Abstract: Cranmer and van Ballegooijen (2010)

Cranmer, S. R., and van Ballegooijen, A. A. 2010, "Connections Between the Magnetic Carpet and the Unbalanced Corona: New Monte Carlo Models," SHINE 2010 Workshop, Santa Fe, New Mexico, July 26-30, 2010.

ABSTRACT:

It is clear from observations of the solar magnetic carpet that much of the heating in closed-field regions is driven by the interplay between emergence, separation, merging, and cancellation of many small flux elements. However, we do not yet know to what extent the open flux tubes are energized by these processes. In order to begin investigating this, we developed Monte Carlo simulations of the photospheric magnetic carpet and extrapolated the time-varying magnetic field up into the corona. These models were constructed for a range of different magnetic flux imbalance ratios (i.e., for both quiet regions and coronal holes), and they appear to be the first simulations to utilize newly observed flux emergence rates that are at least an order of magnitude larger than those used in earlier models. The results agree with a wide range of observations, including surface flux densities and number distributions of magnetic elements. Despite having no imposed supergranular motions in the models, a realistic network of magnetic funnels appeared spontaneously. We also computed the rate at which closed field lines open up (i.e., the recycling times for open flux), and we estimated the energy flux released in reconnection events involving the opening up of closed flux tubes. For quiet regions and mixed-polarity coronal holes, these energy fluxes were found to be much lower than required to accelerate the solar wind. For the most imbalanced coronal holes, the energy fluxes may be large enough to power the solar wind, but the recycling times are far longer than the time it takes the solar wind to accelerate into the low corona. Thus, reconnection and loop-opening processes in the magnetic carpet may be responsible for intermittent events in coronal holes (e.g., polar jets), but probably not for the majority of bulk solar wind acceleration.

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