Nikolai Tsyganenko (University of St Petersburg): Storm-time evolution of the magnetosphere as inferred from dynamical data mining and modern modeling methods
Abstract: Unlike computer simulations, based entirely on first-principle equations, the empirical models seek to reconstruct the real-world magnetosphere from direct in situ observations and, in that sense, can be viewed as the "ground truth" of the data. In this talk, we present and discuss first results of modeling the storm-time evolution of the magnetosphere, based on a synthesis of (i) a new method to represent the magnetic field by means of the so-called cylindrical basis functions (CBF), (ii) the dynamical "nearest-neighbour" data mining in the state parameter space, and (iii) a large pool of archived multi-mission spacecraft data for the period 1995--2019, complemented with concurrent ground disturbance indices. The modeling reveals main features of the geomagnetic field reconfiguration in terms of its depression/compression and extremely variable field line stretching. The initial contraction of the dayside magnetosphere due to the interplanetary shock arrival is accompanied with a local transient surge of the inner tail current and a dramatic antisunward discharge of the magnetic flux. As the storm progresses, the ring current buildup results in a progressively depressed magnetic field in the inner magnetosphere and the magnetic flux transfer to more distant tail plasma sheet. At the same time, a strong dawn-dusk asymmetry is developed due to the formation of the duskside partial ring current, in agreement with previous independent results.