Ion heating in an auroral potential structure

¹ National Observatory of Athens, Institute for Space Applications and Remote Sensing, 15236 Penteli, Greece e-mail: daglis@space.noa.gr
² Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece e-mail: ctsironis@astro.auth.gr

Corresponding author: A. Anastasiadis, anastasi@space.noa.gr

Received: 15 October 2003
Accepted: 26 February 2004

Abstract

We investigate the interaction of O⁺ ions with a one-dimensional potential well, using Hamiltonian formulation. Heating of plasma originating in the terrestrial ionosphere plays a catalytic role in solar-driven magnetic storms, which dissipate energy globally within the magnetosphere of the earth. An interesting candidate for ionospheric plasma heating is a potential well located at auroral arcs in the high-latitude magnetosphere. We consider a potential with an exponential form, having a characteristic length L_x. The oxygen ions drift towards the auroral arc in the presence of a constant magnetic field B_z and a constant electric field E_y. The orbits of individual ions for different initial conditions – phase angle and kinetic energy – are traced. Our results show that, depending upon the initial conditions, test particles can be either accelerated or decelerated. Furthermore, we perform a parametric study for the interactions of mono-energetic and Maxwellian type of initial ion distribution – using random phase angle injection of the particles – with respect to our main model parameter, the characteristic length of the potential L_x. We conclude that for characteristic lengths comparable to twice the ion gyroradius, the O⁺ population is accelerated.