On the Relationship between He<scp>ii</scp>λ304 Prominences and the Photospheric Magnetic Field

Abstract

As observed in He II λ304 images recorded at high cadence, quiescent prominences resemble long-lived systems of jets, in which chromospheric material streams continually from one footpoint area to another. To further clarify the physical nature of the source regions, we have compared He II λ304 images of on-disk prominences (filaments) with line-of-sight magnetograms, employing data from the Extreme-Ultraviolet Imaging Telescope (EIT) and the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The quiescent filaments lie within channels separating the opposite-polarity network fields on each side and containing relatively weak magnetic flux of both polarities. The sideways extensions ("barbs") and endpoints of the filaments overlie smaller scale neutral lines, where opposite-polarity flux elements are in close contact and mutual cancellation occurs. From the chirality rules of Martin et al., we deduce that the barbs are rooted in minority-polarity flux on the "wrong" side of the large-scale photospheric neutral line, and we propose a mechanism for their formation based on the concept of supergranular diffusion. Our results support earlier suggestions that magnetic reconnection accompanying photospheric flux cancellation is the dominant mechanism for injecting mass into quiescent prominences.