Investigation of natural and artificial stimulation of the ionospheric Alfvén resonator at high latitude

Abstract

A brief review is provided of recent progress in understanding the Ionospheric Alfvén Resonator (IAR) at high latitude. Firstly, naturally-occurring resonances of the IAR as detected by pulsation magnetometers in the auroral zone at Sodankylä and in the polar cap at Barentsburg are considered. The characteristics of the IAR in the two regions are broadly similar, although the effects of solar illumination are less clear at the higher latitudes. Secondly we review recent attempts to stimulate the IAR through high-power radio frequency experiments both in the auroral zone at Tromsø with the European Incoherent SCATter (EISCAT) heater, and within the polar cap at Longyearbyen with the Space Plasma Exploration by Active Radar (SPEAR) facility. In the auroral zone at, Tromsø the stimulated IAR has been observed by ground-based magnetometers, and through electron acceleration observed on the FAST spacecraft. At SPEAR in the polar cap, the stimulated IAR has been investigated, with ground magnetometers, with the first results indicative of a positive detection.

Nonlinear effects in the ionospheric Alfvén resonator

“…Assume that the plasma mass density ρ ( x ) changes in a stepwise manner, so that for x < 0 < H (region 1 in Figure 1) the Alfvén speed V A = ∣ B x ∣( μ 0 ρ ) −1/2 is a constant V A ,1 , and for H < x (region 2 in Figure 1) the Alfvén speed is another constant V A ,2 (see the bold curve in Figure 1). Similar systems are often used for investigation of IAR properties[e.g., Trakhtengerts et al , 2000; Yeoman et al , 2008]. Below, the 1D model is used to provide expressions for the nonlinear force in the Alfvén resonator.…”

Diurnal behaviour of the ionospheric Alfvén resonator signatures as observed at high latitude observatory Barentsburg (&lt;I&gt;L&lt;/I&gt;=15)

“…These spectral resonant structures (SRS) have been detected and investigated at low latitudes (Bösinger et al, 2002), at mid-latitudes Pokhotelov et al, 2003;Odzimek et al, 2004;Molchanov et al, 2004), and in the auroral zone (Belyaev et al, 1999;Semenova et al, 1999;Yahnin et al, 2003;Hebden et al, 2005). Recently, SRS were observed on Svalbard, that is, at L∼15 (Semenova et al, 2005;Yeoman et al, 2007).…”