Cometary ion drift energy and temperature at comet 67P/Churyumov–GerasimekoShow others and affiliations
2024 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 533, p. 2980-2990Article in journal (Refereed) Published
Abstract [en]
The Ion Composition Analyzer (ICA) on the Rosetta spacecraft observed both the solar wind and the cometary ionosphere around comet 67P/Churyumov–Gerasimenko for nearly two years. However, observations of low energy cometary ions were affected by a highly negative spacecraft potential, and the ICA ion density estimates were often much lower than plasma densities found by other instruments. Since the low energy cometary ions are often the highest density population in the plasma environment, it is nonetheless desirable to understand their properties. To do so, we select ICA data with densities comparable to those of Rosetta’s Langmuir Probe (LAP)/Mutual Impedance Probe (MIP) throughout the mission. We then correct the cometary ion energy distribution of each energy-angle scan for spacecraft potential and fit a drifting Maxwell–Boltzmann distribution, which gives an estimate of the drift energy and temperature for 3521 scans. The resulting drift energy is generally between 11–18 eV and the temperature between 0.5–1 eV. The drift energy shows good agreement with published ion flow speeds from LAP/MIP during the same time period and is much higher than the cometary neutral speed. We see additional higher energy cometary ions in the spectra closest to perihelion that would be well described by a second Maxwellian-like distribution. The energy and temperature are negatively correlated with heliocentric distance, with a stronger dependence on heliocentric distance for temperature. It cannot be quantitatively determined whether this trend is primarily due to heliocentric distance or spacecraft distance to the comet, which increased with decreasing heliocentric distance.
Place, publisher, year, edition, pages
Oxford University Press, 2024. Vol. 533, p. 2980-2990
Keywords [en]
comets: individual: 67P, methods: data analysis, plasmas, space vehicles: instruments
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:umu:diva-229414DOI: 10.1093/mnras/stae1883ISI: 001299560400006Scopus ID: 2-s2.0-85201862386OAI: oai:DiVA.org:umu-229414DiVA, id: diva2:1896283
Funder
Swedish National Space Board, 2021–000105Swedish National Space Board, 132/192024-09-102024-09-102024-09-10Bibliographically approved