Solar Terrestrial Activity Report

Last major update issued on July 24, 2005 at 02:50 UTC. The next update will be on July 29.

[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 quiet on July 23. Solar wind speed ranged between 412 and 575 (all day average 493) km/sec, generally decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 80.1. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 5.4).
Three hour interval K indices: 21111121 (planetary), 31111111 (Boulder).

The background x-ray flux is at the class A4 level.

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

New region 10791 emerged on July 22 in the northeast quadrant and was numbered the next day by SEC. The region developed moderately quickly on July 23. C flares are possible.

Spotted regions not numbered by NOAA/SEC:
[S573] This region emerged in the northwest quadrant on July 23. Location at midnight: N15W06

Coronal mass ejections (CMEs)

July 21: A fast and impressive symmetrical  full halo CME was observed in LASCO C3 images beginning at 04:18 UTC. Its source was on the backside of the Sun, perhaps 6 days behind the northeast limb.
July 22: No obvious partly or fully Earth directed CMEs were observed.
July 23: A symmetric full halo CME was observed in LASCO C3 images beginning at 01:42 UTC. Its source was backsided. Several CMEs were observed later in the day from a source just 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 coronal hole (CH176) in the southern hemisphere with a narrow trans equatorial extension was in an Earth facing position on July 22. A recurrent trans equatorial coronal hole (CH177) will likely rotate to an Earth facing location on July 26.

Processed SOHO/EIT 284 image at 01:06 UTC on July 24. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet on July 24, quiet to unsettled or active on July 25 due to effects from CH176, and quiet to unsettled on July 26-28. Unsettled to active is possible on July 29 when a high speed stream from CH177 arrives.

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 poor to very poor. Propagation on long distance north-south paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay, two unidentified stations from Brazil were noted as well before 01h UTC. On other frequencies some stations from Argentina and Uruguay were audible at fair signal levels, 1070 Radio El Mundo had the best 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 10 8 N13E50 0090 DAI formerly region S572
location was N14E48 at midnight
S571 2005.07.22   S16W46     plage
S573 2005.07.23   4 N15W06 0010 BXO  
Total spot count: 10 12  
SSN: 20 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)
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 97.1 (1) 57.1 (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]