Solar Terrestrial Activity Report

Last major update issued on July 27, 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 July 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update July 1, 2004)]

Recent activity

The geomagnetic field was quiet to major storm on July 26. Solar wind speed ranged between 551 and 931 km/sec. A very strong solar wind shock was observed at SOHO at 22:28 UTC, solar wind speed increased suddenly from 580 to 930 km/sec. This was the arrival of the large CME associated with the long duration M1 proton event observed between regions 10652 and 10653 on July 26. The transit time for the CME was only 31 hours. Early on July 27 solar wind speed has been just above 1000 km/sec. The planetary A index for the 00-03h UTC interval was 184.

Solar flux measured at 20h UTC on 2.8 GHz was 128.0. The planetary A index was 31 (STAR Ap - based on the mean of three hour interval ap indices: 32.5).
Three hour interval K indices: 64333236 (planetary), 64332236 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 7 C and 3 M class events were recorded during the day.

Region 10652 decayed quickly losing penumbra and spots. There is still a chance of another major flare, however, the region has become significantly less complex over the last two days. Flares: C1.9 at 02:43, M1.3 at 05:52, C1.5 at 08:10, C2.9 at 09:05, C2.5 at 10:29, C4.7 at 16:59, M1.1/2N at 17:30, C1.0 at 22:07, C1.8 at 22:51, M1.2/1F at 00:00 UTC.
Region 10653 lost some penumbra around the main spot, however, a new penumbra emerged further south.
Region 10654 developed further and may produce C flares.

Coronal mass ejections (CMEs)

July 26: No obvious Earth directed CMEs 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 extensions of a coronal hole (CH106) in the southern hemisphere could cause a weak disturbance on July 28.

Processed SOHO/EIT 284 image at 01:06 UTC on July 27. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be minor to very severe storm on July 27, unsettled to major storm on July 28 and quiet to active on July 29-30.

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 useless. Propagation along long distance north-south paths is fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. On other frequencies a number of interesting stations from Brazil could be heard, i.e. an unidentified station on 1520 kHz with religious programming had a fair signal. No signs of any stations from North America.

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.