Solar Terrestrial Activity Report

Activity chart

Last major update issued on July 17, 2012 at 05:35 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 21-24 (last update June 2, 2012)] [Cycle 24 progress NEW]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update June 2, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update June 2, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update July 1, 2012)]

[POES auroral activity level since October 2009 - updated July 17, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was unsettled to major storm on July 16. Solar wind speed at SOHO ranged between 310 and 524 km/s under the influence of CME effects. The total field of the interplanetary magnetic field decreased slowly throughout the day. Bz was southwards until about 15h UTC, then briefly northwards before swinging slowly and more strongly southwards again towards the end of the day. Solar wind temperature has increased after 03h UTC on July 17, possibly due to the arrival of a high speed stream from CH523.

Solar flux measured at 17h UTC on 2.8 GHz was 137.9 (increasing 28.0 over the last solar rotation, the measurement at 20h UTC was flare enhanced). The Potsdam WDC planetary A index was 46 (STAR Ap - based on the mean of three hour interval ap indices: 46.1). Three hour interval K indices: 66554433 (planetary), 65443333 (Boulder).

The background x-ray flux is at the class C1 level.

At midnight UTC the visible solar disk had 11 spotted active regions (in 2K resolution SDO images).

Region 11519 [S16W83] was mostly quiet and stable as it rotated to the southwest limb.
Region 11520 [S17W60] decayed significantly losing spots and penumbral area.
Region 11521 [S21W77] decayed slowly and quietly.
Region 11522 [N12W63] decayed slowly and quietly.
Region 11523 [S29W27] increased the size of the leading penumbra and nearly lost all traces of penumbra on the trailing spots.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
[S12W63] decayed slowly and quietly barely retaining rudimentary penumbra.
S1790 [N12W14] was quiet and stable.
S1798 [S15E77] decayed slightly and was quiet.
New region S1800 [S19E66] emerged near AR S1798. This is a quickly emerging and interesting region. Early on July 17 a magnetic delta structure has developed and M flares are possible. This region was the source of the only interesting activity of the day producing a long duration C7.5 event peaking at 20:03 UTC. A CME was observed off the southeast limb just after the peak of the event. SWPC claims AR 11520 was the source of this event, another interpreter thinks it was AR 11519, and while there certainly were simultaneous flare activity in both regions which may have contributed to the increase in x-ray levels, STEREO-B imagery of AR S1800 matches the onset and peak of the LDE. Most LDEs are anyway associated with CMEs and the only CME observed was off the northern part of the southeast limb.
New region S1801 [S13E07] emerged with a tiny spot.
New region S1802 [S10W51] emerged with a single spot. 

Coronal mass ejections (CMEs)

July 14-16: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.

Coronal holes

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

A coronal hole (CH523) in the northern hemisphere rotated across the central meridian on July 14. A coronal hole (CH524) in the southern hemisphere will likely rotate into an Earth facing position on July 18. 

Coronal hole map

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, 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 this method, the extent and intensity of both CHs are consistent with other data sources.


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


The geomagnetic field is expected to be quiet to active on July 17 due to lingering CME effects and effects from CH523. Quiet to unsettled is likely on July 18-19.

Coronal holes (1) Coronal mass ejection (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
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
2K 1K
11519 2012.07.04 12 4 3 S17W81 0090 DAO DSO  
11520 2012.07.05
12 25 17 S16W58 0430 FKC DKI

location: S17W60

area: 0600

SWPC count, location, classification and area probably includes ARs S1776 and S1777

S1776 2012.07.05       S16W68         plage
S1777 2012.07.05   1 1 S12W63 0010   HRX  
11521 2012.07.07
8 5 4 S22W71 0220 EAO DSO location: S21W77

area: 0300

11522 2012.07.07
4 5 3 N11W76 0060 DSO DSO location: N12W78
S1790 2012.07.10   4 1 N12W14 0000   BXO  
S1791 2012.07.10       N12W37           plage
11523 2012.07.11
3 13 8 S28W21 0040 DAO DAO  
S1795 2012.07.13       N21E05           plage
S1796 2012.07.13       S28W55           plage
S1797 2012.07.14       N09E20           plage
S1798 2012.07.15   2 1 S15E64 0030   HRX  
S1799 2012.07.15       S15W34         plage
S1800 2012.07.16   4 3 S19E66 0020   DRO   beta-gamma
S1801 2012.07.16   1 1 S13E07 0000   AXX    
S1802 2012.07.16   1 1 S10W51 0000   AXX    
Total spot count: 39 65 43  
Sunspot number: 89 175 153  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 69 104 82  (Sum of total spot count + classification weighting for each AR. Classification weighting: X=0, R=3, A/S=5, H/K=10)
Relative sunspot number (Wolf number): 53 61 84 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
2011.04 112.6 54.4 41.8 (+4.9) 8.83
2011.05 95.8 41.6 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.9 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 59.9 (+0.4) 8.28
2011.11 153.5 96.7 61.1 (+1.2) 5.55
2011.12 141.3 73.0 63.4 (+2.3) 3.78
2012.01 132.5 58.3 (65.0 projected, +1.6) 7.15
2012.02 106.5 33.1 (66.5 projected, +1.5) 8.81
2012.03 114.7 64.2 (67.2 projected, +0.7) 16.08
2012.04 113.0 55.2 (66.5 projected, -0.7) 10.10
2012.05 121.5 69.0 (64.8 projected, -1.7) 7.06
2012.06 119.6 64.5 (64.0 projected, -0.8) 10.08
2012.07 153.8 (1) 64.5 (2A) / 124.9 (2B) (65.0 projected, +1.0) (23.10)

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 quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC 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.