Date of Award
2026
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Space Science
Committee Chair
Lingling Zhao
Committee Member
Gary Zank
Committee Member
Jakobus le Roux
Committee Member
Qiang Hu
Committee Member
Laxman Adhikari
Research Advisor
Lingling Zhao
Subject(s)
Solar wind, Solar energetic particles, Heliosphere (Astrophysics)
Abstract
Energetic-particle transport in the near-Sun solar wind is strongly controlled by magnetic turbulence and its geometry. Using Parker Solar Probe observations from encounters E1--E19, we investigate parallel, perpendicular, and momentum diffusion coefficients for energetic protons in the inner heliosphere. The observed turbulence spectra are decomposed into slab and two-dimensional components using a composite turbulence model. The parallel diffusion coefficient is calculated using second-order quasi-linear theory, while the perpendicular diffusion coefficient is obtained from unified nonlinear transport theory. The results show that parallel diffusion increases with heliocentric distance but decreases with increasing turbulence amplitude, indicating enhanced pitch-angle scattering in stronger turbulence. Perpendicular diffusion remains much smaller than parallel diffusion, although it increases in regions of larger \(\delta B/B_0\). The momentum diffusion coefficient decreases radially but increases with turbulence amplitude, suggesting stronger stochastic acceleration in more turbulent near-Sun regions.
Recommended Citation
Madam Subashchandar, Nibuna Siranjeevi, "The parallel and perpendicular diffusion of energetic particles in the inner heliosphere using nonlinear theories and observations" (2026). Dissertations. 503.
https://louis.uah.edu/uah-dissertations/503