Solar Terrestrial Activity Report

Last major update issued on May 11, 2006 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 April 1, 2006)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 1, 2006)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 1, 2006)]
[Historical solar and geomagnetic data charts 1954-2005 (last update March 3, 2006)]
[Archived reports (last update May 3, 2006)]

Recent activity

The geomagnetic field was inactive to unsettled on May 10. Solar wind speed ranged between 349 and 434 (all day average 370) km/sec. A high speed stream from CH223A was observed beginning at ACE just before 19h UTC. Early on May 11 solar wind speed has increased to about 550 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 78.2. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.6).
Three hour interval K indices: 00011113 (planetary), 10011013 (Boulder).

The background x-ray flux is at the class A4 level.

At midnight there were 2 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 10880 decayed further and was quiet.
Region 10882 decayed and is losing its trailing spots. The region will rotate out of view late today.

Coronal mass ejections (CMEs)

May 8-10: No partly or fully Earth directed CMEs were observed in LASCO imagery.

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

Recurrent coronal holes (CH223A and CH223B) in the northern hemisphere was in an Earth facing position on May 8-11. A trans equatorial coronal hole (CH224) will likely rotate into an Earth facing position on May 13-15.

Processed SOHO/EIT 284 image at 01:06 UTC on May 11. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be unsettled to minor storm on May 11-13 and quiet to active on May 14 due to high speed streams from CH223A and CH223B. An other high speeed stream (from CH224) could arrive on May 16 and cause unsettled to minor storm conditions until May 18.

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 poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Tonight Radio Cristal del Uruguay was weakly audible at times. After LSR 740 Rádio Sociedade was about the only TA signal with audio. Between 03 UTC and LSR propagation was unusual with no North American stations heard on the antenna aimed that way. However, 1510 WWZN, 930 CJYQ and 1660 WWRU were all audible on the antenna favoring signals from the southwest. Even signals from European stations were considerably attenuated by the ongoing disturbance.

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
10878 2006.04.26     N12W74     plage
10880 2006.05.04 2 2 S09W17 0020 HAX  
10881 2006.05.05     S08E04     plage
10882 2006.05.06 5 5 S12W70 0110 EAO area was 0060 at midnight
10883 2006.05.07     S04E13     plage
S650 2006.05.03     S12W42     plage
Total spot count: 7 7  
SSN: 27 27  

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)
2005.02 97.2 29.2 33.9 (-0.7)
2005.03 89.9 24.5 33.5 (-0.4)
2005.04 86.0 24.2 31.6 (-1.9)
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 (24.5 predicted, -1.0)
2005.12 90.7 41.2 (21.8 predicted, -2.7)
2006.01 83.4 15.4 (18.7 predicted, -3.1)
2006.02 76.5 4.7 (15.6 predicted, -3.1)
2006.03 75.4 10.8 (13.4 predicted, -2.2)
2006.04 89.0 30.2 (12.7 predicted, -0.7)
2006.05 86.9 (1) 17.4 (2) (12.2 predicted, -0.5)

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.


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