Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 6, 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 unsettled on April 5. Solar wind speed at SOHO ranged between 462 and 569 km/s under the influence of a high speed stream from CH661.

Solar flux at 20h UTC on 2.8 GHz was 122.2 (decreasing 0.7 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 128.4. The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.9). Three hour interval K indices: 22111113 (planetary), 22112223 (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 13 active regions using 2K resolution (SN: 200) and 10 active regions using 1K resolution (SN: 135) SDO images on the visible solar disk.

Region 12317 [N12W83] developed significantly and was mostly quiet.
Region 12318 [N08E43] was quiet and stable.
Region 12319 [S09W09] decayed slowly and quietly.
Region 12320 [S12E29] developed further becoming a compact region. Magnetically the region currently has a fairly simple layout.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4339 [N08W72] developed slowly and quietly.
S4342 [S26E04] was quiet and stable.
S4345 [N10E48] was quiet and stable.
S4346 [N10W00] developed slowly and quietly.
S4347 [N27W15] was quiet and stable.
New region S4348 [S16E38] was observed with penumbra spots.
New region S4349 [S15E12] emerged with a penumbra spot.
New region S4350 [N21W67] emerged with a penumbra spot.
New region S4351 [N31E36] emerged with a penumbra spot.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
C3.1 03:42 NW limb   SDO/EVE C1.9 @ GOES15 - peak 03:36 UT
C3.8 (LDE) 21:06 S12E30 12320 SDO/EVE C3.0 @ GOES15 - peak 21:03 UT

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

Coronal mass ejections (CMEs)

April 3-5: 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 (CH662) was in an Earth facing position on April 5. No geomagnetic disturbances have been associated with CH662 during previous rotations.

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 to fair.

Forecast

The geomagnetic field is expected to be mostly quiet on April 6-8.

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
12314 2015.03.25
2015.03.26
      S21W71            
12316 2015.03.27
2015.03.29
      S21W50          
S4324 2015.03.28       N03W55            
S4327 2015.03.29       S15W56          
S4328 2015.03.30       N23W52            
S4329 2015.03.31       N14W30            
S4330 2015.03.31       N15W46            
S4331 2015.03.31       S31W18          
12317 2015.04.01 1 1 1 N11W85 0030 HSX HAX area: 0160
12319 2015.04.02
2015.04.04
2 3 2 S10W06 0010 AXX CRO  
S4337 2015.04.02       N21W26            
S4339 2015.04.02   4 3 N08W72 0020   CRO  
12320 2015.04.02
2015.04.04
14 33 18 S12E28 0140 DAI DAC

area: 0220

12318 2015.04.03 9 13 7 N10E41 0050 DAO DRO location: N08E43
S4342 2015.04.03   5 1 S26E04 0010   BXO  
S4345 2015.04.03   1 1 N10E48 0010   HRX  
S4346 2015.04.04   2 2 N10W00 0010   AXX  
S4347 2015.04.04   1   N27W15 0001   AXX  
S4348 2015.04.05   4 1 S16E38 0010   BXO    
S4349 2015.04.05   1   S15E12 0002   AXX    
S4350 2015.04.05   1 1 N21W67 0004   AXX    
S4351 2015.04.05   1   N31E36 0001   AXX    
Total spot count: 26 70 37  
Sunspot number: 66 200 137  (total spot count + 10 * number of spotted regions)
Weighted SN: 41 92 59  (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): 40 70 75 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 (122.0)   8.8 (2A) / 52.6 (2B) / 62.6 (2C) (53.4 projected, -2.7) (8.6)

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.