Plasma density irregularities in the high-latitude top side ionosphere

Abstract

Thermal plasma density measurements obtained by using the spherical electrostatic analyzer probe carried by the polar orbiting satellite Isis 1 have been spectrally analyzed to provide quantitative results on the amplitude and scale size distribution of the plasma irregularities in the high‐latitude top side ionosphere. The range of scale sizes examined, 200 m to over 100 km under normal conditions, is more than an order of magnitude greater than that available from ground‐based measurements. Data in the altitude range 574–3523 km and from the period February 1969 to April 1972 have been analyzed. Irregularities in the high‐latitude region from 40° invariant latitude up to the invariant L pole have been studied. In over 90% of the cases examined, the power spectra are found to fit a power law of the form P = P0f−β, where the index β varies within the range 1.5–2.5. The power spectral density was integrated over the scale size range 1–10 km in order to analyze quantitatively latitudinal variations of the irregularity amplitude. While the boundaries of the high‐latitude irregularity zone on particular orbits examined by using this technique are in agreement with earlier morphological studies, it is also evident that the amplitude of the irregularities within the high‐latitude irregularity region itself shows irregular enhancements above a generally raised amplitude level.

Effects of Strong Scattering on Transionospheric Propagation

“…In general, the results from in situ measurements (i.e., one-dimensional) show that p ranges between 1.5 and 2.5, with values close to 2 being most common. This result is found at both high (Phelps, Sagalyn, 1976) and equatorial (Livingston et al, 1981) latitudes for irregularities from -100 m to several hundred kilometers.…”

Dependence of the high-latitude plasma irregularities on the auroral activity indices: a case study of 17 March 2015 geomagnetic storm

“…Signatures of substorm expansion include precipitation of the highenergy particles into the ionosphere that is associated with injection of the high-energy particles in the magnetosphere (Arnoldy and Chan, 1969;McIlwain, 1974). The most intense ionospheric irregularities in the high-latitude ionosphere are caused by plasma processes associated with auroral activities, attributed to auroral particle precipitation, and dynamical processes including high-speed plasma convection (e.g., Phelps and Sagalyn 1976;Fejer and Kelley 1980;Keskinen and Ossakow 1983).…”

Theories of high‐latitude ionospheric irregularities: A review

“…Using a variety of experimental techniques, e.g., satellites [Dyson, 1969;Dyson et al, 1974;Sagalyn et al, 1974;Clark and Raitt, 1976;Phelps and Sagalyn, 1976;Rodriguez et al, 1981], rockets [Olesen et al, 1976;Ogawa et al, 1976;Kelley et al, 1980], scintillations [Aarons et al, 1969;Fremouw et al, 1977;Erukhimov et al, 1981], and radar backscatter [Weaver, 1965;Greenwald,, 1974;Hower et al, 1966;Vickrey et al, 1980;Hanuise et al, 1981], it is now known that the high latitude ionosphere, from the auroral zone into the polar cap, is a highly structured and nonequilibrium medium containing irregularities (plasma density fluctuations and structures) with scale sizes ranging from hundreds of kilometers to meters. Aside from being an interesting scientific phenomenon, ionospheric irregularities are of practical interest to the radio-physics community since they can disrupt transionospheric radio wave communications channels (see recent review by…”