Space Weather
Space weather describes changing environmental conditions in near-Earth space. Magnetic fields, radiation, particles and matter, which have been ejected from the Sun, can interact with the Earth’s upper atmosphere and surrounding magnetic field to produce a variety of effects.
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Aurora forecasts
Northern Hemisphere
Increased auroral activity is possible early on 17 Sep due to a potential glancing Coronal Mass Ejection arrival. Should this occur then aurora may become visible (where skies are clear) from the north of Scotland and similar magnetic latitudes. From Thursday night onwards aurora levels are expected to decline to background levels.
Southern Hemisphere
Increased auroral activity is possible on 17 Sep due to a potential glancing Coronal Mass Ejection (CME) arrival. Should this occur then aurora may become visible (where skies are clear) from the far south of South Island, New Zealand and slight chance of sightings across Tasmania. From Thursday night onwards aurora levels are expected to decline to background levels.
Issued at: 04:08 (GMT) on Thu 17 Sep 2026
Forecast overview
Space Weather Forecast Headline: Chance of G1/Minor Geomagnetic Storms Day 1 (17 Sep).
Analysis of Space Weather Activity over past 24 hours
Solar Activity: Solar activity has been Very Low, with no significant flares observed. There are currently three sunspot regions on the visible disc, all fairly simple unipolar spots located in the west.
There were no Earth directed CMEs observed during the period.
Solar Wind / Geomagnetic Activity: Solar winds, as measured at L1 by SOLAR-1, indicated a mixture of effects from coronal hole fast winds and coronal mass ejections. Solar wind speeds have been generally Elevated, mostly 500-550km/s, with a peak of 578km/s at 16/1244 UTC. The Interplanetary Magnetic Field, Bt, was Moderate at first. It then decreased to Weak from around 16/0445 UTC and has been fairly stable since then. The north-south component, Bz, was Moderate and positive to start, before becoming generally weak (but staying mostly positive) from 16/0145 UTC. Geomagnetic activity has been Quiet to Unsettled (Kp 0-3).
Energetic Particles / Solar Radiation: GOES18 >10MeV proton flux was at normal background levels.
Four-Day Space Weather Forecast Summary
Solar Activity: Solar activity is expected to remain Very Low or Low with only a very slight chance of reaching Moderate levels should any isolated Moderate-class flares occur.
Solar Wind / Geomagnetic Activity: A moderately-fast Coronal Mass Ejection that left the Sun on 14 Sep may pass ahead of Earth orbit early Day 1 (17 Sep), but may give a glancing impact.
Recent increases in solar wind speeds are likely due to the connection to the fast wind of a large, elongated coronal hole in the northern hemisphere. Predominantly Elevated or Strong speeds are expected through Day 1 (17 Sep) and possibly Day 2 (18 Sep) before slowly declining thereafter as the high-speed stream eases.
Geomagnetic activity is expected to be mainly Quiet to Unsettled on Day 1 (17 Sep), with a chance of reaching Active (Kp4) or G1/Minor (Kp5) storming levels should any potential Coronal Mass Ejection arrival combine with ongoing coronal hole effects. Days 2-4 (18-20 Sep) should see a return to persistently Quiet or Unsettled levels (Kp 1-3).
Energetic Particles / Solar Radiation: GOES18 >10MeV proton flux is at background levels and not expected to change significantly during the forecast period.
Issued at: 00:11 (GMT) on Thu 17 Sep 2026
Solar imagery
SDO AIA-193
This channel highlights the outer atmosphere of the Sun - called the corona - as well as hot flare plasma. Hot active regions, solar flares, and coronal mass ejections will appear bright here. The dark areas - called coronal holes - are places where very little radiation is emitted, yet are the main source of solar wind particles.
Issued at:
SDO AIA-304
This channel is especially good at showing areas where cooler dense plumes of plasma (filaments and prominences) are located above the visible surface of the Sun. Many of these features either can't be seen or appear as dark lines in the other channels. The bright areas show places where the plasma has a high density.
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