Earth's ring current
Earth's ring current is responsible for shielding the lower latitudes of the Earth from magnetospheric electric fields. It therefore has a large effect on the electrodynamics of geomagnetic storms. The ring current system consists of a band, at a distance of 3 to 8 RE, which lies in the equatorial plane and circulates clockwise around the Earth (when viewed from the north). The particles of this region produce a magnetic field in opposition to the Earth's magnetic field and so an Earthly observer would observe a decrease in the magnetic field in this area.:135 The negative deflection of the Earth's magnetic field due to the ring current is measured by the Dst index.
The ring current energy is mainly carried around by the ions, most of which are protons. However, one also sees alpha particles in the ring current, a type of ion that is plentiful in the solar wind. In addition, a certain percentage are O+ oxygen ions, similar to those in the ionosphere of Earth, though much more energetic. This mixture of ions suggests that ring current particles probably come from more than one source.
The ring current and geomagnetic storms
- I. A. Daglis; R. M. Thorne; W. Baumjohann & S. Orsini (November 1999). "The terrestrial ring current: Origin, formation, and decay". Reviews of Geophysics. 37. pp. 407–438. Bibcode:1999RvGeo..37..407D. doi:10.1029/1999RG900009.
- Ronald T. Merrill (15 November 2010). Our Magnetic Earth: The Science of Geomagnetism. University of Chicago Press. ISBN 978-0-226-52050-6.