Lessons from Mars and Venus Lessons from Mars and Venus for the Solar Wind Interaction for the Solar Wind Interaction at Mercury at Mercury Markus Frä änz nz Markus Fr MPI fü ür r Sonnensystemforschung Sonnensystemforschung MPI f
Topics Topics � Upstream waves Upstream waves � � Bowshock Bowshock dynamics dynamics � � Instabilities Instabilities � Zhang 1991 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 2 2
Upstream waves Upstream waves waves observed at all planets observed at all planets waves Mars Trotignon 1 9 9 1 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 3 3
Proton Cyclotron Waves Proton Cyclotron Waves exited by pick- -up from exosphere up from exosphere exited by pick Measured by magnetic wave power Mars Measured by pick-up intensity Brain 2002 Mars Dubinin 2006 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 4 4
PCWs allow to determine exospheric profile at allow to determine exospheric profile at PCWs large distances large distances Mars Dubinin 2006 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 5 5
PCWs at Venus at Venus PCWs Delva 2009 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 6 6
Venus: Wave properties Venus: Wave properties Wei&Russell 2009 • Waves properties of the higher frequency waves (red) show that they are not locally generated and similar to the waves observed at 0.3 AU and 1 AU (by Jian et al., 2008), which are created near the Sun and convected outward with the solar wind. • The PCW and lower frequency waves (blue and green) are similar in many ways. 7 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 7 7
Upstream Waves Conclusions Upstream Waves Conclusions At all terrestrial planets waves related to the ion and electron foreshock are observed. Proton cyclotron waves are exited by pick-up from the exosphere. These are observed also outside of the foreshock and allow to determine the exospheric density profile. Respective pick-up ion intensities can also be directly observed for Mars. At Earth and Venus exospheric densities outside of the bow shock are very low. The observed low intensity proton cyclotron waves have recently been interpreted as originating in the solar corona. For Mercury we might expect waves related to sodium pick-up, but sodium cyclotron waves should have very low frequency . Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 8 8
Bow shock dynamics Bow shock dynamics Venus Venus Russell 1988 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 9 9
Bow shock dynamics Bow shock dynamics dynamic pressure dependence dynamic pressure dependence Mars Edberg 2009 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 10 10
Bow shock dynamics Bow shock dynamics clock angle dependence clock angle dependence Mars Vignes 2002 Mars Mazelle 2004 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 11 11
Bow shock dynamics Bow shock dynamics Conclusions Conclusions For Venus bow shock dynamics have been studied in great For Venus bow shock dynamics have been studied in great � � detail by PVO. detail by PVO. Solar wind dynamic pressure plays minor role for Mars and Solar wind dynamic pressure plays minor role for Mars and � � Venus. Venus. Also clock angle unimportant. Also clock angle unimportant. � � For Venus solar EUV has strongest impact, for Mars not For Venus solar EUV has strongest impact, for Mars not � � observed. observed. Second factor is upstream magnetosonic magnetosonic Mach number. Mach number. Second factor is upstream � � For Mercury dynamic pressure should be more important For Mercury dynamic pressure should be more important � � (as for Earth) since magnetopause is much more (as for Earth) since magnetopause is much more compressible than at Mars and Venus. compressible than at Mars and Venus. Also cusp dynamics may influence Mercury bowshock Also cusp dynamics may influence Mercury bowshock � � position. position. Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 12 12
Magnetosheath Instabilities Instabilities Magnetosheath Earth terminator region Earth terminator region 1998 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 13 13
Magnetosheath Instabilities Instabilities Magnetosheath Mars terminator region Mars terminator region Winningham 2006 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 14 14
Magnetosheath Instabilities Instabilities Magnetosheath Venus Venus Pope 2009 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 15 15
Magnetosheath Instabilities Instabilities Magnetosheath Mercury Mercury Slavin 2008 Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 16 16
Magnetosheath Instabilities Instabilities Magnetosheath Conclusions Conclusions ULF waves observed in at Earth flank magnetopause have ULF waves observed in at Earth flank magnetopause have � � been interpreted as being caused by Kelvin- - Helmholtz Helmholtz been interpreted as being caused by Kelvin instability for some time. instability for some time. Similar ULF waves have been observed at Mars, Venus and Similar ULF waves have been observed at Mars, Venus and � � Mercury Mercury At Mars and Venus the waves lead to a filamentation filamentation of the of the At Mars and Venus the waves lead to a � � magnetosheath magnetosheath To explain monochromatic character only growth against To explain monochromatic character only growth against � � magnetospheric field gradient was considered. field gradient was considered. magnetospheric Theory of KH- - wave propagation into wave propagation into magnetosheath magnetosheath is is Theory of KH � � currently being developed by N.Borisov currently being developed by N.Borisov Mirror mode waves are observed at Earth close to Mirror mode waves are observed at Earth close to � � stagnation point. stagnation point. Similar magnetic structure has been interpreted as mirror Similar magnetic structure has been interpreted as mirror � � mode at Venus as mirror mode - - but could not be but could not be mode at Venus as mirror mode confirmed by particle observations. confirmed by particle observations. Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 17 17
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