Solar Terrestrial Activity Report

Last major update issued on June 3, 2007 at 04:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-23 (last update June 3, 2007)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update June 3, 2007)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update June 3, 2007)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports (last update May 18, 2007)]

Recent activity

The geomagnetic field was quiet on June 2. Solar wind speed ranged between 340 and 415 km/s (average speed was 369 km/s, increasing 21 km/s over the previous day). A fairly low speed stream associated with CH271 began to dominate the solar wind after 16h UTC. The interplanetary magnetic field was predominantly northwards and the effects from CH271 have so far been very mild.

Solar flux measured at 20h UTC on 2.8 GHz was 83.2. The planetary A index was 7 (STAR Ap - based on the mean of three hour interval ap indices: 6.6). Three hour interval K indices: 22211212 (planetary), 22221222 (Boulder).

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

At midnight there were 2 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 2 M class events were recorded during the day.

Region 10959 decayed slowly and quietly.
Region 10960 is still a complex region capable of producing M flares. Another major flare, possibly even an X class flare, could occur anytime over the next few days. There is a fairly strong magnetic delta structure in the northern central part of the largest trailing penumbra. None of the flares have yet been associated with significant CMEs. Flares: M2.5 at 06:11 and M1.0 at 10:35 UTC. Early on June 3, at 02:12 UTC, a major M7.0 flare was recorded.

Coronal mass ejections (CMEs)

May 31 - June 2: No obvious fully or partially Earth directed CMEs were observed in LASCO imagery.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A recurrent coronal hole (CH271) in the southern hemisphere was in an Earth facing position on May 30-31.

Processed STEREO 195 image at 14:45 UTC on June 2. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet to unsettled on June 3-4 due to effects from CH271 and quiet on June 5.

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

Daily monitoring will not resume until a local noise problem (related to construction work on a neighboring property) has been fixed. Occasional monitoring reports will be submitted when propagation is good.

April 8, 2007: Stations from the Canadian Atlantic provinces had strong signals during the night. Some stations from the northeastern USA and from Florida did well too, in particular 1510 WWZN was impressive.

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
10958 2007.05.29 1   S12E13 0010 HSX spotless
10959 2007.06.01 2 2 S12E36 0030 CSO classification was HSX at midnight, area 0020
10960 2007.06.01 12 33 S07E62 0480 FKC beta-gamma-delta
S703 2007.05.22     S09W67     plage
Total spot count: 15 35  
SSN: 45 55  

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)
2006.04 89.0 30.2 17.1 (-0.3)
2006.05 80.9 22.3 17.3 (+0.2)
2006.06 76.5 13.9 16.3 (-1.0)
2006.07 75.7 12.2 15.3 (-1.0)
2006.08 79.0 12.9 15.6 (+0.3)
2006.09 77.8 14.4 15.6 (+0.0)
2006.10 74.3 10.4 14.2 (-1.4)
2006.11 86.3 21.5 12.7 (-1.5)
2006.12 84.5 13.6 (12.1 predicted, -0.6)
2007.01 83.3 16.9 (11.7 predicted, -0.4)
2007.02 77.7 10.6 (11.1 predicted, -0.6)
2007.03 72.2 4.8 (10.7 predicted, -0.4)
2007.04 72.4 3.7 (10.9 predicted, +0.2)
2007.05 74.4 11.7 (11.0 predicted, +0.1)
2007.06 81.3 (1) 2.9 (2) (11.3 predicted, +0.3)

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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