scholarly journals Energy distribution of solar flare events

2018 ◽  
Vol 13 (S340) ◽  
pp. 53-54
Author(s):  
S. Sen ◽  
A. Mangalam ◽  
R. Ramesh
Keyword(s):  
Energy Distribution ◽  
Power Law ◽  
Free Field ◽  
Field Configuration ◽  
Radio Observatory ◽  
Radio Data ◽  
Power Law Index ◽  
Coronal Field ◽  
Force Free Field ◽  
Good Agreement

AbstractThe coronal field typically reorganizes itself to attain a force-free field configuration. We have evaluated the power law index of the energy distribution f(E) = f0E−α by using a model of relaxation incorporating different profile functions of winding number distribution f(w) based on braided topologies. We study the radio signatures that occur in the solar corona using the radio data obtained from the Gauribidanur Radio Observatory (IIA) and extract the power law index by using the Statistic-sensitive nonlinear iterative peak clipping (SNIP) algorithm. We see that the power law index obtained from the model is in good agreement with the calculated value from the radio data observation.

scholarly journals Super-giant pulses from the Crab pulsar: energy distribution and occurrence rate

2019 ◽  
Vol 490 (1) ◽  
pp. L12-L16 ◽  
Author(s):  
Apurba Bera ◽  
Jayaram N Chengalur
Keyword(s):  
Energy Distribution ◽  
Power Law ◽  
Pulse Energy ◽  
Occurrence Rate ◽  
Crab Pulsar ◽  
Limited Sample ◽  
Pulse Emission ◽  
High Fluences ◽  
Giant Pulses ◽  
Power Law Index

ABSTRACT We present statistical analysis of a fluence-limited sample of over 1100 giant pulses from the Crab pulsar, with fluence > 130 Jy ms at ∼1330 MHz. These were detected in ∼260 h of observation with the National Centre for Radio Astrophysics (NCRA) 15 m radio telescope. We find that the pulse-energy distribution follows a power law with index $\rm \alpha \approx -3$ at least up to a fluence of ∼5 Jy s. The power-law index agrees well with that found for lower-energy pulses in the range 3–30 Jy ms. The fluence distribution of the Crab pulsar hence appears to follow a single power law over ∼3 orders of magnitude in fluence. We do not see any evidence for the flattening at high fluences reported by earlier studies. We also find that, at these fluence levels, the rate of giant-pulse emission varies by as much as a factor of ∼5 on time-scales of a few days, although the power-law index of the pulse-energy distribution remains unchanged. The slope of the fluence distribution for Crab giant pulses is similar to that recently determined for the repeating FRB 121102. We also find an anti-correlation between the pulse fluence and the pulse width, so that more energetic pulses are preferentially shorter.

scholarly journals Hinode magnetic-field observations of solar flares for exploring the energy storage and trigger mechanisms

2015 ◽  
Vol 11 (S320) ◽  
pp. 175-178
Author(s):  
Toshifumi Shimizu ◽  
Satoshi Inoue ◽  
Yusuke Kawabata
Keyword(s):  
Magnetic Field ◽  
Free Field ◽  
Coronal Magnetic Field ◽  
Field Configuration ◽  
Optical Telescope ◽  
Magnetic Field Data ◽  
Trigger Mechanisms ◽  
The Magnetic Field ◽  
Force Free Field ◽  
Chromospheric Flare

AbstractThe spectro-polarimeter in the Hinode Solar Optical Telescope (SOT) is one of the powerful instruments for the most accurate measurements of vector magnetic fields on the solar surface. The magnetic field configuration and possible candidates for flare trigger are briefly discussed with some SOT observations of solar flare events, which include X5.4/X1.3 flares on 7 March 2012, X1.2 flare on 7 January 2014 and two M-class flares on 2 February 2014. Especially, using an unique set of the Hinode and SDO data for the X5.4/X1.3 flares on 7 March 2012, we briefly reviewed remarkable properties observed in the spatial distribution of the photospheric magnetic flux, chromospheric flare ribbons, and the 3D coronal magnetic field structure inferred by non-linear force-free field modeling with the Hinode photospheric magnetic field data.

A Boubaker Polynomials Expansion Scheme for Solving the Flow of Nonlinear Power-Law Fluid in Semi-Solid State

2012 ◽  
Vol 192-193 ◽  
pp. 276-280
Author(s):  
Kai Kun Wang ◽  
Jin Long Fu ◽  
Xin Hui Si
Keyword(s):  
Solid State ◽  
Power Law ◽  
Analytic Solutions ◽  
Power Law Fluid ◽  
Boubaker Polynomials ◽  
Unsteady Stretching Surface ◽  
Semi Solid ◽  
Power Law Index ◽  
Good Agreement ◽  
Expansion Scheme

The problem of an uncompressible power-law fluid has long been the challenge in semi-solid forming area. In this paper, the flow of a power-law fluid film on an unsteady stretching surface is analyzed by the means of Boubaker Polynomials Expansion Scheme (BPES). Analytic solutions were given and compared with the numerical results for some real power-law index and the unsteadiness parameter in wide ranges. The good agreement between them showed BPES could be used effectively to solve the flow of nonlinear power-law fluid in semi-solid state.

