Electromagnetic
In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions o ...
hiss is a naturally occurring
Extremely Low Frequency
Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric scien ...
/
Very Low Frequency
Very low frequency or VLF is the ITU designation for radio frequencies (RF) in the range of 3–30 kHz, corresponding to wavelengths from 100 to 10 km, respectively. The band is also known as the myriameter band or myriameter wave a ...
electromagnetic wave
In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, which propagate through space and carry momentum and electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visib ...
(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
In signal processing, white noise is a random signal having equal intensity at different frequencies, giving it a constant power spectral density. The term is used, with this or similar meanings, in many scientific and technical disciplines ...
(hence the
onomatopoetic
Onomatopoeia is the process of creating a word that phonetically imitates, resembles, or suggests the sound that it describes. Such a word itself is also called an onomatopoeia. Common onomatopoeias include animal noises such as ''oink'', ''m ...
name, "hiss").
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
The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined ...
, 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
The plasmasphere, or inner magnetosphere, is a region of the Earth's magnetosphere consisting of low-energy (cool) plasma. It is located above the ionosphere. The outer boundary of the plasmasphere is known as the plasmapause, which is defined ...
, 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
* Generation via electromagnetic impulses from terrestrial
lightning
Lightning is a naturally occurring electrostatic discharge during which two electrically charged regions, both in the atmosphere or with one on the ground, temporarily neutralize themselves, causing the instantaneous release of an avera ...
, specifically via lightning-generated
whistlers
Whistler may refer to:
* Someone who whistles
Places
Canada
* Whistler, British Columbia, a resort town
** Whistler railway station
** Whistler Secondary School
* Whistler Blackcomb, a ski resort in British Columbia
* Whistler Mountain, Briti ...
* Generation through coherent nonlinear interaction with energetic electrons near the equatorial plasmasphere
See also
*
Dawn chorus (electromagnetic)
*
Whistler (radio)
A whistler is a very low frequency (VLF) electromagnetic (radio) wave generated by lightning. Originally published by Stanford University Press, Stanford, California (1965). Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, wi ...
*
List of plasma (physics) articles
References
{{DEFAULTSORT:Hiss (Electromagnetic)
Electrical phenomena
Geomagnetism