Effect of a Radiation Cooling and Heating Function on Standing Longitudinal Oscillations in Coronal Loops

Abstract

Standing long-period (with the periods longer than several minutes) oscillations in large hot (with the temperature higher than 3 MK) coronal loops have been observed as the quasi-periodic modulation of the EUV and microwave intensity emission and the Doppler shift of coronal emission lines, and have been interpreted as standing slow magnetoacoustic (longitudinal) oscillations. Quasi-periodic pulsations of shorter periods, detected in thermal and non-thermal emissions in solar flares could be produced by a similar mechanism. We present theoretical modelling of the standing slow magnetoacoustic mode, showing that this mode of oscillation is highly sensitive to peculiarities of the radiative cooling and heating function. We generalised the theoretical model of standing slow magnetoacoustic oscillations in a hot plasma, including the effects of the radiative losses, and accounting for plasma heating. The heating mechanism is not specified and taken empirically to compensate the cooling by radiation and thermal-conduction. It is shown that the evolution of the oscillations is described by a generalised Burgers equation. Numerical solution of an initial value problem for the evolutionary equation demonstrates that different dependences of the radiative cooling and plasma heating on the temperature lead to different regimes of the oscillations, including growing, quasi-stationary and rapidly decaying. Our findings provide a theoretical foundation for probing the coronal heating function, and may explain the observations of decayless long-period quasi-periodic pulsations in flares. The hydrodynamic approach employed in this study should be considered with caution in the modelling of non-thermal emission associated with flares, as it misses potentially important non-hydrodynamic effects.

Accepted by The Astrophysical Journal (March 2016), 17 pages with 12 figures

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• Determination of the Coronal Magnetic Field by Hot Loop Oscillations
• Chromospheric Evaporation in an X1.0 Flare on 2014 March 29 Observed with IRIS and EIS
• SDO/AIA Observations of a Reflecting Longitudinal Wave in a Coronal Loop

Cited by in corpus (15)

• Modelling Quasi-Periodic Pulsations in Solar and Stellar Flares
• Slow-Mode Magnetoacoustic Waves in Coronal Loops
• Formation of quasi-periodic slow magnetoacoustic wave trains by the heating/cooling misbalance
• Statistical Study of GOES X-ray Quasi-Periodic Pulsations in Solar Flares
• Damping of slow magnetoacoustic oscillations by the misbalance between heating and cooling processes in the solar corona
• Very Long-period Pulsations before the Onset of Solar Flares
• Seismological constraints on the solar coronal heating function
• The effect of magnetic field on the damping of slow waves in the solar corona
• Effect of transport coefficients on excitation of flare-induced standing slow-mode waves in coronal loops
• Large-amplitude quasi-periodic pulsations as evidence of impulsive heating in hot transient loop systems detected in the EUV with SDO/AIA
• Role of Compressive Viscosity and Thermal Conductivity on the Damping of Slow Waves in the Coronal Loops With and Without Heating-Cooling Imbalance
• Determination of transport coefficients by coronal seismology of flare-induced slow-mode waves: Numerical parametric study of 1D loop model
• Excitation and Damping of Slow Magnetosonic Waves in Flaring Hot Coronal Loops: Effects of Compressive Viscosity
• Exploring Standing and Reflected Slow-mode Waves in Flaring Coronal Loops: A Parametric Study Using 2.5D MHD Modeling
• The effect of thermal misbalance on magnetohydrodynamic modes in coronal magnetic cylinders