The geomagnetic field was quiet to severe storm on September 20. Solar wind speed at SOHO ranged between 441 and 642 km/s. A fairly strong solar wind shock was observed at 05:32 at SOHO, the arrival of the CME observed on September 18. The CME arrived much earlier than predicted and caused a stronger than expected geomagnetic disturbance.
Solar flux at 23h UTC on 2.8 GHz was 102.9 (decreasing 24.8 over the last solar rotation, the measurement at 20h UTC was enhanced by an LDE in AR 12415). The 90 day 10.7 flux at 1 AU was 105.8. The Potsdam WDC planetary A index was 38 (STAR Ap - based on the mean of three hour interval ap indices: 37.5). Three hour interval K indices: 35754523 (planetary), 25554423 (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 8 active regions using 2K resolution (SN: 155) and 7 active regions using 1K resolution (SN: 114) SDO images on the visible solar disk.
Region 12415 [S19W51] decayed slowly and was the
source of the largest x-ray event of the day.
Region 12418 [S15W21] gained small spots and was quiet.
Region 12419 [N12W17] decayed slowly and quietly.
New region 12420 [N09E77] rotated partially into view on September 19 and
was numbered the next day by SWPC. The region could produce further M class
events.
Spotted regions not numbered (or interpreted differently) by SWPC:
S4765 [S19W59] decayed slowly and quietly.
S4766 [N20E29] reemerged with penumbra spots.
New region S4771 [N13E59] emerged early in the day with several
spots, then decayed.
New region S4772 [S12E10] was observed with
penumbra spots.
C2+ flares:
| Magnitude | Peak time (UTC) | Location | AR | Recorded by | Comment |
| M1.5 (LDE) | 05:03 | N10E90 | 12420 | GOES15 | |
| C2.6 | 09:34 | N09E85 | 12420 | GOES15 | C1.7 @ 09:32 @ SDO/EVE. Attributed to AR 12415 by SWPC |
| C2.2 | 16:28 | S4765 | SDO/EVE | ||
| M2.1/2N (LDE) | 17:57 | S20W24 | 12415 | GOES15 | Type II & IV radio sweeps. Partial halo CME M2.5 @ 18:02 @ SDO/EVE. X-ray emissions returned to background levels after 22:50 UT |
| C2.3 | 20:49 | N08E80 | 12420 | SDO/EVE |
September 20: A partial halo CME was observed after an M2 LDE in AR
12415. It is uncertain if this CME has any Earth directed components.
September 19: No obviously Earth directed CMEs were observed in
available LASCO imagery.
September 18: A CME was observed off the south pole and parts of the
southwest and southeast limbs after the C2 LDE in AR 12415.
[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 (CH691) will rotate across the central meridian on September 21-22.
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 September 21 due to lingering CME. Quiet conditions are likely on September 22-23 with some uncertainty for September 23 should the CME observed on September 20 reach Earth. Effects from CH691 could cause quiet to minor storm conditions on September 24-25.
| 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.
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 | ||||||||||
| 12415 | 2015.09.10 2015.09.11 |
12 | 10 | 5 | S19W56 | 0240 | EAC | DAO |
 |
 |
area: 0130 location: S19W51 SWPC data includes AR S4765 |
| S4752 | 2015.09.11 | S01W55 | |||||||||
| 12418 | 2015.09.12 2015.09.13 |
5 | 19 | 9 | S15W21 | 0210 | CAO | CHO | images/AR_12418_20150920_2345.png | images/AR_12418_20150919_2345.png | area: 0270 |
| 12419 | 2015.09.13 2015.09.15 |
5 | 9 | 5 | N12W19 | 0030 | CAO | CRO |
 |
 |
location: N12W17 |
| S4761 | 2015.09.16 | N23W06 | |||||||||
| S4763 | 2015.09.17 | S27W34 | |||||||||
| S4765 | 2015.09.18 | 6 | 3 | S19W59 | 0100 | CAO |
 |
 |
|||
| S4766 | 2015.09.18 | 5 | 1 | N20E29 | images/AR_S4766_20150920_2345.png | ||||||
| S4767 | 2015.09.18 | S27E08 | |||||||||
| 12420 | 2015.09.19 2015.09.20 |
12 | 20 | 9 | N09E71 | 0270 | EKC | EKC |
 |
 |
area: 0420 location: N09E76 |
| S4771 | 2015.09.20 | 1 | N13E59 | 0001 | AXX |
 |
|||||
| S4772 | 2015.09.20 | 5 | 2 | S12E10 | 0010 | BXO |
 |
||||
| Total spot count: | 34 | 75 | 34 | ||||||||
| Sunspot number: | 74 | 155 | 114 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 59 | 108 | 67 | (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): | 81 | 85 | 97 | 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 |
| 2014.05 | 129.7 | 132.9 | 112.5 | 115.0 (-1.4) | 5.75 |
| 2014.06 | 122.0 | 125.8 | 102.9 | 114.1 (-0.9) | 6.72 |
| 2014.07 | 137.4 | 141.8 | 100.2 | 112.6 (-1.5) | 4.50 |
| 2014.08 | 124.7 | 127.9 | 106.9 | 108.3 (-4.3) | 7.71 |
| 2014.09 | 146.6 | 148.1 | 130.0 | 101.9 (-6.4) | 9.78 |
| 2014.10 | 153.4 | 152.9 | 90.0 | 97.4 (-4.5) | 8.96 |
| 2014.11 | 154.8 | 151.4 | 103.6 | 95.0 (-2.4) | 9.33 |
| 2014.12 | 158.7 | 153.8 | 112.9 | 92.6 (-2.4) | 11.24 |
| 2015.01 | 141.9 | 137.3 | 93.0 | 89.8 (-2.8) | 9.46 |
| 2015.02 | 129.1 | 126.0 | 66.7 | 86.6 (-3.2) | 9.92 |
| 2015.03 | 125.9 | 124.6 | 54.5 | (82.1 projected, -4.5) | 16.14 |
| 2015.04 | 128.8 | 129.7 | 78.0 | (78.0 projected, -4.1) | 10.73 |
| 2015.05 | 120.0 | 122.6 | 90.0 | (75.3 projected, -2.7) | 8.29 |
| 2015.06 | 122.3 | 126.1 | 68.3 | (71.6 projected, -3.7) | 13.15 |
| 2015.07 | 107.0 | 110.8 | 66.4 | (67.9 projected, -3.7) | 8.83 |
| 2015.08 | 105.4 | 108.0 | 64.6 | (66.7 projected, -1.2) | 14.58 |
| 2015.09 | (93.7) | 36.4 (2A) / 54.6 (2B) / 70.1 (2C) | (67.0 projected, +0.3) | (18.8) | |
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.
