Medium scale travelling ionospheric disturbance detection using GPS MyRTKnet

Using Vertical Total Electron Content (VTEC) data derived from the Malaysian Real Time Kinematic network (MyRTKnet), we present a simple technique to estimate the medium scale-travelling ionospheric disturbance (MSTID) at low latitudes. Medium-scale travelling ionospheric disturbances are wave-like perturbations of the ionospheric plasma with wavelengths of several hundred kilometres and velocities of several hundred metres per second. MSTID is one of the most common ionospheric phenomena that generally induces the perturbations of ionospheric total electron content (TEC). To identify these perturbations, the trend of every curve of VTEC against time is subtracted from the original data. A month data of September 2007 (relatively low geomagnetic activity) over four GPS MyRTKnet stations - AYER, GETI, PASP and KRAU have been evaluated. The presence of MSTID if there exists of any mode between 15 and 60 min with an amplitude greater than 0.1 TECU. The analysis of the cross correlation of de-trended VTEC data yielded MSTID velocities around 150.7 ms^-1 at day time and 89.8 ms^-1 at night time with occurrence 25.4% and 8.75% respectively. Based on phase lag among the de-trended VTEC waveforms along latitude and longitude of the I_PP trajectory of the four stations, the movement of the ionospheric wave motion (MSTID) propagated southward.