The large-scale structure of the solar minimum corona.

摘要

The goal of this thesis is to find a quantitative description of the large-scale structure of magnetic field and density in the solar minimum corona that is consistent with observations of both white light intensity and the magnetic field at the photosphere. We use white light images from NASA's Solar Maximum Mission (SMM) Coronagraph/Polarimeter and the High Altitude Observatory Mark III (MkIII) K-coronameter, along with photospheric field measurements from Stanford's Wilcox Solar Observatory (WSO), as constraints on the magnetostatic model of Bogdan and Low (B&L) (1986). We find a family of solutions to the B&L model that reproduce observations of white light quite well, each with a different magnetic field structure. We show that the observed photospheric field cannot be used as an exact boundary condition on the B&L model, but we can limit the white light solutions by matching the total observed photospheric magnetic flux. We find a set of seven model parameters that reproduces white light and photospheric field to within quantifiable model and observational limits, and calculate the physical plasma properties of density, pressure, magnetic field, and temperature that correspond to these parameters.; We extend the model to include current sheets at the equator and around the coronal helmet streamer, and show that by doing so we improve the fit to white light data and to a lesser extent to the photospheric flux. Moreover, by including current sheets in the model, we produce a magnetic field line structure which better matches the underlying coronal white light structure, and which is more consistent with a solar wind accelerating along the open field lines. We use the magnetic field structure determined from our bulk current/current sheet model to calculate expansion factors, which can be used as essential inputs to solar wind models. Finally, we determine that the temperature structure predicted by our model is not in thermal equilibrium. We present a preliminary comparison of this temperature structure to independent emission line temperature diagnostics, and discuss how we hope in future to use such analyses to produce a more energetically consistent temperature distribution.