title: Highly relativistic radiation belt electron acceleration, transport, and loss: Large solar storm events of March and June 2015.
abstract: Two of the largest geomagnetic storms of the last decade were witnessed in 2015. On 17 March 2015, a coronal mass ejection-driven event occurred with aDst(storm time ring current index) value reaching -223 nT. On 22 June 2015 another strong storm (Dstreaching -204 nT) was recorded. These two storms each produced almost total loss of radiation belt high-energy (E≳ 1 MeV) electron fluxes. Following the dropouts of radiation belt fluxes there were complex and rather remarkable recoveries of the electrons extending up to nearly 10 MeV in kinetic energy. The energized outer zone electrons showed a rich variety of pitch angle features including strong "butterfly" distributions with deep minima in flux atα= 90°. However, despite strong driving of outer zone earthward radial diffusion in these storms, the previously reported "impenetrable barrier" atL≈ 2.8 was pushed inward, but not significantly breached, and noE≳ 2.0 MeV electrons were seen to pass through the radiation belt slot region to reach the inner Van Allen zone. Overall, these intense storms show a wealth of novel features of acceleration, transport, and loss that are demonstrated in the present detailed analysis.
authors.affiliation: Laboratory for Atmospheric and Space Physics University of Colorado Boulder Colorado USA.
authors.forename: D N
authors.initials: DN
authors.lastname: Baker
authors.affiliation: Laboratory for Atmospheric and Space Physics University of Colorado Boulder Colorado USA.
authors.forename: A N
authors.initials: AN
authors.lastname: Jaynes
authors.affiliation: Goddard Space Flight Center NASA Greenbelt Maryland USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Kanekal
authors.affiliation: MIT Haystack Observatory Westford Massachusetts USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Foster
authors.affiliation: MIT Haystack Observatory Westford Massachusetts USA.
authors.forename: P J
authors.initials: PJ
authors.lastname: Erickson
authors.affiliation: The Aerospace Corporation Los Angeles California USA.
authors.forename: J F
authors.initials: JF
authors.lastname: Fennell
authors.affiliation: The Aerospace Corporation Los Angeles California USA.
authors.forename: J B
authors.initials: JB
authors.lastname: Blake
authors.affiliation: Laboratory for Atmospheric and Space Physics University of Colorado Boulder Colorado USA.
authors.forename: H
authors.initials: H
authors.lastname: Zhao
authors.affiliation: Laboratory for Atmospheric and Space Physics University of Colorado Boulder Colorado USA.
authors.forename: X
authors.initials: X
authors.lastname: Li
authors.affiliation: Laboratory for Atmospheric and Space Physics University of Colorado Boulder Colorado USA.
authors.forename: S R
authors.initials: SR
authors.lastname: Elkington
authors.affiliation: Los Alamos National Laboratory Los Alamos New Mexico USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Henderson
authors.affiliation: Los Alamos National Laboratory Los Alamos New Mexico USA.
authors.forename: G D
authors.identifier: 0000-0002-7985-8098
authors.initials: GD
authors.lastname: Reeves
authors.affiliation: Institute for the Study of Earth, Oceans, and Space University of New Hampshire Durham New Hampshire USA.
authors.forename: H E
authors.initials: HE
authors.lastname: Spence
authors.affiliation: Department of Physics and Astronomy University of Iowa Iowa City Iowa USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Kletzing
authors.affiliation: Department of Physics and Astronomy University of Minnesota, Twin Cities Minneapolis Minnesota USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Wygant
keywords: electron acceleration; magnetosphere; radiation belts