Solar Terrestrial Activity Report

Last update issued on May 3, 2003 at 03:10 UTC.

[Solar and geomagnetic data - last 4 weeks (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 1, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update May 1, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update May 1, 2003)]

Recent activity

The geomagnetic field was mostly quiet to unsettled on May 2 with a single minor storm interval 03-06h UTC. Solar wind speed ranged between 480 and 611 km/sec under the decreasing influence of a high speed stream from coronal hole CH37.

Solar flux measured at 17h UTC on 2.8 GHz was 143.0 (the measurement at 20h UTC was not used because of influence from a long duration event in region 10345). The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 17.4).
Three hour interval K indices: 35333223 (planetary), 36343312 (Boulder).

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

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

Region 10344 did not change much and remains capable of producing C class flares.
Region 10345 decayed slowly and lost penumbral area both in the northern and southern penumbrae. The region appears to have become a little less complex magnetically over the last day. Flares: M1.0 long duration event peaking at 03:08, C1.4 long duration event peaking at 12:48 and C5.4 long duration event peaking at 18:14 UTC.
Region 10346 was quiet and stable.
Region 10348 reemerged with several spots. Flare: C1.3 (impulsive) at 21:28 UTC.
Region 10349 decayed quickly in the trailing spot section losing nearly half of the penumbral area in that part. The leading spot section did not change much. The region still has a relatively simple layout with all magnetically negative spots in the west and all positive spots in the east. Flares: C1.1 at 01:05 and C2.0 long duration event peaking at 06:25 UTC. It should be noted that region 10344 produced an impulsive flare near the peak of the C2.0 LDE.
Region 10351 added a couple of small spots and was quiet.

Spotted regions not yet numbered by SEC/NOAA:
[S149] A new region emerged on May 2 in the southwest quadrant. Location at midnight: S09W44.
[S150] A new region emerged on May 2 in the southwest quadrant. Location at midnight: S01W30.

Coronal mass ejections (CMEs)

April 30-May 2: No obviously geoeffective CMEs observed.

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 (CH38) in the southern hemisphere will rotate into a geoeffective position on May 2-5.

Processed SOHO EIT 284 image at 19:06 UTC on May 2. Any black areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on May 3 and quiet to unsettled on May 4 and the first half of May 5. Then a high speed stream from coronal hole CH38 will begin dominating the solar wind and cause unsettled to minor storm conditions until May 9. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along north-south paths is fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay at first, then Cadena Peruana de Noticias.]

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.
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 SEC/NOAA. 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.

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 (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% less.

This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.