arXiv subjects

R. Chandra

Publications and source records attributed to R. Chandra.

At least 19 recordsLinked to original sources

arXiv2025

The Birth of a Major Coronal Mass Ejection with Intricate Magnetic Structure from Multiple Active Regions

Coronal mass ejections (CMEs) are the eruptions of magnetised plasma from the Sun and are considered the main driver of adverse space weather events. Hence, undrstanding its formation process, particularly the magnetic topology, is critical for accurate space weather prediction. Here, based on imaging observations and three-dimensional (3D) data-constrained thermodynamic magnetohydrodynamical (MHD) simulation in spherical coordinates, we exhibit the birth of a CME with intricate magnetic structure from multiple active regions (ARs) due to 3D magnetic reconnection. It is observed as a coronal jet between active regions, accompanied by the back-flowing of filament materials along the jet spine after the passage of the eruptive filament. This jet connects two dimming regions within different active regions. This is an observational proxy of 3D magnetic reconnection between the CME flux rope and the null-point magnetic field lines crossing active regions. Hereafter, the thermodynamic data-constrained MHD simulation successfully reproduces the observed jet and the reconnection process that flux ropes partake in, leading to a CME flux rope with a complex magnetic structure distinct from its progenitor. The generality of this scenario is then validated by data-inspired MHD simulations in a simple multipolar magnetic configuration. This work demonstrates the role of multiple active regions in forming CMEs with intricate magnetic structures. On the one hand, a non-coherent flux rope where not all twisted magnetic field lines wind around one common axis is naturally formed. On the other hand, our findings suggest that the topology of a real CME flux rope may not be solely determined by a single active region, particularly during periods of solar maximum.

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arXiv2024

Filament eruption deflection and associated CMEs

We present the observations of a quiescent filament eruption and its deflection from the radial direction. The event occurred in the southern solar hemisphere on 2021 May 9 and was observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO), by the STEREO A Observatory and GONG. Part of the filament erupted in the west direction, while major part of the filament deviated towards east direction. LASCO observed a very weak CME towards the west direction where it faded quickly. Moreover, the eruption was associated with CME observed by STEREO A COR1 and COR2. Our observations provide the evidence that the filament eruption was highly non-radial in nature.

astro-ph.SR↗

arXiv2024

MANTA: A Negative-Triangularity NASEM-Compliant Fusion Pilot Plant

The MANTA (Modular Adjustable Negative Triangularity ARC-class) design study investigated how negative-triangularity (NT) may be leveraged in a compact, fusion pilot plant (FPP) to take a ``power-handling first" approach. The result is a pulsed, radiative, ELM-free tokamak that satisfies and exceeds the FPP requirements described in the 2021 National Academies of Sciences, Engineering, and Medicine report ``Bringing Fusion to the U.S. Grid". A self-consistent integrated modeling workflow predicts a fusion power of 450 MW and a plasma gain of 11.5 with only 23.5 MW of power to the scrape-off layer (SOL). This low $P_\text{SOL}$ together with impurity seeding and high density at the separatrix results in a peak heat flux of just 2.8 MW/m$^{2}$. MANTA's high aspect ratio provides space for a large central solenoid (CS), resulting in ${\sim}$15 minute inductive pulses. In spite of the high B fields on the CS and the other REBCO-based magnets, the electromagnetic stresses remain below structural and critical current density limits. Iterative optimization of neutron shielding and tritium breeding blanket yield tritium self-sufficiency with a breeding ratio of 1.15, a blanket power multiplication factor of 1.11, toroidal field coil lifetimes of $3100 \pm 400$ MW-yr, and poloidal field coil lifetimes of at least $890 \pm 40$ MW-yr. Following balance of plant modeling, MANTA is projected to generate 90 MW of net electricity at an electricity gain factor of ${\sim}2.4$. Systems-level economic analysis estimates an overnight cost of US\$3.4 billion, meeting the NASEM FPP requirement that this first-of-a-kind be less than US\$5 billion. The toroidal field coil cost and replacement time are the most critical upfront and lifetime cost drivers, respectively.

physics.plasm-ph↗

arXiv2018

Can High-Mode Magnetohydrodynamic Waves Propagating in a Spinning Macrospicule Be Unstable due to the Kelvin--Helmholtz Instability?

