Pi2 Pulsations During Extremely Quiet Geomagnetic Condition: Van Allen Probe Observations
A ultra low frequency (ULF) wave, Pi2, has been reported to occur during periods of extremely quiet magnetospheric and solar wind conditions. And no statistical study on the Pi2 has been performed during extremely quiet conditions, using satellite observations to the author’s knowledge. Also Pi2 p...
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Korean Space Science Society (KSSS)
2017-06-01
|
| Series: | Journal of Astronomy and Space Sciences |
| Subjects: | |
| Online Access: | http://ocean.kisti.re.kr/downfile/volume/kosss/OJOOBS/2017/v34n2/OJOOBS_2017_v34n2_111.pdf |
| Summary: | A ultra low frequency (ULF) wave, Pi2, has been reported to occur during periods of extremely quiet magnetospheric and solar
wind conditions. And no statistical study on the Pi2 has been performed during extremely quiet conditions, using satellite
observations to the author’s knowledge. Also Pi2 pulsations in the space fluxgate magnetometers near perigee failed to attract
scientist’s attention previously. In this paper, Pi2 pulsations detected by the Van Allen probe satellites (VAP-A & VAP-B) were
investigated statistically. During the period from October 2012 to December 2014, ninety six Pi2 events were identified using
VAP when Kp = 0 while using Kakioka (KAK, L = 1.23) as a reference ground station. Seventy five events had high coherence
between VAP-Bz and H components at KAK station. As a result, it was found that 77 % of the events had power spectra between
5 and 12 mHz, which differs from the regular Pi2 band range of from 6.7 to 25 mHz. In addition, it was shown that it is possible
to observe Pi2 pulsations from space fluxgate magnetometers near perigee. Twenty two clean Pi2 pulsations were found where
L < 4 and four examples of Pi2 oscillations at different L shells are presented in this paper. |
|---|---|
| ISSN: | 2093-5587 2093-1409 |