Energetic phenomena of substorms in the Earth's magnetosphere pose outstanding unsolved problems in the space community. Multi-point investigations of the physical processes responsible for these phenomena are especially timely due to the increasing availability of multi-point measurements from ground-based stations and distributed satellites within the magnetosphere at the present time. Understanding of these phenomena would answer fundamental questions on impulsive energy release in space and would provide valuable insights into processes occurring throughout our Universe. In addition, knowledge gained from the research would assist space weather forecasting that can affect satellite operation and electric power grids on the ground.

In this project, we use multi-point measurements to examine the sudden changes in the magnetic field just outside the Earth's radiation belt commonly known as dipolarization. We found that there are two classes of dipolarization and they have different effects on populating the radiation belt. We have also found that there is a sufficient supply of energetic electrons just outside the Earth's radiation belt to populate the radiation belt when they are brought in by the dipolarization process.

Two major physical processes are considered in the literature for the underlying cause of particle energization in space. They are called magnetic reconnection and current disruption. We have elaborated the similarities and differences between these two fundamental processes to facilitate their identification in the investigation of energetic phenomena in space.

Turbulence in space associated with a substorm is an outstanding unsolved problem in space research. We use modern analysis techniques such as self-similarity analysis and structure function analysis to demonstrate the presence of super-diffusion process in substorm-associated space turbulence. This study has discovered the region in space that is a natural laboratory to study the unusual phenomenon of super-diffusion.

An interesting phenomenon recently identified in association with a substorm is the occurrence of spatially periodic intensification of brightness in aurora just before the onset of a substorm. This provides an important clue to the onset process of substorms. We have found an instability that can reproduce the characteristics (both the growth rate and the wavelength) of these spatially periodic structure, providing a very strong evidence that the proposed plasma instability is the long-sought-after physical process for the onset of substorms.

We have investigated both theoretically and observationally the efficiency in causing the rapid magnetic field changes in dipolarization by a source just outside the radiation belt or from a distant source much further away from the Earth. Both approaches show that the distant source is insufficient to account for the total magnetic flux involved in dipolarization. This result helps researchers to focus their effort in the region just outside the radiation belt for the dynamic changes in dipolarization.

The results from the above work have been published in eleven research articles in refereed journals. The knowledge gained has also been applied to research in other planets.

Throughout the project, we have engaged summer student and junior scientists in these research activities. Their involvement provides a valuable asset for them in their future job endeavors.

Last Modified: 07/18/2018
Modified by: Anthony T. Y Lui