Solar Terrestrial Activity Report

Last major update issued on July 26, 2004 at 05:55 UTC. Missing images and text data covering July 6-25 will be added when time allows.

[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 major to very severe storm on July 25. Solar wind speed ranged between 524 and 848 km/sec under the influence of effects from at least 2 CMEs.

Solar flux measured at 20h UTC on 2.8 GHz was 156.2 (somewhat high due to a long duration event earlier in the day). The planetary A index was 122 (STAR Ap - based on the mean of three hour interval ap indices: 124.9).
Three hour interval K indices: 67786767 (planetary), 56676766 (Boulder).

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

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was high. A total of 5 C and 4 M class events were recorded during the day.

Region 10652 decayed and lost about a third of its penumbral area. The region is still capable of producing major flares. Flares: C7.4 at 00:32, major impulsive M7.1/2B at 05:51, M1.0/1F at 06:39, C6.9 at 07:14, C2.1 at 13:25, M2.2 at 13:49, C2.5 at 19:45, C1.0 at 23:42 UTC.
Region 10653 decayed slowly. Flare: long duration M1.1 peaking at 15:14 UTC. The most intense part of this large area event was observed between this region and region 10652 in GOES SXI images. 
Region 10654 developed and could produce C flares.

Coronal mass ejections (CMEs)

July 25: A large full halo CME was observed after the long duration M1 proton event between regions 10652 and 10653 after noon. This CME will likely reach Earth on July 27 and cause minor to very severe geomagnetic storming. There may have been a CME associated with the major flare earlier in the day in region 10652, however, no LASCO images for the period are currently available.

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 in the southern hemisphere could cause a disturbance on July 27-28.

Processed SOHO/EIT 284 image at 01:06 UTC on July 26. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to minor storm on July 26, minor to very severe storm on July 27 and unsettled to major storm on July 28.

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 poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with a weak signal. Another station, probably from Argentina, was noted at times. On other frequencies I heard several stations from the São Paulo area in Brazil. Uruguay stations noted on 970, 1130, 1420 and 1480 kHz. 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.