Solar Terrestrial Activity Report

Last major update issued on July 21, 2012 at 04:50 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 unsettled on July 20. Solar wind speed at SOHO ranged between 350 and 463 km/s. A weak solar wind shock was observed at SOHO at 04:00 UTC and the associated disturbance caused quiet to unsettled conditions for the remainder of the day.

Solar flux measured at 20h UTC on 2.8 GHz was 92.3 (increasing 8.3 over the last solar rotation). The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.5). Three hour interval K indices: 23232323 (planetary), 24242322 (Boulder).

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

At midnight UTC the visible solar disk had 7 spotted active regions (in 2K resolution SDO images).

Region 11523 [S28W75] decayed quickly retaining only 2 spots and no penumbra.
Region 11524 [S13E10] decayed losing spots while a tiny spot emerged in the northern part of the dominant polarity area.
Region 11525 [S20E11] gained a few spots and rudimentary penumbra on a trailing spot.
New region 11526 [S18E65] rotated into view on July 19 and was numbered by SWPC the next day. The region decayed losing all traces of penumbra.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
S1806 [N16E25] lost the original spot and gained another spot further east.
New region S1808 [S25E19] emerged with a couple of tiny spots.
New region S1809 [S24W03] emerged inside CH524 with a small spot.

Coronal mass ejections (CMEs)

July 18 and 20: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
July 19: While the core of the full halo CME observed after the M7.7 event in AR 11520 won't reach Earth, there's at least a 50% chance of a flank impact on July 22.

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 (CH524) in the southern hemisphere was in an Earth facing position on July 19-20, but could be too far to the south to become geoeffective. 

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 poor to fair.

Forecast

The geomagnetic field is expected to be quiet to unsettled on July 21. CME effects on July 22 could cause quiet to active conditions with a chance of minor storm intervals. Additionally on July 22-23 there's a chance of weak effects from CH524.

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
11523	2012.07.11 2012.07.12	5	2	1	S28W74	0050	CAO	BXO			area: 0000
S1795	2012.07.13				N21W47						plage
S1797	2012.07.14				N09W32						plage
11524	2012.07.15 2012.07.17	3	1		S17E10	0010	BXO	AXX			area: 0000 location: S13E10
11525	2012.07.16 2012.07.17	4	13	7	S20E09	0040	DSO	DSO			area: 0080
S1801	2012.07.16				S15W41						plage
S1803	2012.07.17				N10W44						plage
S1804	2012.07.18				S33E08						plage
11526	2012.07.19 2012.07.20	3	4		S17E63	0010	BXO	BXO
S1806	2012.07.19		1		N16E25	0000		AXX			BXO in 4K image, only 1 spot visible in 2K resolution
S1807	2012.07.19				S01W01						plage
S1808	2012.07.20		2	1	S25E19	0000		AXX
S1809	2012.07.20		1	1	S24W03	0000		AXX
Total spot count:		15	24	10
Sunspot number:		55	94	50	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		25	29	15	(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):		33	33	28	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

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.