Solar Terrestrial Activity Report

Last major update issued on August 16, 2005 at 05:00 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 13, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on August 15. Solar wind speed ranged between 336 and 566 (all day average 417) km/sec. A high speed stream from CH181 began at ACE at 16:30 UTC. The associated disturbance has increased slowly in intensity early on August 16.

Solar flux measured at 20h UTC on 2.8 GHz was 75.8. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 7.6).
Three hour interval K indices: 11112323 (planetary), 12212213 (Boulder).

The background x-ray flux is at the class A3 level.

At midnight there were 2 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 10797 slowly losing some penumbral area both in the leading and trailing spot sections.
Region 10798 decayed slowly and quietly.

Coronal mass ejections (CMEs)

August 13-15: 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

Recurrent trans equatorial coronal hole (CH181) was in an Earth facing position on August 13-15.

Processed SOHO/EIT 284 image at 01:06 UTC on August 16. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on August 16-17 and quiet to active on August 18.

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 on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) before 03h UTC, then Radio Cristal del Uruguay. Many stations from the easternmost parts of the USA and Canada were audible before 03:30 UTC, then the current disturbance caused a swing to more southerly propagation conditions. Several stations from Argentina, Uruguay and Brazil had good signals after LSR.

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.