Polymeric jets throw light on the origin and nature of the forest of solar spicules

Abstract

Spicules are plasma jets, observed in the dynamic interface region between the visible solar surface and the hot corona. At any given time, it is estimated that about 3 million spicules are present on the Sun. We find an intriguing parallel between the simulated spicular forest in a solar-like atmosphere and the numerous jets of polymeric fluids when both are subjected to harmonic forcing. In a radiative magnetohydrodynamic numerical simulation with sub-surface convection, solar global surface oscillations are excited similarly to those harmonic vibrations. The jets thus produced match remarkably well with the forests of spicules detected in observations of the Sun. Taken together, the numerical simulations of the Sun and the laboratory fluid dynamics experiments provide insights into the mechanism underlying the ubiquity of jets: the nonlinear focusing of quasi-periodic waves in anisotropic media of magnetized plasma as well as polymeric fluids under gravity is sufficient to generate a forest of spicules on the Sun. Spicular jets are highly elongated [4000 − 12000 km in length, 300 − 1100 km in width] features which are believed to transport momentum to the solar wind and non-thermal energy to heat the atmosphere[1, 2, 3]. Several mechanisms have been proposed to account for the formation of solar spicules, including granular squeezing[4], shocks and pulses[5, 6, 7], solar global acoustic waves[8, 9, 10]. So far, models based on these drivers have not been able to quantitatively match both the heights and abundance of the observed solar 1