Source: Journal of Geophysical Research: Space Physics
Particles are trapped in the magnetic field of the Earth, forming the magnetosphere. To study the orbits of energetic ions in prescribed dipole and stretched magnetic fields relevant to the Earth’s magnetosphere, highly accurate test-particle simulations were developed.
Borovsky et al.  conclude that the simulations show the loss cone of ring-current ions is substantially modified during disturbed times. The results pertain to electrons also. As the gyroradius of the ions relative to the curvature of the local magnetic field (i.e. the parameter of adiabaticity) increases, the classic zeroth-order expansion of the first adiabatic invariant, the magnetic moment, is no longer conserved well. This has important implications for the radiation-belt and ring current modeling methodologies currently in use.
The loss-cone modifications are fundamental and their implementation in magnetospheric models is critical to correctly describe particle transport and particle loss mechanisms of the inner magnetosphere.
Citation: Borovsky, J. E., Yakymenko, K. N., & Delzanno, G. L. (2022). Modification of the Loss Cone for Energetic Particles in the Earth’s Inner Magnetosphere. Journal of Geophysical Research: Space Physics, 127, e2021JA030106. https://doi.org/10.1029/2021JA030106
—Viviane Pierrard, Editor, Journal of Geophysical Research: Space Physics