Electron precipitation in the vicinity of a VLF transmitter

Abstract

Using high‐resolution pitch angle measurements made by a magnetic focusing electron spectrometer on the S3‐3 satellite, angular distributions of 235‐keV electrons precipitated in the slot region of the magnetosphere by a ground‐based VLF transmitter are compared with the pitch angle distributions that would be produced by various patterns of longitudinal interaction regions. The observed electrons are in the drift loss cone, necessitating the use of a trace‐back‐to‐longitude‐of‐origin technique coupled with a two‐dimensional convolution program describing the response of the electron spectrometer. The data are well fit both with theoretical calculations of ionospheric field intensity patterns above a transmitter and with a similar pattern of received field intensities measured along a traverse in the conjugate region. The agreement between the data and field patterns implies a linear or quasi‐linear wave‐particle interaction. The energy‐frequency relationship between the electrons and the waves implies an interaction region low on the magnetic field line rather than near the equator, as has been determined for similar precipitations in the inner zone.

Physical mechanisms of man-made influences on the magnetosphere

“…Considering that the frequencies of the transmitters are between 10 and 25 kHz and using Equation (18), it is shown that the energy of the precipitated particles is a few keV. The resonance condition for relativistic electrons with a local pitch angle a is given by (Koons et al, 1981;Vampola, 1987):…”

“…Their ionospheric perturbations have mainly been observed in-situ by satellites. It includes: triggering of new waves (Dowden et al, 1978;Bell et al, 1983;Titova et al, 1984;Bell, 1985;Groves et al, 1988;Bell andNgo, 1988, 1990;Sotnikov et al, 1991), ionospheric heating (Inan, 1990;Bell et al, 1991;Dowden and Adams, 1992;Inan et al, 1992;, wave-electron interactions (Inan et al, 1978;Inan et al, 1982Inan et al, , 1984Inan et al, , 1985Dowden, 1985), and particle precipitation (Koons et al, 1981;Vampola, 1987Vampola, , 1990. Moreover, magnetospheric amplification of VLF pulses through wave-electron interaction is enhanced during magnetic storms (Smith and Clilverd, 1991).…”

Hard X ray survey of energetic electrons from low‐Earth orbit

“…Observations of nearly mono-energetic-electron ,beams in the drift loss cone within this region by Vampola, Koons, Imhof, Datlowe, and coworkers [Vampola, 1977[Vampola, , 1987Koons et al, 1981;Imhof et al, 1983Imhof et al, , 1989Imhof, 1990, 1993] have been interpreted in terms of pitch-angle scattering caused by cyclotron-reSonant interactions of trapped electrons with waves from ground-based VLF transmitters. These waves propagate within the plasmasphere in the Whistler mode.…”

A general association between discrete auroras and ion precipitation from the tail

“…A complete ion and electron spectrum was taken every second and a complete angular distribution was obtained in one spin period (20 s). We also use data from a solid state detector telescope which measured energetic ions (described by Lyons et al [1987]) and a magnetic focusing spectrometer which measured energetic electrons (described by Vampola [1987]; Vampola and Adams [1987]). From these detectors, we use the two lowest energy ion channels (integral flux of > 80 and > 165 keV protons) and the two electron energy channels with the best sensitivity (centered at 33 keV and 235 keV).…”