Abstract
Abstract. Three flybys of comet 1P/Halley, by VEGA 1, 2 and Giotto, are investigated with respect to the occurrence of mirror mode waves in the cometosheath and field line draping in the magnetic pile-up region around the nucleus. The time interval covered by these flybys is approximately 8 days, which is also the approximate length of an orbit or flyby of Rosetta around comet 67P/Churyumov–Gerasimenko. Thus any significant changes observed around Halley are changes that might occur for Rosetta during one pass of 67P/CG. It is found that the occurrence of mirror mode waves in the cometosheath is strongly influenced by the dynamical pressure of the solar wind and the outgassing rate of the comet. Field line draping happens in the magnetic pile-up region. Changes in nested draping regions (i.e. regions with different Bx directions) can occur within a few days, possibly influenced by changes in the outgassing rate of the comet and thereby the conductivity of the cometary ionosphere.
Highlights
In this new era of cometary physics, which started with the arrival of the Rosetta spacecraft (Glassmeier et al, 2007) at comet 67P/Churyumov–Gerasimenko (67P/CG) on 6 August 2014, it is worthwhile to take another look at previous satellite encounters with comets
Two different processes are discussed in this paper, first the presence and generation of mirror mode waves in the cometosheath and the magnetic field line draping around the nucleus in the magnetic pile-up region
This shows that on time scales longer than 20 min the magnetic field strongly rotates in the xy plane for Giotto, with mainly Bx variations, whereas it remains rather constant for VEGA 1 with major negative By component and VEGA 2 with major positive Bx component
Summary
In this new era of cometary physics, which started with the arrival of the Rosetta spacecraft (Glassmeier et al, 2007) at comet 67P/Churyumov–Gerasimenko (67P/CG) on 6 August 2014, it is worthwhile to take another look at previous satellite encounters with comets. In order to simulate Rosetta orbiting 67P/CG and the changes that can be expected in the comet–solar wind interaction, three flybys of comet 1P/Halley by VEGA 1, 2 and Giotto are used. These flybys, within a time span of 8 days showed significant differences in the interaction in the plasma data; a similar data set will be generated by the Rosetta Plasma Consortium (RPC, Glassmeier et al, 2007) at 67P/CG. Note that these data are obtained in shocked solar wind, i.e. within the cometosheath (the region between the bow shock and the ionopause).
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