Solar Terrestrial Activity Report

Last major update issued on May 10, 2005 at 03:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 6, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 6, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update May 6, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update May 2, 2005)]

Recent activity

The geomagnetic field was quiet to active on May 9. Solar wind speed ranged between 502 and 704 km/sec. During the latter half of the day the high speed stream from CH163 gradually replaced the recent CME as the main solar wind factor. 

Solar flux measured at 20h UTC on 2.8 GHz was 110.0. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.4).
Three hour interval K indices: 33111234 (planetary), 33122223 (Boulder).

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

At midnight there were 5 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 9 C class events was recorded during the day.

Region 10758 lost quite a few spots as the leading and intermediate spot sections became more compact and added penumbral area. There's a weak magnetic delta structure in the southeastern part of the largest intermediate penumbra. An M class flare is possible. Flares: C2.8 at 03:37, C1.4 at 10:08, C8.9 at  11:03, C5.6 at 11:46, C2.5 at 12:31 and C1.8 at 12:43 UTC.
Region 10759 changed with the leading penumbra splitting off two penumbrae, one in the southeast and the other in the northeast. In a rather unusual magnetic field configuration a narrow strip of negative polarity is separating the three positive polarity penumbrae. M flares are possible. Flares: C3.7 at 21:09, C2.7 at 23:05 and C2.7 at 23:35 UTC.

Spotted regions not numbered by NOAA/SEC:
[S544] This region rotated into view at the northeast limb on May 8. Location at midnight: N03E60.
[S545] A new region emerged in the southeast quadrant on May 9. Location at midnight: S06E28.
[S546] A new region emerged in the southeast quadrant on May 9 just south of region S545. Location at midnight: S12E28.

Coronal mass ejections (CMEs)

May 7-9: No obviously fully or partly potentially geoeffective CMEs were observed.

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 large recurrent coronal hole (CH163) in the northern hemisphere was in an Earth facing position on May 6-7. A small coronal hole in the northern hemisphere near the equator will be in an Earth facing position on May 10-11.

Processed SOHO/EIT 284 image at 01:06 UTC on May 10. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected be quiet to active on May 10 due to a high speed stream from CH163 and quiet to unsettled on May 11-12. Quiet to active is possible on May 13-14 due to a low speed stream from CH164.

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. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and CPN Radio (Perú). Rádio Cristal (Brazil) on 1350 kHz had the best signal of the observed trans Atlantic stations. From North America both WWZN on 1510 and WWRU on 1660 were audible. 

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.

SEC active region data for May 9 was unavailable at the time of this report.

Active region Date numbered SEC
Location at midnight Area Classification Comment
10758 2005.05.02 51 32 S08W13 0500 FKI beta-gamma-delta
10759 2005.05.08 8 10 N12E60 0430 EKO  
S544 visible on
  1 N03E60 0010 AXX  
S545 emerged on
  7 S06E28 0030 CSO  
S546 emerged on
  3 S12E28 0030 DSO  
Total spot count: 66 53  
SSN: 106 103  

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)
2004.03 112.0 49.1 47.1 (-2.2)
2004.04 101.2 39.3 45.5 (-1.6)
2004.05 99.8 41.5 43.8 (-1.7)
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 (34.8 predicted, -1.1)
2004.12 94.5 17.9 (33.4 predicted, -1.4)
2005.01 102.2 31.3 (30.9 predicted, -2.5)
2005.02 97.2 29.1 (28.3 predicted, -2.6)
2005.03 89.9 24.8 (26.5 predicted, -1.8)
2005.04 86.0 24.4 (24.6 predicted, -1.9)
2005.05 108.6 (1) 19.7 (2) (22.0 predicted, -2.6)

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]