Solar Terrestrial Activity Report

Last major update issued on May 24, 2004 at 03:20 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 May 18, 2004)]

Recent activity

The geomagnetic field was quiet to unsettled on May 23. Solar wind speed ranged between 443 and 505 km/sec under the influence of a high speed stream from coronal hole CH97.

Solar flux measured at 20h UTC on 2.8 GHz was 104.0. The planetary A index was 12 (STAR Ap - based on the mean of three hour interval ap indices: 12.4).
Three hour interval K indices: 33233233 (planetary), 33332433 (Boulder).

The background x-ray flux is at the class B2-B3 level.

At midnight there were 5 spotted regions on the visible disk. The solar flare activity level was low. A total of 4 C class events was recorded during the day.

Region 10613 decayed slowly and quietly.
Region 10615 decayed slowly and quietly.
Region 10618 developed quickly in the leading an trailing spot sections while slow decay was observed in the central section. The large penumbra in the center split into two and no longer has a magnetic delta structure. A new magnetic delta structure is forming quickly in the leading spot section and could cause M class flares. Flares: C2.9 at 14:52, C2.0 at 17:42, C1.6 at 18:01 and C1.4 at 19:54 UTC.
New region 10619 emerged in the southwest quadrant.
New region 10620 emerged in the southeast quadrant to the southeast of region 10618.

Coronal mass ejections (CMEs)

May 21-23: 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 recurrent, poorly defined coronal hole (CH97) in the northern hemisphere was in a geoeffective position on May 19-20.

Processed SOHO/EIT 284 image at 19:05 UTC on May 23. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on May 24-28.

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 good. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: none. At midnight UTC Rádio Papacasa (Brazil) was the best, however, there were at least two other stations from Brazil as well as Radio Cristal del Uruguay. The latter station had a poor signal but was the best between 00:30 and 02:30 UTC when finally Radio Vibración (Venezuela) began to dominate. On 1590.05 kHz an interesting station from Brazil was noted for a long time with mostly non stop (English) oldies. 1510 kHz had two stations from Brazil fighting for dominance, the poorest signal was from Rádio Planalto de Ibiapaba. The strongest station signed off at 01:02 UTC and only a few minutes later WWZN Boston surfaced and gradually got a fair signal. Several stations from Newfoundland (on 540, 590, 650, 740 and 930 kHz) were noted then as well, even WWBR New York on 1130 kHz was audible.

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.