Statistical investigation of Satellite Trace (ST) and Multi-reflected Echo (MRE) ionogram signatures as a precursor to nighttime spread F development from Cyprus over the solar mini-max (2009-2016)

Multi-reflected echoes (MREs) and satellite traces (STs) are established in literature as ionogram signatures of Travelling Ionospheric Disturbances (TIDs) which is a phenomenon that apparently affects spread-F development mainly at nighttime mid-latitude ionosphere. A long-term statistical study has been undertaken to investigate the morphology of these signatures over the lower midlatitude European station of Nicosia, Cyprus (35.19^oN,33.38^oEgeographic; magneticdip.29.38°N) by inspecting all ionograms recorded by the DPS-4D digisonde in the interval 2009-2016. The results underline the systematic manifestation of TID signatures over Cyprus and a dependence of their seasonal and diurnal occurrence rate on solar activity with a seasonal peak of STs during summer and of MREs during January to April. Based on the experimental results, the seasonal occurrence rate of MREs and STs is found to increase by 75% and 56% during high solar activity periods. STs are well known ionogram signatures of TIDs and serve as precursors to the nighttime spread-F formation. The occurrences of mid-latitude spread-Fs over European longitude sector normally increases during summer. TIDs are also prominent at this interval of the year over nighttime mid-latitude ionosphere. MREs as an ionogram signature of TIDs over mid-latitude ionosphere are unique in nature. This paper reports, perhaps for the first time, presence of MREs over European mid-latitude ionosphere as a signature of TIDs.