Solar Terrestrial Activity Report

Last major update issued on January 18, 2005 at 04:40 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 unsettled to severe storm on January 17. Solar wind speed ranged between 512 and 861 km/sec. ACE data indicated abnormal solar wind conditions at 07:17 UTC when solar wind speed increased abruptly from 530 to 610 km/sec. The total field of the interplanetary magnetic field became suddenly stronger as well. The source of this solar wind abnormality was probably the arrival of the halo CME observed after an M8 event in region 10720 on January 15. Another interesting change occurred at about 10:42 UTC when the IMF again had a sudden increase in its total field. The most likely source for this change was the arrival of the CME associated with an X2 flare in region 10720 late on January 15. With both CMEs arriving at a time when solar wind speed was already high, there were no true shocks (SOHO data did indicate a sudden increase in solar wind density at the time of the first abnormality, however, this increase was not present in ACE data. Based on data from both SOHO and ACE one could say this was a solar wind shock). Severe geomagnetic storming was observed after the second abnormality. 

Solar flux measured at 20h UTC on 2.8 GHz was 137.2. The planetary A index was 63 (STAR Ap - based on the mean of three hour interval ap indices: 62.8).
Three hour interval K indices: 54377753 (planetary), 44366653 (Boulder).

The background x-ray flux is at the class C1 level.

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was high. A total of 4 C. 2 M and 1 X class events was recorded during the day.

Spotted regions not numbered by NOAA/SEC:
S498: This region emerged in the southeast quadrant on January 16. Location at midnight: S11E05

Coronal mass ejections (CMEs)

January 16: 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. This CME will likely reach Earth late on January 18 and cause major to very severe geomagnetic storming.

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 likely rotate to a geoeffective position on January 19-20.

Processed SOHO/EIT 284 image at 20:17 UTC on January 17. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to severe or very severe storm on January 18-19 due to CME effects.

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 useless due to the the proton storm currently in progress. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: none. This was a lively frequency with at least 4 stations from Brazil noted. Additionally Radio Cristal del Uruguay and Radio Vibración (Venezuela) - with Union Radio Noticias programming - were noted at times. On other frequencies propagation was fairly good towards Brazil, particularly on frequencies above 1350 kHz.

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.