The geomagnetic field was quiet to active on September 4 under the influence of effects from CH822. Solar wind speed at SOHO ranged between 447 and 564 km/s.
Solar flux at 17h UTC on 2.8 GHz was 134.0 (increasing 62.9 over the previous solar rotation. The measurement at 20h UT was strongly flare enhanced and should be discarded). The average 90 day 10.7 flux at 1 AU was 80.5. The Potsdam WDC planetary A index was 14 (STAR Ap - based on the mean of three hour interval ap indices: 14.3). Three hour interval K indices: 43221234 (planetary), 44222344 (Boulder)
The background x-ray flux is at the class C2 level.
At the time of counting spots (see image time), spots were observed in 6 active regions using 2K resolution (SN: 223) and in 6 active regions using 1K resolution (SN: 141) SDO images on the visible solar disk.
Region 12673 [S09W15] developed further and has a
double sandwich of opposite polarity areas in the southeastern section of the
huge main penumbra. The potential for X class flaring and proton flares is high
given the very strong magnetic delta. There is a high risk of further Earth
directed CMEs from this region over the next few days.
Region 12674 [N13W00] decayed slowly and quietly.
Region 12675 [S06W75] decayed slowly and quietly.
Region 12676 [S10W64] was quiet and stable.
Region 12677 [N17E53] was quiet and stable.
Spotted regions not numbered (or interpreted differently)
by SWPC:
New region
S5789 [N10E59] emerged with tiny spots.
C2+ flares:
| Magnitude | Peak time (UT) | Location | AR | Recorded by | Comment |
| M1.2/1F | 05:49 | S10W04 | 12673 | GOES15 | |
| C2.9 | 08:19 | 12673 | GOES15 | ||
| C2.4 | 11:38 | S08W08 | 12673 | GOES15 | |
| C8.3/1F | 12:25 | S07W08 | 12673 | GOES15 | |
| M1.5/1N | 15:30 | S06W13 | 12673 | GOES15 | |
| C4.1 | 16:46 | 12673 | GOES15 | ||
| C6.0 | 17:39 | S09W10 | 12673 | GOES15 | |
| M1.0 | 18:22 | 12673 | GOES15 | ||
| M1.7 | 19:37 | 12673 | GOES15 | ||
| M5.5/3B | 20:33 | 12673 | GOES15 | Fast, very wide Earth directed full halo CME. Moderate proton event | |
| M2.1 | 22:14 | 12673 | GOES15 |
September 2-3: No obviously Earth directed CMEs were observed in available
LASCO imagery.
September 4: A fast full halo CME was observed starting at 20:06 UT in LASCO
C3 imagery. This CME will likely reach Earth on September 6 and cause a very
strong geomagnetic disturbance.
[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 southern hemisphere coronal hole (CH823) will be in an Earth facing position on September 4-5.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over upper middle latitudes is very poor due to a proton event, propagation could be affected for weeks to come. Propagation on long distance northeast-southwest paths is poor to fair.
The geomagnetic field is expected to be quiet to active on September 5 due to effects from CH822. September 6 could start with quiet conditions. When the CME observed on September 4 arrives we could see minor to severe geomagnetic storming lasting until September 8.
| 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.
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 overlays |
Comment | ||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| SWPC | Magnetic (SDO) |
SWPC | STAR | Current | Previous | ||||||
| 2K | 1K | ||||||||||
| 12673 |
2017.08.28 2017.08.29 |
28 | 68 | 36 | S08W16 | 0680 | DKC | DKC |
 |
 |
area: 1060 beta-gamma-delta |
| 12674 |
2017.08.28 2017.08.29 |
34 | 61 | 31 | N14W01 | 0740 | FHI | FHC |
 |
 |
area: 0870 beta-gamma |
| 12675 |
2017.08.29 2017.08.31 |
4 | 6 | 3 | S02W76 | 0010 | BXO | CRO |
 |
 |
area: 0030 |
| 12676 |
2017.08.31 2017.09.02 |
4 | 11 | 6 | S09W65 | 0030 | CRO | ERI |
 |
 |
area: 0050 |
| 12677 |
2017.09.02 2017.09.03 |
2 | 14 | 4 | N19E51 | 0010 | AXX | CRO |
 |
 |
area: 0030 location: N17E53 |
| S5788 | 2017.09.02 | S10E30 | |||||||||
| S5789 | 2017.09.04 | 3 | 1 | N10E59 | 0006 | BXO |
 |
||||
| Total spot count: | 72 | 163 | 81 | ||||||||
| Sunspot number: | 112 | 223 | 131 | (total spot count + 10 * number of spotted regions) | |||||||
| Weighted SN: | 95 | 193 | 110 | (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): | 123 | 123 | 105 | k * (sunspot number) As of May 7, 2016: k = 1.1 for SWPC, k = 0.55 for MSN 2K, k = 0.80 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 |
| 2016.04 | 93.3 | 94.0 | 38.0 | 47.8 (-2.7) | 9.03 |
| 2016.05 | 93.0 | 95.3 | 52.1 | 44.9 (-2.9) | 11.65 |
| 2016.06 | 81.9 | 84.5 | 20.9 | 41.6 (-3.3) | 8.44 |
| 2016.07 | 86.0 | 88.9 | 32.5 | 38.6 (-3.0) | 9.43 |
| 2016.08 | 85.0 | 87.1 | 50.7 | 36.0 (-2.6) | 9.61 |
| 2016.09 | 87.7 | 88.7 | 44.7 | 33.3 (-2.7) | 14.54 |
| 2016.10 | 86.1 | 85.6 | 33.6 | 31.4 (-1.9) | 15.33 |
| 2016.11 | 78.6 | 76.9 | 21.4 | 29.9 (-1.5) | 9.11 |
| 2016.12 | 75.1 | 72.8 | 18.9 | 28.5 (-1.4) | 9.34 |
| 2017.01 | 77.3 | 74.9 | 25.8 | 27.9 (-0.6) | 9.45 |
| 2017.02 | 76.8 | 75.0 | 26.1 | 26.6 (-1.3) | 9.58 |
| 2017.03 | 74.6 | 73.9 | 17.7 | (25.0 projected, -1.6) | 14.20 |
| 2017.04 | 80.3 | 80.8 | 32.6 | (23.4 projected, -1.6) | 11.70 |
| 2017.05 | 73.6 | 75.2 | 18.8 | (22.3 projected, -1.1) | 8.09 |
| 2017.06 | 74.7 | 77.1 | 19.4 | (21.3 projected, -1.0) | 6.08 |
| 2017.07 | 77.4 | 79.9 | 18.3 | (20.2 projected, -1.1) | 8.97 |
| 2017.08 | 77.9 | 79.8 | 33.1 | (18.7 projected, -1.5) | 10.1 |
| 2017.09 | (111.9) | 11.3 (2A) / 87.8 (2B) / 40.0 (2C) | (17.5 projected, -1.2) | (14.2) | |
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.
