Slow-moving transient sparks vivid auroras around the Arctic circle


Solar wind parameters reflected the arrival of a slow-moving transient at approximately 08:23 UTC on January 11, 2021. At this time, density, temperature, and wind speed increased, sparking vivid auroras around the Arctic circle.

The cause of the shock wave might have been filament eruption on January 8, which was not expected to affect Earth.

As the day progressed, total field strength saw an increase to 20 nT, the Bz component saw a maximum southward deflection to -18 nT, and wind speeds increased to peak over 460 km/s.

Solar wind parameters are expected to remain enhanced early on January 12 as effects from the slow-moving transient continues and combines with the onset of the positive polarity CH HSS.

Nominal conditions are expected to return on January 13 and 14.

The geomagnetic field is expected to be at quiet to unsettled levels, with a chance for an isolated active period, early on January 12 as the influence from the transient persists.

Quiet conditions are expected to return late on January 12 and continue into January 13 and 14.

Featured image: Pink aurora over Tromso, Norway on January 11, 2021. Credit: Markus Varik via

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