Non-potential Enhancement of the Sun's Open Magnetic Flux
Abstract
Measurements of the interplanetary magnetic field (IMF) over several solar cycles do not agree with expected values of open magnetic flux from potential field models. The discrepancy becomes greater around solar maximum in each cycle, when the IMF can be twice as strong as predicted by the models. It has previously been suggested that the increased rate of coronal mass ejections around solar maximum could be responsible for enhancing the open flux. We test this idea by removing the potential field assumption in simulations of the coronal magnetic field evolution over the solar cycle. The simulations use magneto-frictional relaxation in response to flux emergence and surface flux transport, and allow for the development of coronal currents and for the ejection of twisted magnetic flux ropes. Preliminary results show that the non-potential fields have significantly more open flux than potential extrapolations, in agreement with IMF observations. We find that the additional open flux arises from two separate effects: temporary enhancement due to coronal mass ejections, and a background enhancement due to the non-potential nature of the force-free equilibria. (Supported by NASA/LWS grant NNG05GK32G, and NASA contract NNM07AB07C to SAO.)
- Publication:
-
Solar Heliospheric and INterplanetary Environment (SHINE 2009
- Pub Date:
- August 2009
- Bibcode:
- 2009shin.confE.182Y