This is important work, which compliments terrestial geomagnetic measurements and space based observations.
The earth's magnetic field results from a planetary dynamo. Magnetic field lines get frozen into the electrically conductive fluid core. Then, differential motions in the fluid causes the magnetic field to get twisted up -- it's no longer is the simple dipole (like those bar magnets that you played with as a kid). Instead, the earth's magnetic field develops high order moments (sorta like bumps and dips). These shapes evolve as the conductive core moves. Eventually, the magnetic field gets so tangled up, that it unravels. At that time, the earth's field reverses. These magnetic field reversals show up in the geologic record
Measurements like the ESA Swarm satellite give us a handle on the evoloution of the Earth's magnetic field, as well as showing how that field interacts with the magnetic and particle environment of the solar wind.
(disclaimer - most of what I just posted is from a terrific graduate class that I took at the Lunar & Planetary Labs way back in 1979, and when I worked with Charles Sonett, who studied the solar wind. Likely, much of this is way out of date!)