CLaSP Seminar Series - Professor Stuart Bale
Date: January 12, 2017
Time: 3:30 pm - 4:30 pm
Location: Space Research Building Auditorium, Room 2246
Professor Stuart Bale, Director of the UC Berkeley Space Sciences Laboratory, will give a special seminar.
Titile: "Alfven Wave Amplitude Limits in the Solar Wind"
Abstract: Shear-Alfven waves are the signature eigenmode of magnetized plasmas and
are ubiquitous and fundamental in space and astrophysical plasmas. Alfvenic
processes are thought to play a fundamental role in particle acceleration, auroral
processes, and magnetized turbulent cascades amongst many other processes.
Recent theoretical work has uncovered a stringent nonlinear limit on the
amplitude of linearly polarized shear-Alfven waves in high-beta collisionless plasmas.
This limit is associated with a self-excited firehose instability. We use 10 years
of Wind spacecraft data to demonstrate the existence of this effect, and also show a
low beta threshold that may be associated with parametric instability. Finally,
I will extrapolate these results to the inner heliosphere and discuss future
measurements with Solar Probe Plus.