The flare itself was not among the highest classes, but it had a prolonged duration and was associated with a coronal mass ejection. It is the CME, rather than the X-ray emission itself, that matters to aurora observers. If the ejected plasma reaches Earth with the right magnetic field configuration, a geomagnetic storm may occur.
The event is associated with an asymmetric halo CME, whose main bulk was directed southeast of the Sun–Earth line. This means we are not dealing with a central impact on the magnetosphere, but rather with possible contact with the ejection’s side flank. Such cases are more difficult to forecast, as the final effect depends on the density, speed and magnetic field orientation in the incoming solar wind.
G3 forecast for June 8 and G2 for June 9
According to the NASA model, the CME may arrive at Earth on June 8 at around 06:00 UTC, or 08:00 CEST, with an uncertainty of about seven hours. The SWPC WSA-Enlil model indicates 12:00 UTC, or 14:00 CEST, also with a margin of plus or minus seven hours. The realistic arrival window for the CME’s side flank therefore falls on Monday, from the morning into the afternoon in Polish time.
SWPC has issued a G3 geomagnetic storm forecast for June 8. A G2 forecast is in effect for Tuesday, June 9, indicating a gradual weakening of the effects after the main disturbance passes. For observers in Poland, the key question will be whether elevated geomagnetic activity persists into the brief period of darker skies after astronomical twilight ends, or at least into deeper twilight in the north of the country.
Model parameters indicate an increase in solar wind speed to around 650 km/s and density to approximately 15 protons per cubic centimetre. A type II radio emission with a speed of 836 km/s was also associated with the flare, confirming the presence of a shock wave in the solar corona. The CME front was recorded by the CCOR-1 coronagraph around half an hour after the flare’s peak, and after another hour its angular extent exceeded 180 degrees.
The ejection is assessed as bright and dense. This is a significant difference compared with the eruptions of June 2 and 3, which also provided grounds for aurora forecasts but produced no visible effect over Poland. In that case, observers’ expectations did not translate into aurora detections from the country, demonstrating the limitations of models when forecasting side-on or less favourably directed CME structures.
Small active region, high forecast uncertainty
The most unusual element of the current situation is the source of the eruption. AR4461 had an area of about 20 MH, making it a very small active region for the source of an event capable of leading to a G3 geomagnetic storm. Even so, it produced an M1.8 flare, distinct coronal dimming and a CME with a large angular extent.
Coronal dimming is an important signal because it indicates the removal of a substantial amount of matter from the solar corona. In practice, this means that the flare may have been followed by a real mass of plasma capable of interacting with Earth’s magnetosphere. The M1.8 class alone does not determine the strength of the storm, because geomagnetic effects are primarily governed by the CME’s structure when it reaches the vicinity of Earth.
According to the NASA model, the travel time is around 40 hours. This is faster than the typical 48–72 hours for many coronal mass ejections, though slower than the most dynamic CMEs of the current solar cycle, for which transit times of around 25 hours have been recorded. The average transit speed cited in the analysis exceeds 1,000 km/s, but the forecast solar wind speed at Earth is lower, which fits a scenario involving an impact from the flank rather than the central part of the ejection.
How to observe the aurora over Poland on the night of June 8–9
In the case of the aurora, there is no single viewing time comparable to an ISS pass or a lunar occultation of a star. The northern horizon should be monitored, especially after the darkest part of the night begins. In June, conditions in Poland are difficult because close to the summer solstice, astronomical night is very short or does not fully occur in the north of the country.
The approximate window of darker skies lasts around two to three hours. The key factor will be whether the rise in geomagnetic activity coincides with this brief period. If the main disturbance passes during the day on June 8, observers may see nothing despite an accurate storm forecast. If elevated activity persists after dark, however, the chance of detecting the aurora will increase.
No telescope is needed for observation. The aurora is an atmospheric phenomenon caused by solar wind particles interacting with Earth’s magnetosphere and upper atmosphere. During a stronger storm, it may be visible to the naked eye as a glow, bands or pillars low above the northern horizon, but under June conditions, a camera or smartphone using night mode will more often reveal the first signs.
The biggest unknown remains the Bz component of the interplanetary magnetic field. For auroras to develop at mid-latitudes, a prolonged period of negative Bz is favourable because it facilitates the transfer of energy from the solar wind to the magnetosphere. Without such a configuration, even a fast and dense stream may produce a weaker visual effect over Poland.
The forecast for June 8 and 9 is therefore another aurora alert, not a guarantee of observations. After the forecasts for June 4 and 5 failed to deliver for Poland, the current CME appears more promising in terms of density and structure, but it still involves an impact from a side flank. The final outcome will only be known once spacecraft monitoring interplanetary space ahead of Earth record changes in the solar wind.