Influence of photospheric magnetic fields and dynamics on chromospheric K-line emission

We analyze a 9 hr sequence of simultaneous, high-resolution, high-cadence G-band and K-line solar filtergrams plus magnetograms of lower cadence and resolution. Images include both network and inter-network. The magnetic and filtergram intensities, their fluctuations, and relative phases change with progressive strengthening of local magnetic field. At increased flux levels, sudden photospheric downflows create long-lived magnetic elements. For weak magnetic fields the K-line and G-band intensities include an oscillatory component with period 4 minutes. For stronger fields, the K-line period shifts to 5 minutes, while the G-band fluctuations fade due to dissociation of their source, the CH radical. These K-lins and G-band fluctuations, whose periods are longer than the acoustic cutoff, are coherent and in phase. They also are coherent with fluctuations of the magnetic field. Weak-field magnetic fluctuations lead the intensity fluctuations by a phase shift of 90°. Strong-field magnetic fluctuations trail the intensities by 100°. These are interpreted as standing waves in the photosphere and low chromosphere. Another class of G-band fluctuations, with periods shorter than the acoustic cutoff, is associated both with stronger magnetic fields and with enhanced K-line emission with fluctuations longer than the cutoff period. This suggests waves excited by rapid photospheric perturbations and propagating up along magnetic flux tubes.