Speaker
Dr
Drew Turner
(University of California, Los Angeles)
Description
In Earth's outer radiation belt, flux "dropout" events involve the sudden decrease of electron fluxes by up to several orders of magnitude in only a few hours, and the dominant mechanism responsible for dropouts is still debated. On 30 September 2012, a major dropout occurred throughout the entire outer radiation belt during the main phase of a strong geomagnetic storm. Here, we investigate the observations from an unprecedented number of vantage points throughout the system using 14 different spacecraft from the NOAA-POES and -GOES constellations and NASA's THEMIS and new, Van Allen Probes (RBSP) missions. This array of observatories allowed us to quantify the full ranges, in energy, equatorial pitch angle, and L* (radial distance), and timescales of electrons effected by this dropout. Furthermore, with THEMIS and RBSP, we calculated relativistic electrons' phase space densities as a function of their three adiabatic invariants (Mu, K, and L*), which remove ambiguity inherent in flux observations due to adiabatic variations during storms. The evolution of the phase space density profiles revealed the true extent of the loss during the dropout, how competing, localized sources became active during the main phase, and how transport likely played a key role in propagating the dropout throughout most of the outer belt. Both THEMIS and RBSP observed key signatures consistent with loss due to magnetopause shadowing and subsequent outward radial transport, including the loss of energetic (i.e., 100's of keV) ring current ions in a similar manner to the relativistic electrons. However, RBSP also revealed that losses to the atmosphere must also play a role, particularly at lower L-shells (L*<~4), which was supported in part by the POES observations. Here, we provide an overview of these results and discuss their implications for our understanding of outer belt dropout events.
Primary author
Dr
Drew Turner
(University of California, Los Angeles)
Co-authors
Dr
Bernard Blake
(The Aerospace Corp.)
Dr
Chia-Lin Huang
(University of New Hampshire)
Prof.
Daniel Baker
(LASP - University of Colorado)
Dr
Geoff Reeves
(Los Alamos National Laboratory)
Prof.
Harlan Spence
(University of New Hampshire)
Dr
Juan Rodriguez
(CIRES - University of Colorado)
Dr
Michael Henderson
(Los Alamos National Laboratory)
Dr
Seth Claudepierre
(The Aerospace Corp.)
Dr
Steve Morley
(Los Alamos National Laboratory)
Prof.
Vassilis Angelopoulos
(University of California, Los Angeles)
