Solar Terrestrial Activity Report

Last major update issued on July 18, 2005 at 04:15 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 2, 2005)]

Recent activity

The geomagnetic field was quiet to minor storm on July 17. Solar wind speed ranged between 387 and 561 (all day average 463) km/sec. The CME related disturbance which began early in the day, was associated with two episodes of a sustained (moderate) southerly swing of the interplanetary magnetic field, the first from 07:30 until 10h UTC, the second after 21h UTC. These episodes caused minor storm conditions.

Solar flux measured at 20h UTC on 2.8 GHz was 74.1. The planetary A index was 22 (STAR Ap - based on the mean of three hour interval ap indices: 21.5).
Three hour interval K indices: 32353335 (planetary), 32343325 (Boulder).

The background x-ray flux is at the class A7 level.

At midnight the visible solar disk was spotless. The solar flare activity level was low. A total of 1 C class event was recorded during the day, a C4.3 flare in region 10790 at the southwest limb.

Coronal mass ejections (CMEs)

July 15-16: No obvious partly or fully Earth directed CMEs were observed.
July 17: An impressive full halo CME was observed in LASCO C3 images starting at 12:18 UTC. Its source was in region 10786 well behind the northwest limb. A minor increase in proton levels was observed as well after this event.

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 well defined recurrent trans equatorial coronal hole (CH175) will rotate into an Earth facing position on July 17-19.

Processed SOHO/EIT 284 image at 01:06 UTC on July 18. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to minor storm on July 18 due to CME effects. Quiet to unsettled is likely on July 19. Late on July 19 or early on July 20 a high speed stream from CH175 is likely to arrive and could cause unsettled to minor storm conditions until July 22.

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 along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela). An unidentified station from Brazil had a weak and steady signal on 1480 kHz, otherwise there weren't any unusual signals around.

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
10789 2005.07.03     N17W85     plage
10790 2005.07.13 2   S10W93 0060 HAX spotless
S569 2005.07.12     N06W11     plage
Total spot count: 2 0  
SSN: 12 0  

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)
2005.07 105.4 (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]