Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 20, 2016 at 04:30 UT.

Charts (* = updated daily) Data and archive
  Solar wind (*) Solar and geomagnetic data - last month (*)
  Electron fluence (*) Archived daily reports and monthly data from 2003.01 (April 2, 2016)
Solar cycle Solar cycles 23-24 (April 2, 2016) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (April 2, 2016) Noon SDO sunspot count 1K / 4K (*)
  Solar cycles 1-24 (July 17, 2015) POES auroral activity level October 2009 - December 2012
  Comparison of cycles 21, 22, 23 and 24 (April 2, 2016) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 12, 13, 14, 16 and 24 (April 2, 2016) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs. solar cycles (April 20, 2016)  

Recent activity

The geomagnetic field was very quiet on April 19 with no signs of any coronal hole high speed stream. Solar wind speed at SOHO ranged between 346 and 440 km/s.

Solar flux at 20h UTC on 2.8 GHz was 89.1 (increasing 2.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 97.1. The Potsdam WDC planetary A index was 2 (STAR Ap - based on the mean of three hour interval ap indices: 1.5). Three hour interval K indices: 00001001 (planetary), 00111211 (Boulder).

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

At the time of counting spots (see image time), spots were observed in 5 active regions using 2K resolution (SN: 76) and 3 active regions using 1K resolution (SN: 39) SDO images on the visible solar disk.

Region 12529 [N10W82] decayed slowly and was mostly quiet.
Region 12531 [N15W23] was quiet and stable.
Region 12532 [N06E28] lost penumbral area while gaining tiny spots.

Spotted regions not numbered (or interpreted differently) by SWPC:
S5237 [N10W01] reemerged with tiny spots.
New region S5245 [S02E83] rotated into view.

C2+ flares:

Magnitude Peak time (UT) Location AR Recorded by Comment
           

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

Coronal mass ejections (CMEs)

April 17-19: No obviously Earth directed CMEs were observed in available LASCO 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 northern hemisphere coronal hole (CH728) rotated across the central meridian on April 15-16. A recurrent trans equatorial extension of a northern hemisphere coronal hole will likely rotate into an Earth facing position on April 20-21.

Propagation

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

Forecast

The geomagnetic field is expected to be quiet to unsettled on April 20-22. A high speed stream associated with CH729 could cause unsettled to minor storm conditions on April 23-24.

Coronal holes (1) Coronal mass ejection (2) M and X class flares (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: 0-30% probability, Yellow: 30-70% probability, Red: 70-100% probability.

Active solar regions


(Click on image for 2K resolution). 4K 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
12529 2016.04.07 5 5 3 N10W81 0600 CKO HKX

location: N10W69

area: 0700

12531 2016.04.12
2016.04.13
  2   N13W22 0005   AXX location: N15W23
S5234 2016.04.13       S03W33            
S5237 2016.04.14   2   N10W01 0005   AXX    
12532 2016.04.15
2016.04.16
3 16 5 N06E27 0040 CAO CRI

 

S5242 2016.04.16       S19W12            
S5243 2016.04.17       N36W13            
S5245 2016.04.19   1 1 S02E83 0180   HSX    
Total spot count: 8 26 9  
Sunspot number: 28 76 39  (total spot count + 10 * number of spotted regions)
Weighted SN: 23 44 27  (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): 31 34 31 k * (sunspot number)
As of February 19, 2016: k = 1.1 for SWPC, k = 0.45 for MSN 2K, k = 0.80 for MSN 1K (MSN=Magnetic Sunspot Number)

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO) (4)
Smoothed sunspot number (4) Average ap
(3)
Measured 1 AU
2014.02 170.3
(cycle peak)
166.3 146.1 (cycle peak) 110.5 (+1.2) 10.70
2014.04 143.9 144.8 112.5 116.4 (+2.1) (solar max) 7.88
2015.02 129.1 126.0 66.7 86.1 (-3.2) 9.92
2015.03 125.9 124.6 54.5 82.2 (-3.9) 16.14
2015.04 128.8 129.7 75.3 78.9 (-3.3) 10.73
2015.05 120.0 122.6 88.8 76.1 (-2.8) 8.29
2015.06 122.3 126.1 66.5 72.1 (-4.0) 13.15
2015.07 107.0 110.8 66.4 68.3 (-3.8) 8.83
2015.08 105.4 108.0 64.6 66.4 (-1.9) 14.58
2015.09 101.7 102.7 78.1 66.0 (-0.4) 15.78
2015.10 104.1 103.3 61.7 (64.6 projected, -1.4) 14.02
2015.11 109.3 106.9 63.2 (61.9 projected, -2.7) 12.09
2015.12 113.1 109.5 57.7 (59.9 projected, -2.0) 14.29
2016.01 103.4 100.1 56.6 (58.2 projected, -1.7) 9.4
2016.02 103.6 101.0 57.2 (55.9 projected, -2.3) 9.9
2016.03 91.5 90.6 54.9 (52.9 projected, -3.0) 10.58
2016.04 (98.0)   20.1 (2A) / 31.7 (2B) / 33.3 (2C) (50.2 projected, -2.7) (9.2)

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.