| Abstract : | Localised magnetic reconnection at the dayside magnetopause gives rise to Flux Transfer Events or FTEs. These FTEs have been abundantly observed in-situ. The magnetic fields within the FTEs are seen to exhibit complex helical flux-rope topologies with a mixture of field lines of various connectivities. Leveraging the adaptive mesh refinement strategy, we perform a three-dimensional resistive magnetohydrodynamic simulation of the magnetosphere of an Earth-like planet and study the evolution of these FTEs. For the first time, we detect and track the FTE structures in 3D and present a complete volumetric picture of FTE evolution. The temporal evolutions of thermodynamic quantities within the FTE volumes confirm that continuous reconnection at the active X-lines spanning the FTEs is the dominant cause of active FTE growth, as indicated by the deviation of the pressure–volume curves from an adiabatic profile. An investigation into the magnetic properties of the FTEs shows a rapid decrease in the perpendicular currents within the FTE volume, exhibiting the tendency of currents within the FTE structure toward being field-aligned. Such FTEs are readily modelled from in-situ observations using the linear (constant-α) force-free flux-rope model. An assessment of the validity of the linear force-free flux-rope model for such FTEs shows that the structures drift toward a constant-α state but continuous reconnection inhibits the attainment of a purely linear force-free configuration. Additionally, the fluxes enclosed by the selected FTEs are computed to range between 0.3 and 1.5 MWb. The FTE with the highest flux content constitutes ∼1% of the net dayside open flux which is close to previous estimates in literature. These flux values are further compared against the flux estimates provided by the linear force-free flux-rope model. For the selected FTEs, the linear force-free model underestimated the flux content by up to 40%, owing to the continuous reconnected flux injection. |
