Rapid flux transport in the central plasma sheet

Authors

  • R. Schödel,

  • W. Baumjohann,

  • R. Nakamura,

  • V. A. Sergeev,

  • T. Mukai


Abstract

On the basis of several years of Geotail data we performed a comprehensive statistical analysis of rapid convective transport in the neartail and midtail central plasma sheet. We chose a new approach by using flux transport and not ion bulk velocity as the threshold parameter for the identification of rapid flows. This criterion for rapid convection is independent of the radial distance from the Earth. We found that the occurrence rate of earthward rapid flux transport events was constant at radial distances >15 RE and that it started to drop only earthward of 15 RE. Tailward rapid flux transport events with Bz < 0 were extremely rare inside of 20 RE. Their occurrence rate increased strongly beyond that distance. Tailward directed events with Bz > 0 could be seen at all distances. Their occurrence rate has a minimum at radial distances between 20 and 30 RE and increases earthward and tailward of that region. They are likely to have a different nature and different origins in the near-Earth region and in the midtail beyond about 25–30 RE. In close analogy to bursty bulk flows we defined rapid convection events by using the flux transport criterion instead of a velocity criterion. We found that rapid convection events transport about the same amount of mass, energy, and magnetic flux and have about the same duration at all radial distances between 10 and 50 RE. We found that rapid convection was responsible for 30–50% of the observed total transport of mass, energy, and magnetic flux past Geotail at all observed distances in the central plasma sheet.

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