Fluctuating magnetic fields in the magnetosphere

Abstract

The study of Extremely-Low-Frequency (ELF) and Very-Low-Frequency (VLF) waves in space has been intensively pursued in the past decade. Search coil magnetometers, magnetic loop antennas, and electric dipole antennas have been carried on board many spacecraft. The measurements performed by these instruments have revealed a multitude of wave phenomena, whose study in turn is providing a wealth of information on the physics of the magnetospheric and ionospheric plasma. Two classes of wave phenomena are observed: whistlers and emissions. The observed whistler phenomena include: multiple hop ducted whistlers, ion-cutoff whistlers, ion cyclotron whistlers, subprotonospheric whistlers, magnetospherically reflected whistlers and walking trace whistlers.The emissions observed at high altitudes near the magnetic equator differ in many respects from those observed at low altitudes near the ionosphere. At high altitudes, inside the plasmasphere ELF hiss is the dominant emission and outside the plasmasphere chorus is the dominant emission. Also seen is a sub-LHR hiss band in the outer plasmasphere near the equator, and high pass noise and broadband noise in the outer nightside magnetosphere. At low altitude both ELF hiss and chorus are present but, here, ELF hiss is the dominant emission even outside the plasmasphere. Additional emissions, specific to low altitudes, such as VLF hiss and LHR noise are also observed. Although the observations of these phenomena by spacecraft have been complemented by many ground-based and rocket borne studies as well as by spacecraft observations of man-made signals, this paper reviews only satellite observations of signals of natural origin.

Survey of ELF-VLF plasma waves in outer radiation belt observed by Cluster STAFF-SA experiment

“…Chorus emissions are coherent right-hand polarized whistler mode waves observed near and outside the plasmapause, characterized by discrete structure of the dynamic spectrum (e.g. Russell et al, 1972;Storey et al, 1991;Sazhin and Hayakawa, 1992). Chorus is observed in a frequency band running from 0.1 to 0.8 f ce and often structured in two distinct bands: one above and one below 0.5 f ce (Tsurutani and Smith, 1977).…”

Whistler waves in Freja observations

“…Whistlers are dispersive waves (e.g., group and phase velocity are frequency dependent), which propagate obliquely to the ambient magnetic field. The spectrum of whistler waves are readily detected in ground‐based and spacecraft measurements in ionosphere and magnetosphere [ Russell et al , 1971; Al'pert , 1980; Carpenter , 1988; Sazhin et al , 1992; Singh et al , 1998], and may be implied in solar observations [ Mann and Baumgärtel , 1989; Chernov , 1990]. There are various of plasma instabilities in ionosphere and magnetosphere mostly due to anisotropic distribution of electrons, such as beams, loss‐cones, rings, or anisotropic temperature, which lead to the emissions in the whistler branch [ Gurnett and Frank , 1972; Maggs , 1976; Sazhin et al , 1993].…”

Oscillatory Nature of the Magnetosphere II. The EM-Background, Strong Packets of Waves, Resonances

“…Even the Earth's magnetic field tail has been discussed as such a system. A limited set of important historical papers include those of Watanabe (1959Watanabe ( , 1961, Obayashi (1965), Patel (1965Patel ( , 1968, Dungey (1968), Radoski (1967aRadoski ( , b, 1971, Brjunelli and Namgaladze (1969), McClay (1969), Ershkovich and Nusinov (1971), Orr and Mathew (1973), Russell et al (1972), McPherron et al (1972), Southwood (1974Southwood ( , 1975, Chen and Hasegawa (1974a, b), Fukunishi and Lanzerotti (1974a, b), Polyakov et al (1981), Krylov and Lifshits (1983), Belyaev et al (1984), Southwood (1985, 1986), Rickard and Wright (1994), and many others. A review including many references is, for example, by Gulelmi and Troitskaya (1973) (see also Cummings et al (1962)).…”