Measuring kink waves in the internetwork chromosphere
Krishna Mooroogen
Northumbria University
Richard Morton
Current observational instruments are now providing data with the necessary temporal and spatial cadences required to examine highly dynamic, fine-scale magnetic structures in the solar atmosphere. Using a combination of monochromatic imaging and spectroscopy from the Swedish Solar Telescope, we investigate the dynamic properties of internetwork fibrils. We find the fibrils support wave like motions, which we interpret as kink waves, and we use the measured wave properties to provide statistics on the variation of plasma properties via magneto-seismology. We model the data to improve the uncertainties of the measurement of spatial and temporal properties of the waves. The variation of the noise as a function of intensity of the data was determined, and a non-linear relationship was found. Using an advanced tracking and fitting routine we create time-series plots of intensity and measure the periods and amplitudes of the waves along a wave-guide. Cross-correlation was applied to the time-series to measure the propagation speed of the waves. The estimated data noise is used to establish sampling distributions for uncertainties, which were propagated through to determine the uncertainties of the measurements of the propagation speeds. This was achieved by employing a Monte Carlo parametric bootstrapping technique. Using the measured amplitudes and propagation speeds, we are able to infer the variation of plasma properties along fibrils via magneto-seismology. The measurements of the periods and amplitudes have a broad distribution, with ranges, 70-150 s and 100-120 km respectively. Phase speeds were measured above the local sound speed, between the ranges, 20-200 km/s.