Solar Terrestrial Activity Report

Last update issued on September 14, 2003 at 03:55 UTC. 

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[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 8, 2003)]

Recent activity

The geomagnetic field was quiet to unsettled on September 13. Solar wind speed ranged between 450 and 597 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 96.1. The planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 12.1).
Three hour interval K indices: 33332222 (planetary), 33333211 (Boulder).

The background x-ray flux is at the class B2 level.

At midnight there were 2 spotted regions on the visible disk. Solar flare activity was low. A single C class event was recorded during the day.

Region 10456 decayed substantially during the latter half of the day and lost penumbra both in the leading and trailing parts. A magnetic delta structure developed early in the day but was gone by midnight. Flare: C2.2 at 07:42 UTC.
New region 10458 emerged in the southwest quadrant on September and was numbered by NOAA/SEC the next day.

Coronal mass ejections (CMEs)

September 11 and 13: No potentially geoeffective CMEs observed.

September 12: A full halo CME was observed early in the day. The CME was best defined over the south pole and was faint over the northern limbs. The source of this CME is likely the B8 event which occurred late on September 11 when a filament erupted just south of region S253. The CME is likely to reach Earth early on September 15.

Coronal holes

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

Small coronal holes (CH56 and CH58) near the equator were in a geoeffective position on September 13. A recurrent trans equatorial coronal hole (CH57) will rotate into a geoeffective position on September 15-17. This coronal hole has been developing during the last couple of days, particularly in the section located in the northern hemisphere.

Processed SOHO/EIT 284 image from 01:06 UTC on September 14. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to unsettled on September 14. High speed streams from coronal holes CH58, CH56 and CH57 will likely cause unsettled to active conditions on September 16-17 and unsettled to minor storm on September 18-20. The CME associated with a filament eruption late on September 11 could cause unsettled to active geomagnetic conditions early on September 15.

Long distance low frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is fair. Propagation along north-south paths is fair. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant station tonight: Radio Vibración (Venezuela), however, several other stations were noted including at least one US station].

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)
Coronal hole indicator CME indicator M and X class flare indicator

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.

Active solar regions (Recent map)

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
Location at midnight Area Classification Comment
10455 2003.09.06     S20W54     plage
10456 2003.09.08 20 19 S07W59 0240 DAI area was 0150
at midnight
10457 2003.09.09 1   S11W45
0010 HSX spotless,
SEC spot was
in region S253
10458 2003.09.13 6 8 S08W32 0020 CSO formerly region S254
classification was CAO
at midnight
S253 emerged on
    S12W39     plage
Total spot count: 27 27
SSN: 57 47

Monthly solar cycle data

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)
2003.09 103.0 (1) 25.6 (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.

[DX-Listeners' Club]