Solar Terrestrial Activity Report

Last major update issued on May 4, 2012 at 04:35 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 1, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on May 3. Solar wind speed at SOHO ranged between 272 and 324 km/s. A weak solar wind shock was observed at 00:59 UTC at SOHO, likely the arrival of the CME observed late on April 28.

Solar flux measured at 20h UTC on 2.8 GHz was 114.0 (increasing 16.6 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: 8.8). Three hour interval K indices: 32222113 (planetary), 32222223 (Boulder).

The background x-ray flux is at the class B4 level.

At midnight UTC the visible solar disk had 10 spotted active regions (in 2K resolution SDO images).

Region 11469 [S20W53] decayed slowly and quietly.
Region 11470 [S15W03] developed slowly and was quiet.
Region 11471 [S22E06] displayed no significant changes and was quiet.
Region 11472 [S28W11] decayed slowly and quietly.
Region 11473 [S18W67] decayed slowly and quietly.
Region 11474 [N15E55] was quiet and stable.
New region 11475 [N05E66] rotated into view at the northeast limb on May 2 and was numbered by SWPC the next day. The region was quiet.

Spotted active regions not numbered by NOAA/SWPC:
S1611 [S26W48] decayed slightly again. Apparantly SWPC considers the region to be part of AR 11469.
S1621 [N13W15] decayed slowly and quietly.
New region S1627 [N05W22] emerged with a tiny spot.

An active region just behind the northeast limb was the source of most of the flare activity recorded during the day. The largest event was C2.3 at 16:56 UTC (wrongly attributed to AR 11475 by SWPC).

Coronal mass ejections (CMEs)

May 1-3: 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 recurrent trans equatorial coronal hole (CH515) will rotate into an Earth facing position on May 5-7.

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 to fair. Propagation on long distance northeast-southwest paths is poor to fair.

Forecast

The geomagnetic field is expected to be quiet on May 4-7. On May 8-10 a high speed stream from CH515 will likely cause quiet to minor storm conditions with a chance of major storm intervals.

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
11469	2012.04.23 2012.04.24	10	7	2	S26W51	0100	CAO	BXO			location: S20W53 area: 0010 SWPC has S1611 and 11469 as one region
11467	2012.04.24				N13W49						plage location: N15W44
S1611	2012.04.25		14	7	S26W48	0100		DAO
11471	2012.04.27 2012.04.28	7	15	7	S19E02	0300	CKO	CKO			location: S22E06
11470	2012.04.27 2012.04.28	10	10	4	S15W07	0010	BXO	DSO			location: S15W03 area:0080
S1616	2012.04.27				N04W56						plage
S1618	2012.04.28				N21E01						plage
11472	2012.04.29	3	6	3	S28W12	0010	BXO	BXO
S1619	2012.04.29				S13W33						plage
S1621	2012.04.30		1		N13W15	0000		AXX
11473	2012.05.01	5	6	3	S21W68	0060	CSO	CSO			location: S18W67
11474	2012.05.01 2012.05.02	1	1	1	N16E52	0020	HRX	HRX			location: N15E55
S1623	2012.05.01				S41W46						plage
11475	2012.05.02	1	1	1	N05E61	0040	HSX	HSX
S1626	2012.05.02				S28E03						plage
S1627	2012.05.03		1		N05W22	0000		AXX
Total spot count:		37	62	28
Sunspot number:		107	162	108	(total spot count + 10 * number of spotted regions)
Weighted penumbral SN:		65	95	61	(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	57	59	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.