A numerical model to investigate the polarisation azimuth of ULF waves through an ionosphere with oblique magnetic fields

Sciffer, M. D.; Waters, C. L.; Menk, F. W.

doi:10.5194/angeo-23-3457-2005

Cited by 35 publications

(68 citation statements)

References 21 publications

(47 reference statements)

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“…After this initial period, the problem has also been studied for more general geometries of the background magnetic field (see, e.g., Leonovich and Mazur, 1991;Alperovich and Fedorov, 1993;Sciffer and Waters, 2002;Sciffer et al, 2004Sciffer et al, , 2005. Below we present a model and numerical results for the problem of magnetohydrodynamic wave transmission through and reflection from the ionosphere within a more realistic "thick ionosphere" model (Knudsen et al, 1992).…”

Section: Model Calculationsmentioning

confidence: 99%

Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations

Yagova

Heilig²,

Fedorov

2015

Ann. Geophys.

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Abstract. We analyze Pc2-3 pulsations recorded by the CHAMP (CHAllenging Minisatellite Payload) satellite in the F layer of the Earth's ionosphere, on the ground, and in the magnetosphere during quiet geomagnetic conditions. The spectra of Pc2-3 pulsations recorded in the F layer are enriched with frequencies above 50 mHz in comparison to the ground Pc2-3 spectra. These frequencies are higher than the fundamental harmonics of the field line resonances in the magnetosphere. High quality signals with dominant frequencies 70-200 mHz are a regular phenomenon in the F layer and in the magnetosphere. The mean latitude of the maximum Pc2-3 occurrence rate lies at L ≈ 3.5 in the F layer, i.e., inside the plasmasphere. Day-to-day variations of the L value of the CHAMP Pc2-3 occurrence rate maximum follow the plasmapause day-to-day variations. Polarization and amplitude of Pc2-3s in the magnetosphere, in the ionosphere, and on the ground allow us to suggest that they are generated as fast magnetosonic (FMS) waves in the outer magnetosphere and are partly converted into shear Alfven waves near the plasmapause. The observed ground-to-ionosphere amplitude ratio during the night is interpreted as a result of the Alfven wave transmission through the ionosphere. The problem of wave transmission through the ionosphere is solved theoretically by means of a numerical solution of the full-wave equation for the Alfven wave reflection from and transmission through a horizontally stratified ionosphere. The best agreement between the calculated and measured values of the ground-to-ionosphere amplitude ratio is found for k = 5 × 10 −3 km −1 , i.e., the observed ground-to-ionosphere amplitude ratio corresponds to a wave spatial scale which could provide a Doppler shift within a few percent of the apparent frequency of the Pc2-3 pulsations as recorded by a loworbiting spacecraft.

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Section: Model Calculationsmentioning

confidence: 99%

Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations

Yagova

Heilig²,

Fedorov

2015

Ann. Geophys.

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“…Since the ULF wave energy must pass through the ionosphere to reach ground based sensors, a number of studies have examined the propagation of ULF waves from the magnetosphere through the ionosphere to the ground (Hughes, 1974;Ellis and Southwood., 1983;Waters et al, 2001;Ponomarenko et al, 2001;Sciffer et al, 2005). Analytic models treat the ionosphere as a thin current sheet whose properties can be characterised by height integrated Pedersen and Hall conductivities (Hughes, 1974;Sciffer and Waters, 2002).…”

Section: Ulf Waves and The Ionospherementioning

confidence: 99%

“…A boundary value formulation that allows for oblique B 0 and both MHD wave modes was developed by (Sciffer et al, 2005). ULF wave energy, incident from the magnetosphere is described as an electromagnetic disturbance.…”

Section: Ulf Waves and The Ionospherementioning

confidence: 99%

Modulation of radio frequency signals by ULF waves

et al. 2007

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Abstract. The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1-100 mHz) plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that the magnitude of the ULF wave electric field, e, and the geomagnetic field, B 0 , giving an e×B 0 drift, is the dominant mechanism for changing the radio frequency. We also show how data from high frequency (HF) Doppler sounders can be combined with HF radar data to provide details of the spatial structure of ULF wave energy in the ionosphere. Due to spatial averaging effects, the spatial structure of ULF waves measured in the ionosphere may be quite different to that obtained using ground based magnetometer arrays. The ULF wave spatial structure is shown to be a critical parameter that determines how ULF wave effects alter the frequency of HF signals propagating through the ionosphere.

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“…: Poloidal Alfvén wave adjacent to plasmapause waves observed at the ground are modified by the ionosphere (Hughes, 1974;Hughes and Southwood, 1976;Glassmeier, 1984) and consequently, modelling of the ionospheric screening effect is necessary for an accurate understanding of the ground based observations (e.g. Sciffer et al, 2004Sciffer et al, , 2005Glassmeier, 1988).…”

Section: Introductionmentioning

confidence: 99%

Spatio-temporal structure of a poloidal Alfvén wave detected by Cluster adjacent to the dayside plasmapause

et al. 2008

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Abstract.A case study of a poloidal ULF pulsation near the dayside plasmapause is presented based on Cluster observations of magnetic and electric fields. The pulsation is detected close to the magnetic equatorial plane at L shells L=[4.4, 4.6] and oscillates with a frequency of f =23 mHz. Investigating the wave energy flux reveals the standing wave nature of the observed pulsation. An estimation of the azimuthal wave number exposes a narrow azimuthal structure of the wave field with m≈160. Spatial and temporal characteristics of the pulsation are analyzed in detail by representing data in a field line related coordinate system and a rangetime-intensity representation. This allows an estimation of both the spatial extension of the wave field in the radial direction and its temporal decay rate. The analysis furthermore indicates that the same field lines are excited to a standing wave oscillation twice. Furthermore an accurate identification of a phase jump of the wave field across L shells is possible. Comparing the radial localization of the detected wave with theoretically expected field line eigenfrequencies reveals that the wave field is confined in the Alfvén resonator at the outer edge of the plasmapause.

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A numerical model to investigate the polarisation azimuth of ULF waves through an ionosphere with oblique magnetic fields

Cited by 35 publications

References 21 publications

Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations

Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations

Modulation of radio frequency signals by ULF waves

Spatio-temporal structure of a poloidal Alfvén wave detected by Cluster adjacent to the dayside plasmapause

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