Mode conversion and auroral effects observed on a polar VLF propagation path

Westerlund, S.; Svennesson, J.

doi:10.1016/0021-9169(71)90128-0

Cited by 11 publications

(3 citation statements)

References 27 publications

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“…We also received the NLK (18.6 kHz, Jim Creek, Washington) signal which propagates through the subauroral region (<55 ø CGL), but no clear propagation disturbances were observed during the substorms on November 13, 1979. Also shown in Figure 1 Westerlund and Svennesson, 1971]. However, when the receiver site is located at low latitude, the higher-order modes excited at the ionospheric discontinuity in the auroral zone are attenuated during propagation from the auroral zone to the low latitudes.…”

Section: Substorms On November 13 1979mentioning

confidence: 97%

“…In spite of the great advantages of VLF wave propagation for detection of precipitating energetic electrons, as mentioned above, investigations of a relation between VLF wave propagation disturbances and magnetospheric substorms are quite sparce. It has been shown that there is a close relation between VLF phase anomalies and occurrence of geomagnetic bays [Westerlund and Svennesson, 1971;Svennesson, 1973;Westerlund and Reder, 1973]. In addition, the flux of precipitating electrons with E > 40 keV has been estimated from phase anomalies on a VLF signal propagating along a mid-latitude path during the night [Potemra and Rosenberg, 1973].…”

Section: Introductionmentioning

confidence: 99%

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Quantitative study of substorm‐associated VLF phase anomalies and precipitating energetic electrons on November 13, 1979

Kikuchi¹,

Evans²

1983

J. Geophys. Res.

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The phase anomalies associated with substorms are observed on VLF signals propagating on transauroral paths (transmitters at OMEGA‐ALDRA (13.6 kHz), GBR (16.0 kHz), and OMEGA‐NORTH DAKOTA (13.6 kHz)) which were continually received at Inubo, Japan, during the events on November 13, 1979. Detailed comparisons are made between these phase anomalies and geomagnetic bays, and quantitative relations are obtained with precipitating energetic electrons (E > 30, E > 100, and E > 300 keV) detected on board the TIROS‐N and NOAA 6 satellites. It is concluded that two types of VLF phase anomalies exist which, in turn, are associated with two phases in the history of energetic electron precipitation into the atmosphere. The first type of phase anomaly is associated with direct injection of energetic electrons into the outer magnetosphere and atmosphere which, in turn, is completely correlated in time with development of the auroral electrojet current system. The second type arises from energetic electrons which subsequently precipitate from a trapped electron population and has a delayed onset and prolonged duration. An excellent quantitative correlation is obtained between the logarithm of the electron flux and the magnitude of the phase anomaly on the OMEGA‐ALDRA signal. From the local time characteristics of this quantitative relation it is deduced that the electrons with E > 300 keV are the main source of D region ionization responsible for the VLF phase anomaly.

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Section: Substorms On November 13 1979mentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Quantitative study of substorm‐associated VLF phase anomalies and precipitating energetic electrons on November 13, 1979

Kikuchi¹,

Evans²

1983

J. Geophys. Res.

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“…Anomalous effects of mode conversion were found initially for transequatorial paths [Lynn, 1967], but the reasons are not yet understood. Westerlund and Svennesson [1971] have discussed qualitatively why anomalous mode conversion effects are seen at auroral latitudes for a transpolar path. However, these anomalous effects have never been observed for mid-latitude paths; moreover, they have not yet been investigated quantitatively.…”

Section: Introductionmentioning

confidence: 99%

Winter anomalous effects of mode conversion observed in mid‐latitude VLF transmission

Muraoka¹

1983

J. Geophys. Res.

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Mode conversion effects were observed on a long-distance VLF propagation path at mid-latitudes during two winters: 1974/75 and 1975/76. The occurrence of amplitude minima as a result of interference between modal components was found to be delayed in the sunrise transition during the D region winter anomaly. At the same time the depth of amplitude fading and the magnitude of phase step decreased and, sometimes, became indiscernibly small. These anomalous effects of mode conversiøn are interpreted as being due to the lowering of the nighttime VLF reflection height in excellent agreement with the high absorption of HF radio waves in the daytime. The implication is that the electron density in the D region is enhanced day and night during winter anomalous days. Dynamical processes in the middle atmosphere are likely to play an important role in the day-long enhancement.

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Experimental evaluation of relative mode parameters in the irregular earth-to-ionosphere waveguide

Fleer¹,

Shchavelev²

1974

Meas Tech

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Mode conversion and auroral effects observed on a polar VLF propagation path

Cited by 11 publications

References 27 publications

Quantitative study of substorm‐associated VLF phase anomalies and precipitating energetic electrons on November 13, 1979

Quantitative study of substorm‐associated VLF phase anomalies and precipitating energetic electrons on November 13, 1979

Winter anomalous effects of mode conversion observed in mid‐latitude VLF transmission

Experimental evaluation of relative mode parameters in the irregular earth-to-ionosphere waveguide

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