Excitation of poloidal standing Alfvén waves through drift resonance wave‐particle interaction

Dai, Lei; Takahashi, Kazue; Wygant, J. R.; Chen, Liu; Bonnell, J. W.; Cattell, C. A.; Thaller, S. A.; Kletzing, C. A.; Smith, Charles W.; MacDowall, R. J.; Baker, D. N.; Blake, J. B.; Fennell, J. F.; Claudepierre, S. G.; Funsten, H. O.; Reeves, G. D.; Spence, Harlan E.

doi:10.1002/grl.50800

Cited by 146 publications

(218 citation statements)

References 48 publications

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“…In this subsection, we demonstrate the validity of our approach by comparing our analysis result with a recent direct spacecraft observation of poloidal standing Alfvén waves by Dai et al (2013). Since these observations occurred near tosphere, we present the analysis results of the dipole and the compressed-dipole field, which offer different background field geometries.…”

Section: A Real-case Study Of Poloidal Standing Alfvén Modementioning

confidence: 77%

“…The eigenfrequencies and the corresponding wave-form solutions are presented. Section 3 extends the analysis to the decoupled eigenvalue solutions of the poloidal-mode waves for a given geometry and presents a quantitative comparison of the standing transverse Alfvén wave solutions with the observations of Dai et al (2013). Finally, we summarize our results in the last section.…”

Section: Introductionmentioning

confidence: 90%

“…Since these observations occurred near tosphere, we present the analysis results of the dipole and the compressed-dipole field, which offer different background field geometries. Figure 11 shows our results of suitable physical units for L = 5 with the same set of parameters as Dai et al (2013), ρ e = 6.4 amu cm −3 and the power index 1.0 of the density variation, to facilitate a direct comparison with their results (Fig. 3 therein).…”

Section: A Real-case Study Of Poloidal Standing Alfvén Modementioning

confidence: 99%

“…Sometimes they exhibit regular and monochromatic magnetic and electric field wave forms which are due to the standing wave mode along magnetic field lines. Such waves can be identified as Alfvén waves propagating in the Earth's magnetosphere, e.g., the recent spacecraft observation by the Van Allen Probes (Radiation Belt Storm Probes) of Dai et al (2013). Based on the direction or the polarization of the magnetic (or electric) field perturbation in the linearized assumption, they can be further characterized as toroidal and/or poloidal-mode waves.…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, motivated by a recent direct observation of poloidal standing Alfvén waves in Earth's magnetosphere by Dai et al (2013) (see also Dai et al, 2015;Takahashi et al, 2013;Liu et al, 2013Liu et al, , 2011, we extend our investigation to examine the poloidal-mode waves as well. In the case of a transverse poloidal mode, we show that the wave equation can also be cast as a KG form along a field line.…”

Section: Introductionmentioning

confidence: 99%

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Hydromagnetic waves in a compressed-dipole field via field-aligned Klein–Gordon equations

Zheng¹,

Hu²,

Webb³

et al. 2016

Ann. Geophys.

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Abstract. Hydromagnetic waves, especially those of frequencies in the range of a few millihertz to a few hertz observed in the Earth's magnetosphere, are categorized as ultra low-frequency (ULF) waves or pulsations. They have been extensively studied due to their importance in the interaction with radiation belt particles and in probing the structures of the magnetosphere. We developed an approach to examining the toroidal standing Aflvén waves in a background magnetic field by recasting the wave equation into a Klein-Gordon (KG) form along individual field lines. The eigenvalue solutions to the system are characteristic of a propagation type when the corresponding eigenfrequency is greater than a critical frequency and a decaying type otherwise. We apply the approach to a compressed-dipole magnetic field model of the inner magnetosphere and obtain the spatial profiles of relevant parameters and the spatial wave forms of harmonic oscillations. We further extend the approach to poloidalmode standing Alfvén waves along field lines. In particular, we present a quantitative comparison with a recent spacecraft observation of a poloidal standing Alfvén wave in the Earth's magnetosphere. Our analysis based on the KG equation yields consistent results which agree with the spacecraft measurements of the wave period and the amplitude ratio between the magnetic field and electric field perturbations.

