Solar Terrestrial Activity Report

Last major update issued on July 31, 2006 at 05:10 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 quiet on July 29. Solar wind speed ranged between 350 and 469 km/s (all day average 405 km/s - decreasing 74 km/s from the previous day). A high speed stream from CH234 began to dominate the solar wind early on July 31.

Solar flux measured at 20h UTC on 2.8 GHz was 73.9. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.6).
Three hour interval K indices: 22100112 (planetary), 22211112 (Boulder).

The background x-ray flux is at the class A2 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10901 redeveloped a trailing spot while the leader spot continued to lose penumbral area.
New region 10902 emerged quickly early in the day in the southwest quadrant, then began to decay slowly.

Spotted regions not numbered by NOAA/SEC:
[S669] This region emerged in the southwest quadrant on July 30. Polarities are reversed making this a candidate for the first cycle 24 region.

Coronal mass ejections (CMEs)

July 28-30: 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 well defined recurrent trans equatorial coronal hole (CH234) was in an Earth facing position on July 28-30.

Processed SOHO/EIT 284 image at 01:06 UTC on July 31. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to major storm on July 31 and August 1 due to a high speed stream from CH234 becoming quiet to active on August 2 and quiet to unsettled on August 3.

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 fair. Propagation did not favor a particular area tonight. Stations from the easternmost parts of North America, from Venezuela, Perú, Brazil, Argentina and Uruguay were all heard. 1470 kHz had CPN Radio (Perú) dominating for at least 30 minutes around LSR.

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
10901 2006.07.22 1 3 N06W43 0010 HSX classification was CAO at midnight, area 0030
10902 2006.07.30 2 2 S10W21 0030 CSO classification was HAX at midnight, area 0020
location: S09W32
S669 2006.07.30   1 S12W55 0010 HRX candidate cycle 24 region
Total spot count: 3 6  
SSN: 23 36  

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 75.8 (1) 22.3 (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.


[DX-Listeners' Club]