Longitudinal variation of mid‐latitude hiss from six long duration balloon flights

Abstract

The longitudinal variation of mid‐latitude hiss as measured on six balloons at latitudes of 35°S–55°S, shows a significant minimum at 70°E–80°E, about 1000 km east of the geomagnetic conjugate of the Soviet transmitter, UMS (17.1 kHz). It is suggested that the well documented pitch angle diffusion induced by the UMS signal removes the ability of the trapped electrons to maintain the amplification of the hiss to at least the reflection and re‐ducting losses (∼20 dB) at the ends of the echoing, ducted path. The eastward shift of the minimum from the conjugate of UMS is primarily caused by the time taken by the eastward drifting electrons to recover this ability, though the effect is enhanced by the east–west asymmetry in the propagation of hiss under the ionosphere.

High‐latitude distributions of plasma waves and spatial irregularities from DE 2 alternating current electric field observations

“…The maximum intensi-ties, extending from roughly the region near 75 ø INL at 1300 MLT to the region near 68 ø INL at 2300 MLT, lie in the poleward portion of the evening auroral oval. Between 4 and 64 kHz this auroral belt distribution, commonly attributed to "auroral hiss," is clearly separated from the distribution of intense signals at INL < 60 ø, which is primarily caused by whistlers and VLF transmissions from the Earth's surface.The assumption that intense signals at INL < 60 ø originate primarily at the Earth's surface is based on a large body of previous studies [e.g.,Dowden and Holzworth, 1990]. It is also supported by the present statistics which show a dayside minimum, particularly at 16-64 kHz, that can be attributed to absorption of the surface transmissions in the lower ionosphere.The basic INL and asymmetric evening-morning distribution characteristics of auroral hiss, and correlations between auroral hiss and low-energy precipitating electrons, have been known for some time [e.g.,Gurnett, 1966;Gurnett and Frank, 1972;Laaspere and Hoffman, 1976, and references therein].…”

Plasmaspheric hiss overview and relation to chorus

“…An anthropogenic source of hiss, possibly due to power line harmonic radiation (PLHR) leaking into the plasmasphere from the ground Molchanov et al, 1991). In support of this mechanism, a modulation of mid-latitude hiss intensity by a ground-based VLF transmitter was reported, possibly related to its source (Dowden and Holzworth, 1990) (e.g., the ''Sunday effect'' when wave intensity would apparently be stronger during the work-week). 2.…”