Solar Terrestrial Activity Report

Last major update issued on October 1, 2015 at 05:05 UT.

Recent activity

The geomagnetic field was very quiet on September 30. Solar wind speed at SOHO ranged between 271 and 356 km/s.

Solar flux at 20h UTC on 2.8 GHz was 131.1 (increasing 44.6 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 107.0. The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.6). Three hour interval K indices: 00000001 (planetary), 10012211 (Boulder).

The background x-ray flux is at the class B8 level.

At the time of counting spots (see image time), spots were observed in 7 active regions using 2K resolution (SN: 183) and 3 active regions using 1K resolution (SN: 90) SDO images on the visible solar disk.

Region 12420 [N09W61] decayed slowly and was mostly quietly.
Region 12422 [S20W53] decayed slowly losing penumbral area in the leading and trailing spots. The region still has multiple magnetic deltas and could produce a major flare.
Region 12426 [N19W17] was quiet and stable.
Region 12427 [N17E09] developed slowly and quietly. The region has minor polarity intermixing.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4781 [S18E16] lost the leader spot and gained a trailing spot.
New region S4791 [N09E34] emerged with tiny spots.
New region S4792 [N16E57] was observed with tiny spots.

The most interesting activity of the day was near the west limb as AR 12423 continued to be active and seemed to trigger an extensive filament eruption. This eruption was associated with a wide and well defined CME.

C2+ flares:

Flare activity (SDO/EVE/ESP XRS-B proxy)

Coronal mass ejections (CMEs)

September 28-30: No obviously Earth directed CMEs were observed in available LASCO imagery. The west limb CME observed on September 30 may have had a small Earth directed component.

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 small recurrent northern hemisphere coronal hole (CH692) was in an Earth facing position on September 29. A recurrent trans equatorial coronal hole (CH694) will likely rotate into an Earth facing position on October 3-4.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is fair. Propagation on long distance northeast-southwest paths is poor.

Forecast

The geomagnetic field is expected to be mostly quiet on October 1. Quiet to unsettled is possible on October 2-3 due to effects from diminishing CH692. There is a minor chance a component of the CME observed on September 30 could reach Earth on October 3 and cause unsettled to active conditions.

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: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% probability.

Active solar regions

(Click on image for 2K resolution) Compare to the previous day's image.

0.5K image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue 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 overlays		Comment
		SWPC	Magnetic (SDO)				SWPC	STAR	Current	Previous
			2K	1K
12420	2015.09.19 2015.09.20	2	12	4	N12W57	0040	CSO	CRO			location: N09W61
12421	2015.09.20 2015.09.22				N16W78
12422	2015.09.22	23	50	31	S18W55	0860	FKC	FKC			beta-gamma-delta location: S20W53
12425	2015.09.23 2015.09.25				S05W72
12426	2015.09.24 2015.09.25		2		N16W20	0004		AXX
S4780	2015.09.24				N30W29
S4781	2015.09.26		1		S18E16	0002		AXX
12427	2015.09.27	12	44	25	N18E09	0180	DSI	DAI			beta-gamma area: 0290
12428	2015.09.27 2015.09.28	1			S04W92	0010	HRX				rotated out of view
S4786	2015.09.27				S10W58
S4787	2015.09.28				S18W35
S4791	2015.09.30		2		N09E34	0003		AXX
S4792	2015.09.30		2		N16E57	0003		AXX
Total spot count:		38	113	60
Sunspot number:		78	183	90	(total spot count + 10 * number of spotted regions)
Weighted SN:		61	131	78	(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):		86	101	77	k * (sunspot number) As of July 1, 2015: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.85 for MSN 1K (MSN=Magnetic Sunspot Number)

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).
2B) Boulder SN current month average to date.
2C) STAR SDO 1K Wolf number 30 day average.
3) Running average based on the quicklook and definitive Potsdam WDC ap indices. Values in red are based on the definitive international GFZ Potsdam WDC ap indices.
4) Updated to new data set from WDC-SILSO on July 1, 2015

This report has been prepared by Jan Alvestad. It is based on the analysis of data from whatever sources are available at the time the report is prepared. All time references are to Universal Time. Comments and suggestions are always welcome.

SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.