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The structure of electric current and magnetic helicity in the solar coronais closely linked to solar activity over the 11-year cycle, yet is poorlyunderstood. As an alternative to traditional current-free "potential field"extrapolations, we investigate a model for the global coronal magnetic fieldwhich is non-potential and time-dependent, following the build-up and transportof magnetic helicity due to flux emergence and large-scale photosphericmotions. This helicity concentrates into twisted magnetic flux ropes, which maylose equilibrium and be ejected. Here, we consider how the magnetic structurepredicted by this model-in particular the flux ropes-varies over the solaractivity cycle, based on photospheric input data from six periods of cycle 23.The number of flux ropes doubles from minimum to maximum, following the totallength of photospheric polarity inversion lines. However, the number of fluxrope ejections increases by a factor of eight, following the emergence rate ofactive regions. This is broadly consistent with the observed cycle modulationof coronal mass ejections, although the actual rate of ejections in thesimulation is about a fifth of the rate of observed events. The model predictsthat, even at minimum, differential rotation will produce sheared,non-potential, magnetic structure at all latitudes.

Solar Cycle Variation of Magnetic Flux Ropes in a Quasi-Static Coronal Evolution Model