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López RA, Shaaban SM, Lazar M, Poedts S, Yoon PH, Micera A, Lapenta G. Particle-in-cell Simulations of the Whistler Heat-flux Instability in Solar Wind Conditions. THE ASTROPHYSICAL JOURNAL. LETTERS 2019; 882:10.3847/2041-8213/ab398b. [PMID: 32042401 PMCID: PMC7008930 DOI: 10.3847/2041-8213/ab398b] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In collision-poor plasmas from space, e.g., solar wind or stellar outflows, the heat flux carried by the strahl or beaming electrons is expected to be regulated by the self-generated instabilities. Recently, simultaneous field and particle observations have indeed revealed enhanced whistler-like fluctuations in the presence of counter-beaming populations of electrons, connecting these fluctuations to the whistler heat-flux instability (WHFI). This instability is predicted only for limited conditions of electron beam-plasmas, and has not yet been captured in numerical simulations. In this Letter we report the first simulations of WHFI in particle-in-cell setups, realistic for the solar wind conditions, and without temperature gradients or anisotropies to trigger the instability in the initiation phase. The velocity distributions have a complex reaction to the enhanced whistler fluctuations conditioning the instability saturation by a decrease of the relative drifts combined with induced (effective) temperature anisotropies (heating the core electrons and pitch-angle and energy scattering the strahl). These results are in good agreement with a recent quasilinear approach, and support therefore a largely accepted belief that WHFI saturates at moderate amplitudes. In the anti-sunward direction the strahl becomes skewed with a pitch-angle distribution decreasing in width as electron energy increases, which seems to be characteristic of self-generated whistlers and not to small-scale turbulence.
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Affiliation(s)
- R A López
- Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
| | - S M Shaaban
- Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
- Theoretical Physics Research Group, Physics Department, Faculty of Science, Mansoura University, 35516, Mansoura, Egypt
| | - M Lazar
- Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
- Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - S Poedts
- Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
| | - P H Yoon
- Institute for Physical Science and Technology, University of Maryland, College Park, MD, USA
- School of Space Research, Kyung Hee University, Republic of Korea
- Korea Astronomy and Space Science Institute, Daejeon 34055, Republic of Korea
| | - A Micera
- Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
- Solar-Terrestrial Centre of Excellence-SIDC, Royal Observatory of Belgium, B-1180 Brussels, Belgium
| | - G Lapenta
- Centre for mathematical Plasma Astrophysics, KU Leuven, Celestijnenlaan 200B, B-3001 Leuven, Belgium
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Giagkiozis S, Wilson LB, Burch JL, Le Contel O, Ergun RE, Gershman DJ, Lindqvist PA, Mirioni L, Moore TE, Strangeway RJ. Statistical Study of the Properties of Magnetosheath Lion Roars. JOURNAL OF GEOPHYSICAL RESEARCH. SPACE PHYSICS 2018; 123:5435-5451. [PMID: 31709134 PMCID: PMC6839693 DOI: 10.1029/2018ja025343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Lion roars are narrowband whistler wave emissions that have been observed in several environments, such as planetary magnetosheaths, the Earth's magnetosphere, the solar wind, downstream of interplanetary shocks, and the cusp region. We present measurements of more than 30,000 such emissions observed by the Magnetospheric Multiscale spacecraft with high-cadence (8,192 samples/s) search coil magnetometer data. A semiautomatic algorithm was used to identify the emissions, and an adaptive interval algorithm in conjunction with minimum variance analysis was used to determine their wave vector. The properties of the waves are determined in both the spacecraft and plasma rest frame. The mean wave normal angle, with respect to the background magnetic field (B 0), plasma bulk flow velocity (V b ), and the coplanarity plane (V b × B 0) are 23°, 56°, and 0°, respectively. The average peak frequencies were ~31% of the electron gyrofrequency (ω ce ) observed in the spacecraft frame and ~18% of ω ce in the plasma rest frame. In the spacecraft frame, ~99% of the emissions had a frequency < ω ce , while 98% had a peak frequency < 0.72 ω ce in the plasma rest frame. None of the waves had frequencies lower than the lower hybrid frequency, ω. From the probability density function of the electron plasma β e , the ratio between the electron thermal and magnetic pressure, ~99.6% of the waves were observed with β e < 4 with a large narrow peak at 0.07 and two smaller, but wider, peaks at 1.26 and 2.28, while the average value was ~1.25.
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Affiliation(s)
- Stefanos Giagkiozis
- Automatic Control and Systems Engineering, University of Sheffield, Sheffield, UK
| | - Lynn B Wilson
- Heliophysics Science Division, NASA Goddard Spaceflight Center, Greenbelt, MD, USA
| | | | - Olivier Le Contel
- Laboratoire de Physique des Plasmas, UMR7648, CNRS, Ecole Polytechnique, Sorbonne Universités, Université Paris-Sud, Observatoire de Paris, Paris, France
| | - Robert E Ergun
- Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, CO, USA
| | - Daniel J Gershman
- Fields and Particles, NASA Goddard Space Flight Center, Greenbelt, MD, USA
- Department of Astronomy, University of Maryland, College Park, MD, USA
| | - Per-Arne Lindqvist
- Department of Space and Plasma Physics, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Laurent Mirioni
- Laboratoire de Physique des Plasmas (LPP), CNRS/ Ecole Polytechnique/ Sorbonne Universités UPMC/ Paris-Sud 11, Palaiseau, France
| | - Thomas E Moore
- Heliophysics Science Division, NASA Goddard Spaceflight Center, Greenbelt, MD, USA
| | - Robert J Strangeway
- Institute of Geophysics and Planetary Physics and Earth and Space Sciences, University of California, Los Angeles, CA, USA
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Lacombe C, Alexandrova O, Matteini L, Santolík O, Cornilleau-Wehrlin N, Mangeney A, de Conchy Y, Maksimovic M. WHISTLER MODE WAVES AND THE ELECTRON HEAT FLUX IN THE SOLAR WIND:CLUSTEROBSERVATIONS. ACTA ACUST UNITED AC 2014. [DOI: 10.1088/0004-637x/796/1/5] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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