Cometary Ions Detected By The Cassini Spacecraft 6.5 au Downstream Of Comet 153P/Ikeya-Zhang

Measured flux of pickup H+ from late 2001 to early 2003, divided by its average value, first presented as Figure 5 of McComas et al. [3]. The missing data point is for a time when no unambiguous pickup H+ data were available. The observed and modeled (smooth curve, see [3]) values show a factor of 2 increase as Cassini moved away from the center of the interstellar hydrogen shadow. The shaded region highlights the time period encompassing a statistically-significant increase in detected pickup protons, corresponding to the entire period covered in Figure 2.

During March-April 2002, while between the orbits of Jupiter and Saturn, the Cassini spacecraft detected a significant enhancement in pickup proton flux.

The most likely explanation for this enhancement was the addition of protons to the solar wind by the ionization of neutral hydrogen in the corona of comet 153P/Ikeya-Zhang. This comet passed relatively close to the Sun-Cassini line during that period, allowing pickup ions to be carried to Cassini by the solar wind.

This pickup proton flux could have been further modulated by the passage of the interplanetary counterparts of coronal mass ejections past the comet and spacecraft. The radial distance of 6.5 Astronomical Units (au) traveled by the pickup protons, and the implied total tail length of >7.5 au make this cometary ion tail the longest yet measured.

Geraint H. Jones, Heather A. Elliott, David J. McComas, Matthew E. Hill, Jon Vandegriff, Edward J. Smith, Frank J. Crary, J. Hunter Waite
Comments: Submitted to Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2006.00500 [astro-ph.EP] (or arXiv:2006.00500v1 [astro-ph.EP] for this version)
Submission history
From: Geraint Jones
[v1] Sun, 31 May 2020 12:08:27 UTC (5,459 KB)
Astrobiology, Astrochemistry

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