Coronal hole, weak shock passage, filaments

Tuesday, 31 March 2015 18:06 UTC

Weak shock passage

An unknown shock passage of what could be an undetected coronal mass ejection was observed at ACE around 7:40 UTC this morning. Geomagnetic storming has not been observed and if we consider the current solar wind and IMF conditions, it is also unlikely that we will see a geomagnetic storm in the hours ahead. The solar wind speed is below the 400 km/s, just shy of background speeds but it is worth noting that the strength of the IMF (Bt) remains above average. Enhanced auroral displays are still possible in the hours ahead at high latitude locations.

Image: The signature of a clear shock passage around 7:40 UTC seen here on data from ACE.

Coronal hole facing Earth

We thus didn't see much from the southern polar coronal hole but another coronal hole is facing Earth and this northern hemisphere coronal hole has a transequatorial portion meaning it is more than likely that we will see an enhanced solar wind stream at Earth from this coronal hole. The solar wind stream could arrive as early as Thursday.

Image: Composite image by NASA SDO showing the dark coronal hole and two filaments on the Sun.

Something else that is well worth keeping an eye on are two filament channels that are trailing this coronal hole. Should one of these filaments become unstable and erupt, it is very much possible that the resulting coronal mass ejection has an Earth-directed component. Something to keep an eye on in the days ahead!