Formation of Extreme Anomalies in the Total Electron Content According to Data from Linear Theory

Under the assumption that the evolution of the total electron content (TEC) in a quiet ionosphere can be described within the framework of the linear dynamic-stochastic approach, the corresponding model is constructed and verified. The TEC data archive for 1998–2018 of the Crustal Dynamics Data Information System (CDDIS) of the National Aeronautics and Space (NASA) Administration was used in the calculations. The observed extreme anomalies of the TEC field (with an anomaly magnitude exceeding the triple value of the root-mean-square deviation of the anomaly norm) were interpreted as the response of a quiet ionosphere to external actions. It is believed that such actions include disturbances of the solar radiation flux and geomagnetic anomalies characterized by corresponding indices, as well as actions of other physical natures (the influence of the atmospheric gravity wave breaking, etc.). The external action was defined as the difference between the changed TEC anomaly predicted with the linear model and its real value. The linear dynamic-stochastic model made it possible to distinguish anomalies of the initial state of the ionosphere and external actions that were able to change it to the greatest extent after a given time. It is shown that the structure of extreme TEC anomalies is determined by the form of the optimal response vectors (left singular vectors of the corresponding operators). The coefficient of correlation reaches 0.85 for projection of the anomaly onto five leading vectors and 0.7 for projection onto the first vector.