Slow and sausage loop mode excitation due to local and global spontaneous perturbations

Abstract

We analyze the capability of different types of perturbations associated with usual environment energy fluctuations of the solarcorona to excite slow and sausage modes in solar flaring loops.Methods. We performed numerical simulations of magnetohydrodynamic (MHD) ideal equations with a consideration of straightplasma magnetic tubes subject to local and global energy depositions.Results. We find that local loop energy depositions of typical microflares [(1027- 1030) erg] are prone to driving slow shock wavesthat induce slow-mode patterns. The slow-mode features are obtained for every tested local energy deposition inside the loop. Meanwhile,in order to obtain an observable sausage mode pattern, a global perturbation that is capable of instantaneously modifying theinternal loop temperature is required; specifically, the characteristic conductive heating time must be much smaller than the radiativecooling one. Experiments carried out by varying the parameter demonstrate that the excitation of sausage modes does notsignificantly depend on the value of this parameter but, rather, depends on the global or local character of the energy source.