scholarly journals A confined flare above filaments

2013 ◽  
Vol 8 (S300) ◽  
pp. 227-230
Author(s):  
K. Dalmasse ◽  
R. Chandra ◽  
B. Schmieder ◽  
G. Aulanier
Keyword(s):  
Free Field ◽  
High Resolution Data ◽  
Flare Loops ◽  
Multi Wavelength ◽  
Linear Force ◽  
Force Free Field ◽  
Flare Model ◽  
Class Flare ◽  
Opposite Chirality ◽  
Good Agreement

AbstractWe present the dynamics of two filaments and a C-class flare observed in NOAA 11589 on 2012 October 16. We used the multi-wavelength high-resolution data from SDO, as well as THEMIS and ARIES ground-based observations. The observations show that the filaments are progressively converging towards each other without merging. We find that the filaments have opposite chirality which may have prevented them from merging. On October 16, a C3.3 class flare occurred without the eruption of the filaments. According to the standard solar flare model, after the reconnection, post-flare loops form below the erupting filaments whether the eruption fails or not. However, the observations show the formation of post-flare loops above the filaments, which is not consistent with the standard flare model. We analyze the topology of the active region's magnetic field by computing the quasi-separatrix layers (QSLs) using a linear force-free field extrapolation. We find a good agreement between the photospheric footprints of the QSLs and the flare ribbons. We discuss how slipping or slip-running reconnection at the QSLs may explain the observed dynamics.

scholarly journals Evolution of relativistic thin discs with a finite ISCO stress – I. Stalled accretion

2019 ◽  
Vol 489 (1) ◽  
pp. 132-142 ◽  
Author(s):  
Andrew Mummery ◽  
Steven A Balbus
Keyword(s):  
Power Law ◽  
Extended Period ◽  
Companion Paper ◽  
Light Curves ◽  
Evolutionary Equation ◽  
Stable Circular Orbit ◽  
Innermost Stable Circular Orbit ◽  
Stress Models ◽  
Power Law Index ◽  
Good Agreement

ABSTRACT We present solutions to the relativistic thin disc evolutionary equation using an α-model for the turbulent stress tensor. Solutions with a finite stress at the innermost stable circular orbit (ISCO) give rise to bolometric light curves with a shallow power-law time dependence, in good agreement with those observed in tidal disruption events. A self-similar model based on electron scattering opacity, for example, yields a power-law index of −11/14, as opposed to −19/16 for the case of zero ISCO stress. These solutions correspond to an extended period of relaxation of the evolving disc which, like the light curves they produce, is not sustainable indefinitely. Cumulative departures from the approximation of exact circular orbits cause the power-law index to evolve slowly with time, leading eventually to the steeper fall-off associated with traditional zero ISCO stress models. These modified solutions are discussed in detail in a companion paper.

Elastic Foundation Analysis of Uniformly Loaded Functionally Graded Viscoelastic Sandwich Plates

2012 ◽  
Vol 28 (3) ◽  
pp. 439-452 ◽  
Author(s):  
A. M. Zenkour ◽  
M. Sobhy
Keyword(s):  
Power Law ◽  
Sandwich Plate ◽  
Plate Theory ◽  
Functionally Graded ◽  
Sandwich Plates ◽  
Equilibrium Equations ◽  
Graded Material ◽  
Plate Aspect Ratio ◽  
Type V ◽  
Power Law Index

AbstractThis paper deals with the static response of simply supported functionally graded material (FGM) viscoelastic sandwich plates subjected to transverse uniform loads. The FG sandwich plates are considered to be resting on Pasternak's elastic foundations. The sandwich plate is assumed to consist of a fully elastic core sandwiched by elastic-viscoelastic FGM layers. Material properties are graded according to a power-law variation from the interfaces to the faces of the plate. The equilibrium equations of the FG sandwich plate are given based on a trigonometric shear deformation plate theory. Using Illyushin's method, the governing equations of the viscoelastic sandwich plate can be solved. Parametric study on the bending analysis of FG sandwich plates is being investigated. These parameters include (i) power-law index, (ii) plate aspect ratio, (iii) side-to-thickness ratio, (iv) loading type, (v) foundation stiffnesses, and (vi) time parameter.

scholarly journals Jet Impingement Heat Transfer of Confined Single and Double Jets with Non-Newtonian Power Law Nanofluid under the Inclined Magnetic Field Effects for a Partly Curved Heated Wall

2021 ◽  
Vol 13 (9) ◽  
pp. 5086
Author(s):  
Fatih Selimefendigil ◽  
Hakan F. Oztop ◽  
Ali J. Chamkha
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Particle Size ◽  
Aspect Ratio ◽  
Power Law ◽  
Volume Fraction ◽  
Inclined Magnetic Field ◽  
Magnetic Field Effects ◽  
Power Law Nanofluid ◽  
Power Law Index

