Supersonic Downflows in the Vicinity of a Solar Pore

At the footpoints of magnetic arcades spanning over a site of flux emergence we observe strong redshifts in the He I triplet at 1083 nm. These redshifts are associated with downflow speeds of up to 40kms−1. Within the spatial resolution of our data (1″–2″) obtained with the Tenerife Infrared Polarimeter at the VTT we find an almost unshifted atmospheric component coexisting with the redshifted component. We were able to retrieve the magnetic field configuration in both the unshifted and the redshifted component simultaneously and infer an uncombed, fibril-like structure of the upper chromosphere. The supersonic downflow speeds are interpreted as a consequence of a significantly reduced pressure scale height above the pore, where the magnetic arcades are rooted. A temporal series of the fast downflow region reveals that the supersonic flow is maintained for more than one hour. Making use of the increased spatial resolution of the new TIP2 instrument we are working on reducing the upper limit on the size of the fibril-like flux channels in the upper chromosphere.