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3:30 p.m.
via ZOOM
For More Information:
Taylor Prendergast
301 405 4951
tprender@umd.edu
https://terpconnect.umd.edu/~swisdak/PPS/plasma_seminar.html
The next plasma physics seminar will begin at 3:30 pm on Wednesday, April
14th. It will be held on Zoom at this link:
https://umd.zoom.us/j/8380649660. Katherine Goodrich of UC-Berkeley will
be discussing "*Shocks Under the Microscope: Examining the Microphysics of
Collisionless Shocks with High Resolution, Multi-point Space Plasma
Measurements".*
The abstract:
Collisionless shocks are an important and universal phenomenon in
astrophysical plasmas. Shocks form when a supersonic plasma flow interacts
with an impermeable obstacle. Examples of such interactions include
galactic jets or supernova remnants interacting with the interstellar
medium, or plasma wind from stars encountering stellar system bodies, such
as planets, comets and moons. The shock performs the necessary function of
converting kinetic energy to thermal energy, heating the originally
supersonic plasma flow until its speed is reduced and it can flow around
the obstacle. The energy conversion processes that take place inside
collisionless shocks, however, are not well established and have thus been
a subject of interest for several decades.
The closest and perhaps the most relevant collisionless shock to us humans,
is the Earth's bow shock. This shock forms 10-12 Earth radii upstream of
our planet when supersonic plasma ejected from the sun, called the solar
wind, meets the Earth's intrinsic magnetosphere. The bow shock has been
observed by multiple spacecraft such as ISEE, Cluster, WIND, and THEMIS
over three decades. These missions have provided us with a wealth of
information on plasma conditions both upstream and downstream of the shock,
however, limited instrument capabilities have prevented us from resolving
the physical processes active at the shock itself. The energy conversion
processes active within shocks are expected to occur at primarily electron
spatial and time scales (milliseconds to seconds), which up until recently
were beyond the reach of our particle observations. While we can rely on
highly time resolved magnetic and electric field measurements from these
missions, they provide an incomplete view of the inner workings of the
shock.
Observations from the Magnetospheric Multiscale (MMS) mission (launched in
2014) provide particle observations on the order of 10s of milliseconds,
providing an unprecedented opportunity to directly observe microscale
processes inside collisionless shocks. In this talk, we'll take a first
look at the direct connection between electric and magnetic field signals
with electron and ion dynamics in the Earth's bow shock. We find that
energy conversion can occur from multiple processes, some unexpected,
within varied areas of the shock. The new dataset provided by MMS enables a
new age of collisionless shock analysis as well as motivation for future
space missions dedicated to the shock, signaling an exciting time for space
physicists!
The full schedule for this semester can be found at
https://terpconnect.umd.edu/~swisdak/PPS/plasma_seminar.html
This Event is For: Campus
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