Solar Terrestrial Activity Report

Last major update issued on May 9, 2005 at 04:45 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 active to severe storm on May 8. Solar wind speed ranged between 402 and 788 km/sec. The CME observed on May 6 (probably) arrived at SOHO at 09:07 UTC and caused minor to severe geomagnetic storm conditions.

Solar flux measured at 20h UTC on 2.8 GHz was 101.3. The planetary A index was 64 (STAR Ap - based on the mean of three hour interval ap indices: 64.5).
Three hour interval K indices: 66457644 (planetary), 65346643 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 3 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 10758 developed quickly in the leading spot section while decaying in the trailing spots. An M class flare is possible.
New region 10759 rotated partly into view on May 7 and was numbered by SEC the next day. The region is complex with both polarities present within the leading penumbra. M flares are possible. Flare: C1.2 at 09:28 UTC.

Spotted regions not numbered by NOAA/SEC:
[S544] This region rotated into view at the northeast limb on May 8. Location at midnight: N03E78.

Coronal mass ejections (CMEs)

May 6: A full halo CME was observed in LASCO C3 images beginning at 18:18 UTC. Material distribution around the disk suggest a centrally placed backsided source in the northern hemisphere. Another and more interesting moderately fast CME was observed nearly simultaneously with most of the ejected material seen over the southeast limb. This was at least a partial halo CME, the presence of the other CME makes it hard to determine the full extent. Its source was the long duration event in region 10758.
May 7-8: 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.

Processed SOHO/EIT 284 image at 01:06 UTC on May 9. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected be unsettled to minor storm on May 9-10 due to a high speed stream from CH163.

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 useless. Propagation along long distance north-south paths is good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and several stations from Brazil. On other frequencies a large number of stations from Brazil 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.

Active region Date numbered SEC
Location at midnight Area Classification Comment
10758 2005.05.02 51 55 S08W06 0170 FAI beta-gamma
area was 0280 at midnight
10759 2005.05.08 8 7 N12E71 0340 DKO beta-delta
classification was EKO at midnight
S541 emerged on
    S15W77     plage
S543 visible on
  1 N03E78 0020 HSX  
Total spot count: 59 63  
SSN: 79 93  

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)
2005.05 108.4 (1) 16.3 (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]