AUTHOR=Stephens Grant K. , Sitnov Mikhail I. 

TITLE=Concurrent Empirical Magnetic Reconstruction of Storm and Substorm Spatial Scales Using Data Mining and Virtual Spacecraft

JOURNAL=Frontiers in Physics

VOLUME=Volume 9 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/physics/articles/10.3389/fphy.2021.653111

DOI=10.3389/fphy.2021.653111

ISSN=2296-424X

ABSTRACT=Data-mining (DM) has ushered in a new era of empirical magnetic reconstructions of the
4 magnetosphere via application of the k-nearest neighbors (kNN) method. In this approach,
5 the combined magnetosphere storm-substorm state is characterized by the Sym-H and AL IMF
6 indices, their time derivatives, and the solar wind electric field vBz . However, using the
7 DM reconstructions to account for the substorm contributions to the ring current as well as
8 describing storm-time substorms remains a problem. The inner region r ≤ 12RE , where the
9 ring current develops, has a much higher density of data than the tail region 12RE ≤ r ≤ 22RE,
10 where substorms operate. This results in two models inconsistent in their scales dictated by the
11 corresponding data densities. The inner model reconstructs storm time dynamics, including the
12 formation of the westward and eastward ring current and pressure distributions. The outer model
13 captures substorm features, including the thinning and rapid dipolarization of the tail sheet during
14 the growth and expansion phases respectively. However, the substorm model is insufficient to
15 reconstruct the eastward ring current while the storm model cannot fully reproduce substorm
16 effects because it overfits in the tail region. This issue is addressed by constructing a hybrid
17 model which is fit using virtual magnetic field observations generated by sampling the other
18 two models. The resulting merged resolution model concurrently captures the spatial scales
19 associated with both storms in the inner region and substorms in the near-tail region. Hence it
20 is particularly useful for investigation of the storm-substorm relationship, including storm-time
21 substorms and the impact of individual substorm injections to the buildup of the storm-time ring
22 current.