Turbulent magnetic field in the distant magnetotail: Bottom‐up process of plasmoid formation?

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 slop...

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Bibliographic Details
Published inGeophysical research letters Vol. 21; no. 25; pp. 2935 - 2938
Main Authors Hoshino, M., Nishida, A., Yamamoto, T., Kokubun, S.
Format Journal Article
LanguageEnglish
Published American Geophysical Union 15.12.1994
Blackwell Publishing Ltd
Subjects
Fluid dynamics
Fluid flow
Magnetic fields
Magnetic reconnection
Magnetospheric Physics
Magnetotail
Plasma sheet
Plasmoids
Signatures
Space Plasma Physics
Spectra
Turbulence
Turbulent flow
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Summary: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 Bz 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 Bz magnetic field component, although the spectral feature in the lower frequency regions exhibits differences in appearance. When there is no bipolar signature on Bz 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.
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ArticleID:94GL02094
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SourceType-Scholarly Journals-1
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ISSN:0094-8276
1944-8007
DOI:10.1029/94GL02094