Solar Terrestrial Activity Report

Last major update issued on May 3, 2006 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 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 inactive to quiet on May 2. Solar wind speed ranged between 278 and 304 (all day average 290) km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 89.4. The planetary A index was 4 (STAR Ap - based on the mean of three hour interval ap indices: 3.5).
Three hour interval K indices: 10100121 (planetary), 11211321 (Boulder).

The background x-ray flux is at the class A9 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 10875 decayed slowly and quietly.
Region 10876 decayed further and had only a single tiny spot left at midnight. The region could become spotless today.
Region 10878 was quiet and stable.
New region 10879 emerged on May 1 in the northeast quadrant and was numbered the following day by SEC.

Coronal mass ejections (CMEs)

April 30: A very faint CME may have been associated with a C1.8 flare in region 10875. LASCO C2 images has traces of this CME just before noon.
May 1: A faint full halo CME was observed in LASCO C2 images from 16:30 UTC and was likely associated with a long duration C1 event in region 10875.
May 2: No partly or fully Earth directed CMEs were observed in LASCO imagery.

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) will rotate into an Earth facing position on May 2-3.

Processed SOHO/EIT 284 image at 01:06 UTC on May 3. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet on May 3. Slow CMEs observed on April 30 and May 1 could reach Earth on May 4 and cause unsettled to active conditions. A strong high speed stream from CH222 will likely reach Earth on May 5 and cause unsettled to minor or major storm conditions.

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 very poor to poor. Propagation on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Radio Vibración (Venezuela), CPN Radio (Perú) and Radio Cristal del Uruguay were all noted at times. At local sunrise many stations from Brazil became audible above 1350 kHz. Two stations were audible on 1510 kHz, one of them had strong peaks.

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 7 7 S12W47 0140 DAO  
10876 2006.04.24 5 1 S18W16 0040 CSO classification was AXX at midnight, area 0000
10877 2006.04.26     S05W28     plage
10878 2006.04.26 2 2 N13E31 0060 CSO classification was HSX at midnight
10879 2006.05.02 4 7 N16E07 0050 DAO formerly region S649
S647 2006.04.29     N08W11     plage
Total spot count: 18 17  
SSN: 58 57  

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 91.4 (1) 3.5 (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.


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