Last major update issued on May 19, 2005 at 04:20 UTC.
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[Historical solar and
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The geomagnetic field was quiet to active on May 18. Solar wind speed ranged between 445 and 612 km/sec.
Solar flux measured at 20h UTC on 2.8 GHz was 83.8. The planetary
A
index was 13 (STAR Ap - based on the mean of three hour interval ap
indices: 13.4).
Three hour interval K indices: 33434322 (planetary), 23434221 (Boulder).
The background x-ray flux is at the class A8 level.
At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 2 C class events was recorded during the day.
Region 10759 was quiet and stable.
Region 10763 decayed quickly and only had a few penumbraless spots by the end of the day. The region will likely become
spotless today. Flares: C1.6 at 08:28 and C2.0 at 14:49 UTC.
Spotted regions not numbered by NOAA/SEC:
[S549] This region emerged in the southwest quadrant on May 18. Location at
midnight: S12W08.
[S550] A new region rotated into view at the northeast limb on May 18. Location at midnight: N08E79.
May 16 and 18: No obviously fully or partly potentially geoeffective CMEs were observed.
May 17: A very faint and slow full halo CME was observed after an M1.8 flare in region 10763 early in the day. This CME
could reach Earth early on May 20.
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 (CH166) in the northern hemisphere will likely be in an Earth facing position on May 17. CH166 may be too far to the north to become geoeffective.
Processed SOHO/EIT 284 image at 19:06 UTC on May 18. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected be quiet to unsettled on May 19 becoming quiet to active on May 20 due to a weak CME. Quiet to unsettled is likely on May 21-22.
| 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) 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 very poor. 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. On other frequencies a few stations from Brazil (with 930 Rádio Metropolitana as the most consistent signal) and Argentina could be heard.
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 |
|---|---|---|---|---|---|---|---|
| 10759 | 2005.05.08 | 9 | 1 | N12W62 | 0280 | CHO | classification was HHX at midnight |
| 10763 | 2005.05.12 | 17 | 3 | S16W24 | 0120 | EAI | classification was BXO at midnight, area 0010 |
| S548 | 2005.05.17 | S13W01 | plage | ||||
| S549 | 2005.05.18 | 1 | S12W08 | 0010 | AXX | ||
| S550 | 2005.05.18 | 1 | N08E79 | 0020 | HSX | ||
| Total spot count: | 26 | 6 | |||||
| SSN: | 46 | 46 | |||||
| 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 | 107.4 (1) | 44.1 (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.
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