Relativistic turning acceleration of resonant electrons by coherent whistler mode waves in a dipole magnetic field

By Yoshiharu Omura, N. Furuya, Danny Summers. 2007

227 citations recorded by the source corpus.

[1] We report a very efficient process for accelerating high-energy electrons by coherent whistler mode waves in the Earth's dipole magnetic field, which we have found in our recent test particle simulations. The efficient acceleration process takes place for weakly relativistic seed electrons of a few hundred kiloelectronvolts. Under an assumption that the whistler mode wave packets are excited near the equatorial plane of the inner magnetosphere and propagate away from the equator, the acceleration process becomes irreversible. With a sufficiently long whistler mode wave packet of the order of 1 s, the energetic electrons are accelerated to a relativistic energy range of a few megaelectronvolts through a single resonant trapping process. We call this particular acceleration process relativistic turning acceleration (RTA), which could be a viable mechanism for increasing relativistic electron fluxes in the outer radiation belt. Necessary conditions for RTA are a relatively large amplitude of whistler mode waves, in the range of 50 to a few hundred picoteslas, and an initial kinetic energy of trapped electrons in the energy range of a few hundred kiloelectronvolts. The minimum energy of electrons accelerated by the RTA process and the maximum energy attained by it are derived analytically and verified by the test particle simulations.

Subfields: Astronomy and Astrophysics, Geophysics

View Paper: https://www.semanticscholar.org/paper/73a7f30d9689a11015caf9a8682fb54eca5371dd

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In Astronomy and Astrophysics

1. R. Thorne
2. Nigel P. Meredith
3. R. Horne
4. Wen Li
5. Binbin Ni
6. Y. Shprits
7. Jacob Bortnik
8. Danny Summers

In Geophysics

1. R. Thorne
2. Nigel P. Meredith
3. R. Horne
4. Wen Li
5. Binbin Ni
6. Y. Shprits
7. Danny Summers
8. S. Glauert

Citations in the corpus

• Global model of lower band and upper band chorus from multiple satellite observations (2012, background): “These very large amplitude waves lead to pronounced non-linear effects and, as such, may also be very effective for acceleration [e.g., Omura et al., 2007; Cattell et al., 2008; Bortnik et al., 2008b; Tao et al., 2012] and loss [Kersten et al., 2011] of relativistic electrons, depending on how…”
• Theory and simulation of the generation of whistler‐mode chorus (2008, unknown): “2.3. Relativistic Second-Order Resonance Condition [13] The relativistic cyclotron resonance condition for a whistler-mode wave with a fixed frequency has recently been analyzed by Omura et al. [2007] .”
• Oblique propagation of whistler mode waves in the chorus source region (2009, methodology): “…mode chorus and its effects on the outer Van Allen radiation belt, using both quasi-linear [e.g., Shprits et al., 2007; Summers et al., 2007] and nonlinear [e.g., Trakhtengerts et al., 2007; Omura et al., 2007, 2008] approaches to the description of wave interactions with energetic electrons.”
• Origin of energetic electron precipitation >30 keV into the atmosphere (2010, background): “Here we assume that the scattering can be treated as a diffusion problem where the electrons interact with a series of uncorrelated waves, but note that chorus waves also undergo nonlinear wave‐particle interactions which have yet to be fully assessed [e.g., Omura et al., 2007].”
• Discovery of very large amplitude whistler‐mode waves in Earth's radiation belts (2008, background): “5 MeV in 1s for waves with amplitudes of tens of mV/m [Omura et al., 2007].”
• Earth's Van Allen Radiation Belts: From Discovery to the Van Allen Probes Era (2019, background): “…that nonlinear interactions between waves and electrons are potentially important for affecting electron dynamics in the heart of the outer radiation belt (e.g., Albert, 2002; Bortnik et al., 2008; Foster et al., 2017; Inan et al., 1978; Omura et al., 2007, 2015; Omura & Zhao, 2012; Yoon, 2011).”
• THEMIS observations of long‐lived regions of large‐amplitude whistler waves in the inner magnetosphere (2008, background): “At such large amplitudes, nonlinear wave-particle interaction effects including phase trapping become important, and can accelerate particles to relativistic energies [Omura et al., 2007; Summers and Omura, 2007].”
• On the relationship between relativistic electron flux and solar wind velocity: Paulikas and Blake revisited (2010, background): “, 1998] nonlinear whistler interactions [Omura et al., 2007], and”
• Space Weather Effects in the Earth’s Radiation Belts (2018, background): “Energy gain for a single RTA interaction with the chorus rising tone shown in Fig.”
• Nonlinear mechanisms of lower-band and upper-band VLF chorus emissions in the magnetosphere (2009, background): “…et al., 1998, 2002, 2004a,b, 2007a,b; Roth et al., 1999;47 Summers and Ma, 2000; Albert, 2000, 2002; Miyoshi et al., 2003; Horne et al., 2005;48 Omura et al., 2007; Katoh and Omura, 2004, 2007a; Summers and Omura, 2007; Furuya49 et al., 2008; Katoh et al., 2008]50 Numerical modeling of chorus…”
• Resonant scattering of plasma sheet electrons leading to diffuse auroral precipitation: 2. Evaluation for whistler mode chorus waves (2011, background): “…turning acceleration (RTA) and ultrarelativistic acceleration (UTA) have been proposed as very efficient energization mechanisms for electrons interacting with discrete chorus wave packet(s) in cosmic plasma environments [e.g., Omura et al., 2007; Summers and Omura, 2007; Furuya et al., 2008].”