Solar Terrestrial Activity Report

Last major update issued on March 17, 2010 at 05:00 UTC.

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The geomagnetic field was quiet on March 16. Solar wind speed ranged between 332 and 372 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 83.2. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.0). Three hour interval K indices: 10101112 (planetary), 11202212 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight there was 1 spotted region on the visible solar disk.

Region 11054 decayed quickly and could lose its trailing spots today.

March 15-16: No obvious Earth directed CMEs were observed in LASCO or STEREO images.
March 14: A partial halo CME was observed in LASCO images early in the day after a C1.5 flare in region 11054 at 23:36 UTC on March 13. The CME was complex with mass ejected near region 11054, across the central meridian and into the northwest limb.

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 small coronal hole (CH396) in the southern hemisphere was in an Earth facing position on March 14-15.

Processed SOHO/EIT 195 image at 23:48 UTC on March 16. 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 poor. Propagation on long distance northeast-southwest paths is poor.

The geomagnetic field is expected to be quiet to occasionally unsettled on March 17-19 due to coronal hole effects. If the CME observed on March 14 arrives, active and minor storm intervals will be possible from late on March 17 and on March 18.

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.