Solar Terrestrial Activity Report

Last major update issued on May 16, 2005 at 03:45 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 active to extremely severe storm on May 15. Solar wind speed ranged between 410 and 992 km/sec. A very strong solar wind shock was observed at SOHO at 02:18 UTC with a sudden increase in solar wind speed from 514 to 971 km/sec. For the next 3 hours the interplanetary magnetic field did not have any sustained periods with northerly or southerly field direction. At 05:30 UTC the IMF swung extremely strongly southwards, then swung slowly northwards and was northwards after 08:15 UTC and until about 17h UTC. Since then the IMF has been weakly to moderately southwards. The extreme southwards IMF between 05:30 and 06:10 UTC caused extremely severe geomagnetic storming. Boulder recorded magnetic deviations of 682 nT, far exceeding what is required to achieve a K index of 9.

Solar flux measured at 20h UTC on 2.8 GHz was 103.0. The planetary A index was 105 (STAR Ap - based on the mean of three hour interval ap indices: 105.4).
Three hour interval K indices: 55984445 (planetary), 56973345 (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 moderate. A total of 7 C and 1 M class events was recorded during the day.

Region 10758 continued to produce flares from behind the southwest limb. Flares: C2.5 at 00:11, C1.4 at 02:40, C1.2 at 06:15 and C1.0 at 07:08 UTC.
Region 10759 decayed further and was quiet.
Region 10762 decayed quickly and lost all trailing spots, the region could become spotless today or tomorrow.
Region 10763 developed slowly with a positive polarity area emerging to the south of the leading negative polarity area. The region, which has had a magnetic delta structure in the the trailing penumbra for several days, became much more active during the latter half of the day. Further M class flares are possible. Flares: C1.2 at 17:44, C1.8 at 18:55, C2.9 at 20:46 and an impulsive M3.5 at 22:36 UTC. The M3 event was accompanied by a strong type II radio sweep.

Coronal mass ejections (CMEs)

May 13: A bright and fast CME aimed directly at Earth was first observed in LASCO C2 images at 17:22 and in C3 at 17:42 UTC and was associated with the major M8 proton flare in region 10759. The propagation of the shock wave on and near the solar surface was extremely impressive in EIT 195 images.
May 14-15: No obviously fully or partly potentially geoeffective CMEs were observed. At the time this report will be posted it is uncertain if the M3 flare in region 10763 late on May 15 was associated with a potentially geoeffective CME.

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 new coronal hole (CH165) in the southern hemisphere was exposed when corona was blown away by the M8 flare on May 13, CH165 was in an Earth facing position on May 13-14. A recurrent coronal hole (CH166) in the northern hemisphere will likely be in an Earth facing position on May 17.

Processed SOHO/EIT 284 image at 01:06 UTC on May 16. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected be unsettled to minor storm on May 16 and quiet to unsettled on May 17-18.

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 useless. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. Only a few other stations, like Rádio Clube Paranaense on 1430 and Rádio 9 de Julho on 1600 kHz were heard on other frequencies.

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
10759 2005.05.08 14 9 N11W20 0290 DHO location was N11W22 at midnight
10762 2005.05.10 6 3 S13W53 0060 DAO classification was HAX at midnight, area 0030, location S12W55
10763 2005.05.12 19 24 S15E16 0140 DAI beta-gamma-delta
classification was EAI at midnight, area 0190, location S16E16
Total spot count: 39 36  
SSN: 69 66  

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)
2005.05 110.3 (1) 38.9 (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]