Solar wind entry into the high-latitude terrestrial magnetosphere during geomagnetically quiet times

Abstract

An understanding of the transport of solar wind plasma into and throughout the terrestrial magnetosphere is crucial to space science and space weather. For non-active periods, there is little agreement on where and how plasma entry into the magnetosphere might occur. Moreover, behaviour in the high-latitude region behind the magnetospheric cusps, for example, the lobes, is poorly understood, partly because of lack of coverage by previous space missions. Here, using Cluster multi-spacecraft data, we report an unexpected discovery of regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps. From statistical observational facts and simulation analysis we suggest that these regions are most likely produced by magnetic reconnection at the high-latitude magnetopause, although other processes, such as impulsive penetration, may not be ruled out entirely. We find that the degree of entry can be significant for solar wind transport into the magnetosphere during such quiet times.

Substorm simulation: Quiet and N‐S arcs preceding auroral breakup

“…Shi et al . [] found localized regions of high‐density ions in the lobe. The pitch angle distribution of the ions is almost isotropic, and the characteristic energy is ~ keV.…”

North‐south asymmetries in cold plasma density in the magnetotail lobes: Cluster observations

“…One end of the magnetic field lines of the lobes connects to the solar wind downtail, and the other end connects to the polar cap of the ionosphere. The plasma density is very low, and the plasma is predominantly of ionospheric origin [e.g., Chappell et al , , ], though there is also some transfer of plasma from the solar wind across the magnetopause [e.g., Hultqvist et al , ; Shi et al , , and references therein]. Filling of lobe flux tubes starts with ionization of atoms and gas molecules in the thermosphere, accompanied by upflow due to thermal and electromagnetic forces.…”

Solar wind penetration into the high-latitude magnetosphere: Cluster observations

“…Many people concentrate on the mechanism of the solar wind plasma entry into the magnetosphere during the IMF northward period, such as the high-latitude magnetic reconnection [3,4], impulsive penetration, the low latitudes instabilities or gradient drift. In this paper, we find that when the IMF is northward, although the formation of the entry layers depends on the direction of IMF, we pointed out that it mainly depends on the IMF Bx component and the influences of IMF By component could be weak.…”

“…There are many possible mechanisms such as high-latitude magnetic reconnection [3,4], impulsive penetration [5], the low latitudes instabilities [6] and gradient drift [7]. During the quiet times when the interplanetary magnetic field (IMF) is northward, using Cluster multi-spacecrafts observation data between August to October each year from 2002 to 2004, Shi et al (2013) reported some new regions of solar wind entry into the Earth's high-latitude magnetosphere tailward of the cusps where the solar wind plasmas penetrate into magnetosphere through the mechanism of high-latitude magnetic reconnection. In this paper, we used another period Cluster data which is between January to April each year from 2001 to 2006 to make further research on the transmission characteristics of the solar wind plasmas.…”