March 17, 2017, 1:00 pm - 2:00 pm

March 17, 2017, 1:00 pm - 2:00 pm, Heliophysics Director's Seminar

Trapped in a plasma wave

Dan Gershman (NASA/GSFC Code 673)

Alfven waves are fundamental wave modes in plasmas that transport energy throughout the universe. We have used instrumentation on NASA's Magnetospheric Multiscale (MMS) as a 'wave microscope,' resolving the small-scale structure of an Alfven wave with unprecedented detail. It is only with this closeup view that we are able to directly test some of the earliest theories in plasma physics about wave dynamics. For the first time, we were able to directly observe energy being exchanged back and forth between an Alfven wave's particles and 3D electromagnetic fields. In addition, inside the wave peaks we found trapped electrons whose dynamics have been predicted to prevent plasma waves from decaying, enabling us to observe them in the first place. We can use these detailed wave properties as boundary conditions to better understand the transport of energy in the Sun-Earth system. These data illustrate the true potential of MMS as a fundamental plasma physics laboratory.

How does the magnetotail set itself up for reconnection?

Katherine Garcia-Sage (NASA/GSFC Code 673)

As a result of complex interactions between the magnetosphere, solar wind, and ionosphere, reconnection in the tail of the magnetosphere is highly variable in time and space. Even when the solar wind is steady, the magnetotail is filled with flow channels and magnetic bubbles. Using a global magnetospheric MHD model, we show how the magnetotail sets itself up for reconnection to occur, as dynamic plasma flows create patchy current sheets that result in patchy reconnection. The simulations show which velocity and magnetic field signatures may serve as indicators that reconnection is being setup nearby. These signatures can be used for MMS and other spacecraft that are searching for signs of reconnection in the magnetotail.