Last update issued on April 18, 2003 at 01:45 UTC.
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[Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2003)]
[Graphical comparison of cycles 10, 13, 17, 20 and 23 (last update April 2, 2003)]
[Historical solar and geomagnetic data charts 1954-2003 (last update April 13, 2003)]
[Archived reports (last update April 14, 2003)]
The geomagnetic field was unsettled to minor storm on April 17. Solar wind speed ranged between 608 and 768 km/sec under the influence of a high speed stream from coronal hole CH32. Wind speed slowly decreased during the latter half of the day.
Solar flux measured at 20h UTC on 2.8 GHz was 101.5. The planetary A
index was 30 (STAR Ap - based on the mean of three hour interval ap indices: 30.9).
Three hour interval K indices: 35554533 (planetary), 35544432 (Boulder).
The background x-ray flux is at the class B2 level.
At midnight there were 3 spotted regions on the visible disk. Solar flare activity was low. Only 1 C class event was recorded during the day.
Region 10334 developed a trailing spot and was otherwise quiet and stable.
Region 10335 developed slowly adding several small spots.
New region 10336 rotated into view at the northeast limb.
An active region behind the southeast limb should soon rotate into view. Flare: C4.4 at 22:16 UTC.
April 15-17: No obviously geoeffective CMEs 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 large trans equatorial southern hemisphere coronal hole (CH32) was in a geoeffective position on April 11-13. A small coronal hole (CH33) in the southern hemisphere will likely rotate into a geoeffective position on April 18. A recurrent coronal hole (CH34) in the northern hemisphere will rotate into a geoeffective position on April 18-19. A recurrent coronal hole (CH35) in the southern hemisphere is likely to be in a geoeffective position on April 21-22.
Processed SOHO EIT 284 image at 19:06 UTC on April 17. Any black areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to unsettled is likely on April 18-20 while high speed coronal hole streams will cause unsettled to active conditions on April 21-22. Long distance medium wave (AM) band propagation along east-west paths over high and upper middle latitudes is likely to remain very poor until at least April 19. Propagation along north-south paths is fair and is expected to remain fair until at least April 18. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay.]
| 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.
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.
Compare to the previous day's image.
Data for all numbered solar regions according to the Solar Region Summary provided by SEC/NOAA. 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.
| Solar region | Date numbered | SEC spot count |
STAR spot count |
Location at midnight | Area | Classification | Comment |
|---|---|---|---|---|---|---|---|
| 10332 | 2003.04.07 | N12W73 | plage | ||||
| 10334 | 2003.04.10 | 4 | 3 | S08W24 | 0060 | DSO | |
| 10335 | 2003.04.10 | 2 | 8 | S22E06 | 0010 | BXO | |
| 10336 | 2003.04.17 | 1 | 1 | N12E75 | 0100 | HSX | |
| S138 | emerged on 2003.04.16 |
S07W15 | now spotless | ||||
| S139 | emerged on 2003.04.16 |
N18E59 | now spotless | ||||
| Total spot count: | 7 | 12 | |||||
| SSN: | 37 | 42 | |||||
| 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) |
| 2002.03 | 179.5 | 98.4 | 113.3 (-1.3) |
| 2002.04 | 189.8 | 120.7 | 110.5 (-2.9) |
| 2002.05 | 178.4 | 120.8 | 108.8 (-1.7) |
| 2002.06 | 148.7 | 88.3 | 106.2 (-2.6) |
| 2002.07 | 173.5 | 99.6 | 102.7 (-3.5) |
| 2002.08 | 183.6 | 116.4 | 98.7 (-4.0) |
| 2002.09 | 175.8 | 109.6 | 94.6 (-4.1) |
| 2002.10 | 167.0 | 97.5 | (91.0 predicted, -3.6) |
| 2002.11 | 168.7 | 95.0 | (85.7 predicted, -5.3) |
| 2002.12 | 157.2 | 81.6 | (81.3 predicted, -4.4) |
| 2003.01 | 144.0 | 79.5 | (78.3 predicted, -3.0) |
| 2003.02 | 124.5 | 46.2 | (73.3 predicted, -5.0) |
| 2003.03 | 131.4 | 61.5 | (67.6 predicted, -5.7) |
| 2003.04 | 119.5 (1) | 48.9 (2) | (62.7 predicted, -4.9) |
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 (SEC/NOAA) sunspot number. The official international sunspot number is typically 25-45% less.
This report has been prepared by Jan Alvestad. It is based partly on my own observations and interpretations, and partly on data from sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.
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