Solar Terrestrial Activity Report

Last major update issued on January 19, 2005 at 03:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update January 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update January 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update January 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update November 8, 2004)]
[Archived reports (last update January 12, 2005)]

Recent activity

The geomagnetic field was active to severe storm on January 18. Solar wind speed ranged between 443 and 993 km/sec (values are unreliable due to proton storm). 

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.

Solar flux measured at 20h UTC on 2.8 GHz was 124.3. The planetary A index was 72 (STAR Ap - based on the mean of three hour interval ap indices: 72.4).
Three hour interval K indices: 65756645 (planetary), 55646644 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight there were 5 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 12 C and 2 M class events was recorded during the day.

Spotted regions not numbered by NOAA/SEC:
S500: This region rotated into view at the northeast limb on January 18. Location at midnight: N10E70.

Coronal mass ejections (CMEs)

January 18: No obvious fully or partly Earth directed CMEs were observed.
January 17: A large and fast full halo CME was observed after the X3 event in region 10720 during the UTC morning.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report with the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A fairly large recurrent coronal hole (CH140) in the northern hemisphere will rotate to a geoeffective position on January 18-20.

Processed SOHO/EIT 284 image at 21:36 UTC on January 18. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to major storm on January 19 due to CME effects and quiet to active on January 20. A high speed stream from coronal hole CH140 will likely reach Earth late on January 21 and cause unsettled to minor storm conditions until January 23.

Coronal holes (1)	Coronal mass ejections (2)	M and X class flares (3)

1) Effects from a coronal hole could reach Earth within the next 5 days. When the high speed stream has arrived the color changes to green.
2) Material from a CME is likely to impact Earth within 96 hours.
3) There is a possibility of either M or X class flares within the next 48 hours.

Green: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. On other frequencies only a few stations were noted: 740 Rádio Sociedade (Brazil), 930 Rádio Metropolitana (Brazil), 1510 WWZN Boston, 1620 WDHP and 1660 WGIT.

Active solar regions (Recent map)

Compare to the previous day's image.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SEC. Comments are my own, as is the STAR spot count (spots observed at or inside a few hours before midnight) and data for regions not numbered by SEC or where SEC has observed no spots. SEC active region numbers in the table below and in the active region map above are the historic SEC/USAF numbers.

Monthly solar cycle data

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2) Unofficial, accumulated value based on the Boulder (NOAA/SEC) sunspot number. The official international sunspot number is typically 30-50% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and analysis, and partly on data from some of these solar data sources. All time references are to the UTC day. Comments and suggestions are always welcome.