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Evidence on a Class of Azimuthally Propagating Dipolarization Structures in the Earth's Magnetosphere from 4 to 30 Re
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  • Sheng Tian,
  • Cynthia A. Cattell,
  • John Wygant,
  • Vassilis Angelopoulos,
  • Geoffrey D. Reeves
Sheng Tian
University of Minnesota

Corresponding Author:[email protected]

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Cynthia A. Cattell
University of Minnesota
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John Wygant
University of Minnesota
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Vassilis Angelopoulos
University of California Los Angeles
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Geoffrey D. Reeves
Space Science and Applications Group, Los Alamos National Laboratory, Los Alamos, New Mexico, USA.
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Abstract

We report observational evidence for a class of coherent magnetic dipolarization structures that are long lived and radially extensive. The reported dipolarization structures, a subset of general dipolarizations, typically remain coherent over 20-30 min in real time, 3-6 hours in MLT, and 10-20 Re in radial distance. Arrays of more than three spacecraft in non-collinear geometry are used to determine the propagation vector, including both the normal speed and direction, of such dipolarizations in the equatorial plane. The determined azimuthal propagation is ~3 deg/min, which corresponds to ~50 km/s at 6.6 Re. This speed is consistent with those obtained from two azimuthally separated spacecraft in previous works. Further analysis suggests that these azimuthally propagating dipolarizations (APDs) are often finger-like in shape, ranging from 5 to 20 Re in length and several Re in width. The reported APD may accompany the earthward flow channel and dipolarizing flux bundle (DFB).