Understanding Electron Heat Flux Dropouts

Electron heat flux dropouts occur relatively frequently in the solar wind. While they are a necessary signature of flux that is disconnected from the Sun, and knowledge of just how much flux is disconnected is vital for discriminating between models of how the Sun reverses its magnetic field, it is now becoming increasingly clear that most dropouts are caused by some other mechanism. We report on progress in understanding that mechanism. Two factors contribute to electron heat flux in the solar wind: total flux integrated over pitch angle, and pitch angle isotropy. The latter correlates well with plasma beta, but the former does not, implying that heat flux and isotropy are to some degree independent and that pitch angle scattering in high-beta plasma may contribute to isotropy. However, drops in total integrated flux do seem to correlate with the pitch angle isotropy but at scale sizes larger than those of beta variations.. We use Wind data to perform correlations between total flux, isotropy and beta to determine at which scales they are best correlated. If total flux and beta are independent, we would expect their respective correlations with isotropy to occur at different scales. The scale at which each correlation maximises provides valuable information on the processes involved in heat flux dropouts and on the interdependence between total flux, isotropy and plasma beta.