The effects of inductive electric field on the dynamics of terrestrial inner magnetosphere

Liu, Jianghuai

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https://hdl.handle.net/2142/127205 Copy

Description

Title

The effects of inductive electric field on the dynamics of terrestrial inner magnetosphere

Author(s)

Liu, Jianghuai

Issue Date

2024-12-06

Director of Research (if dissertation) or Advisor (if thesis)

Ilie, Raluca

Doctoral Committee Chair(s)

Ilie, Raluca

Committee Member(s)

• Makela, Jonathan J
• Kudeki, Erhan
• Peng, Zhen

Department of Study

Electrical & Computer Eng

Discipline

Electrical & Computer Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Space Plasma Physics
• Magnetosphere Physics
• Terrestrial Ring Current
• Plasmasphere
• Space Plasma Acceleration

Abstract

Geomagnetic storms are the result of energetic charged particles of both solar and ionospheric origin being transported and injected into the terrestrial inner magnetosphere, producing significant plasma and electromagnetic perturbations of the geospace environment, which can have deleterious effects on both technological and economic assets in space and on the ground. Composed of relativistic electrons and protons, the radiation belt is a hazardous environment for both spacecraft and humans in space, while variations in the ring current, an electric current system flowing around Earth consisting of energetic ions and electrons, can cause severe disruption of electrical systems on the ground. As a predominant mechanism by which plasma is energized throughout the terrestrial magnetospheric cavity, the ambient electric fields control the magnetospheric convection while also regulating the total plasma energy content in near-Earth space. Even though a clear relationship has been established between the enhancement of magnetospheric large-scale electric field and inner magnetospheric ring current by extensive in-situ spacecraft and ground-based measurements, knowledge of the particular energization processes that take place in the inner magnetospheric region is limited at best. The difficulty lies in the fact that observations alone cannot provide a clear separation of the different sources of energization. Using a newly developed physics-based first principle model, this dissertation explicitly quantifies the effects of the inductive electric field, resulting from the temporal change of magnetic field, on the dynamics of the terrestrial inner magnetosphere, especially on the buildup of storm-time ring currents. Kinetic models are of crucial importance in the study of inner magnetosphere dynamics. This dissertation presents the theoretical and numerical developments implemented in the Hot Electron-Ion Drift Integrator (HEIDI) model to incorporate the effect of the inductive electric field, which makes it the first numerical model that explicitly considers these effects. Specifically, new drift terms associated with the inductive electric field are incorporated into the calculation of bounce-averaged coefficients of the equatorial phase space distribution function, and the effects of the inductive drifts on the total drift and energization rate are tested under certain inductive electric field models for the first time. To validate the new model, two empirical inductive electric field models and one self-consistent inductive electric field with an analytically changing magnetic field are established and examined. This work shows that the rapidly changing magnetic field produces large inductive electric fields that can frequently dominate over the electrostatic component of the electric field. Consequently, not taking the effect of the inductive electric field (even if changes of magnetic gradient-curvature drift have been considered) into account leads to a mis-estimation of the kinematics of the ring current ion species and the associated ring current evolution over time. In order to incorporate a realistic description of electromagnetic fields and enhance self-consistent coupling between fields and plasma, this thesis presents the new self-consistent coupling implemented between the HEIDI model and the global magnetospheric MHD model. The magnetic field is obtained by solving the force-balanced MHD equations, then passed from the MHD model to the kinetic model, forming an appropriate geospace simulation setup that can be used to explore the change in the inner magnetospheric dynamics due to the presence of inductive electric fields. Using synthetic solar wind conditions to drive the dynamics in the global magnetosphere, the work presented in this thesis demonstrated that the inner magnetospheric inductive electric field is persistent even during steady solar wind conditions, providing long-lasting drift and convection that have the potential to significantly alter the trajectory of both thermal and energetic plasma. Furthermore, we have shown that the local inductive-driven convection can dominate over the potential-driven convection at all times. Such changes in plasma drift due to the inductive electric field further reshape the storm-time ring current morphology by increasing its degree of asymmetry. Furthermore, the inductive electric field is effective in energizing the trapped ring current ions and increasing the plasma pressure in the region without increasing the number of particles into the domain. These results emphasize the importance of complete electric field description in modeling the inner magnetospheric plasma dynamic. Although particles of all energies experience the same change in the azimuthal drift due to inductive effects, the azimuthal drift path of low-energy plasma is more effectively changed by the inductive effects, which can lead to additional changes in the plasmasphere evolution during both storm-time and recovery phase. In addition to the transport and energization of ring current ions, the cold H⁺ produced via charge exchange reactions between ring current ions and exospheric neutral hydrogen is explored. This process provides an additional source of cold plasma that further contributes to the plasmasphere and affects the plasma dynamics in the Earth's magnetosphere system, which is required to explain the large discrepancy between current observations and numerical modeling solutions for plasmaspheric refilling rates. Numerical simulations were performed with the HEIDI model mimicking an idealized three-phase geomagnetic storm to investigate the role of heavy ion composition in the ring current (O⁺ vs. N⁺) and exospheric neutral hydrogen density in the production of cold H⁺ via charge exchange reactions. It is found that ring current heavy ions produce more than 50% of the total cold protons via charge exchange reactions, and energetic N⁺ is more efficient in producing cold H⁺ via charge exchange reactions than O⁺. Furthermore, the density structure of the cold protons is highly dependent on the mass of the parent ion; that is, cold H⁺ deriving from charge exchange reactions involving energetic O⁺ with neutral hydrogen, populates the lower L-shells, while cold H⁺ deriving from charge exchange reactions involving energetic N⁺ with neutral hydrogen populates the higher L-shells.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127205

Copyright and License Information

© 2024 Jianghuai Liu

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