Intense velocity-shears and magnetic fields in diffuse molecular gas: from 10 pc to 5 mpc

Regions of intense velocity-shears are identified on statistical grounds in nearby diffuse molecular gas: they form conspicuous thin (∼ 0.03 pc) and parsec-long structures that do not bear the signatures of shocked gas. Several straight substructures, ∼ 3 mpc thick, have been detected at different position-angles within one of them. Two exhibit the largest velocityshears ever measured far from star forming regions, up to 780 km s−1 pc−1 . Their position-angles are found to be also those of 10-parsec striations in the I(100μm) dust emission of the large scale environment. The B field projections, where available in these fields, are parallel both to the parsec- and to one of the milliparsec-scale shears. These findings put in relation the small-scale intermittent facet of the gas velocity field and the large scale structure of the magnetic fields.