The Very Low-Frequency Emissions Generated in the Earth's Exosphere

Gallet, Roger M.

doi:10.1109/jrproc.1959.287267

Cited by 81 publications

(51 citation statements)

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“….As the stream velocity increases, the two bands of emission widen but the upper limit of the upper band remains at the gyrofrequency. The mathematical problem of finding the limits of the bands is identical with that used by Gallet (1959) in his treatment of the travelling-wave model and the expressions there obtained for discrete frequencies are the values for the limits of the bands.…”

Section: Discussion V (A) Oerenko'lj Radiation and Hissmentioning

confidence: 99%

“…The refractive index of the ionosphere, for propagation in the whistler, or longitudinal extraordinary mode with the wave normal direction approximately the same as that of the Earth's magnetic field, as derived from magneto-ionic theory, is given by Gallet (1959),…”

Section: Discussion V (A) Oerenko'lj Radiation and Hissmentioning

confidence: 99%

“…From this, Gallet (1959) finds that two frequencies are simultaneously generated, and these are given by where j is the wave frequency, jp=(N e e 2 je: o m)i=plasma frequency, j H = [loeH j m = electron gyrofrequency, Ne=electron density, e = electronic charge, m=electronic mass, H = magnetic field, e:o=electrical permittivity of free space, [lo=magnetic permeability of free space, v=velocity of ionized stream of particles, c=velocity of electromagnetic waves in free space.…”

mentioning

confidence: 81%

“…In his explanation of various classes of ionospherics Gallet (1959) has assumed an electron density distribution of the outer ionosphere such that f;/fH is a constant. During a period of frequent emission, such as when dawn chorus is occurring, it is to be expected that there would be an increase in electron density because of many streams of particles being trapped in the geomagnetic field, and the correct model may tend to approach fp/f H constant.…”

Section: (B) Different Classes Of Ionosphericsmentioning

confidence: 99%

“…(1960) has suggested the term" Ionospherics". Several attempts have been made to explain the generation of ionospherics, such as the travelling-wave amplification model of Gallet (1959), the Cerenkov radiation model of Ellis (1959), and the Doppler-shifted gyrofrequency model of MacArthur (1959) and Murcray and Pope (1960). These all suffer from lack of generality.…”

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confidence: 99%

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A Study of Ionospherics at Macquarie Island

McInnes¹

1961

Aust. J. Phys.

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SummaryVery low frequency radio emissions of natural origin, sometimes known as iono. spherics, recorded at Macquarie Island have been examined and grouped into classes. The diurnal variations of all classes show a non·uniform distribution with a peak shortly before local midday. The ionospherics appeared to fall into three groups as regards dependence on magnetic K·index. Strong correlations were discovered between values of emission frequency and K.index, for several classes of ionospherics. The role of Cerenkov radiation in the generation of ionospherics is discussed. Suggested energy distributions are put forward to explain various classes of ionospherics. The magnetic associations and diurnal variation are explained on the basis of current geomagnetic disturbance theory. Ionospheric absorption is also considered to affect the diurnal variation. The phenomenon of" surf", as reported by Campbell and Pope, is discussed.

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Section: Discussion V (A) Oerenko'lj Radiation and Hissmentioning

confidence: 99%

Section: Discussion V (A) Oerenko'lj Radiation and Hissmentioning

confidence: 99%

mentioning

confidence: 81%

Section: (B) Different Classes Of Ionosphericsmentioning

confidence: 99%

mentioning

confidence: 99%

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A Study of Ionospherics at Macquarie Island

McInnes¹

1961

Aust. J. Phys.

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Dayside auroral hiss observed at South Pole Station

et al. 2013

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[1] We performed a statistical study of low frequency (LF) auroral hiss recorded at South Pole Station in 2004, 2005, and 2007, and very low frequency (VLF) hiss recorded in [2000][2001][2002][2003][2004][2005][2006][2007][2008]. As expected, most auroral hiss occurs in the pre-midnight sector. However, there is a secondary peak in occurrence in the pre-noon sector (1000-1530 UT; 0630-1200 magnetic local time (MLT)) and somewhat more events occur in the post-noon sector (1530-2100 UT; 1200-1730 MLT), with a null in occurrence around noon MLT. Individual dayside events appear similar to nightside hiss, but statistically they do not extend to as high frequencies. Solar wind discontinuities or impulses on the magnetopause are not correlated with these events. All-sky camera, photometer, magnetometer, riometer, and VLF receiver data show that dayside LF hiss almost always extends to the VLF range and is often associated with active aurora. Examination of interplanetary magnetic field (IMF), substorm conditions, and Kp/AE/QI indices at times of dayside hiss suggests differences between the pre-noon and post-noon events: pre-noon events are associated with IMF B y < 0, whereas post-noon events favor B z < 0 and show a weaker correlation with B y > 0. The correlation between pre-noon events and B y < 0 may arise because under those conditions, the pattern of field-aligned currents (FACs) shifts to later magnetic local times, causing upward FACs to be dominant during pre-noon hours at 74 ı , the invariant latitude of the South Pole. Unlike pre-noon events, post-noon events are more often associated with substorm activity on the nightside and favor elevated Kp indices, suggesting a connection of post-noon events to nightside activity.

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Pulsating auroral electron flux modulations in the equatorial magnetosphere

et al. 2013

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[1] In this study, we present the first in situ continuous measurements of electron flux modulations in the near-equatorial magnetosphere correlated with pulsating aurora (PA) observations. The contested conjecture that the source of these electrons originates near the equator, made decades ago using sounding rocket data, has now been confirmed using this data. We compared the frequencies of equatorial electron flux pulsations and PA luminosity fluctuations at their ionospheric footprint, using simultaneous satellite-and ground-based data from GOES 13 and Time History of Events and Macroscale Interactions during Substorms (THEMIS) instrumentation. Observations of PA were obtained on 15 March 2008 using a THEMIS All-Sky Imager (ASI) located in northern Canada. The field line footprint of the geostationary GOES 13 satellite, mapped down to the ionosphere at 100 km, falls within the field-of-view of the ASI. We examined electron flux data from the Magnetospheric Electron Detector (MAGED) on GOES 13, in the energy range of 30 to 50 keV, by computing an array of the correlation coefficients between the pixel luminosity for each individual pixel of the ASI images and the flux measurements at the satellite. The results reveal a direct correlation between diffuse luminosity fluctuation periods near the ground and particle pulsation periods. The time variance between the two data sets was examined in order to explore the validity of the equatorial source region premise. The resulting time lag of < 1 s in the PA measurements is consistent with this claim. We also report on a preliminary quantification of the loss cone using the MAGED telescope response functions.

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The Very Low-Frequency Emissions Generated in the Earth's Exosphere

Cited by 81 publications

References 8 publications

A Study of Ionospherics at Macquarie Island

A Study of Ionospherics at Macquarie Island

Dayside auroral hiss observed at South Pole Station

Pulsating auroral electron flux modulations in the equatorial magnetosphere

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