Solar Terrestrial Activity Report

Last major update issued on April 1, 2004 at 03:40 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, 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 28, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on March 31. Solar wind speed ranged between 448 and 537 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 121.2. The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 8.5).
Three hour interval K indices: 12313232 (planetary), 22322332 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight there were 4 spotted regions on the visible disk. The solar flare activity level was low. A total of 9 C class events was recorded during the day.

Region 10581 was quiet and stable.
Region 10582 decayed with the main penumbra losing a significant amount of area and several spots disappearing. There is still some polarity intermixing and a minor M class flare is possible. Flares: C3.8 at 00:16, C2.3 at 00:42, C2.2 at 06:04, C3.7 at 09:35, very long duration C3.4 event peaking at 11:51, C2.1 at 14:02, C2.8 at 15:11, C1.1 at 19:20 and C7.4 at 20:08 UTC.
Region 10587 developed slowly in the leading spot section while slow decay was observed in the trailing spots.

Coronal mass ejections (CMEs)

March 29-31: No partly or fully earth directed CMEs observed in very limited LASCO data. A C2 long duration event in region 10581 late on March 30 may have been associated with an earth directed CME. A very long duration C3.4 event in region 10582 on March 31 may have been associated with an earth directed CME. There are no LASCO images available covering the hours after these events.

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

An elongated, recurrent trans equatorial coronal hole (CH88) will be in a geoeffective position on April 1-7. This coronal hole has extended westwards and will be influencing the geomagnetic field for at least a week.

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 April 1-3 and unsettled to minor storm on April 4-10 under the influence of a high speed stream from coronal hole CH88. If one of the long duration events noted above was associated with a geoeffective CME, conditions could become much worse on April 2 and 3.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation along long distance north-south paths is fair to good. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela). Good to excellent propagation towards Venezuela was noted with stations heard on 30-40 frequencies. Many had soccer commentaries celebrating one of the biggest upsets in South American soccer history as Venezuela downed Uruguay 3-0 in Uruguay].

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.