Solar Terrestrial Activity Report

Last major update issued on July 29, 2005 at 05:30 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, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update July 19, 2005)]

Recent activity

The geomagnetic field was unsettled to minor storm on July 28. Solar wind speed ranged between 378 and 640 (all day average 529) km/sec under the influence of a high speed stream from CH177.

Solar flux measured at 20h UTC on 2.8 GHz was 95.8. The planetary A index was 28 (STAR Ap - based on the mean of three hour interval ap indices: 27.5).
Three hour interval K indices: 35445334 (planetary), 35434324 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 1 C and 2 M class events was recorded during the day.

Region 10791 added several trailing spots and was quiet.
New region 10792 rotated into view at the northeast limb. This region is quite complex with at least one significant magnetic delta structure. A major proton flare is possible, the chance of an X class flare cannot be ignored. Flares: M1.0 long duration event peaking at 00:30, C2.8 at 06:37 and an M4.8 long duration event peaking at 22:08 UTC. The latter event was associated with a weak type II radio sweep.

Spotted regions not numbered by NOAA/SEC:
[S574] This region emerged in the northeast quadrant on July 28. Location at midnight: N15E23.

Coronal mass ejections (CMEs)

July 26-28: No obvious partly or fully Earth directed CMEs were observed. Several CMEs originating from region 10792 were observed while the region was behind the northeast limb.

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 trans equatorial coronal hole (CH177) was in an Earth facing position on July 25-27.

Processed SOHO/EIT 284 image at 01:06 UTC on July 29. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to minor storm on July 29 and quiet to unsettled on July 30-31.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
Coronal hole indicator CME indicator M and X class flare indicator

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.


Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation on long distance north-south paths is poor to very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela), both with unusually poor signals. CPN Radio (Perú) was noted just before local sunrise. Weak signals were heard on a few other frequencies with an unidentified station from Brazil on 1590 kHz having the strongest signal.

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
10791 2005.07.23 2 7 N14W20 0120 HSX classification was DAO at midnight
10792 2005.07.28 7 28 N12E78 0220 DSO beta-gamma-delta
classification was DKC at midnight, area 0600
S573 2005.07.23     N15W71     plage
S574 2005.07.28   5 N15E23 0040 DAO  
Total spot count: 9 40  
SSN: 29 70  

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)
2004.05 99.8 41.5 43.8 (-1.7)
2004.06 97.4 43.2 41.6 (-2.2)
2004.07 119.1 51.1 40.2 (-1.4)
2004.08 109.6 40.9 39.2 (-1.0)
2004.09 103.1 27.7 37.5 (-1.7)
2004.10 105.9 48.0 35.9 (-1.6)
2004.11 113.2 43.5 35.3 (-0.6)
2004.12 94.5 17.9 35.2 (-0.1)
2005.01 102.2 31.3 (34.6 predicted, -0.6)
2005.02 97.2 29.1 (33.3 predicted, -1.3)
2005.03 89.9 24.8 (31.6 predicted, -1.7)
2005.04 86.0 24.4 (29.7 predicted, -1.9)
2005.05 99.3 42.6 (27.2 predicted, -2.5)
2005.06 93.7 39.3 (25.7 predicted, -1.5)
2005.07 95.4 (1) 60.9 (2) (24.7 predicted, -1.0)

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]