Growth of Outward Propagating Fast-magnetosonic/Whistler Waves in the Inner Heliosphere Observed by Parker Solar Probe

He, Jiansen; Wang, Ying; Zhu, Xingyu; Duan, Die; Verscharen, Daniel; Zhao, Guoqing

doi:10.3847/1538-4357/ac6c8e

Cited by 4 publications

(3 citation statements)

References 63 publications

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“…The SOP is inversely correlated with k B , 0 ( ) q . This indicates that the orthogonal components have a higher coherence at small propagation angles, and thus the quasi-parallel-propagating fluctuations are more wave-like (He et al 2022;Zhu et al 2023). At small propagation angles, the SOP is slightly greater at τ < 100 s than at τ > 100 s. The ellipticity distribution is isotropic at a constant period.…”

Section: Turbulent Energy Anisotropy Of Inertial-range Turbulencementioning

confidence: 95%

Evolution of the Interplanetary Turbulence and the Associated Turbulence Anisotropy in the Outer Heliosphere: VOYAGER 2 Observations

Zhu,

He,

Zank

et al. 2024

ApJ

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We study the radial evolution of the inertial-range solar wind plasma turbulence and its anisotropy in the outer heliosphere. We use magnetic field ( B ) measurements from the Voyager 2 spacecraft for heliocentric distances R from 1 to 33 au. We find that the perpendicular and trace power spectral densities (PSDs) of the magnetic field ( E B ⊥ and E B Tr ) still follow a Kolmogorov-like spectrum until 33 au. The parallel magnetic field PSD, E B ∥ , transits from a power-law index of −2 to −5/3 as the distance crosses R ∼ 10 au. The PSD at frequencies 0.01 Hz < f < 0.2 Hz flattens at R > 20 au, gradually approaching an f −1 spectrum, probably due to instrument noise. At 0.002 Hz < f < 0.1 Hz, quasi-parallel propagation dominates at 1 au < R < 7 au, with quasi-perpendicular propagation gradually emerging at R > 5 au. For R > 7 au, oblique propagation becomes the primary mode of propagation. At smaller frequencies of f < 0.01 Hz, E B ⊥ increases with propagation angle at 1 au < R < 5 au, and in contrast decreases with propagation angle at R > 5 au due to the enhanced power level at propagation angles smaller than 20°. Such enhancement may derive from the injection of wave energy from the pickup ion source into the background turbulent cascade, and the injected wave energy is transferred across scales without leaving local enhancements in E B ⊥ or E B Tr .

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Section: Turbulent Energy Anisotropy Of Inertial-range Turbulencementioning

confidence: 95%

Evolution of the Interplanetary Turbulence and the Associated Turbulence Anisotropy in the Outer Heliosphere: VOYAGER 2 Observations

Zhu,

He,

Zank

et al. 2024

ApJ

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“…PSP studies show the presence of ion-scale waves, as well as significant evidence that the associated proton VDFs are prone to kinetic instability, suggesting the local growth of these waves (Verniero et al 2020;Klein et al 2021;Verniero et al 2022). A kinetic wave event in the inner heliosphere solar wind shows a clear dispersion relationship of the outward-propagating FM/W wave and a growth rate spectrum reflecting the rapid growing process of the wave event (He et al 2022). We note that Bowen et al (2020a) investigate the properties of magnetic and electric field fluctuations associated with coherent ion-scale waves.…”

Section: Introductionmentioning

confidence: 97%

Non-field-aligned Proton Beams and Their Roles in the Growth of Fast Magnetosonic/Whistler Waves: Solar Orbiter Observations

Zhu

Duan

et al. 2023

ApJ

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The proton beam is an important population of the non-Maxwellian proton velocity distribution in the solar wind, but its role in wave activity remains unclear. In particular, the velocity vector of the proton beam and its influence on wave growth/damping have not been addressed before. Here we explore the origin and the associated particle dynamics of a kinetic wave event in the solar wind by analyzing measurements from Solar Orbiter and comparing them with theoretical predictions from linear Vlasov theory. We identify the waves as outward-propagating circularly polarized fast magnetosonic/whistler (FM/W) waves. The proton’s velocity distribution functions can destabilize FM/W waves. According to linear Vlasov theory, the velocity fluctuations of the core and the beam associated with FM/W waves render the original field-aligned background drift velocity non-field-aligned. This non-field-aligned drift velocity carrying the information of the velocity fluctuations of the core and the beam is responsible for the wave growth/damping. Specifically, for the FM/W waves we analyze, the non-field-aligned fluctuating velocity of the beam population is responsible for the growth of these unstable waves in the presence of a proton beam. In contrast, the core population plays the opposite role, partially suppressing the wave growth. Remarkably, the observed drift velocity vector between the core and the beam is not field aligned during an entire wave period. This result contrasts the traditional expectation that the proton beam is field aligned.

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“…The Parker Solar Probe (PSP) (Fox et al 2016) observations of ion-scale waves have been reported in the near-Sun plasma environment by many studies (e.g., Bowen et al 2020a;Perrone et al 2020;Verniero et al 2020;Klein et al 2021;Shi et al 2021;Zhao et al 2021b;He et al 2022). The reported ion-scale waves are often Alfvén ion cyclotron waves (ACWs) with wave frequencies around the proton gyrofrequency and kinetic Alfvén waves (KAWs) (Huang et al 2020;Duan et al 2021), which will be introduced in more detail below.…”

Section: Introductionmentioning

confidence: 99%

Statistical Properties of Alfvén Ion Cyclotron Waves and Kinetic Alfvén Waves in the Inner Heliosphere

Sun

Yang

Li³

et al. 2023

Res. Astron. Astrophys.

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Alfvén ion cyclotron waves (ACWs) and kinetic Alfvén waves (KAWs) are found to exist at < 0.3~au observed by Parker Solar Probe in Alfvénic slow solar winds. To examine the statistical properties of the background parameters for ACWs and KAWs and related wave disturbances, both wave events observed by Parker Solar Probe are selected and analyzed. The results show that there are obvious difference in the background and disturbance parameters between ACWs and KAWs. ACW events have a relatively higher occurrence rate but with a total duration slightly shorter than KAW events. The median background magnetic field magnitude and the related background solar wind speed of KAW events are larger than those of ACWs. The distributions of the relative disturbances of the proton velocity, proton temperature, he proton number density, and β cover wider ranges for ACW events than for KAW events. The results may be important for the understanding of the nature and characteristics of Alfvénic slow solar wind fluctuations at ion scales near the Sun, and provide the information of the background field and plasma parameters and the wave disturbances of ACWs and KAWs for further relevant theoretical modelling or numerical simulations.

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Growth of Outward Propagating Fast-magnetosonic/Whistler Waves in the Inner Heliosphere Observed by Parker Solar Probe

Cited by 4 publications

References 63 publications

Evolution of the Interplanetary Turbulence and the Associated Turbulence Anisotropy in the Outer Heliosphere: VOYAGER 2 Observations

Evolution of the Interplanetary Turbulence and the Associated Turbulence Anisotropy in the Outer Heliosphere: VOYAGER 2 Observations

Non-field-aligned Proton Beams and Their Roles in the Growth of Fast Magnetosonic/Whistler Waves: Solar Orbiter Observations

Statistical Properties of Alfvén Ion Cyclotron Waves and Kinetic Alfvén Waves in the Inner Heliosphere

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