Open Access

Ground magnetic perturbations associated with the standing toroidal mode oscillations in the magnetosphere-ionosphere system

  • Hiroyuki Nakata1Email author,
  • Shigeru Fujita1, 2,
  • Akimasa Yoshikawa3,
  • Masahiro Itonaga4 and
  • Kiyohumi Yumoto3
Earth, Planets and Space201452:BF03351669

DOI: 10.1186/BF03351669

Received: 15 October 1999

Accepted: 17 August 2000

Published: 20 June 2014

Abstract

The behavior of toroidal mode oscillations of standing Alfvén waves (refer to as standing Alfvén oscillations) in the coupled magnetosphere-ionosphere system is investigated using a trapezoid-shape magnetosphere model. It is found that the magnetic perturbation is transmitted across the ionosphere differently in the two cases where the ionospheric electric field perturbation is static (Pedersen conductivity > Hall conductivity) and where it is inductive (Pedersen conductivity < Hall conductivity). It is noted that the ionospheric Hall current for the inductive condition shields the magnetic field perturbation. The north-south asymmetry of the conjugate ground magnetic perturbations is calculated by using a trapezoid model with the ionospheric and magnetospheric parameters based on the IGRF and IRI. It is revealed that the ionospheric electric field is almost static for the fundamental mode oscillation, whereas inductive for the higher harmonic ones. It is also found that the north-south asymmetry of the ground magnetic perturbations depends not only on the L-value but also on magnetic longitude; this is because the ionosphere and magnetic field conditions are not uniform as a function of longitude.