Portal de Periódicos da CAPES

13. Whistlers: Diagnostic Tools in Space Plasma

1971; Elsevier BV; Linguagem: Inglês

10.1016/s0076-695x(08)60860-1

1875-6514

Neil Brice, Robert L. Smith,

Astro and Planetary Science

This chapter describes the role of whistlers as a diagnostic tool in space plasma. Whistlers are electromagnetic waves radiated by lightning discharges and subsequently dispersed by propagation in the earth's ionized outer atmosphere. Whistlers measure the electron densities at large distances in the earth's outer atmosphere, within the magnetosphere. The propagation delay is proportional to the square root of the density, weighted inversely as the square root of the magnetic field strength. Thus, the high electron density occurring over a relatively short distance in the ionosphere where the magnetic field is large makes only a minor contribution to the propagation time. At high altitudes, the path is long and the magnetic field weak so that most of the propagation delay occurs in this region. The chapter records naturally occurring electromagnetic waves in the frequency range from about 30 Hz to 30 kHz. The sensors range from multiturn loop antennas fitted into rocket nose cones to a dipole several miles long laid on the antarctic ice.