Solar Terrestrial Activity Report

Last major update issued on March 10, 2006 at 03:45 UTC. The next update will likely be on March 13.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update March 2, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update March 2, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update March 2, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update March 2, 2006)]

Recent activity

The geomagnetic field was inactive to unsettled on March 9. Solar wind speed ranged between 337 and 396 (all day average 370) km/sec under the increasing influence of a low to moderately high speed stream from CH215.

Solar flux measured at 20h UTC on 2.8 GHz was 72.9. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 4.5).
Three hour interval K indices: 01000232 (planetary), 01011120 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight the visible solar disk was spotless. The solar flare activity level was very low. No C class events were recorded during the day.

Coronal mass ejections (CMEs)

March 7-9: No recent LASCO images available. The filament eruption in region 10856 on March 7 may have been associated with a small CME with potentially Earth directed extensions.

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 recurrent trans equatorial coronal hole (CH215) appears to have become larger over the last solar rotation and was in an Earth facing position on March 5-7.

Processed SOHO/EIT 284 image at 01:20 UTC on February 28. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on March 10-11 due to effects from CH215 and quiet on March 12-13.

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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight:  WLAM Lewiston ME. Propagation was best to the US east coast and Cuba. Although there weren't any impressive signals around, stations like 610 WIOD Miami FL and 1480 WSAR Fall River MA were audible at weak to fair signal levels.

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% lower.

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.