Parks et al. [2012] found the entropy of electrons are increased across the Earth's bow shock. Based on the Vlasov equation or the entropy conservation equation, the entropy of electrons are almost unchanged if their distribution is symmetrical (e.g. Maxwellian, flat-top etc.). What are your views on this?
Article Entropy Generation across Earth's Bow Shock
The answer is in the question. Firstly, most of the distributions are not maxwellian in the magnetosphere, that is moslty loss cone and anti loss cone and power distribution and so on. Even if the distribution is maxwellian it will get remodified due to the various acceleration mechanisms of the particles, gain energy from the solar wind. It is not much difficulty in understanding that the bow shock region is a dynamicall unbalanced region, so the magnetic field pressure and the particle pressure will be highly fluctuating (beta), So the entropy should change and energy is definitely from the solar wind may little bit from earths magnetic field
Many thanks, Sunitha. I still have a question. In thermodynamics books, weusually discuss the entropy of an ideal gas or a particle system. Is there any theory can describe the entropy of the whole system of space plasmas (including particles and fields)?
If the magnetic field of the shock is removed, does the entropy change of the particles can maintain without binary collision ?
I don't know what happened on Bowshock. But in reconnection, which is a highly dissipative process in space, the entropy increases even in collisionless limit.
The entropy increases, or say the dissipation is caused by the non-ideal terms in the generalized ohm'a law, such as the divergence of pressure tensor or inertial term. I think similar physical process also occurs in bowshock. Although asymmetrical electron distribution can lead to such non-ideal terms, it is not a necessary condition for the existence of non-ideal terms.
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