An interpretation of the I-V phase background based on observed plasma jets

The presence of a solar background in the phase difference between the intensity and velocity (I - V) p-mode oscillation signals recently has been interpreted in terms of downflows due to convection (Skartlien & Rast 2000) or due to chromospheric explosive events (Moretti et al. 2001a). In support of the latter, we present I and V characteristics of impulsive brightenings observed in the NaI D lines, show that these reproduce the frequency dependence of the I - V modulation background, and show that explanations invoking more frequently occurring phenomena such as seismic events are not likely in low-elle modulation data.