Solar Terrestrial Activity Report

Last major update issued on September 11, 2004 at 02:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update September 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update September 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update September 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2004 (last update August 28, 2004)]
[Archived reports (last update September 11, 2004)]

Recent activity

The geomagnetic field was quiet on September 10. Solar wind speed ranged between 271 and 445 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 130.0. The planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 6.3).
Three hour interval K indices: 21122222 (planetary), 10122211 (Boulder).

The background x-ray flux is at the class B5 level.

At midnight there were 4 spotted regions on the visible disk. The solar flare activity level was low. A total of 7 C class events was recorded during the day.

Region 10667 decayed slowly and quietly
Region 10669 decayed fairly quickly and was quiet.
Region 10671 developed slowly and rotated partly out of view at the southwest limb.
Region 10672 was mostly unchanged. There is a negative polarity area in the south, then a strong positive polarity area in the middle and a weak negative polarity area in the north. There is lots of hot plage inside the region. A minor M class flare is possible Flares: C1.0 at 02:07, C1.8 at 07:25, C2.1 at 12:56, C1.0 at 15:05, C6.9 at 16:13, C1.7 long duration event peaking at 19:41 and a C1.6 event which began at 23:57 and peaked at 00:06 UTC the next day.

Coronal mass ejections (CMEs)

September 8-10: No obviously Earth directed CMEs were observed. A CME was observed above the central east limb after the C3 event on September 9.

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

A coronal hole (CH113) in the southern hemisphere could rotate into a marginally geoeffective position on September 11-12.

Processed SOHO/EIT 284 image at 19:06 UTC on September 10. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be quiet on September 11-13.

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. 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.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is good. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are monitored every night on 1470 kHz. Dominant stations tonight: WLAM Lewiston ME and Radio Vibración (Venezuela). While a few stations from Colombia (i.e. RCN Barranquilla on 760 kHz), Venezuela and the Caribbean (i.e. Radio Visión Cristiana on 530 and WKAQ Radio Reloj on 580 kHz) most of the stations I heard were from Canada and the USA. The Newfoundland stations in particular had excellent signals.

Propagation conditions could improve further during the next few days.

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. 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
10667 2004.09.01 5 4 S11W45 0250 HHX classification was CAO
at midnight, area 0220
10669 2004.09.05 18 10 S06W38 0130 DSI classification was DAO
at midnight, area 0080
10671 2004.09.06 11 5 S09W81 0370 DKI classification was HKX
at midnight
10672 2004.09.09 13 19 N05E60 0260 DAI area was 0160
at midnight
S451 emerged on
2004.09.08
    S06E27     plage
Total spot count: 47 38
SSN: 87 78

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)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 60.1 (-1.7)
2003.09 112.2 48.7 59.6 (-0.5)
2003.10 151.7 65.5 58.2 (-1.4)
2003.11 140.8 67.3 56.8 (-1.4)
2003.12 114.9 46.5 54.8 (-2.0)
2004.01 114.1 37.7 52.0 (-2.8)
2004.02 107.0 45.8 49.3 (-2.7)
2004.03 112.0 49.1 (47.0 predicted, -2.3)
2004.04 101.2 39.3 (44.8 predicted, -2.2)
2004.05 99.8 41.5 (41.5 predicted, -3.3)
2004.06 97.4 43.2 (38.6 predicted, -2.9)
2004.07 119.1 51.0 (36.8 predicted, -1.8)
2004.08 109.6 40.9 (35.4 predicted, -1.4)
2004.09 109.4 (1) 19.3 (2) (34.2 predicted, -1.2)

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.


[DX-Listeners' Club]