Prof. Rickard Lundin (IRF)Date:
AulaPlanetary magnetic fields and solar forcing - critical aspects for the evolution of the earth-like planets
The Earth-like planets: Mercury, Venus, Earth and Mars have in common that they are closest to the Sun (0.3-1.5 AU). This makes them subject to intense solar radiation- and solar wind forcing. Specific properties, like their differences in intrinsic magnetization, make them evolve in different ways. Under the assumption that all Earth-like planets accreted from matter of essentially the same chemical origin, the differences we observe today must have been due to differences in evolution. This is particularly important for the evolution of volatiles on a planet. The Earth is the only planet where a significant hydrosphere remains. The question is therefore, what happened with the water on the other Earth-like planets? Moreover, what major mechanisms are responsible for the differentiation we can see today in the respective atmosphere of the Earth-like planets?
A hypothesis put forward during recent years is that solar wind interaction with the topside atmosphere and ionosphere leads to a long-term change of planetary atmospheres. The interaction is particular effective for celestial bodies with low gravity and/or without magnetic shielding to fend off the solar wind from reaching the upper atmosphere and ionosphere. The solar wind affects primarily the ionized part of a planetary atmosphere, but direct sputtering is also a relevant scavenging process. Lacking magnetic shielding the energy and momentum of the solar wind is capable of fast erosion if the target area is sufficiently large (e.g. the expanding coma of a comet). The evolution of volatiles (atmosphere, hydrosphere) on the Earth-like planets with their differences in gravity, distance to the Sun and magnetic shielding will be discussed in view of the solar wind erosion process. Created 2005-10-13 15:13:23 by Rick McGregorLast changed 2005-10-13 15:14:16 by Rick McGregor