The solar wind is the outward plasma flow from the Sun, carrying an interplanetary magnetic field. Its pressure and field compress intrinsic planetary magnetospheres, form magnetotails, and can drive an induced magnetosphere around a planet with no appreciable intrinsic field.
Magnetic flux freezing in a highly conducting solar wind can carry open magnetic field lines outward. A nearly radial flux tube occupying fixed solid angle has area proportional to , so constant magnetic flux gives . If a field is approximately dipolar inside an opening radius and radial beyond it, its radial component at is enhanced by order compared with continued dipolar decay. Opposite polarities preserve zero net flux through a closed surface; this approximation does not introduce a magnetic monopole.
A terrestrial planet with a thin present atmosphere and evidence of a different past volatile and climate history.
A Martian geological interval between the Noachian and Amazonian, with extensive volcanic and aqueous activity. Numerical boundary ages depend on the crater chronology model.
An early interval of Martian geological history, identified by ancient cratered terrains and extensive records of aqueous alteration.
An ice giant with substantial heavy material beneath its H/He envelope. Its low intrinsic luminosity makes efficient, fully mixed cooling an imperfect universal assumption.
A gas giant with a substantial H/He envelope. Intrinsic cooling, contraction and helium differentiation contribute to its thermal evolution.
Removing helium from a hydrogen-rich envelope lowers He/H and raises its reciprocal H/He. A helium-rain explanation of atmospheric depletion must keep those two ratio conventions distinct. Settling helium-rich material can release gravitational energy while changing atmospheric composition; excess luminosity alone does not uniquely determine the interior process.
