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A magnetized, spherical plasma expansion in an inhomogeneous plasma: Transition from super‐ to sub‐Alfvénic
Author(s) -
Brecht Stephen H.,
Hewett Dennis W.,
Larson David J.
Publication year - 2009
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 - 10.1029/2009gl038393
Subject(s) - physics , shock wave , plasma , magnetic field , shock (circulatory) , shock waves in astrophysics , longitudinal wave , coupling (piping) , quantum electrodynamics , electromagnetic radiation , wave propagation , classical mechanics , mechanics , computational physics , optics , quantum mechanics , mechanical engineering , engineering , medicine
In this letter the transition of a strong 3‐D collisionless shock into sub‐Alfvénic waves is numerically. The transition occurs due to changes in the background plasma parameters. The Alfvén speed eventually exceeds the shock speed; the shock does not run out of energy. At this velocity transition, the shock disassembles into two types of waves: the usual compressional Alfvén wave and a left‐hand polarized electromagnetic shear Alfvén wave. This latter wave shows remarkable 3‐D coherence, and preliminary analysis suggests that there are two possible sources of energy: one is coupling to the strong electromagnetic waves that exist within the collisionless shock and the other is the density and magnetic field gradients at the interface.