Abstract

Abstract. TEC data, obtained from over 60 GPS stations, were used to study the ionospheric effects of the 12–16 September 1999 magnetic storm over Europe. The spatial and temporal changes of the ionosphere were analysed as a time series of TEC maps, which present 15 min averages of TEC. The data set consisting of GPS observations, collected by a dense network of European stations, with sampling rate of 30 s, enable the creation of TEC maps with high spatial and temporal resolution. The storm included the positive as well as the negative phase. The positive phase took place during the first storm day of 12 September 1999. The short-lived daytime TEC enhancement was observed at all latitudes. The maximal enhancement reached a factor of 1.3–1.5. On the second and third days, the negative phase of the storm developed. The TEC decrease was registered regardless of time of the day. The TEC depression exceeded 70% relative to quiet days. On the following days (15 and 16 September), a significant daytime enhancement of TEC was observed once again. The complex occurrence of the ionospheric storm was probably related to the features of development of the magnetic storm. We found out that during the storm the large and medium-scale irregularities developed in the high-latitude ionosphere. The multi-stations technique, employed to create TEC maps, was particularly successful while studying the mid-latitude ionospheric trough. We found out that the essential changes of TEC during the storm, which were registered at the auroral and sub-auroral ionosphere, were connected with the effect of the trough and its dynamics, which depends on geomagnetic activity.Key words. Ionosphere (ionospheric disturbances; auroral ionosphere; mid-latitude ionosphere)

Highlights

  • Nowadays, GPS measurements are commonly used to investigate the structure and dynamic of the ionosphere

  • The September 1999 storm consisted of a short-duration positive effect on the first day on a driven stage of the storm and a long-lasting negative phase on 13 and 14 September

  • This is a well-known picture in the development of the ionospheric storm

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Summary

Introduction

GPS measurements are commonly used to investigate the structure and dynamic of the ionosphere. The comparison of storm-time behaviour of TEC with f oF2 measurements at different latitudes is presented. The strong positive effect was observed in TEC and f oF2 during the daytime on 15 and 16 September. Temporal evaluation of TEC distribution over Europe on the first disturbed day (12 September) is presented in Fig. 6 via the series of TEC maps.

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