Ionospheric heating with obliquely incident waves

Abstract

Nearly all ionospheric heaters operate at vertical incidence. Oblique waves cannot satisfy frequency‐matching conditions necessary to excite the parametric decay instability, and they are weakened by geometric spreading below the ionosphere. Those spreading losses are mitigated, however, by focussing near caustics. This paper calculates fields near the caustics of oblique waves and estimates the corresponding increases in electron temperature. It finds that a transmitter having a power‐gain product of 5 MW can raise the temperature of F‐layer electrons by a hundred degrees or more. Those temperature increases are initially concentrated in narrow regions near caustics, but spread by heat conduction over tens of kilometers.

Numerical simulation of oblique ionospheric heating by powerful radio waves

“…The simulation results thereby indicate that although energy losses due to geometric spreading of oblique propagation are larger than for vertical incidence, the ionospheric electron density and temperature can be disturbed considerably due to the electric field enhancement of the focused heating wave in the caustic region. Identical conclusions were obtained in previous studies (Field et al, 1990;Hinkel-Lipsker et al, 1993).…”

“…Budden (1976) presented the calculation of an electric field in the caustic region of the isotropic medium, and obtained the numerical result by ray tracing. Field et al (1990) used the numerical method of Warren et al (1982) to resolve the equation and obtained the electric field at any given point, including the caustic area and reflection region.…”

“…Modern ionospheric heaters can transmit the radio waves with different elevation angles Oyama et al, 2006), which means not just an overhead ionosphere region, but also that the remote ionosphere can be modulated by powerful radio wave incidence. Warren et al (1982) proposed a method to extend ray-tracing calculation into a strong focusing region and applied it to simulate the ionospheric electron temperature and density changes due to oblique heating (Field and Warber, 1985;Field et al, 1990). Hinkel-Lipsker et al (1993) introduced an ionospheric oblique heating model by coupling the ray-tracing numerical method and ionospheric plasma transport equations.…”

Some aspects of ion‐acoustic whistlers in the ionosphere in the presence of negative ions

“…There are several theories to explain the heating phenomena of earth's ionosphere [16][17][18][19][20], but no theory has been proved to be unique. Recently, Murtaza and Shukla [6] pointed out that the Landau damping of the lower hybrid waves can cause the electron heating, whereas the ion-cyclotron waves can heat the ions preferentially, i.e.…”