Statistics of total electron content depletions observed over the South American continent for the year 2008

Abstract

This paper presents for the first time regional plots of total electron content (TEC) depletions derived from GPS observations over the South American continent with a coverage of over 45° longitude (i.e., 35°W to 80°W). We introduce a new numerical algorithm that has been developed to automatically detect TEC bite‐outs that are produced by the transit of equatorial plasma bubbles. This algorithm was applied to TEC values measured by the Low Latitude Ionospheric Sensor Network (LISN) and by receivers that belong to 3 other networks that exist in South America. The general characteristics of the TEC depletions are provided along with their temporal length, local time distribution and depletion depth. The regional day‐to‐day and seasonal variability of the TEC depletions are also presented for 2008, a year of low solar activity. The regional day‐to‐day variability of TEC depletions is highly dynamic, but their seasonal distributions follow the longitudinal characteristics of plasma bubbles presented by other authors. During the equinoxes, TEC depletions are mainly observed on the west coast of South America, and during the December solstice they mostly occur on the east side of the continent. However, in all seasons, we observe days when depletions extend all over the continent. We place these new results in the context of theories of plasma bubble seeding.