Geomagnetism

Nothing. That answer might surprise you, but the fact that the field occasionally reverses is simply a property of the continuous, on-going behavior of the Earth's dynamo. There is no "cause" per se.
Most material is non-magnetic, being composed of molecules made of atoms, each of which have electrons orbiting nuclear protons, where the motion of one electron, essentially a tiny electric current, generates a magnetic field that is cancelled by the
At most places on the Earth's surface, the compass doesn't point exactly toward geographic north.
Aurorae is the plural of the word "aurora," which is a luminous glow of the upper atmosphere caused by energetic particles descending from the Earth's magnetosphere or coming directly from the Sun.
Space weather is the state of the environment in space near the Earth, including the solar wind and the Sun's magnetic field, the outer part of the Earth's magnetic field called the magnetosphere, and the electrically conducting part of the Earth's atm
Not directly. High-altitude pilots and astronauts can experience enhanced levels of radiation during magnetic storms, but the hazard is due to the radiation, not the magnetic field itself.
This is a question more about health than geophysics; nonetheless, it is a question we are often asked.
A magnetic storm is a period of rapid magnetic field variation
The infrastructure and activities of our modern technologically-based society can be adversely affecte
Models and charts of the magnetic field at the Earth's surface need to be periodically updated because the field is constantly changing in time.