Energy Buildup Research Articles

Explosive Baroclinic Instability

Abstract A low-order general circulation model contains all the elements of baroclinic instability, including differential heating to drive the mean zonal shear flow against dissipation. Simulations exhibit vacillation ending in fixed-point solutions and chaotic solutions with significant amplifications of the baroclinic cycles compared to those of vacillation. The chaos sensitivity to initial conditions, covering a broad landscape of initial values, demands analysis of why the chaos occurs and its impact on subsequent storm intensity. Three attractors found in the dynamic system are important. One attractor is the stable fixed-point solution—the ultimate destination of a vacillation trajectory. A second attractor represents an unstable zonal solution. Though this dynamic system is bound, some trajectories get extremely close to the unstable, but strongly attracting, zonal solution. It is while traversing such a trajectory that the buildup of available potential energy is such to allow subsequent explosive baroclinic instability to develop. The roots of the characteristic matrix of the dynamic system are examined at every time step. A single critical value of one of the roots is found to be the cause of the chaos for a given value of the differential heating H. The system becomes more stable with increased values of H; vacillation is stronger and more prominent, and the critical value for chaos increases with H. When chaos does occur, it is stronger and more explosive.

WE-E-18A-05: Bremsstrahlung of Laser-Plasma Interaction at KeV Temperature: Forward Dose and Attenuation Factors

Purpose: To obtain an analytical empirical formula for the photon dose source term in forward direction from bremsstrahlung generated from laser-plasma accelerated electron beams in aluminum solid targets, with electron-plasma temperatures in the 10–100 keV energy range, and to calculate transmission factors for iron, aluminum, methacrylate, lead and concrete and air, materials most commonly found in vacuum chamber labs. Methods: Bremsstrahlung fluence is calculated from the convolution of thin-target bremsstrahlung spectrum for monoenergetic electrons and the relativistic Maxwell-Juettner energy distribution for the electron-plasma. Unattenuatted dose in tissue is calculated by integrating the photon spectrum with the mass-energy absorption coefficient. For the attenuated dose, energy dependent absorption coefficient, build-up factors and finite shielding correction factors were also taken into account. For the source term we use a modified formula from Hayashi et al., and we fitted the proportionality constant from experiments with the aid of the previously calculated transmission factors. Results: The forward dose has a quadratic dependence on electron-plasma temperature: 1 joule of effective laser energy transferred to the electrons at 1 m in vacuum yields 0,72 Sv per MeV squared of electron-plasma temperature. Air strongly filters the softer part of the photon spectrum and reduce the dose to one tenth in the first centimeter. Exponential higher energy tail of maxwellian spectrum contributes mainly to the transmitted dose. Conclusion: A simple formula for forward photon dose from keV range temperature plasma is obtained, similar to those found in kilovoltage x-rays but with higher dose per dissipated electron energy, due to thin target and absence of filtration.

WE-E-18A-06: To Remove Or Not to Remove: Comfort Pads From Beneath Neonates for Radiography

Purpose: To obtain an analytical empirical formula for the photon dose source term in forward direction from bremsstrahlung generated from laser-plasma accelerated electron beams in aluminum solid targets, with electron-plasma temperatures in the 10–100 keV energy range, and to calculate transmission factors for iron, aluminum, methacrylate, lead and concrete and air, materials most commonly found in vacuum chamber labs. Methods: Bremsstrahlung fluence is calculated from the convolution of thin-target bremsstrahlung spectrum for monoenergetic electrons and the relativistic Maxwell-Juettner energy distribution for the electron-plasma. Unattenuatted dose in tissue is calculated by integrating the photon spectrum with the mass-energy absorption coefficient. For the attenuated dose, energy dependent absorption coefficient, build-up factors and finite shielding correction factors were also taken into account. For the source term we use a modified formula from Hayashi et al., and we fitted the proportionality constant from experiments with the aid of the previously calculated transmission factors. Results: The forward dose has a quadratic dependence on electron-plasma temperature: 1 joule of effective laser energy transferred to the electrons at 1 m in vacuum yields 0,72 Sv per MeV squared of electron-plasma temperature. Air strongly filters the softer part of the photon spectrum and reduce the dose to one tenth in the first centimeter. Exponential higher energy tail of maxwellian spectrum contributes mainly to the transmitted dose. Conclusion: A simple formula for forward photon dose from keV range temperature plasma is obtained, similar to those found in kilovoltage x-rays but with higher dose per dissipated electron energy, due to thin target and absence of filtration.

