Open AccessA phase locking mechanism for nongyrotropic electron distributions upstream of the Earth's bow shock
Author(s) -
Gurgiolo C.,
Goldstein M. L.,
Narita Y.,
Glassmeier K.H.,
Fazakerley A. N.
Publication year - 2005
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2005ja011010
Subject(s) - bow shock (aerodynamics) , physics , whistler , bow wave , electron , phase (matter) , shock wave , geophysics , distribution function , magnetic field , computational physics , plasma , atomic physics , mechanics , solar wind , quantum mechanics
Observations of nongyrotropic electron distributions in the region upstream of the Earth's bow shock suggest that there exists a mechanism to lock in their phase, otherwise they would rapidly gyrophase mix into a ring‐beam distribution. Measurements by the Plasma Electron and Current Experiment (PEACE) on the Cluster spacecraft have provided a way of determining the rotational period of a nongyrotropic electron distribution. For the time period studied, the rotational period is found to be ≈0.5 Hz, significantly lower than the local Larmor frequency but in line with the frequency of waves observed in the local magnetic field. Detailed wave analysis has revealed that the waves are most likely ordinary right‐hand whistler waves. The conclusion is that the waves provide the necessary phase locking mechanism. It is not clear whether those waves are generated by the nongyrotropic distribution or are produced by other means and then cause the observed nongyrotropy.