Pitch Angle Distributions of Electrons in Space Environment - Radial Dependance during Dipolarization at Tailside
Description: The radiation environment in the Earth's space, including charged particles, is important to be investigated, not only because the space weather can affect it but also the contemporary design for satellites would rely on precise information of it. Our previous study on dipolarization effects on pitch-angle distributions (PAD) of electrons at the tailside in the inner plasmasheet during geomagnetic activity has significantly contributed to the new finding that the cigar distributions below about 1keV tend to be isotropized yet the isotropic distributions above 1keV tend to be cigarized. The ineffectiveness of Fermi acceleration below 1keV, because the bounce period would be comparable to the dipolarization time, has been proposed to be the factor causing the cigarization not effective. In this study, we would extend our analysis to the RADIAL distributions of the proportion of isotropization to cigarization for electrons up to a few tens of keV, during the dipolarization. This is because that at different L-shell for different radial distance, the field line length is different so the electron bounce time is different, affecting the validity of Fermi acceleration so as to affect the extent of cigarization. There were previous studies indicated that near the Earth where the field line is similar to a dipole, the betatron acceleration would dominate while the Fermi acceleration would dominate at the distance far from the Earth where the field line is stretched. This physical concept could be also examined from this observational analysis, in addition to previous checking on the dependence of this variations on energies. This would not only contribute to modeling electrons environment during dipolarization when geomagnetic activities occur, but is also beneficial to the design of satellite based on the information of variations of angular distributions of fluxes provided.
Amount: TWD 726,000
Funding type: research
Funder scheme: 學術補助
Investigator: 汪愷悌 (lead)
Institution: 國立成功大學太空與電漿科學研究所
Subfield: Space and Planetary Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Funded outputs count: 1
Funder award ID: MOST104-2111-M032-001-MY2
OpenAlex ID: G1251237012