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J/A+A/600/A3        Comet ion acoustic waves code             (Gunell+, 2017)

Ion acoustic waves at comet 67P/Churyumov-Gerasimenko. Observations and computations. Gunell H., Nilsson H., Hamrin M., Eriksson A., Odelstad E., Maggiolo R., Henri P., Vallieres X., Altwegg K., Tzou C.-Y., Rubin M., Glassmeier K.-H., Stenberg Wieser G., Simon Wedlund C., De Keyser J., Dhooghe F., Cessateur G., Gibbons A. <Astron. Astrophys. 600, A3 (2017)> =2017A&A...600A...3G (SIMBAD/NED BibCode)
ADC_Keywords: Comets ; Models Keywords: comets: general - comets: individual: 67P/Churyumov-Gerasimenko - instrumentation: detectors - methods: analytical - plasmas - waves Abstract: On 20 January 2015 the Rosetta spacecraft was at a heliocentric distance of 2.5AU, accompanying comet 67P/Churyumov-Gerasimenko on its journey toward the sun. The Ion Composition Analyser (RPC-ICA), other instruments of the Rosetta Plasma Consortium, and the ROSINA instrument made observations relevant to the generation of plasma waves in the cometary environment. Observations of plasma waves by the Rosetta Plasma Consortium Langmuir probe (RPC-LAP) can be explained by dispersion relations calculated based on measurements of ions by the Rosetta Plasma Consortium Ion Composition Analyser (RPC-ICA), and this gives insight into the relationship between plasma phenomena and the neutral coma, which is observed by the Comet Pressure Sensor of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument (ROSINA-COPS). We use the simple pole expansion technique to compute dispersion relations for waves on ion timescales based on the observed ion distribution functions. These dispersion relations are then compared to the waves that are observed. Data from the instruments RPC-LAP, RPC-ICA and the mutual impedance probe (RPC-MIP) are compared to find the best estimate of the plasma density. We find that ion acoustic waves are present in the plasma at comet 67P/Churyumov-Gerasimenko, where the major ion species is H2O+. The bulk of the ion distribution is cold, kBTi=0.01eV when the ion acoustic waves are observed. At times when the neutral density is high, ions are heated through acceleration by the solar wind electric field and scattered in collisions with the neutrals. This process heats the ions to about 1eV, which leads to significant damping of the ion acoustic waves. In conclusion, we show that ion acoustic waves appear in the H2O+ plasmas at comet 67P/Churyumov-Gerasimenko and how the interaction between the neutral and ion populations affects the wave properties. Description: The general package for dispersion relations and fluctuation calculations using simple pole expansions is in the directory named simple. The directory ThisPaper contains files that are specific to the present paper. ThisPaper/startup.m sets up paths and physical constants. ThisPaper/aa16appendix.m plots the figure in the appendix. ThisPaper/aa16figs7to9.m performs the computations behind Figs. 7-9 and plots those figures. ThisPaper/aa16fig6.m performs the computations behind Fig. 6 and plots it. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file ThisPaper/* 0 5 Files specific to the present paper simple/* 0 20 General package for dispersion relations and fluctuation calculations using simple pole expansions
Acknowledgements: Herbert Gunell, herbert.gunell(at)physics.org
(End) Patricia Vannier [CDS] 23-Jan-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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