Ring Current Dynamics

Abstract

This chapter reviews the current understanding of ring current dynamics. The terrestrial ring current is an electric current flowing toroidally around the Earth, centered at the equatorial plane and at altitudes of ∼10,000 to 60,000 km. Enhancements in this current are responsible for global decreases in the Earth's surface magnetic field, which have been used to define geomagnetic storms. Intense geospace magnetic storms have severe effects on technological systems, such as disturbances or even permanent damage of telecommunication and navigation satellites, telecommunication cables, and power grids. The main carriers of the ring current are positive ions, with energies from ∼1 keV to a few hundred keV, which are trapped by the geomagnetic field and undergo an azimuthal drift. The ring current is formed by the injection of ions originating in the solar wind and the terrestrial ionosphere into the inner magnetosphere. The injection process involves electric fields, associated with enhanced magnetospheric convection and/or magnetospheric substorms. The quiescent ring current is carried mainly by protons of predominantly solar wind origin, while active processes in geospace tend to increase the abundance (both absolute and relative) of O + ions, which are of ionospheric origin. During intense geospace magnetic storms, the O + abundance increases dramatically. This increase has been observed to occur concurrently with the rapid intensification of the ring current in the storm main phase and to result in O + dominance around storm maximum. This compositional change can affect several dynamic processes, such as species-and energy-dependent charge-exchange and wave-particle scattering loss.

Correlation-based characterisation of time-varying dynamical complexity in the Earth's magnetosphere

“…The hourly Dst index values have been widely used as a proxy of the magnetospheric ring current strength and, consequently, the intensity of geospace magnetic storms, which are considered the most complex phenomenon of magnetospheric dynamics (Gonzalez et al, 1994;Daglis, 2006 …”

Similarities between extreme events in the solar-terrestrial system by means of nonextensivity

“…Universality relates to the uncovering of a universal formula that describes with good approximation the same property on different systems (Zhou et al, 2006). For instance, de Arcangelis et al (2006) showed that the same empirical laws widely accepted in seismology also characterize, surprisingly, the size and time occurrence of solar flares. Recently, Balasis et al (2011a) provided evidence for universality in solar flare, magnetic storm and earthquake dynamics.…”

“…The presented similarities suggest that these apparently diverse phenomena may follow qualitatively similar physical mechanisms. For instance, de Arcangelis et al (2006) suggested that magnetic stress transfer in the solar corona plays the role of elastic stress redistribution on the Earths crust. We suggest that plasma pressure distribution in the inner magnetosphere could play the role of magnetic stress transfer in the solar corona and elastic stress redistribution on the Earths crust.…”

Prediction of SYM-H index during large storms by NARX neural network from IMF and solar wind data

“…Long-lasting large southward IMF (Interplanetary Magnetic Field) enables energy transfer from the solar wind to the magnetosphere to enhance greatly through magnetic reconnection at dayside magnetopause. Large interplanetary electric fields (IEF) break into geospace, leading to dramatically enhanced and earthward shifted ring currents which cause a rapid decrease in the horizontal component of the geomagnetic field on the ground at low latitudes and characterize a geomagnetic storm development (Gonzalez et al, 1994;Gosling et al, 1991;Tsurutani et al, 1988;Daglis, 2006). Satellite observations show that storm time ring current mainly consists of ions with energy from tens to hundreds keV which drift westward over the equatorial area within 2-7 R E height.…”

“…particles newly input into ring current decreases, the convection boundary moves outside, cold ionospheric plasma refills the exhausted inner magnetosphere, then encounters with energy particles, and thus gives rise to plasma waves. Ring current ions loss is caused through 4 kinds of processes such as charge exchanges with neutral atoms, Coulomb collisions with plasma, pitch angle diffusion caused by waveparticle interaction, as well as drifting out of the dayside magnetopause (Daglis, 2006), and thus the ring current decays. This is the recovery phase of a magnetic storm.…”