March 15th, 2019, 1:00 pm - 2:00 pm, SED Director's Seminar, Hosted by the Geospace Physics Laboratory (673)

Shock-ing surprises brought by MMS fast electron measurements

Li-Jen Chen

The MMS plasma instrument, the Fast Plasma Investigation (FPI) - designed, built, and operated at GSFC - has enabled discoveries of never-before-seen processes in space plasmas. We will highlight two such examples brought by the ultra-fast electron measurements of FPI at the terrestrial bow shock and magnetic reconnection layers, respectively. At the bow shock, while other spacecraft missions may have at most several measurements across the shock, FPI resolves the shock layer with hundreds of continuous 3D distribution functions. FPI witnesses the solar wind electron stream being accelerated in bulk to such high velocities that the streaming breaks down and is transformed into heat. In the core region of magnetic reconnection, FPI unveils both the orderly dance and scattered roaming of electrons in different regimes of the magnetic field guiding the reconnection current. These discoveries break new grounds for theories, simulations, and laboratory experiments to resolve longstanding questions on collisionless heating at shocks, and collisionless resistivity in magnetic reconnection.

How to catch the fast aurora

Robert Michell

The visual aurora displays many different types of features ranging from large-scale, slow moving structures to small-scale, extremely dynamic features. Such extreme dynamics, which have proved difficult to even image optically, present an even greater challenge when attempting to measure their in situ electron characteristics. Being able to resolve these fast features would greatly improve our estimates of the energy input into the ionosphere/thermosphere (IT) which can have significant impacts on our understanding of the response of the IT system to such inputs. We will discuss our recent instrument development efforts to achieve that goal, showing some actual auroral electron data taken with such instruments and the new science that can be enabled by going to such high time resolution measurements.

Magnetic storms heat the atmosphere and reign satellites

Eftyhia Zesta and Denny Oliveria

Magnetic storms have been known to cause upper atmosphere heating and neutral density upwelling since the beginning of space age. Enhanced density levels increase air drag forces on low-Earth orbit (LEO) satellites, which in turn affect their acceleration leading to altitude losses, lifetime reduction, and orbital tracking uncertainties. Several LEO missions in the past decades have studied the upper atmosphere heating, but in the last years the subsequent cooling of the upper atmosphere has been of great interest. We use state-of-the-art atmospheric density data from two LEO missions, CHAMP and GRACE, launched in early 2000?s, to explore the upper atmosphere heating and cooling during magnetic storms with different intensities. We found that storms with the most extreme heating are the fastest to cool off during the storm recovery phase. By using a method recently developed at NASA/GSFC (673-674), we found that the orbital drag during the most extreme storms are more than 10 times larger when compared with idealized non-storm times. We discuss the challenges current upper atmosphere density models have to overcome in order to accurately predict long-term satellite orbital drag during magnetic storms.