This paper provides the first observations of EIA asymmetry by receiving beacon transmissions onboard low earth orbiting satellites from a single station ground-based receiver. The EIA strength and asymmetry are derived from the latitudinal profiles of TEC obtained from a radio beacon receiver at Trivandrum (8.5¿N, 77¿E, diplat ~0.5¿N). These two parameters, obtained well ahead of the onset time of ESF, are shown to have a definite role on the subsequent ESF activity. In the present paper, both these factors are combined to define a new 'threshold parameter' for the generation of ESF. It has been shown that this parameter can define the state of the 'background ionosphere' conducive for the generation of ESF irregularities much prior to its onset.