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Section: A Real-case Study Of Poloidal Standing Alfvén Modementioning

confidence: 77%

Section: Introductionmentioning

confidence: 90%

Section: A Real-case Study Of Poloidal Standing Alfvén Modementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Hydromagnetic waves in a compressed-dipole field via field-aligned Klein–Gordon equations

Zheng¹,

Hu²,

Webb³

et al. 2016

Ann. Geophys.

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show abstract

Interactions of energetic electrons with ULF waves triggered by interplanetary shock: Van Allen Probes observations in the magnetotail

et al. 2014

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We present in situ observations of a shock-induced substorm-like event on 13 April 2013 observed by the newly launched Van Allen twin probes. Substorm-like electron injections with energy of 30-500 keV were observed in the region from L ∼5.2 to 5.5 immediately after the shock arrival (followed by energetic electron drift echoes). Meanwhile, the electron flux was clearly and strongly varying on the ULF wave time scale. It is found that both toroidal and poloidal mode ULF waves with a period of 150 s emerged following the magnetotail magnetic field reconfiguration after the interplanetary (IP) shock passage. The poloidal mode is more intense than the toroidal mode. The 90• phase shift between the poloidal mode B r and E a suggests the standing poloidal waves in the Northern Hemisphere. Furthermore, the energetic electron flux modulations indicate that the azimuthal wave number is ∼14. Direct evidence of drift resonance between the injected electrons and the excited poloidal ULF wave has been obtained. The resonant energy is estimated to be between 150 keV and 230 keV. Two possible scenaria on ULF wave triggering are discussed: vortex-like flow structure-driven field line resonance and ULF wave growth through drift resonance. It is found that the IP shock may trigger intense ULF wave and energetic electron behavior at L ∼3 to 6 on the nightside, while the time profile of the wave is different from dayside cases.

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THEMIS measurements of quasi‐static electric fields in the inner magnetosphere

Califf

Blum

et al. 2014

JGR Space Physics

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We use 4 years of Time History of Events and Macroscale Interactions during Substorms (THEMIS)double-probe measurements to offer, for the first time, a complete picture of the dawn-dusk electric field covering all local times and radial distances in the inner magnetosphere based on in situ equatorial observations. This study is motivated by the results from the CRRES mission, which revealed a local maximum in the electric field developing near Earth during storm times, rather than the expected enhancement at higher L shells that is shielded near Earth as suggested by the Volland-Stern model. The CRRES observations were limited to the duskside, while THEMIS provides complete local time coverage. We show strong agreement with the CRRES results on the duskside, with a local maximum near L = 4 for moderate levels of geomagnetic activity and evidence of strong electric fields inside L = 3 during the most active times. The extensive data set from THEMIS also confirms the day/night asymmetry on the duskside, where the enhancement is closest to Earth in the dusk-midnight sector, and is farther away closer to noon. A similar, but smaller in magnitude, local maximum is observed on the dawnside near L = 4. The noon sector shows the smallest average electric fields, and for more active times, the enhancement develops near L = 7 rather than L = 4. We also investigate the impact of the uncertain boom-shorting factor on the results and show that while the absolute magnitude of the electric field may be underestimated, the trends with geomagnetic activity remain intact.

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Excitation of poloidal standing Alfvén waves through drift resonance wave‐particle interaction

Cited by 146 publications

References 48 publications

Hydromagnetic waves in a compressed-dipole field via field-aligned Klein–Gordon equations

Hydromagnetic waves in a compressed-dipole field via field-aligned Klein–Gordon equations

Interactions of energetic electrons with ULF waves triggered by interplanetary shock: Van Allen Probes observations in the magnetotail

THEMIS measurements of quasi‐static electric fields in the inner magnetosphere

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