Science Seminars

Flux Transfer Events and Kelvin-Helmholtz Waves at Earth’s Magnetopause

Speaker: Jimmy Raeder (University of New Hampshire)
Date: Thursday, Aug 17, 2017
Time: 4:00 PM
Location: SPSC W120

Seminar Abstract:

Flux Transfer Events (FTEs) occur as the result of transient reconnection at the magnetopause. Numerous models have been proposed to explain the formation and subsequent motion of FTEs. Here, we use OpenGGCM simulations of the magnetosphere to show that (a) FTEs form by sequential multiple X-line reconnection, i.e., as a FTE forms, a new X-line develops in its wake, which creates the next FTE; (b) the motion of FTEs is controlled by both dipole tilt angle and by the sign of the IMF By component; and (c) FTEs contain flux of various topologies such that a fully developed FTE contains mostly closed flux. Kelvin-Helmholtz waves (KHW) were believed to be rare and only occurring during times of strong northward IMF and high solar wind speed. Using 7 years of THEMIS observations, we showed that KHW are much more ubiquitous, i.e., occurring 40% of the time under northward Bz, ~10% of the time under southward Bz, and ~20% under any condition. OpenGGCM simulations are consistent with these results.
The SW/IMF conditions for FTEs and KHW overlap somewhat, which makes it often difficult to distinguish between FTEs and KHW in data. We find that at times FTEs can occur in conjunction with KHW, such that large amplitude breaking KH waves are triggered by FTEs and eventually envelope the FTE. This process provides potentially an effective transport mechanism for plasma to enter the tail plasma sheet.