Centrifuge-assisted micromolding of ceramic microparts

A novel method with the combined technology of soft lithography and centrifugal casting was developed to fabricate ceramic microparts. A well-dispersed aqueous alumina suspension suitable for micromolding was prepared. The suspension was filled into microstructured polydimethylsiloxane molds followed by consolidation under centrifugal force. Compared with the micromolding under gravity, denser particle packing was achieved for the green microparts under centrifugal force. The centrifugal force enhanced sedimentation of the alumina particles at a short time and thus the green density was significantly improved. A flexible polyethylene film was used as the substrate to prevent crack formation during drying, which allowed unconstraint shrinkage and reduced the buildup of strain energy. After sintering, the linear shrinkages of the microparts under centrifugal force were lower than those under gravity. The microparts under centrifugal force were fully densified and had good shape retention. The novel method, called centrifuge-assisted micromolding, has been demonstrated by the fabrication of the alumina microchannel part.

Internal energy distribution in electrospray ionization: towards the evaluation of a thermal-like distribution from the multiple-collision model.

The internal energy deposition in ions that cross the desolvation region of an electrospray ionization (ESI) source affects the mass spectra that are obtained using in-source collision-induced dissociation (CID) or in tandem mass spectrometry (MS/MS) mode. It is thus important to evaluate the internal energy distributions of the ions in different parts of an ESI mass spectrometer. The desolvation region is considered as a collision zone and a partially elastic multiple-collision model is used to account for the accumulation of internal energy in the ions. The ion survival yields (SY(Theo) of the theoretical mass spectra calculated by MassKinetics software are fitted with the experimental ion survival yields (SY(Exp)) of the substituted benzylpyridinium cations that have been obtained with an ESI source interfaced with a quadrupole mass spectrometer. The theoretical parameters used for fitting the calculation data with the experimental results are the center-of-mass collision energy (Ecom ) of the colliding ions and a term related to the pressure of the desolvation area of the ESI interface. In the proposed model, an average number of 'effective' collisions of close to 30 in the desolvation area is employed. The voltages applied to the orifice of this interface are correlated to a theoretical initial kinetic energy (E(init,Kin)) in the laboratory frame of the ions. In the present case, these theoretical initial kinetic energies range from 5.5 to 9 eV. The internal energy distributions evaluated from this model resemble the thermal distributions of ions having 'characteristic temperatures' between 1020 and 1550 K, and the results of calculations show that the mean internal energy of the ions increases linearly with the orifice voltage. The model used in this study can account for the energy build-up of the ions in an ESI interface and allows the change in the internal energy distribution of the electrosprayed ions in different regions of a mass spectrometer to be evaluated.

Monte Carlo study of secondary electron production from gold nanoparticle in proton beam irradiation

Purpose: In this study, we examined some characteristics of secondary electrons produced by gold nanoparticle (NP) during proton beam irradiation. Method: By using the Geant4 Monte Carlo simulation toolkit, we simulated the NP at the range from radius (r) of 17.5 nm, 25 nm, 35 nm to r = 50 nm. The proton beam energies used were 20MeV, 50MeV, and 100MeV. Findings on secondary electron production and their average kinetic energy are presented in this paper. Results: Firstly, for NP with a finite size, the secondary electron production increase with decreasing incident proton beam energy and secondary buildup existed outside NP. Secondly, the average kinetic energy of secondary electrons produced by a gold NP increased with incident proton beam energy. Thirdly, the larger the NP size, the more the secondary electron production. Conclusion: Collectively, our results suggest that apart from biological uptake efficiency, we should take the secondary electron production effect into account when considering the potential use of NPs in proton beam irradiation. ----------------------------------------------- Cite this article as : Gao J, Zheng Y. Monte Carlo study of secondary electron production from gold nanoparticle in proton beam irradiation. Int J Cancer Ther Oncol 2014; 2 (2):02025. DOI: http://dx.doi.org/10.14319/ijcto.0202.5

Mesoscale and macroscale kinetic energy fluxes from granular fabric evolution.

