Impulse-excited hydromagnetic cavity and field-line resonances in the magnetosphere

Allan, W.; White, Sarahlouise; Poulter, E. M.

doi:10.1016/0032-0633(86)90144-3

Cited by 251 publications

(190 citation statements)

References 31 publications

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“…The theory has been well established in 1D by Southwood (1974) who showed that a resonant singularity existed on the field line where the Alfvén frequency (ω A ) is equal to the fast mode frequency (see also Chen & Hasegawa (1974)) motivated by observations of the Earth's magnetosphere. There have also been simulations showing how 1D resonant solutions can grow with time (Allan et al (1986), Mann et al (1995)). Such wave coupling is a basic plasma process and also occurs in the solar context where 1D models have been used to explain the heating of coronal flux tubes (e.g., Goossens et al (1995), Soler & Terradas (2015), Arregui & Ballester (2011), and references therein).…”

Section: Introductionmentioning

confidence: 99%

The Theoretical Foundation of 3d Alfvén Resonances: Normal Modes

Wright

Elsden

2016

ApJ

134

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We consider the resonant coupling of fast and Alfvén magnetohydrodynamic (MHD) waves in a 3D equilibrium. Numerical solutions to normal modes (∝ exp(−iωt)) are presented along with a theoretical framework to interpret them. The solutions we find are fundamentally different to those in 1D and 2D. In 3D there exists an infinite number of possible resonant solutions within a "Resonant Zone," and we show how boundary conditions and locally 2D regions can favour particular solutions. A unique feature of the resonance in 3D is switching between different permissible solutions when the boundary of the Resonant Zone is encountered. The theoretical foundation we develop relies upon recognising that in 3D the orientation of the resonant surface will not align in a simple fashion with an equilibrium coordinate. We present a method for generating the Alfvén wave natural frequencies for an arbitrarily oriented Alfvén wave, which requires a careful treatment of scale factors describing the background magnetic field geometry.

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Section: Introductionmentioning

confidence: 99%

The Theoretical Foundation of 3d Alfvén Resonances: Normal Modes

Wright

Elsden

2016

ApJ

134

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“…Allan et al, 1986;Samson et al, 1992;Mann et al, 1999) or Kelvin-Helmholtz instability surface waves on the flanks of the magnetopause (e.g. Southwood, 1974;Fujita et al, 1996;Engebretson et al, 1998;Rae et al, 2005) have been proposed, the spatial amplitude and phase structures of ground based magnetic field measurements during FLR events are commonly accepted due to abundant experimental evidence (e.g.…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis of ground based magnetic field measurements with the field line resonance detector

et al. 2008

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Abstract. In this paper we introduce the field line resonance detector (FLRD), a wave telescope technique which has been specially adapted to estimate the spectral energy density of field line resonance (FLR) phase structures in a superposed wave field. The field line resonance detector is able to detect and correctly characterize several superposed FLR structures of a wave field and therefore constitutes a new and powerful tool in ULF pulsation studies. In our work we derive the technique from the classical wave telescope beamformer and present a statistical analysis of one year of ground based magnetometer data from the Canadian magnetometer network CANOPUS, now known as CARISMA. The statistical analysis shows that the FLRD is capable of detecting and characterizing superposed or hidden FLR structures in most of the detected ULF pulsation events; the one year statistical database is therefore extraordinarily comprehensive. The results of this analysis confirm the results of previous FLR characterizations and furthermore allow a detailed generalized dispersion analysis of FLRs.

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“…It is generally accepted that ULF waves in the Pc 3 (10-100 mHz) band, observed at low and middle latitudes, are a consequence of field line resonance (FLR) stimulated by fast mode oscillations in the plasmasphere and magnetosphere [Kivelson and Southwood, 1986;Allan et al, 1986;Allan and Poulter, 1992]. In this situation the signature observed on the ground is that of the FLR and the frequency increases with decreasing latitude.…”

Section: Introductionmentioning

confidence: 99%

The phase structure of very low latitude ULF waves across dawn

Waters¹,

Sciffer²,

Fraser³

et al. 2001

J. Geophys. Res.

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Abstract. Ultralow frequency (ULF) waves at the geomagnetic equator are studied by using a small magnetometer array and a one-dimensional electromagnetic wave model. Most ULF waves observed at low latitudes have been associated with shear Alfven mode hydromagnetic resonances in the plasmasphere. Near the equator it is difficult to excite these resonances, and the wave activity is attributed to fast mode waves. The phase difference data recorded at longitudinally spaced, equatorial magnetometers shows a marked change around dawn when one station is sunlit while the other is still in darkness. The phase structure with latitude also shows large phase shifts near the equator, in agreement with previous studies. A model of ULF wave propagation through the equatorial ionosphere is presented and used to compare with the observed amplitude and phase properties. It is shown that the observed frequencies are in the vicinity of the wave cutoff frequency where the phase structure becomes complicated. For frequencies above the cutoff, the phase structure across dawn is directly related to dawn-associated changes in electron density in the ionosphere.

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Impulse-excited hydromagnetic cavity and field-line resonances in the magnetosphere

Cited by 251 publications

References 31 publications

The Theoretical Foundation of 3d Alfvén Resonances: Normal Modes

The Theoretical Foundation of 3d Alfvén Resonances: Normal Modes

Statistical analysis of ground based magnetic field measurements with the field line resonance detector

The phase structure of very low latitude ULF waves across dawn

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