Complementary and Catalytic Roles of Man‐Made VLF Waves and Natural Plasma Waves in the Loss of Radiation Belt Electrons. Issue 10 (11th October 2021)

• Record Type: Journal Article
• Authors: Li, L. Y.; Wang, Z. Y.; Yu, J.; Cao, J. B.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-10-11
• Subjects: man‐made VLF waves -- lightning‐generated whistlers -- plasmaspheric hiss -- inner radiation belt -- slot region -- loss of radiation belt electrons; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2020JA028879
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: By simulating the energy and pitch angle diffusions of radiation belt electrons caused by ground‐based VLF transmitter waves, plasmaspheric hiss and lightning‐generated whistlers (LGWs), we quantitatively estimated the electron change rates caused by individual and multiple waves. We found that man‐made VLF waves and naturally generated hiss or LGWs play complementary and catalytic roles in the loss of radiation belt electrons. Man‐made VLF waves mainly reduce the hundreds of keV electrons in inner radiation belt ( L < 2), but they alone cannot effectively remove the MeV electrons in slot region ( L ∼ 2–3) because of unefficient diffusions at small pitch angles (<60°). On the contrary, natural hiss and LGWs do not affect the hundreds of keV electrons in the inner belt, but they are able to effectively reduce the hundreds of keV and MeV electrons at small pitch angles in the slot region. The loss of the small pitch electrons caused by hiss or LGWs offer a necessary phase space density gradient for the diffusion of large pitch angle MeV electrons (>60°) driven by man‐made VLF waves toward the loss cone. The combined diffusions by three types of the waves ultimately catalyze the loss of the large pitch angle MeV electrons in the slot region, and thus cause more electron losses in the wider energy and pitch angle ranges. Plain Language Summary: Although man‐made VLF waves, lightning‐generated whistlers (LGWs) and plasmaspheric hiss are often used to estimate the lifetime of radiation belt electrons, their roles are not differentiated well. An ongoing debate has been whether man‐made VLF waves are able to effectively remove MeV electrons in slot region. Here, by simulating the electron energy and pitch angle diffusions driven by individual and multiple waves, we found that man‐made VLF waves mainly reduce the hundreds of keV electrons in inner radiation belt ( L < 2), while naturally generated hiss and LGWs are able to effectively remove the hundreds of keV and MeV electrons at small pitch angles (<60°) in slot region. The loss of the small pitch electrons caused by hiss or LGWs offer a necessary phase space density gradient for the diffusion of large pitch angle MeV electrons (>60°) driven by man‐made VLF waves toward the loss cone. Man‐made VLF waves ultimately promote the loss of MeV electrons at large pitch angles in slot region when existence of natural hiss waves or LGWs. These conclusions are helpful for understanding to the roles of each type of the waves in changing the high‐energy radiation belt electrons. Key Points: Man‐made VLF waves mainly reduce the hundreds of keV electrons in inner radiation belt, but they alone cannot effectively remove the MeV electrons in slot region Plasmaspheric hiss and lightning‐generated whistlers (LGWs) mainly remove the MeV electrons in slot region, but they do not reduce the hundreds of keV electrons in inner belt Man‐made VLF waves can promote the loss of the large pitch angle MeV electrons in slot region when existence of naturally generated hiss or LGWs