IGPP Seminar Series

Dynamical Effects of Plasma-Sheet Inhomogeneities

by Richard Wolf
Rice University, Space Physics


The plasma sheet, which consists of kilovolt plasma on closed magnetic field lines, is arguably the most important region of Earth's magnetosphere. Though early theories visualized the plasma sheet as approximately uniform, it is clear that meso-scale inhomogeneities play a key role in the physics of the region. Four topics related to these inhomogeneities will be covered: (1) Two basic sets of fluid equations that can usefully be applied to the plasma sheet, specifically magnetohydrodynamics and the quasi-static approximation to it, will be reviewed. Particular attention will be paid to expressions for the entropy of a magnetic flux tube. (2) Simulations of the motion of thin, ideal-MHD filaments will be used to study the motion of low-entropy bubbles through the plasma sheet. Bubbles seem to be related to bursty bulk flows, poleward boundary intensifications, and possibly micropulsations, and they may control the overall structure of the plasma sheet. (3) A superposed-epoch study will be described that clarifies the characteristic time variation of the entropy parameter in substorm expansions, convection bays, and pseudo-breakups. (4) Quasi-static and full-MHD simulations will be presented that illustrate a process in which a localized current disruption on stretched, closed field lines seems to lead to creation of a bubble/blob pair, localized thinning of the plasma sheet, and reconnection.
Tuesday, 30 March 2010
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM