¹Department of Physics, National Institute of Technology ,Srinagar Kashmir India

²Mechanical Engineering Department National Institute of Technology Srinagar India

Characteristics of nighttime VLF/ELF emissions are examined on the basis of the data obtained at a low latitude ground station Jammu (geomag. lat., 22o 26' N; L = 1.17), India during our VLF/ELF campaign. From the detailed analysis of the acquired VLF/ELF data at Jammu we have found two remarkable events which clearly exhibit a rise in their frequency with time in pre midnight sectors during magnetically quiet periods. Our analysis shows that the emissions observed are of hiss and hissler types and are recorded during magnetically quiet period followed by disturbances. The observed frequency drift in VLF/ELF emissions at Jammu seems to be a rare phenomenon at low latitudes during magnetically quiet period in pre midnight sectors. This property of temporal frequency drift in VLF/ELF emissions observed at our station Jammu are interpreted in terms of a electron-cyclotron wave-particle interaction for wave excitation. The initial frequency increase is believed to be due to combined effect of L-shell drift of energetic electrons.