Solar Terrestrial Activity Report

Last major update issued on July 30, 2007 at 04:35 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update July 23, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update July 23, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update July 23, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update July 1, 2007)]

Recent activity

The geomagnetic field was quiet to active on July 29. Solar wind speed ranged between 354 and 726 km/s (average speed was 495 km/s, increasing 140 km/s over the previous day) under the influence of a high speed stream from CH280.

Solar flux measured at 20h UTC on 2.8 GHz was 69.0. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.1). Three hour interval K indices: 34233233 (planetary), 34233333 (Boulder).

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

At midnight there were 2 spotted regiona on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10965 decayed and could soon become spotless.

Spotted regions not numbered by NOAA/SEC:
[S706] A new region emerged in the southwest quadrant on July 29. Location at midnight: S08W13.

Coronal mass ejections (CMEs)

July 27-29: No obvious fully or partly Earth directed CMEs were observed.

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 (CH280) was in an Earth facing position on July 25-27. A new trans equatorial coronal hole (CH281) was in an Earth facing position on July 29-30.

.

Processed STEREO 195 image at 20:55 UTC on July 29. The darkest areas on the solar disk are likely coronal holes.

Propagation

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 northeast-southwest paths is poor to fair.

Monitoring remarks from a location near N58E06: July 30: Some stations from Argentina, Brazil, Perú and Argentina were audible during the night, however, most signals were weak. At LSR 1470 kHz had a mix of Radio Cristal del Uruguay, CPN Radio and a station from Brazil. After LSR the strongest TA signal was that of 1500 kHz Radio Dos Mil.

Forecast

The geomagnetic field is expected to be quiet to active on July 30 - August 3, first due to effects from CH280, later on replaced by CH281. Quiet conditions could return on August 4, then become quiet to active again on August 5-6 due to effects from CH282.

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.

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
10965 2007.07.28 4 2 S11E10 0040 CSO classification was AXX at midnight, area 0010
S706 2007.07.29   2 S08W13 0010 AXX  
Total spot count: 4 4  
SSN: 14 24  

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)
2006.05 80.9 22.3 17.3 (+0.2)
2006.06 76.5 13.9 16.3 (-1.0)
2006.07 75.7 12.2 15.3 (-1.0)
2006.08 79.0 12.9 15.6 (+0.3)
2006.09 77.8 14.4 15.6 (+0.0)
2006.10 74.3 10.4 14.2 (-1.4)
2006.11 86.3 21.5 12.7 (-1.5)
2006.12 84.5 13.6 12.1 (-0.6)
2007.01 83.3 16.9 (11.9 predicted, -0.2)
2007.02 77.7 10.6 (11.3 predicted, -0.6)
2007.03 72.2 4.8 (10.8 predicted, -0.5)
2007.04 72.4 3.7 (10.8 predicted, unchanged)
2007.05 74.4 11.7 (10.6 predicted, -0.2)
2007.06 73.7 12.0 (10.7 predicted, +0.1)
2007.07 71.8 (1) 14.8 (2) (11.0 predicted, +0.3)

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]