Lessons from Mars and Venus Lessons from Mars and Venus for the - - PowerPoint PPT Presentation

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 Fr Markus Frä änz nz MPI f MPI fü ür r Sonnensystemforschung Sonnensystemforschung

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 2 2

Topics Topics

• Upstream waves

Upstream waves

• Bowshock

Bowshock dynamics dynamics

• Instabilities

Instabilities

Zhang 1991

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 3 3

Upstream waves Upstream waves

waves waves observed at all planets

• bserved at all planets

Mars Trotignon 1 9 9 1

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 4 4

Proton Cyclotron Waves Proton Cyclotron Waves

exited by pick exited by pick-

• up from exosphere

up from exosphere

Measured by magnetic wave power Measured by pick-up intensity Mars Brain 2002 Mars Dubinin 2006

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 5 5

PCWs PCWs allow to determine exospheric profile at allow to determine exospheric profile at large distances large distances

Mars Dubinin 2006

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 6 6

PCWs PCWs at Venus at Venus

Delva 2009

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 7 7

7

Venus: Wave properties Venus: Wave properties

• 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.

Wei&Russell 2009

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 8 8

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 9 9

Bow shock dynamics Bow shock dynamics Venus Venus

Russell 1988

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 10 10

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 11 11

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 12 12

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

• bserved.
• bserved.
• Second factor is upstream

Second factor is upstream magnetosonic magnetosonic Mach number. Mach number.

• 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

Also cusp dynamics may influence Mercury bowshock bowshock position. position.

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 13 13

Magnetosheath Magnetosheath Instabilities Instabilities

Earth terminator region Earth terminator region

1998

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 14 14

Magnetosheath Magnetosheath Instabilities Instabilities

Mars terminator region Mars terminator region

Winningham 2006

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 15 15

Magnetosheath Magnetosheath Instabilities Instabilities Venus Venus

Pope 2009

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 16 16

Magnetosheath Magnetosheath Instabilities Instabilities Mercury Mercury

Slavin 2008

Mars/ Venus Solar Wind Interaction Mars/ Venus Solar Wind Interaction 17 17

Magnetosheath Magnetosheath Instabilities Instabilities

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 been interpreted as being caused by Kelvin-

• Helmholtz

Helmholtz 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

At Mars and Venus the waves lead to a filamentation filamentation of the

• f the

magnetosheath magnetosheath

• To explain monochromatic character only growth against

To explain monochromatic character only growth against magnetospheric magnetospheric field gradient was considered. field gradient was considered.

• Theory of KH

Theory of KH-

• wave propagation into

wave propagation into magnetosheath magnetosheath is is currently being developed by currently being developed by N.Borisov 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 mode at Venus as mirror mode -

• but could not be

but could not be confirmed by particle observations. confirmed by particle observations.