Browsing by Author "Chen, Chuxin"
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Item Earthward motion of depleted flux tubes in the Earth's plasma sheet: MHD model calculations(1995) Chen, Chuxin; Wolf, Richard A.A magnetohydrodynamic (MHD) theory has been developed for the motion of a thin magnetic flux tube through a two-dimensional stationary medium that is in MHD equilibrium. The flux tube is represented as a one-dimensional filament. Simple properties of the computed time development of the filament have been explored analytically, including linear intermediate and slow-mode waves and corresponding MHD shock solutions. Numerical solutions for filaments in the tail display the strong earthward flow and dipolar shapes that are characteristic of bursty bulk flows that are frequently observed in the plasma sheet of the Earth's magnetosphere.Item Interpretation of high speed flows in the plasma sheet(1994) Chen, Chuxin; Wolf, Richard A.We propose that the "bursty bulk flows" are "bubbles" in the Earth's plasma sheet. Specifically, they are flux tubes that have lower values of $pV\sp{5/3}$ than their neighbors, where p is the thermal pressure of the particles and V is the volume of a tube containing one unit of magnetic flux. Whether they are created by reconnection or some other mechanism, the bubbles are propelled earthward by a magnetic-buoyancy force, which is related to the interchange instability. Most of the major observed characteristics of the bursty bulk flows can be interpreted naturally in terms of the bubble picture. We propose a new "stratified fluid" picture of the plasma sheet, based on the idea that bubbles constitute the crucial transport mechanism. Results from simple mathematical models of plasma-sheet transport support the idea that bubbles can resolve the pressure-balance inconsistency.