Premium
High‐latitude Pi2 pulsations associated with kink‐like neutral sheet oscillations
Author(s) -
Wang G. Q.,
Volwerk M.,
Zhang T. L.,
Schmid D.,
Yoshikawa A.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2016ja023370
Subject(s) - oscillation (cell signaling) , quasiperiodic function , physics , current sheet , instability , plasma sheet , current (fluid) , latitude , ionosphere , substorm , geophysics , magnetic field , mechanics , magnetosphere , condensed matter physics , chemistry , magnetohydrodynamics , quantum mechanics , astronomy , thermodynamics , biochemistry
A kink‐like neutral sheet oscillation event observed by Cluster between 1436 and 1445 UT on 15 October 2004 has been investigated. The oscillations with periods between 40 and 60 s, observed at (−13.1, 8.7, −0.5) R E , are dominant in B X and B Y . And they propagate mainly duskward with a velocity of (86, 147, 46) km/s. Their periods and velocity can be explained by the magnetic double‐gradient instability. These oscillations are accompanied by strong field‐aligned currents (FACs), which prefer to occur near the strongly tilted current sheet, and local maximum FAC tends to occur near the neutral sheet. The FACs show one‐to‐one correlated with a high‐latitude Pi2 pulsation event recorded by KTN and TIK stations with a delay time of ~60 and 90 s, respectively. Both the Pi2 and oscillations propagate westward with a comparative conjunctive speed. These findings suggest a strong relation between the FACs and Pi2, and we infer that the Pi2 is caused by the FACs. The periods of the FACs are modulated by the oscillations but not exactly equal, which is one possible reason that the period of the Pi2 caused by the FACs could be different from the oscillations. We speculate that a current circuit between the plasma sheet and ionosphere can be formed during strongly tilted current sheet, and successive tilted current sheet could generate quasiperiodic multiple FAC systems, which can generate high‐latitude Pi2 pulsations and control their periods.