Solar Terrestrial Activity Report

Last major update issued on May 6, 2006 at 05:00 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 quiet to active on May 5. Solar wind speed ranged between 297 and 359 (all day average 331) km/sec. Solar wind speed increased slowly and has early on May 6 reached 400 km/sec under the increasing influence of a moderately high speed stream from CH222.

Solar flux measured at 20h UTC on 2.8 GHz was 86.7. The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 13.3).
Three hour interval K indices: 43432201 (planetary), 43542101 (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 10878 decayed slowly and quietly.
Region 10879 decayed further and had only a single tiny spot left at the end of the day.
Region 10880 was quiet and stable.
New region 10881 rotated into view at the southeast limb.

Coronal mass ejections (CMEs)

May 3 and 5: No partly or fully Earth directed CMEs were observed in LASCO imagery.
May 4: A partial halo CME was observed in LASCO images early in the day following a filament eruption near spotless region 10876.

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 recurrent trans equatorial coronal hole (CH222) was in an Earth facing position on May 2-4.

Processed SOHO/EIT 284 image at 01:06 UTC on May 6. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to minor storm on May 6 due to a high speed stream from CH222. Quiet to active conditions are likely on May 7 becoming mostly quiet on May 8-9.

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 Vibración (Venezuela) and Radio Cristal del Uruguay were both audible at times with weak signals. Some of the most often heard stations from Newfoundland and Nova Scotia were audible at low levels during the hour before local sunrise.

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
10875 2006.04.23 3   S13W85 0070 CSO rotated out of view
10876 2006.04.24     S17W55     plage
10877 2006.04.26     S05W67     plage
10878 2006.04.26 2 2 N14W09 0020 HSX  
10879 2006.05.02 3 1 N16W31 0020 CSO classification was AXX at midnight, area 0010
10880 2006.05.04 2 2 S08E50 0100 CSO  
10881 2006.05.05 1 1 S12E75 0000 AXX  
S647 2006.04.29     N08W50     plage
S650 2006.05.03     S12E23     plage
Total spot count: 11 6  
SSN: 61 46  

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 90.1 (1) 6.7 (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.


[DX-Listeners' Club]