Sun news September 16: Beautiful prominence, auroras tonight?
Today’s top story: Wisps of plasma twirled over the sun’s horizon over the past day, following an eruption on our star’s far side. Meanwhile, we on Earth could see the effect of some previous eruptions later today. Forecasters expect up to two bursts of solar material to reach our magnetic field by this evening, fired by the sun on Sunday and Monday. Combined with an ongoing stream of fast solar wind from a coronal hole, these glancing coronal mass ejections (CMEs) could push geomagnetic conditions to G1 (minor) storm levels, with a chance of G2 (moderate) and even a slight chance of G3 (strong) storms. So aurora watchers around the latitudes of Scotland and possibly northern England should keep an eye on the skies tonight!
Past 24 hours on the sun
(11 UTC September 15 – 11 UTC September 16)
Flare activity: Solar activity continued at very low levels, with only faint B-class flares. Observers counted just two flares, both B-class (weak).
- Strongest flare: A B5.5 peaking at 15:16 UTC on September 15. It came from an unnumbered region on the northeast limb.
- Other notable flares: A B3.6 peaked at 8:14 UTC on September 16 from AR4521.
- Lead flare producer: AR4521 and the unnumbered northeast region ended tied, with one B flare each.
Sunspot regions: Currently, the Earth-viewed solar disk shows two numbered sunspot regions.
- AR4527 (alpha) and AR4528 (alpha): Both numbered regions are magnetically simple, with no relevant activity. They pose little threat of strong flaring.
- No new regions rotated onto the disk during this period. However, the unnumbered spot on the northeast limb that produced the B 5.5 bears watching as it comes into view.
Blasts from the sun? A CME appeared off the northwest limb in SOHO LASCO C2 imagery starting at 16:48 UTC on September 15. Analysts believe it erupted on the far side of the sun, since SDO and GOES SUVI imagery showed no matching eruption on the Earth-facing disk. Observers spotted no new Earth-directed CMEs during the period. However, three earlier CMEs from September 13 and 14 remain in play for Earth impact.
Past 24 hours in space weather
Solar wind: Solar wind conditions were enhanced, likely from the edge of a coronal hole high-speed stream. Speeds showed two sharp, short-lived spikes.
Bt, Bz and magnetic coupling: The total interplanetary magnetic field held strong through most of the period, then dropped to weak strength around 9 UTC this morning. Meanwhile, the north-south component (Bz) pointed mostly northward for much of the period, limiting geomagnetic coupling. Then, around 18:52 UTC on September 15, it swung sharply southward. It stayed south until roughly 0 UTC, then began shifting between south and north in short stretches. At the time of this writing, the Bz points northward.
Earth’s magnetic field: The geomagnetic field ranged from quiet to active levels, with the Kp index reaching 4 (active) at times. Conditions hit the Kp 4 threshold at 0:30 UTC on September 16. Despite the southward Bz swing late in the period, conditions did not reach G1 storm thresholds during this window. Auroras were not widely reported. At the time of this report, the Kp index sits at level 2.
What’s ahead? Sun–Earth forecast
Flare activity forecast: Forecasters expect solar activity to remain at very low to low levels. NOAA’s Space Weather Prediction Center gives a chance for isolated C-class flares through September 18. The SIDC also considers C-class flares likely, at 50% probability or greater. The chance for M-class (moderate) flares edged up slightly, from 5% yesterday to 10% today. Even so, no complex regions sit on the disk to drive stronger activity. X-class chances remain minimal.
Geomagnetic activity forecast:
- September 16: Active to G1 (minor, Kp 5) storm levels are likely, with a chance of G2 (moderate, Kp 6) and a slight chance of G3 (strong, Kp 7). The combined effects of the coronal hole high-speed stream and potential glancing CME arrivals from September 13 are the drivers. Auroras are possible across Scotland and southern New Zealand, with a slight chance of reaching the latitudes of northern England and Tasmania.
- September 17: Lingering fast wind effects and the possible arrival of the September 14 CME could maintain a chance of G1 (minor, Kp 5) conditions, with a slight chance of isolated G2 (moderate, Kp 6) intervals. Aurora remains possible at high latitudes.
- September 18: Expect unsettled to active conditions (Kp 3 to 4) as enhancements wane. A return toward quieter levels should follow. Aurora chances diminish to background.
