A case of artificial triggering of VLF magnetospheric noise during the drift of a whistler duct across magnetic shells

Carpenter, D. L.; Stone, Keppler; Lasch, S.

doi:10.1029/ja074i007p01848

Cited by 24 publications

(3 citation statements)

References 10 publications

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“…Under this circumstance the motion of the magnetic field line can be identified as the E x B drift motion of the plasma. The results obtained from the model calculation compare favorably with the values deduced from cross-L drifts of whistler ducts [Carpenter and Stone, 1967;Carpenter et al, 1969]. As the whistler measurements have earlier been interpreted as evidence supporting the convective electric field theories [Axford, 1969], there is now considerable uncertainty about the real nature of the electric field detected by whistler observations following this demonstration that an electric field of similar character can be produced by a decaying ring current.…”

Section: Electric Fields Induced By the Ring Currentsupporting

confidence: 73%

Inductive electric fields in the Ionosphere‐Magnetosphere System

Kim¹,

Graham²,

Wang³

1979

Reviews of Geophysics

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In recent years, there has been increasing awareness of the importance of large‐scale electric fields in the earth's magnetosphere. Much attention has been directed to the quasi‐static electric field associated with charge separations generated by solar wind‐magnetosphere interaction, but these seem inadequate to explain many important processes. This paper reviews the evidence for the inclusion of electric fields of inductive origin, i.e., those due to time‐dependent currents in the magnetosphere‐ionosphere system. Attention is focused on processes associated with magnetospheric substorms, as they are well characterized by various types of evidence and do involve events such as energetic particle precipitation which require explanation beyond that provided by static electric field models. It is found that inductive electric fields are significant at times and should be included for a proper description of observed events.

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Section: Electric Fields Induced By the Ring Currentsupporting

confidence: 73%

Inductive electric fields in the Ionosphere‐Magnetosphere System

Kim¹,

Graham²,

Wang³

1979

Reviews of Geophysics

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“…These basic forms are commonly referred to as risers, fallers, and hooks [ Helliwell and Carpenter , ; Helliwell , ]. The earliest work observed the generation of these triggered emissions from Morse code VLF Navy transmissions [ Helliwell et al , ; Helliwell , ; Kimura , ; Lasch , ] or from natural signals such as whistlers [ Carpenter et al , ], while later work focused on observations of triggered emissions from Siple transmissions [ Helliwell and Katsufrakis , ; Stiles and Helliwell , ; Helliwell , , ; Sa , ]. Repeated observations of triggered emission behavior provided phenomenological descriptions of conditions for triggering.…”

Section: Past Observations and Modeling Effortsmentioning

confidence: 99%

An empirical profile of VLF triggered emissions

Spasojević

Inan

2015

JGR Space Physics

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The Siple Transmitter Experiment operated from 1973 to 1988 and generated a wealth of observations of nonlinear wave‐particle interactions including extensive recordings of triggered emissions generated by VLF signals injected into the magnetosphere from the transmitter at Siple Station, Antarctica. Due to their complex appearance and immensely varied behavior, triggered emissions remain poorly described and understood. This work provides a comprehensive statistical description of observed triggered emissions and establishes statistical bounds on triggered emission type (fallers, risers, and positive and negative hooks) and behavior (frequency changes between 1 kHz and 2.5 kHz with initial sweep rates between −2.5 kHz/s and 2.5 kHz/s, with risers undergoing a median frequency change of 556 Hz and fallers a median frequency change of −198 Hz). The statistical study also reveals an apparent dependence of the triggered emission behavior on the transmitted signal itself. Long tones and rising ramps generate more risers and positive hooks, while short tones and falling ramps produce more fallers and negative hooks. Triggered emissions also appear to favorably initiate with sweep rates similar to that of the triggering element, with the 1 kHz/s rising ramps triggering initial risers with a median sweep rate of 1.03 kHz/s and −1 kHz/s triggering initial fallers with a median sweep rate of −0.73 kHz/s. These results improve observations of wave modification resulting from wave‐particle interactions in the radiation belts and can be used to validate numerical simulations of triggered emissions.

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“…Only the paths associated with the largest travel time appear to be connected with triggering; i.e., the satellite spectrograms show the emissions to be linked with the final portion of the received pulse. When the triggering paths cross the equatorial plane, the local geomagnetic electron frequency [t is twice the Omega frequency co ([t • 2co); this relation seems to be associated with the shape of the whistler refractive index [Helliwell, 1969] and is also verified in parallel whistler triggering [Carpenter et al, 1969]. The existence of triggering by oblique whistlers raises the question of its causative mechanism.…”

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confidence: 93%

On the triggering capability of obliquely propagating whistlers

Brinca¹

1975

J. Geophys. Res.

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The nonlinear interaction between obliquely propagating whistlers and energetic electrons in fundamental gyroresonance is studied through numerical simulation. In analogy with the parallel whistler case, phase bunching occurs in the perpendicular velocities of the resonant electrons. The computed organized current brought about by the bunching suggests that obliquely propagating whistlers have the capability to trigger emissions through the gyroresonance interaction.

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A case of artificial triggering of VLF magnetospheric noise during the drift of a whistler duct across magnetic shells

Cited by 24 publications

References 10 publications

Inductive electric fields in the Ionosphere‐Magnetosphere System

Inductive electric fields in the Ionosphere‐Magnetosphere System

An empirical profile of VLF triggered emissions

On the triggering capability of obliquely propagating whistlers

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