SPEAR: Early results from a very high latitude ionospheric heating facility

Abstract

Early results are presented from high power ionospheric modification experiments with the SPEAR (Space Plasma Exploration by Active Radar) HF facility, which is used to generate artificial fieldaligned irregularities (AFAI) in the polar cap ionosphere. These AFAIs are detected both through HF coherent backscatter radar and bistatic HF Doppler experiments. The AFAIs created with SPEAR are demonstrated to provide an important geophysical diagnostic of the polar cap ionospheric electric field, and may also scatter radio waves out of the ionospheric waveguide, even when they have propagated over very considerable distances.

The polar-ionosphere phenomena induced by high-power radio waves from the spear heating facility

“…In the period of experiments on modification of the F 2 layer of the polar ionosphere, the development times of AFAIs amounted to t 1 ≈ 10−30 s and their relaxation times t 2 ranged from 15 to 40 s. We note that artificial irregularities in the F region of the polar ionosphere were also recorded in the SPEAR heating experiments using a system of CUTLASS coherent Doppler spectra in Hankasalmi (Finland) and Reykjavik (Iceland) [23].…”

SPEAR-induced field-aligned irregularities observed from bi-static HF radio scattering in the polar ionosphere

“…An investigation of SPEARinduced ion and plasma line spectral enhancements recorded by the EISCAT Svalbard UHF incoherent scatter radar points to sporadic E-layer enhancements consistent with the formation of cavitons and upper E-and F-region enhancements consistent with the actions of both the purely growing mode and the PDI . Yeoman et al (2007) has demonstrated that AFAIs in the F2 layer are detected both through the CUTLASS radars and bi-static HF Doppler radio scatter observations and that they provide an important geophysical diagnostic of the polar cap ionospheric electric field.…”

Model simulation of the large-scale high-latitude F-layer modification by powerful HF waves with different modulation

“…Recently, a new very high-latitude heating facility, SPEAR, has been built on Spitzbergen. This heater is utilized for the modification of the ionosphere inside the northern polar cap Yeoman et al, 2007;Clausen et al, 2008). It is now generally understood that high-power high-frequency radio waves, pumped into the ionosphere, cause a variety of physical processes in the ionospheric plasma.…”