The geomagnetic field was quiet to active on December 19. Solar wind speed at SOHO ranged between 336 and 490 km/s. A solar wind shock was observed at SOHO at 15:26 UT. This was likely the arrival of the combined CMEs observed on December 16. While there were a few southward excursions of the IMF Bz component initially, Bz was mostly near neutral towards the end of the day. Bz swung strongly southwards after 02h UT on December 20, this will likely cause minor to major geomagnetic storming.
Solar flux at 20h UTC on 2.8 GHz was 119.0 (decreasing 3.9 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 106.8. The Potsdam WDC planetary A index was 10 (STAR Ap - based on the mean of three hour interval ap indices: 10.1). Three hour interval K indices: 11001344 (planetary), 11111443 (Boulder).
The background x-ray flux is at the class B7 level.
At the time of counting spots (see image time), spots were observed in 5 active regions using 2K resolution (SN: 90) and 4 active regions using 1K resolution (SN: 58) SDO images on the visible solar disk.
Region 12468 [S15W53] decayed slowly and quietly.
Region 12469 [N18W27] was mostly quiet and stable.
Region 12470 [N13W10] was inactive and in slow decay.
Spotted regions not numbered (or interpreted differently) by SWPC:
S4956 [N11W45] lost the leader spots while a trailer spot became large
enough to be counted at 1K resolution.
S4971 [N14E39] reemerged with tiny spots.
An active region at or just behind the northeast limb has produced several flares late on December 19 and early on December 20. The region could produce M class flares and will likely rotate into view today.
C2+ flares:
| Magnitude | Peak time (UTC) | Location | AR | Recorded by | Comment |
| C3.1 | 02:04 | S18W39 | 12468 | GOES15 | some contribution from event in AR 12465 at the southwest limb |
| C4.5 (LDE) | 22:28 | N05E90 | GOES15 |
December 17-19: No obviously Earth directed CMEs were observed in available LASCO imagery.
[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]
No obvious coronal holes are currently in or near Earth facing positions.
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 to fair.
The geomagnetic field is expected to be unsettled to major storm on December 20 due to CME effects becoming quiet to unsettled on December 21. Quiet conditions are likely on December 22.
| 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.
(Click on image for 2K resolution).
4K resolution.
Compare to the previous day's image.
As of December 12,
2015, the active region maps are based on image products from semi-automated
sunspot counting at 4K resolution.
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 | ||||||||||
| 12468 |
2015.12.09 2015.12.10 |
1 | 2 | 1 | S15W54 | 0010 | AXX | AXX |
 |
 |
|
| S4956 | 2015.12.11 | 1 | 1 | N11W45 | 0004 | AXX |
 |
 |
|||
| 12469 |
2015.12.11 2015.12.12 |
1 | 6 | 1 | N19W28 | 0000 | AXX | CRO |
 |
 |
area: 0015 |
| 12470 | 2015.12.12 | 12 | 29 | 15 | N14W08 | 0450 | EHO | EHO |
 |
 |
area: 0780 location: N13W10 |
| 12471 | 2015.12.14 | S21W26 | |||||||||
| S4968 | 2015.12.15 | N22E26 | |||||||||
| S4969 | 2015.12.16 | S16E34 | |||||||||
| S4970 | 2015.12.16 | S26E05 | |||||||||
| S4971 | 2015.12.18 | 2 | N14E39 | 0004 | BXO |
 |
|||||
| S4972 | 2015.12.18 | N29W17 |
 |
||||||||
| Total spot count: | 14 | 40 | 18 | ||||||||
| Sunspot number: | 44 | 90 | 58 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 24 | 53 | 31 | (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): | 48 | 50 | 49 | k * (sunspot number) As of July 1, 2015: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.85 for MSN 1K (MSN=Magnetic Sunspot Number) |
|||||||
| Month | Average solar flux | International sunspot number (WDC-SILSO) (4) |
Smoothed sunspot number (4) | Average
ap (3) |
|
|---|---|---|---|---|---|
| Measured | 1 AU | ||||
| 2014.02 | 170.3 (cycle peak) |
166.3 | 146.1 (cycle peak) | 110.5 (+1.2) | 10.70 |
| 2014.04 | 143.9 | 144.8 | 112.5 | 116.4 (+2.1) (solar max) | 7.88 |
| 2014.10 | 153.4 | 152.9 | 90.0 | 97.3 (-4.6) | 8.96 |
| 2014.11 | 154.8 | 151.4 | 103.6 | 94.7 (-2.6) | 9.33 |
| 2014.12 | 158.7 | 153.8 | 112.9 | 92.2 (-2.5) | 11.24 |
| 2015.01 | 141.9 | 137.3 | 93.0 | 89.3 (-2.9) | 9.46 |
| 2015.02 | 129.1 | 126.0 | 66.7 | 86.1 (-3.2) | 9.92 |
| 2015.03 | 125.9 | 124.6 | 54.5 | 82.2 (-3.9) | 16.14 |
| 2015.04 | 128.8 | 129.7 | 75.3 | 78.9 (-3.3) | 10.73 |
| 2015.05 | 120.0 | 122.6 | 88.8 | 76.0 (-2.9) | 8.29 |
| 2015.06 | 122.3 | 126.1 | 66.5 | (72.1 projected, -3.9) | 13.15 |
| 2015.07 | 107.0 | 110.8 | 66.4 | (68.4 projected, -3.7) | 8.83 |
| 2015.08 | 105.4 | 108.0 | 64.6 | (67.2 projected, -1.2) | 14.58 |
| 2015.09 | 101.7 | 102.7 | 78.1 | (67.4 projected, +0.2) | 15.78 |
| 2015.10 | 104.1 | 103.3 | 61.7 | (66.5 projected, -0.9) | 14.02 |
| 2015.11 | 109.3 | 106.9 | 63.2 | (64.5 projected, -2.0) | 12.09 |
| 2015.12 | (110.2) | 34.0 (2A) / 55.5 (2B) / 70.0 (2C) | (62.7 projected, -1.8) | (10.9) | |
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).
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.
4) Updated to new data set from WDC-SILSO on July 1, 2015
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 Universal Time. Comments and suggestions are always welcome.
SDO images are courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.
