Solar Terrestrial Activity Report

Last major update issued on August 24, 2005 at 04:40 UTC. Last minor update posted at 10:35 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 23. Solar wind speed ranged between 419 and 557 (all day average 466) km/sec. The high speed stream associated with CH183 was observed beginning at ACE at about 19:30 UTC and has caused a minor increase in disturbance levels early on August 24.

Solar flux measured at 23h UTC on 2.8 GHz was 106.9 (the reading at 20h UTC was too high because of an M class long duration event). The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.0).
Three hour interval K indices: 32222322 (planetary), 33223322 (Boulder).

The background x-ray flux is at the class B7 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 6 C and 1 M class events was recorded during the day. A region with a large loop system located behind the northeast limb was the source of 2 long duration C class events during the first half of the day (including a C1.6 event peaking at 06:53 UTC), then a C3.4 flare at 22:05 and a C1.2 flare at 23:15 UTC. M flares are possible from this region.

Region 10800 developed slowly. There is some polarity intermixing at the center of the region. C flares are possible.  Flare: C1.9 at 20:31 UTC

Spotted regions not numbered or wrongly numbered by NOAA/SEC:
[S583] This is a complex, compact reversed polarity region about to rotate over the southwest limb. Almost all spots are within a single large penumbra. This penumbra has a strong magnetic delta structure with the positive polarity area in the northwest spearheading the negative polarity area. Further M or even X class proton flares are possible. Location at midnight: S10W76. Flares: C2.2 at 12:18 and M2.7 long duration event peaking at 14:44 UTC
[S586] This region emerged in the southeast quadrant on August 23. Location at midnight: S12E26.

Comment added at 06:00 UTC on August 24: The CME associated with the M2 LDE on August 22 was observed at ACE at 05:40 UTC. The solar wind shock appears to be moderately strong, minor to major geomagnetic storming is possible.

Comment added at 10:35 UTC: The current disturbance has intensified with very severe (Kp=8) to extremely severe (Kp=9) geomagnetic storming observed. The planetary A index for the 07-10h UTC interval was 207. Between 08:40 and 10h UTC the interplanetary magnetic field was extremely strongly southwards peaking at levels only observed during the most intense solar storms. Otherwise the region at the northeast limb is beginning to rotate into view.

Coronal mass ejections (CMEs)

August 21: No obvious partly or fully Earth directed CMEs were observed.
August 22: A complex CME event was observed after the M2.6 LDE early in the day. While most of the CME was observed over the southwest limb, contributions from disappearing filaments to the east of flare source made this a full halo CME. It's actually hard to tell if this CME should be separated into 2 or 3 different CMEs, all occurring within a short time period. A large CME was observed over the southwest limb following the major LDE event during the afternoon. Extensions over the eastern hemisphere were much weaker, however, it is still likely that Earth will receive some effects even from this CME.
August 23: At least a partial halo CME was observed after the M2 LDE in region S583 during the afternoon.

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 recurrent coronal hole (CH183) in the southern hemisphere was in an Earth facing position on August 21-22. CH183 doubled its size after the M2 LDE early on August 22.

Processed SOHO/EIT 284 image at 01:06 UTC on August 24. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to major storm on August 24-25 due to effects from CH183 and two CMEs. Quiet to active is likely on August 26.

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 fair. Propagation on long distance northeast-southwest paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela) and WWNN Boca Raton FL. A number of stations from the easternmost parts of the USA and Canada were noted throughout the MW band, in particular some of the New York stations had strong signals. At LSR many stations from Venezuela and Colombia were audible as well. Some stations from Argentina could be heard 10-30 minutes 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.