Solar Terrestrial Activity Report

Last major update issued on August 12, 2004 at 04:30 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, 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 active on August 11. Solar wind speed ranged between 476 and 706 km/sec under the influence of a high speed stream from coronal hole CH109.

Solar flux measured at 20h UTC on 2.8 GHz was 130.8. The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 13.4).
Three hour interval K indices: 22343333 (planetary), 32333332 (Boulder).

The background x-ray flux is at the class B7 level.

At midnight there were 4 spotted regions on the visible disk. The solar flare activity level was low. A total of 20 C class events were recorded during the day.

Region 10656 developed further with the huge central penumbra extending eastwards and southwards. Although the region is large and it currently has two small magnetic deltas, there are no long neutral lines (often associated with major flare activity). Some positive polarity is emerging between the leading and central negative polarity areas. M class flares are possible. Flares: C3.2 at 03:46, C1.3 at 07:06, C2.0 at 07:16, C1.1 at 08:10, C1.3 at 08:26, C2.9 at 08:52, C4.2 at 10:15, C7.6 at 11:41, C1.3 at 12:09, C1.7 at 12:49, C1.8 at 14:11, C1.4 at 15:05, C1.8 at 15:39, C2.8 at 16:17, C1.6 at 16:36, C1.7 at 17:53, C1.3 at 21:14, C1.0 at 21:34, C1.0 at 22:10 and C3.7 at 22:37 UTC.
Region 10657 was quiet and stable.
Region 10659 was quiet and stable.
New region 10660 emerged near the southeast limb in a bright plage area.

Coronal mass ejections (CMEs)

August 9-11: No obviously Earth directed CMEs were detected in LASCO images.

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

The southernmost part of a large, poorly defined coronal hole (CH109) in the northern hemisphere was in a geoeffective position on August 8-9.

Processed SOHO/EIT 284 image at 19:06 UTC on August 11. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on August 12 due to a high speed stream from coronal hole CH109, quiet to unsettled is likely on August 13.

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 poor. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: unidentified station from Brazil early in the night, Radio Vibración (Venezuela) later. A few stations from North America were noted at local sunrise with Radio Disney on 1650 kHz having the best signal.

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
10656 2004.08.06 68 77 S13E03 0990 EKC beta-gamma-delta
area was 1150
at midnight
10657 2004.08.06 1 1 N10E12 0060 HSX  
10658 2004.08.07     S05W01     plage
10659 2004.08.10 2 3 N17E46 0040 CSO  
10660 2004.08.11 4 5 S08E62 0020 CRO classification was DSO
at midnight
S444 emerged on
2004.08.09
    S10E33     plage
Total spot count: 75 86
SSN: 115 126

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 98.7 (1) 23.8 (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.


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