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

We analyse the capability of different type of perturbations -associated with usual environment energy fluctuations of the solar corona- to excite slow and sausage modes in solar flaring loops. We perform numerical simulations of the MHD ideal equations considering straight plasma magnetic tubes subject to local and global energy depositions. We find that local loop energy depositions of typical microflares [$\sim$($10^{27}$-$10^{30}$) erg] are prone to drive slow shock waves that induce slow mode patterns. The slow mode features are obtained for every tested local energy deposition inside the loop. Meanwhile, to obtain an observable sausage mode pattern a global perturbation, capable to modify instantaneously the internal loop temperature, is required, i.e. the characteristic conductive heating time must be much smaller than the radiative cooling one. Experiments carried out by varying parameter $β$ show us that the excitation of sausage modes does not depend significantly on the value of this parameter but on the global or local character of the energy source.

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