Solar Terrestrial Activity Report

Last major update issued on August 13, 2004 at 04:45 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 12. Solar wind speed ranged between 466 and 553 km/sec under the weakening influence of a high speed stream from coronal hole CH109.

Solar flux measured at 20h UTC on 2.8 GHz was 147.2. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 10.8).
Three hour interval K indices: 32223323 (planetary), 33213323 (Boulder).

The background x-ray flux is at the class B8 level.

At midnight there were 5 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 12 C and 1 M class events was recorded during the day.

Region 10656 added penumbra in the southeast and northwest, some decay was observed just south of the main central penumbra. The region has small magnetic delta structures and could produce M class flares. While the region's size is impressive, it is currently not very complex magnetically. Flares: C1.2 at 01:18, M1.2/1F at 05:05, C2.2 at 06:29, C1.8 at 09:11, C4.0 at 09:35, C4.9 at 11:43, C2.1 at 13:01, C1.4 at 15:47, long duration C6.5 peaking at 16:23, C4.4 at 18:57, C6.1 at 22:27, C9.9 at 22:58 and C1.2 at 23:46 UTC.
Region 10657 was quiet and stable.
Region 10659 decayed slowly and quietly.
Region 10660 developed slowly and quietly.
New region 10661 rotated partly into view at the northeast limb. This is the return of old region 10652. The region is currently neither complex nor displaying much activity.

Coronal mass ejections (CMEs)

August 10-12: No obviously Earth directed CMEs were detected in LASCO images.

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

No obvious coronal holes are currently approaching geoeffective positions.

Processed SOHO/EIT 284 image at 13:05 UTC on August 12. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 13-15.

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 ranged from poor to very good. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: none, several stations were heard including CPN Radio (Perú), Radio Cristal del Uruguay and Radio Vibración (Venezuela). On other frequencies conditions were rather poor at midnight, then before local sunrise Puerto Rico was noted on 1600 and 1480 and 1430 kHz, several stations from Venezuela could be heard as well, particularly above 1350 kHz. Then just after local sunrise propagation swung quickly and strongly southwards with Radio San Carlos (Uruguay) having the best signal I've heard them with. Radio San Nicolas (Argentina) on 1430 kHz was strong too and there were several other interesting signals around (i.e Radio Ñandutí (Paraguay on 1020.1 kHz).

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.