Characterizing Energetic Electron Precipitation and Whistler-mode Waves during Electron Injection Events
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2022-01
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Abstract
Magnetically trapped particles in the magnetosphere can be lost and precipitate into the atmosphere. Precipitated particles deposit energy into the atmosphere and affect the atmospheric chemistry and ionization in the ionosphere. The change in the ionospheric charge density can disturb telecommunication on the Earth. The precipitated particles can also alter the density of substantial atmospheric components such as HOx and NOx which are critical catalysts in ozone destruction. Therefore, studying the causes and effects of energetic particle precipitation has great importance. One type of geomagnetic event that is associated with energetic particle precipitation is a substorm injection. Energetic electron precipitation associated with substorm injections typically occurs when magnetospheric waves, particularly whistler-mode waves, resonantly interact with electrons to affect their pitch angle and scatter particles into the loss cone through a diffusion process. In this thesis, I describe two studies about electron precipitation through wave-particle interactions during substorm injection events. The first study aims to quantitatively characterize energetic electron precipitations during injection events in the magnetosphere. This part uses in-situ measurements by the Van Allen Probes and presents the typical substorm-induced precipitation flux as 4×〖10〗^6 el/cm2.s.sr. The precipitation flux is estimated from characterizing the ground signatures of precipitated electrons on radio signal propagation in the ionosphere. The second study aims to investigate the physical drivers of electron precipitation during injections. This part investigates whistler-mode wave generation in conjunction with electron injections using in-situ wave measurements by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission. This study indicates that only 5% of the injection events are associated with an order of magnitude wave power enhancement. Investigating diffusion rates due to the generated waves during the selected events states that strong scattering is not typically associated with injection events in the magnetosphere.
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Ghaffari, R. (2022). Characterizing energetic electron precipitation and whistler-mode waves during electron injection events (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.