Science Seminars

10/22/2015 – The Role of Flux Tube Entropy in Earth’s Plasma Sheet

Speaker: Richard Wolf (Rice Univ.)
Date: Thursday, Oct 22, 2020
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

The plasma sheet is a crucial region of Earth’s magnetosphere, providing a source of the aurora, the substorm, and the storm-time ring current, as well as a seed population for the outer radiation belts. I will argue that flux-tube entropy, interchange instability, and reconnection all play crucial roles in plasma-sheet structure and dynamics. In the 1960s and 1970s, theorists tended to visualize the plasma sheet as undergoing more-or-less-uniform sunward convection, though with fluctuations. As the modeling based on that picture became more rigorous, it became clear that it was in conflict with average observations. Starting with the discovery of bursty bulk flows in the 1990s, the uniform-sunward-convection picture has gradually been replaced by a picture in which most of the sunward transport takes place in localized regions of fast flow and low flux-tube entropy. Recent work with the Rice Convection Model-Equilibrium code (RCM-E) has concentrated on modeling various types of situations (sawtooth events, substorm growth and expansion, storm main phase, long-term averages), with emphasis on exploring the effects of changes in flux tube entropy and associated interchange instability. A final topic will be the buoyancy oscillations that occur in interchange-stable regions of the magnetosphere, oscillations that turn out to be very similar to the buoyancy oscillations that occur in convectively stable regions of Earth’s atmosphere.