Solar Terrestrial Activity Report

Last major update issued on March 21, 2006 at 04:40 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 to minor storm on March 20. Solar wind speed ranged between 576 and 734 (all day average 652) km/sec under the influence of a high speed stream from CH216. Wind speed decreased slowly and gradually after 15h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 76.9. The planetary A index was 22 (STAR Ap - based on the mean of three hour interval ap indices: 21.9).
Three hour interval K indices: 54442243 (planetary), 55542233 (Boulder).

The background x-ray flux is at the class A2 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 10862 added several small spots. The main area of interest is still in the western part of the largest trailing penumbra where it's difficult to visually separate the opposite polarity areas. C flares are possible.

Spotted regions not numbered by NOAA/SEC:
[S634] This region emerged on March 20 in the northwest quadrant due north of region 10862. Location at midnight: N07W27

Coronal mass ejections (CMEs)

March 18-20: 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 recurrent trans equatorial coronal hole (CH216) was in an Earth facing position on March 16-17. A coronal hole (CH217) in the northern hemisphere will likely rotate to an Earth facing position on March 21.

Processed SOHO/EIT 284 image at 01:06 UTC on March 21. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on March 21-23. Effects from CH217 could reach Earth on March 24 and cause a few unsettled to active intervals.

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 very poor. Propagation on long distance northeast-southwest paths is fair to poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración and CPN Radio (Perú). Several stations from Colombia and Venezuela were audible on other frequencies.

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.