Solar Terrestrial Activity Report

Last major update issued on July 23, 2005 at 05:20 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 quiet to unsettled on July 22. Solar wind speed ranged between 563 and 670 (all day average 581) km/sec under the influence of a high speed stream from CH175.

Solar flux measured at 20h UTC on 2.8 GHz was 73.6. The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 12.9).
Three hour interval K indices: 33223333 (planetary), 33222333 (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.

Spotted regions not numbered by NOAA/SEC:
[S571] This region emerged in the southwest quadrant on July 22. Location at midnight: S16W33.
[S572] A new region emerged in the northeast quadrant on July 22. The region has poor separation of the positive and negative polarity areas and C flares are possible. Location at midnight: N15E62.

Coronal mass ejections (CMEs)

July 20 and 22: No obvious partly or fully Earth directed CMEs were observed.
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 23: A symmetric full halo CME was observed in LASCO C3 images beginning at 01:42 UTC. Its source was backsided.

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 25-26.

Processed SOHO/EIT 284 image at 01:06 UTC on July 23. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on July 23-25, possibly with isolated active intervals on July 25 due to effects from CH176.

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 fair to good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: none, Radio Cristal del Uruguay, Rafaela Argentina, CPN Radio (Perú) and Radio Vibración (Venezuela) were all heard with fair to good signals at times. As usual propagation was best after local sunrise with stations from the province of Buenos Aires having the best signals from 590 Radio Continental, 710 Radio Diez, 790 Radio Mitre and others. The strongest signal of all trans Atlantic stations was that of Rádio Cristal (Brazil) on 1350 kHz, the signal peaked just above S9+10dB. From the Caribbean WMDD on 1480, WDHP on 1620 and WGIT on 1660 kHz all had fair signals.

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
S569 2005.07.12     N06W63     plage
S571 2005.07.22   3 S16W33 0020 DRO  
S572 2005.07.22   5 N15E62 0030 CAO  
Total spot count: 0 8  
SSN: 0 28  

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 97.9 (1) 56.5 (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]