Microphysics of Waves and Instabilities in the Solar Wind and Their Macro Manifestations in the Corona and Interplanetary Space

Investigations of the physical processes responsible for coronal heating and the acceleration of the solar wind were pursued with the use of our recently developed 2D MHD solar wind code and our 1D multifluid code. In particular, we explored: (1) the role of proton temperature anisotropy in the expansion of the solar (2) the role of plasma parameters at the coronal base in the formation of high (3) a three-fluid model of the slow solar wind (4) the heating of coronal loops (5) a newly developed hybrid code for the study of ion cyclotron resonance in wind, speed solar wind streams at mid-latitudes, the solar wind

Are solar maximum fan streamers a consequence of twisting sheet structures?

Context.Fan streamers are often observed at low to mid latitudes in the corona at solar maximum, appearing narrow in latitudinal extent near the Sun, and fanning out with height, adopting an approximately linear, but not necessarily radial, configuration above ~3 $R_{\odot}$. Aims.We offer arguments to support the conjecture that such structures may sometimes consist of high density, non-uniform sheets, viewed edge-on near the Sun, and twisting to a more face-on alignment by 3 $R_{\odot}$. Methods.EUV and white light observations of a fan streamer observed on 2000/12/05 are analyzed. A simple 3D density model is used to recreate the streamer structure. Results.EIT images show a thin bright sheet at the base of the streamer. The continuation of this structure through the EIT, MLSO MKIV coronameter, and LASCO C2 fields of view, suggests that this sheet is formed mostly of open magnetic field lines. The overall large-scale appearance of the streamer is well simulated by a simple model of a twisting high-density sheet. If the twisting-sheet conjecture is valid, there is a correlation between the distribution of enhanced rays within the streamer viewed in white light, and the distribution of small regions of enhanced brightness seen on the disk in EIT 171 Å at the position of the streamer base. Conclusions.We suggest that the apparent poleward divergence of equatorial coronal rays, or threads, seen during solar maximum above active regions, may sometimes be a consequence of such a twisting sheet topology

An empirical 3D model of the large-scale coronal structure based on the distribution of Hα filaments on the solar disk

Despite the wealth of solar data currently available, the explicit connection between coronal streamers and features on the solar disk remains unresolved. An empirical three-dimensional model, which reproduces the evolution of the large-scale coronal structure starting from the solar surface, is presented. The model is based on the view that the source of the large-scale coronal structure, namely streamers, is a consequence of the evolution of twisted sheet-like structures originating from prominences (or, equivalently, filaments) at the base of the corona. The high-density sheets evolve and merge with height into a final radial configuration constrained by the oberved position of streamers stalks higher up in the corona. The observational constraints are provided by white light observations from the LASCO/C2 data during the declining phase of solar activity, spanning the end of Carrington Rotation (CR) 2005 and the start of CR 2006, i.e. July-August 2003, and the position of filaments from the corresponding H$\alpha$ synoptic maps of the Paris-Meudon Observatory. The 3D model thus derived yields a reasonable agreement with the observed large-scale coronal structure, in particular the shape of large helmet streamers. These results give confidence in the underlying assumption that large helmet streamers can be the result of the convergence of two or more sheet-like structures originating from a distribution of prominences on the solar disk. The model supports the view that streamers, during that time of the solar cycle, are often associated with multiple current sheets