James Stewart
Gather.town id
SW02
Poster Title
Waves Produced by Merging Magnetic Solar Flux Ropes
Institution
The University of Manchester
Abstract (short summary)
The presence of quasi-periodic pulsations in solar flares, temporary periodic signatures in emitted radiation at different wavelengths, may reveal important information about the energy release process but the origin of this phenomenon is not well understood. One approach to addressing this issue is to develop models of oscillatory reconnection and to explore how reconnection itself may generate oscillatory behavior and waves. To this end, we present the results of 2D magnetohydrodynamic simulations of magnetic reconnection between two twisted magnetic flux ropes, leading to the merger of the flux ropes, and discuss the origins of the resulting periodic pulsations and the waves which are emitted.
Plain text (extended) Summary
Introduction:
Solar flares can be defined as the sudden and intense emission of electromagnetic radiation emitted from the solar atmosphere. This process is characterised by the conversion of stored magnetic energy in complex magnetic structures to kinetic and thermal energy through a process known as magnetic reconnection.
Short-lived temporary periodic oscillations, known as quasiperiodic pulsations (QPPs) are frequently observed in solar flare emissions. Understanding the origin of QPPs and their relation to magnetic reconnection can help develop diagnostic tools that can be used to investigate the conditions inside the solar flare.
Some solar flares occur when plasma loops in the solar corona interact and undergo magnetic reconnection. QPPs are believed to be generated during this process. This scenario can be modelled as the merging of two twisted magnetic flux ropes. This poster discusses simulations performed on two magnetic flux ropes merging and undergoing magnetic reconnection. The aim of these simulations was to study the resulting oscillatory behaviour. During the merging process, waves were emitted away from the reconnection site. The behaviour of these waves is discussed in this poster.
Oscillatory Reconnection and Wave Emission:
Two-dimensional resistive magnetohydrodynamic simulations were performed on two cylindrical magnetic flux ropes, with constant out-of-plane magnetic field, undergoing magnetic reconnection. The model used for the flux ropes was based on similar work by
Stanier et al. Simulations were performed using LARE2D code.
Two flux ropes start in a position of near equilibrium, distance ± h away from the origin along the y-axis. The Lorentz force attracts the two flux ropes together. The flux ropes merge via the process of magnetic reconnection forming a single flux rope. During this process, the magnetic field oscillates. The field cycles between reconnecting along the horizontal and vertical axis. The magnitude of these oscillations decreases over time.
During oscillatory reconnection, waves emit radially outwards from the reconnection site. The waves have a quadrupolar structure, emitting only along the diagonals. The nature of these waves is currently being investigated.
Propagation Speed of the Waves:
The propagation speed of the waves was calculated. The propagation speed of the waves was found to be of the order 0.1𝑉𝐴, (where 𝑉𝐴 is the Alfvén speed). This is suggestive of slow waves propagating almost transverse to the magnetic field.
Parallel and Perpendicular Component of the Wave:
The velocity parallel and perpendicular to the total magnetic field was calculated. The component parallel to the magnetic field is stronger than the component perpendicular to the magnetic field. This shows that although the waves propagate radially outwards, most of the motion in the waves occurs along the magnetic field lines. This is not behaviour associated with slow waves. This behaviour indicates that the waves may behave as a combination of known wave modes.
Conclusion:
This poster discussed the waves emission from simulations of two cylindrical magnetic flux ropes undergoing magnetic reconnection. These wave’s propagation speed is suggestive of slow waves propagating almost transverse to the magnetic field. However, most of the motion of waves is parallel to the cylindrical magnetic field, which is not behaviour associated with slow waves. This indicates that the waves may be a combination of currently known wave modes.
Solar flares can be defined as the sudden and intense emission of electromagnetic radiation emitted from the solar atmosphere. This process is characterised by the conversion of stored magnetic energy in complex magnetic structures to kinetic and thermal energy through a process known as magnetic reconnection.
Short-lived temporary periodic oscillations, known as quasiperiodic pulsations (QPPs) are frequently observed in solar flare emissions. Understanding the origin of QPPs and their relation to magnetic reconnection can help develop diagnostic tools that can be used to investigate the conditions inside the solar flare.
Some solar flares occur when plasma loops in the solar corona interact and undergo magnetic reconnection. QPPs are believed to be generated during this process. This scenario can be modelled as the merging of two twisted magnetic flux ropes. This poster discusses simulations performed on two magnetic flux ropes merging and undergoing magnetic reconnection. The aim of these simulations was to study the resulting oscillatory behaviour. During the merging process, waves were emitted away from the reconnection site. The behaviour of these waves is discussed in this poster.
Oscillatory Reconnection and Wave Emission:
Two-dimensional resistive magnetohydrodynamic simulations were performed on two cylindrical magnetic flux ropes, with constant out-of-plane magnetic field, undergoing magnetic reconnection. The model used for the flux ropes was based on similar work by
Stanier et al. Simulations were performed using LARE2D code.
Two flux ropes start in a position of near equilibrium, distance ± h away from the origin along the y-axis. The Lorentz force attracts the two flux ropes together. The flux ropes merge via the process of magnetic reconnection forming a single flux rope. During this process, the magnetic field oscillates. The field cycles between reconnecting along the horizontal and vertical axis. The magnitude of these oscillations decreases over time.
During oscillatory reconnection, waves emit radially outwards from the reconnection site. The waves have a quadrupolar structure, emitting only along the diagonals. The nature of these waves is currently being investigated.
Propagation Speed of the Waves:
The propagation speed of the waves was calculated. The propagation speed of the waves was found to be of the order 0.1𝑉𝐴, (where 𝑉𝐴 is the Alfvén speed). This is suggestive of slow waves propagating almost transverse to the magnetic field.
Parallel and Perpendicular Component of the Wave:
The velocity parallel and perpendicular to the total magnetic field was calculated. The component parallel to the magnetic field is stronger than the component perpendicular to the magnetic field. This shows that although the waves propagate radially outwards, most of the motion in the waves occurs along the magnetic field lines. This is not behaviour associated with slow waves. This behaviour indicates that the waves may behave as a combination of known wave modes.
Conclusion:
This poster discussed the waves emission from simulations of two cylindrical magnetic flux ropes undergoing magnetic reconnection. These wave’s propagation speed is suggestive of slow waves propagating almost transverse to the magnetic field. However, most of the motion of waves is parallel to the cylindrical magnetic field, which is not behaviour associated with slow waves. This indicates that the waves may be a combination of currently known wave modes.
URL
james.stewart@manchester.ac.uk
Poster file