Solar Terrestrial Activity Report

Last major update issued on May 31, 2005 at 04:10 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 15, 2005)]

Recent activity

The geomagnetic field was unsettled to severe storm on May 30. Solar wind speed ranged between 410 and 540 km/sec. The interplanetary magnetic field (at ACE) was very strongly southwards between 05 and 17h UTC, this caused minor to severe geomagnetic storming. 

Solar flux measured at 20h UTC on 2.8 GHz was 94.9. The planetary A index was 67 (STAR Ap - based on the mean of three hour interval ap indices: 66.8).
Three hour interval K indices: 43676754 (planetary), 33566554 (Boulder).

The background x-ray flux is at the class B1 level.

At midnight there were 4 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 10767 decayed slowly and quietly.
Region 10770 developed slowly and was quiet.
New region 10771 emerged in the northwest quadrant.

Spotted regions not numbered by NOAA/SEC:
[S552] This region emerged quickly after noon in the southeast quadrant in a hot plage area. The opposite polarity fields are poorly separated and further development is likely.

Coronal mass ejections (CMEs)

May 28-30: 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 coronal hole (CH168) in the southern hemisphere was in an Earth facing position on May 29. A recurrent coronal hole (CH169) in the northern hemisphere will rotate into an Earth facing position on June 1-3.

Processed SOHO/EIT 284 image at 19:06 UTC on May 30. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to active on May 31. Unsettled to active conditions are possible on June 1-2 due to a high speed stream from CH168.

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 useless. Propagation along long distance north-south paths is excellent. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: None, many stations from Brazil and Argentina were audible and of course Radio Cristal del Uruguay. Conditions were too good as it was difficult to get more than a few seconds of continuous audio from a single station. On 1540 kHz two stations from Argentina were noted, while other frequencies above 1350 kHz at times were stuffed by Brazilian stations.

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
10765 2005.05.19     N08W81     plage
10766 2005.05.21     N13W45     plage
10767 2005.05.21 22 23 S09W44 0240 EAC beta-gamma
classification was DAI at midnight, area 0150
10769 2005.05.28 4   S08E49 0020 BXO spotless
10770 2005.05.29 7 11 N12W14 0060 DAO  
10771 2005.05.30 3 4 N24W33 0040 BXO classification was DSO at midnight
S552 emerged on
2005.05.30
  6 S18E61 0050 DAO  
Total spot count: 36 44  
SSN: 76 84  

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 99.4 (1) 62.8 (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]