Statistical Study of Solar Wind Conditions Prior to Substorm Onsets

Due to complex, multi-region, coupled plasma systems, auroral substorm onsets have been historically difficult to predict. The northward turning of the interplanetary magnetic field was considered the primary candidate as an external triggering mechanism for substorm onsets. However, that was later shown to be coincidental in nature. This study is motivated by recent multi-spacecraft observations that show how several magnetosheath jets at the bow shock were heavily correlated to substorm onsets, indicated by a strongly radial IMF interval. In the past, studies have looked at small samples of substorms in order to make large-scale predictions. However in this study, a total of 28 years of solar wind data is analyzed from NASA’s OMNI database to determine if any predictions can be made at all. This thesis investigates statistical differences between parameters before, during, and after substorm onset. This is accomplished using Welch’s t-test to account for differences in distribution means and variances. A time period requirement in-between substorms will also be utilized to show that each parameters’ results are not affected by reoccurring substorms. It is found that Bz, Ey, and |E| are the most significant parameters based off this test.