The solar wind exerts a pressure upon Mercury. How much is this at its perihelion?
According to "Physics of Solar System Plasmas" by Thomas E. Cravens (2004), p.282 it is
ρSW uSW2 = 1.3e-8 Pa
at the average distance of Mercury from the Sun (0.39AU). That estimate just scaled the average solar wind pressure measured at the Earth distance by r-2 to get the wind density at Mercury distance. This can be further corrected to get the pressure at the perihelion rperi=0.309AU :
PSWperi=1.3e-8*(0.39/0.309)2=2.1e-8 Pa.
This reasonably well agrees with the solar wind characteristics measured by Mariner 10 [see G. Siscoe, L. Christopher, Geophys. Res. Lett. 2 (1975), 158] at actual Mercury orbit radius.
A couple of remarks -- 1) this pressure varies within an order of magnitude with time; 2) the wind does not directly hit the Mercury surface, it is mostly deflected by the magnetosphere, as the data from Mariner 10 shows.
According to "Physics of Solar System Plasmas" by Thomas E. Cravens (2004), p.282 it is
ρSW uSW2 = 1.3e-8 Pa
at the average distance of Mercury from the Sun (0.39AU). That estimate just scaled the average solar wind pressure measured at the Earth distance by r-2 to get the wind density at Mercury distance. This can be further corrected to get the pressure at the perihelion rperi=0.309AU :
PSWperi=1.3e-8*(0.39/0.309)2=2.1e-8 Pa.
This reasonably well agrees with the solar wind characteristics measured by Mariner 10 [see G. Siscoe, L. Christopher, Geophys. Res. Lett. 2 (1975), 158] at actual Mercury orbit radius.
A couple of remarks -- 1) this pressure varies within an order of magnitude with time; 2) the wind does not directly hit the Mercury surface, it is mostly deflected by the magnetosphere, as the data from Mariner 10 shows.
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