Filamentary structure of the ISM at high latitudes

Different mechanisms for filament formation are studied with a view to account for the results of Verschuur (1991a, b). It is shown that pinch phenomena can produce a filamentary structure of H I without any pressure contribution from the warm component of the interstellar medium (ISM). The mechanisms of filament formation involving the Parker instability and magnetoconvection are also discussed. It is shown that instabilities corresponding to all these mechanisms may result in a picture similar to that observed by Verschuur.