[HCDX] Extremely fast CME arrived at 0600 on Jan.18

["Jan Alvestad" <jan@xxxxxxxxxx>]

The extremely fast halo CME observed after the X3.8 event on January 17
reached Earth near 0600 UT on January 18, a transit time of approximately 21
hours. There was no shock wave, or at least no observable shock as most of
the normally available data could not be used due to sensor contamination by
the strong proton storm. The arrival of the CME can be deduced from whatever
SOHO, WIND and ACE data that was still usable. Thermal velocity (SOHO MTOF)
reached extreme levels after the arrival of this CME. Solar wind velocity
(SOHO and WIND) measurements were unreliable but did indicate that something
unusual was in progress. ACE IMF total field measurements recorded a sudden
increase at 05:33 UT and by 06:20 UT the IMF reached its strongest negative
(southwards) point.

With the proton storm gradually subsiding, "normality" was restored to solar
wind observations late on January 18. At this time both SOHO and ACE
recorded wind speed near 1000 km/sec, very impressive considering that the
CME had arrived many hours before.

Mediumwave propagation has improved considerably over the last 24 hours.
WDHP on 1620 kHz had a nice signal at 02 UT while there was no trace of this
station yesterday.

Jan Alvestad (author Solar Terrestrial Activity Report -
http://www.dxlc.com/solar/ )
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