We investigate the conditions at which high-mode magnetohydrodynamic (MHD) waves propagating in a spinning solar macrospicule can become unstable with respect to the Kelvin--Helmholtz instability (KHI). We consider the macrospicule as a weakly twisted cylindrical magnetic flux tube moving along and rotating around its axis. Our study is based on the dispersion relation (in complex variables) of MHD waves obtained from the linearized MHD equations of an incompressible plasma for the macrospicule and cool ($\beta = 0$, rate of the plasma to the magnetic pressure) plasma for its environment. This dispersion equation is solved numerically at appropriate input parameters to find out an instability region or window that accommodates suitable unstable wavelengths on the order of the macro\-spicule width. It is established that an $m = 52$ MHD mode propagating in a macro\-spicule with width of $6$~Mm, axial velocity of $75$~km\,s$^{-1}$, and rotating one of $40$~km\,s$^{-1}$ can become unstable against the KHI with instability growth times of $2.2$ and $0.57$~min at $3$ and $5$~Mm unstable wavelengths, respectively. These growth times are much shorter than the macrospicule lifetime, which lasts about $15$~min. An increase or decease in the width of the jet would change the KHI growth times, which remain more or less on the same order when they are evaluated at wavelengths equal to the width or radius of the macrospicule. It is worth noting that the excited MHD modes are super-Alfv\'enic waves. A change in the background magnetic field can lead to another MHD mode number $m$ that ensures the required instability window.

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arXiv2018

Nuclear transition matrix elements for neutrinoless double-$\beta$ decay within mechanisms involving light Majorana neutrino mass and right-handed current

Employing the projected-Hartree-Fock-Bogoliubov (PHFB) model in conjunction with four different parametrizations of pairing plus multipolar effective two body interaction and three different parametrizations of Jastrow short range correlations, nuclear transition matrix elements for the neutrinoless double-$\beta $ decay of $^{94,96}$Zr, $^{100}$Mo, $^{110}$Pd, $^{128,130}$Te and $^{150}$Nd isotopes are calculated within mechanisms involving light Majorana neutrino mass and right handed current. Statistically, model specific uncertainties in sets of twelve nuclear transition matrix elements are estimated by calculating the averages along with the standard deviations. For the considered nuclei, \ the most stringent extracted on-axis limits on the effective light Majorana neutrino mass $ $, the effective weak coupling of right-handed leptonic current with right-handed hadronic current $<\lambda >$, and the effective weak coupling of right-handed leptonic current with left-handed hadronic current $<\eta >$ \ from the observed limit on half-life $T_{1/2}^{0\nu }$ of $^{130}$Te isotope are $0.33$ eV, $4.57\times 10^{-7}$ and $4.72\times 10^{-9}$, respectively.

nucl-th↗

arXiv2018

Horizontal photospheric flows trigger a filament eruption

A large filament composed principally of two sections erupted sequentially in the southern hemisphere on January 26 2016. The central, thick part of the northern section was first lifted up and lead to the eruption of the full filament. This event was observed in H-alpha with GONG and CLIMSO, and in ultraviolet (UV) with the AIA/SDO imager. The aim of the paper is to relate the photospheric motions below the filament and its environment to the eruption of the filament. An analysis of the photospheric motions using SDO/HMI continuum images with the coherent structure tracking (CST) algorithm developed to track granules, as well as large-scale photospheric flows, has been performed. The supergranule pattern is clearly visible outside the filament channel but difficult to detect inside because the modulus of the vector velocity is reduced in the filament channel, mainly in the magnetized areas. The horizontal photospheric flows are strong on the west side of the filament channel and oriented towards the filament. The ends of the filament sections are found in areas of concentration of corks. Whirled flows are found locally around the feet. The strong horizontal flows with an opposite direction to the differential rotation create strong shear and convergence along the magnetic polarity inversion line (PIL) in the filament channel. The filament has been destabilized by the converging flows, which initiate an ascent of the middle section of the filament until the filament reaches the critical height of the torus instability inducing, consequently, the eruption. The "n" decay index indicated an altitude of 60 Mm for the critical height. It is conjectured that the convergence along the PIL is due to the large-scale size cells of convection that transport the magnetic field to their borders.

astro-ph.SR↗

arXiv2018

Observations of Two Successive EUV Waves and their Mode Conversion

In this paper, we present the observations of two successive fast-mode extreme ultraviolet (EUV) wave events observed on 2016 July 23. Both fast-mode waves were observed by the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory (SDO) satellite, with a traveling speed of ~ 675 and 640 km/s, respectively. These two wave events were associated with two filament eruptions and two GOES M-class solar flares from the NOAA active region 12565, which was located near the western limb. The EUV waves mainly move toward the south direction. We observed the interaction of the EUV waves with a helmet streamer further away in the south. When either or one of the EUV waves penetrates into the helmet streamer, a slowly propagating wave with a traveling speed of ~ 150 km/s is observed along the streamer. We suggest that the slowly-moving waves are slow-mode waves, and interpret this phenomenon as the magnetohydrodynamic (MHD) wave mode conversion from the fast mode to the slow mode. Besides, we observed several stationary fronts in the north and south of the source region.

