Sergei R. Kamaletdinov, Ivan Y. Vasko, Anton V. Artemyev
{"title":"无碰撞冲击中静电波的非线性电子散射","authors":"Sergei R. Kamaletdinov, Ivan Y. Vasko, Anton V. Artemyev","doi":"10.1017/s0022377824000217","DOIUrl":null,"url":null,"abstract":"<p>We present a theoretical analysis of electron pitch-angle scattering by ion-acoustic electrostatic fluctuations present in the Earth's bow shock and, presumably, collisionless shocks in general. We numerically simulate electron interaction with a single wave packet to demonstrate the scattering through phase bunching and phase trapping and quantify electron pitch-angle scattering in dependence on the wave amplitude and wave normal angle to the local magnetic field. The iterative mapping technique is used to model pitch-angle scattering of electrons by a large number of wave packets, which have been reported in the Earth's bow shock. Assuming that successive electron scatterings are not correlated, we revealed that the long-term dynamics of electrons is diffusive. The diffusion coefficient depends on the ratio <span><span><span data-mathjax-type=\"texmath\"><span>$\\varPhi _0/W$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline1.png\"/></span></span> between the wave packet amplitude and electron energy, <span><span><span data-mathjax-type=\"texmath\"><span>$D\\propto (\\varPhi _0/W)^{\\nu }$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline2.png\"/></span></span>. A quasi-linear scaling (<span><span><span data-mathjax-type=\"texmath\"><span>$\\nu \\approx 2$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline3.png\"/></span></span>) is observed for sufficiently small wave amplitudes, <span><span><span data-mathjax-type=\"texmath\"><span>$\\varPhi _0\\lesssim 10^{-3}W$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline4.png\"/></span></span>, while the diffusion is nonlinear (<span><span><span data-mathjax-type=\"texmath\"><span>$1<\\nu <2$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline5.png\"/></span></span>) above this threshold. We show that pitch-angle diffusion of <span><span><span data-mathjax-type=\"texmath\"><span>${\\lesssim }1$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline6.png\"/></span></span> keV electrons in the Earth's bow shock can be nonlinear. The corresponding diffusion coefficient scales with the intensity <span><span><span data-mathjax-type=\"texmath\"><span>$E_{w}^{2}$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline7.png\"/></span></span> of the electrostatic fluctuations in a nonlinear fashion, <span><span><span data-mathjax-type=\"texmath\"><span>$D\\propto E_{w}^{\\nu }$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline8.png\"/></span></span> with <span><span><span data-mathjax-type=\"texmath\"><span>$\\nu <2$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline9.png\"/></span></span>, while its expected values in the Earth's bow shock are <span><span><span data-mathjax-type=\"texmath\"><span>$D\\sim 0.1\\unicode{x2013}100$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline10.png\"/></span></span> <span><span><span data-mathjax-type=\"texmath\"><span>$(T_{e}/W)^{\\nu -1/2}\\,{\\rm rad}^{2}\\,{\\rm s}^{-1}$</span></span><img data-mimesubtype=\"png\" data-type=\"\" src=\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline11.png\"/></span></span>. We speculate that in the Earth's quasi-perpendicular bow shock the stochastic shock drift acceleration mechanism with pitch-angle scattering provided by the electrostatic fluctuations can contribute to the acceleration of thermal electrons up to approximately 1 keV. The potential effects of a finite perpendicular coherence scale of the wave packets on the efficiency of electron scattering are discussed.</p>","PeriodicalId":16846,"journal":{"name":"Journal of Plasma Physics","volume":"118 1","pages":""},"PeriodicalIF":2.1000,"publicationDate":"2024-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Nonlinear electron scattering by electrostatic waves in collisionless shocks\",\"authors\":\"Sergei R. Kamaletdinov, Ivan Y. Vasko, Anton V. Artemyev\",\"doi\":\"10.1017/s0022377824000217\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>We present a theoretical analysis of electron pitch-angle scattering by ion-acoustic electrostatic fluctuations present in the Earth's bow shock and, presumably, collisionless shocks in general. We numerically simulate electron interaction with a single wave packet to demonstrate the scattering through phase bunching and phase trapping and quantify electron pitch-angle scattering in dependence on the wave amplitude and wave normal angle to the local magnetic field. The iterative mapping technique is used to model pitch-angle scattering of electrons by a large number of wave packets, which have been reported in the Earth's bow shock. Assuming that successive electron scatterings are not correlated, we revealed that the long-term dynamics of electrons is diffusive. The diffusion coefficient depends on the ratio <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$\\\\varPhi _0/W$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline1.png\\\"/></span></span> between the wave packet amplitude and electron energy, <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$D\\\\propto (\\\\varPhi _0/W)^{\\\\nu }$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline2.png\\\"/></span></span>. A quasi-linear scaling (<span><span><span data-mathjax-type=\\\"texmath\\\"><span>$\\\\nu \\\\approx 2$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline3.png\\\"/></span></span>) is observed for sufficiently small wave