Wide-band observations of lf hiss at Frobisher Bay (<i>L</i>= 14.6)

Morgan, M. G.

doi:10.1029/ja082i016p02377

Cited by 11 publications

(8 citation statements)

References 36 publications

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“…Thus a lack of a specific one-to-one correlation with ground-based geophysical activity during the detection of "auroral" signals in the frequency range of a few hundred kilohertz does not necessarily indicate a lack of energetic electrons in the topside ionosphere. Morgan [1977] also noted that a one-to-one correlation between LF hiss, extending up to this frequency range, and 30-MHz riometer activity was not always obtained.…”

Section: Discussionmentioning

confidence: 92%

Ground‐level detection of low‐ and medium‐frequency auroral radio emissions

Benson

Desch²,

Hunsucker³

et al. 1988

J. Geophys. Res.

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Natural radio emissions in the frequency range of several hundred kilohertz were detected at ground level in the auroral region. The measurements were made during a ground‐level observing program conducted near Fairbanks, Alaska, in the spring of 1986 in an attempt to detect auroral cyclotron‐maser generated whistler mode waves. The expectation for detecting such emissions was based on earlier theoretical work and satellite observations concerning auroral radio emissions. Four commercial communication receivers were used to obtain narrowband (3 kHz) samples of the radio noise spectrum at 150, 291, 500, and 700 kHz. Signals attributed to auroral processes were obtained on 7 of 15 nights of operation. Such signals were distinguished from man‐made interference by their bursty time structure and wide bandwidth (hundreds of kilohertz) and/or comparable signal intensities on orthogonal antennas. A one‐to‐one correlation with geophysical phenomena was not always readily evident. Emissions were observed even when magnetic activity was weak‐to‐moderate, and they were often absent during the strongest magnetic activity. Most of the strongest emissions, however, were observed in a small time interval around midnight magnetic local time (≈ ± 30 min). Such a tight ordering of the phenomena near magnetic midnight suggests a close tie‐in with auroral processes, even though the necessary conditions for the wave generation process are not readily apparent in conventional ground‐based geophysical records. The present results support earlier occasional reports in the literature, over the last 3 decades, of radio noise from the aurora at frequencies ∼ 100 kHz and indicate the importance of extending the upper frequency of ground‐based high‐latitude VLF stations to the vicinity of 1 MHz. Such observations may provide the means to continuously monitor cyclotron maser‐generated whistler emissions from the ground and, in turn, to determine under what conditions this specific instability process is initiated.

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Section: Discussionmentioning

confidence: 92%

Ground‐level detection of low‐ and medium‐frequency auroral radio emissions

Benson

Desch²,

Hunsucker³

et al. 1988

J. Geophys. Res.

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“…Ground based observations of radio noise generated along auroral field lines have been reported in many publications [Reber and Ellis, 1956;Dowden, 1959;Parthasarthy and Berkey, 1964;Helliwell, 1965;Ungstrup, 1967;Jorgensen, 1968;Harang, 1969;Morgan, 1977;Kellog andMonson, 1979' andSato andHayashi, 1985]. These measurements have covered a broad frequency range from several kilo-Hertz to above one mega-Hertz.…”

Section: Introductionmentioning

confidence: 99%

“…Here, it is important to point out that radio waves in the same frequency range as that associated with AKR have been observed by ground facilities [Reber and Ellis, 1956;Dowden, 1959;Jorgensen, 1968;Morgan, 1977] (although original emphasis of these investigations was to study whistlers generated by lightning or active experiments). In addition to these publications, we find that a recent paper by Benson et al [ 1988] is particularly interesting.…”

Section: Introductionmentioning

confidence: 99%

A theory of electron cyclotron waves generated along auroral field lines observed by ground facilities

Wu¹,

Yoon²,

Freund³

1989

Geophysical Research Letters

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A generation mechanism for radio waves in the frequency range 150–700 kHz observed by ground facilities is suggested in terms of an electromagnetic electron cyclotron instability driven by auroral electrons. The excited waves can propagate downward along the ambient magnetic field lines and are thus observable with ground facilities. The trapped auroral electrons are supposed to play an important role in the generation process, because they give rise to a thermal anisotropy which consequently leads to the instability. The present work is a natural extension of the theory proposed earlier by Wu et al. [1983] which was discussed in a different context but may be used to explain the observed waves originated at low altitudes (< 0.5 RE). This paper presents a possible wave generation mechanism valid in the entire auroral field line region of interest.

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“…In the introduction to a recent paper [Morgan, 1977a], I have summarized how a distinctly different type of hiss came to be recognized in observations on the ground at high latitudes. This hiss, which may extend from audio frequencies upward to 100 kHz or more, is of a burstlike character and is associated with bursts of auroral luminosity.…”

Section: •4uroral Hissmentioning

confidence: 99%

Equatorial hiss in the topside ionosphere

Morgan¹

1979

J. Geophys. Res.

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Equatorial hiss seen in the topside ionosphere by the Dartmouth experiment on Ogo 6, using an electric dipole antenna, is described. The observations are consistent with wave normal positions intermediate between the geomagnetic field and the resonance cone. Unlike that seen by Gurnett (1968) on Injun 3, using a loop antenna, the hiss is seen over the full range of altitudes from perigee to apogee (400–1100 km). There is a significant local time dependence, with concentration in the dawn and dusk sectors. Simultaneous occurrence with spread F would appear to be no more than coincidental. The possibility of spacecraft effects has been discounted. A search by Hoffman (1977) for equatorial electron fluxes such as those found by Heikkila (1971) has been negative. Thus the underlying cause of the hiss remains unknown. The hiss occurs in two distinct forms, ‘spiky’ and ‘nonspiky.’ No parameter has been found which clearly determines which type will occur, although there is some local time dependence. The hiss is most intense at the lowest frequency observed (20 Hz), but the spiky form may extend above 15 kHz and occasionally even to 200 kHz. Although it is largely confined to the equatorial zone, two instances were found when this hiss extended to middle latitudes and two when it occurred in the polar cap. In one of the latter it coexisted with the usual auroral hiss. A reassessment of synoptic recordings made at Huancayo during the International Geophysical Year has reaffirmed the absence of hiss, as well as whistlers, on the ground at the magnetic dip equator.

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Wide-band observations of lf hiss at Frobisher Bay (L= 14.6)

Cited by 11 publications

References 36 publications

Ground‐level detection of low‐ and medium‐frequency auroral radio emissions

Ground‐level detection of low‐ and medium‐frequency auroral radio emissions

A theory of electron cyclotron waves generated along auroral field lines observed by ground facilities

Equatorial hiss in the topside ionosphere

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