Solar Terrestrial Activity Report

Activity chart

Last major update issued on July 31, 2012 at 05:30 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 quiet to active on July 30. Solar wind speed at SOHO ranged between 322 and 459 km/s under the influence of a low speed stream from CH525.

Solar flux measured at 20h UTC on 2.8 GHz was 136.0 (decreasing 9.8 over the last solar rotation). The Potsdam WDC planetary A index was 15 (STAR Ap - based on the mean of three hour interval ap indices: 14.8). Three hour interval K indices: 223334422 (planetary), 13433423 (Boulder).

The background x-ray flux is at the class B6 level.

At midnight UTC the visible solar disk had 8 spotted active regions (in 2K resolution SDO images).

Region 11528 [N16W28] developed slowly and displayed a lot of activity in SDO/AIA imagery. Further C flares are possible.
Region 11529 [S11W22] was quiet and stable.
Region 11530 [S19W12] was quiet and stable.
Region 11532 [S21E18] lost the magnetic delta structure in the central penumbra after the M class event. There's still a minor delta in the large leading penumbra. Further M class flaring is possible. Flares: C8.8 at 14:03, M1.1 at 15:48 UTC.
Region 11533 [S29W22] was quiet and stable.
Region 11534 [N21E27] added a spot in the northern section.
New region 11535 [N18E64] rotated into view on July 29 and was numbered the next day by SWPC.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
New region S1832 [N22E04] emerged with a tiny spot.

A region at the southeast limb has rotated partly into view early on July 31 with several spots. This region produced a C6.3 flare at 23:58 UTC. Minor M class flaring is possible.

Coronal mass ejections (CMEs)

July 29-30: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
July 28: The partial halo CME produced by the M6 event in AR 11532 could have a minor Earth directed component.

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 recurrent trans equatorial coronal hole (CH525) was in an Earth facing position on July 25-27.

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.

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 unsettled on July 31 due to effects from CH525. Weak effects from the July 28 CME are possible on August 1.

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
detected
Spot count Location at midnight Area Classification SDO / HMI 4K continuum
image with magnetic polarity overlay
Comment
SWPC STAR SDO SWPC STAR Current Previous
2K 1K
11526 2012.07.19
2012.07.20
      S17W73         plage

location: S18W61

11528 2012.07.22
2012.07.23
2 7 4 N17W28 0030 CSO CSO

 

11527 2012.07.22
2012.07.23
      N27W31           plage

location: N25W22

11529 2012.07.22
2012.07.23
2 3 2 S11W23 0060 HSX HSX  
11530 2012.07.23
2012.07.24
1 27 7 S18W13 0150 HSX CHO

area: 0260

S1819 2012.07.24       N21W46           plage
S1820 2012.07.24       N17W57           plage
11532 2012.07.25
2012.07.26
14 55 23 S19E14 0350 DKC FKI beta-gamma-delta

area: 0750

location: S21E18

11533 2012.07.26
2012.07.27
3 10 5 S28W21 0010 BXO BXO  
11534 2012.07.27
2012.07.28
  5 1 N17E27 0000   BXO location: N21E27
S1826 2012.07.27       S25W53           plage
S1827 2012.07.28       N17W14           plage
S1828 2012.07.28       S22W15         merged with AR 11530
S1829 2012.07.28       S02W41           plage
11535 2012.07.29
2012.07.30
7 18 8 N18E64 0100 DAI DSI area: 0350
11536 2012.07.30 7     S23E26 0100 DAO       part of AR 11532
S1832 2012.07.30   1 1 N22E04 0000   AXX    
Total spot count: 36 126 51  
Sunspot number: 106 206 131  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 71 161 86  (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): 64 72 72 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 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
(3)
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
2012.07 133.7 (1) 95.8 (2A) / 99.0 (2B) (65.0 projected, +1.0) (14.68)

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.