During yesterday's major X1.0 solar flare (17:35 - 17:54 UTC) a rare event called Magnetic crochet occurred. Magnetic crochet, also known as Solar Flare Effect, occurs during fast impulsive flares and is described as a ripple in Earth's magnetic field caused by electrical currents flowing in air, about 60 to 150 km above the surface of the Earth.
According to IPS, a Magnetic crochet arises from the increased ionisation in the D and E layers of the ionosphere caused by the massive increase in X-ray radiation generated by the solar flare. This ionisation changes the properties (especially the conductivity) of these ionospheric layers allowing electric currents to flow more easily.
It is the magnetic effect of these currents which produce the jump in the Earth's magnetic field. As the flare declines, the ionospheric layers quickly return to their previous state, the electric currents in the layers return to normal, and the change in the magnetic field ends.
Magnetic crochets are quite rare because they are only observed during large flares which rise to a peak very quickly. Also, they are mostly observed in locations close to the sub-solar point (i.e. the point on Earth when the sun is overhead).
Most of the yesterday's CME is directed north, but there appears to be a faint Earth-directed component that could deliver a glancing blow to our planet's magnetic field on April 1/2.
Featured image: NASA SDO