Last update issued on September 18, 2003 at 03:20 UTC.
[Solar and geomagnetic data
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[Solar cycles 21-23 (last update
September 1, 2003)]
[Solar cycles 1-20]
[Graphical comparison of cycles
21, 22 and 23 (last update September 1, 2003)]
[Graphical comparison of cycles
2, 10, 13, 17, 20 and 23 (last update September 1, 2003)]
[Historical solar and geomagnetic data
charts 1954-2003 (last update July 23, 2003)]
[Archived reports (last update
September 16, 2003)]
The geomagnetic field was active to severe storm on September 17. Solar wind speed ranged between 484 and 895 km/sec under the influence of a strong high speed stream from coronal hole CH57.
Solar flux measured at 20h UTC on 2.8 GHz was 105.9. The planetary A index
was 61 (STAR Ap - based on the mean of three hour interval ap indices:
61.4).
Three hour interval K indices: 55577445 (planetary), 55555545
(Boulder).
The background x-ray flux is at the class B2 level.
At midnight there were 5 spotted regions on the visible disk. Solar flare activity was low. A total of 3 C class events was recorded during the day. A C1.9 event peaking at 01:42 UTC and a C2.4 long duration event peaking at 04:06 UTC had their origin behind the southwest limb.
Region 10459 lost the leader spots while the largest penumbra
increased its area considerably. Flare: C2.7
at 05:15 UTC.
Region 10460 was quiet and stable
Region 10461
developed further and more than doubled the penumbral area.
Region
10462 decayed and could become spotless today.
New region 10463
rotated into view at the northeast limb on September 16 and was numbered by SEC
the next day.
September 15-17: No potentially 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 recurrent trans equatorial coronal hole (CH57) was in a geoeffective position on September 14-17. An elongated coronal hole (CH59) in the southern hemisphere could rotate into a geoeffective position on September 18-20. CH59 developed significantly on September 17 and added a northward extension in the easternmost part.
Processed SOHO/EIT 284 image from 01:06 UTC on September 18. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be unsettled to minor storm until September 20 due to a high speed stream from coronal hole CH57. A high speed stream from coronal hole CH59 will likely cause unsettled to active conditions on September 21-23.
Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is useless. Propagation along north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay (no other stations heard on this frequency)].
| 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 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.
| Solar region | Date numbered | SEC spot count |
STAR spot count |
Location at midnight | Area | Classification | Comment |
|---|---|---|---|---|---|---|---|
| 10458 | 2003.09.13 | S10W86 | plage | ||||
| 10459 | 2003.09.14 | 12 | 14 | S11W01 | 0050 | DSO | classification was DAO at midnight, area 0070 |
| 10460 | 2003.09.15 | 2 | 2 | N17E51 | 0040 | CSO | classification was DSO at midnight |
| 10461 | 2003.09.16 | 12 | 17 | N12W52 | 0140 | DAO | classification was DAI at midnight, area 0260 |
| 10462 | 2003.09.16 | 6 | 2 | S10W43 | 0030 | CSO | classification was CRO at midnight, area 0020 |
| 10463 | 2003.09.17 | 1 | 1 | N09E74 | 0090 | HAX | formerly region S257 |
| Total spot count: | 33 | 36 | |||||
| SSN: | 83 | 86 | |||||
| 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) |
| 2002.07 | 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 | 90.5 (-4.1) |
| 2002.11 | 168.7 | 95.5 | 85.2 (-5.3) |
| 2002.12 | 157.2 | 80.8 | 82.0 (-3.2) |
| 2003.01 | 144.0 | 79.7 | 81.0 (-1.0) |
| 2003.02 | 124.5 | 46.0 | 78.5 (-2.5) |
| 2003.03 | 131.4 | 61.1 | (74.2 predicted, -4.3) |
| 2003.04 | 126.4 | 60.0 | (69.3 predicted, -4.9) |
| 2003.05 | 115.7 | 55.2 | (64.4 predicted, -4.9) |
| 2003.06 | 129.3 | 77.4 | (60.4 predicted, -4.0) |
| 2003.07 | 127.7 | 85.0 | (56.9 predicted, -3.5) |
| 2003.08 | 122.1 | 72.7 | (53.9 predicted, -3.0) |
| 2003.09 | 102.1 (1) | 35.5 (2) | (51.9 predicted, -2.0) |
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 sources noted in solar links. All time references are to the UTC day. Comments and suggestions are always welcome.
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