Solar Terrestrial Activity Report

Last major update issued on April 1, 2005 at 04:05 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update March 3, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update March 3, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update March 3, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update March 16, 2005)]

Recent activity

The geomagnetic field was quiet to unsettled on March 31. Solar wind speed ranged between 401 and 474 km/sec.

Solar flux measured at 20h UTC on 2.8 GHz was 76.7. The planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 9.0).
Three hour interval K indices: 13321232 (planetary), 13212223 (Boulder).

The background x-ray flux is at the class A2 level.

At midnight there was 1 spotted region on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

New region 10748 rotated into view at the northeast limb on March 30 and was numbered the next day by SEC.

Coronal mass ejections (CMEs)

March 29-31: No obvious fully or partly Earth directed CMEs were observed.

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 large recurrent coronal hole (CH154) in the northern hemisphere will be in an Earth facing position on March 30-April 2.

Processed SOHO/EIT 284 image at 01:06 UTC on April 1. The darkest areas on the solar disk are likely coronal holes.

Forecast

The geomagnetic field is expected to be mostly quiet on April 1. Unsettled to minor storm conditions are possible on April 2-5 due to a high speed stream from CH154.

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 fair. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Vibración (Venezuela), WLAM Lewiston ME and WWNN Boca Raton FL. The best trans Atlantic signals were from KNR (Greenland) on 650 kHz, the Newfoundland stations on 590, 620, 640, 710, 750 and 930 kHz as well as WWZN 1510, WBZ 1030 kHz.

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
10745 2005.03.21     N12W81     plage
10747 2005.03.31 1   S07E23 0010 HSX spotless
10748 2005.03.31 1 1 N09E59 0020 HSX formerly region S531
S527 emerged on
2005.03.24
    N03W36     plage
S528 emerged on
2005.03.28
    N13W83     plage
S529 emerged on
2005.03.28
    S08W02     plage
S530 emerged on
2005.03.28
    N07E04     plage
Total spot count: 2 1  
SSN: 22 11  

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)
2004.01 114.1 37.3 52.0 (-2.8)
2004.02 107.0 45.8 49.3 (-2.7)
2004.03 112.0 49.1 47.1 (-2.2)
2004.04 101.2 39.3 45.5 (-1.6)
2004.05 99.8 41.5 43.9 (-1.6)
2004.06 97.4 43.2 41.7 (-2.2)
2004.07 119.1 51.0 40.3 (-1.4)
2004.08 109.6 40.9 39.2 (-1.1)
2004.09 103.1 27.7 (37.4 predicted, -1.8)
2004.10 105.9 48.4 (35.2 predicted, -2.2)
2004.11 113.2 43.7 (33.3 predicted, -1.9)
2004.12 94.5 17.9 (31.0 predicted, -2.3)
2005.01 102.2 31.3 (28.3 predicted, -2.7)
2005.02 97.2 29.1 (25.9 predicted, -2.4)
2005.03 89.9 (1) 41.0 (2) (24.1 predicted, -1.8)

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]