Solar Terrestrial Activity Report

Last major update issued on July 7, 2006 at 04:05 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update June 7, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 7, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 7, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update June 5, 2006)]

Recent activity

The geomagnetic field was quiet to active on July 6. Solar wind speed ranged between 540 and 695 km/s (all day average 567 km/s - decreasing 41 km/s from the previous day) under the declining influence of a high speed stream from CH230.

Solar flux measured at 20h UTC on 2.8 GHz was 85.0. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 10.8).
Three hour interval K indices: 43331122 (planetary), 42332212 (Boulder).

The background x-ray flux is at the class A8 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 1 M class event was recorded during the day.

Region 10898 had the central umbra fragmenting further with a new penumbra in the southern part splitting off from the main penumbra. C flares are possible and there is a small chance of another M class flare. Flare: M2.5/2F flare at 08:36 UTC. This event was associated with type II and IV radio sweeps and a minor proton enhancement.
Region 10899 was mostly unchanged and quiet.

Coronal mass ejections (CMEs)

July 4-5: No partly or fully Earth directed CMEs were detected in LASCO imagery.
July 6: A large full halo CME was observed after the M2 event in region 10898. While the core of this CME is not likely to reach Earth, some of the ejected material is heading our way and could reach Earth late on July 8 or sometine on July 9.

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 coronal hole (CH231) in the southern hemisphere will likely rotate into an Earth facing location on July 7-9.

Processed SOHO/EIT 284 image at 01:06 UTC on July 7. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be mostly quiet on July 7-8. CME effects are possible from late on July 8 until July 10 with unsettled to minor storm conditions likely. A high speed stream from CH231 will probable dominate the solar wind on July 10-12 and cause quiet to minor storm conditions.

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. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Cristal del Uruguay, Radio VibraciĆ³n and at least two other stations were all audible. There were a number of stations from Brazil (both stations on 1280 kHz, 2 on 1290 and 1300 kHz and 1 each on 1310 and 1320 kHz to mention a few), Uruguay (best signals from 930 Montecarlo and 1410 AM Libre) and Argentina on other frequencies, even a few stations from Chile and Venezuela could be heard.

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
10897 2006.06.25     N06W75     plage
10898 2006.06.28 8 6 S08W41 0420 CKI  
10899 2006.07.05 6 6 S05E56 0100 DSO  
Total spot count: 14 12  
SSN: 34 32  

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 86.0 (1) 6.8 (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]