A theoretical model for the generation of Kinetic Alfvén waves in the Earth's Magnetosphere by Ion Beam and Velocity Shear

Barik, K. C.; Singh, S. V.; Lakhina, G. S.

doi:10.23919/ursirsb.2019.8956140

Cited by 8 publications

(5 citation statements)

References 33 publications

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“…To understand this puzzling scenario of KAWs in space and astrophysical contexts, several mechanisms have been suggested so far (see reviews in Lakhina 1990Lakhina , 2008Nishizuka et al 2008;Barik et al 2019aBarik et al , 2019bBarik et al , 2019c. Previous studies have primarily focused on the Maxwellian distribution, attributing the fluctuations to gyroradius correction terms.…”

Section: Introductionmentioning

confidence: 99%

Solar Coronal Heating by Kinetic Alfvén Waves

Ayaz,

Li,

Khan

2024

ApJ

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The utilization of the Cairns distribution serves as a vital tool for characterizing the nonthermal attributes commonly observed in space plasmas. In these intricate plasma environments, extensive measurements have been conducted to monitor the fluctuations inherent in the perturbed electromagnetic (EM) field and the associated Poynting flux, specifically concerning kinetic Alfvén waves (KAWs). Traditionally, these fluctuations have been attributed to gyroradius correction terms within the framework of Maxwellian distributed plasmas. However, our study introduces an innovative perspective grounded in kinetic theory coupled with the Cairns distribution, adept at encapsulating the nonthermal nuances characterized by the index parameter Λ. Within the domain of the solar corona, our investigation centers on the perturbed EM field ratios and the Poynting flux of KAWs, with a foundation in the Cairns distribution function. It is noteworthy that the perpendicular components, although deemed less significant due to the dominance of k ⊥ over k ∥, remain unquantified regarding their relative insignificance. Similarly, the exploration of the imaginary part of the normalized EM field ratio has been a relatively understudied domain. Furthermore, we delve into the nuanced assessment of the power rate I x /I z characterizing the perpendicular and parallel normalized Poynting fluxes (S x and S z ). Intriguingly, we discern that large values of Λ, compared to their Maxwellian counterparts, manifest advantageous attributes, particularly concerning the energization of the plasma over extended distances along the ambient magnetic field lines. The analytical insights gleaned from this study find practical application in understanding phenomena within the solar atmosphere, particularly shedding light on the significant role played by nonthermal particles in the observed heating processes.

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Section: Introductionmentioning

confidence: 99%

Solar Coronal Heating by Kinetic Alfvén Waves

Ayaz,

Li,

Khan

2024

ApJ

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“…However, there have been no such studies, until now, that account for the combined effect of the ion beam and velocity shear in the resonant instability of KAWs. Although Barik et al (2019bBarik et al ( , 2019c proposed a theoretical model that was devoted to studying the combined effect of the ion beam and velocity shear in the generation of KAWs in Earth's magnetosphere, it was for complete Maxwellian plasmas. Nevertheless, many satellite observations have confirmed that the velocity distribution of plasma species follows a power law having a long energy tail, which is best described by a non-Maxwellian, like a κ-distribution (Vasyliunas 1968;Pierrard & Lazar 2010;Livadiotis 2015a;Lazar et al 2016).…”

Section: Introductionmentioning

confidence: 99%

Kinetic Alfvén Waves Excited by Multiple Free Energy Sources in the Magnetotail

Barik

Singh

Lakhina

2023

ApJ

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The generation of kinetic Alfvén waves (KAWs) is investigated through a three-component theoretical model incorporating ion beam and velocity shear as the sources of free energy in a non-Maxwellian κ-distributed plasmas. The model considers Maxwellian distributed background ions, drifting-Maxwellian beam ions, and κ-electrons as its constituent species. It is found that the combination of either positive velocity shear with counter-streaming beam ions or parallel streaming beam ions with negative velocity shear favors the excitation of KAWs. The effect of the κ-parameter on the excitation of KAWs under the combined energy sources is explored. The effect of plasma parameters such as number density, propagation angle, and temperature of plasma species on the real frequency and the growth rate of KAWs are examined. For the plasma parameters pertinent to the magnetotail region of Earth’s magnetosphere, the model is able to produce KAWs in the frequency range of ≈(5–67) mHz, which matches well with the recent ‘Time History of Events and Macroscale Interactions during Substorms (THEMIS)’ observations in the near-Earth magnetotail region.

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“…Furthermore, the excitation and propagation of KAW and other Alfvénic waves have been theoretically proposed in different space plasma environments, such as planetary magnetospheres resembling those of Mars and Saturn (Singh et al 2019;Barik et al 2021); dusty plasmas, as in planetary disks and cometary tails (Jatenco-Pereira et al 2014;Saini et al 2015); neutron stars or black hole surrounding plasmas (Nättilä & Beloborodov 2022); and many other astrophysical plasma environments (Sah 2010). The excitation of KAW and ion-acoustic waves by hot ion beams and velocity shear, through both resonant and non-resonant instabilities, has also been studied extensively and in depth in plasmas composed of hot electrons and cold ions (Lakhina 1990(Lakhina , 2008Barik et al 2019aBarik et al ,b,c, 2020. This mechanism for the excitation of ULF waves has been linked to the study of the polar cusp region of Earth's magnetosphere, but the results are more general and can be applied to any plasma of these characteristics.…”

Section: Introductionmentioning

confidence: 99%

The effect of heavy ions on the dispersion properties of kinetic Alfvén waves in astrophysical plasmas

Villarroel-Sepúlveda,

López,

Moya

2023

A&A

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Context. Spacecraft measurements have shown Kinetic Alfvén Waves propagating in the terrestrial magnetosphere at lower wave-normal angles than predicted by linear Vlasov theory of electron-proton plasmas. To explain these observations, it has been suggested that the abundant heavy ion populations in this region may have strong, non-trivial effects that allow Alfvénic waves to acquire right-handed polarization at lower angles with respect to the background magnetic field, as in the case of typical electron-proton plasma. Aims. We study the dispersion properties of Alfvénic waves in plasmas with stationary phase-space distribution functions with different heavy ion populations. Our extensive numerical analysis has allowed us to quantify the role of the heavy ion components on the transition from the left-hand polarized electromagnetic ion-cyclotron (EMIC) mode to the right-hand polarized kinetic Alfvén wave (KAW) mode. Methods. We used linear Vlasov-Maxwell theory to obtain the dispersion relation for oblique electromagnetic waves. The dispersion relation of Alfvén waves was obtained numerically by considering four different oxygen ion concentrations ranging between 0.0 and 0.2 for all propagation angles, as a function of both the wavenumber and the plasma beta parameter. Results. The inclusion of the heavy O+ ions is found to considerably reduce the transition angle from EMIC to KAW both as a function of the wave number and plasma beta. With increasing O+ concentrations, waves become more damped in specific wavenumber regions. However, the inclusion of oxygen ions may allow weakly damped KAW to effectively propagate at smaller wave-normal angles than in the electron-proton case, as suggested by observations.

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A theoretical model for the generation of Kinetic Alfvén waves in the Earth's Magnetosphere by Ion Beam and Velocity Shear

Cited by 8 publications

References 33 publications

Solar Coronal Heating by Kinetic Alfvén Waves

Solar Coronal Heating by Kinetic Alfvén Waves

Kinetic Alfvén Waves Excited by Multiple Free Energy Sources in the Magnetotail

The effect of heavy ions on the dispersion properties of kinetic Alfvén waves in astrophysical plasmas

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