• Diagnostics of magnetospheric electron density and ion composition using whistler mode sounding data from the image satellite

      Proddaturi, Radha Krishna (2007-08)
      This thesis reports the observations of the Magnetospherically Reflected (MR) Whistler Mode (WM) echoes on the IMAGE (Imager for Magnetopause-to-Aurora Global Exploration) satellite. These observations and interpretations were first reported in Sonwalkar et at. [2006]. MR-WM echoes were observed when RPI (Radio Plasma Imager) onboard the IMAGE satellite transmitted 3.2 ms pulses in the 6 kHz to 63 kHz frequency band. These echoes occurred at frequencies less than ~12 kHz with time delays ranging from 40 ms to 130 ms. MR-WM echoes were recorded when the satellite was at altitudes ranging from 700 km to 4000 km, geomagnetic latitudes from -30° to 50°, and magnetic local times 3 to 17. Ray tracing simulations confirmed that MR- WM echoes are a result of WM waves propagating along the geomagnetic field line and reflecting at an altitude where local flh [almost equal] f, where flh is the lower hybrid frequency and f is the wave frequency. In this interpretation, the lower and upper cutoff frequencies of the MR- WM echoes are equal to the flh at the satellite and the maximum flh along the geomagnetic field line passing through the satellite, respectively. These echoes were frequently accompanied by discrete WM echoes at frequencies greater than the maximum frequency of the MR- WM echoes. By matching the measured dispersions of the MR- WM and discrete WM echoes with that calculated from ray tracing simulations, remote estimates of electron density and ion effective mass were obtained along the geomagnetic field line passing through the satellite.