Auroral-E mode oblique HF propagation and its dependence on auroral oval position

High-latitude propagation studies using a meridional chain of LF/MF/HF receivers

“…2a shows no obvious example of this phenomenon, an effect which may be partly attributed to propagation via an enhanced auroral E-layer, as documented by several investigators (e.g. Hunsucker and Bates, 1969;Hunsucker et al, 1996;Milan et al, 1997).…”

“…Furthermore, as noted above, enhanced ionospheric propagation can be associated with auroral substorms due to the formation of an auroral sporadic E-layer supporting additional propagation modes with low absorption (e.g. Hunsucker and Bates, 1969;Hunsucker et al, 1996;Milan et al, 1997). Also, a number of studies indicate increases in HF ionospheric propagation preceding substorms; for example, Blagoveshensky and Vystavnoy (1994) observe enhancement of ionospheric propagation on 15-25 MHz 3-4 h preceding substorm onset, and Blagoveshensky and Borisova (2000) observe enhancement in ionospherically propagating HF signals associated with growth phase of substorms, 1-2 h prior to substorm onset, followed by the usual sharp decrease in ionospherically propagating HF signals at onset.…”

Ionosphere dynamics in the auroral zone during the magnetic storm of March 17–18, 2015

“…According to Enell et al (2015), the determination of Es-layer parameters at auroral latitudes like Sodankylä is a very complicated task. Hunsucker et al (1996) states that the Es-layer occurrences in Alaska, when 3<Kp<5, are of random "impulse" nature with an impulse duration from one minute to more than three hours and with an average duration of eleven minutes. On March 16 th the magnetometer recorded very weak variations of the X-component within the time interval 03:00 -10:00 UT, not exceeding 30 -40 nT.…”