Coronal Structures Observed in X-rays (NIXT) and H_alpha Surges

Ground-based coordinated observations with the Multichannel subtractive double pass spectrograph (MSDP) and the heliograph in Meudon allowed us to portray the chromospheric intensity and velocity fields below coronal structures observed with the Normal Incidence X-ray Telescope (NIXT). On July 11, 1991 (eclipse day) we have identified in AR 6713 (N38 W 42) the X-ray signatures of the network, subflares, filaments and surges. The largest H_alpha surge has only weak emission in X-ray, while a weak H_alpha feature corresponds to a very bright x-ray subflare. We calculate the emission measures of these events and give some constraints on the triggering mechanisms of surges.