Aspects of traveling ionospheric disturbance effects over Cyprus

Abstract

To investigate the dynamics of the nighttime ionosphere over the lower mid-latitude European station of Nicosia, Cyprus (35°N, 33°E geographic; magnetic dip. 29.38°N), ionograms recorded by the DPS-4D digisonde during the interval 2010-2016 have been analyzed thoroughly over magnetically quiet conditions to identify and characterize the nighttime spread F signatures. To establish the effect of different driving mechanisms on spread F within the framework of Perkins instability on a statistical basis, the spread F occurrence has been correlated with the presence of Traveling Ionospheric Disturbance (TID) wavefronts in the F region and/or the development of unstable sporadic E layers (spread Es) over the E region of the ionosphere. The presence of TID wavefronts in synchronism with spread F development has been identified by analyzing the GPS Rate of TEC Index (ROTI) fluctuation maps over the eastern Mediterranean nighttime ionosphere. Also, the association between the generation of spread Es layers prior to spread F development has been studied from the Height-time-intensity (HTI) analysis over the Nicosia Digisonde data. The results verify the systematic manifestation and therefore the significance of TID wavefronts and spread Es layers as triggering factors responsible for the seeding of spread F development over the lower European latitudes. A clear seasonal characteristic of spread F occurrence in synchronism with the presence of TID wavefronts and/or spread Es layers over the lower European midlatitudes is also established from 2010 to 2016. .