Spectroscopic Observations and Modelling of Impulsive Alfvén Waves Along a Polar Coronal Jet

Abstract

Using the Hinode/EIS 2$"$ spectroscopic observations, we study the intensity, velocity, and FWHM variations of the strongest Fe XII 195.12 Å line along the jet to find the signature of Alfvén waves. We simulate numerically the impulsively generated Alfvén waves within the vertical Harris current-sheet, forming the jet plasma flows, and mimicking their observational signatures. Using the FLASH code and the atmospheric model with embedded weakly expanding magnetic field configuration within a vertical Harris current-sheet, we solve the two and half-dimensional (2.5-D) ideal magnetohydrodynamic (MHD) equations to study the evolution of Alfvén waves and vertical flows forming the plasma jet. At a height of $\sim 5\mathrm{Mm}$ from the base of the jet, the red-shifted velocity component of Fe XII 195.12 Å line attains its maximum ($5{\mathrm{km}\mathrm{s}}^{-1}$) which converts into a blue-shifted one between the altitude of $5-10\mathrm{Mm}$. The spectral intensity continously increases up to $10\mathrm{Mm}$, while FWHM still exhibits the low values with almost constant trend. This indicates that the reconnection point within the jet's magnetic field topology lies in the corona $5-10\mathrm{Mm}$ from its footpoint anchored in the Sun's surface. Beyond this height, FWHM shows a growing trend. This may be the signature of Alfvén waves that impulsively evolve due to reconnection and propagate along the jet. From our numerical data, we evaluate space- and time- averaged Alfvén waves velocity amplitudes at different heights in the jet's current-sheet, which contribute to the non-thermal motions and spectral line broadening. The synthetic width of Fe XII $195.12\mathring{\mathrm{A}}$ line exhibits similar trend of increment as in the observational data, possibly proving the existence of impulsively generated (by reconnection) Alfvén waves which propagate along the jet.

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Cited by in corpus (9)

• MHD Waves in open coronal structures
• Low-frequency Alfven Waves Produced by Magnetic Reconnection in the Sun's Magnetic Carpet
• Oscillations excited by plasmoids formed during magnetic reconnection in vertical gravitationally stratified current-sheet
• Magnetic swirls and associated fast magnetoacoustic kink waves in a solar chromospheric flux tube
• Propagation of Waves above a Plage as Observed by IRIS and SDO
• Origin of Quasi-Periodic Pulsation at the Base of Kink Unstable Jet
• Diagnostic of Homologous Solar Surge Plasma as observed by IRIS and SDO
• Numerical Simulations of Torsional Alfvén Waves in Axisymmetric Solar Magnetic Flux Tubes
• On modelling the kinematics and evolutionary properties of pressure pulse driven impulsive solar jets