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Communication Dans Un Congrès Année : 2019

Plasma density at comet 67P from 1.25 to 3.8 AU

Résumé

The Rosetta dual Langmuir Probe instrument (LAP) of the Rosetta Plasma Consortium (RPC) on-board the ESA Rosetta spacecraft operated from August 2014 to September 2016 to characterise the plasma environment in the cometary ionosphere of 67P/Churyumov-Gerasimenko. The latest cross-calibrational efforts between the Mutual Impedance Probe (MIP) and LAP yielded a high-time resolution density dataset over the course of the mission, with unprecedented temporal coverage and dynamic range to resolve the dynamic environment of the comet, and was recently delivered to the Planetary Science Archive. We follow and characterise the plasma environment from the lowest densities with the earliest cometary activity signatures to peak densities at around 6000 cm-3, where fluctuations of order of magnitudes can be seen within minutes, substantially faster and often orders of magnitudes larger fluctuations than the neutral gas environment. We show statistics of the density, establish time scales of the dynamics and discuss physical interpretations.

To combine the high time resolution and wide dynamic range of the Langmuir probes with the absolute accuracy of the mutual impedance measurement and overcome spacecraft sheath effects on the Langmuir probe measurements, the cross-calibration effort recovers the density by considerations of the effective electron temperature, effective ion energy, EUV flux and spacecraft potential. We report these parameters over the entire mission with a resolution of 48 to three hours and investigate their individual roles as drivers of ionisation and compare to the plasma density fluctuations beyond the neutral gas fluctuation.

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Dates et versions

hal-03563826 , version 1 (10-02-2022)

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F. L. Johansson, A. Eriksson, E. Odelstad, E. Vigren, P. Henri, et al.. Plasma density at comet 67P from 1.25 to 3.8 AU. American Geophysical Union, 2019, San Francisco, United States. ⟨hal-03563826⟩
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