Fig. 4. Locations of bright lanes of umbral flashes (UFs, green line segments) plotted over an off-band H-alpha image. The red dotted contours indicate the HMI line-of-sight magnetic field strength at -1000, -1400, -1600, and -1800 G. L1, L2, L3, R1, and R2 mark various UFs lanes discussed in the study.
Fig. 5. Dynamics of UFs as seen in NST Halpha+0.4A (top) and Halpha-0.4A (bottom) images. L1 and R1 mark locations of two bright UF lanes. The short line segments mark the edge of an expanding UF lane, while the arrow shows the direction of its expansion. The large tick marks in the leftmost top panel indicate 1 Mm intervals.
Fig. 6. NST Halpha 0.4A Doppler map (left) and IRIS Mg II k slit-jaw image. The black contour outlines the Mg II k sunspot and is drawn at an arbitrary level. The white arrow points to a blue shifted feature in the Halpha Doppler map that corresponds to the R1 UF lane. The two broken line segments mark two low contrast Mg II k UF fronts that are co-spatial with the two red-shifted features in the H® Doppler map.