A phase locking mechanism for nongyrotropic electron distributions upstream of the Earth's bow shock





Citation of Original Publication

Gurgiolo, C., M. L. Goldstein, Y. Narita, and K.-H. Glassmeier (2005), A phase locking mechanism for nongyrotropicelectron distributions upstream of the Earth’s bow shock, J. Geophys. Res., 110, A06206, doi:10.1029/2005JA011010.


This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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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.