astro-ph.SR↗

arXiv2017

Solar Jet on 2014 April 16 Modeled by Kelvin--Helmholtz Instability

We study here the arising of Kelvin--Helmholtz Instability (KHI) in one fast jet of 2014 April 16 observed by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamics Observatory (SDO) in different UV and EUV wavelengths. The evolution of jet indicates the blob like structure at its boundary which could be the observational evidence of the KHI. We model the jet as a moving cylindrical magnetic flux tube of radius $a$ embedded in a magnetic field B_i and surrounded by rest magnetized plasma with magnetic field B_e. We explore the propagation of the kink MHD mode along the jet that can become unstable against the KHI if its speed exceeds a critical value. Concerning magnetic fields topology we consider three different configurations, notably of (i) spatially homogeneous magnetic fields (untwisted magnetic flux tube), (ii) internal (label `i') twisted magnetic field and external homogeneous one (label `e') (single-twisted flux tube), and (iii) both internal and external twisted magnetic fields (double-twisted magnetic flux tube). Plasma densities in the two media rho_i and rho_e are assumed to be homogeneous. The density contrast is defined in two ways: first as rho_e/rho_i and second as rho_e/(rho_i + rho_e). Computations show that the KHI can occur at accessible flow velocities in all the cases of untwisted and single-twisted flux tubes. It turns out, however, that in the case of a double-twisted flux tube the KHI can merge at an accessible jet speed only when the density contrast is calculated from the ratio rho_e/(rho_i} + rho_e). Evaluated KHI developing times and kink mode wave phase velocities at wavelength of 4 Mm lie in the ranges of 1--6.2 min and 202--271 km/s, respectively---all being reasonable for the modeled jet.

astro-ph.SR↗

arXiv2017

Large-Amplitude Longitudinal Oscillations Triggered by the Merging of Two Solar Filaments: Observations and Magnetic Field Analysis

We follow the eruption of two related intermediate filaments observed in H$\alpha$ (from GONG) and in EUV (from SDO/AIA) and the resulting large-amplitude longitudinal oscillations of the plasma in the filament channels. The events occurred in and around the decayed active region AR12486 on 2016 January 26. Our detailed study of the oscillation reveals that the periods of the oscillations are about one hour. In H$\alpha$ the period decreases with time and exhibits strong damping. The analysis of 171~\AA\ images shows that the oscillation has two phases, an initial long period phase and a subsequent oscillation with a shorter period. In this wavelength the damping appears weaker than in H$\alpha$. The velocity is the largest ever detected in a prominence oscillation, approximately 100 $\mathrm{\, km \, s^{-1}}$. Using SDO/HMI magnetograms we reconstruct the magnetic field of the filaments modeled as flux ropes by using a flux-rope insertion method. Applying seismological techniques we determine that the radii of curvature of the field lines in which cool plasma is condensed are in the range 75-120~Mm, in agreement with the reconstructed field. In addition, we infer a field strength of $\ge7$ to 30 gauss, depending on the electron density assumed; that is also in agreement with the values from the reconstruction (8-20 gauss). The poloidal flux is zero and the axis flux is of the order of 10$^{20}$ to 10$^{21}$ Mx, confirming the high shear existing even in a non-active filament.

astro-ph.SR↗

arXiv2017

A Study of a long duration B9 flare-CME event and associated piston-driven shock

We present and discuss here the observations of a small long duration GOES B- class flare associated with a quiescent filament eruption, a global EUV wave and a CME on 2011 May 11. The event was well observed by the Solar Dynamics Observatory (SDO), GONG H{\alpha}, STEREO and HiRAS spectrograph. As the fil- ament erupted, ahead of the filament we observed the propagation of EIT wave fronts, as well as two flare ribbons on both sides of the polarity inversion line (PIL) on the solar surface. The observations show the co-existence of two types of EUV waves, i.e., a fast and a slow one. A type II radio burst with up to the third harmonic component was also associated with this event. The evolution of pho- tospheric magnetic field showed flux emergence and cancellation at the filament site before its eruption.

astro-ph.SR↗

arXiv2017

Two neutrino double-$\beta $ decay of $94\leq A\leq 150$ nuclei for the 0$^{+}\rightarrow $2$^{+}$ transition

