In situgeneration of coronal Alfvén waves by jets

Abstract

Within the framework of 3D resistive MHD, we simulate the formation of a plasma jet with the morphology, upward velocity up to 130 km/s and timescale formation between 60 and 90 s after beginning of simulation, similar to those expected for Type II spicules. Initial results of this simulation were published in Paper (e.g., González-Avilés et al. 2018) and present paper is devoted to the analysis of transverse displacements and rotational type motion of the jet. Our results suggest that 3D magnetic reconnection may be responsible for the formation of the jet in Paper (González-Avilés et al. 2018). In this paper, by calculating times series of the velocity components v x and v y in different points near to the jet for various heights we find transverse oscillations in agreement with spicule observations. We also obtain a time-distance plot of the temperature in a cross-cut at the plane x =0.1 Mm and find significant transverse displacements of the jet. By analyzing temperature isosurfaces of 10 4 K with the distribution of v x , we find that if the line-of-sight (LOS) is approximately perpendicular to the jet axis then there is both motion towards and away from the observer across the width of the jet. This red-blue shift pattern of the jet is caused by rotational motion, initially clockwise and anticlockwise afterwards, which could be interpreted as torsional motion and may generate torsional Alfvén waves in the corona region. From a nearly vertical perspective of the jet the LOS velocity component shows a central blue-shift region surrounded by red-shifted plasma.

Vortex Motions in the Solar Atmosphere

“…However, simulations by González-Avilés et al. ( 2018 , 2019 ) did not include magnetoconvection yet rotational motions still naturally occurred. This finding is important in the context of coronal heating, as it provides evidence that torsional (Alfvén) waves may be excited directly in the corona where they can dissipate energy rather than having to navigate the highly inhomogeneous solar atmosphere.…”

I. Jet Formation and Evolution Due to 3D Magnetic Reconnection

“…By looking at the velocity field in a specific cross-cut of the spicule we can track the circular displacement of plasma that eventually can be identified with blue-red shifts. A detailed analysis on the torsional properties of the spicule, generated waves, rotational and radial displacements will be presented in a separate paper (González-Avilés et al 2017b).…”

Modos de ondas magnetohidrodinámicas influenciados por la corriente de desplazamiento

“…La demostración se inicia a partir de (17). Esta ecuación solamente se diferencia de (14) en la expresión del primer término de la izquierda.…”

“…donde ρ m la densidad del fluido. Las ondas de Alfvén se pueden encontrar, por ejemplo, en la atmósfera solar, el viento solar, la magnetosfera de la Tierra, plasmas astrofísicos y los producidos en laboratorios [5,[15][16][17][18]. Generalmente, en un fluido magneto-conductor el campo magnético no es uniforme en todo el espacio ocupado por el fluido.…”