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We present the formation of quasi-periodic cool spicule-like jets in the solar atmosphere using 2.5-D numerical simulation in two-fluid regime (ions+neutrals) under the presence of thermal conduction and ion-neutral collision. The non-linear, impulsive Alfv\'enic perturbations at the top of the photosphere trigger field aligned magnetoacoustic perturbations due to ponderomotive force. The transport of energy from Alfv\'en pulse to such vertical velocity perturbations due to ponderomotive force is considered as an initial trigger mechanism. Thereafter, these velocity perturbations steepen into the shocks followed by quasi-periodic rise and fall of the cool jets transporting mass in the overlying corona., Comment: In Press; Philosophical Transactions of the Royal Society A; 21 Pages; 06 Figures. Philosophical Transactions is the oldest English science journal in the world, which has been published continuously since March 1665 as launched by Henry Oldenburg

We describe a 2.5D MHD simulation describing the evolution of cool jets triggered by initial vertical velocity perturbations in the solar chromosphere. We implement random velocity pulses of amplitude 20-50 km/s between 1 Mm and 1.5 Mm, along with various switch-off periods between 50 s and 300 s. The applied vertical velocity pulses create a series of magnetoacoustic shocks steepening above TR. These shocks interact with each other in the inner corona, leading to complex localized velocity fields. The upward propagation of such perturbations creates low-pressure regions behind them, which propel a variety of cool jets and plasma flows. We study the transverse oscillations of a representative cool jet J1 , which moves up to the height of 6.2 Mm above the TR from its origin point. During its evolution, the plasma flows make the spine of jet J1 radially inhomogeneous, which is visible in the density and Alfv\'en speed smoothly varying across the jet. The highly dense J1 supports the propagating transverse wave of period of approximately 195 s with a phase speed of about 125 km/s. In the distance-time map of density, it is manifested as a transverse kink wave. However, the careful investigation of the distance-time maps of the x- and z-components of velocity reveals that these transverse waves are actually the mixed Alfv\'enic modes. The transverse wave shows evidence of damping in the jet. We conclude that the cross-field structuring of the density and characteristic Alfv\'en speed within J1 causes the onset of the resonant conversion and leakage of the wave energy outward to dissipate these transverse oscillations via resonant absorption. The wave energy flux is estimated as approximately of 1.0 x 10^6 ergs cm^{-2} s^{-1}. This energy, if it dissipates through the resonant absorption into the corona where the jet is propagated, is sufficient energy for the localized coronal heating., Comment: "Physics", 17 Pages, 6 Figures; in Special Issue in the Honor of Professor Marcel Goossens on the occasion of his 75th birthday

We use multiwavelength imaging observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) to study the evolution of Kelvin-Helmholtz (K-H) instability in a fan-spine magnetic field configuration. This magnetic topology exists near an active region AR12297 and is rooted in a nearby sunspot. In this magnetic configuration, two layers of cool plasma flow in parallel and interact with each other inside an elongated spine. The slower plasma flow (5 $km s^{-1}$) is the reflected stream along the spine field lines from the top, which interacts with the impulsive plasma upflows (114-144 km s$^{-1}$) from below. This process generates a shear motion and subsequent evolution of the K--H instability. The amplitude and characteristic wavelength of the K-H unstable vortices increase, satisfying the criterion of the fastest growing mode of this instability. We also describe that the velocity difference between two layers and velocity of K-H unstable vortices are greater than the Alfven speed in the second denser layer, which also satisfies the criterion of the growth of K-H instability. In the presence of the magnetic field and sheared counter streaming plasma as observed in the fan-spine topology, we estimate the parametric constant, $\Lambda\ge$1, that confirms the dominance of velocity shear and the evolution of the linear phase of the K-H instability. This observation indicates that in the presence of complex magnetic field structuring and flows, the fan-spine configuration may evolve into rapid heating, while the connectivity changes due to the fragmentation via the K-H instability., Comment: 14 pages, 8 figures, accepted for publication in ApJ

In this paper, we describe the kinematical and evolutionary properties of the impulsive cool jets in the solar atmosphere using numerical simulation by Godunov-type PLUTO code at two different strength of the quiet-Sun magnetic field (B=56, 112 Gauss). These types of chromospheric jets are originated by the pressure pulse, which mimics after effects of the localized heating in the lower solar atmosphere. These jets may be responsible for the transport of mass and energy in the localized upper atmosphere (i.e., corona). The detection of the height-time profiles for the jets, originated by imposing the different pressure pulses, exhibit the asymmetric near parabolic behaviour. This infers that the upward motion of the jet occurs under the influence of pressure perturbation. However, its downward motion is not only governed by the gravitational free fall, but also due to the complex plasma motions near its base under the effect of counter propagating pulses. Maximum height and life-time of the jets w.r.t. the strength of the pressure pulse show a linear increasing trend. This suggests that if the extent of the heating and thus pressure perturbations will be longer then more longer chromospheric jets can be triggered from the same location in the chromosphere. For the certain amplitude of pressure pulse, the strong magnetic field configuration (B=112 Gauss) leads more longer jet compared to the weaker field (B=56 Gauss). This suggests that the strong magnetic field guides the pressure pulse driven jets more efficiency towards the higher corona. In conclusion, our model mimics the properties and evolution of variety of the cool impulsive jets in the chromosphere (e.g., macrospicules, network jets, isolated repeated cool jets, confined \& small surges etc)., Comment: In Press Annales Geophysicae, 15 Pages, 11 Figures