The Relative Importance of Geomagnetic Storm Signatures on the Total Electron Content Perturbations Over the Continental US

A study of 37 large solar storms occurring in the equinox periods from 2000 to 2018 is presented to quantify their effects on total electron content (TEC) variations in the ionosphere over the North American sector. The dependence of storm-related TEC enhancements and depletions is studied as a function of various storm parameters using machine-learning and statistical algorithms to quantify their relative importance. The variables under consideration include the onset time and duration of each storm, as well as characteristic scalar values derived from ring current variations detected by a network of ground-based magnetometers. The TEC data used in the study are taken from the Continuously Operating Reference Station network of ground-based GPS measurements, archived in the Madrigal database. The agreement and disagreement of the results across the different methods studied, along with the relative uncertainties in model prediction capability of the machine-learning study, show that the geo-effectiveness of large storms in the equinox periods is more closely related to the storm onset time and to ionospheric preconditioning than to any other parameters used in characterizing the storm. The effects in the higher latitude regions are shown to be very different from the lower latitude regions over the North American sector. This behavior can possibly be explained through storm-induced changes in the atmospheric chemistry and the related temperature-dependent production and loss processes at the higher latitudes.