An event study on broadband electric field noises and electron distributions in the lunar wake boundary
Abstract Wave–particle interactions are fundamental processes in space plasma, and some plasma waves, including electrostatic solitary waves (ESWs), are recognised as broadband noises (BBNs) in the electric field spectral data. Spacecraft observations in recent decades have detected BBNs around the...
| Main Authors: | , , , , , , , , , , , , , |
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SpringerOpen
2022-01-01
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| Series: | Earth, Planets and Space |
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| Online Access: | https://doi.org/10.1186/s40623-021-01566-2 |
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| author | Masaki N. Nishino Yoshiya Kasahara Yuki Harada Yoshifumi Saito Hideo Tsunakawa Atsushi Kumamoto Shoichiro Yokota Futoshi Takahashi Masaki Matsushima Hidetoshi Shibuya Hisayoshi Shimizu Yukinaga Miyashita Yoshitaka Goto Takayuki Ono |
| author_facet | Masaki N. Nishino Yoshiya Kasahara Yuki Harada Yoshifumi Saito Hideo Tsunakawa Atsushi Kumamoto Shoichiro Yokota Futoshi Takahashi Masaki Matsushima Hidetoshi Shibuya Hisayoshi Shimizu Yukinaga Miyashita Yoshitaka Goto Takayuki Ono |
| author_sort | Masaki N. Nishino |
| collection | DOAJ |
| description | Abstract Wave–particle interactions are fundamental processes in space plasma, and some plasma waves, including electrostatic solitary waves (ESWs), are recognised as broadband noises (BBNs) in the electric field spectral data. Spacecraft observations in recent decades have detected BBNs around the Moon, but the generation mechanism of the BBNs is not fully understood. Here, we study a wake boundary traversal with BBNs observed by Kaguya, which includes an ESW event previously reported by Hashimoto et al. Geophys Res Lett 37:L19204 https://doi.org/10.1029/2010GL044529 (2010). Focusing on the relation between BBNs and electron pitch-angle distribution functions, we show that upward electron beams from the nightside lunar surface are effective for the generation of BBNs, in contrast to the original interpretation by Hashimoto et al. Geophys Res Lett 37:L19204 https://doi.org/10.1029/2010GL044529 (2010) that high-energy electrons accelerated by strong ambipolar electric fields excite ESWs in the region far from the Moon. When the BBNs were observed by the Kaguya spacecraft in the wake boundary, the spacecraft’s location was magnetically connected to the nightside lunar surface, and bi-streaming electron distributions of downward-going solar wind strahl component and upward-going field-aligned beams (at $$\sim$$ ∼ 124 eV) were detected. The interplanetary magnetic field was dominated by a positive $$B_Z$$ B Z (i.e. the northward component), and strahl electrons travelled in the antiparallel direction to the interplanetary magnetic field (i.e. southward), which enabled the strahl electrons to precipitate onto the nightside lunar surface directly. The incident solar wind electrons cause negative charging of the nightside lunar surface, which generates downward electric fields that accelerate electrons from the nightside surface toward higher altitudes along the magnetic field. The bidirectional electron distribution is not a sufficient condition for the BBN generation, and the distribution of upward electron beams seems to be correlated with the BBNs. Ambipolar electric fields in the wake boundary should also contribute to the electron acceleration toward higher altitudes and further intrusion of the solar wind ions into the deeper wake. We suggest that solar wind ion intrusion into the wake boundary is also an important factor that controls the BBN generation by facilitating the influx of solar wind electrons there. Graphical Abstract |
| first_indexed | 2024-04-11T20:45:03Z |
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| institution | Directory Open Access Journal |
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| language | English |
