Estimation of frequency and duration of ionospheric disturbances over Turkey with IONOLAB-FFT algorithm
- PDF / 3,375,033 Bytes
- 24 Pages / 595.276 x 790.866 pts Page_size
- 68 Downloads / 170 Views
ORIGINAL ARTICLE
Estimation of frequency and duration of ionospheric disturbances over Turkey with IONOLAB-FFT algorithm Secil Karatay1 Received: 2 September 2019 / Accepted: 6 August 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract One of the more common methods of observation of variability of the Earth’s ionosphere is based on total electron content (TEC) estimated from ground-based dual-frequency Global Positioning System (GPS) receivers. Variations in solar, geomagnetic and seismic activity cause depletions or enhancements in the ionospheric electron concentrations that can be detected as disturbances. Some of these disturbances have wave-like characteristics, where frequency of oscillation can be used to identify and classify the disturbance. In this study, the frequency of such periodic disturbances is estimated using a fast Fourier transform (FFT)-based method, namely IONOLAB-FFT, in the spectral domain. IONOLAB-FFT, which was initially developed to be used on slant TEC (STEC), is modified to be applied to TEC in the local zenith direction of the receiver. The algorithm is tested using literature data on disturbances generated by a geomagnetic activity, a solar flare, a medium-scale traveling ionospheric disturbance (MSTID), a large-scale TID (LSTID) and an earthquake. An accordance with these known disturbances is observed in running IONOLAB-FFT, and the main frequencies and durations of the disturbances are estimated. IONOLAB-FFT method is applied to TEC computed from Turkish Permanent GPS Network (TNPGN-Active) which lies in mid-latitude region to detect the any wave-like oscillations, sudden disturbances and other irregularities during December, March, June and September months for 2010, 2011 and 2012 years. It is observed that a large number of the estimated frequencies are accumulated between 0.08 and 0.14 MHz corresponding to periods of 3.5 h to 2 h. The significant frequencies are grouped less than 0.28 MHz. A large number of the durations of the oscillations are between 425 and 550 min in 2010, 300 and 550 min in 2011 and 350 and 400 min in 2012. The longest duration (around 800 min: 13.33 h) is observed in December months, and the shortest duration (around 2 h) is observed in September months. Keywords Ionosphere · GPS · Total electron content · Disturbances · FFT
1 Introduction The ionosphere is defined as the region of Earth’s upper atmosphere between 50 and 1000 km. It has electrically charged ions and electrons that affect the propagation of radio waves. The charged particles are produced mainly by solar radiation. Therefore, the properties of the ionosphere depend significantly on the Sun and its activity. The ionization in the ionosphere varies with in space and time. A 11-year solar cycle and seasonal, monthly and diurnal periodicities are the characteristics of the ionosphere. The other mechanism and factors, such as solar, geomagnetic and seismic activi-
B 1
Secil Karatay [email protected] Department of Electrical and Electronics Engineering, Kastamo
Data Loading...
