Harmonics of whistler-mode waves near the Moon

Abstract

Harmonic spectral features of electromagnetic waves in the frequencies of several Hz around the Moon have been identified by Kaguya. The waves have steepened waveforms peculiarly in the compressional component. The fundamental waves have almost the same properties as narrowband whistler-mode waves with the frequencies near 1 Hz, which have been observed around the Moon. The waves are observed around the terminator region in the solar wind near the lunar magnetic anomalies at the altitudes under 120 km. We suggest that the harmonic spectra are a result of the nonlinear steepening of narrowband whistler-mode waves. Although the narrowband whistler-mode waves have been observed in the upstream region of many planetary bow shocks, such harmonics have rarely been observed there. Since the harmonics are more frequently observed at lower altitudes of the Moon, they are possibly caused by lunar intrinsic environments including lunar dusts and local structures of lunar magnetic anomalies.

One‐Hertz Waves at Mars: MAVEN Observations

“…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.…”

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

“…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.…”

A new view on the solar wind interaction with the Moon

“…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).…”

“…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).…”