A Non-radial Eruption in a Quadrupolar Magnetic Configuration with a Coronal Null

TL;DR

This study analyzes a non-radial solar eruption in a quadrupolar magnetic configuration, revealing the magnetic topology, energy buildup, and reconnection processes that led to a jet-like eruption with an inverted-Y structure.

Contribution

It provides detailed magnetic field extrapolation and analysis of a non-radial eruption in a quadrupolar system, highlighting the role of coronal null points and complex connectivity.

Findings

Ejected plasma followed a highly inclined, non-radial trajectory.

Multiple flare ribbons and reconnection signatures observed near the null point.

Magnetic energy of ~2e31 erg accumulated rapidly in a small bipole.

Abstract

We report one of several homologous non-radial eruptions from NOAA active region (AR) 11158 that are strongly modulated by the local magnetic field as observed with the Solar Dynamic Observatory (SDO). A small bipole emerged in the sunspot complex and subsequently created a quadrupolar flux system. Non-linear force-free field (NLFFF) extrapolation from vector magnetograms reveals its energetic nature: the fast-shearing bipole accumulated ~2e31 erg free energy (10% of AR total) over just one day despite its relatively small magnetic flux (5% of AR total). During the eruption, the ejected plasma followed a highly inclined trajectory, over 60 degrees with respect to the radial direction, forming a jet-like, inverted-Y shaped structure in its wake. Field extrapolation suggests complicated magnetic connectivity with a coronal null point, which is favorable of reconnection between different flux components in the quadrupolar system. Indeed, multiple pairs of flare ribbons brightened simultaneously, and coronal reconnection signatures appeared near the inferred null. Part of the magnetic setting resembles that of a blowout-type jet; the observed inverted-Y structure likely outlines the open field lines along the separatrix surface. Owing to the asymmetrical photospheric flux distribution, the confining magnetic pressure decreases much faster horizontally than upward. This special field geometry likely guided the non-radial eruption during its initial stage.