Solar Terrestrial Activity Report

Last major update issued on March 28, 2004 at 05:55 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 active on March 27. Solar wind speed ranged between 468 and 980 km/sec. A high speed stream from coronal hole CH87 was observed arriving at SOHO at 16:30 UTC. Within a few hours solar wind speed increased from from 600 to nearly 1000 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 127.6. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 15.3).
Three hour interval K indices: 31233434 (planetary), 32333435 (Boulder).

The background x-ray flux is at the class B5 level.

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

Region 10577 decayed slowly and quietly.
Region 10578 decayed and lost penumbra on the leading spots.
Region 10581 was quiet and stable.
Region 10582 decayed slightly as negative polarity spots at the southern edge of the largest (leading positive polarity) penumbra moved slowly away. An M class flare is still possible.
New region 10583 emerged in the northwest quadrant on March 25 and was noticed by SEC two days later. The region will soon rotate over the northwest limb.
New region 10584 emerged in the southeast quadrant on March 25 and was numbered by SEC two days later.
New region 10585 rotated into view at the southeast limb on March 25 and was recorded by SEC two days afterwards.
New region 10586 emerged quickly near the southwest limb early on March 27. The region is rotating over the limb. Flares: C1.3 at 09:49, C1.4 at 12:57, C1.9 at 14:32, C1.7 at 16:46 and C1.0 at 19:42 UTC.

Coronal mass ejections (CMEs)

March 25-27: 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 was in 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 unsettled to minor storm on March 28-29 and quiet to active on March 30-31 due to a high speed stream from coronal hole CH87.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along long distance north-south paths is poor to fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and CPN Radio (Perú)].

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.