Solar Terrestrial Activity Report

Last major update issued on August 20, 2004 at 04:30 UTC. Minor update posted at 11:40 UTC.

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

Recent activity

The geomagnetic field was quiet to unsettled on August 19. Solar wind speed ranged between 325 and 368 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 120.6. The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 7.8).
Three hour interval K indices: 31022322 (planetary), 21012222 (Boulder).

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

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 9 C and 2 M class events was recorded during the day.

Region 10656 behind the southwest limb continued to be active and produced several flares. Flares: C2.6 at 00:06, C4.7 at 01:19, C3.0 at 04:25, M3.0 at 07:01, C3.0 at 12:39, C4.2 at 13:07, M2.1 at 13:51, C2.1 at 21:02 UTC.
Region 10661 decayed slightly and was quiet.
Region 10662 developed slowly and quietly.
New region 10663 was first observed at the northeast limb late on August 18 and was numbered by SEC the next day. A trailing spot section in the northeastern part of the region rotated into view. Bright plage is observed at several locations in the region.

Comment added at 11:40 UTC on August 20, 2004: A coronal hole flow is currently disturbing the geomagnetic field. Solar wind parameters suggest that the disturbance will intensify and could reach the minor storm level within a few hours. Solar wind speeds associated with the coronal hole flow have so far been low.
A new region has emerged in the southeast quadrant with several spots. The plage in this region has been somewhat bright over the last few days and the current development is not unexpected. The current location is S11E47.

Coronal mass ejections (CMEs)

August 17: A full halo CME was observed in LASCO C3 images starting at 07:42 UTC. Most of the ejected material was observed over the southeast limb, faint extensions were noted at the west limbs. The source of this CME was a fairly large filament eruption to the south and southeast of region 10661. This eruption began around 04h UTC and peaked near 06h UTC.
August 18: A CME was observed after the X1 flare in the afternoon. Most of the ejected material was observed over the southwest limb, however, there were nearly simultaneous emissions over the east limb, and there is a slight chance that this was a (faint) full halo CME.
August 19: No obviously Earth directed CMEs were 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

The northernmost extension of a coronal hole (CH110) in the southern hemisphere will likely rotate to a geoeffective position on August 22.

Processed SOHO/EIT 284 image at 01:06 UTC on August 20. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet to unsettled on August 20-22. There is a chance of a weak CME reaching the Earth on August 20.

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 fair to occasionally good. Propagation along long distance north-south paths is fair to poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela). WLAM (with WMTW programming) was noted as well. On other frequencies quite a few stations from North America could be heard. CFNW (relaying CFCB) on 790 kHz had a surprisingly good signal, the best of all the Newfoundland stations. Several stations from Venezuela had fair to good signals as well.

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.