Last major update issued on June 1, 2004 at 03:15 UTC.
[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update May 3, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update May 3, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update May 3, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update April 28,
2004)]
[Archived reports (last update May 30, 2004)]
The geomagnetic field was quiet to active on May 31. Solar wind speed ranged between 462 and 546 km/sec under the influence of a stream from coronal hole CH98.
Solar flux measured at 20h UTC on 2.8 GHz was 95.4. The planetary A
index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.8).
Three hour interval K indices: 42333332 (planetary), 43333222 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight there were 4 spotted regions on the visible disk. The solar flare activity level was low. A total of 5 C class events was recorded during the day.
Region 10618 decayed slowly and rotated partly out of view at the southwest limb. Flares:
C6.5 long duration event peaking at 00:28, C2.3 at 04:37, C1.0 at 08:52, C1.1 at 05:16, C3.8 at 10:36 UTC.
Region 10621 decayed slowly and quietly.
Region 10622 was quiet and stable.
Spotted regions not numbered by NOAA/SEC:
[S410] This region rotated into view at the southeast limb late on May 31. Location at midnight: S08E78.
May 29-31: No fully or partly Earth directed CME observed.
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 elongated coronal hole (CH98) in the northern hemisphere was in a geoeffective position on May 25-29. A recurrent trans equatorial coronal hole (CH99) was in a geoeffective position on May 30-31.
Processed SOHO/EIT 284 image at 19:05 UTC on May 31. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to active on May 31-June 3 due to effects from coronal holes CH98 and CH99.
| 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 fair to poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Vibración (Venezuela). Several stations from Brazil were observed on other frequencies, one of them was Rádio Clube Paranaense on 1430 kHz. The only station from North America was WWZN Boston on 1510 kHz with a weak signal.
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 |
|---|---|---|---|---|---|---|---|
| 10618 | 2004.05.20 | 5 | 2 | S10W83 | 0290 | FAO |
classification was HAX at midnight, area 0130 |
| 10620 | 2004.05.23 | S15W68 | plage | ||||
| 10621 | 2004.05.29 | 16 | 12 | S15E38 | 0100 | DAI |
classification was DSO at midnight, area 0070 |
| 10622 | 2004.05.30 | 3 | 3 | S12E58 | 0030 | HAX | |
| S406 | emerged on 2004.05.24 |
S14W82 | plage | ||||
| S408 | emerged on 2004.05.28 |
N13W51 | plage | ||||
| S409 | emerged on 2004.05.29 |
S01E21 | plage | ||||
| S410 | visible on 2004.05.31 |
1 | S08E78 | 0010 | AXX | ||
| Total spot count: | 24 | 18 | |||||
| SSN: | 54 | 58 | |||||
| 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) |
| 2003.04 | 126.4 | 60.0 | 70.1 (-3.9) |
| 2003.05 | 115.7 | 55.2 | 67.6 (-2.5) |
| 2003.06 | 129.3 | 77.4 | 65.0 (-2.6) |
| 2003.07 | 127.7 | 83.3 | 61.8 (-3.2) |
| 2003.08 | 122.1 | 72.7 | 60.0 (-1.8) |
| 2003.09 | 112.2 | 48.7 | 59.5 (-0.5) |
| 2003.10 | 151.7 | 65.5 | 58.1 (-1.4) |
| 2003.11 | 140.8 | 67.3 | (56.5 predicted, -1.6) |
| 2003.12 | 114.9 | 46.5 | (53.5 predicted, -3.0) |
| 2004.01 | 114.1 | 37.2 | (49.1 predicted, -4.4) |
| 2004.02 | 107.0 | 46.0 | (44.8 predicted, -4.3) |
| 2004.03 | 112.0 | 48.9 | (42.1 predicted, -2.7) |
| 2004.04 | 101.2 | 39.3 | (40.0 predicted, -2.1) |
| 2004.05 | 99.8 (1) | 77.3 (2) | (36.8 predicted, -3.2) |
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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