Open Magnetic Flux and the Slow Solar Wind
Abstract
In the standard paradigm of coronal structure (most applicable to solar minimum), the open magnetic field originates primarily in coronal holes, regions of low intensity emission in EUV and X-rays. The regions that are magnetically closed trap the coronal plasma and give rise to the streamer belt that is prominent in coronagraph and eclipse images. If this paradigm is correct, then coronal models using global maps of the photospheric magnetic field should be able to approximately match coronal boundaries observed in emission, as well as the magnitude of the open magnetic flux inferred from in situ spacecraft measurements. We have investigated the July 2010 time period, using PFSS and MHD models computed using several available magnetic maps, coronal hole boundaries detected from STEREO and SDO EUV observations, and estimates of the interplanetary magnetic flux from in situ ACE measurements. We have found that for all of the model/map combinations, models that have coronal hole areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than coronal holes observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected coronal holes for Carrington rotation 2098 with observatory synoptic magnetic maps for this time period. We find that this method also underestimates the interplanetary magnetic flux. We discuss these results and possible implications for the origin of the slow solar wind.
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2017)
- Pub Date:
- July 2017
- Bibcode:
- 2017shin.confE..71L