caa a22 4500 445815884 CHVBK 20180317145228.0 cr unu---uuuuu 170323e20111201xx s 000 0 eng 10.1007/s11214-011-9828-2 doi (NATIONALLICENCE)springer-10.1007/s11214-011-9828-2 Upstream Ion Cyclotron Waves at Venus and Mars [Elektronische Daten] [Magda Delva, Christian Mazelle, César Bertucci] The occurrence of waves generated by pick-up of planetary neutrals by the solar wind around unmagnetized planets is an important indicator for the composition and evolution of planetary atmospheres. For Venus and Mars, long-term observations of the upstream magnetic field are now available and proton cyclotron waves have been reported by several spacecraft. Observations of these left-hand polarized waves at the local proton cyclotron frequency in the spacecraft frame are reviewed for their specific properties, generation mechanisms and consequences for the planetary exosphere. Comparison of the reported observations leads to a similar general wave occurrence at both planets, at comparable locations with respect to the planet. However, the waves at Mars are observed more frequently and for long durations of several hours; the cyclotron wave properties are more pronounced, with larger amplitudes, stronger left-hand polarization and higher coherence than at Venus. The geometrical configuration of the interplanetary magnetic field with respect to the solar wind velocity and the relative density of upstream pick-up protons to the background plasma are important parameters for wave generation. At Venus, where the relative exospheric pick-up ion density is low, wave generation was found to mainly take place under stable and quasi-parallel conditions of the magnetic field and the solar wind velocity. This is in agreement with theory, which predicts fast wave growth from the ion/ion beam instability under quasi-parallel conditions already for low relative pick-up ion density. At Mars, where the relative exospheric pick-up ion density is higher, upstream wave generation may also take place under stable conditions when the solar wind velocity and magnetic field are quasi-perpendicular. At both planets, the altitudes where upstream proton cyclotron waves were observed (8 Venus and 11 Mars radii) are comparable in terms of the bow shock nose distance of the planet, i.e. in terms of the size of the solar wind-planetary atmosphere interaction region. In summary, the upstream proton cyclotron wave observations demonstrate the strong similarity in the interaction of the outer exosphere of these unmagnetized planets with the solar wind upstream of the planetary bow shock. Springer Science+Business Media B.V., 2011 Venus nationallicence Mars nationallicence Upstream nationallicence Cyclotron waves nationallicence Ion pick-up nationallicence Exosphere nationallicence Delva Magda Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042, Graz, Austria aut Mazelle Christian CESR/UPS-CNRS, Toulouse, France aut Bertucci César Institute for Astronomy and Space Physics, IAFE, Buenos Aires, Argentina aut Space Science Reviews Springer Netherlands 162/1-4(2011-12-01), 5-24 0038-6308 162:1-4<5 2011 162 11214 https://doi.org/10.1007/s11214-011-9828-2 text/html Onlinezugriff via DOI 1 review-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11214-011-9828-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Delva Magda Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042, Graz, Austria aut NATIONALLICENCE 700 1- Mazelle Christian CESR/UPS-CNRS, Toulouse, France aut NATIONALLICENCE 700 1- Bertucci César Institute for Astronomy and Space Physics, IAFE, Buenos Aires, Argentina aut NATIONALLICENCE 773 0- Space Science Reviews Springer Netherlands 162/1-4(2011-12-01), 5-24 0038-6308 162:1-4<5 2011 162 11214 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer