Abstract
Abstract. Observations of streamers in extreme ultraviolet (EUV) emission with SOHO/UVCS show dramatic differences in line profiles and latitudinal variations in heavy ion emission compared to hydrogen Ly-α emission. In order to use ion emission observations of streamers as the diagnostics of the slow solar wind properties, an adequate model of a streamer including heavy ions is required. We extended a previous 2.5-D multi-species magnetohydrodynamics (MHD) model of a coronal streamer to 3-D spherical geometry, and in the first approach we consider a tilted dipole configuration of the solar magnetic field. The aim of the present study is to test the 3-D results by comparing to previous 2.5-D model result for a 3-D case with moderate departure from azimuthal symmetry. The model includes O5+ ions with preferential empirical heating and allows for calculation of their density, velocity and temperature in coronal streamers. We present the first results of our 3-D multi-fluid model showing the parameters of protons, electrons and heavy ions (O5+) at the steady-state solar corona with a tilted steamer belt. We find that the 3-D results are in qualitative agreement with our previous 2.5-D model, and show longitudinal variation in the variables in accordance with the tilted streamer belt structure. Properties of heavy coronal ions obtained from the 3-D model together with EUV spectroscopic observations of streamers will help understanding the 3-D structures of streamers reducing line-of-sight integration ambiguities and identifying the sources of the slow solar wind in the lower corona. This leads to improved understanding of the physics of the slow solar wind.
Highlights
White-light images of the solar corona from ground observations during the total solar eclipses and space-based coronagraphs show that the dominant magnetic structures of the minimum corona are equatorial streamers
The magnetic structure determines plasma parameters in the streamer, high plasma density and electron temperature with a maximum at the core of the streamer. It has been well known for decades that, during the solar minimum, the magnetic field of the Sun is qualitatively described as a tilted dipole and a long-lived quiescent streamer belt forms at low latitudes, as seen in eclipse images and white-light coronagraph observations
During the solar minimum the structure of the solar magnetic field can be well approximated by the tilted dipole configuration
Summary
White-light images of the solar corona from ground observations during the total solar eclipses and space-based coronagraphs show that the dominant magnetic structures of the minimum corona are equatorial streamers. The magnetic structure determines plasma parameters in the streamer, high plasma density and electron temperature with a maximum at the core of the streamer. It has been well known for decades that, during the solar minimum, the magnetic field of the Sun is qualitatively described as a tilted dipole and a long-lived (several days or longer) quiescent streamer belt forms at low latitudes, as seen in eclipse images and white-light coronagraph observations. The streamer belt structures is evident in UV emission of ions (e.g., Giordano and Mancuso, 2008)
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