Solar Terrestrial Activity Report

Last major update issued on August 11, 2005 at 04:50 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, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update August 3, 2005)]

Recent activity

The geomagnetic field was quiet to minor storm on August 10. Solar wind speed ranged between 418 and 492 (all day average 449) km/sec. An unexpected disturbance was observed beginning at ACE just after 06h UTC. This disturbance ended at approximately 15h UTC. The interplanetary magnetic field was moderately southwards 07-12h UTC and this caused minor geomagnetic storming.

Solar flux measured at 20h UTC on 2.8 GHz was 76.3. The planetary A index was 22 (STAR Ap - based on the mean of three hour interval ap indices: 22.5).
Three hour interval K indices: 32455322 (planetary), 31455422 (Boulder).

The background x-ray flux is at the class A5 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10794 decayed slowly and quietly.
Region 10795 decayed slowly and quietly.

Spotted regions not numbered by NOAA/SEC:
[S579] This region rotated into view at the southeast limb on August 10. Location at midnight: S14E65.

Coronal mass ejections (CMEs)

August 8-10: No obvious partly or fully 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

A trans equatorial coronal (CH180) was in an Earth facing position on August 8-9. Recurrent trans equatorial coronal hole (CH181) will likely rotate to an Earth facing position on August 13-15.

Processed SOHO/EIT 284 image at 01:06 UTC on August 11. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on August 11-12 due to effects from CH180. Quiet conditions are likely 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 very poor. Propagation on long distance northeast-southwest paths is good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and LT28 Rafaela Argentina. Many stations from Argentina and Uruguay were heard throughout the MW band with good signals from stations like Radio del Plata (Argentina) on 1030 and Radio Belgrano (Argentina) on 1510 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% lower.

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.