Breathless news reports indicate magnetic fluctuations, and one has even blamed it for an earthquake. (Not likely.)
The K index comes out every 3 hours, and measures the most disturbed of three axes on standard magnetometers on a quasi-logarithmic scale from one to nine. The high latitudes will be affected first. Paths from places like Japan will degrade. When the Boulder ("WWV") K index rises, you know it's happening.