Solar Terrestrial Activity Report

Last major update issued on May 3, 2004 at 03:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 3, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 3, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update May 3, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update April 30, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on May 2. Solar wind speed ranged between 314 and 446 km/sec. The total field of the interplanetary magnetic field was stronger than average, however, the IMF was generally northwards all day causing the geomagnetic field to remain mostly quiet.

Solar flux measured at 20h UTC on 2.8 GHz was 97.5. The planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 7.6).
Three hour interval K indices: 31022222 (planetary), 22122222 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was low. A total of 10 C class events was recorded during the day.

Region 10601 decayed in the trailing spot section while development was observed in the intermediate spot section with numerous new spots emerging. There is still a possibility of a minor M class flare. Flares: C5.4 at 03:51, C1.3 at 05:34, C1.4 at 08:36, C1.1 at 10:11, C8.3 at 11:19, C1.4 at 15:18, C2.1 at 15:36, C2.6 at 16:01, C1.0 at 16:45 and C1.1 at 17:19 UTC.
Region 10603 decayed slowly and quietly.

Spotted regions not numbered by NOAA/SEC:
[S397] This region emerged on May 2 near the southeast limb. Location at midnight: S19E63.

Coronal mass ejections (CMEs)

April 30 - May 2: No fully or partly Earth directed CME 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 small recurrent coronal hole (CH93) in the northern hemisphere may have been in a geoeffective position on April 29 and early on April 30. A large trans equatorial coronal hole (CH94) - the recurrent eastern part of what was CH88 during the previous rotation - will be in a geoeffective position on April 30 - May 4.

Processed SOHO/EIT 284 image at 01:05 UTC on May 3. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to active on May 3-7 due to a high speed stream from coronal hole CH94. Occasional minor storm intervals are possible on May 6-7.

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.

Propagation

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 poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay at first, then Radio Vibración (Venezuela), with CPN Radio (Perú) having the best signal after 03h UTC. Only a few stations from North America could be heard, the usual Newfoundland stations had the best signals].

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.