ULF Waves in the Magnetosphere

Takahashi, Kazue

doi:10.1002/rog.1991.29.s2.1066

Cited by 17 publications

(4 citation statements)

References 149 publications

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“…The most convincing experimental evidence for the existence of geomagnetic field line resonances in the magnetosphere has been provided by spacecraft data [e.g., Takahashi, 1991 In the present paper we extend both experimental and theoretical aspects of low-latitude field line resonance properties. We compare the resonant frequency and resonance width determined using the meridional amplitude subtraction, amplitude division, and cross-phase methods with the results of a multistation study of the meridional variation in Pc 3 wave polarization parameters by Ziesolleck et al [1993].…”

Section: Introductionsupporting

confidence: 64%

Low latitude geomagnetic field line resonance: Experiment and modeling

Waters¹,

Menk²,

Fraser³

1994

J. Geophys. Res.

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Geomagnetic field line resonances may be identified in ground magnetometer data by comparing the difference in amplitude and phase of signals recorded at two closely spaced sites or by examining the latitudinal variation in polarization properties across a more extended array. These two methods give comparable results for values of the resonant frequency and width at low latitudes (L < 3). We have also found an upper limit for the damping factor, γ∼0.07 at L=1.8, by applying a damped simple harmonic oscillator model. The field line resonance structure observed in 5 weeks of data showed only one resonant frequency at L=1.8 but up to four harmonies concurrently at L=2.8. An early local morning decrease in eigenfrequency was usually present at L=1.8. This is attributed to dynamic heavy ion mass loading effects in the ionosphere where the plasma density increases around dawn. The observed eigenfrequencies were used to evaluate two plasma density models. Calculations using a combined IRI‐90 and diffusive equilibrium (DE) model gave eigenfrequencies which are considerably smaller than the experimentally observed values at both L=1.8 and L=2.8. Furthermore, the calculated harmonic spacings at L=2.8 do not agree with the experimental values, although the diurnal trends were successfully modeled using the IRI‐DE plasma description. The low‐latitude plasma density model described by Bailey (1983) yields eigenfrequencies which show good agreement with the experimentally observed values at both latitudes.

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Section: Introductionsupporting

confidence: 64%

Low latitude geomagnetic field line resonance: Experiment and modeling

Waters¹,

Menk²,

Fraser³

1994

J. Geophys. Res.

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“…And, if so, is frequency sweeping associated with the saturation of these instabilities?" Although most magnetospheric waves which resonate with' energetic particles are externally driven by solar wind variability and plasma flows near the magnetosphere [38], theory and observation have indicated the possibility of drift-bounce resonant excitation of PC 4-5 pulsations by energetic ring-current ions [39]. If low-frequency Alfv6n waves are excited by drift-bounce resonances, they will have a relatively short perpendicular wavelength, and the detection of frequency sweeping will require multiple satellites.…”

Section: Conclusion and Opportunitiesmentioning

confidence: 99%

Laboratory Observations of Wave-Induced Radial Transport within an "Artificial Radiation Belt"

Mauel

1997

J. Phys. IV France

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Wave-induced radial transport of energetic electrons has been observed in a laboratory terrella. In the experiment, electron-cyclotron-resonance heating (ECRH) is used to create a localized population of trapped energetic electrons (1 keV < Eh < 50 keV) within a low-density discharge which we refer to as an "artificial radiation belt." As the,intensity of the radiation belt increases, quasiperiodic bursts of driftresonant fluctuations, w = w d h , are excited. The frequency spectrum of this instability is time-varying and complex, and global chaotic radial transport is induced whenever the frequency spectrum is both intense and compact. High-speed measurements of the energetic electron transport are made with particle detectors, and these measurements can be directly compared with nonlinear and self-consistent simulations. We find quasilinear transport simulations do not reproduce the experimental measurements. In contrast, simulations which retain the electron's guiding-center Hamiltonian dynamics and which preserve the first, p, and second, J, adiabatic invariants reproduce key temporal characteristics of the experimental measurements. The resemblance between simulation and experiment suggests that persistent phase-space structures strongly modulate the energetic electron transport and contribute to the growth and saturation of the instability.

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“…In particular, ULF wave activity in the ∼15 to 100 mHz band is known to be associated with small interplanetary magnetic field (IMF) cone angles with frequency proportional to the IMF magnitude [ Troitskaya et al , 1971; Arthur and McPherron , 1977; Greenstadt and Olson , 1977]. Experimental detection of FLRs is straightforward and FLRs are routinely found from the magnetopause to low latitudes ( L ∼ 1.5), mostly over the dayside magnetosphere [ Samson et al , 1971; Orr , 1973; Baransky et al , 1989; Takahashi , 1991; Waters et al , 1991; Anderson and Engebretson , 1995; Menk et al , 2000]. FLR excitation over most of the magnetosphere is generally thought to arise from coupling with fast mode MHD waves that may propagate across the background magnetic field [ Chen and Hasegawa , 1974a, Southwood , 1974].…”

Section: Introductionmentioning

confidence: 99%

Detection of ultralow‐frequency cavity modes using spacecraft data

et al. 2002

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[1] The cold, magnetized plasma in the Earth's magnetosphere supports two ultralowfrequency plasma wave modes. Both these modes may exhibit resonant oscillations in the magnetosphere cavity. Theoretical and numerical studies have predicted the existence of cavity/waveguide resonance modes, yet experimental evidence is sparse. In this paper we detail the expected structure of these modes using both one dimensional (1-D) and three-dimensional (3-D) magnetohydrodynamic (MHD) numerical models. The cavity/ waveguide mode structures are examined in order to develop experimental detection methods suitable for spacecraft electric and magnetic field perturbation data. Cavity mode resonances in the 1-D model suggest a detection method based on wave polarization using the radial (b x ) and field-aligned (b z ) magnetic perturbations. However, when implemented, this method failed to identify cavity/waveguide modes in the magnetic field data recorded by Active Magnetospheric Particle Tracer Explorers/CCE for events that showed pronounced field line resonances in the azimuthal (b y ) channel. An examination of data from a 3-D MHD numerical simulation showed that the cavity/waveguide resonant signature was identified best in b z component data. Consequently, a wave mode detection method using the b z data from two spatially separated satellites is discussed.

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ULF Waves in the Magnetosphere

Cited by 17 publications

References 149 publications

Low latitude geomagnetic field line resonance: Experiment and modeling

Low latitude geomagnetic field line resonance: Experiment and modeling

Laboratory Observations of Wave-Induced Radial Transport within an "Artificial Radiation Belt"

Detection of ultralow‐frequency cavity modes using spacecraft data

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