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Pc1 pulsations observed by AMPTE/CCE in the Earth's outer magnetosphere
Author(s) -
Anderson B. J.,
Takahashi K.,
Erlandson R. E.,
Zanetti L. J.
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i011p01853
Subject(s) - magnetosphere , physics , plasmasphere , ring current , earth's magnetic field , geophysics , plasma sheet , magnetopause , cyclotron , van allen radiation belt , convection , van allen probes , astrophysics , magnetic field , atomic physics , plasma , meteorology , nuclear physics , quantum mechanics
Electromagnetic ion cyclotron waves in the Pc1–2 frequency range (0.1–5 Hz) have been observed in Earth's equatorial magnetosphere over the range L =3 to 9 by the AMPTE/CCE magnetic fields experiment. We report detailed analysis of data from two orbits together with preliminary occurrence statistics from 31 days. One example occurred during disturbed geomagnetic conditions (maximum AE>1000 nT) and exhibited intense Pc1 from L =5 to the magnetopause ( L ≈7.5). The second example occurred during moderate to quiet conditions (average AE≈300 nT) and displayed Pc1 in two distinct L ranges: low ( L ≈4) and high ( L >7,5). Statistical results show that Pc1 are ≈4 times more common for L >7 than for L <6 and occur primarily in the afternoon. The discovery of a statistically dominant outer magnetospheric source region implies that ring current interaction with the plasmasphere is not the primary source of Pcl excitation but suggests that plasma sheet ions may be a significant energy source for Pc1. This result is consistent with the strong dependence of the linear convective growth rate on magnetic field strength.