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On the propagation of blobs in the magnetotail: MHD simulations
Author(s) -
Birn J.,
Nakamura R.,
Hesse M.
Publication year - 2013
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/jgra.50521
Subject(s) - physics , magnetohydrodynamics , magnetohydrodynamic drive , vorticity , mechanics , magnetic field , magnetic flux , breakup , entropy (arrow of time) , turbulence , perturbation (astronomy) , classical mechanics , computational physics , vortex , quantum mechanics
Using three‐dimensional magnetohydrodynamic (MHD) simulations of the magnetotail, we investigate the fate of entropy‐enhanced localized magnetic flux tubes (“blobs”). Such flux tubes may be the result of a slippage process that also generates entropy‐depleted flux tubes (“bubbles”) or of a rapid localized energy increase, for instance, from wave absorption. We confirm the expectation that the entropy enhancement leads to a tailward motion and that the speed and distance traveled into the tail increase with the entropy enhancement, even though the blobs tend to break up into pieces. The vorticity on the outside of the blobs twists the magnetic field and generates field‐aligned currents predominantly of region‐2 sense (earthward on the dusk side and tailward on the dawn side), which might provide a possibility for remote identification from the ground. The breakup, however, leads to more turbulent flow patterns, associated with opposite vorticity and the generation of region‐1 sense field‐aligned currents of lower intensity but approximately equal integrated magnitude.