Solar Terrestrial Activity Report

Last major update issued on April 14, 2005 at 04:15 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update April 4, 2005)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 4, 2005)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 4, 2005)]
[Historical solar and geomagnetic data charts 1954-2004 (last update February 1, 2005)]
[Archived reports (last update April 2, 2005)]

Recent activity

The geomagnetic field was quiet to minor storm on April 13. Solar wind speed ranged between 5+9 and 652 km/sec under the influence of a high speed stream from CH157.

Solar flux measured at 20h UTC on 2.8 GHz was 83.5. The planetary A index was 26 (STAR Ap - based on the mean of three hour interval ap indices: 26.5).
Three hour interval K indices: 24445544 (planetary), 24444544 (Boulder).

The background x-ray flux is at the class A6 level.

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was very low. No C class events were recorded during the day.

Region 10750 decayed slowly and quietly.
Region 10752 developed slowly and could produce further C flares.
New region 10753 emerged in the northeast quadrant on April 12 and was numbered the next day by SEC. Slow development was observed during the first half of the day, late in the day the region appeared to be in slow decay.

Coronal mass ejections (CMEs)

April 11-13: 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 recurrent coronal hole (CH157) in the northern hemisphere was in an earth facing position on April 9-10. A recurrent coronal hole (CH158) in the southern hemisphere will be in an Earth facing position on April 16.

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

Forecast

The geomagnetic field is expected to be quiet to active on April 14 as the high speed stream from CH157 subsides. Quiet to unsettled is likely on April 15-17.

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 poor. Propagation along long distance north-south paths is poor. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant station tonight: Radio Cristal del Uruguay. Several stations from North America were noted above 1400 kHz at 04h UTC, WWZN on 1510 kHz had a fair signal while the Georgia stations on 1630, 1670 and 1690 as well as WHKT on 1650 kHz all had weak signals.

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
10749 2005.04.03     S06W69     plage
10750 2005.04.05 5 5 S07W28 0060 CSO classification was DSO at midnight, area 0050
10752 2005.04.12 8 9 N01E56 0150 DAO area was 0110 at midnight
10753 2005.04.13 2 5 N12W06 0010 CSO formerly region S535
area was 0020 at midnight
S533 emerged on
2005.04.09
    N19W54     plage
Total spot count: 15 19  
SSN: 45 49  

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)
2004.02 107.0 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 43.8 (-1.7)
2004.06 97.4 43.2 41.6 (-2.2)
2004.07 119.1 51.1 40.2 (-1.4)
2004.08 109.6 40.9 39.2 (-1.0)
2004.09 103.1 27.7 37.5 (-1.7)
2004.10 105.9 48.0 (35.6 predicted, -1.9)
2004.11 113.2 43.5 (33.9 predicted, -1.7)
2004.12 94.5 17.9 (31.6 predicted, -2.3)
2005.01 102.2 31.3 (28.9 predicted, -2.7)
2005.02 97.2 29.1 (26.5 predicted, -2.4)
2005.03 89.9 24.8 (24.7 predicted, -1.8)
2005.04 85.3 (1) 17.9 (2) (22.9 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]