Description
Organisers: Alexander Russell, Jonathan Eastwood, Gunnar Hornig, James McLaughlin, Christopher Prior, Julia Stawarz, Peter Wyper, Anthony Yeates
Magnetic reconnection is one of the most important processes in solar, space and astrophysical plasmas. In a highly conducting plasma with large length scales, magnetic field connections between plasma elements are conserved, allowing the accumulation of magnetic energy over time. However, conservation of connectivity can break down in small volumes โ this has global consequences, for example enabling rapid conversion of magnetic energy in solar flares, auroral substorms and astrophysical jets and disks.
This session aims to bring together researchers working on magnetic reconnection, magnetic topology and resistive and collisionless instabilities, from the solar, space and astrophysics communities. Cross-cutting scientific discussions will cover theory, simulations, remote observations and in-situ observations.
Some of the key questions we are interested in addressing are:
o What do the latest numerical simulations and observations reveal about reconnection and non-ideal instabilities?
o How do recent new perspectives on topological properties, such as magnetic skeletons or helicity, shed light on dynamics such as flaring and coronal heating?
o How does turbulence affect reconnection, and vice-versa?
o How have results from the latest missions (e.g. Solar Orbiter and MMS), observatories (e.g. DKIST) and analysis tools (e.g. field line helicity) changed our understanding of these topics?
The Earthโs magnetotail is formed primarily of magnetic field lines that are topologically open, i.e. connected to the interplanetary magnetic field (IMF). During periods of northward-directed IMF, the magnetopause reconnection site moves tailward of the cusps, resulting in either the โstirringโ of magnetic flux without a net change in topology (โsingle lobe reconnectionโ), or the closure of...
Energy transfer in magnetised plasmas is fundamentally shaped by the interplay between turbulence and reconnection. Coherent structures are central to intermittent magnetohydrodynamic turbulence, which is observed in situ in the solar wind. We establish a correspondence between the energy transfer rate and the magnetic topology of underlying turbulent fluctuations. Magnetic field topology is...
Within collisionless turbulent plasmas, intense thin current sheets can undergo magnetic reconnection, playing a crucial role in both turbulence dynamics and energy dissipation. The prevalence of magnetic reconnection may be influenced by the properties of the turbulent fluctuations in different environments. The Magnetospheric Multiscale mission (MMS) provides high-resolution, multi-point...
Magnetic reconnection and plasma turbulence are deeply interlinked processes. The turbulent evolution of magnetic structures lead to the onset of reconnection events and turbulence is present in different regions associated with the reconnection dynamics, e.g., inflow region, exhaust, Ion diffusion region and Electron diffusion region. Plasma turbulence plays a fundamental role because it...
Magnetic reconnection is one of the fundamental dynamical processes in the solar corona. The method of studying reconnection in active region-scale magnetic fields generally depends on non-local methods (i.e. requiring information across the magnetic field under study) of magnetic topology, such as separatrix skeletons and quasi-separatrix layers. The theory of General Magnetic Reconnection is...
The short timescale of the solar flare reconnection process has long proved to be a puzzle. Studies suggest the importance of the formation of plasmoids in the reconnecting current sheet, with quantifying the aspect ratio of the width to length of the current sheet in terms of a negative power $\alpha$ of the Lundquist number, that is, S$^{-\alpha}$, being key to understanding the onset of...
Magnetic null points are regions within a magnetic field where the field strength vanishes and are commonly associated with various forms of heating. A previous study of ours showed that there are interesting restrictions on the flow of heat at null points due to their magnetic geometry. This causes null points to take on strikingly different thermal structures that depend on the form of...
Magnetic reconnection is a fundamental plasma process at the heart of many dynamic events such as solar flares. Despite reconnection events being dynamic, models of reconnection are often based off steady state solutions such as Sweet-Parker reconnection and Pestchek reconnection. In this study we investigate oscillatory reconnection, a time-dependent form of reconnection, and how it compares...
Solar flares are explosive events in which magnetic reconnection rapidly converts stored magnetic energy into bulk motion, plasma heating, and particle acceleration. Observations of solar flare ribbons reveal various fine structures, including wave-like perturbations and spirals, which theory suggests are linked to plasmoids formed via tearing-mode instabilities in the flare current sheet....
Understanding the evolution of the complex magnetic fields found in solar active regions is an active area of research. There are numerous models for such fields which range in their complexity due to the number of known physical effects included in them, the one common factor being they all extrapolate the magnetic field up from the photosphere. In this study we focus on the fact that above...
Magnetic reconnection is of particular importance in space plasmas because of its role in controlling magnetic topology and releasing stored magnetic energy. In situ observations of reconnection complement remote sensing and simulations by directly quantifying the local properties of reconnection as well as providing ground truth of the plasma physical mechanisms of heating and acceleration....
Solar flare ribbons have long been used as a diagnostic of the flare reconnection process, where the surface magnetic flux swept out by the ribbons is used to infer the amount and rate that magnetic flux that is reconnected in the solar corona. However, in recent years fine structures such as โkernelsโ, โspiralsโ and โblobsโ within flare ribbons have been increasingly observed and recognised...
3D direct numerical simulations have recently opened an important new window into the role of self-generated turbulence in magnetic reconnection at high Lundquist numbers. Interestingly, these simulations exhibit features associated with the Lazarian-Vishniac theory (turbulence and field line dispersion) and with 2D plasmoid mediated reconnection (flux ropes and reconnection rates). Motivated...
The accurate forecasting of solar flares is considered a key goal within the solar physics and space weather communities. There is significant potential for flare prediction to be improved by incorporating topological fluxes of magnetogram data sets, without the need to invoke three-dimensional magnetic field extrapolations. Topological quantities such as magnetic helicity and magnetic winding...
This study investigates the impact of different magnetic field extrapolations on particle acceleration and energy release during solar flares. Using magnetograms obtained before a solar flare event, two distinct magnetic field extrapolations were constructed: a force-free model and a non-force-free model. These models represent different assumptions about the balance of magnetic forces in the...
Solar flares are caused by magnetic reconnection in active regions (ARs). Sometimes, similar flares can recur in the same AR, known as homologous flares. This study investigates whether magnetic reconnection follows the same process in two homologous flares of AR12146.
We examined the morphologically similar flare ribbons and diagnosed their magnetic topology using quasi-separatrix layers...
It is well known that the magnetic helicity integral of magnetohydrodynamics is non-unique if the magnetic field passes through the domain boundary. In particular, it depends on the choice of vector potential. In some sense, any choice is equally meaningful, because all are invariant under ideal deformations vanishing on the boundary. However, we propose that some choices are more physically...
A major goal for magnetic reconnection research is to understand reconnection with self-generated turbulence, which appears central to solar flares and other energy releases in solar and space plasmas. In nature, reconnection occurs for a wide range of shear angles, including when upstream magnetic fields are close to antiparallel. Existing numerical studies of 3D self-generated turbulent...
The Omega-effect in the Omega-alpha solar dynamo model is characterised by the horizontally anisotropic flow in the solar tachocline which deforms the large-scale dipole magnetic field into an azimuthal configuration. This anisotropic flow is believed to be shear-driven due to the location of the tachocline between the uniformly rotating radiative zone below and the differentially rotating...
Magnetic reconnection is a fundamental astrophysical process responsible for changing the topology of magnetic fields, releasing magnetic energy, and, in the Sun, facilitating both coronal heating and the onset of solar flares. As such, it is desirable to be able identify the locations at which it occurs, the properties of reconnection sites, and the nature of the change in magnetic...
