Plasmoid Formation and Acceleration in the Solar Streamer Belt

The dynamical behavior of a con—guration consisting of a plane —uid wake —owing in a current sheet embedded in a plasma sheet that is denser than its surroundings is discussed. This con—guration is a useful model for a number of structures of astrophysical interest, such as solar coronal streamers, com- etary tails, the Earths magnetotail and Galactic center nonthermal —laments. In this paper, the results are applied to the study of the formation and initial motion of the plasma density enhancements observed by the Large-Angle Spectrometric Coronagraph (LASCO) instrument onboard the Solar and Heliospheric Observatory (SOHO) spacecraft. It is found that beyond the helmet cusp of a coronal streamer, the magnetized wake con—guration is resistively unstable, that a traveling magnetic island develops at the center of the streamer, and that density enhancements occur within the magnetic islands. As the massive magnetic island travels outward, both its speed and width increase. The island passively traces the acceleration of the inner part of the wake. The values of the acceleration and density contrasts are in good agreement with LASCO observations. Subject headings: MHDSun: coronaSun: magnetic —eldssolar wind