Magnetic Flux

Magnetic flux is a measurement of how much magnetic field passes through a given area, and it's one of the most useful tools scientists have for tracking how much magnetic energy is building up in a region of the Sun or how strongly the solar wind's magnetic field is coupling with Earth's magnetosphere. Think of magnetic field lines as if they were real, countable threads; the more of those threads pass through a surface, and the more tightly packed together they are, the higher the magnetic flux. On the Sun, regions with high magnetic flux appear as sunspots, and the total flux emerging in an active region is one of the strongest predictors of how likely that region is to produce a significant solar flare. In Earth's space environment, the concept applies to how much of the interplanetary magnetic field's flux successfully connects, or reconnects, with Earth's own magnetic field — the more efficiently this happens, particularly when the field points southward, the more energy gets transferred into the magnetosphere, fueling geomagnetic storms and auroras. Magnetic flux is measured in units called webers, or more commonly for solar physics in maxwells, and satellite magnetographs routinely map its distribution across the Sun's visible surface to help forecasters anticipate space weather.