The Earth’s surface and lower Ionosphere (60-90km altitude) acts as perfect conductor at Very low
frequency waves (VLF: 3-30 kHz) and forms a natural waveguide known as earth-ionosphere waveguide
(EIWG). The VLF waves propagates long distance with very low attenuation by multiple reflection
between the boundaries of EIWG and carry information about the state of lower ionosphere. It is well
known that lower ionosphere which is sandwich region between atmosphere and ionosphere affect by
solar influence (e.g. solar flares, geomagnetic storm etc.), sources from troposphere
(lightning/thunderstorm/cyclone etc.) and from lithosphere (Earthquake/Tsunami) and therefore,
important for earth-ionosphere connections as well as weather and climate. In the present talk, we will
discuss with example role of VLF waves in probing effect of various geophysical sources on the lower
ionosphere.