Wave-particle interaction in the auroral ionosphere in LF and HF range: Results from antarctic rocket observations.

Abstract

Plasma wave observations using the sounding rockets, S-310JA-11 and S-310JA-12 have disclosed the following new aspects of wave-particle interaction processes in the auroral ionosphere:1) generation of intense Z-mode waves by auroral particles through the inverse Landau damping, 2) confirmation of the leaked components of auroral kilometric radiation, and 3) detection of naturally generated electrostatic electron cyclotron harmonic (ESCH) waves in the frequency range lower than the local electron cyclotron frequency.It is pointed out that Z-mode waves in the auroral region have a very important role because the waves are easily generated being coupled with the particle precipitation. The leaked component of AKR is an important manifestation of the mode conversion processes. The generation of ESCH waves are associated with the nonlinear wave-particle interaction. The newly detected ESCH wave phenomena correspond to n=0 case of the fDn emissions. IntroductionExperiments using auroral sounding rockets were carried out at Syowa Station, Antarctica, in 1985, as a campaign for the international Middle Atmosphere Program (MAP). The main objective of the experiments is to study wave-particle interaction processes in auroras; the scope of the program has been described in this special issue . The experiments for plasma waves in the HF range is one of the essential observations for the study on (1) generation and propagation mechanism of the plasma waves through the resonant interaction processes with the auroral particles and (2) the role of the generated plasma waves in the acceleration and deceleration processes of the auroral particles.On two sounding rockets, S-310JA-11 and S-310JA-12 plasma wave probes (PWH) were installed being designed to observe plasma waves in auroras in the LF and HF ranges. In this paper, we report the preliminary results of these rocket 923 924 A. MORIOKA et al.observations for plasma waves. The PWH instrument consists of an electric dipole antenna with 2.4 m (tip to tip) length and a superheterodyne receiver; the receiving frequency is swept stepwise in a range from 50 kHz to 11.5 MHz. To sweep the full receiving range of the receiver, the full band is divided into two sub-bands; i.e., from 50 kHz to 1.4 MHz for a low frequency band and from 1.4 MHz to 11.5 MHz for a high frequency band. The frequency resolution of the receiver is 10 kHz in the low band and 80 kHz in the high band. The total frequency range from the low band to the high band is scanned in 1.28 seconds. The gain of the receiver is changed automatically between high-gain and low-gain to get a wide dynamic range; the switching of the gain was made being synchronized with the timing of each frequency scanning.The observations by both rockets S-310JA-11 and S-310JA-12 were carried out successfully, and provided much information on wave particle interactions that are taking place in and above the auroral formation regions. Observation of Plasma Wave Phenomena by Two Experiments S-310JA-11 rocket observationThe S-310JA-11 rocket wa...

Sub-ionospheric AKR: A possible mechanism for its transport down from the topside generation region to the F layer and ground

“…For example, recent ground-based observations in Antarctica show occurrence of AKR-like signals simultaneous with similar AKR detected in space with the Geotail spacecraft (LaBelle et al, , 2015. These observations confirmed earlier claims that AKR might be observable at low-altitude spacecraft, rockets and possibly even from ground-based instrumentation (Oya et al, 1985;Morioka et al, 1988;Beghin et al, 1989;Yoon and Ziebell, 1995;Shutte et al, 1997;La-Belle et al, 1999;Parrot and Berthelier, 2012;Simoes et al, 2012). Such observations are difficult to explain by conventional mechanisms because the highly ionised dense upper ionosphere poses a seemingly unsurpassable barrier for the transport of X-, O-, or Z-mode radiation at AKR frequencies of a few 100 kHz down to the atmosphere.…”

Ground-level detection of auroral kilometric radiation

“…Hence its discovery, which came twenty years after the discovery of Jovian decametric radiation, relied on suitably instrumented spacecraft a large distance (>5000 km) from Earth. Nevertheless, over the years there have been occasional reports of AKR‐like emissions observed at low altitudes from rocket‐borne, low‐earth‐orbiting satellite borne, and ground based receivers [e.g., Oya et al , 1985; Morioka et al , 1988; Beghin et al , 1989; Shutte et al , 1997; LaBelle et al , 1999]. In particular, Oya et al [1985] championed the idea of “leaked AKR” as an explanation for AKR‐like signals observed with the low‐Earth‐orbiting EXOS‐C satellite.…”

Studies on Plasma and Plasma Waves in the Plasmasphere and Auroral Particle Acceleration Region, by PWS on board the EXOS-D (Akebono) Satellite

“…Generation processes of the upper hybrid waves are related to two complementary features of free energy; i.e., one is the case of the plasma velocity DUSENBERY and LYONS, 1985;OMIDI and Wu, 1985;MENIETTI, 1985;BAHNSEN et al, 1987;HASHIMOTO et al, 1987;HORNE, 1988;MORIOKA et al, 1988;EHORNE, 1989;HASHIMOTO and CALVERT, 1990).…”