GEM: Solar Wind Triggering, Periodicity, and Evolution of Sawtooth Events During Magnetic Storms

Boston College, Chestnut Hill MA

Investigators

Abstract

Sawtooth events in the Earth?s magnetosphere are global, large-amplitude oscillations of energetic plasma particle fluxes at geosynchronous orbit. Sawtooth events are one of the primary magnetospheric modes during extreme solar wind driving periods cause large disturbances in the magnetosphere and ionosphere. It is thought that sawtooth events are periodic intense magnetospheric substorms. There are still a number of questions concerning sawtooth events that remain to be answered: (1) Under what magnetospheric condition can a solar wind change trigger substorm onset? (2) How does the magnetospheric convection near sawtooth onset vary with the solar wind? (3) What are the loading and unloading rates of the magnetotail magnetic flux during sawtooth oscillations? (4)? Can the effective scale length of the dayside magnetopause reconnection line be derived? (5) What determines the period of sawtooth oscillations? (6) Can the evolution of the magnetotail magnetic flux be calculated simply from the solar wind input? This project will use statistical analyses, as well as case studies, to examine these questions. The project will use a new method to determine the effective scale length of the dayside magnetopause reconnection line during sawtooth events and to determine how this scale length varies with the solar wind. The solar wind parameters will be used as input to calculate the evolution of the magnetotail/polar cap magnetic flux during sawtooth events. The new methods for determining the scale length of the reconnection line, and the evolution of magnetic flux in the magnetotail will provide guidance for similar studies of isolated substorms. The empirical formulas of the magnetospheric parameters have the potential to be useful in forecasting and nowcasting of space weather events.