Abstract
Abstract. Størmer's particles' trapping regions for a planet with an intrinsic dipolar magnetic field are considered, taking into account the ring current which arises due to the trapped particles' drift for the case of the Earth. The influence of the ring current on the particle trapping regions' topology is investigated. It is shown that a critical strength of the ring current exists under which further expansion of the trapping region is no longer possible. Before reaching this limit, the dipole field, although deformed, retains two separated Størmer regions. After transition of critical magnitude, the trapping region opens up, and charged particles, which form the ring current, get the opportunity to leave it, thus decreasing the ring current strength. Numerical calculations have been performed for protons with typical energies of the Earth's radiation belt and ring current. For the Earth's case, the Dst index for the critical ring current strength is calculated.
Highlights
One of the first scientists who studied the problem of finding trajectories of charged particles moving from the Sun to the Earth was Norwegian physicist Carl Størmer
The present paper consists of the following sections: Sect. 2 describes the Earth’s ring current and its general features; in Sect. 3 we consider the mathematical formulation of the Størmer problem; in Sect. 4 we consider the effect of Størmer’s parameter γ change on the allowed–forbidden regions’ configuration; in Sect. 5 the trapping regions are modeled with different magnitudes of the ring current strength
We propose a new loss mechanism associated with the disappearance of Størmer’s forbidden region of particle motion between two allowed regions due to an increase in the ring current strength
Summary
In the Størmer problem in connection with its specificity (axial symmetry), we will consider only the contributions of the dipole field (the contributions of the quadrupole and other multipoles have been considered in Shebalin, 2004, but only axially symmetric components, which are small for the Earth’s case), the bz component of the external origin field (IMF or tail current sheet field) and field of an axially symmetric ring current This approximation will allow us to estimate the influence of the ring current on the allowed regions of particle motion for the case of the Earth’s magnetosphere. The present paper consists of the following sections: Sect. 2 describes the Earth’s ring current and its general features; in Sect. 3 we consider the mathematical formulation of the Størmer problem; in Sect. 4 we consider the effect of Størmer’s parameter γ change on the allowed–forbidden regions’ configuration; in Sect. 5 the trapping regions are modeled with different magnitudes of the ring current strength
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