Solar Terrestrial Activity Report

Last major update issued on May 31, 2012 at 03:50 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update May 3, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 3, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 3, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 3, 2012)]

[POES auroral activity level since October 2009 - updated May 26, 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on May 30. Solar wind speed at SOHO ranged between 382 and 526 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 111 (decreasing 3.0 over the last solar rotation). The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 8.9). Three hour interval K indices: 32222221 (planetary), 31122321 (Boulder).

The background x-ray flux is at the class B5 level.

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

Region 11490 [S13W23] decayed slowly and quietly.
Region 11492 [S13E05] decayed further and remained quiet.

Spotted active regions not numbered by NOAA/SWPC:
S1682 [S25E10] was quiet and stable.
S1692 [S13E33] was quiet and stable.
New region S1697 [S17E88] rotated partly into view.
New region S1698 [N14E88] rotated partly into view. At least C flares are possible.
New region S1699 [N14E77] rotated into view and appears to be developing.
New region S1700 [S21E55] emerged with a tiny spot.

Coronal mass ejections (CMEs)

May 29-30: No obviously Earth directed CMEs were observed in LASCO or STEREO imagery.
May 28: While there is little of interest in LASCO imagery, STEREO A and B imagery indicates a slow and long duration minor CME which could be Earth directed.

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 (CH520) will likely rotate into an Earth facing position on June 2-4.

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 May 31 and quiet on June 1-3.

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
11486	2012.05.17 2012.05.18	1			N17W92	0090	HSX				rotated out of view
11489	2012.05.21 2012.05.22				S30W58						location: S26W40
11488	2012.05.21 2012.05.22	2			N12W59	0010	BXO				spotless
S1674	2012.05.22				S21W50						plage
11490	2012.05.23 2012.05.24	22	24	12	S12W22	0180	DSI	DSI			beta-gamma
S1676	2012.05.23				S10W57						plage
11492	2012.05.24 2012.05.25	13	19	6	S13E03	0120	EAO	ESO			location: S13E05
S1682	2012.05.25		5	2	S25E10	0000		AXX
S1683	2012.05.25				N01W35						plage
S1684	2012.05.25				N21W46						plage
S1686	2012.05.26				S18W40						plage
S1687	2012.05.26				S28W34						plage
S1690	2012.05.26				S07W05						plage
S1691	2012.05.26				S26W12						plage
S1692	2012.05.27		3	1	S13E33	0000		BXO
S1693	2012.05.28				S22E20						plage
S1694	2012.05.28				N09E06						plage
S1695	2012.05.28				S15W57						plage
S1696	2012.05.29				S27W32						plage
S1697	2012.05.30		1	1	S17E88	0080		HSX
S1698	2012.05.30		2	1	N14E77	0020		HRX
S1699	2012.05.30		1	1	N14E88	0060		HSX
S1700	2012.05.30		1		S21E55	0000		AXX
Total spot count:		38	56	24
Sunspot number:		78	136	94	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		53	79	47	(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):		47	48	52	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.