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Pulsations of auroral kilometric radiation at Pc1 frequencies
Author(s) -
Hanasz Jan,
Schreiber Roman,
Pickett Jolene,
de Feraudy Hervé
Publication year - 2008
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 - 10.1029/2008gl034609
Subject(s) - physics , magnetosphere , cyclotron , maser , earth's magnetic field , electromagnetic radiation , geophysics , magnetic field , instability , electron , geomagnetic storm , computational physics , atomic physics , astrophysics , optics , nuclear physics , quantum mechanics , mechanics
Cases of AKR pulsations at frequencies 1 to 4 Hz, typical for Pc1 geomagnetic pulsations, were observed from four Cluster spacecraft. 15 events were found in years 2001–2005, with 14 occurring in a recovery phase of a strong magnetic storm. In a studied event of 22 June 2003 the AKR pulses show positive frequency drifts, corresponding to the earthward motion of AKR sources along auroral magnetic field lines. The source velocities match calculated propagation of shear Alfvén waves within the auroral cavity. In our scenario a primary cause of the AKR Pc1 pulsations can be inertial Alfvén waves converted either from electromagnetic ion cyclotron waves generated in the equatorial magnetosphere, or from electromagnetic ion cyclotron waves generated in the auroral cavity. We suggest that the parallel electric field of the earthward propagating wave can periodically produce the ‘shell’ electron distribution, which could be the free energy source of the AKR pulse emission through the electron‐cyclotron maser instability.