Last major update issued on September 18, 2005 at 04:10 UTC.
geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 3, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 3, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 3, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update September 14, 2005)]
The geomagnetic field was quiet to active on September 18. Solar wind speed ranged between 452 and 652 (all day average 525) km/sec under the influence of a weak high speed coronal hole stream.
Solar flux measured at 20h UTC on 2.8 GHz was 102.2. The planetary
index was 12 (STAR Ap - based on the mean of three hour interval ap
Three hour interval K indices: 13443221 (planetary), 23442231 (Boulder).
The background x-ray flux is at the class B4 level.
At midnight there were 4 spotted regions on the visible solar disk. The solar flare activity level was low. A total of 3 C class events was recorded during the day, all optically uncorrelated.
Region 10808 decayed further and lost penumbra on all spots outside of the main penumbra. The magnetic delta
structure in the main penumbra has weakened, however, an M class flare is still possible.
Region 10810 developed slowly and could produce at least C flares. There is some polarity intermixing in the trailing spot section.
Spotted regions not numbered by NOAA/SEC:
[S592] This region emerged in the northeast quadrant on September 18. Location at midnight: N12E00.
[S593] A new region emerged in the southeast quadrant on September 18. Location at midnight: S09E14.
September 16-18: No obvious fully or partly Earth directed CMEs were observed.
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
No obvious coronal holes are currently approaching Earth-facing positions.
Processed TRACE mosaic image on September 6, 2005. The darkest areas on the solar disk are likely coronal holes.
The geomagnetic field is expected to be quiet to unsettled on September 19-21 with the possibility of a few active intervals due to a high speed stream.
|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 on long distance northeast-southwest paths is fair. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and CPN Radio (Perú). On 1510 kHz Radio Belgrano (Argentina) was audible after 03:30 UTC, prior to that another Spanish language station had the best signal, possibly Radio Rancagua (Chile) based on the weak IDs. Several stations from Argentina and Uruguay were noted on other frequencies.
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|
classification was CKO at midnight, area 0280
classification was DAI at midnight, area 0230
|Total spot count:||30||36|
flux at Earth
|International sunspot number||Smoothed sunspot number|
cycle 23 sunspot max.
|2005.03||89.9||24.5||(33.5 predicted, -0.4)|
|2005.04||86.0||24.4||(32.2 predicted, -1.3)|
|2005.05||99.3||42.6||(29.9 predicted, -2.3)|
|2005.06||93.7||39.6||(28.7 predicted, -1.2)|
|2005.07||96.4||39.9||(27.7 predicted, -1.0)|
|2005.08||90.5||36.4||(25.8 predicted, -1.9)|
|2005.09||97.8 (1)||28.3 (2)||(24.2 predicted, -1.6)|
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% lower.
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.