Modeling of ion dynamics in the inner geospace during enhanced magnetospheric activity

Abstract

Abstract.We investigate the effect of magnetic disturbances on the ring current buildup and the dynamics of the current systems in the inner geospace by means of numerical simulations of ion orbits during enhanced magnetospheric activity. For this purpose, we developed a particle-tracing model that solves for the ion motion in a dynamic geomagnetic field and an electric field due to convection, corotation and Faraday induction and which mimics reconfigurations typical to such events. The kinematic data of the test particles is used for analyzing the dependence of the system on the initial conditions, as well as for mapping the different ion species to the magnetospheric currents. Furthermore, an estimation of Dst is given in terms of the ensemble-averaged ring and tail currents. The presented model may serve as a tool in a Sunto-Earth modeling chain of major solar eruptions, providing an estimation of the inner geospace response.

The Major Geoeffective Solar Eruptions of 2012 March 7: Comprehensive Sun-to-Earth Analysis

“…Therefore, our results are in qualitative agreement with observations by THEMISthat indicate the entry of THEMIS Einto the magnetosheath following the arrival of the pressure pulse. Tsironis et al (2015) used the outputs of various Tsyganenko models to trace test particles and determine the resulting ring-current dynamics as well as to assess the various contributions to the resulting Dst index. March 8 marks a particularly pronounced SSC with the Dst index attaining high positive values of ∼50 nT.…”

Computation of the Fields and Potentials for Particle Tracing Under the Effect of Electromagnetic Forces

“…In the context introduced above, the time-dependence of the fields and potentials is described in a logic similar to that of an "event", i.e., a well-defined set of simultaneous physics processes which are localized in time, starting and ending at specific timestamps t 1 and t 2 respectively. According to this, we have the following expressions for the magnetic field and the scalar potential [10]…”

“…A modeling option is to follow directly the full particle orbits under the electric and magnetic forces during the phases of the event. In such models, the Lorentz equation of motion is solved, either in its full form or reduced in terms of the guiding-center approximation, and the standard physics included is the magnetic field coming from the Earth's terrestrial magnet plus the fields generated by the magnetospheric currents, and the electric field owed to large-scale plasma convection and corotation with the Earth (e.g., [10,20]. An important factor, however, is the electric field induced by the time variation of the magnetic field, as it is involved in the strong acceleration of charged particles which is observed during geomagnetic disturbances [19].…”

“…An important factor, however, is the electric field induced by the time variation of the magnetic field, as it is involved in the strong acceleration of charged particles which is observed during geomagnetic disturbances [19]. In the following, we briefly present the capabilities of the current version of the particle tracing model (for more details the reader is pointed to [10]).…”

“…Regarding the modeling of the magnetic field, the Earth's magnetic field is described by a dipole magnet placed at the planet's center, tilted at an angle θ t = 11.5 • and reversed magnetic poles with respect to the geographic ones. The formula in Geocentric Solar Magnetospheric coordinates is [10]…”