- September 19: Quiet to unsettled conditions (Kp 0 to 3) are expected as the solar wind returns to near-background levels.
Sun news September 15: Chunk of sun-stuff on its way to Earth
It’s now confirmed: a chunk of sun-stuff fired into space during yesterday’s filament eruption is on its way to Earth. Forecasters anticipate an arrival by September 17, which could trigger G1 (minor) geomagnetic storming and auroras at far-northern latitudes. Meanwhile, the filament that fired the burst continued its fiery activity throughout the past day. Observers have spotted no other coronal mass ejections (CMEs) yet, but this region could send more plasma into space at any moment. Stay tuned.
Past 24 hours on the sun
(11 UTC September 14 – 11 UTC September 15)
Flare activity: Solar activity stayed very low. Observers counted 5 flares: 1 C-class (common) and 4 B-class (weak).
- Strongest flare: A C1.0 peaking at 14:33 UTC on September 14 from active region AR4530.
- Lead flare producer: AR4530 reached the top of the list with three flares: the only C flare of the period plus two B-class flares.
Sunspot regions: The solar disk we see from Earth shows two numbered sunspot regions.
- AR4527 (alpha) and AR4528 (alpha): Both numbered regions are magnetically simple, with no relevant activity.
Blasts from the sun? The filament eruption in the southwest on September 14 hurled a CME into space. After modeling and analysis, specialists confirmed it carries an Earth-directed component, with arrival expected by September 17. Beyond that event, observers spotted no other Earth-directed CMEs in available coronagraph imagery during the past 24 hours.
Past 24 hours in space weather
Solar wind: Solar wind speeds increased from low to moderate levels through the period. A combined effect may explain the rise: a chunk of solar stuff the sun hurled out on September 9, plus fast solar wind from a coronal hole.
Bt, Bz and magnetic coupling: The total interplanetary magnetic field started the period weak. It then climbed, ending the period at strong levels. Meanwhile, the north-south component (Bz) held a mostly northward orientation throughout. Only a couple of faint peaks shifted southward. At the time of this writing, the Bz points north at moderate levels.
Earth’s magnetic field: The geomagnetic field ranged from quiet to active levels, with the Kp at 0-4. Kp reached level 4 at 17:43 UTC on September 14. At the time of this report, the Kp index sits at level 2.
Sun news September 14: Violent filament eruption last night
The solar southwest was lit up last night by a violent filament eruption. The eruption came from the vicinity of sunspot region AR4528, and has been associated with a C1.4 (common) flare at 19:45 UTC. The blast sent a chunk of sun-stuff into space, which could give Earth a glancing blow by early Thursday.
Past 24 hours on the sun
(11 UTC September 13 – 11 UTC September 14)
Flare activity: Very low. Observers counted 2 flares: 1 C-class and 1 B-class (weak).
- Strongest flare: C1.4, peaking at 19:45 UTC on September 13 from an as-yet-unnumbered active region now located in southwest solar quadrant.
- Lead flare producer: The southwestern region and AR4529 were tied for the lead with just one flare each.
Sunspot regions: Currently, the sun shows four numbered regions on its Earth-viewed side. They are grouped to the west of the solar disk, leaving a wide area on the east hemisphere with no active regions at all.
- AR4524 (alpha), AR4527 (alpha), AR4428 (alpha), AR4529 (beta): All regions are magnetically simple and are either stable or slowly decaying.
Blasts from the sun? The abovementioned filament eruption hurled plasma into space at 19:45 UTC on September 13. A glancing blow is anticipated by early September 17. Other than that, observers detected no Earth-directed coronal mass ejections (CMEs) in available coronagraph imagery during the past 24 hours.
Past 24 hours in space weather
Solar wind: Solar wind speeds reached moderate levels through the first half of the period. At around 21 UTC on September 13, conditions started to decrease to background levels.
Bt, Bz and magnetic coupling: The total interplanetary magnetic field was weak. The north-south component (Bz) kept a moderately southward orientation throughout most of the period.
Earth’s magnetic field: The geomagnetic field kept quiet, with the Kp at 0-2.
The sun in recent days
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Bottom line: Sun news September 16, 2026: The sun stayed quiet, but two CMEs are closing in. Geomagnetic storms and auroras are possible later today.
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