Solar Terrestrial Activity Report

Last major update issued on March 25, 2006 at 05:05 UTC.

[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 quiet on March 24. Solar wind speed ranged between 350 and 402 (all day average 374) km/sec. A weak low speed stream from CH217 began to influence the geomagnetic field after noon.

Solar flux measured at 20h UTC on 2.8 GHz was 75.8. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.6).
Three hour interval K indices: 10001122 (planetary), 10012112 (Boulder).

The background x-ray flux is at the class A3 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10863 reemerged with spots and was the largest region on the visible disk late in the day.
New region 10864 emerged in the southwest quadrant on March 23 and was numbered by SEC the following day.

Coronal mass ejections (CMEs)

March 22-24: No partly or fully Earth directed CMEs were observed in LASCO imagery.

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 trans equatorial coronal hole (CH217) was in an Earth facing position on March 21-22.

Processed SOHO/EIT 284 image at 01:06 UTC on March 25. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on March 25-27 due to weak effects from CH217.

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 poor to very poor. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). Propagation was best to Venezuela, Colombia and Cuba.

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.