Relativistic electrons produced by foreshock disturbances

Abstract

Foreshock disturbances -- large-scale (~1000 km to >30,000 km), transient (~5-10 per day - lasting ~10s of seconds to several minutes) structures [1,2] - generated by suprathermal (>100 eV to 100s of keV) ions [3,4] arise upstream of Earth's bow shock formed by the solar wind colliding with the Earth's magnetosphere. They have recently been found to accelerate ions to energies of several keV [5,6]. Although electrons in Saturn's high Mach number (M > 40) bow shock can be accelerated to relativistic energies (nearly 1000 keV) [7], it has hitherto been thought impossible to accelerate electrons at the much weaker (M < 20) Earth's bow shock beyond a few 10s of keV [8]. Here we report observations of electrons energized by foreshock disturbances to energies up to at least ~300 keV. Although such energetic electrons have been previously reported, their presence has been attributed to escaping magnetospheric particles [9,10] or solar events [11]. These relativistic electrons are not associated with any solar activity nor are they of magnetospheric origin. Further, current theories of ion acceleration in foreshock disturbances cannot account for electrons accelerated to the observed relativistic energies [12-17]. These electrons are clearly coming from the disturbances, leaving us with no explanation as to their origin.

arXiv comment14 pages, 8 figures, rejected from Nature, intend to submit to Phys. Rev. Lett

References in corpus (9)

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• Shocklets, SLAMS, and field-aligned ion beams in the terrestrial foreshock
• Electron acceleration to relativistic energies at a strong quasi-parallel shock wave
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• Particle-in-cell simulations of particle energization via shock drift acceleration from low Mach number quasi-perpendicular shocks in solar flares

Cited by in corpus (23)

• Electron energy partition across interplanetary shocks: I. Methodology and Data Product
• Observational Evidence for Stochastic Shock Drift Acceleration of Electrons at the Earth's Bow Shock
• Statistical study of particle acceleration in the core of foreshock transients
• Fermi acceleration of electrons inside foreshock transient cores
• Wave generation and heat flux suppression in astrophysical plasma systems
• dHybridR: a Hybrid--Particle-in-Cell Code Including Relativistic Ion Dynamics
• Theory of Electron Injection at Oblique Shock of Finite Thickness
• Electron energy partition across interplanetary shocks: III. Analysis
• Formation of foreshock transients and associated secondary shocks
• Magnetospheric Multiscale (MMS) observations of foreshock transients at their very early stage
• Lepton-driven Non-resonant Streaming Instability
• An in situ comparison of electron acceleration at collisionless shocks under differing upstream magnetic field orientations
• Revealing an unexpectedly low electron injection threshold via reinforced shock acceleration
• Electron acceleration by magnetosheath jet-driven bow waves
• Intense whistler-mode waves at foreshock transients: characteristics and regimes of wave-particle resonant interaction
• Pre-acceleration in the Electron Foreshock II: Oblique Whistler Waves
• Interpretation of flat energy spectra upstream of fast interplanetary shocks
• Multi-Mission Observations of Relativistic Electrons and High-Speed Jets Linked to Shock Generated Transients
• Criteria for ion acceleration in laboratory magnetized quasi-perpendicular collisionless shocks: when are 2D simulations enough?
• The Persistent Mystery of Collisionless Shocks
• Electron Heating in 2D Particle-in-Cell Simulations of Quasi-Perpendicular Low-Beta Shocks
• The electron foreshock at high-Mach-number nonrelativistic oblique shocks
• Observational Evidence of Magnetic Reconnection in the Terrestrial Foreshock Region