary space / planar magnetic structures / SAKIGAKE / GEOTAIL / solar wind / velocity distribution function / tangential discontinuity |
|---|
| Research Abstract |
Non-Parker type interplanetary magnetic field comes from non-static source on the Sun, and is expected as a key that relates solar wind and its solar source. As has been recognized in the Yohkoh soft X-ray images, there are various activities on the photosphere which release ejecta into interplanetary space. It is difficult to identify all the interplanetary counterparts of the ejecta because they can be easily missed by point observation from interplanetary spacecraft. It is more convenient to examine non-spiral magnetic field in interplanetary space and then to investigate their relationship to the solar phenomena.
In this study, non-Parker type interplanetary objects, planar magnetic structures, have been examined by using magnetic field and low-energy particle data obtained by GEOTAIL spacecraft. In a planar magnetic structure, magnetic field vectors are all parallel to a plane that is inclined to the ecliptic plane. Previous study showed that the sources often coincided with expanding ioops from active regions. In order to examine their magnetic connection to the photosphere, angular distribution of low-energy electrons in planar magnetic structures were examined by using Low Energy Particle(LEP) experiment onboard GEOTAIL.Bidirectional electrons characteristic of closed field lines were not found in planar magnetic structures.
Previous studies suggested that the jumps in magnetic field were tangential discontinuities, however, velocity jumps had not been investigated because of lack of high-time resolution observation of the solar wind velocity. In this study, GEOTAIL/LEP data were used to calculate velocity component Vn normal to the plane of the structure and the propagation speed U of the discontinuity surface. It resulted in that the jumps were tangential discontinuities in which the speed U was equal to Vn.
|
