Engineering topics
Publications and source records attributed to Henoux, Jean-Claude.
Team 2 of the Ottawa Flares 22 Workshop dealt with observational and theoretical aspects of the characteristics and processes of energy release in flares. Main results summarized in this article stress the global character of the flaring phenomenon in active regions, the importance of discontinuities in magnetic connectivity, the role of field-aligned currents in free energy storage, and the fragmentation of energy release in time and space.
We report findings concerning energy transport and dynamics in flares during the impulsive and gradual phases based on new ground-based and space observations (notably from Yohkoh). A preheating sometimes occurs during the impulsive phase. Ca XIX line shifts are confirmed to be good tracers of bulk plasma motions, although strong blue shifts are not as frequent as previously claimed. They often appear correlated with hard X-rays but, for some events, the concept that electron beams provide the whole energy input to the thermal component seems not to apply. Theory now yields: new diagnostics of low-energy proton and electric beams; accurate hydrodynamical modeling of pulse beam heating of the atmosphere; possible diagnostics of microflares (based on X-ray line ratio or on loop variability); and simulated images of chromospheric evaporation fronts. For the gradual phase, the continual reorganization of magnetic field lines over active regions determines where and when magnetic reconnection, the mechanism favored for energy release, will occur. Spatial and temporal fragmentation of the energy release, observed at different wavelengths, is considered to be a factor as well in energy transport and plasma dynamics.