Solar Terrestrial Activity Report

Activity chart

Last major update issued on May 4, 2015 at 05:40 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 (May 1, 2015)
Solar cycle Solar cycles 23-24 (May 1, 2015) Historical solar and geomagnetic data charts 1954-2006 (April 5, 2007)
  Cycle 24 progress (May 1, 2015) Noon SDO sunspot count 1K Reference: 4K (large file) (*)
  Solar cycles 1-20 POES auroral activity level October 2009 - December 2012
  Comparison of cycles 21, 22, 23 and 24 (May 1, 2015) 3rd SSN Workshop, Tucson, 2013
  Comparison of cycles 10, 12, 13, 14, 16 and 24 (May 1, 2015) 4th SSN Workshop, Locarno, 2014
  Solar polar fields vs solar cycles (April 10, 2015)  

Recent activity

The geomagnetic field was quiet on May 3. Solar wind speed at SOHO ranged between 353 and 488 km/s.

Solar flux at 20h UTC on 2.8 GHz was 111.1 (decreasing 6.1 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 125.8. The Potsdam WDC planetary A index was 6 (STAR Ap - based on the mean of three hour interval ap indices: 5.6). Three hour interval K indices: 22211111 (planetary), 23322211 (Boulder).

The background x-ray flux is at the class B6 level.

At the time of counting spots (see image time), spots were observed in 8 active regions using 2K resolution (SN: 168) and 7 active regions using 1K resolution (SN: 117) SDO images on the visible solar disk.

Region 12335 [S15E37] developed further gaining spots and penumbral area. C and minor M class flares are possible.
New region 12336 [N14E14] emerged on May 2 and was numbered by SWPC the next day. C flares are possible.
New region 12337 [S16E58] emerged on May 2 and received its NOAA number the following day.
New region 12338 [N04E57] rotated into view on May 2 and developed slowly on May 3.

Spotted regions not numbered (or interpreted differently) by SWPC:
S4426 [S12E07] was quiet and stable.
S4429 [S26E02] was quiet and stable.
New region S4438 [N05E66] emerged with penumbra spots trailing AR 12338.
New region S4439 [N12E76] rotated into view.

C2+ flares:

Magnitude Peak time (UTC) Location AR Recorded by Comment
C2.2 23:47 S18E42 12335 GOES15  

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

Coronal mass ejections (CMEs)

May 1, 3: No obviously Earth directed CMEs were observed.
May 2: A partial halo CME was observed late in the day and early on May 3 after a large filament eruption in the southern hemisphere.

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 (CH666) was in a potentially geoeffective position on May 2. CH666 has decayed over the last days and may not be capable of creating a geomagnetic disturbance.

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.

Forecast

The geomagnetic field is expected to be quiet on May 4-5. There is a slight possibility of a few unsettled intervals due to weak effects from CH666 on May 5-6. The CME observed late on May 2 and early on May 3 was fairly slow and may have had Earth directed extensions which could reach us on May 6. In that case some unsettled and active intervals are possible.

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 overlays
Comment
SWPC Magnetic
(SDO)
SWPC STAR Current Previous
2K 1K
12333 2015.04.21
2015.04.22
       N22W83            
12334 2015.04.27
2015.04.30
      S20W31          
S4421 2015.04.27       S10W31            
S4423 2015.04.29       S27W45            
12335 2015.04.30 20 50 28 S16E37 0170 DAC EAC beta-gamma

area: 0450

S4426 2015.04.30   12 3 S12E07 0020   BXO  
S4427 2015.04.30       N13W44            
S4428 2015.04.30       N13W16            
S4429 2015.05.01   1 1 S26E02 0003   AXX  
S4430 2015.05.01       S22W45            
S4431 2015.05.02       N01W38          
S4432 2015.05.02       S12W30          
12338 2015.05.02
2015.05.03
2 6 3 N04E56 0010 AXX CRO area: 0025
12336 2015.05.02
2015.05.03
3 12 9 N13E12 0010 BXO DRI area: 0060
12337 2015.05.02
2015.05.03
2 4 2 S16E56 0010 AXX BXO  
S4437 2015.05.02       N10W16          
S4438 2015.05.03   2   N05E66 0005   BXO    
S4439 2015.05.03   1 1 N12E76 0005   AXX    
Total spot count: 27 88 47  
Sunspot number: 67 168 117  (total spot count + 10 * number of spotted regions)
Weighted SN: 32 99 58  (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 59 64 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
2013.12 147.7 143.1 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) (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 78.5 (-1.2) 4.50
2014.08 124.7 127.9 74.7 75.5 (-3.0) 7.71
2014.09 146.6 148.1 87.6 70.8 (-4.7) 9.78
2014.10 153.4 152.9 60.6 67.3 (-3.5) 8.96
2014.11 154.8 151.4 70.1 (64.9 projected, -2.4) 9.33
2014.12 158.7 153.8 78.0 (62.6 projected, -2.3) 11.24
2015.01 141.9 137.3 67.0 (60.4 projected, -2.2) 9.46
2015.02 129.1 126.0 44.8 (58.7 projected, -1.7) 9.92
2015.03 125.9 124.6 38.4 (56.3 projected, -2.4) 16.14
2015.04 128.8 129.7 54.4 (53.7 projected, -2.6) 10.3
2015.05 (105.6)    3.4 (2A) / 35 (2B) / 77.8 (2C) (51.5 projected, -2.2) (5.7)

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.