Recent advances in high-resolution measurements means it is now possible to identify and track the local "fabric" or contact topology of individual grains in a deforming sand throughout loading history. These provide compelling impetus to the development of methods for inferring changes in the contact forces and energies at multiple spatiotemporal scales, using information on grain contacts alone. Here we develop a surrogate measure of the fluctuating kinetic energy based on changes in the local contact topology of individual grains. We demonstrate the method for dense granular materials under quasistatic biaxial shear. In these systems, the initially stable and solidlike response eventually gives way to liquidlike behavior and global failure. This crossover in mechanical behavior, akin to a phase transition, is marked by bursts of kinetic energy and frictional dissipation. Mechanisms underlying this release of energy include the buckling of major load-bearing structures known as force chains. These columns of grains represent major repositories for stored strain energy. Stored energy initially accumulates at all of the contacts along the force chain, but is released collectively when the chain overloads and buckles. The exact quantification of the buildup and release of energy in force chains, and the manner in which force chain buckling propagates in the sample (i.e., diffuse and systemwide versus localized into shear bands), requires detailed knowledge of contact forces. To date, however, the forces at grain contacts continue to elude measurement in natural granular materials like sand. Here, using data from computer simulations, we show that a proxy for the fluctuating kinetic energy in dense granular materials can be suitably constructed solely from the evolving properties of the grain's local contact topology. Our approach directly relates the evolution of fabric to energy flux and makes possible research into the propagation of failure from measurements of grain contacts in real granular materials.

Partial energy stack section for qualitative subsurface velocity estimation

Abstract We suggest a fast method to extract basic subsurface velocity information from seismic data. The method uses the energy buildup of time traces. The stacked and arranged energy buildup signals can give us rough information of subsurface velocity structures. This method can be used with seismic data acquired on the subsurface with large contrasts of the acoustic impedance such as salt areas. The section of stacked partial energy can complement the near-offset gather by adding the qualitative velocity information to the subsurface image. The section itself is not a velocity model; however, we can use it to find structures with large velocity or density contrast before we start standard seismic processes. Numerical examples using the SEG/EAGE salt velocity model, BP benchmark model, Pluto model, and a field dataset from Gulf of Mexico demonstrate that the method can be used to obtain rough subsurface velocity information quickly.

DEM Study on Energy Allocation Behavior in Crushable Soils

Detailed knowledge of particle-scale energy allocation behavior under the influence of particle breakage is of fundamental importance to the development of micromechanics-based constitutive models of sands. This paper reports original results of the energy input/dissipation of an idealized crushable soil using 3D DEM simulations. Particle breakage is modeled as the disintegration of synthetic agglomerate particles which are made up of parallel-bonded elementary spheres. Simulation results show that the initial specimen density and crushability strongly affect the energy allocation of the soil both at small and large strains. The major role of particle breakage, which itself only dissipates a negligible amount of input energy, is found to advance the soil fabric change and promote the interparticle friction dissipation. Particularly, at small strains, particle breakage disrupts the strain energy buildup and thus reduces the mobilized shear strength and dilatancy of a granular soil. At large strains where particle breakage is greatly reduced, a steady energy dissipation by interparticle friction and mechanical damping is observed. Furthermore, it is found that shear bands develop in most dense crushable specimens at large strains, but they are only weakly correlated to the anisotropy of the accumulated friction dissipation.

