Coherent multiple Pc1 pulsation bands: possible evidence for the ionospheric Alfvén resonator

Feygin, F. Z.; Nekrasov, A. K.; Mursula, K.; Kangas, J.; Pikkarainen, T.

doi:10.1007/s005850050044

Cited by 5 publications

(5 citation statements)

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“…On the other hand, for a narrowband emission there might be the possibility of its substantial attenuation if its frequency does not match these transparency windows. Indeed, Feygin et al [] identified a subclass of early‐morning coherent multiband Pc1 events, which could not be produced by heavy ion stopbands but rather were IAR‐associated ionospheric transmission features. Prikner et al [] observed and interpreted structured Pc1 bands as signatures of transmission bands at the second, third, and fourth IAR harmonics.…”

Section: Discussionmentioning

confidence: 99%

Interaction of magnetospheric Alfvén waves with the ionosphere in the Pc1 frequency band

et al. 2016

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A characteristic feature of the upper ionosphere is the occurrence of the ionospheric Alfvén resonator (IAR) and MHD waveguide, which can trap electromagnetic wave energy in the range from fractions of a Hz to a few Hz. This wave trapping ensures the strong dependence of the ionospheric transmission/reflective properties on frequency. We have developed a numerical model of the magnetospheric Alfvén wave interaction with the ionosphere and transmission to the ground based on the solution of multifluid magnetohydrodynamic (MHD) full wave equations in a realistic ionosphere, whose parameters were reconstructed from the International Reference Ionosphere model. The MHD modes are coupled owing to the frequency‐dependent Hall conductivity and geomagnetic field line inclination. This model can be applied to the interpretation of the spectral structure of electromagnetic emissions of the magnetospheric origin in the band 0.1–10 Hz observed at various latitudes. The model predicts that the upper part of the ULF spectrum (f > 1 Hz) will be severely absorbed upon wave transmission through the daytime ionosphere to the ground. At nighttime the transmission coefficient of Alfvén waves has an oscillatory dependence on frequency, with “transmission windows” at the lowest IAR eigenfrequencies (<3 Hz). At higher frequencies (3–10 Hz) the reflection/transmission coefficients are dominated by periodic scale‐dependent modulation owing to the waveguide modes. Broad maxima/minima of the transmission coefficient are determined by the phasing between Alfvén and fast magnetosonic waves at the bottom of the ionosphere.

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Section: Discussionmentioning

confidence: 99%

Interaction of magnetospheric Alfvén waves with the ionosphere in the Pc1 frequency band

et al. 2016

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“…Geophys. Geod., 54 (2010) Coherent multiple Pc1 pulsation bands, recorded at Finnish stations, were studied by Feygin et al (1994). The conclusions suggested that the central frequencies of the simultaneous Pc1 bands agree with the IAR resonance properties.…”

Section: Introductionmentioning

confidence: 90%

A comparative Pc1 case study applying two modes of ionospheric Alfvén resonator modeling

2010

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The case study of four Pc1 subauroral pulsation events from Finland has been carried out on the basis of the full-wave numerical method. This method has been applied to simultaneous Scandinavian EISCAT radar measurements of the ionospheric plasma parameters, and their vertical (altitude) profiles have been utilized. Two alternative plasma profiles with different ion composition displays have been put to the test. A comparison between both types of the modeled ionospheric Alfvén resonator (IAR) ground signal frequency response and the frequency range of the Pc1 signal records has been studied. The results of the applied method can illustrate possible quiescent or disturbance changes in the upper ionosphere above the dense F2 layer. The ionospheric region up to ~ 2000 km has been taken into account for this comparative analysis.

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“…Frequency‐dependent transmission through the ionosphere was suggested to control the Pc1 frequency band observed on the ground (Fraser‐Smith, ). Indeed, the central frequency of Pc1 emissions was found to correspond to the maximum of the transmission coefficient, coinciding with the frequency of IAR harmonics (Feygin et al, ; Mursula et al, ; Prikner et al, , ). Thus, the ionosphere with the IAR and IFW can act as a multiband band‐pass filter for EMIC waves, forming the spectral structure of Pc1 emissions observed on the ground.…”

Section: Introduction: Pc1 Waves and Transmission/reflective Propertimentioning

confidence: 94%

Transmission of a Magnetospheric Pc1 Wave Beam Through the Ionosphere to the Ground

et al. 2018

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A characteristic feature of the upper ionosphere is the occurrence of the ionospheric Alfvén resonator (IAR) and the ionospheric fast-mode waveguide (IFW), which can trap electromagnetic wave energy in the Pc1 frequency range from fractions of a hertz to a few hertz. This wave trapping ensures the dependence of ionospheric transmission/reflective properties on frequency. We numerically model magnetospheric Alfvén wave transmission through the ionosphere to the ground based on solution of the magnetohydrodynamic full-wave equations in a realistic ionosphere, whose parameters are reconstructed from the International Reference Ionosphere model. The spatial structure of an incident wave is modeled as a localized beam with a finite latitudinal scale ⟂ and an azimuthally propagating wave. The IAR and IFW modes are coupled owing to the Hall conductivity and geomagnetic field inclination. Ground spatial and spectral structures of the Pc1 wave (0.1-to 6-Hz band) have been calculated for summer day/night conditions at the Antarctic Halley observatory, though results may be qualitatively applied to any midlatitude site. An incident wave with azimuthal wave vector k y = 1.7 ⋅ 10 −3 km −1 , and ⟂ = 10 2 km has been considered. The model predicts that beneath the incident beam the ground magnetic response "duplicates" its structure after accounting for a ∕2 rotation and some latitudinal shift/widening. The transmission has an oscillatory dependence on frequency, thus forming "transmission windows" at resonant frequencies of IAR and IFW modes. The spectra vary depending on distance from an incidence point. Interference between IFW modes is revealed in the nonmonotonic and frequency-dependent character of latitudinal variations of wave amplitude.

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Coherent multiple Pc1 pulsation bands: possible evidence for the ionospheric Alfvén resonator

Cited by 5 publications

References 0 publications

Interaction of magnetospheric Alfvén waves with the ionosphere in the Pc1 frequency band

Interaction of magnetospheric Alfvén waves with the ionosphere in the Pc1 frequency band

A comparative Pc1 case study applying two modes of ionospheric Alfvén resonator modeling

Transmission of a Magnetospheric Pc1 Wave Beam Through the Ionosphere to the Ground

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