Solar Terrestrial Activity Report

Last major update issued on August 17, 2004 at 03:30 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 16. Solar wind speed ranged between 290 and 356 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 133.6. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 9.5).
Three hour interval K indices: 21123323 (planetary), 11213322 (Boulder).

The background x-ray flux is at the class C1 level.

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 12 C and 2 M class events was recorded during the day.

Region 10656 decayed significantly losing quite a bit of penumbral area, particularly on the trailing spots. There is still a magnetic delta structure in the trailing spot section and further M class activity is likely until the region rotates out of view on August 18. Flares: C2.8 at 03:05, M1.1 at 03:47, C5.9/1F at 05:09, C9.4 at 05:38, C1.9 at 07:49, C1.7 at 08:35, C8.0 at 10:31, long duration C9.0 peaking at 13:38, C1.1 at 15:08, C1.9 at 17:51, C2.9 at 20:00, C6.2 at 20:55 and M1.1/1F at 22:44 UTC.
Region 10660 decayed further and could become spotless today.
Region 10661 developed slowly with several spots emerging. A weak magnetic delta structure formed at the southern edge of the largest penumbra. Further development will enable this region to produce M flares.

Coronal mass ejections (CMEs)

August 13-15: Several small CMEs were observed over the south pole, the southwest limb and the central west limb after flare activity in region 10656. While none of these CMEs had any obvious Earth directed components, there is a chance that some of the ejected material could reach Earth.
August 16: A full halo CME was observed beginning at 15:18 in LASCO C3 images. The source of this event was likely a few days behind the west limb.

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 19:06 UTC on August 16. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 17-19.

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 to fair. 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. Propagation favored stations from the Caribbean with the best signals from Harbour Light on 1400, WDHP on 1620, Caribbean Beacon on 1610 and the Puerto Rico stations on 1520 and 1600 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.