Harmonics of whistler-mode waves near the Moon

Tsugawa, Y.; Katoh, Yutai; Terada, Naoki; Tsunakawa, Hideo; Takahashi, Futoshi; Shibuya, H.; Shimizu, Hisayoshi; Matsushima, Masaki

doi:10.1186/s40623-015-0203-5

Cited by 10 publications

(7 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One‐hertz waves are whistler mode waves, which have frequencies near 1 Hz as measured in a spacecraft frame, and these waves are observed frequently in planetary upstream regions. These low‐frequency upstream whistler waves have been observed at Mercury (Fairfield & Behannon, ; Le et al, ; Orlowski et al, , ; Russell, ), Venus (Orlowski et al, ; Orlowski & Russell, ; Orlowski et al, ; Russell, ), Earth (Balikhin et al, ; Fairfield, ; Greenstadt et al, ; Heppner et al, ; Holzer et al, ; Hoppe et al, , ; Orlowski et al, , ; Russell et al, ; Russell & Farris, ; Russell, ; Tsurutani et al, ), Mars (Brain et al, ), Saturn (Orlowski et al, , ; Russell, ; Sulaiman et al, ), Jupiter (Tsurutani et al, ), Uranus (Smith et al, , ), the Moon (Halekas et al, , ; Nakagawa et al, , ; Tsugawa et al, , , , ), and at interplanetary shocks (Ramírez Vélez et al, ; Wilson et al, ). The frequency of these waves monotonically decreases for planets that are farther away from the Sun.…”

Section: Introductionmentioning

confidence: 95%

One‐Hertz Waves at Mars: MAVEN Observations

et al. 2018

View full text Add to dashboard Cite

We perform a survey of 1-Hz waves at Mars utilizing Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft observations for a Martian year. We find that the 1-Hz wave occurrence rate shows an apparent variation caused by masking of the waves by background turbulence during the times when the background turbulence levels are high. To correct for this turbulence masking, we select waves that occur in time intervals where the background turbulence levels are low. We find that the extreme ultraviolet flux does not affect the wave occurrence rate significantly, suggesting that the newly born pickup ions originating in the Mars's exosphere contribute minimally to the 1-Hz wave generation. We find that the wave occurrence rates are higher for low Mach numbers and low beta values than for high Mach numbers and high beta values. Further, we find that a high percentage of 1-Hz waves satisfy the group-standing condition, which suggests that a high percentage of the waves seen as monochromatic waves in the spacecraft frame can be broadband waves in the solar wind frame that have group velocities nearly equal and opposite to the solar wind velocity. We infer that the wave occurrence rate trends with the Mach number and proton beta are a consequence of how the Mach numbers and beta values influence the wave generation and damping or how those parameters affect the group-standing condition. Finally, we find that the 1-Hz waves are equally likely to be found in both the quasi-parallel and the quasi-perpendicular foreshock regions. Key Points:• One-hertz waves at Mars show an apparent occurrence rate variation due to masking of the waves during times of high background turbulence levels • The wave occurrence rates vary significantly with Mach numbers and proton beta values but do not vary significantly with EUV flux levels • The 1-Hz waves are observed in both the quasi-parallel and quasi-perpendicular foreshock regions with comparable occurrence rates waves can also be seen far upstream of the bow shock as their group velocities can exceed the solar wind flow velocity enabling them to propagate upstream against the solar wind flow.

show abstract

Section: Introductionmentioning

confidence: 95%

One‐Hertz Waves at Mars: MAVEN Observations

et al. 2018

View full text Add to dashboard Cite

show abstract

“…13,34 It predicts that multiple reflected whistlers gradually refract away from the Earth. Such predictions cannot be made for whistler modes in lunar crustal magnetic fields 35 or for low frequency whistlers at the bowshock 36 or near reconnection regions. 37,38 Nonuniform magnetic fields also exist in the exhaust region of helicon thrusters 14,16,39 or toroidal plasma devices [39][40][41][42] with the focus on plasma production rather than wave refraction.…”

