Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 10, 2015 at 04:30 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 April 10, 2015]
[Presentations: 3rd SSN Workshop, Tucson, 2013 (pdf) / 4th SSN Workshop, Locarno, 2014]

Recent activity

The geomagnetic field was quiet to unsettled on April 9. Solar wind speed at SOHO ranged between 340 and 424 km/s. A weak disturbance, probably related to a low speed stream from CH661, began early in the day. Solar wind speed increased at SOHO early on April 10 and the total field of the interplanetary magnetic field became stronger as another disturbance arrived. This may have been related to the arrival of the CME observed  late on April 6.

Solar flux at 20h UTC on 2.8 GHz was 111.3 (decreasing 8.1 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 127.0. The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 9.6). Three hour interval K indices: 23232223 (planetary), 22233323 (Boulder).

The background x-ray flux is at the class B3 level.

At the time of counting spots (see image time), spots were observed in 10 active regions using 2K resolution (SN: 169) and 8 active regions using 1K resolution (SN: 112) SDO images on the visible solar disk.

Region 12318 [N07W08] decayed slowly and quietly.
Region 12319 [S10W63] reemerged with penumbra spots.
Region 12320 [S13W22] decayed slowly and produced several C flares.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4342 [S31W34] was quiet and stable.
S4346 [N15W55] was quiet and stable.
S4348 [S14W11] was quiet and stable.
S4352 [S19W04] decayed slowly and quietly.
S4354 [S04W63] reemerged with penumbra spots.
S4358 [S13E47] was quiet and stable.
New region S4361 [S22E31] emerged with a penumbra spot.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
C5.4/1N 06:35 S14W13 12320 GOES15  
C5.9/1N 17:29 S15W21 12320 GOES15 C7.1 @ SDO/EVE
C6.2/1F 19:01 S15W21 12320 GOES15  
C3.3 23:45 S15W21 12320 GOES15  

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

Coronal mass ejections (CMEs)

April 7-9: 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]

An extension of the southern polar coronal hole could be associated with a co-rotating interaction region. Then extension will rotate across the central meridian on April 12-13.

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 fair.

Forecast

The geomagnetic field is expected to be quiet to active on April 10 with a chance of minor storm intervals due to CME effects. Quiet conditions are likely on April 11-12.

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
12319 2015.04.02
2015.04.04
  2 1 S10W71 0005   BXO  

location: S10W63

12320 2015.04.02
2015.04.04
13 40 20 S12W25 0140 EAC DAI

beta-gamma-delta

location: S13W22

12318 2015.04.03 4 10 4 N08W08 0010 BXO BXO  
S4342 2015.04.03   2 1 S31W34 0006   BXO  
S4345 2015.04.03       N10W05          
S4346 2015.04.04   2 1 N15W55 0008   AXX  
S4348 2015.04.05   2 2 S14W11 0007   AXX  
S4349 2015.04.05       S15W40            
S4351 2015.04.05       N31W16            
S4352 2015.04.06   6   S19W04 0012   BXO  
S4354 2015.04.07   3 2 S04W63 0010   BXO    
S4355 2015.04.07       N01W01          
S4355 2015.04.07       N01W01          
S4358 2015.04.07   1 1 S13E47 0005   AXX  
S4359 2015.04.07       N11E37            
S4360 2015.04.08       S10E12          
S4361 2015.04.09   1   S22E31 0003   AXX    
Total spot count: 17 69 32  
Sunspot number: 37 169 112  (total spot count + 10 * number of spotted regions)
Weighted SN: 30 95 49  (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): 22 59 62 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
2015.03 125.9 124.6 38.4 (56.1 projected, -2.3) 16.14
2015.04 (117.3)   15.2 (2A) / 50.8 (2B) / 65.1 (2C) (53.4 projected, -2.7) (7.0)

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.