Investigation of ionospheric TEC anomalies caused by space weather conditions
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ORIGINAL ARTICLE
Investigation of ionospheric TEC anomalies caused by space weather conditions Salih Alcay1 · Merve Gungor1
Received: 19 June 2020 / Accepted: 29 August 2020 © Springer Nature B.V. 2020
Abstract This study examines the influence of space weather conditions on ionospheric TEC variations at different latitudes around the world. According to the space weather condition indices (geomagnetic storm-activity indices, solar activity indices, magnetic field change indices, plasma density and proton flux indices) different time periods were chosen. GPS observations were used to obtain TEC data derived from International GNSS Service (IGS) stations located at northern and southern hemisphere latitude regions (equatorial, mid-latitude and high latitude). GPS TEC data were evaluated associated with the space weather conditions using 15-day running median statistical analysis method. The results showed that besides the commonly used geomagnetic storm-activity and solar activity indices, plasma density, magnetic field change and particle flux indices are also important in determining whether there is any TEC anomaly in the ionosphere. This study illustrated that all indices should be examined in the applications associated with the ionosphere and particularly in the research of pre-earthquake ionospheric anomalies. Keywords Ionosphere · Space weather condition · Space weather condition indices · TEC
1 Introduction Earth’s atmosphere is divided into five main layers according to the temperature and is retained by the gravity.
B S. Alcay
[email protected]
1
Geomatics Engineering Department, Engineering and Architecture Faculty, Necmettin Erbakan University, Konya, Turkey
The layers from the closest to the highest of the Earth’s surface are troposphere, stratosphere, mesosphere, thermosphere and exosphere, respectively. The ionosphere is the ionized part of upper atmosphere ranging from 60 km to 1000 km includes entire thermosphere and parts of the mesosphere and exosphere. The ionosphere exhibits some regular, temporal and regional variations including diurnal, 27-day, seasonal, semiannual, annual, 11 year (Sentürk and Cepni 2018). These changes can be modeled and their effects can be largely determined. Besides the regular variations, unexpected irregular variations in the ionosphere are caused by many factors including space weather conditions (aurora, coronal holes, coronal mass ejection, galactic cosmic rays, geomagnetic storms, ionospheric scintillation, radiation belts, solar EUV irradiance, solar flares, solar radiation storm, solar wind, traveling ionospheric disturbances (URL-1)), geological natural hazards (earthquakes, volcanic eruptions), manmade events (nuclear explosion, rocket launches). The ionosphere effects the various areas such as space-based observation systems (GNSS etc.), synthetic aperture radar (SAR) imaging (Xu et al. 2004), communication systems, earth satellites - power grids on earth (Brunini et al. 2004) and space weather applications (Liu and Gao 2004). The widespread effe
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