Electromagnetic hiss is a naturally occurring Extremely Low Frequency/Very Low Frequency electromagnetic wave (i.e., 300 Hz - 10 kHz) that is generated in the plasma of either the Earth's ionosphere or magnetosphere. Its name is derived from its incoherent, structureless spectral properties which, when played through an audio system, sound like white noise (hence the onomatopoetic name, "hiss").
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Varieties
Hiss may be observed in any of several varieties depending on local time and L-shell of the observer:
- Plasmaspheric hiss is generally observed within the plasmasphere, peaking in frequency slightly below ~1 kHz and rarely exceeding 3 kHz.
- Exo-hiss and ELF hiss are two varieties of hiss observed outside of the plasmasphere, both having a spectrum similar to that of plasmaspheric hiss.
- Midlatitude hiss is generally observed outside of the plasmasphere and tends to have frequencies between 2 and 10 kHz.
- Auroral hiss is observed in the auroral zones of the Earth and can extend up to several hundred kHz.
Generation mechanisms
There are several proposed generation mechanisms for plasmaspheric hiss in particular, including:
- Generation from discrete chorus emissions [1] [2]
- Generation via electromagnetic impulses from terrestrial lightning, specifically via lightning-generated whistlers[3] [4] [5] [6]
See also
References
- ^ Santolík, O., J. Chum, M. Parrot, D. A. Gurnett, J. S. Pickett, and N. Cornilleau-Wehrlin (2006), Propagation of whistler mode chorus to low altitudes: Spacecraft observations of structured ELF hiss, J. Geophys. Res., 111, A10208, doi:10.1029/2005JA011462.
- ^ Bortnik, J., R. M. Thorne, and N. P. Meredith (2008), The unexpected origin of plasmaspheric hiss from discrete chorus emissions, Nature, 452, 62–66, doi:10.1038/nature06741.
- ^ Sonwalkar, V. S., and U. S. Inan (1989), Lightning as an embryonic source of VLF hiss, J. Geophys. Res., 94, 6986–6994.
- ^ Draganov, A. B., U. S. Inan, V. S. Sonwalkar, and T. F. Bell (1992), Magnetospherically reflected whistlers as a source of plasmaspheric hiss, Geophys. Res. Lett., 19, 233–236.
- ^ Green, J. L., S. Boardsen, L. Garcia, W. W. L. Taylor, S. F. Fung, and B. W. Reinisch (2005), On the origin of whistler mode radiation in the plasmasphere, J. Geophys. Res., 110, A03201, doi:10.1029/2004JA010495.
- ^ Meredith, N. P., R. B. Horne, M. A. Clilverd, D. Horsfall, R. M. Thorne, and R. R. Anderson (2006), Origins of plasmaspheric hiss, J. Geophys. Res., 111, A09217, doi:10.1029/2006JA011707.
Sources
- V. S. Sonwalkar (1995). Handbook of Atmospheric Electrodynamics, vol. II. CRC Press. pp. 426–426,432-433. ISBN 084932520X.
- Robert A. Helliwell (2006 [1965]). Whistlers and Related Ionospheric Phenomena. Dover Publications, Inc. ISBN 0-486-44572-0.
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