Solar Terrestrial Activity Report

Last major update issued on August 18, 2004 at 03:25 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, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update August 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update August 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28, 2004)]
[Archived reports (last update August 10, 2004)]

Recent activity

The geomagnetic field was quiet to slightly active on August 17. Solar wind speed ranged between 302 and 368 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 135.0. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.9).
Three hour interval K indices: 31123343 (planetary), 32113323 (Boulder).

The background x-ray flux is at the class B9 level.

At midnight there were 3 spotted regions on the visible disk. The solar flare activity level was moderate. A total of 15 C and 4 M class events was recorded during the day.

Region 10656 decayed further in the southern part of the trailing spot section while development was observed between the central section and the northern part of the trailing spot section. This development coincides with the strengthening of a magnetic delta structure. Further M class flare activity is likely today and tomorrow as the region rotates over the southwest limb. Flares: C2.9 at 00:50, C2.9 at 02:03, C4.5 at 03:47, C3.2 at 04:20, M1.1 at 05:04, C5.2 at 07:40, C3.0 at 08:07, C4.9 at 08:37, C4.1 at 09:58, C2.1 at 10:24, C2.2 at 12:12, C8.8 at 13:40, C1.5 at 16:12, C1.6 at 16:48, C7.2 at 18:14, M2.4 at 19:37, M1.8 at 21:21 and M1.3 at 22:28 UTC.
Region 10661 lost the magnetic delta structure and was otherwise mostly unchanged. Flare: C1.8 at 10:47 UTC.

Spotted regions not numbered by NOAA/SEC:
[S445] This region emerged to the northeast of region 10661 on August 17. Location at midnight: N13E39.

Coronal mass ejections (CMEs)

August 15: Several small CMEs were observed over the south pole, the southwest limb and the central west limb after flare activity in region 10656. While none of these CMEs had any obvious Earth directed components, there is a chance that some of the ejected material could reach Earth.
August 16: A full halo CME was observed beginning at 15:18 UTC in LASCO C3 images. The source of this event was likely a few days behind the west limb.
August 17: A full halo CME was observed in LASCO C3 images starting at 07:42 UTC. Most of the ejected material was observed over the southeast limb, faint extensions were noted at the west limbs. The source of this CME was a fairly large filament eruption to the south and southeast of region 10661. This eruption began around 04h UTC and peaked near 06h UTC.

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 (CH110) in the southern hemisphere will likely rotate to a geoeffective position on August 22.

Processed SOHO/EIT 284 image at 01:06 UTC on August 17. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on August 18 and most of August 19. Late on August 19 or early on August 20 there is a possibility of a CME impact and unsettled to minor storm conditions are possible.

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 poor. Propagation along long distance north-south paths is poor to fair. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Rádio Papacasa (Brasil) with some interference from unidentified Brazilians. Mostly weak signals were observed throughout the MW band. From North America the best signals could be heard from WWZN 1510 and WWRU 1660 kHz.

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
10656 2004.08.06 21 26 S14W77 0930 FKC beta-gamma-delta
10657 2004.08.06     N10W67     plage
10658 2004.08.07     S05W79     plage
10659 2004.08.10     N18W32     plage
10660 2004.08.11 1   S08W24 0010 AXX spotless
10661 2004.08.12 11 12 N09E20 0470 DKO beta-gamma
S444 emerged on
    S10W45     plage
S445 emerged on
  5 N13E39 0020 DRO  
Total spot count: 33 43
SSN: 63 73

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)
2003.06 129.3 77.4 65.0 (-2.6)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 60.1 (-1.7)
2003.09 112.2 48.7 59.6 (-0.5)
2003.10 151.7 65.5 58.2 (-1.4)
2003.11 140.8 67.3 56.8 (-1.4)
2003.12 114.9 46.5 54.8 (-2.0)
2004.01 114.1 37.7 52.0 (-2.8)
2004.02 107.0 45.8 (49.1 predicted, -2.9)
2004.03 112.0 49.1 (46.5 predicted, -2.6)
2004.04 101.2 39.3 (44.3 predicted, -2.2)
2004.05 99.8 41.5 (41.0 predicted, -3.3)
2004.06 97.4 43.2 (38.2 predicted, -2.8)
2004.07 119.1 51.0 (36.3 predicted, -1.9)
2004.08 114.0 (1) 44.5 (2) (34.9 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% less.

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]