Solar Terrestrial Activity Report

Last major update issued on June 4, 2005 at 05:10 UTC.

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

Recent activity

The geomagnetic field was quiet to unsettled on June 3. Solar wind speed ranged between 379 and 449 km/sec under the influence of a weak low speed stream from CH168.

Solar flux measured at 20h UTC on 2.8 GHz was 95.3. The planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.5).
Three hour interval K indices: 23322222 (planetary), 23323322 (Boulder).

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

At midnight there were 3 spotted regions on the visible solar disk. The solar flare activity level was moderate. A total of 2 C and 2 M class events was recorded during the day. A long duration M1.0 event peaked at 12:26 UTC. Its source was in a region just behind the northeast limb and it was associated with a large, wide and fast full halo CME.

Region 10772 developed in the trailing spot section. This part of the region is complex with at least one magnetic delta structure. Further M class activity is likely. Flares: C3.1 long duration event peaking at 02:24, impulsive M1.3/1B (associated with a weak type II radio sweep) at 04:11 and C6.5 at 23:55 UTC. The C6 event was associated with weak type II and IV radio sweeps.
Region 10773 did not change substantially, however, the trailing penumbra appears to be splitting into two penumbrae.

Spotted region not numbered by NOAA/SEC:
[S553] This region emerged in the northeast quadrant on June 3. Interestingly this region has reversed polarities. Location at midnight: N05E08.

Coronal mass ejections (CMEs)

June 1-3: No obvious fully or partly potentially geoeffective 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 (CH169) in the northern hemisphere with a trans equatorial extension was in an Earth facing position on June 1-3.

Processed SOHO/EIT 284 image at 01:06 UTC on June 4. The darkest areas on the solar disk are likely coronal holes.


The geomagnetic field is expected to be quiet to minor storm on June 4-6 due to a high speed stream from CH169.

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.


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 good. Trans Atlantic propagation conditions are normally monitored every night on 1470 kHz. Dominant stations tonight: Radio Cristal del Uruguay and Radio Rafaela (Argentina). Lots of stations from Argentina, Uruguay and eastern Brazil were observed on other frequencies, particularly during the hour after local sunrise.

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
10769 2005.05.28 1   S06E09 0000 AXX spotless
10770 2005.05.29     N12W65     plage
10771 2005.05.30     N23W85     plage
10772 2005.05.31 18 18 S17E09 0120 DAI beta-gamma-delta
area was 0150 at midnight, location S18E07
10773 2005.06.01 6 5 S13E50 0140 DAO area was 0110 at midnight, location S13E47
S553 2005.06.03   4 N05E07 0010 BXO  
Total spot count: 25 27  
SSN: 55 57  

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)
2004.04 101.2 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 35.9 (-1.6)
2004.11 113.2 43.5 35.3 (-0.6)
2004.12 94.5 17.9 (34.8 predicted, -0.5)
2005.01 102.2 31.3 (32.8 predicted, -2.0)
2005.02 97.2 29.1 (30.4 predicted, -2.4)
2005.03 89.9 24.8 (28.8 predicted, -1.6)
2005.04 86.0 24.4 (26.9 predicted, -1.9)
2005.05 99.3 42.6 (24.3 predicted, -2.6)
2005.06 95.2 (1) 7.3 (2) (22.8 predicted, -1.5)

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]