Solar Terrestrial Activity Report

Last major update issued on May 4, 2005 at 04:20 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update April 4, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 4, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 4, 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 quiet to unsettled on May 3. Solar wind speed ranged between 431 and 563 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 112.3. The planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.8).
Three hour interval K indices: 32233321 (planetary), 32233321 (Boulder).

The background x-ray flux is at the class B3 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 10756 decayed slowly losing spots and penumbral area.
Region 10757 decayed slowly and quietly.
Region 10758 developed slowly. An M class flare is possible. Flare: C2.7 at 10:36 UTC.

Coronal mass ejections (CMEs)

May 1: A brighter full halo CME was observed in LASCO C3 images beginning at 01:42 UTC. Considerable large scale reshaping of the corona to the south of region 10756 was observed late on April 30 and early on May 1. However, since I couldn't observe any significant eruptive event or a disappearing filament during the relevant time frame, it is at this time uncertain if the CME was backsided (with the same source as the CME observed on April 30) or had its origin near region 10756.
May 2: A full halo CME was observed in LASCO C3 images beginning at 06:18 UTC. There was no significant activity on the visible disk during the hours just before this observation and the origin of the CME was likely backsided, possibly with the same origin as the CMEs observed on April 30 and May 1. A large and bright CME was observed over most of the eastern limb late in the day and early on May 3.
May 3: A partial halo CME was observed in LASCO C3 images beginning at 19:42 UTC. The source of this CME was likely backsided.

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 coronal hole (CH163) in the northern hemisphere will likely rotate to an Earth facing position on May 6-7.

Processed SOHO/EIT 284 image at 19:06 UTC on May 3. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected be quiet to unsettled on May 4-6.

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 poor. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay  and Radio Vibración (Venezuela). On other frequencies a few stations from North America (on 800, 930, 1130, 1510 and 1660 kHz) were audible on the EWE directed NNW while on the antenna aimed to the southwest mostly stations from Brazil and Argentina (710 Radio Diez had the best signal) could be heard.

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
10756 2005.04.25 30 21 S07W38 0770 DKC beta-delta
10757 2005.04.28 5 4 S06W65 0070 DAO area was 0050 at midnight
10758 2005.05.02 14 15 S07E63 0200 DAI classification was EAI at midnight
S540 emerged on
    S10W45     plage
S541 emerged on
    S15W12     plage
Total spot count: 49 40  
SSN: 79 70  

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)
2005.05 112.1 (1) 6.3 (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]