Simultaneous observations of subauroral electron temperature enhancements and electromagnetic ion cyclotron waves

Abstract

Observational results from an investigation of low frequency (0.5–4.0 Hz) electromagnetic ion cyclotron waves and subauroral electron temperature enhancements recorded from the DE‐2 satellite are presented. Four different wave events were analyzed, all recorded at magnetic latitudes from 57–60°, magnetic local times from 8–14 hours, and altitudes from 600–900 km. The peak wave amplitudes during the events ranged from 8–70 nT and 5–30 mV/m in the magnetic and electric field, respectively. Electron temperature (Te) enhancements at the time of the waves were observed in 3 of 4 events. A linear relationship between the wave magnetic field spectral density and Te enhancements was found for these events. The Te enhancements were also correlated with an enhanced flux of low energy electrons. During one event (82104) an enhanced flux of electrons were observed at energies up to 50eV and at nearly all pitch angles, although the flux was largest in the precipitating and upflowing directions. It is suggested that the waves are responsible for heating the low energy electrons which precipitate to the ionosphere and produce the observed Te enhancements. The upflowing electron population appears to be heated at ionospheric altitudes, below the DE‐2 satellite. The precipitating electrons may also be heated at ionospheric altitudes through Landau damping, although the observations do not rule out electron heating near the equator.

Electromagnetic wave structures within subauroral polarization streams

“…It is worth noting that Iyemori and Hayashi [1989] and Erlandson et al [1993] observed down‐going electromagnetic waves with ∼0.1–1 Hz frequencies (Pc1 range) at L ≥ 4 in the dusk and morning sectors. Erlandson et al [1993] suggested that those are electromagnetic ion cyclotron (EMIC) waves generated by RC protons in the RC‐plasmasphere overlap region. Could this mechanism contribute to formation of the down‐going Poynting flux and energetic ion precipitations in the dusk‐evening sector (Figure 6)?…”

Cold electron heating by EMIC waves in the plasmaspheric plume with observations of the Cluster satellite

“…There are three leading mechanisms: Coulomb collisions of plasmaspheric electrons with RC ions producing a heated plasmaspheric electron population [Cole, 1965[Cole, , 1975Kozyra et al, 1987;Fok et al, 1993]; heating the plasmaspheric electrons through resonant Landau damping of electromagnetic ion cyclotron (EMIC) waves generated by RC ions [Cornwall et al, 1971; Thorne and Horne, 1992;Zhou et al, 2013]; and kinetic Alfvén waves directly accelerating plasmaspheric electrons into the ionosphere through the parallel electric field associated with the waves [Hasagawa and Mima, 1978]. Evidences of ion cyclotron, kinetic Alfvén waves in association with events of ionospheric electron heating elsewhere have been reported [Lundblad and Søraas, 1978;Erlandson et al, 1993;Lanzerotti et al, 1978;Mishin and Burke, 2005]. Although the energy source of plasmaspheric electron heating is assumed to be in the magnetosphere [Kozyra et al, 1997], to our knowledge few in situ evidence of plasmaspheric electron heating in the plasmaspheric plume has been reported.…”

Overlap of the plasmasphere and ring current: Relation to subauroral ionospheric heating

“…Using measured ring current and plasmasphere particle distributions in conjunction with a hydromagnetic model, both Gorbachev et al [1992] and Khazanov et al [1994] have derived ionospheric electron and ion temperature profiles expected from the generation of equatorial ion cyclotron waves which match well with measured profiles. Evidence of ion cyclotron waves in association with ionospheric heating events have been reported by Lundblad and Søraas [1978] and Erlandson et al [1993]. Both Jordanova et al [2001] and Khazanov et al [2003] have included the generation of ion cyclotron waves in two‐dimensional ring current models.…”