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Turbulent magnetic field in the distant magnetotail: Bottom‐up process of plasmoid formation?
Author(s) -
Hoshino M.,
Nishida A.,
Yamamoto T.,
Kokubun S.
Publication year - 1994
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 - 10.1029/94gl02094
Subject(s) - plasmoid , physics , magnetic field , magnetic reconnection , turbulence , current sheet , computational physics , magnetohydrodynamics , mechanics , quantum mechanics
The GEOTAIL magnetic field observations in the earth's magnetotail are examined in terms of a turbulent magnetic reconnection process. It is found that the observed Fourier power spectral density of the turbulent magnetic fields can be approximated by a power‐law spectrum which changes its slope around a turnover frequency with 0.04 Hz, in spite of the differences among a wide variety of magnetic perturbations observed in the distant magnetotail plasma sheet. The turbulent magnetic field data are classified into two cases (Nishida et al. in this issue): one is accompanied with a plasmoid bipolar signature on B z magnetic field, and the other without the bipolar signature. The higher frequency regions above the turnover frequency always show similar spectral slope in the cases with and without a bipolar signature in B z magnetic field component, although the spectral feature in the lower frequency regions exhibits differences in appearance. When there is no bipolar signature on B z magnetic field, the lower frequency range is almost a flat spectrum. On the other hand, the slope of the lower frequency region becomes steep when a large scale bipolar signature is observed. The observations may indicate that 1) a small‐scale tearing mode vortex with the scale of plasma sheet thickness is excited in the magnetotail, and 2) the large‐scale plasmoid is coalescently formed from the small‐scale tearing mode vortices.