Solar Terrestrial Activity Report

Last major update issued on February 11, 2010 at 05:20 UTC.

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The geomagnetic field was quiet on February 10. Solar wind speed ranged between 280 and 326 km/s. An increase in solar wind speed, density and total field was observed at ACE just before midnight. The disturbance may be related to recent CME activity.

Solar flux measured at 20h UTC on 2.8 GHz was 91.3. 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: 11111111 (planetary), 11120111 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 2 spotted regions on the visible solar disk.

Region 11045 decayed slowly and could still produce occasional C flares. Flares: C1.5 at 00:26, C1.2 at 15:06 and C3.7 at 15:14 UTC.
Region 11046 developed slowly and was quiet.

February 7: A full halo CME was observed following an M6 flare in region 11045.
February 8: A small CME was observed after an M4 flare in region 11045.
February 9-10: No obvious Earth directed CMEs were observed in LASCO images.

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 coronal hole (CH392) in the northern hemisphere will likely rotate into an Earth facing position on February 11-12.

Processed SOHO/EIT 195 image at 15:24 UTC on February 10. 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 good. Propagation on long distance northeast-southwest paths is poor.

The geomagnetic field is expected to be quiet to unsettled on February 11-12 due to CME and coronal hole effects and quiet on February 13-14. A few unsettled intervals are possible on February 15 due to effects from CH392.

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 ap indices.

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.