Space Weather Prediction Center (SWPC) issued a G3 – Strong geomagnetic storm watch for June 8, as a partial halo CME from a June 6 solar flare is forecast to reach Earth around midday UTC. A G2 – Moderate geomagnetic storm watch is also in effect for June 9, as storming is expected to continue into the early part of the day.
SWPC’s 3-Day Forecast, issued at 12:30 UTC on June 7, forecasts the highest 3-hour Kp index of the June 7–9 period at 7.00, corresponding to NOAA Scale G3, during the 18:00–21:00 UTC period on June 8. The forecast calls for G2 conditions during the 21:00–00:00 UTC period on June 8 and the 00:00–03:00 UTC period on June 9. G1 – Minor geomagnetic storm periods are forecast earlier on June 8 and through the morning of June 9.
The CME was associated with an M1.8 flare at 14:01 UTC on June 6 from Region 4461. The event produced an F10.7 cm radio burst of 190 sfu, an approximately 11-degree-long filament eruption centered near S25E28, and a Type II radio sweep with an estimated speed of 838 km/s.
The resulting partial halo CME was first observed in LASCO C2 coronagraph imagery at 14:01 UTC on June 6 and is expected to arrive at Earth around midday UTC on June 8.
Solar activity reached moderate levels in 24 hours to 12:30 UTC on June 7. Region 4456, located at N17W41, produced a C8.8 flare at 13:18 UTC on June 6 and continued to evolve. SWPC said the region gained additional spots with an asymmetric penumbra and a weak delta signature in its intermediate area.
New spots also formed north of Region 4462, located at N16E12, but had not been numbered by SWPC pending corroborating solar observatory reports.
Pre-arrival solar wind conditions were declining on June 7. Total interplanetary magnetic field strength of 4–5 nT, with the Bz component showing brief southward deflections to -4 to -5 nT. Solar wind speed declined from about 600 km/s (373 miles/s) to about 450 km/s (280 miles/s), while geomagnetic field activity remained at quiet to active levels.
The current solar wind regime is expected to continue weakening through June 7 before a disturbed environment returns early to mid UTC-day on June 8.
The CME shock arrival is forecast to bring enhanced magnetic field strength and much faster solar wind speeds. Enhanced conditions are expected to continue into June 9 before a waning trend begins by mid UTC-day.
The greater than 2 MeV electron flux at geosynchronous orbit reached high levels, with a peak flux of 1 280 pfu at 17:10 UTC on June 6. The greater than 10 MeV proton flux became enhanced after 15:15 UTC on June 6, following the M1.8 flare event.
The greater than 10 MeV proton flux is expected to remain at background levels, although SWPC gives a chance for an S1 – Minor solar radiation storm on June 8 during the CME shock arrival. The 3-Day Forecast gives the chance of S1 or greater solar radiation storms as 15% on June 7, 25% on June 8, and 10% on June 9.
There’s a 55% chance of M-class flares on each day from June 7 through June 9, with a 10% chance of X-class on each of those days.
At G3 – Strong geomagnetic storm levels, voltage corrections may be required on power systems, and false alarms may be triggered on some protection devices. Surface charging may occur on satellite components, drag may increase on low-Earth-orbit satellites, and orientation corrections may be needed.
Intermittent satellite navigation and low-frequency radio navigation problems are possible, as well as intermittent HF radio problems, and aurora as far equatorward as Illinois and Oregon under past G3 conditions.
The UK Met Office also forecasts CME arrival on June 8, describing the CME as relatively fast and wide, with an Earth-directed component while the bulk of the material passes south and east of Earth.
Its space weather forecast calls for a chance of G3 – Strong geomagnetic storm conditions on June 8, easing to G1 – Minor to G2 – Moderate conditions on June 9 before mainly quiet geomagnetic activity resumes later in the four-day period.
The Met Office expects enhanced aurora across Canada and the northern United States, with some chance of visible aurora at northernmost geomagnetic latitudes in Europe before activity eases. In the Southern Hemisphere, aurora visibility may extend to southern New Zealand and possibly Tasmania.
Storm intensity will depend on CME arrival time and magnetic field orientation after shock arrival. A stronger and prolonged southward Bz would support a higher geomagnetic response, while a weaker or less geoeffective magnetic configuration would reduce realized storm levels.
References:
1 Forecast Discussion – NOAA/SWPC – 12:30 UTC on June 7, 2026