Single and double impinging jets heat transfer of non-Newtonian power law nanofluid on a partly curved surface under the inclined magnetic field effects is analyzed with finite element method. The numerical work is performed for various values of Reynolds number (Re, between 100 and 300), Hartmann number (Ha, between 0 and 10), magnetic field inclination (γ, between 0 and 90), curved wall aspect ratio (AR, between 01. and 1.2), power law index (n, between 0.8 and 1.2), nanoparticle volume fraction (ϕ, between 0 and 0.04) and particle size in nm (dp, between 20 and 80). The amount of rise in average Nusselt (Nu) number with Re number depends upon the power law index while the discrepancy between the Newtonian fluid case becomes higher with higher values of power law indices. As compared to case with n = 1, discrepancy in the average Nu number are obtained as −38% and 71.5% for cases with n = 0.8 and n = 1.2. The magnetic field strength and inclination can be used to control the size and number or vortices. As magnetic field is imposed at the higher strength, the average Nu reduces by about 26.6% and 7.5% for single and double jets with n greater than 1 while it increases by about 4.78% and 12.58% with n less than 1. The inclination of magnetic field also plays an important role on the amount of enhancement in the average Nu number for different n values. The aspect ratio of the curved wall affects the flow field slightly while the average Nu variation becomes 5%. Average Nu number increases with higher solid particle volume fraction and with smaller particle size. At the highest particle size, it is increased by about 14%. There is 7% variation in the average Nu number when cases with lowest and highest particle size are compared. Finally, convective heat transfer performance modeling with four inputs and one output is successfully obtained by using Adaptive Neuro-Fuzzy Interface System (ANFIS) which provides fast and accurate prediction results.

scholarly journals Blocks Size Frequency Distribution in the Enceladus Tiger Stripes Area: Implications on Their Formative Processes

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 82
Author(s):  
Maurizio Pajola ◽  
Alice Lucchetti ◽  
Lara Senter ◽  
Gabriele Cremonese
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Size Frequency Distribution ◽  
Surface Stresses ◽  
Size Frequency ◽  
The One ◽  
Power Law Index ◽  
Comet 67P ◽  
South Polar ◽  
Degree Of Fragmentation

We study the size frequency distribution of the blocks located in the deeply fractured, geologically active Enceladus South Polar Terrain with the aim to suggest their formative mechanisms. Through the Cassini ISS images, we identify ~17,000 blocks with sizes ranging from ~25 m to 366 m, and located at different distances from the Damascus, Baghdad and Cairo Sulci. On all counts and for both Damascus and Baghdad cases, the power-law fitting curve has an index that is similar to the one obtained on the deeply fractured, actively sublimating Hathor cliff on comet 67P/Churyumov-Gerasimenko, where several non-dislodged blocks are observed. This suggests that as for 67P, sublimation and surface stresses favor similar fractures development in the Enceladus icy matrix, hence resulting in comparable block disaggregation. A steeper power-law index for Cairo counts may suggest a higher degree of fragmentation, which could be the result of localized, stronger tectonic disruption of lithospheric ice. Eventually, we show that the smallest blocks identified are located from tens of m to 20–25 km from the Sulci fissures, while the largest blocks are found closer to the tiger stripes. This result supports the ejection hypothesis mechanism as the possible source of blocks.

scholarly journals Impact of autocatalytic chemical reaction in an Ostwald-de-Waele nanofluid flow past a rotating disk with heterogeneous catalysis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Bai Yu ◽  
Muhammad Ramzan ◽  
Saima Riasat ◽  
Seifedine Kadry ◽  
Yu-Ming Chu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Differential Equations ◽  
Chemical Reaction ◽  
Power Law ◽  
Variable Thickness ◽  
Rotating Disk ◽  
Thermal Profile ◽  
Nanofluid Flow ◽  
Power Law Index

AbstractThe nanofluids owing to their alluring attributes like enhanced thermal conductivity and better heat transfer characteristics have a vast variety of applications ranging from space technology to nuclear reactors etc. The present study highlights the Ostwald-de-Waele nanofluid flow past a rotating disk of variable thickness in a porous medium with a melting heat transfer phenomenon. The surface catalyzed reaction is added to the homogeneous-heterogeneous reaction that triggers the rate of the chemical reaction. The added feature of the variable thermal conductivity and the viscosity instead of their constant values also boosts the novelty of the undertaken problem. The modeled problem is erected in the form of a system of partial differential equations. Engaging similarity transformation, the set of ordinary differential equations are obtained. The coupled equations are numerically solved by using the bvp4c built-in MATLAB function. The drag coefficient and Nusselt number are plotted for arising parameters. The results revealed that increasing surface catalyzed parameter causes a decline in thermal profile more efficiently. Further, the power-law index is more influential than the variable thickness disk index. The numerical results show that variations in dimensionless thickness coefficient do not make any effect. However, increasing power-law index causing an upsurge in radial, axial, tangential, velocities, and thermal profile.

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