Statistical study of Pc1-2 wave propagation characteristics in the high-latitude ionospheric waveguide

Kim, H.; Lessard, M.; Engebretson, M. J.; Young, Matthew A.

doi:10.1029/2010ja016355

Cited by 47 publications

(60 citation statements)

References 63 publications

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“…Engebretson et al, 2008); and ground-based observations (e.g. Kawamura et al, 1983;Mursula et al, 2001;Kim et al, 2011). The electromagnetic ion cyclotron (EMIC) instability at high altitudes is generally considered as the source of Pc1 pulsations.…”

Section: Introductionmentioning

confidence: 99%

Global characteristics of Pc1 magnetic pulsations during solar cycle 23 deduced from CHAMP data

2013

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We present a global climatology of Pc1 pulsations as observed by the CHAMP satellite from 2000 to 2010. The Pc1 center frequency and bandwidth are about 1 and 0.5 Hz, respectively. The ellipticity is mostly linear with the major axis almost aligned with the magnetic zonal direction. The diurnal variation of Pc1 occurrences shows a primary maximum early in the morning and a secondary maximum during pre-midnight hours. The annual variations of the occurrence rates exhibit a clear preference for local summer. The solar cycle dependence of the occurrence rate reveals a maximum at the declining phase (2004–2005). Neither magnetic activity nor solar wind velocity controls the Pc1 occurrence rate significantly. Pc1 occurrence rate peaks at subauroral latitudes, but the steep cutoff towards higher latitudes is due to auroral field-aligned currents masking the Pc1 pulsations. The center frequency of Pc1 pulsations does not show a clear dependence on latitude. The global distribution of Pc1 exhibits highest occurrence rates near the longitude sector of the South Atlantic Anomaly. Pc1 events at auroral latitudes, although they are rarely detected, show a clear occurrence peak around local noon. A majority of the auroral Pc1 events are observed during solar minimum years

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Section: Introductionmentioning

confidence: 99%

Global characteristics of Pc1 magnetic pulsations during solar cycle 23 deduced from CHAMP data

2013

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“…Neudegg et al (1995) have shown from an array of ground magnetometers that Pc1 signals propagate with a typical speed of 450 km/s over distances of a few hundred kilometers, consistent with propagation in this ionospheric waveguide. Yahnina et al (2000) found that Pc1 oscillations can be seen a few hours of magnetic local time away from their source while Kim et al (2011) showed examples of Pc1 events seen up to 3000 km from their source. These observations indicate that these waves can propagate over large distances through the ionosphere.…”

Section: Simplified Model For the Fast Alfvén Mode In The Iarmentioning

confidence: 99%

On the coupling of fast and shear Alfvén wave modes by the ionospheric Hall conductance

2013

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There are two low frequency, magnetised, cold plasma wave modes that propagate through the Earth's magnetosphere. These are the compressional (fast) and the shear Alfvén modes. The fast mode distributes energy throughout the magnetosphere with the ability to propagate across the magnetic field. Previous studies of coupling between these two modes have often focussed on conditions necessary for mode coupling to occur in the magnetosphere. However, Kato and Tamao (1956) predicted mode coupling would occur for non-zero Hall currents. Recently, the importance of the Hall conductance in the ionosphere for low frequency wave propagation has been studied using one dimensional (1-D) models. In this paper we describe effects of the ionosphere Hall conductance on field line resonance and higher frequency, 0.1-5 Hz waves associated with the Ionospheric Alfvén Resonator (IAR). The Hall conductance reduces the damping time of field line resonances and Joule dissipation into the ionosphere. The Hall conductance also couples shear Alfvén waves trapped in the IAR to fast mode waves that propagate across the ambient magnetic field in an ionospheric waveguide. This coupling leads to the production of low frequency magnetic fields on the ground that can be observed by magnetometers.

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“…Once generated, these waves propagate generally along magnetic field lines, reaching the ionosphere(s) and coupling wave power to a signal that can be observed on the ground. Within the ionosphere, horizontal structuring in the F region results in the development of a horizontal ducting region, where the EMIC wave is partially converted to a fast mode wave that can be carried thousands of kilometers in a matter of seconds [ Kim et al , , ; Fraser , ; Greifinger and Greifinger , ]. The net result is that a ducted signal can be observed across a range of magnetic latitudes and longitudes, relative to the locations of the injection of the wave into the ionosphere; Posch et al [] quantified this effect with regard to Pi1B pulsations (which have comparable frequencies to the waves studied here) and found that they are localized to approximately 4 h of local time and 7 ∘ in magnetic latitude.…”

Section: Introductionmentioning

confidence: 99%

Solar cycle dependence of ion cyclotron wave frequencies

et al. 2015

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Electromagnetic ion cyclotron (EMIC) waves have been studied for decades, though remain a fundamentally important topic in heliospheric physics. The connection of EMIC waves to the scattering of energetic particles from Earth's radiation belts is one of many topics that motivate the need for a deeper understanding of characteristics and occurrence distributions of the waves. In this study, we show that EMIC wave frequencies, as observed at Halley Station in Antarctica from 2008 through 2012, increase by approximately 60% from a minimum in 2009 to the end of 2012. Assuming that these waves are excited in the vicinity of the plasmapause, the change in Kp in going from solar minimum to near solar maximum would drive increased plasmapause erosion, potentially shifting the generation region of the EMIC to lower L and resulting in the higher frequencies. A numerical estimate of the change in plasmapause location, however, implies that it is not enough to account for the shift in EMIC frequencies that are observed at Halley Station. Another possible explanation for the frequency shift, however, is that the relative density of heavier ions in the magnetosphere (that would be associated with increased solar activity) could account for the change in frequencies. In terms of effects on radiation belt dynamics, the shift to higher frequencies tends to mean that these waves will interact with less energetic electrons, although the details involved in this process are complex and depend on the specific plasma and gyrofrequencies of all populations, including electrons. In addition, the change in location of the generation region to lower L shells means that the waves will have access to higher number fluxes of resonant electrons. Finally, we show that a sunlit ionosphere can inhibit ground observations of EMIC waves with frequencies higher than ∼0.5 Hz and note that the effect likely has resulted in an underestimate of the solar-cycle-driven frequency changes described here.

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Statistical study of Pc1-2 wave propagation characteristics in the high-latitude ionospheric waveguide

Cited by 47 publications

References 63 publications

Global characteristics of Pc1 magnetic pulsations during solar cycle 23 deduced from CHAMP data

Global characteristics of Pc1 magnetic pulsations during solar cycle 23 deduced from CHAMP data

On the coupling of fast and shear Alfvén wave modes by the ionospheric Hall conductance

Solar cycle dependence of ion cyclotron wave frequencies

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