Solar Terrestrial Activity Report

Last major update issued on January 19, 2010 at 05:10 UTC. Minor update posted at 15:30 UTC

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update October 4, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update October 4, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update October 4, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update January 3, 2010)]

The geomagnetic field was very quiet on January 18. Solar wind speed ranged between 330 and 361 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 81.5. The planetary A index was 3 (STAR Ap - based on the mean of three hour interval ap indices: 3.3). Three hour interval K indices: 01001111 (planetary), 01110111 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight the visible solar disk was spotless.

A region behind the southeast limb has been quite active over the last days. The region was the source of a long duration C4.9 event peaking at 20:39 UTC. This event was associated with a CME.

Update added at 15:30 UTC: The region at the southeast limb has been quite active today and produced a C5.2 flare at 08:45, a C4.9 flare at 09:06 and an M2.3 flare at 13:41 UTC. Further M class flare activity is possible.

January 16-18: No partially or fully Earth directed CMEs were observed in LASCO or STEREO imagery.

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

A northern hemisphere coronal hole (CH389) with a weak equatorialward extension rotated across the central meridian on January 15-16.

Processed SOHO/EIT 195 image at 23:35 UTC on January 18. The darkest areas on the solar disk are likely coronal holes.

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is fair to good. Propagation on long distance northeast-southwest paths is poor.

The geomagnetic field is expected to be quiet with possible unsettled intervals on January 19 due to effects from CH389 and quiet on January 20-21.

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) Effects from a CME are likely to be observed at 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.

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/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

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/SWPC) sunspot number. The official international sunspot number is typically 30-50% lower.
3) Running average based on the daily SWPC ap indices. Values in red are based on official NGDC records.

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.