Within the PHFB approach, the $0^{+}\rightarrow 2^{+}$ transition of two neutrino double-$\beta $ decay of $^{94,96}$Zr, $^{100}$Mo, $^{104}$Ru, $^{110}$Pd, $^{128,130}$Te and $^{150}$Nd isotopes is studied employing wave functions generated with four different parametrizations of the pairing plus multipole type of two-nucleon interaction and the summation method. In comparison to the $0^{+}\rightarrow 0^{+}$ transition, the nuclear transition matrix elements $M_{2\nu }(2^{+})$ are quite sensitive to the deformation of the yrast 2$^{+}$ state. Consideration of the available theoretical and experimental results suggest that the observation of the 0$% ^{+}\rightarrow $2$^{+}$ transition of $2\nu \beta ^{-}\beta ^{-}$ decay may be possible in $^{96}$Zr, $^{100}$Mo, $^{130}$Te and $^{150}$Nd isotopes. The effect of deformation on the $M_{2\nu }(2^{+})$ is also studied.

nucl-th↗

arXiv2017

Slippage of Jets Explained by the Magnetic Topology of NOAA Active Region 12035

In this study, we present the investigation of eleven recurring solar jets originated from two different sites (site 1 and site 2) close to each other (~ 11 Mm) in the NOAA active region (AR) 12035 during 15--16 April 2014. The jets were observed by the Atmospheric Imaging Assembly (AIA) telescope onboard the Solar Dynamics Observatory (SDO) satellite. Two jets were observed by the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India telescope in H-alpha. On 15 April flux emergence is important in site 1 while on 16 April flux emergence and cancellation mechanisms are involved in both sites. The jets of both sites have parallel trajectories and move to the south with a speed between 100 and 360 km/s. We observed some connection between the two sites with some transfer of brightening. The jets of site 2 occurred during the second day and have a tendency to move towards the jets of site 1 and merge with them. We conjecture that the slippage of the jets could be explained by the complex topology of the region with the presence of a few low-altitude null points and many quasi-separatrix layers (QSLs), which could intersect with one another.

astro-ph.SR↗

arXiv2017

Spin-tensor decomposition of nuclear transition matrix elements for neutrinoless double-$\beta $ decay of $^{76}$Ge and $^{82}$Se nuclei within PHFB approach

Employing the PHFB model, nuclear transition matrix elements $M^{\left( K\right) }$ for the neutrinoless double-$\beta^{-} $ decay of $\ ^{76}$Ge and $^{82}$Se isotopes are calculated within mechanisms involving light as well as heavy Majorana neutrinos, and classical Majorons by considering the spin-tensor decomposition of realistic KUO and empirical JUN45 effective two-body interaction. It is noticed that the effects due to the SRC on NTMEs $M^{\left( 0\nu \right) }$ and $M^{\left( 0N\right) }$ due to the exchange of light and heavy Majorana neutrinos, respectively, is maximally incorporated by the central part of the effective two-body interaction, which varies by a small amount with the inclusion of spin-orbit and tensor components. The maximum uncertainty in the average NTMEs $\overline{M}^{(0\nu)}$ and $\overline{M}^{(0N)}$ turns out to be about 10\% and 37\%, respectively.

nucl-th↗

arXiv2017

Kelvin--Helmholtz instability in a twisting solar polar coronal hole jet observed by \emph{SDO}/AIA

We investigate the conditions under which the fluting ($m = 2$), $m = 3$, and $m = 12$ magnetohydrodynamic (MHD) modes in a uniformly twisted flux tube moving along its axis become unstable in order to model the Kelvin--Helmholtz (KH) instability in a twisting solar coronal hole jet near the northern pole of the Sun. Using a twisting jet of 2010 August 21 by \emph{SDO}/AIA and other observations of coronal jets we set the parameters of our theoretical model and have obtained that in a twisted magnetic flux tube of radius of $9.8$~Mm, at a density contrast of $0.474$ and fixed Alfv\'en Mach number of ${\cong}0.76$, for three MHD modes there exist instability windows whose width crucially depends upon the internal magnetic field twist. It is found that for the considered modes an azimuthal magnetic field of $1.3$--$1.4$~G (computed at the tube boundary) makes the width of the instability windows equal to zero, that is, it suppress the KH instability onset. On the other hand, the times for developing KH instability of the $m = 12$ MHD mode at instability wavelengths between $15$ and $12$~Mm turn out to be in the range of $1.9$ to $4.7$~minutes that is in agreement with the growth rates estimated from the temporal evolution of the observed unstable jet's blobs in their initial stage.

