arXiv subjects

Balveer Singh

Publications and source records attributed to Balveer Singh.

6 recordsLinked to original sources

arXiv2026

On the Modeling of Kink Oscillations in Fine-Structured Coronal Loops with Field-aligned Nonlinear Longitudinal Disturbances

We investigate the influence of nonlinear longitudinal disturbances, triggered by an initial field-aligned velocity flow, on the damping of standing kink oscillations in fine-structured, cool coronal loop strands under isobaric conditions. Using two-dimensional ideal MHD simulations, we model different realistic flow geometries, bounded, unbounded, and external, and quantify their impact on wave excitation, damping, and energy leakage. Our modelled loop strand incorporates strong density contrasts ($d = 5$ and $d = 20$), providing a configuration consistent with cool-loop observations from Hinode/SOT and SDO/AIA. Our results show that while the nonlinear disturbances exert mild influence on the oscillation period, they substantially modify the damping time. Unbounded flows yield the strongest damping, reducing the damping time by up to $\sim 25\%$ compared to bounded flows, caused by enhanced wave-flow coupling and scattering. Longitudinally inhomogeneous flows further intensify the damping, with high-density strands exhibiting faster convergence toward the uniform-flow limit. In cases with supersonic internal flow, slow sausage-mode harmonics and weak slow shocks are additionally excited, indicating the generation of mixed-mode wave responses in flow-dominated loops. These findings demonstrate that realistic, spatially extended nonlinear disturbances play a significant role in the damping of kink oscillations and should be incorporated into forward modeling and coronal seismology diagnostics.

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arXiv2026

Recurrent Coronal Jets and QPPs: Periodic Reconnection and Localized Heating Across Quiet-Sun to Active Regions

We analyze quasi-periodic pulsations (QPPs) in recurrent coronal jets driven by periodic magnetic reconnection associated with successive flux emergence in the fan-spine magnetic topologies. Using the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), we investigate three long-lived recurring jets spanning quiet Sun to moderate-field-strength regions, each exhibiting recurrent eruptions linked to episodic reconnection. Wavelet analysis of multithermal AIA EUV jet-base light curves detects QPPs with periods of 6-13 min, exceeding typical p-mode oscillation periods. Distance-time analysis reveals quasi-periodic propagating ridges, interpreted as recurrent field-aligned plasma ejections, and morphological similarities to slow magnetoacoustic waves, which cannot be entirely excluded. However, the dominant photospheric unsigned flux periodicities of 10-32 min at the jet source regions favor the reconnection-driven interpretation. DEM analysis confirms multithermal plasma with the hottest emission concentrated near the jet base, and the QPP periods fall well below both radiative and conductive cooling timescales, implying persistent localized heating within the fan-spine configuration. These results demonstrate that periodic reconnection in fan-spine topologies drives recurrent jet eruptions and contributes to localized coronal heating across the quiet Sun, moderate-field strength regions, and active regions.

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arXiv2024

Alfvén Pulse Driven Spicule-like Jets in the Presence of Thermal Conduction and Ion-Neutral Collision in Two-Fluid Regime

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 Alfvénic perturbations at the top of the photosphere trigger field aligned magnetoacoustic perturbations due to ponderomotive force. The transport of energy from Alfvén 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.

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arXiv2023

Numerical Simulations of the Decaying Transverse Oscillations in the Cool Jet

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 Alfvén 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 Alfvénic modes. The transverse wave shows evidence of damping in the jet. We conclude that the cross-field structuring of the density and characteristic Alfvén 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.

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arXiv2021

Evolution of Kelvin-Helmholtz Instability in the Fan-Spine Topology

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, $Λ\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.

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arXiv2019

On modelling the kinematics and evolutionary properties of pressure pulse driven impulsive solar jets

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).

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