Solar Terrestrial Activity Report

Last major update issued on May 4, 2011 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 May 1, 2011)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update May 1, 2011)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update May 1, 2011)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update May 1, 2011)]

[POES auroral activity level charts since October 2009 - updated May 2, 2011]
Annotated geomagnetic activity charts - Carrington rotation 2107 [Feb.-March 2011] - 2108 [March-April 2011] NEW

Recent activity

The geomagnetic field was quiet to active on May 3. Solar wind speed ranged between 555 and 669 km/s under the diminishing influence of a high speed stream from CH446.

Solar flux measured at 20h UTC on 2.8 GHz was 107.0 (decreasing 10.1 over the last solar rotation). The planetary A index was 13 (STAR Ap - based on the mean of three hour interval ap indices: 12.6). Three hour interval K indices: 44222322 (planetary), 43232332 (Boulder).

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

At midnight UTC the visible solar disk had 9 spotted regions.

Region 11200 decayed slowly and quietly.
Region 11203 was quiet and stable.
Region 11204 was mostly quiet and stable. Flare: C1.3 at 10:52 UTC
Region 11205 decayed slowly and quietly.
New region 11206 was first observed with spots on April 29 and numbered by NOAA/SWPC on May 3. Slow decay was observed on May 3.

Spotted regions not numbered by NOAA/SWPC:
[S988] emerged in the northwest quadrant on May 2. Location at midnight: N12W46
[S989] emerged in the northeast quadrant on May 3. Location at midnight: N21E46
[S990] emerged in the northeast quadrant on May 3. Location at midnight: N29E52
[S991] emerged in the northeast quadrant on May 3. Location at midnight: N22E66

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 late October 2002)
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago

A poorly defined coronal hole (CH447) in the southern hemisphere was in an Earth facing position on May 2-3.

The darkest areas on the solar disk are likely coronal holes.

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.

Forecast

The geomagnetic field is expected to be mostly quiet on May 4-6. There is a possibility of unsettled intervals on May 5-6 if a coronal hole stream associatred with CH447 arrives.

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 polarity overlay		Comment
		SWPC	STAR SDO			SWPC	STAR	Current	Previous
11201	2011.04.24 2011.04.27			N14W43						location: N11W36
11200	2011.04.25 2011.04.26	10	4	S18W49	0030	CRO	BXO			area: 0010 location: S18W51
S974	2011.04.27			S37W25						plage
11203	2011.04.28	1	6	N17E11	0120	HSX	CSO			location: N17E13
S976	2011.04.28			N07W20						plage
S977	2011.04.28			N05W36						plage
S979	2011.04.28			N28W58						plage
11206	2011.04.29 2011.05.03	3	4	N22W18	0010	BXO	AXX			formerly region S980 location: N22W16
11204	2011.04.30 2011.05.02	10	19	N17E26	0130	CAO	CSI			location: N15E27
11205	2011.04.30 2011.05.02	3	5	N14E37	0010	BXO	BXO
S984	2011.04.30			S35W54						plage
S985	2011.04.30			N21W32						plage
S986	2011.05.01			S20E10						plage
S987	2011.05.01			N35W55						plage
S988	2011.05.02		4	N12W46	0010		BXO
S989	2011.05.03		1	N21E46	0000		AXX
S990	2011.05.03		1	N29E52	0000		AXX
S991	2011.05.03		1	N22E66	0000		AXX
Total spot count:		27	45
Sunspot number:		77	135

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 preliminary daily SWPC ap indices. Values in red are based on the official NGDC 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.