Solar Terrestrial Activity Report

Last major update issued on March 26, 2004 at 04:55 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, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update March 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update March 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update March 11, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on March 25. Solar wind speed ranged between 335 and 459 km/sec. A weak coronal hole flow (probably from coronal hole CH85) arrived after noon with some magnetometers recording active conditions a few hours later.

Solar flux measured at 20h UTC on 2.8 GHz was 127.0. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.4).
Three hour interval K indices: 11123322 (planetary), 11112332 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight there were 8 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 5 C and 1 M class events was recorded during the day.

Region 10574 decayed significantly and was quiet.
Region 10577 decayed slightly with the positive polarity area in the north located further east compared to the largest spot one day ago. Flare: C3.7 at 12:12 UTC.
Region 10578 developed slightly in the trailing spot section while slow decay was observed elsewhere.
Region 10581 was quiet and stable.
New region 10582 rotated fully into view at the northeast limb. The region is fairly complex with a magnetic delta structure in the main penumbra. M class flares are possible. Flares: C1.1 at 00:27, C3.2 at 04:23, M2.3 at 04:39, C6.1 at 07:21 and C1.8 at 15:08 UTC.

Spotted regions not numbered by NOAA/SEC:
[S377] This region emerged in the northwest quadrant on March 25. Location at midnight: N08W41.
[S378] A new region emerged in the southeast quadrant on March 25. Location at midnight: S13E47.
[S379] This region rotated into view at the southeast limb on March 25. Location at midnight: S16E76.

Coronal mass ejections (CMEs)

March 23-25: No partly or fully earth directed CMEs observed in limited LASCO data.

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 coronal hole (CH87) in the northern hemisphere will likely rotate into a geoeffective position on March 25-27.

Processed SOHO/EIT 284 image at 00:12 UTC on March 18. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on March 26 and most of March 27. A high speed stream from coronal hole CH87 could arrive on March 27 or 28 and cause unsettled to minor storm conditions until March 30.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is fair to good. Propagation along long distance north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and WLAM Lewiston ME. At times many stations from the easternmost parts of North America were heard on other frequencies throughout the MW band, WTIC Hartford CT on 1080 kHz was heard above the Spanish stations on that frequency, WSAR Fall River MA was noted on 1480 kHz and so on].

Coronal holes (1)	Coronal mass ejections (2)	M and X class flares (3)

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) Material from a CME is likely to impact 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/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% less.

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.