[Magnetic reconnection]

Project work suggestion / Examensarbeten (30 hp)

High fluxes of suprathermal electrons in the Earth magnetotail

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Goal

Study the source regions of high energy suprathermal electrons in the Earth magnetotail using ESA Cluster satellite observations during 12 years of its mission.

Background

Cluster consists of 4 spacecraft with orbit apogee at 19 Earth radii. Since 2001 Cluster has collected large database of Earth magnetotail observations under different conditions (different phases of solar cycle, different solar wind conditions, different stages of reconnection, etc.). This allows to address statistically many important science topics where previously mainly event based studies have been carried out. Cluster spacecraft allow the most detailed 3D in situ observations of plasma that are accessible experimentally and the obtained knowledge can be of importance not only understanding Earth magnetosphere but even understanding such physically very distant phenomena as solar flares.

Project

One topic of very high importance is the suprathermal (energies manyfold larger than thermal energies) electron acceleration in the Earth magnetotail. For example, much of our knowledge on distance solar flares, is based on X-ray emissions generated by similar suprathermal electrons in the Suns corona. The suprathermal electrons can be observed in situ in the Earth magnetotail and are believed to be created due to magnetic reconnection and associated physical processes. There have been detailed event studies of such suprathermal electron acceleration within magnetic islands of tail current sheet during magnetic reconnection, or magnetic flux pile up regions created due to reconnection jets. Numerical simulations have suggested different possible acceleration mechanisms. However, statistically it has not been resolved what is the most efficient mechanism generating these electrons in the Earth magnetotail. The large database of Cluster would allow to address this question. The goal of the project would be to identify all Cluster events where suprathermal electrons show localized high fluxes, thus suggesting that Cluster is passing through the electron generation region, and classify these regions based on the properties of the magnetic field and plasma. For example, are these regions in the center of current sheet, at the front of magnetic pile up regions, within magnetic islands etc.

Plan