Aurora's painting the sky
On November 20, polar light was visible, even on low latitudes!

Last week we expected some firework from the returning monster sunspot groups of previous rotation. The expectations were only partially filled in.

The week started promising. From Nov 17 to Nov 20, 10 M flares were counted, all coming from sunspot group 90 (NOAA 0501). On Nov 18, the SIDC software CACTUS, Computer Aided CME tracking, detected a full halo CME in LASCO images. The CME was associated with the M3.2 and M3.9 flares, which were closely related in space and time through a complex activity process of sunspot group 90.

Click on the blue LASCO for a movie.

noaa k_p index
lasco
The arrival, around 07.45 UT on Nov 20, of the shock front of the powerful halo CME triggered a severe geomagnetic storm. In ACE and SOHO/CELIAS data, the signature of this arrival was clearly visible. The solar wind speed jumped suddenly from 430 to 750 km/s. The horizontal component of the interplanetary magnetic field was even measured to be -60nT. NOAA reported estimated K_p indices of 9 as seen on the figure above. Other ground based stations like Izmiran measured extreme disturbances of the geomagnetic field (K indices of 9).
ewan kane

left: Long Calderwood, Scotland, taken by Ewan Kane


right: Belfast, Northen Ireland, taken by Alan Fitzsimmons

aurora alan fitzsimmons