Estimation of Polar Depletion Regions by VTEC Contrast and Watershed Enhancing

This article presents a method for determining near-Pole ionization depletion regions and troughs from global navigation satellite system (GNSS) vertical total electron content (VTEC) maps. To define the regions, we use Image processing tools, considering VTEC maps as gray-level images. In this work, watershed segmentation is applied to determine edges of based on flow areas between lowest zones (< 1%) medium (> 10%). order enhance contrast low-ionization those with higher relative ionization, histogram equalized, which increases maps, distance are increased. The percentile thresholds makes independent hypotheses about generation depletions, their morphology, or number that can occur map. We test performance by comparing identified in eight events reported literature under different conditions ionosphere. used reference were measured satellites, radar, GNSS. propose allows real-time GNSS morphology detected matches shape literature.