Correspondence on Microwave Effects in Organic Synthesis

Angewandte Chemie recently published an unusual Essay by Prof. C. Oliver Kappe and co-workers entitled, “Microwave Effects in Organic Synthesis—Myth or Reality?” The major point of discussion is an Edge Article we published last year in the RSC journal Chemical Science entitled, “On the Rational Design of Microwave-Actuated Organic Reactions.” The Angewandte Essay is unusual in its inclusion of 38 pages of experimental details in the Supporting Information, 30 of which describe unpublished data from original experiments pertaining to our work. These data are interpreted as conflicting with our report. We reject their alternative interpretations of our experiments, and we discuss here how the new data from their experiments in fact align with our conclusions. In our article, we provided an example of a microwave (MW)-actuated reaction system, which we define as one for which MW irradiation provides a synthetic advantage over conventional heating at the same temperature. We designed an extreme reaction system—an ionic benzyl-transfer reagent in a nonpolar aromatic solvent—and subjected it to extreme conditions: constant MW irradiation at high power (300 W). Our design of this chemical system was predicated on the concept of selective heat storage in the domains existing around microwave-absorbing solutes in nonabsorbing media at fixed (and typically high) applied microwave powers. The design rationale aligns with an understanding of selective microwave heating obtained from fundamental dielectric relaxation studies carried out by Richert and Huang. In such a system, the selective absorption of microwave energy by the solute will result in localized energy in the solvation domain (i.e. effective temperature) that is higher than the surrounding medium. The solute then acts as a molecular radiator, transferring thermal energy to the bulk solution. If convective heat transfer out of the domains is slow compared to the build-up of thermal energy within the solute domains, then the thermal energy of the solute will exceed what would be predicted based on the measured temperature of the bulk solution. As an extension of that work, one can hypothesize that a microwave-absorbing reactant in a nonabsorbing medium can potentially realize product formation at rates in excess of what would be expected from conventional heating at the same measured bulk temperature. Indeed, we observed reactivity enhancements under MW heating compared to conventional oil-bath heating in a benzylation of [D10]pxylene (Figure 1).

THE STORAGE AND DISSIPATION OF MAGNETIC ENERGY IN THE QUIET SUN CORONA DETERMINED FROM SDO /HMI MAGNETOGRAMS

In recent years, higher cadence, higher resolution observations have revealed the quiet-Sun photosphere to be complex and rapidly evolving. Since magnetic fields anchored in the photosphere extend up into the solar corona, it is expected that the small-scale coronal magnetic field exhibits similar complexity. For the first time, the quiet-Sun coronal magnetic field is continuously evolved through a series of non-potential, quasi-static equilibria, deduced from magnetograms observed by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory, where the photospheric boundary condition which drives the coronal evolution exactly reproduces the observed magnetograms. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. We find that the free magnetic energy built up and stored within the field is sufficient to explain small-scale, impulsive events such as nanoflares. On comparing with coronal images of the same region, the energy storage and dissipation visually reproduces many of the observed features. The results indicate that the complex small-scale magnetic evolution of a large number of magnetic features is a key element in explaining the nature of the solar corona.

Comparative study of diode-pumping self-injection and injection-locking Tm:YAG lasers

A comparative study of the laser characteristics of self-injection and injection-locking Tm:YAG lasers is given in this paper. At a pump energy of 145 mJ and Q-switched repetition rate of 100 Hz, an output energy of 2.39 mJ was obtained for an injection-locking Tm:YAG laser, with a pulse width of 403.2 ns and a pulse building-up time of 2.12 μs. Under the same conditions, the output energy, pulse width and pulse build-up time for a self-injection Tm:YAG laser were 2.21 mJ, 407.0 ns and 3.95 μs, respectively. The threshold of the Q-switched injection-locking Tm:YAG laser was much lower than that of the self-injection laser, and the pulse width was narrower and the pulse build-up time shorter. Additionally, the output spectrum was much purer for the injection-locking laser.

