Solar Terrestrial Activity Report

Last major update issued on April 6, 2004 at 03:35 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-23 (last update April 2, 2004)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22 and 23 (last update April 2, 2004)]
[Graphical comparison of cycles 2, 10, 13, 17, 20 and 23 (last update April 2, 2004)]
[Historical solar and geomagnetic data charts 1954-2003 (last update January 16, 2004)]
[Archived reports (last update April 5, 2004)]

Recent activity

The geomagnetic field was quiet to minor storm on April 5. Solar wind speed ranged between 359 and 464 km/sec. A high speed stream from coronal hole CH88 increasingly dominated the solar wind after 11h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 108.7. The planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.5).
Three hour interval K indices: 10013454 (planetary), 23323554 (Boulder).

The background x-ray flux is at the class B1-B2 level.

At midnight there were 7 spotted regions on the visible disk. The solar flare activity level was moderate. A single M class event was recorded during the day.

Region 10581 rotated quietly to the southwest limb. 
Region 10582 rotated quietly to the northwest limb.
Region 10587 decayed slowly and quietly.
Region 10588 was quiet and stable.
New region 10589 rotated into view at the northeast limb on April 4 and was numbered by SEC the next day.

Spotted regions not numbered by NOAA/SEC:
[S380] This region emerged on April 3 just south of region 10588. The region developed moderately quickly on April 4 and slowly on April 5. The leading penumbra has a magnetic delta structure and another minor M class flare is possible. Location at midnight: S16E25. Flare: M1.7/1F at 05:55 UTC.  This event was associated with a weak type II radio sweep and a partial halo CME where most of the ejected material was observed off of the southeast limb.
[S383] This region emerged to the southeast of region S380 on April 5 and had a single small spot at midnight. Location at midnight: S19E30.

Coronal mass ejections (CMEs)

April 3-4: No fully or partly Earth directed CME observed.
April 5: A partial halo CME was observed after 06h UTC in LASCO images. The main ejecta was off of the southeast limb, however, a faint front was seen around most of the visible disk. A weak solar wind shock is possible on April 8. 

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

An elongated, recurrent trans equatorial coronal hole (CH88) will be in a geoeffective position on April 1-7. This coronal hole is best defined in the easternmost part.

Processed SOHO/EIT 284 image at 19:06 UTC on April 5. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be unsettled to minor storm on April 6, quiet to active on April 7 and unsettled to minor storm on April 8-9 due to a high speed stream from coronal hole CH88.

Long distance low and medium frequency (below 2 MHz) propagation along east-west paths over high and upper middle latitudes is very poor. Propagation along long distance north-south paths is poor. [Trans Atlantic propagation conditions are currently monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and CPN Radio (Perú). A weak signal from WWZN on 1510 was the only noted station from North America].

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.

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
Location at midnight Area Classification Comment
10581 2004.03.24 1 1 S04W83 0040 HSX  
10582 2004.03.25 1 1 N14W81 0120 HSX  
10585 2004.03.27     S15W66     plage
10587 2004.03.28 17 12 S14W31 0140 CAI  
10588 2004.04.01 12 1 S13E26
0170 DAO SEC spot count,
area and classification
include region S380
10589 2004.04.05 4 7 N10E54 0050 BXO formerly region S381
classification was CRO
at midnight, area 0020
S380 emerged on
  20 S16E25 0130 DAC beta-gamma-delta
split off from region
S382 emerged on
    N15W67     plage
S383 emerged on
  1 S19E30 0010 AXX  
Total spot count: 35 43
SSN: 85 113

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)
2003.03 131.4 61.1 74.0 (-4.3)
2003.04 126.4 60.0 70.1 (-3.9)
2003.05 115.7 55.2 67.6 (-2.5)
2003.06 129.3 77.4 65.0 (-2.6)
2003.07 127.7 83.3 61.8 (-3.2)
2003.08 122.1 72.7 60.0 (-1.8)
2003.09 112.2 48.7 59.5 (-0.5)
2003.10 151.7 65.5 (58.0 predicted, -1.5)
2003.11 140.8 67.3 (55.9 predicted, -2.1)
2003.12 114.9 46.5 (53.3 predicted, -2.6)
2004.01 114.1 37.2 (49.1 predicted, -4.2)
2004.02 107.0 46.0 (44.5 predicted, -4.6)
2004.03 112.0 48.9 (41.7 predicted, -2.8)
2004.04 109.2 (1) 14.0 (2) (39.6 predicted, -2.1)

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]