Section: Introductionmentioning

confidence: 97%

Whistler modes in highly nonuniform magnetic fields. III. Propagation near mirror and cusp fields

Stenzel

Urrutia

2018

Physics of Plasmas

View full text Add to dashboard Cite

The properties of helicon modes in highly nonuniform magnetic fields are studied experimentally. The waves propagate in an essentially unbounded uniform laboratory plasma. Helicons with mode number m ¼ 1 are excited with a magnetic loop with dipole moment across the dc magnetic field. The wave fields are measured with a three-component magnetic probe movable in three orthogonal directions so as to resolve the spatial and temporal wave properties. The ambient magnetic field has the topology of a mirror or a cusp, produced by the superposition of a uniform axial field B 0 and the field of a current-carrying loop with the axis along B 0. The novel finding is the reflection of whistlers by a strong mirror magnetic field. The reflection arises when the magnetic field changes on a scale length shorter than the whistler wavelength. The simplest explanation for the reflection mechanism is the strong gradient of the refractive index which depends on the density and magnetic field. More detailed observations show that the incident wave splits when the k vector makes an angle larger than 90 with respect to B 0 which produces a parallel phase velocity component opposite to that of the incident wave. The reflection coefficient has been estimated to be close to unity. Interference between reflected and incident waves creates nodes in which the whistler mode becomes linearly polarized. When the magnetic field topology is that of a reversed field configuration (FRC), the incident wave is absorbed near the three-dimensional (3D) magnetic null point which prevents wave reflections. However, waves outside the separatrix are not absorbed and continue to propagate around the null point. When waves are excited inside the FRC, their polarization and helicon mode are reversed. Implications of these observations on research in space plasmas and helicon sources are pointed out.

show abstract

“…Their analysis suggested that broadband and narrow band waves are different views of the same waves propagating in the solar wind frame. In addition, the harmonics of the whistler waves have also been observed around lunar magnetic anomalies near the terminator region of Moon from Kaguya (Tsugawa et al 2015).…”

Section: Discussionmentioning

confidence: 94%

“…The abundance of positive charge in the range 10 −5 to 10 −7 cm −3 can accelerate electrons up to 1 keV and broadband electrostatic noise due to the counterstreaming electron beams has been found as a result of this process. Electrostatic solitary waves and whistler waves have been observed around Moon (Halekas et al 2006;Tsugawa et al 2011Tsugawa et al , 2012Tsugawa et al , 2015Nakagawa et al 2011). Electrostatic solitary waves has been observed on the day-side lunar surface as well as at the boundary of the lunar wake from Kaguya (Hashimoto et al 2010).…”

Section: Discussionmentioning

confidence: 98%

A new view on the solar wind interaction with the Moon

et al. 2015

View full text Add to dashboard Cite

Characterised by a surface bound exosphere and localised crustal magnetic fields, the Moon was considered as a passive object when solar wind interacts with it. However, the neutral particle and plasma measurements around the Moon by recent dedicated lunar missions, such as Chandrayaan-1, Kaguya, Chang'E-1, LRO, and ARTEMIS, as well as IBEX have revealed a variety of phenomena around the Moon which results from the interaction with solar wind, such as backscattering of solar wind protons as energetic neutral atoms (ENA) from lunar surface, sputtering of atoms from the lunar surface, formation of a "mini-magnetosphere" around lunar magnetic anomaly regions, as well as several plasma populations around the Moon, including solar wind protons scattered from the lunar surface, from the magnetic anomalies, pick-up ions, protons in lunar wake and more. This paper provides a review of these recent findings and presents the interaction of solar wind with the Moon in a new perspective.

show abstract

Harmonics of whistler-mode waves near the Moon

Cited by 10 publications

References 17 publications

One‐Hertz Waves at Mars: MAVEN Observations

One‐Hertz Waves at Mars: MAVEN Observations

Whistler modes in highly nonuniform magnetic fields. III. Propagation near mirror and cusp fields

A new view on the solar wind interaction with the Moon

Contact Info

Product

Resources

About