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| spelling | doaj.art-23dd1841f2fe42cbbb05794c505b11bb2022-12-22T04:04:03ZengSpringerOpenEarth, Planets and Space1880-59812022-01-0174111310.1186/s40623-021-01566-2An event study on broadband electric field noises and electron distributions in the lunar wake boundaryMasaki N. Nishino0Yoshiya Kasahara1Yuki Harada2Yoshifumi Saito3Hideo Tsunakawa4Atsushi Kumamoto5Shoichiro Yokota6Futoshi Takahashi7Masaki Matsushima8Hidetoshi Shibuya9Hisayoshi Shimizu10Yukinaga Miyashita11Yoshitaka Goto12Takayuki Ono13Institute of Space and Astronautical Science, Japan Aerospace Exploration AgencyKanazawa University, Kakuma-machiKyoto UniversityInstitute of Space and Astronautical Science, Japan Aerospace Exploration AgencyInstitute of Space and Astronautical Science, Japan Aerospace Exploration AgencyTohoku UniversityOsaka UniversityKyushu UniversityTokyo Institute of TechnologyDoshisha UniversityEarthquake Research Institute, The University of TokyoKorea Astronomy and Space Science InstituteKanazawa University, Kakuma-machiTohoku UniversityAbstract Wave–particle interactions are fundamental processes in space plasma, and some plasma waves, including electrostatic solitary waves (ESWs), are recognised as broadband noises (BBNs) in the electric field spectral data. Spacecraft observations in recent decades have detected BBNs around the Moon, but the generation mechanism of the BBNs is not fully understood. Here, we study a wake boundary traversal with BBNs observed by Kaguya, which includes an ESW event previously reported by Hashimoto et al. Geophys Res Lett 37:L19204 https://doi.org/10.1029/2010GL044529 (2010). Focusing on the relation between BBNs and electron pitch-angle distribution functions, we show that upward electron beams from the nightside lunar surface are effective for the generation of BBNs, in contrast to the original interpretation by Hashimoto et al. Geophys Res Lett 37:L19204 https://doi.org/10.1029/2010GL044529 (2010) that high-energy electrons accelerated by strong ambipolar electric fields excite ESWs in the region far from the Moon. When the BBNs were observed by the Kaguya spacecraft in the wake boundary, the spacecraft’s location was magnetically connected to the nightside lunar surface, and bi-streaming electron distributions of downward-going solar wind strahl component and upward-going field-aligned beams (at $$\sim$$ ∼ 124 eV) were detected. The interplanetary magnetic field was dominated by a positive $$B_Z$$ B Z (i.e. the northward component), and strahl electrons travelled in the antiparallel direction to the interplanetary magnetic field (i.e. southward), which enabled the strahl electrons to precipitate onto the nightside lunar surface directly. The incident solar wind electrons cause negative charging of the nightside lunar surface, which generates downward electric fields that accelerate electrons from the nightside surface toward higher altitudes along the magnetic field. The bidirectional electron distribution is not a sufficient condition for the BBN generation, and the distribution of upward electron beams seems to be correlated with the BBNs. Ambipolar electric fields in the wake boundary should also contribute to the electron acceleration toward higher altitudes and further intrusion of the solar wind ions into the deeper wake. We suggest that solar wind ion intrusion into the wake boundary is also an important factor that controls the BBN generation by facilitating the influx of solar wind electrons there. Graphical Abstracthttps://doi.org/10.1186/s40623-021-01566-2Lunar plasma environmentWave–particle interactionSolar windLunar wakeBroadband electric field noise |
| spellingShingle | Masaki N. Nishino Yoshiya Kasahara Yuki Harada Yoshifumi Saito Hideo Tsunakawa Atsushi Kumamoto Shoichiro Yokota Futoshi Takahashi Masaki Matsushima Hidetoshi Shibuya Hisayoshi Shimizu Yukinaga Miyashita Yoshitaka Goto Takayuki Ono An event study on broadband electric field noises and electron distributions in the lunar wake boundary Earth, Planets and Space Lunar plasma environment Wave–particle interaction Solar wind Lunar wake Broadband electric field noise |
| title | An event study on broadband electric field noises and electron distributions in the lunar wake boundary |
| title_full | An event study on broadband electric field noises and electron distributions in the lunar wake boundary |
| title_fullStr | An event study on broadband electric field noises and electron distributions in the lunar wake boundary |
| title_full_unstemmed | An event study on broadband electric field noises and electron distributions in the lunar wake boundary |
| title_short | An event study on broadband electric field noises and electron distributions in the lunar wake boundary |
| title_sort | event study on broadband electric field noises and electron distributions in the lunar wake boundary |
| topic | Lunar plasma environment Wave–particle interaction Solar wind Lunar wake Broadband electric field noise |
| url | https://doi.org/10.1186/s40623-021-01566-2 |
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