SM21A-2482
The Distribution of Chorus and Plasmaspheric Hiss Waves in the Inner Magnetospahere as Functions of Geomagnetic Activity and Solar Wind Parameters as Observed by The Van Allen Probes.
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Homayon Aryan, NASA Goddard Space Flight Center, Greenbelt, MD, United States, David G Sibeck, NASA/GSFC, Greenbelt, MD, United States, Oleksiy V. Agapitov, University of California Berkeley, Berkeley, CA, United States and Craig Kletzing, University of Iowa, Iowa City, IA, United States
Abstract:
The dynamics of the radiation belts is dependent upon the acceleration and loss of radiation belt electrons that is largely determined by the interaction of georesonant wave particles with chorus and plasmaspheric hiss waves. The distribution of these waves in the inner magnetosphere is commonly presented as a function of geomagnetic activity as expressed by the geomagnetic indices (Ae, Kp, and Dst). However, it has been shown that not all geomagnetic storms necessarily increase the flux of energetic electrons at the radiation belts. In fact, almost 20% of all geomagnetic storms cause a decrease in the flux of energetic electrons, while 30% has relatively no effect. Also, the geomagnetic indices are indirect, nonspecific parameters compiled from imperfectly covered ground based measurements that lack time history. This emphasises the need to present wave distributions as a function of both geomagnetic activity and solar wind parameters, such as velocity (V), density (n), and interplanetary magnetic field component (Bz), that are known to be predominantly effective in the control of radiation belt energetic electron fluxes. This study presents the distribution of chorus and plasmaspheric hiss waves in the inner magnetosphere as functions of both geomagnetic activity and solar wind parameters for different L-shell, magnetic local time, and magnetic latitude. This study uses almost three years of data measured by the EMFISIS on board the Van Allen Probes. Initial results indicate that the intensity of chorus and plasmaspheric hiss emissions are not only dependent on the geomagnetic activity but also dependent on solar wind parameters. The largest average wave intensities are observed with equatorial chorus in the region 4<L<9 primarily on the dawn-side during active conditions, fast solar wind velocity, low solar wind density, and highly negative Bz respectively.
