Last major update issued on April 5, 2014 at 06:20 UTC.
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[Solar cycles 23-24 (last update April 1, 2014)] [Cycle 24 progress (last update April 1, 2014) ]
[Solar cycles 1-20]
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[Presentation 3rd SSN Workshop, Tucson, 2013 (pdf)]
The geomagnetic field was quiet on April 4. Solar wind speed at SOHO ranged between 367 and 467 km/s. ACE EPAM data indicate that a CME arrived during the day, sometime after noon, probably the CME observed on April 1. No solar wind shock was observed and there was no significant increase in geomagnetic activity. The CME observed on April 2 has not yet arrived.
Solar flux at 20h UTC on 2.8 GHz was 156.9 (increasing 15.3 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 154.5. The Potsdam WDC planetary A index was 5 (STAR Ap - based on the mean of three hour interval ap indices: 4.8). Three hour interval K indices: 11222210 (planetary), 11223321 (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 in 2K resolution (SN: 338) and 11 active regions in 1K resolution (SN: 220) SDO images on the visible solar disk.
Region 12021 [S13W41] developed a magnetic delta
structure in the largest penumbral structure. M flares are possible.
C5+ flare: C6.2 at 14:54 UTC.
Region 12022 [N17W27] was quiet and stable.
Region 12026 [S11E14] was mostly quiet and stable with some decay observed in the leading and central spots sections. C and M class flares are possible.
Region 12027 [N12E18] was mostly unchanged. C5+ flare: C8.3/1F at 13:48 UTC. This flare was associated with a fairly narrow CME off the northeast limb.
Region 12028 [S08E23] was quiet and stable.
Region 12029 [N17E02] decayed slowly and quietly.
Region 12030 [N10E31] developed gaining many spots. The region has polarity intermixing and could produce C and minor M class flares.
Spotted regions not numbered (or interpreted differently) by SWPC:
S3288 [N06E15] lost the leader spots.
S3297 [N07W43] lost the trailing spots and was quiet.
S3298 [N08E18] was quiet and stable.
New region S3301 [N14E66] emerged with a penumbra spot.
New region S3302 [S19E39] emerged with a penumbra spot.
April 2: A large and fast asymmetrical full halo CME was observed after
the M6.5 event in AR 12027.
April 3-4: No obviously Earth directed CMEs were observed in LASCO and STEREO imagery.
Coronal hole history (since October
Compare today's report to the situation one solar rotation ago: 28 days ago 27 days ago 26 days ago
No obvious coronal holes are currently in or near potentially geoeffective positions.
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.
The geomagnetic field is expected to be quiet to active on April 5 due to CME effects and quiet on April 6-7.
|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
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.
(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
|Spot count||Location at midnight||Area||Classification||SDO / HMI 4K continuum
image with magnetic polarity overlay
|Total spot count:||89||218||110|
|Sunspot number:||159||338||220||(total spot count + 10 * number of spotted regions)|
|Weighted SN:||124||272||154||(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):||95||118||121||k * (sunspot number). k = 0.6 for SWPC, k = 0.35 for MSN 2K, k = 0.55 for MSN 1K (MSN=Magnetic Sunspot Number)|
|Month||Average solar flux||International sunspot number
|Smoothed sunspot number||Average ap
|2013.10||132.1||131.2||85.6||(74.9 projected, +1.8)||7.71|
|2013.11||148.3||145.1||77.6||(74.9 projected, -0.0)||5.68|
|2013.12||147.7||143.1||90.3||(74.4 projected, -0.5)||4.68|
|2014.01||157.4||152.4||82.0||(74.3 projected, -0.1)||5.44|
|166.3||102.8 (cycle peak)||(73.7 projected, -0.6)||10.70|
|2014.03||149.9||148.5||92.2||(73.8 projected, +0.1)||4.88|
|2014.04||154.5(1)||18.2 (2A) / 136.5 (2B) / 108.1 (2C)||(73.0 projected, -0.8)||(5.0)|
1) Running average based on the daily 20:00 UTC observed solar flux value at
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.