Record-breaking avalanches in driven threshold systems

Record-breaking avalanches generated by the dynamics of several driven nonlinear threshold models are studied. Such systems are characterized by intermittent behavior, where a slow buildup of energy is punctuated by an abrupt release of energy through avalanche events, which usually follow scale-invariant statistics. From the simulations of these systems it is possible to extract sequences of record-breaking avalanches, where each subsequent record-breaking event is larger in magnitude than all previous events. In the present work, several cellular automata are analyzed, among them the sandpile model, the Manna model, the Olami-Feder-Christensen (OFC) model, and the forest-fire model to investigate the record-breaking statistics of model avalanches that exhibit temporal and spatial correlations. Several statistical measures of record-breaking events are derived analytically and confirmed through numerical simulations. The statistics of record-breaking avalanches for the four models are compared to those of record-breaking events extracted from the sequences of independent and identically distributed (i.i.d.) random variables. It is found that the statistics of record-breaking avalanches for the above cellular automata exhibit behavior different from that observed for i.i.d. random variables, which in turn can be used to characterize complex spatiotemporal dynamics. The most pronounced deviations are observed in the case of the OFC model with a strong dependence on the conservation parameter of the model. This indicates that avalanches in the OFC model are not independent and exhibit spatiotemporal correlations.

Simulation of homogeneous turbulent shear flows at higher Reynolds numbers: numerical challenges and a remedy

In a recent study, Isaza and Collins [J. Fluid Mech., 637 (2009), pp. 213–239] found the asymptotic state of homogeneous turbulent shear flows (HTSFs) to be sensitively dependent on the initial shear parameter (), and yet be almost independent of the initial Reynolds number (R λ≡qλ/ν). The stringent resolution criteria they employed, however, restricted their studies to relatively low Reynolds numbers. In this paper, we present higher resolution direct numerical simulations of HTSFs over a wider range of Reynolds numbers, aided in part by an improved parallelisation scheme that utilises two-dimensional domain decomposition. We maximise the time-window for our simulations by determining appropriate settings for the initial energy spectrum, viscosity and domain configuration, thereby ensuring that we attain the highest possible asymptotic Reynolds number at the chosen grid resolution. In the course of our study, we find that the pseudo-spectral method suffers from Gibbs oscillations while resolving the thin vortical structures that tend to form in HTSFs. The nonlinear growth of these oscillations leads to spurious energy buildup in the high-wavenumber region of the spectrum, and contaminates the flow field. Consequently, the growth of the integral length scale is found to be numerically stunted, well before the intended final Reynolds number is attained. The issue is rectified by the application of exponential-type spectral filters, which stabilise the simulations and extend the runtime window, permitting attainment of larger asymptotic Reynolds numbers. Various large-scale flow statistics are then studied, and their dependence on the initial value of the shear parameter and Reynolds number corroborates the findings of Isaza and Collins.

Coronal Magnetic Field Evolution from 1996 to 2012: Continuous Non-potential Simulations

Coupled flux transport and magneto-frictional simulations are extended to simulate the continuous magnetic-field evolution in the global solar corona for over 15 years, from the start of Solar Cycle 23 in 1996. By simplifying the dynamics, our model follows the build-up and transport of electric currents and free magnetic energy in the corona, offering an insight into the magnetic structure and topology that extrapolation-based models cannot. To enable these extended simulations, we have implemented a more efficient numerical grid, and have carefully calibrated the surface flux-transport model to reproduce the observed large-scale photospheric radial magnetic field, using emerging active regions determined from observed line-of-sight magnetograms. This calibration is described in some detail. In agreement with previous authors, we find that the standard flux-transport model is insufficient to simultaneously reproduce the observed polar fields and butterfly diagram during Cycle 23, and that additional effects must be added. For the best-fit model, we use automated techniques to detect the latitude–time profile of flux ropes and their ejections over the full solar cycle. Overall, flux ropes are more prevalent outside of active latitudes but those at active latitudes are more frequently ejected. Future possibilities for space-weather prediction with this approach are briefly assessed.

