The increase of the ionospheric activity as measured by GPS

Abstract

The paper outlines a method allowing to compute the TEC with a precision of about 2–3 TECU and to detect Travelling Ionospheric Disturbances using GPS measurements. We describe the solar cycle dependance of the TEC and TIDs. Since the beginning of 1998, we have observed a stronger ionospheric activity due to the increasing solar activity. This ionospheric activity is characterized by larger TEC values which are regularly reaching the level of 60 TECU and by a larger number of Travelling Ionospheric Disturbances. During the winter 1999–2000, the mean daily TEC was above 45 TECU; at solar minimum the mean daily TEC is ranging from 4 TECU to 12 TECU. In January 2000 (close to solar maximum) more than 1300 events due to TID’s were detected: it is 6.5 more than in January 1996 (at solar minimum).