Solar Terrestrial Activity Report

Last major update issued on July 18, 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 minor storm on July 17. Solar wind speed at SOHO ranged between 351 and 565 km/s. A high speed stream from CH523 became the dominant solar wind source after 03h UTC.

Solar flux measured at 20h UTC on 2.8 GHz was 127.5 (increasing 23.8 over the last solar rotation). The Potsdam WDC planetary A index was 24 (STAR Ap - based on the mean of three hour interval ap indices: 23.8). Three hour interval K indices: 55522223 (planetary), 33522312 (Boulder).

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

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11520 [S17W73] decayed further and has simplified considerably magnetically.
Region 11523 [S29W39] decayed slowly and quietly.
New region 11524 [S15E50] rotated into view on July 15 and was numbered by SWPC 2 days later.
New region 11525 [S20E52] emerged on July 16 and got a number from SWPC the next day. The region simplified in the southern part, however, polarities are intermixed with opposite polarity spots closely spaced in the northern spot section. C flares are possible, as is a minor M class flare.

Spotted active regions not numbered or interpreted differently by NOAA/SWPC:
S1801 [S15W02] was quiet and stable.
New region S1803 [N10W05] emerged with a tiny spot.

The most interesting event of the day was a very long duration event caused by a filament eruption near AR 11520. The event peaked at the M1.7 level at 17:15 UTC and was associated with a bright CME off the southwest limb.

Coronal mass ejections (CMEs)

July 15-17: 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. 

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 very 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 18 due to effects from CH523 and quiet on July 19-20.

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
11520	2012.07.05 2012.07.06	8	7	6	S17W75	0590	EKO	CKO
11521	2012.07.07 2012.07.09	4			S19W85	0140	DSO				location: S21W90 rotated out of view
11522	2012.07.07 2012.07.12	3			N12W90	0060	CAO				rotated out of view
S1790	2012.07.10				N12W27						plage
S1791	2012.07.10				N12W50						plage
11523	2012.07.11 2012.07.12	4	13	7	S28W36	0060	CSO	DAO			location: S29W39
S1795	2012.07.13				N21W08						plage
S1797	2012.07.14				N09E07						plage
11524	2012.07.15 2012.07.17	5	2	1	S15E50	0030	CSO	HAX
S1799	2012.07.15				S15W47						plage
11525	2012.07.16 2012.07.17	3	17	7	S22E51	0030	CSO	DAI			beta-gamma location: S20E52 area: 0070
S1801	2012.07.16		2		S15W02	0000		BXO
S1802	2012.07.16				S10W64						plage
S1803	2012.07.17		1		N10W05	0000		AXX
Total spot count:		27	42	21
Sunspot number:		87	102	61	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		62	67	46	(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):		52	36	34	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.