Solar Terrestrial Activity Report

Last major update issued on August 22, 2004 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, 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 unsettled to active on August 21. Solar wind speed ranged between 376 and 546 km/sec, partly under the influence of a low speed coronal hole flow. A marked increase in solar wind speed was observed between 01 and 02h UTC from 390 to 530 km/sec. While this was not a solar wind shock, this may have been the arrival of an additional disturbance, possibly a CME associated with the X1 event near the southwest limb on August 18.

Solar flux measured at 20h UTC on 2.8 GHz was 120.0. The planetary A index was 17 (STAR Ap - based on the mean of three hour interval ap indices: 18.3).
Three hour interval K indices: 34433333 (planetary), 44543323 (Boulder).

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

At midnight there were 5 spotted regions on the visible disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10661 decayed slowly and lost most of the small spots.
Region 10662 decayed and lost about half of its penumbral area.
Region 10663 was mostly unchanged and quiet.
Region 10664 developed slowly and quietly.

Spotted regions not numbered by NOAA/SEC:
[S447] A new region emerged in the northeast quadrant on August 20 and added a single small spot on August 21. Location at midnight: N05W01

Coronal mass ejections (CMEs)

August 19-21: 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 was likely in a geoeffective position on August 21.

Processed SOHO/EIT 284 image at 01:06 UTC on August 22. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on August 22-23. A weak coronal hole flow from coronal hole CH110 could reach Earth on August 24 and cause unsettled to active conditions that day and on August 25.

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 fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela). Only 3 stations from North America were heard: WWZN 1510, Radio Disney 1650 and WWRU 1660. Just before and at local sunrise propagation was best towards Argentina and Brazil (Rádio Sociedade on 740 kHz had an amazing signal), then after local sunrise (04:14 UTC) conditions suddenly improved towards Venezuela (many frequencies) and Puerto Rico (1430 and 1480 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.