Solar Terrestrial Activity Report

Last major update issued on July 28, 2004 at 04:00 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, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update July 1, 2004)]

Recent activity

The geomagnetic field was minor to extremely severe storm on July 27. Solar wind speed ranged between 729 and 1005 km/sec under the influence of a CME.

Solar flux measured at 20h UTC on 2.8 GHz was 118.1 (somewhat high due to a long duration M1 event). The planetary A index was 162 (STAR Ap - based on the mean of three hour interval ap indices: 164.0), making July 27 one of the stormiest days during solar cycle 23.
Three hour interval K indices: 87889755 (planetary), 77788645 (Boulder).

The background x-ray flux is at the class B3 level.

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 8 C and 2 M class events were recorded during the day.

Region 10652 decayed further, however, M class flares are still possible (and will be until the region has rotated behind the northwest limb). Flares: C1.5 at 03:02, M1.1/1N at 05:45, C1.2 at 06:29, long duration C3.7 peaking at 10:18, C3.0/1F at 15:07, C2.8 at 15:25, C1.8 at 18:57, long duration M1.5/1F peaking at 20:20, C2.9 at 22:33 and C1.1 at 22:57 UTC.
Region 10653 decayed significantly and could soon become spotless.
Region 10654 seems to have matured and is likely to decay unless new magnetic flux emerges.

Coronal mass ejections (CMEs)

July 26-27: No obvious Earth directed CMEs observed.

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

The northernmost extensions of a coronal hole (CH106) in the southern hemisphere were in a geoeffective position on July 25, however, no noticeable geomagnetic effects are likely due to the extreme CME related geomagnetic storm which began late on July 26.

Processed SOHO/EIT 284 image at 19:06 UTC on July 27. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be unsettled to active on July 28 and quiet to unsettled on July 29-31.

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 useless. Propagation along long distance north-south paths is good to very good. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant station tonight: A strong unidentified station from Brazil with a football commentary for a match in Ceará. Other unidentified stations from Brazil were noted as well. Half an hour before local sunrise Radio Cristal del Uruguay was observed with a weak signal. Lots of Brazilian stations could be heard on other frequencies (particularly on frequencies above 1350 kHz). No signs of any stations from North America.

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
10652 2004.07.16 25 37 N07W62 0930 FKC beta-gamma-delta
classification was EKC
at midnight, area 0500
10653 2004.07.17 3 1 S14W65 0070 DSO classification was HRX
at midnight, area 0020
10654 2004.07.25 8 10 N07E25 0130 DSO classification was DAO
at midnight, area 0090
Total spot count: 36 48
SSN: 66 78

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)
2003.06 129.3 77.4 65.0 (-2.6)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 60.1 (-1.7)
2003.09 112.2 48.7 59.6 (-0.5)
2003.10 151.7 65.5 58.2 (-1.4)
2003.11 140.8 67.3 56.8 (-1.4)
2003.12 114.9 46.5 54.8 (-2.0)
2004.01 114.1 37.7 (51.1 predicted, -3.7)
2004.02 107.0 45.8 (46.9 predicted, -4.2)
2004.03 112.0 49.1 (44.1 predicted, -2.8)
2004.04 101.2 39.3 (42.1 predicted, -2.0)
2004.05 99.8 41.5 (38.8 predicted, -3.3)
2004.06 97.4 43.2 (36.0 predicted, -2.8)
2004.07 123.0 (1) 79.5 (2) (34.2 predicted, -1.8)

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% less.

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]