Solar Terrestrial Activity Report

Activity chart

Last major update issued on April 4, 2012 at 06:40 UTC.

[Solar and geomagnetic data - last month (updated daily)]
[Solar wind and electron fluence charts (updated daily)
[Solar cycles 21-24 (last update April 1, 2012)]
[Solar cycles 1-20]
[Graphical comparison of cycles 21, 22, 23 and 24 (last update April 1, 2012)]
[Graphical comparison of cycles 10, 12, 13, 14, 16 and 24 (last update April 1, 2012)]
[Historical solar and geomagnetic data charts 1954-2006 (last update April 5, 2007)]
[Archived reports since January 2003 (last update April 1, 2012)]

[POES auroral activity level since October 2009 - updated April 1, 2012]
Annotated geomagnetic activity charts - Carrington rotation 2118 [December 2011 - January 2012] - 2119 [January-February 2012]
[Solar polar fields vs solar cycles - updated June 27, 2011]

Recent activity

The geomagnetic field was quiet to unsettled on April 3. Solar wind speed at SOHO ranged between 276 and 342 km/s.

Solar flux measured at 20h UTC on 2.8 GHz was 103.5 (decreasing 32.2 over the last solar rotation). The Potsdam WDC planetary A index was 8 (STAR Ap - based on the mean of three hour interval ap indices: 8.4). Three hour interval K indices: 33111123 (planetary), 22201212 (Boulder).

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

At midnight UTC the visible solar disk had 6 spotted active regions (in 2K resolution SDO images).

Region 11445 [S22W73] was quiet and stable.
Region 11448 [S18W23] was quiet and stable.
Region 11450 [N15W04] lost some of its magnetic complexity and has a very elongated leader penumbra. There's only rudimentary penumbra on the trailing spots.
Region 11451 [N18E17] was quiet and stable.
Region 11452 [N18E33] developed slowly and was quiet.
Region 11453 [S17W10] decayed slowly and quietly

Coronal mass ejections (CMEs)

April 1-3: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery. A filament eruption in the northern hemisphere early on April 2 caused a CME and was observed in both LASCO and STEREO images. There's a slight chance of a flank impact from this CME on April  5.

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 was probably too far to the south on April 3 to become geoeffective.

Coronal hole map

The above coronal hole map is based on a method where coronal holes are detected automatically. While the method may need some fine tuning, it has significant advantages over detecting coronal holes manually. The main improvement is the ability to detect coronal holes at and just beyond the solar limbs. Early results using this method for SDO images over a span of several weeks indicate a good match between coronal holes observed over the visible disk and their extent and position at the east and west limbs. Note that the polar coronal holes are easily detected using this method, the extent and intensity of both CHs are consistent with other data sources.

Propagation

Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and 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 quiet to unsettled on April 4 due to weak effects from CH510. There's a slight chance of a flank CME impact on April 5. If the CME reaches Earth some unsettled and active intervals are possible. Otherwise expect quiet conditions  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: 0-20% probability, Yellow: 20-60% probability, Red: 60-100% probability.

Active solar regions

Click on image for higher resolution image) Compare to the previous day's image

When available the active region map has a coronal hole polarity overlay where red (pink) is negative and blue (blue-green) 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 STAR SDO SWPC STAR Current Previous
2K 1K
11445 2012.03.23 1 3 1 S22W71 0110 HSX CSO

area: 0130

location: S22W73

11448 2012.03.26
2012.03.28
  3 1 S17W27 0000   BXO location: S18W23
11453 2012.03.27
2012.04.02
5 9 4 S17W11 0020 BXO BXO  
11449 2012.03.28
2012.03.29
      S18W88         plage
S1558 2012.03.28       S30W58         plage
11450 2012.03.30
2012.03.31
13 25 12 N16W04 0060 DSI DAI  
11451 2012.03.30
2012.03.31
  5   N18E11 0000   BXO

location: N18E17

11452 2012.03.31
2012.04.02
3 13 6 N18E33 0020 BXO DAI  
S1563 2012.03.31       N26W22           plage
Total spot count: 22 58 24  
Sunspot number: 62 118 74  (total spot count + 10 * number of spotted regions)
Weighted penumbral SN: 37 73 39  (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): 37 41 41 k * (sunspot number). k = 0.6 for SWPC, k = 0.35 (changed from 0.45 on March 1, 2011) for STAR SDO 2K, k = 0.55 for STAR SDO 1K

Monthly solar cycle data

Month Average measured solar flux International sunspot number (SIDC) Smoothed sunspot number Average ap
(3)
2008.07 65.7 (SF minimum) 0.5 2.8 (-0.4)  
2008.12 69.2 0.8 1.7 (-)
sunspot minimum
 
2011.01 83.6 19.1 31.0 (+2.2) 5.51
2011.02 94.6 29.4 33.4 (+2.4)  6.44
2011.03 115.0 56.2 36.9 (+3.5) 8.18
2011.04 112.6 54.4 41.8 (+4.9) 8.83
2011.05 95.8 41.6 47.6 (+5.8) 8.94
2011.06 95.8 37.0 53.2 (+5.6) 8.06
2011.07 94.2 43.9 57.2 (+4.0) 8.16
2011.08 101.7 50.6 59.0 (+1.8) 7.26
2011.09 133.8 78.0 59.5 (+0.5) 12.27
2011.10 137.3 88.0 (60.1 projected, +0.6) 8.28
2011.11 153.5 96.7 (61.6 projected, +1.5) 5.55
2011.12 141.3 73.0 (64.3 projected, +2.7) 3.78
2012.01 132.5 58.3 (67.8 projected, +3.5) 7.15
2012.02 106.5 33.1 (71.8 projected, +4.0) 8.81
2012.03 114.7 64.2 (73.9 projected, +2.1) 16.08
2012.04 105.6 (1) 6.0 (2A) / 59.7 (2B) (74.9 projected, +1.0) (10.63)

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 SIDC international sunspot number is typically 30-50% lower. 2B) Month average to date.
3) Running average based on the quicklook Potsdam WDC ap indices. Values in red are based on the definitive international Potsdam WDC ap indices.

This report has been prepared by Jan Alvestad. It is based on 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.