Topical Discussion Meeting - 3D structure and extraction of coronal holes, and the consequences for space weather
Stephan G. Heinemann (Institut of Physics, University of Graz); Stefan J. Hofmeister (Institut of Physics, University of Graz); Manuela Temmer (Institut of Physics, University of Graz); Tadhg Garton (School of Physics, Trinity College Dublin, Dublin 2 Ireland); Jon Linker (Predictive Science Inc.)
Monday 18/11, 17:15-18:30
Coronal holes (CH) are recognized to be the solar source regions of high-speed solar wind streams. These streams are closely associated with recurrent geomagnetic activity, and are therefore of major importance in space weather forecasting. CH properties are an important input and/or consistency check for empirical and numerical models that forecast high-speed stream properties in interplanetary space. However, differences in the extraction of CHs based on EUV and magnetic field data, impedes comparison and evaluation of the results. A consistent definition of CH boundaries does not yet exist. Improving our knowledge of solar wind sources requires a deeper understanding of CH properties and their role in producing fast solar wind. The background solar wind is not only important for recurrent activity, but also plays a key role in the propagation of transient disturbances, so advances in this area are vital for providing more reliable Space Weather warnings.
The aim of this TDM is to discuss a roadmap towards a consistent definition of CHs, how this can be applied for CH detection, and in turn improve forecasting and modeling results. We invite short contributions that can enlighten important aspects on CH structure, challenges in extraction, modeling of the open magnetic field, and/or limitations in our observational methods.
As key points we raise the following:
• What is the relevant physics: density depletion vs. open magnetic field configuration?
• How should CHs be defined? Modelling, observations or a combination?
• Open magnetic flux problem in modelling: Are models accurate enough to estimate the open coronal magnetic flux from photospheric magnetograms? Should we combine observations and models?
• 3D structure: horizontal - vertical
• How are coronal holes built up? How strong is the expansion at what heights? At what heights do we observe/ extract coronal holes from?
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