Dual radar investigation of E region plasma waves in the southern polar cap

Abstract

Origins and characteristics of small‐scale plasma irregularities in the polar ionosphere are investigated using a dual radar setup in which the E region is probed from opposite directions by two Super Dual Auroral Radar Network facilities at the McMurdo and Dome Concordia Antarctic stations. In certain time intervals, velocity agreement is observed when velocities are compared at the same physical location in the horizontal plane. Such an agreement is widely expected if velocity at a given location is largely controlled by the convection electric field. In other cases, however, velocity agreement is unexpectedly observed when measurements are considered at the same slant range (distance along the radar beam) for both radars. This implies that it is not the electric field at a given location that is a controlling factor. Raytracing results show that the same range agreement may be explained for certain E region density conditions when echo altitude increases with radar range. Backscatter observations under generally unfavorable conditions for irregularity generation and the critical role of propagation conditions in the polar cap are discussed. The observed E region velocity in the polar cap is demonstrated to depend indirectly on the plasma density distribution, which is important for establishing the fundamental dependence on the convection electric field.

Toward an integrated view of ionospheric plasma instabilities: Altitudinal transitions and strong gradient case

“…In particular, we are interested in decameter-scale waves ≥ 10 m, which were the focus of several recent experimental studies using coherent radars within the Super Dual Auroral Radar Network (SuperDARN) [e.g., Forsythe and Makarevich, 2015;Lamarche and Makarevich, 2015, and references therein] and for which a fluid approach is applicable at least in the E and lower F regions (up to ∼130-140 km depending on V E ). In the modeling part of this study, however, we focus on small-scale irregularities (i.e., below 100 m in wavelength ).…”

“…In the modeling part of this study, however, we focus on small-scale irregularities (i.e., below 100 m in wavelength ). In particular, we are interested in decameter-scale waves ≥ 10 m, which were the focus of several recent experimental studies using coherent radars within the Super Dual Auroral Radar Network (SuperDARN) [e.g., Forsythe and Makarevich, 2015;Lamarche and Makarevich, 2015, and references therein] and for which a fluid approach is applicable at least in the E and lower F regions (up to ∼130-140 km depending on V E ). Decameter scales refer to wave numbers k ≈ 0.6 m −1 , i.e., to the "middle" part of each pattern in Figure 1.…”

A modeling study of asymmetries in plasma irregularity characteristics near gradient reversals

“…Importantly, both E-and F-region irregularities are observed by the same radar (e.g., recent papers by Lamarche and Makarevich, 2015;Forsythe and Makarevich, 2015) and measurements of the background convection velocity V E are routinely derived from F-region observations. In addition to their ability to observe largescale structures in the context of background plasma convection, SuperDARN radars provided important observational evidence in support of the GDI mechanism being responsible for the irregularity formation and asymmetries near gradient reversals Koustov et al, 2012).…”

Asymmetry in the Farley‐Buneman dispersion relation caused by parallel electric fields

“…Coherent radars within the Super Dual Auroral Radar Network (SuperDARN) measure irregularity phase velocity very accurately (with uncertainty of less than about 1%). Many of the high southern latitude SuperDARN radars including radars at the South Pole, McMurdo, Dome Concordia, and Syowa Antarctic stations have aspect angles of different polarity within their E region fields of view (FoVs) [ Makarevich et al , ; Forsythe and Makarevich , ]. The phase velocity along the same radar beam can be examined as a function of the aspect angle [ Ogawa et al , ; Nielsen , ; Kustov et al , ; Makarevich et al , , ].…”

“…The gyrofrequencies for ions and electrons (negative in this notation convention) were taken to be constant with altitude and equal to 150 s −1 and −10 7 s −1 , respectively. The geographic coordinates of 80°E, 60°S and the time of 14:00 magnetic local time (MLT) on 15 February 2013 were selected to represent summer daytime conditions at high southern latitudes which were recently demonstrated to have a significant presence of echoes of likely FBI origin [ Makarevich et al , ; Forsythe and Makarevich , ].…”