Solar Terrestrial Activity Report

Last major update issued on August 28, 2005 at 03:30 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update August 2, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 2, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 2, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update August 13, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on August 27. Solar wind speed ranged between 371 and 531 (all day average 436) km/sec, generally decreasing all day.

Solar flux measured at 20h UTC on 2.8 GHz was 92.1. The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.6).
Three hour interval K indices: 31222211 (planetary), 31222221 (Boulder).

The background x-ray flux is at the class A9 level.

At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 1 C class event was recorded during the day.

Region 10800 decayed and could lose the leader spots before rotating out of view.
Region 10801 reemerged with a few spots.
Region 10803 decayed slowly and lost the magnetic delta structure. There is still some polarity intermixing. Flare: C1.4 at 20:51 UTC
New region 10805 rotated into view at the southeast limb. There's not much separating the opposite polarity areas in this region.

Coronal mass ejections (CMEs)

August 26-27: No obvious partly or fully Earth directed CMEs were observed.
August 25: A fast and wide full halo CME was observed after the major M6 event in region 10803. This CME was not as dense as we often observe and it was difficult to track the expansion front over the western limbs.

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 coronal hole (CH184) in the southern hemisphere will likely rotate to an Earth facing position on August 27-28.

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on August 28-29. A high speed stream from CH184 could reach Earth during the latter half of August 30 and cause unsettled to minor storm conditions that day and on August 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.

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 very poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay with an unusually weak signal. Only a few stations could be heard with audio on other frequencies. After LSR on August 27 conditions were good to Paraguay and Argentina. 

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
10800 2005.08.19 7 5 N16W61 0060 EAO  
10801 2005.08.20 5 4 N09W31 0020 DSO  
10802 2005.08.24     S12W26     plage
10803 2005.08.24 26 20 N11E40 0130 DAI beta-gamma
10804 2005.08.25 1   N11W14 0010 AXX spotless
10805 2005.08.27 2 3 S08E73 0060 DSO  
Total spot count: 41 32  
SSN: 91 72  

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)
2004.06 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 (-0.6)
2005.02 97.2 29.2 (33.5 predicted, -1.1)
2005.03 89.9 24.5 (32.1 predicted, -1.4)
2005.04 86.0 24.4 (30.2 predicted, -1.9)
2005.05 99.3 42.6 (27.6 predicted, -2.6)
2005.06 93.7 39.6 (26.1 predicted, -1.5)
2005.07 96.4 39.9 (25.1 predicted, -1.0)
2005.08 91.0 (1) 55.8 (2) (23.2 predicted, -1.9)

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]