The research group led by Weichao Tu, an assistant professor in the Department of Physics and Astronomy, conducts a new analysis of three space storms that reveals the mechanism of particle loss from the Van Allen radiation belts.
The work has been published in the Journal of Geophysical Research:
The Van Allen belts are giant, donut-shaped rings of radiation that encircle Earth, extending up to 58,000 kilometers into space. Electrons in the belts, known as “killer electrons”, carry energies that are about a thousand times more than a person receives in a dental X-ray. This radiation can be remediated as electrons get knocked between belts, down into the atmosphere, or out into space.
The new study by the WVU group examines how forces such as solar wind and magnetic storms drive this electron loss by analyzing three separate “dropout events” in which there was a sudden loss of electrons in the outermost belt. Understanding why such events happen is important because radiation within the belts can interfere with communications systems and damage satellites.
The study reveals that two distinct mechanisms played a role in freeing the trapped electrons. In some storms, the most important mechanism was magnetopause shadowing, in which a gust of solar wind temporarily changes the shape of the magnetosphere. This interferes with the particles’ typical drift around the planet and forces electrons outward, toward space. In other storms, waves of energy generated by plasma within the magnetosphere scattered electrons, forcing them downward, into the atmosphere.
In the future, the team hopes to determine what percentage of dropout events is caused by magnetopause shadowing versus plasma-generated waves, information that could help scientists predict when it is safe to launch satellites and other space missions.
The published work was first authored by Zheng Xiang, a visiting graduate student at WVU from Wuhan University of China, and in collaboration with Prof. Binbin Ni at Wuhan University, Profs. Xinlin Li and Dan Baker at the Laboratory for Atmospheric and Space Physics of University of Colorado Boulder, and Dr. Steve Morley at the Los Alamos National Laboratory. The project was funded by research grants from National Science Foundation and National Aeronautics and Space Administration.
Reference: “Understanding the Mechanisms of Radiation Belt Dropouts
Observed by Van Allen Probes”, Journal of Geophysical Research: Space Physics, 122, doi:10.1002/2017JA024487 (2017). Authors: Zheng Xiang, Weichao Tu, Xinlin Li, Binbin Ni, S. K. Morley, and D. N. Baker.
Contact:
Weichao Tu,
304.293.3349, Assistant Professor at the Department of Physics and Astronomy