Abstract
ABSTRACT We present results revealing microwave pulsations produced in a model of a flaring twisted solar coronal loop, without any external oscillatory driver. Two types of oscillations are identified: slowly decaying oscillations with a period of about 70–75 s and amplitude of about 5–10 per cent seen in loops both with and without energetic electrons, and oscillations with a period of about 40 s and amplitude of a few tens of per cent observed only in loops with energetic electrons for about 100 s after the onset of fast energy release. We interpret the longer-period oscillations as the result of a standing kink mode modulating the average magnetic field strength in the loop, whilst the short-period intermittent oscillations associated with energetic electrons are likely to be produced by fast variations of the electric field, which produces energetic electrons in this scenario. The slowly decaying oscillations can explain the quasi-periodic pulsations often observed in the flaring corona.
Highlights
Waves and oscillations are ubiquitous in the solar corona (e.g. De Moortel & Nakariakov 2012; Nakariakov & Kolotkov 2020)
We present results revealing microwave pulsations produced in a model of a flaring twisted solar coronal loop, without any external oscillatory driver
We interpret the longer-period oscillations as the result of a standing kink mode modulating the average magnetic field strength in the loop, whilst the short-period intermittent oscillations associated with energetic electrons are likely to be produced by fast variations of the electric field which produces energetic electrons in this scenario
Summary
Waves and oscillations are ubiquitous in the solar corona (e.g. De Moortel & Nakariakov 2012; Nakariakov & Kolotkov 2020). The presence of QPPs in hard X-ray emission may indicate that MHD oscillations modulate particle acceleration in the corona, which, in turn, results in an oscillatory pattern in the intensity of bremsstrahlung produced by non-thermal electrons (e.g. McLaughlin et al 2018; Carley et al 2019; Hayes et al 2019). Another key question is whether the observed QPPs are due to auto-oscillations of the coronal magnetic field structure, or instead forced or triggered externally, for example by an incoming MHD wave. We investigate the time-domain properties of the MW emission produced by this flaring loop, showing that pulsations similar in many ways to observed QPPs can be produced without any external wave-like modulation
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