Magnetic properties of Civ Doppler shift patterns

The relationship between Doppler shift patterns observed in the transition region and magnetic field patterns observed in the photosphere is studied using coaligned pairs of Civ Dopplergrams and Fei magnetograms. Categories of magnetic features are defined - including neutral lines, unipolar regions, strong field regions, weak field regions, and magnetic boundaries - and from these, magnetic associations are determined for 159 V ₀ lines separating areas of relative blueshift and redshift observed in and around active regions. The cases are subdivided on the basis of whether blueshifts or redshifts are observed on the side of the V ₀ line nearest the solar limb.Two main results are that V ₀ lines associated with neutral lines tend to have limbward blueshifts, while V ₀ lines associated with unipolar regions tend to have limbward redshifts. These and other results provide supportive evidence for the active region model proposed recently by Klimchuk, in which relative redshifts occur where strong vertical fields penetrate the surface, and relative blueshifts occur where these same fields have spread out to become horizontal. It is likely that the relative blueshifts correspond to absolute Doppler shifts of very small amplitude, possibly even absolute redshifts.The National Center for Atmospheric Research is sponsored by the National Science Foundation.