Akademik Veri Yönetim Sistemi
Solar Influences on the Magnetosphere, Ionosphere and Atmosphere, Burgas, Bulgaristan, 3 - 07 Haziran 2024, ss.25-37
Studies of solar (and stellar) dynamos face a problem of utter complexity, i.e., the interaction of a turbulent plasma in the convection zone, associated with latitudinal rotation together with magnetic field acting in a highly stratified medium, covering wide ranges of spatial and temporal scales. Recent theoretical models for the solar dynamo in complex 3-D simulations highlighted changes of the Sun’s stratification, mainly in the upper zones, pointing the role of the leptocline, a shallow and sharp shear layer in the top ~8-10 Mm. Here, we give here a brief history of the circumstances that led to the discovery of this layer, characterized by a strong radial rotational gradient at mid latitudes and self-organized meridional flows. We give an overview of the physical solar parameters that originate in this layer: opacity, superadiabicity and turbulent pressure changes; the hydrogen and helium ionization processes; sharp decrease in the sound speed; probably an oscillation phase of the seismic radius associated with a nonmonotonic expansion with depth; probably temporal changes in photospheric zonal and sectorial modes and their associated gravitational moments. Likely also the initial place of the solar wind escape. In addition, the leptocline may play a key role in the formation of the magnetic butterfly diagram. Such results should be the starting point of systematic further investigations of structure and dynamics in this layer, leading to a better understanding of the solar cycle.