Solar Terrestrial Activity Report

Last major update issued on July 20, 2006 at 05:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update July 19, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 19, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 19, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update July 9, 2006)]

Recent activity

The geomagnetic field was inactive to very quiet on July 19. Solar wind speed ranged between 270 and 308 km/s (all day average 273 km/s - decreasing 46 km/s from the previous day).

Solar flux measured at 20h UTC on 2.8 GHz was 71.1. The planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 2.1).
Three hour interval K indices: 11000011 (planetary), 12000001 (Boulder).

The background x-ray flux is below the class A1 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10900 decayed quickly and could soon become spotless.

Coronal mass ejections (CMEs)

July 17-19: No partly or fully Earth directed CMEs were detected in LASCO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent trans equatorial coronal hole (CH232) will rotate into an Earth facing location on July 21. This coronal hole has decayed substantially over the past two solar rotations.

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

Forecast

The geomagnetic field is expected to be quiet on July 19-22.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)

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) Effects from a CME are likely to be observed at 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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is good. Lots of stations were heard throughout the MW band with the best reception from Brazil. 760 kHz usually only has Rádio Uirapuru, this morning another station from further south in Brazil was audible at almost the same signal level. Frequencies like 1280, 1290 and 1300 each had at least two stations from Brazil. Argentina was noted on several frequencies above 1600 kHz with 1610 Radio Guaviyú occasionally reaching very good signal levels.

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
spot
count
STAR
spot
count
Location at midnight Area Classification Comment
10900 2006.07.14 14 6 S04W25 0090 DSO classification was BXO at midnight, area 0010
Total spot count: 14 6  
SSN: 24 16  

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)
2005.05 99.3 42.7 28.9 (-2.7)
2005.06 93.7 39.3 28.8 (-0.1)
2005.07 96.4 40.1 29.1 (+0.3)
2005.08 90.5 36.4 27.4 (-1.7)
2005.09 91.1 21.9 25.8 (-1.6)
2005.10 77.0 8.5 25.5 (-0.3)
2005.11 86.3 18.0 24.9 (-0.6)
2005.12 90.7 41.2 23.0 (-1.9)
2006.01 83.4 15.4 (20.7 predicted, -2.3)
2006.02 76.5 4.7 (18.2 predicted, -2.5)
2006.03 75.4 10.8 (16.4 predicted, -1.8)
2006.04 89.0 30.2 (15.7 predicted, -0.7)
2006.05 80.9 22.2 (14.9 predicted, -0.8)
2006.06 76.5 13.9 (12.7 predicted, -2.2)
2006.07 76.7 (1) 15.8 (2) (11.3 predicted, -1.4)

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.


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