VLF Emissions in the Magnetosphere

Rycroft, M.J.

doi:10.1029/rs007i008p00811

Cited by 45 publications

(19 citation statements)

References 103 publications

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“…They may also propagate in ducted mode along a lower L-value which can be received at low latitudes (Rycroft, 1972;Chang and Inan, 1983). The wave-normal angle of these waves in the generation region may be quite large.…”

Section: Experimental Observationmentioning

confidence: 99%

Two types of ELF hiss observed at Varanasi, India

Singh

Patel

et al. 1999

Ann. Geophys.

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Abstract. The morphology of ELF hiss events observed at low-latitude ground station Varanasi (L = 1.07, geomagnetic latitude 14°55¢N) are reported, which consist of two types: (1) events which propagated in ducted mode along the geomagnetic ®eld line corresponding to observing station Varanasi and (2) events which propagated in ducted mode along higher L-values (L = 4±6), after reaching the lower edge of ionosphere excite the Earth-ionosphere wave guide and propagate towards equator to be received at Varanasi. To understand the generation mechanism of ELF hiss, incoherent Cerenkov radiated power from the low latitude and middle latitude plasmasphere are evaluated. Considering this estimated power as an input for wave ampli®cation through wave±particle interaction, the growth rate and ampli®cation factor is evaluated which is too small to explain the observed wave intensity. It is suggested that some non-linear mechanism is responsible for the generation of ELF hiss.

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Section: Experimental Observationmentioning

confidence: 99%

Two types of ELF hiss observed at Varanasi, India

Singh

Patel

et al. 1999

Ann. Geophys.

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“…Liehmon's (1967) results, however, indicate that the off-equatorial growth rate can become quite significant, especially at higher frequencies. Regions of lower magnetic field strength and larger electron number density are also advantageous (Rycroft, 1972).…”

Section: A B Collier and A R W Hughes: Modelling Substorm Chorusmentioning

confidence: 99%

Modelling substorm chorus events in terms of dispersive azimuthal drift

Collier

Hughes

2004

Ann. Geophys.

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Abstract. The Substorm Chorus Event (SCE) is a radio phenomenon observed on the ground after the onset of the substorm expansion phase. It consists of a band of VLF chorus with rising upper and lower cutoff frequencies. These emissions are thought to result from Doppler-shifted cyclotron resonance between whistler mode waves and energetic electrons which drift into a ground station's field of view from an injection site around midnight. The increasing frequency of the emission envelope has been attributed to the combined effects of energy dispersion due to gradient and curvature drifts, and the modification of resonance conditions and variation of the half-gyrofrequency cutoff resulting from the radial component of the E×B drift.A model is presented which accounts for the observed features of the SCE in terms of the growth rate of whistler mode waves due to anisotropy in the electron distribution. This model provides an explanation for the increasing frequency of the SCE lower cutoff, as well as reproducing the general frequency-time signature of the event. In addition, the results place some restrictions on the injected particle source distribution which might lead to a SCE.

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“…It is generally accepted that the VLF whistler-mode waves are generated by the cyclotron instability of radiation belt energetic particles in the inner magnetosphere (e.g., Rycroft, 1972;Trakhtengerts and Rycroft, 2008). The frequency of excited waves is controlled by the equatorial electron gyrofrequency fce, which is proportional to the local magnetic field strength.…”

Section: Discussionmentioning

confidence: 99%

New Type of High-Frequency Discrete VLF Emissions ("BIRDS") at Auroral Latitudes

Manninen¹,

Turunen²,

Клейменова³

et al. 2018

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Based on VLF observations in Northern Finland at Kannuslehto (KAN, L ~ 5.5), recently we revealed a new and previously unknown daytime type of VLF emissions at frequencies well above 4÷5 kHz. These emissions have neither been seen before because they were hidden by strong impulsive sferics originating in lightning. The peculiar VLF signals, discovered after filtering out the sferics, were studied. It is shown here that these emissions, which have a complicated spectral structure, occur during the winter around local noon under the quiet solar and geomagnetic conditions (Vsw < 400÷500 km/s, BIMF < 5÷7 nT, Np < 5÷8 cm -3 , AE < 150÷200 nT). These emissions are usually right-hand polarized and can last for several hours as a series of separate short discrete wideband (from 4 to 10 kHz and higher) signals, each with a duration between one and several minutes. We suppose that these waves are generated via the electron-cyclotron resonance mechanism deep inside the magnetosphere at much lower L-values than KAN. However, the details of the generation and propagation mechanisms of these newly discovered VLF emissions remain unclear.

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VLF Emissions in the Magnetosphere

Cited by 45 publications

References 103 publications

Two types of ELF hiss observed at Varanasi, India

Two types of ELF hiss observed at Varanasi, India

Modelling substorm chorus events in terms of dispersive azimuthal drift

New Type of High-Frequency Discrete VLF Emissions ("BIRDS") at Auroral Latitudes

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