A comparison between VEGA 1, 2 and Giotto flybys of comet 1P/Halley: implications for Rosetta

摘要

Three flybys of comet 1P/Halley, by VEGA 1, 2 and Giotto, are investigatedwith respect to the occurrence of mirror mode waves in the cometosheath andfield line draping in the magnetic pile-up region around the nucleus. Thetime interval covered by these flybys is approximately 8 days, which is alsothe approximate length of an orbit or flyby of Rosetta around comet67P/Churyumov–Gerasimenko. Thus any significant changes observed aroundHalley are changes that might occur for Rosetta during one pass of 67P/CG. Itis found that the occurrence of mirror mode waves in the cometosheath isstrongly influenced by the dynamical pressure of the solar wind and theoutgassing rate of the comet. Field line draping happens in the magneticpile-up region. Changes in nested draping regions (i.e. regions withdifferent directions) can occur within a few days, possiblyinfluenced by changes in the outgassing rate of the comet and thereby theconductivity of the cometary ionosphere.