astro-ph.SR↗

arXiv2017

Two Step Filament Eruption During 14-15 March 2015

We present here an interesting two-step filament eruption during 14-15 March 2015. The filament was located in NOAA AR 12297 and associated with a halo Coronal Mass Ejection (CME). We use observations from the Atmospheric Imaging Assembly (AIA) and Heliospheric Magnetic Imager (HMI) instruments onboard the Solar Dynamics Observatory (SDO), and from the Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO). We also use H-alpha data from the Global Oscillation Network Group (GONG) telescope and the Kanzelhoehe Solar Observatory. The filament shows a first step eruption on 14 March 2015 and it stops its rise at a projected altitude ~ 125 Mm on the solar disk. It remains at this height for ~ 12 hrs. Finally it eruptes on 15 March 2015 and produced a halo CME. We also find jet activity in the active region during both days, which could help the filament de-stabilization and eruption. The decay index is calculated to understand this two-step eruption. The eruption could be due to the presence of successive instability-stability-instability zones as the filament is rising.

astro-ph.SR↗

arXiv2017

The transition from eruptive to confined flares in the same active region

Solar flares are sudden and violent releases of magnetic energy in the solar atmosphere that can be divided in eruptive flares, when plasma is ejected from the solar atmosphere, resulting in a coronal mass ejection (CME), and confined flares when no CME is associated with the flare. We present a case-study showing the evolution of key topological structures, such as spines and fans which may determine the eruptive versus non-eruptive behavior of the series of eruptive flares, followed by confined flares, which are all originating from the same site. To study the connectivity of the different flux domains and their evolution, we compute a potential magnetic field model of the active region. Quasi-separatrix layers are retrieved from the magnetic field extrapolation. The change of behavior of the flares from one day to the next -eruptive to confined- can be attributed to the change of orientation of the magnetic field below the fan with respect to the orientation of the overlaying spine, rather than an overall change in the stability of the large scale field. Flares tend to be more-and-more confined when the field that supports the filament and the overlying field gradually become less-and-less anti-parallel, as a direct result of changes in the photospheric flux distribution, being themselves driven by continuous shearing motions of the different magnetic flux concentrations.

astro-ph.SR↗

arXiv2016

Blowout Jets and Impulsive Eruptive Flare in a Bald-Patch Topology

Context: A subclass of broad EUV and X-ray jets, called blowout jets, have become a topic of research since they could be the link between standard collimated jets and CMEs.} Aim: Our aim is to understand the origin of a series of broad jets, some accompanied by flares and associated with narrow and jet-like CMEs. Methods: We analyze observations of a series of recurrent broad jets observed in AR 10484 on 21-24 October 2003. In particular, one of them occurred simultaneously with an M2.4 flare on 23 October at 02:41 UT (SOLA2003-10-23). Both events were observed by ARIES H-alpha Solar Tower-Telescope, TRACE, SOHO, and RHESSI instruments. The flare was very impulsive and followed by a narrow CME. A local force-free model of AR 10484 is the basis to compute its topology. We find bald patches (BPs) at the flare site. This BP topology is present for at least two days before. Large-scale field lines, associated with the BPs, represent open loops. This is confirmed by a global PFSS model. Following the brightest leading edge of the H-alpha and EUV jet emission, we can temporarily associate it with a narrow CME. Results: Considering their characteristics, the observed broad jets appear to be of the blowout class. As the most plausible scenario, we propose that magnetic reconnection could occur at the BP separatrices forced by the destabilization of a continuously reformed flux rope underlying them. The reconnection process could bring the cool flux-rope material into the reconnected open field lines driving the series of recurrent blowout jets and accompanying CMEs. Conclusions: Based on a model of the coronal field, we compute the AR 10484 topology at the location where flaring and blowout jets occurred from 21 to 24 October 2003. This topology can consistently explain the origin of these events.

astro-ph.SR↗

arXiv2016

Multi-wavelength view of an M2.2 Solar Flare on 26 November 2000

In this paper, we present a study of an M2.2 class solar flare of 26 November 2000 from NOAA AR 9236. The flare was well observed by various ground based observatories (ARIES, Learmonths Solar Observatory) and space borne instruments (SOHO, HXRS, GOES) in time interval between 02:30 UT to 04:00 UT. The flare started with long arc-shape outer flare ribbon. Afterwards the main flare starts with two main ribbons. Initially the outer ribbons start to expand with an average speed ($\sim$ 20 km s$^{-1}$) and later it shows contraction. The flare was associated with partial halo coronal mass ejection (CMEs) which has average speed of 495 km s$^{-1}$. The SOHO/MDI observations show that the active region was in quadrupolar magnetic configuration. The flux cancellation was observed before the flare onset close to flare site. Our analysis indicate the flare was initiated by the magnetic breakout mechanism.

astro-ph.SR↗