Fluxes input parameters (parameter -- description -- options, with default given first):

flux_option -- determines flux model -- 'gs2', 'gryffin', 'gene', 'global', 'ifspppl', 'quasilinear'
vtfac -- thermal speed = sqrt(vtfac*T/m)...should be consistent with def. from flux code -- default 2.0
grad_option -- determines which equilibrium gradients to evolve -- 'tgrads', 'all', 'tigrad', 'ngrad'
fork_flag -- .false. for running serially, .true. otherwise