1. The problem statement, all variables and given/known data Hi! I need to calculate the subsolar magnetopause distance (r_mp) when the distance to Earth is 0.4 AU. I have all the formulas and the data, but I still don’t get a reasonable value (it’s too small!) Here is what I know: Solar wind density: 5 cm^-3 (rho_sw) Solar wind speed=400 km/s (u_sw) Magnetic field at Earth’s surface= 5*10^-6 T (B_E) u_0= magnetic constant permeability= 4*pi*10-7 T m/A 2. Relevant equations 3. The attempt at a solution First I start to calculate the thermal pressure: p= rho_sw*(u_sw)^2 next, the magnetic field when the distance is 0.4 AU, where r= 1AU * 0.4: B(0.4)=B_E*(R_E/r) And finally I use the following equation to get the distance I am searching for in term of Earth radius R_E: (r_mp/R_E)=[(2*B(r)^2)/( u_0*p)]^1/6 But as I mentioned, the value is not “the right one”. Can I get help from someone? Thanks!