Solar Terrestrial Activity Report

Last major update issued on July 22, 2006 at 05:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update July 19, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 19, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 19, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update July 9, 2006)]

Recent activity

The geomagnetic field was inactive to very quiet on July 21. Solar wind speed ranged between 270 and 281 km/s (all day average 273 km/s - decreasing 10 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 72.6. The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.3).
Three hour interval K indices: 10001011 (planetary), 10000003 (Boulder).

The background x-ray flux is at the class A5 level.

At midnight the visible solar disk was spotless. The solar flare activity level was very low. No C class events were recorded during the day. An active region at the east limb should soon rotate into view. This region could produce C flares.

Coronal mass ejections (CMEs)

July 19 and 21: No partly or fully Earth directed CMEs were detected in LASCO imagery.
July 20: A partial halo CME was observed after noon as a result of the eruption of a large filament in the southeast quadrant.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent trans equatorial coronal hole (CH232) was in an Earth facing location on July 21-22. This coronal hole has decayed substantially over the past two solar rotations and is currently poorly defined.

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


The geomagnetic field is expected to be quiet on July 22. The CME observed on July 20 could reach Earth during the latter half of July 23 or on July 24and cause unsettled to active conditions. A low speed stream from CH232 could influence the geomasgnetic field on July 24-26 resulting in some unsettled intervals.

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) Effects from a CME are likely to be observed at 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.


Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair to good. The MW band was monitored after 01h UTC. An intense thunderstorm over France prevented listening to the weaker signals and the antenna pointed to the southwest. After LSR strong signals were noted from a number of stations in the Buenos Aires area. 720, 850, 950, 1190, 1270 and 1450 were all unusually clear. Some stations from Brazil had good signals as well, most of those stations are located in or near São Paulo. Signals from North America were weaker compared to the previous day, probably because of the more southward interplanetary magnetic field. Lots of carriers were noted on the NW EWE.

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.

Active region Date numbered SEC
Location at midnight Area Classification Comment
10900 2006.07.14 2   S06W52 0010 BXO spotless
Total spot count: 2 0  
SSN: 12 0  

Monthly solar cycle data

Month Average solar
flux at Earth
International sunspot number Smoothed sunspot number
2000.04 184.2 125.5 120.8
cycle 23 sunspot max.
2000.07 202.3 170.1 119.8
2001.12 235.1 132.2 114.6 (-0.9)
2005.05 99.3 42.7 28.9 (-2.7)
2005.06 93.7 39.3 28.8 (-0.1)
2005.07 96.4 40.1 29.1 (+0.3)
2005.08 90.5 36.4 27.4 (-1.7)
2005.09 91.1 21.9 25.8 (-1.6)
2005.10 77.0 8.5 25.5 (-0.3)
2005.11 86.3 18.0 24.9 (-0.6)
2005.12 90.7 41.2 23.0 (-1.9)
2006.01 83.4 15.4 (20.7 predicted, -2.3)
2006.02 76.5 4.7 (18.2 predicted, -2.5)
2006.03 75.4 10.8 (16.4 predicted, -1.8)
2006.04 89.0 30.2 (15.7 predicted, -0.7)
2006.05 80.9 22.2 (14.9 predicted, -0.8)
2006.06 76.5 13.9 (12.7 predicted, -2.2)
2006.07 76.3 (1) 16.7 (2) (11.3 predicted, -1.4)

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.

[DX-Listeners' Club]