Browsing by Author "Arikan F."

Now showing 1 - 4 of 4

Classification of regional ionospheric disturbance based on machine learning techniques
(2016-08-01) Terzi M.B.; Arikan O.; Karatay S.; Arikan F.; Gulyaeva T.
In this study, Total Electron Content (TEC) estimated from GPS receivers is used to model the regional and local variability that differs from global activity along with solar and geomagnetic indices. For the automated classification of regional disturbances, a classification technique based on a robust machine learning technique that have found wide spread use, Support Vector Machine (SVM) is proposed. Performance of developed classification technique is demonstrated for midlatitude ionosphere over Anatolia using TEC estimates generated from GPS data provided by Turkish National Permanent GPS Network (TNPGN-Active) for solar maximum year of 2011. As a result of implementing developed classification technique to Global Ionospheric Map (GIM) TEC data, which is provided by the NASA Jet Propulsion Laboratory (JPL), it is shown that SVM can be a suitable learning method to detect anomalies in TEC variations.
Ionospheric responses during equinox and solstice periods over Turkey
(2017-11-01) Karatay S.; Cinar A.; Arikan F.
Ionospheric electron density is the determining variable for investigation of the spatial and temporal variations in the ionosphere. Total Electron Content (TEC) is the integral of the electron density along a ray path that indicates the total variability through the ionosphere. Global Positioning System (GPS) recordings can be utilized to estimate the TEC, thus GPS proves itself as a useful tool in monitoring the total variability of electron distribution within the ionosphere. This study focuses on the analysis of the variations of ionosphere over Turkey that can be grouped into anomalies during equinox and solstice periods using TEC estimates obtained by a regional GPS network. It is observed that noon time depletions in TEC distributions predominantly occur in winter for minimum Sun Spots Numbers (SSN) in the central regions of Turkey which also exhibit high variability due to midlatitude winter anomaly. TEC values and ionospheric variations at solstice periods demonstrate significant enhancements compared to those at equinox periods.
Space weather studies of IONOLAB group
(2016-10-19) Arikan F.; Sezen U.; Toker C.; Artuner H.; Bulu G.; Demir U.; Erdem E.; Arikan O.; Tuna H.; Gulyaeva T.; Karatay S.; Mosna Z.
IONOLAB is an interdisciplinary research group dedicated for handling the challenges of near earth environment on communication, positioning and remote sensing systems. IONOLAB group contributes to the space weather studies by developing state-of-the-art analysis and imaging techniques. On the website of IONOLAB group, www.ionolab.org, four unique space weather services, namely, IONOLAB-TEC, IRI-PLAS-2015, IRI-PLAS-MAP and IRI-PLAS-STEC, are provided in a user friendly graphical interface unit. Newly developed algorithm for ionospheric tomography, IONOLAB-CIT, provides not only 3-D electron density but also tracking of ionospheric state with high reliability and fidelity. The algorithm for ray tracing through ionosphere, IONOLAB-RAY, provides a simulation environment in all communication bands. The background ionosphere is generated in voxels where IRI-Plas electron density is used to obtain refractive index. One unique feature is the possible update of ionospheric state by insertion of Total Electron Content (TEC) values into IRI-Plas. Both ordinary and extraordinary paths can be traced with high ray and low ray scenarios for any desired date, time and transmitter location. 2-D regional interpolation and mapping algorithm, IONOLAB-MAP, is another tool of IONOLAB group where automatic TEC maps with Kriging algorithm are generated from GPS network with high spatio-temporal resolution. IONOLAB group continues its studies in all aspects of ionospheric and plasmaspheric signal propagation, imaging and mapping.
The seasonal anomalies in ionosphere over Turkey
(2016-06-20) Cinar A.; Karatay S.; Arikan F.
The ionosphere is a region on the Earth's upper atmosphere which extends between 50 km to 1000 km from the ground. It is a layer that consists gases which are ionized by solar radiation. Solar radiation and incident angle of the Sun is important to understand how the Ionosphere affects the radio waves. Total Electron Content (TEC) is one of the important parameters that characterizes Ionosphere and directly related with the Sun's activity. The Ionosphere reflects radio waves and provides communication to distance places in short wave radio communication. In this study, behaviours of the Ionosphere in Turkey are examined for soltice and equinox periods between the years 2009 and 2012 which are one of solar minima and solar maxima periods, respectively by using Symmetric Kullback-Leibler Distance and L2 Norm methods.