Solar Terrestrial Activity Report

Last major update issued on July 20, 2011 at 05:55 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update July 2, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update July 2, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update July 2, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update July 2, 2011)]

[POES auroral activity level charts since October 2009 - updated July 19, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2110 [May-June 2011] - 2111 [June-July 2011] NEW
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to minor storm on July 19. Solar wind speed ranged between 402 and 711 km/s under the influence of a high speed stream from CH466.

Solar flux measured at 20h UTC on 2.8 GHz was 100.3 (increasing 7.4 over the last solar rotation). The planetary A index was 18 (STAR Ap - based on the mean of three hour interval ap indices: 17.8). Three hour interval K indices: 11233544 (planetary), 12233433 (Boulder).

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

At midnight UTC the visible solar disk had 10 spotted regions.

Region 11250 was quiet and stable. The region will rotate to the southwest limb today.
Region 11251 was quiet and stable.
Region 11252 was quiet and stable.
Region 11254 developed slowly and could produce C flares.
Region 11256 decayed slowly and quietly.
Region 11257 decayed slowly and was quiet. The region is rotating over the northwest limb.
Region 11258 decayed slowly and quietly.
Region 11259 developed slowly and was quiet.

Spotted regions not numbered by NOAA/SWPC:
[S1124] emerged in the southwest quadrant on July 18. Location at midnight: S33W69
[S1125] emerged in the southeast quadrant on July 19. Location at midnight: S17E12

Coronal mass ejections (CMEs)

July 17-19: No obviously earth directed CMEs were observed.

Coronal holes

Coronal hole history (since late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A large trans equatorial coronal hole (CH466) was Earth facing on July 14-18.

The above coronal hole map is based on a new method where coronal holes are detected automatically. The method may need some fine tuning, however, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using the new method, the extent and intensity of both holes are consistent with other data sources.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair to good.

Forecast

The geomagnetic field is expected to be quiet to active on July 2021 with a chance of minor storm intervals due to a high speed stream from CH466. Quiet conditions are likely on July 22-23.

Coronal holes (1) Coronal mass ejections (2) M and X class flares (3)



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) Effects from a CME are likely to be observed at 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

(Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) is positive.

Data for all numbered solar regions according to the Solar Region Summary provided by NOAA/SWPC. 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 SWPC or where SWPC has observed no spots. SWPC active region numbers in the table below and in the active region map above are the historic SWPC/USAF numbers.

Active region Date numbered
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
11250 2011.07.10 1 1 S26W74 0100 HSX HSX area: 0030

location: S25W76

11251 2011.07.10
2011.07.11
1 3 N17W35 0090 HSX CSO

location: N17W33

11257 2011.07.10
2011.07.17
3 3 N20W83 0240 DSO CSO

location: N21W84

S1112 2011.07.11     N06W57           plage
11255 2011.07.12
2011.07.14
    N18W20         plage
11252 2011.07.12
2011.07.13
  1 N25W08 0000   AXX

 

11254 2011.07.13
2011.07.14
12 36 S22W04 0080 DSO DAI

location: S23W03

area: 0150

11256 2011.07.14
2011.07.15
2 4 N10W21 0010 BXO AXX

area: 0000

11258 2011.07.15
2011.07.18
4 5 N12W51 0040 CSO BXO location: N13W52

area: 0000

S1121 2011.07.16     N18E05           plage
11259 2011.07.17
2011.07.18
3 13 N25E56 0100 CSO CSI

location: N24E57

S1123 2011.07.17     N10E15         plage
S1124 2011.07.18   1 S33W69 0000   AXX  
S1125 2011.07.19   3 S17E12 0000   AXX    
Total spot count: 26 70  
Sunspot number: 96 170  (raw spot count + 10 * number of spotted regions)
Classification adjusted SN: 56 95  (Sum of raw spot count + classification adjustment for each AR. Classification adjustment: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 58 56  k * (sunspot number). k = 0.6 for SWPC. k = 0.33 for STAR SDO

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
3.25
2010.04 75.9 8.0 14.0 (+1.7) 10.22 / 10.24
2010.05 73.8 8.7 15.5 (+1.5) 9.18 / 8.15
2010.06 72.5 13.6 16.4 (+0.9) 8.17 / 6.85
2010.07 79.8 16.1 16.7 (+0.3) 6.31 / 5.15
2010.08 79.2 19.6 17.4 (+0.7) 8.49 / 7.77
2010.09 81.1 25.2 19.6 (+2.2) 5.33 / 5.45
2010.10 81.6 23.5 23.2 (+3.6) 6.07 / 6.27
2010.11 82.5 21.5 26.5 (+3.3) 4.80 / 5.50
2010.12 84.2 14.4 28.8 (+2.3) 3.41 / 4.35
2011.01 83.6 19.1 (30.6 predicted, +1.8) 4.32 / 5.51
2011.02 94.6 29.4 (32.6 predicted, +2.0) 5.41 / 6.44
2011.03 115.0 56.2 (35.2 predicted, +2.6) 7.79 / 8.18
2011.04 112.6 54.4 (38.1 predicted, +2.9) 9.71 / 8.83
2011.05 95.8 41.6 (41.4 predicted, +3.3) 9.18 / 8.94
2011.06 95.8 37.0 (45.2 predicted, +3.8) 8.96
2011.07 90.8 (1) 41.2 (2A) / 67.3 (2B) (49.4 predicted, +4.1) (9.39)

1) Running average based on the daily 20:00 UTC observed solar flux value at 2800 MHz.
2A) Current impact on the monthly sunspot number based on the Boulder (NOAA/SWPC) sunspot number (accumulated daily sunspots / month days). The official SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the preliminary daily SWPC ap indices. Values in red are based on the official NGDC ap indices.

This report has been prepared by Jan Alvestad. It is based on analysis of data from whatever sources are available at the time the report is prepared. All time references are to the UTC day. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.