Observation and characterization of traveling ionospheric disturbances induced by solar eclipse of 20 March 2015 using incoherent scatter radars and GPS networks

Abstract We present the results of a comprehensive study of traveling ionospheric disturbances (TIDs) occurring over Europe during the total solar eclipse of 20 March 2015. For detection of wave structures and estimation of TID parameters, two remote sensing techniques were combined:incoherent scatter (IS) radars andEuropean and Finnish dense GPS receiver networks. Similar procedures were applied for processing bothIS and GPS data. We developed a new method enabling to analyze TEC data separately in thetemporal and spatial domain. For the first time, we produced maps of band-pass filtered TEC variations and reported both large- and medium-scale prevailing TIDs observed duringthis solar eclipse , both having similar periods about 50 - 60 min. The downward phase progression indicatesthat TIDs were induced by atmospheric gravity waves generated at lower altitudes. The variations in IS power attained peak relative amplitudes of 0.22 (22%) at 220 km over Tromso and of 0.17 (17%) at 200 km over Kharkiv. The vertical phase velocity was about 57 m/s over Tromso. It increased from 25 to 170 m/s over Kharkiv with altitude increasingfrom 120 to 310 km. Over Western Europe, large-scale TIDs (LSTIDs) hadprevailing north-east direction over the region from 45°to 50°N and 2°W to 8°E. Here, their average horizontal phase velocity V m was 803 ± 281 m∕s and the absolute amplitudes of TEC variations usually do not exceed 0.17 TECU. For this region, we found strong difference in LSTID propagation azimuth between the solar eclipse day and the two adjacent days of 19 and 21 March 2015, used as reference. This most likely indicates that these LSTIDs were directly caused by the solar eclipse through local heating/cooling processes occurring during the passing of the Moon penumbra. Over another region, limited by 44°– 50°N and 13°– 19°E, the LSTIDs had south-east propagation. Over Finland, the LSTIDs also propagated southeastward having V m = 774 ± 202 m∕s and TEC amplitudes up to 0.6 TECU. A possible evidence of LSTID generation at high latitudes indirectly by this solar eclipse through an excitation of slow magnetosonic waves was experimentally detected. Medium-scale TIDs (MSTIDs) propagated southeastward over both regions having V m values of 144 ± 54 m∕s over Western Europe and of 104 ± 43 m∕s over Finland. Over Northern Europe, the maximum MSTID amplitudes were greater by a factor of 5 compared to those over Western Europeand reached 0.4 TECU. We did not detect a clear difference in MSTID propagation between solar eclipse and reference days. The IS and GPS results are in consistency with each other. Thedetected TID parameters ofpredominant periods, relative amplitudes, altitude range and MSTID horizontal propagation direction generally correspond to the results of other studies.