Reconstructing Substorms via Historical Data Mining: Is It Really Feasible?
N. A. Tsyganenko, V. A. Andreeva, M. I. Sitnov, G. K. Stephens, J. W. Gjerloev, X. Chu, O. A. Troshichev
The evolution of the low-latitude magnetosphere over the substorm cycle is reconstructed based on
a new high-resolution 3D representation of the magnetic field and nearest-neighbor data mining.
The study covers radial distances 2.5-25 RE
and employs a record-large pool of spacecraft data taken during 1995-2019. The magnetospheric state
is quantified by four indices, representing the ground geomagnetic activity and its temporal trends
in the entire range of geomagnetic latitude:
the SuperMAG SMR, the midlatitude positive bay MPB, the auroral SML, and the polar cap PC index.
The developed technique has been tested on specific substorm events, with the results presented in
the form of 5-min cadence diagrams and animations of the magnetic field line configurations and
electric current distributions. In all the analyzed events, the initial intensification and radial expansion
of the inner tail current is accompanied by a gradual stretching of the magnetic field, followed by
its sudden collapse, dramatic depletion of the current beyond R ~ 12 RE,
and a large-scale dipolarization of the field around the time of MPB peak, after which the system recovers
and tends to its pre-substorm state.
JGRA, published September 13, 2021: https://doi.org/10.1029/2021JA029604.
This work was supported by the Russian Foundation for Basic
Research (RFBR) grant 20-05-00218.