Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 3, 2015 at 05:30 UT

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)]
[Solar cycles 23-24 (last update April 1, 2015)] [Cycle 24 progress (last update April 1, 2015) ]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2015)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2015)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 1, 2015)]

[Noon SDO sunspot count 1K Reference: 4K (large file) (updated daily)]

[POES auroral activity level October 2009 - December 2012]
[Solar polar fields vs solar cycles - updated March 15, 2015]
[Presentations: 3rd SSN Workshop, Tucson, 2013 (pdf) / 4th SSN Workshop, Locarno, 2014]

Recent activity

The geomagnetic field was quiet to active on April 2. Solar wind speed at SOHO ranged between 387 and 470 km/s.

Solar flux at 20h UTC on 2.8 GHz was 121.3 (decreasing 6.1 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 129.1. The Potsdam WDC planetary A index was 11 (STAR Ap - based on the mean of three hour interval ap indices: 11.3). Three hour interval K indices: 12222244 (planetary), 22323434 (Boulder).

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

At the time of counting spots (see image time), spots were observed in 12 active regions using 2K resolution (SN: 169) and 6 active regions using 1K resolution (SN: 77) SDO images on the visible solar disk.

Region 12313 [N18W49] decayed slowly and quietly.
Region 12314 [S22W26] was quiet and stable.
Region 12316 [S19W10] was quiet and stable.
Region 12317 [N10W43] developed slowly and was mostly quiet.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4311 [S24W55] decayed slowly and quietly.
S4327 [S13W18] decayed slowly and quietly.
S4331 [S15E20] decayed slowly and quietly.
New region S4336 [S11E32] emerged with small spots.
New region S4337 [N21E10] was observed with a penumbra spot.
New region S4338 [S24W76] emerged with penumbra spots.
New region S4339 [N07W38] emerged with penumbra spots.
New region S4340 [S12E68] rotated into view.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
           

Flare activity according to SDO/EVE/ESP XRS-B proxy

Coronal mass ejections (CMEs)

March 31 - April 2: No obviously Earth directed CMEs were observed.

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 (CH661) was in an Earth facing position on March 30-31.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over 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 active on April 3-4 due to effects from a high speed stream associated with CH661 and quiet on April 5-6.

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) 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 overlay
Comment
SWPC Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
12305 2015.03.20
2015.03.21
1     S09W91 0220 HSX    

rotated out of view

12310 2015.03.22
2015.03.23
      N04W83        

 

12312 2015.03.23       N09W55           trailing part of AR 12310

SWPC location on April 1 was stated as N08W58

12315 2015.03.23
2015.03.28
      S25W79         location: S18W78

SWPC location on April 1 was S21W66

S4311 2015.03.23   2   S24W55 0003   AXX  
12313 2015.03.23
2015.03.24
  4 1 N18W54 0010   BXO

 

12314 2015.03.25
2015.03.26
  1 1 S21W29 0003   AXX location: S22W26
12316 2015.03.27
2015.03.29
  3   S21W08 0006   AXX  
S4324 2015.03.28       N03W16            
S4325 2015.03.28       S15W47            
S4326 2015.03.29       N16W34            
S4327 2015.03.29   3   S13W18 0006   AXX  
S4328 2015.03.30       N23W13            
S4329 2015.03.31       N14E09            
S4330 2015.03.31       N15W07            
S4331 2015.03.31   3   S15E19 0005   BXO  
S4333 2015.03.31       S09W34            
12317 2015.04.01 10 19 10 N09W45 0060 DSI DAI area: 0120

location: N10W43

S4335 2015.04.01       S22W42          
S4336 2015.04.02   3 2 S11E32 0010   CRO    
S4337 2015.04.02   1 1 N21E10 0002   AXX    
S4338 2015.04.02   6 2 N24W76 0015   BXO    
S4339 2015.04.02   2   N07W38 0004   BXO    
S4340 2015.04.02   2   S12E68 0004   AXX    
Total spot count: 11 49 17  
Sunspot number: 31 169 77  (total spot count + 10 * number of spotted regions)
Weighted SN: 21 57 25  (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): 19 59 42 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for MSN 2K, k = 0.55 for MSN 1K (MSN=Magnetic Sunspot Number)

Monthly solar cycle data

Month Average solar flux International sunspot number
(WDC-SILSO)
Smoothed sunspot number Average ap
(3)
Measured 1 AU
2013.11  148.3 145.1 77.6 75.4 (+0.4) 5.68
2013.12 147.7 143.1 90.3 76.0 (+0.6) 4.68
2014.01 157.4 152.4 81.8 77.3 (+1.3) 5.44
2014.02 170.3
(cycle peak)
166.3 102.3 (cycle peak) 78.4 (+1.1) 10.70
2014.03 149.9 148.5 91.9 80.8 (+2.4) 4.88
2014.04 143.9 144.8 84.7 81.9 (+1.1)
(likely solar max)
7.88
2014.05 129.7 132.9 75.2 80.5 (-1.4) 5.75
2014.06 122.0 125.8 71.0 79.7 (-0.8) 6.72
2014.07 137.4 141.8 72.5 78.6 (-1.1) 4.50
2014.08 124.7 127.9 74.7 75.6 (-3.0) 7.71
2014.09 146.6 148.1 87.6 70.9 (-4.7) 9.78
2014.10 153.4 152.9 60.6 (67.3 projected, -3.6) 8.96
2014.11 154.8 151.4 70.1 (64.7 projected, -2.6) 9.33
2014.12 158.7 153.8 78.0 (62.4 projected, -2.3) 11.24
2015.01 141.9 137.3 67.0 (60.2 projected, -2.2) 9.46
2015.02 129.1 126.0 44.8 (58.4 projected, -1.8) 9.92
2015.03 126.0 124.6 38.4 (56.1 projected, -2.3) 15.5
2015.04 (122.7)   3.3 (2A) / 50.0 (2B) / 61.8 (2C) (53.4 projected, -2.7) (8.7)

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 WDC-SILSO international sunspot number is typically 30-50% lower. 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.

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 the UTC day. Comments and suggestions are always welcome.

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