P_dyn (wind ram pressure)
P_B(r) (dipole pressure)
Dipole field lines
Every magnetized planet holds the stellar wind at bay by balancing its dipole magnetic pressure against the wind's ram pressure. This 2D companion draws that balance directly as two curves on a pressure-vs-distance graph — the magnetopause standoff distance is literally where they cross — and below it, a meridian cross-section shows the dipole field lines and the deflected stellar-wind stream around the same computed boundary. Move the planet closer to its star, weaken its magnetic moment, or crank up stellar activity and watch the crossing point slide inward, sometimes collapsing onto the planet itself.