Preliminary results of measurements of the equatorial electrojet over India

Four Nike-Apache sounding rockets instrumented to measure the magnetic field and the electron density were launched from near the magnetic dip equator in India in January 1964. The initial results from one of these further establish the nature of the equatorial electrical currents in the ionosphere [Singer et al., 1951; Cahill, 1959]. A nuclear-free precession magnetometer measured the scalar magnitude (B) of the earth's magnetic field in terms of the precession frequency ƒ and the gyromagnetic ratio γ of the proton [Packard and Varian, 1954]: |B| = 2πƒ/γ Electron density measurements were made with a simple dc Langmuir probe. A constant 2.7 volt bias was applied between the tip of the probe and the base. The resulting current, which is proportional to the electron density if temperature effects are neglected, was monitored [Smith, 1963]. An ionization chamber densitometer for measuring air pressure, a barometric pressure switch, and a magnetic aspect sensor were also flown for trajectory and aspect determination. The information was transmitted to the ground by an FM-FM telemetry system. A magnetic tape recorder was then used to record the telemetered signal together with a crystal-controlled 100 kc/s reference signal for later data reduction.