11:00 AM - 1:00 PM
[PEM10-P12] Characteristics and Causes of Morning side Pc3 Pulsations
Keywords:Magnetic Pulsations, Morning side Pc3, Kelvin-Helmholtz instability
It is known that Pc3 type geomagnetic pulsations occur in the daytime magnetosphere when the solar wind magnetic field is radial. So far, we have investigated the occurrence of Pc3 geomagnetic pulsations on the morning side based on the observation data in 2003 owned by Kyushu University and the following results have been obtained.
1) Although Pc-3 pulsations were distributed in the morning and afternoon around noon,
many Pc-3 pulsations were observed on the morning side.
2) When we investigated the direction of the solar wind magnetic field during the appearance of the morning Pc-3 pulsation occurred, the solar wind magnetic field was directing along the Archimedes Spiral.
This time, we extended the analysis period from 2003 to 2021 and verified the above results. As a result, for the all cases; i.e., 280 cases of Pc3 geomagnetic pulsations observed on the morning side (04 to 08 LT), it turned out that the solar wind magnetic field directing along the Archimedes Spiral.
On the morning and evening Frank side, the solar wind flows along the magnetosphere boundary. At this time, Kelvin-Helmholtz instability grows significantly when it has a large angle close to perpendicular to the magnetosphere boundary. Hence, we consider that the Pc-3 pulsations observed on the morning side are originated from waves generated by Kelvin-Helmholtz instability among the magnetospheric sheath region and invaded the magnetosphere and reached the low latitude equatorial region on the morning side.
In the talk, we will describe the cause of the morning Pc3 pulsation while comparing it with another data observed at stations far away in longitude.
1) Although Pc-3 pulsations were distributed in the morning and afternoon around noon,
many Pc-3 pulsations were observed on the morning side.
2) When we investigated the direction of the solar wind magnetic field during the appearance of the morning Pc-3 pulsation occurred, the solar wind magnetic field was directing along the Archimedes Spiral.
This time, we extended the analysis period from 2003 to 2021 and verified the above results. As a result, for the all cases; i.e., 280 cases of Pc3 geomagnetic pulsations observed on the morning side (04 to 08 LT), it turned out that the solar wind magnetic field directing along the Archimedes Spiral.
On the morning and evening Frank side, the solar wind flows along the magnetosphere boundary. At this time, Kelvin-Helmholtz instability grows significantly when it has a large angle close to perpendicular to the magnetosphere boundary. Hence, we consider that the Pc-3 pulsations observed on the morning side are originated from waves generated by Kelvin-Helmholtz instability among the magnetospheric sheath region and invaded the magnetosphere and reached the low latitude equatorial region on the morning side.
In the talk, we will describe the cause of the morning Pc3 pulsation while comparing it with another data observed at stations far away in longitude.