amplitudes, <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$\\\\varPhi _0\\\\lesssim 10^{-3}W$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline4.png\\\"/></span></span>, while the diffusion is nonlinear (<span><span><span data-mathjax-type=\\\"texmath\\\"><span>$1<\\\\nu <2$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline5.png\\\"/></span></span>) above this threshold. We show that pitch-angle diffusion of <span><span><span data-mathjax-type=\\\"texmath\\\"><span>${\\\\lesssim }1$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline6.png\\\"/></span></span> keV electrons in the Earth's bow shock can be nonlinear. The corresponding diffusion coefficient scales with the intensity <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$E_{w}^{2}$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline7.png\\\"/></span></span> of the electrostatic fluctuations in a nonlinear fashion, <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$D\\\\propto E_{w}^{\\\\nu }$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline8.png\\\"/></span></span> with <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$\\\\nu <2$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline9.png\\\"/></span></span>, while its expected values in the Earth's bow shock are <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$D\\\\sim 0.1\\\\unicode{x2013}100$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline10.png\\\"/></span></span> <span><span><span data-mathjax-type=\\\"texmath\\\"><span>$(T_{e}/W)^{\\\\nu -1/2}\\\\,{\\\\rm rad}^{2}\\\\,{\\\\rm s}^{-1}$</span></span><img data-mimesubtype=\\\"png\\\" data-type=\\\"\\\" src=\\\"https://static.cambridge.org/binary/version/id/urn:cambridge.org:id:binary:20240306134914101-0214:S0022377824000217:S0022377824000217_inline11.png\\\"/></span></span>. We speculate that in the Earth's quasi-perpendicular bow shock the stochastic shock drift acceleration mechanism with pitch-angle scattering provided by the electrostatic fluctuations can contribute to the acceleration of thermal electrons up to approximately 1 keV. The potential effects of a finite perpendicular coherence scale of the wave packets on the efficiency of electron scattering are discussed.</p>\",\"PeriodicalId\":16846,\"journal\":{\"name\":\"Journal of Plasma Physics\",\"volume\":\"118 1\",\"pages\":\"\"},\"PeriodicalIF\":2.1000,\"publicationDate\":\"2024-03-07\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Plasma Physics\",\"FirstCategoryId\":\"101\",\"ListUrlMain\":\"https://doi.org/10.1017/s0022377824000217\",\"RegionNum\":3,\"RegionCategory\":\"物理与天体物理\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"PHYSICS, FLUIDS & PLASMAS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Plasma Physics","FirstCategoryId":"101","ListUrlMain":"https://doi.org/10.1017/s0022377824000217","RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"PHYSICS, FLUIDS & PLASMAS","Score":null,"Total":0}
Nonlinear electron scattering by electrostatic waves in collisionless shocks
We present a theoretical analysis of electron pitch-angle scattering by ion-acoustic electrostatic fluctuations present in the Earth's bow shock and, presumably, collisionless shocks in general. We numerically simulate electron interaction with a single wave packet to demonstrate the scattering through phase bunching and phase trapping and quantify electron pitch-angle scattering in dependence on the wave amplitude and wave normal angle to the local magnetic field. The iterative mapping technique is used to model pitch-angle scattering of electrons by a large number of wave packets, which have been reported in the Earth's bow shock. Assuming that successive electron scatterings are not correlated, we revealed that the long-term dynamics of electrons is diffusive. The diffusion coefficient depends on the ratio $\varPhi _0/W$ between the wave packet amplitude and electron energy, $D\propto (\varPhi _0/W)^{\nu }$. A quasi-linear scaling ($\nu \approx 2$) is observed for sufficiently small wave amplitudes, $\varPhi _0\lesssim 10^{-3}W$, while the diffusion is nonlinear ($1<\nu <2$) above this threshold. We show that pitch-angle diffusion of ${\lesssim }1$ keV electrons in the Earth's bow shock can be nonlinear. The corresponding diffusion coefficient scales with the intensity $E_{w}^{2}$ of the electrostatic fluctuations in a nonlinear fashion, $D\propto E_{w}^{\nu }$ with $\nu <2$, while its expected values in the Earth's bow shock are $D\sim 0.1\unicode{x2013}100$$(T_{e}/W)^{\nu -1/2}\,{\rm rad}^{2}\,{\rm s}^{-1}$. We speculate that in the Earth's quasi-perpendicular bow shock the stochastic shock drift acceleration mechanism with pitch-angle scattering provided by the electrostatic fluctuations can contribute to the acceleration of thermal electrons up to approximately 1 keV. The potential effects of a finite perpendicular coherence scale of the wave packets on the efficiency of electron scattering are discussed.
期刊介绍:
JPP aspires to be the intellectual home of those who think of plasma physics as a fundamental discipline. The journal focuses on publishing research on laboratory plasmas (including magnetically confined and inertial fusion plasmas), space physics and plasma astrophysics that takes advantage of the rapid ongoing progress in instrumentation and computing to advance fundamental understanding of multiscale plasma physics. The Journal welcomes submissions of analytical, numerical, observational and experimental work: both original research and tutorial- or review-style papers, as well as proposals for its Lecture Notes series.