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61 results on '"Simon Wedlund, Cyril"'

51. Plasma waves at Comet 67P/Churyumov-Gerasimenko: in the diamagnetic cavity and outside it

Author

EGU 2017 (23-28/04/2017: Vienna), Gunell, H., Altwegg, Kathrin, Cessateur, Gaël, De Keyser, Johan, Dhooghe, Frederik, Eriksson, Anders, Gibbons, Andrew, Glassmeier, Karl Heinz, Götz, Charlotte C G, Karlsson, T., Hamrin, Maria, Henri, Pierre, Maggiolo, Romain, Nilsson, Hans, Odelstad, Elias, Rubin, Martin, Simon Wedlund, Cyril, Stenberg Wieser, Gabriella, Tzou, Chiayu C.Y., Vallieres, Xavier, EGU 2017 (23-28/04/2017: Vienna), Gunell, H., Altwegg, Kathrin, Cessateur, Gaël, De Keyser, Johan, Dhooghe, Frederik, Eriksson, Anders, Gibbons, Andrew, Glassmeier, Karl Heinz, Götz, Charlotte C G, Karlsson, T., Hamrin, Maria, Henri, Pierre, Maggiolo, Romain, Nilsson, Hans, Odelstad, Elias, Rubin, Martin, Simon Wedlund, Cyril, Stenberg Wieser, Gabriella, Tzou, Chiayu C.Y., and Vallieres, Xavier

Abstract

info:eu-repo/semantics/nonPublished

Published
2017

52. Ion acoustic waves at comet 67P/Churyumov-Gerasimenko: Observations and computations

Author

Gunell, H., Nilsson, Hans, Hamrin, Maria, Eriksson, Anders, Odelstad, Elias, Maggiolo, Romain, Henri, Pierre, Vallieres, Xavier, Altwegg, Kathrin, Tzou, Chiayu C.Y., Rubin, Martin, Glassmeier, Karl Heinz, Wieser, Gabriella Stenberg, Simon Wedlund, Cyril, De Keyser, Johan, Dhooghe, Frederik, Cessateur, Gaël, Gibbons, Andrew, Gunell, H., Nilsson, Hans, Hamrin, Maria, Eriksson, Anders, Odelstad, Elias, Maggiolo, Romain, Henri, Pierre, Vallieres, Xavier, Altwegg, Kathrin, Tzou, Chiayu C.Y., Rubin, Martin, Glassmeier, Karl Heinz, Wieser, Gabriella Stenberg, Simon Wedlund, Cyril, De Keyser, Johan, Dhooghe, Frederik, Cessateur, Gaël, and Gibbons, Andrew

Abstract

Context. On 20 January 2015 the Rosetta spacecraft was at a heliocentric distance of 2.5 AU, 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. Aims. 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). Methods. 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. Results. 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 = 0.01 eV 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 1 eV, which leads to significant damping of the ion acoustic waves. Conclusions. 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., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2017

53. Plasma waves confined to the diamagnetic cavity of comet 67P/Churyumov-Gerasimenko

Author

Gunell, H., Götz, Charlotte C G, Eriksson, Anders, Nilsson, Hans, Simon Wedlund, Cyril, Henri, P, Maggiolo, Romain, Hamrin, Maria, De Keyser, Johan, Rubin, Martin, Stenberg Wieser, Gabriella, Cessateur, Gaël, Dhooghe, Frederik, Gibbons, Andrew, Gunell, H., Götz, Charlotte C G, Eriksson, Anders, Nilsson, Hans, Simon Wedlund, Cyril, Henri, P, Maggiolo, Romain, Hamrin, Maria, De Keyser, Johan, Rubin, Martin, Stenberg Wieser, Gabriella, Cessateur, Gaël, Dhooghe, Frederik, and Gibbons, Andrew

Abstract

info:eu-repo/semantics/published

Published
2017

54. Erratum: Evolution of the ion environment of comet 67P during the Rosetta mission as seen by RPC-ICA

Author

Nilsson, Hans, primary, Wieser, Gabriella Stenberg, additional, Behar, Etienne, additional, Gunell, Herbert, additional, Wieser, Martin, additional, Galand, Marina, additional, Simon Wedlund, Cyril, additional, Alho, Markku, additional, Goetz, Charlotte, additional, Yamauchi, Masatoshi, additional, Henri, Pierre, additional, Odelstad, Elias, additional, and Vigren, Erik, additional