Rotating horizontal convection

Abstract‘Horizontal convection’ (HC) is the generic name for the flow resulting from a buoyancy variation imposed along a horizontal boundary of a fluid. We study the effects of rotation on three-dimensional HC numerically in two stages: first, when baroclinic instability is suppressed and, second, when it ensues and baroclinic eddies are formed. We concentrate on changes to the thickness of the near-surface boundary layer, the stratification at depth, the overturning circulation and the flow energetics during each of these stages. Our results show that, for moderate flux Rayleigh numbers ($O(1{0}^{11} )$), rapid rotation greatly alters the steady-state solution of HC. When the flow is constrained to be uniform in the transverse direction, rapidly rotating solutions do not support a boundary layer, exhibit weaker overturning circulation and greater stratification at all depths. In this case, diffusion is the dominant mechanism for lateral buoyancy flux and the consequent buildup of available potential energy leads to baroclinically unstable solutions. When these rapidly rotating flows are perturbed, baroclinic instability develops and baroclinic eddies dominate both the lateral and vertical buoyancy fluxes. The resulting statistically steady solution supports a boundary layer, larger values of deep stratification and multiple overturning cells compared with non-rotating HC. A transformed Eulerian-mean approach shows that the residual circulation is dominated by the quasi-geostrophic eddy streamfunction and that the eddy buoyancy flux has a non-negligible interior diabatic component. The kinetic and available potential energies are greater than in the non-rotating case and the mixing efficiency drops from${\sim }0. 7$to${\sim }0. 17$. The eddies play an important role in the formation of the thermal boundary layer and, together with the negatively buoyant plume, help establish deep stratification. These baroclinically active solutions have characteristics of geostrophic turbulence.

Solar Magnetic Carpet III: Coronal Modelling of Synthetic Magnetograms

This article is the third in a series working towards the construction of a realistic, evolving, non-linear force-free coronal-field model for the solar magnetic carpet. Here, we present preliminary results of 3D time-dependent simulations of the small-scale coronal field of the magnetic carpet. Four simulations are considered, each with the same evolving photospheric boundary condition: a 48-hour time series of synthetic magnetograms produced from the model of Meyer et al. (Solar Phys. 272, 29, 2011). Three simulations include a uniform, overlying coronal magnetic field of differing strength, the fourth simulation includes no overlying field. The build-up, storage, and dissipation of magnetic energy within the simulations is studied. In particular, we study their dependence upon the evolution of the photospheric magnetic field and the strength of the overlying coronal field. We also consider where energy is stored and dissipated within the coronal field. The free magnetic energy built up is found to be more than sufficient to power small-scale, transient phenomena such as nanoflares and X-ray bright points, with the bulk of the free energy found to be stored low down, between 0.5 – 0.8 Mm. The energy dissipated is currently found to be too small to account for the heating of the entire quiet-Sun corona. However, the form and location of energy-dissipation regions qualitatively agree with what is observed on small scales on the Sun. Future MHD modelling using the same synthetic magnetograms may lead to a higher energy release.

Explicit filtering to obtain grid-spacing-independent and discretization-order-independent large-eddy simulation of two-phase volumetrically dilute flow with evaporation

AbstractPredictions from conventional large-eddy simulation (LES) are known to be grid-spacing and spatial-discretization-order dependent. In a previous article (Radhakrishnan & Bellan,J. Fluid Mech., vol. 697, 2012a, pp. 399–435), we reformulated LES for compressible single-phase flow by explicitly filtering the nonlinear terms in the governing equations so as to render the solution grid-spacing and discretization-order independent. Having shown in Radhakrishnan & Bellan (2012a) that the reformulated LES, which we call EFLES, yields grid-spacing-independent and discretization-order-independent solutions for compressible single-phase flow, we explore here the potential of EFLES for evaporating two-phase flow where the small scales have an additional origin compared to single-phase flow. Thus, we created a database through direct numerical simulation (DNS) that when filtered serves as a template for comparisons with both conventional LES and EFLES. Both conventional LES and EFLES are conducted with two gas-phase SGS models; the drop-field SGS model is the same in all these simulations. For EFLES, we also compared simulations performed with the same SGS model for the gas phase but two different drop-field SGS models. Moreover, to elucidate the influence of explicit filtering versus gas-phase SGS modelling, EFLES with two drop-field SGS models but no gas-phase SGS models were conducted. The results from all these simulations were compared to those from DNS and from the filtered DNS (FDNS). Similar to the single-phase flow findings, the conventional LES method yields solutions which are both grid-spacing and spatial-discretization-order dependent. The EFLES solutions are found to be grid-spacing independent for sufficiently large filter-width to grid-spacing ratio, although for the highest discretization order this ratio is larger in the two-phase flow compared to the single-phase flow. For a sufficiently fine grid, the results are also discretization-order independent. The absence of a gas-phase SGS model leads to build-up of energy near the filter cut-off indicating that while explicit filtering removes energy above the filter width, it does not provide the correct dissipation at the scales smaller than this width. A wider viewpoint leads to the conclusion that although the minimum filter-width to grid-spacing ratio necessary to obtain the unique grid-independent solution might be different for various discretization-order schemes, the grid-independent solution thus obtained is also discretization-order independent.

