Ionosphere

The ionosphere is the part of a planetary atmosphere where there is not enough gas for ionized molecules to combine and become neutral again, so the region stays ionized.

The ionosphere is caused by photoionization due to ultraviolet emission from a stellar body. Since it is a plasma it can be pushed around by the planet's magnetic field, especially when the field is compressed by a strong solar flare. The solar wind normally interacts directly with the ionosphere only near the magnetic poles, where it produces aurorae.