Published
2017
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55. Investigating short-time-scale variations in cometary ions around comet 67P

Author

Stenberg Wieser, Gabriella, primary, Odelstad, Elias, additional, Wieser, Martin, additional, Nilsson, Hans, additional, Goetz, Charlotte, additional, Karlsson, Tomas, additional, André, Mats, additional, Kalla, Leif, additional, Eriksson, Anders I., additional, Nicolaou, Georgios, additional, Simon Wedlund, Cyril, additional, Richter, Ingo, additional, and Gunell, Herbert, additional

Published
2017
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56. Evolution of the ion environment of comet 67P during the Rosetta mission as seen by RPC-ICA

Author

Nilsson, Hans, primary, Wieser, Gabriella Stenberg, additional, Behar, Etienne, additional, Gunell, Herbert, additional, Wieser, Martin, additional, Galand, Marina, additional, Simon Wedlund, Cyril, additional, Alho, Markku, additional, Goetz, Charlotte, additional, Yamauchi, Masatoshi, additional, Henri, Pierre, additional, Odelstad, Elias, additional, and Vigren, Erik, additional

Published
2017
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57. Ion acoustic waves observed at Comet 67P/Churyumov-Gerasimenko

Author

AGU Fall Meeting, Gunell, H., Nilsson, H., Hamrin, N, Eriksson, A, Maggiolo, Romain, Henri, P, Altwegg, Kathrin, Tzou, C-Y, Rubin, Martin, Glassmeier, K.-H., Stenberg Wieser, Gabriella, Simon Wedlund, Cyril, De Keyser, Johan, Dhooghe, Frederik, Cessateur, Gaël, Gibbons, Andrew, AGU Fall Meeting, Gunell, H., Nilsson, H., Hamrin, N, Eriksson, A, Maggiolo, Romain, Henri, P, Altwegg, Kathrin, Tzou, C-Y, Rubin, Martin, Glassmeier, K.-H., Stenberg Wieser, Gabriella, Simon Wedlund, Cyril, De Keyser, Johan, Dhooghe, Frederik, Cessateur, Gaël, and Gibbons, Andrew

Abstract

info:eu-repo/semantics/nonPublished

Published
2016

61. Ion acoustic waves observed at Comet 67P/Churyumov-Gerasimenko

Author

Gunell, H., Nilsson, H., Hamrin, N., Eriksson, A., Maggiolo, Romain, Henri, P., Altwegg, Kathrin, Tzou, C-Y, Rubin, Martin, Glassmeier, K. -H, Stenberg Wieser, G., Simon Wedlund, Cyril, Johan De Keyser, Dhooghe, Frederik, Cessateur, Gaël, Gibbons, Andrew, and POTHIER, Nathalie

Subjects
Surfaces, [SDU] Sciences of the Universe [physics], Ices, Dust, PLANETARY SCIENCES: COMETS AND SMALL BODIES, Plasma and MHD instabilities
Abstract

We present observations of ion acoustic waves at Comet 67P/Churyumov-Gerasimenko performed on 20 January 2015 when the Rosetta spacecraft was located near the terminator, 28 km from the nucleus of the comet. At the time of the observations the activity of the comet was still low. We use distribution functions obtained by the Ion Composition Analyser of the Rosetta Plasma Consortium (RPC-ICA) and electron temperature estimatesfrom the Langmuir Probes (RPC-LAP) to compute dispersion relations for waves on the ion timescale, and compare the results to spectra obtained by RPC-LAP. The peaks of the wave spectra appear at frequencies near 500 Hz. We perform cross-calibrations between RPC-ICA, RPC-LAP, and the Mutual Impedance Probe (RPC-MIP). Matching the dispersion relations to the wave observations helps us to form an estimate of the plasma density. At times when there is significant wave activity the water ion distribution is constituted by a cold (0.01 eV) population of locally produced ions and a thin tail of ions that have been accelerated by an electric field. The tail is approximately unidirectional, covering a wide velocity range, and centred at 20km/s in the spacecraft frame. At other times a warm (approximately 1 eV), mainly isotropic, ion population renders the ion acoustic mode heavily damped, and no waves are observed. Observations of the neutral density by the ROSINA COPS instrument indicate that frictional heating by the radial neutral flow contributes to this warm ion population. This work was supported by the Belgian Science Policy Office through the Solar-Terrestrial Centre of Excellence and by PRODEX/ROSETTA/ROSINA PEA 4000107705.

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