Harmonic maser emissions from electrons with loss-cone distribution in solar active regions

Abstract

Electron cyclotron maser emission (ECME) is regarded as a plausible source for the coherent radio radiations from solar active regions (e.g., solar radio spikes). In this Letter, we present a 2D3V fully kinetic electromagnetic particle-in-cell (PIC) simulation to investigate the wave excitations and subsequent nonlinear processes induced by the energetic electrons in the loss-cone distribution. The ratio of the plasma frequency to the electron gyrofrequency ${\omega }_{pe}/{\Omega }_{ce}$ is set to 0.25, adequate for solar active region conditions. As a main result, we obtain strong emissions at the second-harmonic X mode (X2). While the fundamental X mode (X1) and the Z mode are amplified directly via the electron cyclotron maser instability, the X2 emissions can be produced by the nonlinear coalescence between two Z modes and between Z and X1 modes. This represents a novel generation mechanism for the harmonic emissions in plasmas with a low value of ${\omega }_{pe}/{\Omega }_{ce}$, which may resolve the escaping difficulty of explaining solar radio emissions with the ECME mechanism.

17 pages, 4 figures

References in corpus (7)

• Coherent Emission Mechanisms in Astrophysical Plasmas
• Is Cyclotron Maser Emission in Solar Flares Driven by a Horseshoe Distribution?
• PIC Simulation of Double Plasma Resonance and Zebra Pattern of Solar Radio Bursts
• An alternative form of the fundamental plasma emission through the coalescence of Z-mode waves with whistlers
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• Harmonic ECME Excited by Energetic Electrons Travelling Inside A Coronal Loop
• Narrowband Spikes Observed during the 2013 November 7 Flare

Cited by in corpus (7)

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• Verification of the standard theory of plasma emission with particle-in-cell simulations
• Loading loss-cone distributions in particle simulations
• Harmonic Electron Cyclotron Maser Emission along the Coronal Loop
• Particle-in-cell simulations of electron-positron cyclotron maser forming pulsar radio zebras
• Excitation of extraordinary modes inside the source of Saturn's kilometric radiation