Abstract
We propose a new technique for energizing coronal magnetic equilibria
toward eruptions. We achieve this via a sequence of MHD relaxations of
small line-tied pulses of magnetic helicity, each of which is simulated
by a suitable rescaling of the current-carrying part of the field. The
whole procedure is ‘magnetogram-matching’ because it involves no changes
to the normal component of the field at the lower boundary. The
technique is illustrated by application to bipolar force-free
configurations whose magnetic flux ropes (MFRs) are modeled with our
regularized Biot-Savart law method. We have found that, in spite of the
bipolar character of the ambient potential field in these examples, the
resulting MFR eruption is generally sustained by two reconnection
processes. The first, which we refer to as breakthrough reconnection, is
analogous to breakout reconnection in quadrupolar configurations. It
occurs at a quasi-separator field line located inside the current layer
that wraps around the erupting MFR, and results from taking into account
the line-tying effect at the photosphere. The second process is the
classical tether-cutting reconnection that develops at the second
quasi-separator inside a vertical current layer formed below the
erupting MFR. Both reconnection processes work in tandem to propel the
MFR through the overlying ambient field. The considered examples suggest
that our technique will be beneficial for both the modeling of
particular eruptive events and theoretical studies of eruptions in
idealized magnetic configurations. This research was supported by NASA
programs HTMS (award no. 80NSSC20K1274) and HSR (80NSSC19K0858 and
80NSSC20K1317); NASA/ NSF program DRIVE (80NSSC20K0604); and NSF grants
AGS-1923377 and ICER-1854790.