Last major update issued on April 21, 2015 at 05:00 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 April 10, 2015]
[Presentations:
3rd SSN Workshop, Tucson, 2013 (pdf)
/
4th SSN Workshop, Locarno, 2014]
The geomagnetic field was quiet to unsettled on April 20. Solar wind speed at SOHO ranged between 354 and 437 km/s. A high speed stream associated with CH664 arrived late in the day and early on April 21.
Solar flux at 20h UTC on 2.8 GHz was 149.7 (increasing 16.7 over the last solar rotation). The 90 day 10.7 flux at 1 AU was 128.2. The Potsdam WDC planetary A index was 9 (STAR Ap - based on the mean of three hour interval ap indices: 8.8). Three hour interval K indices: 33112133 (planetary), 33123203 (Boulder).
The background x-ray flux is at the class B8 level.
At the time of counting spots (see image time), spots were observed in 16 active regions using 2K resolution (SN: 324) and 14 active regions using 1K resolution (SN: 215) SDO images on the visible solar disk.
Region 12321 [N12W52] decayed quickly and was quiet.
Region 12324 [N19W18] was quiet and stable.
Region 12325 [N04W11] was mostly unchanged and quiet.
Region 12326 [N15W36] was quiet and stable.
Region 12327 [S09E30] was quiet and stable.
Region 12329 [S07W62] gained spots and was quiet.
New region 12330 [N16E32] emerged on April 19 and was numbered by SWPC
the next day as the region began to decay.
Spotted regions not numbered (or interpreted
differently) by SWPC:
S4367 [N08W43] decayed slowly and quietly.
S4383 [S12E12] was quiet and stable.
S4389 [S22E38] was quiet and stable.
S4390 [S10E23] reemerged with several penumbra spots.
S4392 [N11W72] developed relatively quickly as new flux emerged and
became a compact region with a small magnetic delta. A minor M class flare is
possible.
S4394 [S10W09] decayed slowly and quietly.
S4398 [N08E22] decayed slowly and quietly.
New region S4400 [N09E38] emerged with a penumbra
spot.
New region S4401 [N20W40] emerged with a few penumbra spots.
| Magnitude | Peak time (UTC) | Location | AR | Recorded by | Comment |
| C2.4 (LDE) | 21:16 | NE limb | GOES15 | attributed to AR 12321 by SWPC |
April 18-20: No obviously Earth directed CMEs were observed.
[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 southern hemisphere coronal hole (CH664) rotated across the central meridian on April 16-18.
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 quiet to unsettled on April 21-23 with a chance of active intervals on April 21 due to effects from CH664.
| 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) 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 | ||||||||||
| 12322 | 2015.04.10 2015.04.11 |
3 | N11W71 | 0030 | CRO |
spotless location: N13W79 SWPC has moved AR 12322 to the location of AR S4392 |
|||||
| 12321 | 2015.04.10 2015.04.11 |
9 | 8 | 2 | N10W49 | 0080 | CSO | BXO |
 |
 |
area: 0020 location: N12W52 |
| S4367 | 2015.04.11 | 10 | 1 | N08W43 | 0070 | CAO |
 |
 |
|||
| 12326 | 2015.04.11 2015.04.16 |
1 | 4 | 3 | N15W41 | 0010 | AXX | BXO |
 |
 |
location: N15W36 |
| 12324 | 2015.04.13 2015.04.14 |
9 | 25 | 18 | N19W18 | 0230 | DKI | CAI |
 |
 |
|
| S4372 | 2015.04.13 | S18W51 | |||||||||
| 12325 | 2015.04.13 2015.04.14 |
8 | 22 | 11 | N05W09 | 0220 | CKO | DKO |
 |
 |
area: 0360 location: N04W11 |
| S4375 | 2015.04.13 | N10W56 | |||||||||
| S4380 | 2015.04.15 | S13W27 |
 |
||||||||
| S4381 | 2015.04.15 | N18W36 | |||||||||
| S4383 | 2015.04.16 | 13 | 6 | S12E12 | 0035 | BXO |
 |
 |
|||
| 12327 | 2015.04.16 2015.04.17 |
4 | 15 | 4 | S09E30 | 0110 | CSO | CSO |
 |
 |
|
| S4385 | 2015.04.16 | S18W45 |
 |
||||||||
| S4388 | 2015.04.17 | N17W57 | |||||||||
| S4389 | 2015.04.17 | 4 | 1 | S22E38 | 0008 | BXO |
 |
 |
|||
| S4390 | 2015.04.17 | 7 | 4 | S10E23 | 0025 | BXO |
 |
||||
| 12329 | 2015.04.17 2015.04.19 |
8 | 26 | 10 | S08W62 | 0030 | CRO | DRI |
 |
 |
|
| S4392 | 2015.04.17 | 13 | 9 | N11W72 | 0170 | DAC |
 |
 |
beta-gamma-delta | ||
| S4394 | 2015.04.18 | 2 | S10W09 | 0012 | AXX |
 |
 |
||||
| S4395 | 2015.04.18 | S15W50 | |||||||||
| 12330 | 2015.04.19 2015.04.20 |
3 | 9 | 5 | N15E32 | 0030 | DSO | BXO |
 |
 |
|
| S4398 | 2015.04.19 | 1 | N08E22 | 0003 | AXX |
 |
 |
||||
| S4400 | 2015.04.20 | 1 | 1 | N09E38 | 0003 | AXX |
 |
||||
| S4401 | 2015.04.20 | 3 | 2 | N20W40 | 0008 | BXO |
 |
||||
| Total spot count: | 45 | 164 | 75 | ||||||||
| Sunspot number: | 125 | 324 | 215 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 86 | 197 | 108 | (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): | 75 | 113 | 118 | 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 (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 | 125.9 | 124.6 | 38.4 | (56.1 projected, -2.3) | 16.14 |
| 2015.04 | (131.0) | 47.9 (2A) / 71.9 (2B) / 82.8 (2C) | (53.4 projected, -2.7) | (11.9) | |
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). 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.