Spinoff Challenges for Computational Fluid Dynamics

This paper describes extensions of computational fluid dynamics (CFD) to fields of analysis lying well beyond their current realms of application. In particular, three examples are presented. The first is to the collective behavior of mobs of people interacting with sources of danger and/or opportunity to which each individual responds by actions that depend strongly on the inducement of fear and/or excitement, depending on the intrinsic susceptibilities of the person. This behavior results in both individual activities (agent-based) and collective behaviors (crowd-based stochastic) with consequences of potentially great significance. Extensions are also described for which various other emotional developments are important to the behavior of a mob. The second example is to the processes of biological evolution, in particular to the driving forces that influence the directions of species alterations through a succession of characteristics that are tested for survivability in classical Darwinian fashion. The key to the analysis lies in the newly emerging field of epigenetics, in which numerous important experimental studies are producing astonishing results leading to major challenges to the creation of computational models of the collective fluid-like dynamics of interacting biological species. The third example explores an alternative to the Big Bang theory for describing the origin of our universe. The idea is that a parent universe exists, being composed of energy, matter, and antimatter in various forms. In some region a perturbation occurs, which locally has an excess of matter over antimatter. An enormous gravitational buildup of matter and energy in the region leads to a black hole, in which there is distortion in the fourth dimension. The result then leads to an offspring entity (universe) that becomes completely detached from the parent. To apply computational fluid dynamics to the analysis of this process requires formulations that include a major component of relevant physical representations. In all three of these examples, instabilities, fluctuations, and turbulence play major roles. These arise naturally in agent-based numerical formulations (the first and second of our examples), but are much more challenging to describe in a stochastic representation (e.g., the Navier–Stokes equations). Some promising spectral analysis extensions for stochastic formulations are included in this paper.

THE MECHANISMS FOR THE ONSET AND EXPLOSIVE ERUPTION OF CORONAL MASS EJECTIONS AND ERUPTIVE FLARES

We have investigated the onset and acceleration of coronal mass ejections (CMEs) and eruptive flares. To isolate the eruption physics, our study uses the breakout model, which is insensitive to the energy buildup process leading to the eruption. We performed 2.5D simulations with adaptive mesh refinement that achieved the highest overall spatial resolution to date in a CME/eruptive flare simulation. The ultra-high resolution allows us to separate clearly the timing of the various phases of the eruption. Using new computational tools, we have determined the number and evolution of all X- and O-type nulls in the system, thereby tracking both the progress and the products of reconnection throughout the computational domain. Our results show definitively that CME onset is due to the start of fast reconnection at the breakout current sheet. Once this reconnection begins, eruption is inevitable; if this is the only reconnection in the system, however, the eruption will be slow. The explosive CME acceleration is triggered by fast reconnection at the flare current sheet. Our results indicate that the explosive eruption is caused by a resistive instability, not an ideal process. Moreover, both breakout and flare reconnections begin first as a form of weak tearing characterized by a slowly evolving plasmoids, but eventually transition to a fast form with well-defined Alfvenic reconnection jets and rapid flux transfer. This transition to fast reconnection is required for both CME onset and explosive acceleration. We discuss the key implications of our results for CME/flare observations and for theories of magnetic reconnection.