# Paul CharbonneauUniversité de Montréal | UdeM · Department of Physics

Paul Charbonneau

PhD

## About

247

Publications

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Introduction

Additional affiliations

June 2002 - present

October 1991 - April 2002

## Publications

Publications (247)

Objective. In diffusing alpha-emitters radiation therapy (‘Alpha DaRT’), the diffusion-leakage (DL) model is used to determine the spatial distributions of the emitters and the corresponding alpha dose, critical for a successful treatment. This work first introduces a finite volume (FV) approach to develop numerical schemes to simulate the DL model...

Hot Jupiter atmospheres are possibly subject to a thermoresistive instability. Such an instability may develop as the ohmic heating increases the electrical conductivity in a positive feedback loop, which ultimately leads to a runaway of the atmospheric temperature. We extend our previous axisymmetric one-dimensional radial model, by representing t...

Diffusion plays an important role in a wide variety of phenomena, from bacterial quorum sensing to the dynamics of traffic flow. While it generally tends to level out gradients and inhomogeneities, diffusion has nonetheless been shown to promote pattern formation in certain classes of systems. Formation of stable structures often serves as a key fa...

Diffusion plays an important role in a wide variety of phenomena, from bacterial quorum sensing to the dynamics of traffic flow. While it generally tends to level out gradients and inhomogeneities, diffusion has nonetheless been shown to promote pattern formation in certain classes of systems. Formation of stable structures often serves as a key fa...

Self-organized critical avalanche models are a class of cellular automata that, despite their simplicity, can be applied to the modeling of solar (and stellar) flares and generate robust power-law distributions in event size measures. However, bridging the conceptual gap to both magnetohydrodynamics and real flare observations continues to prove ch...

The physical origin of centennial and millennial-scale variations in solar activity remains ill-understood. Although stochastic fluctuations of the solar dynamo are unavoidable in view of the turbulent nature of the solar convection zone, the quasiperiodic long timescale modulations revealed by the cosmogenic radioisotope records are suggestive of...

Hot Jupiter atmospheres may be subject to a thermoresistive instability where an increase in the electrical conductivity due to ohmic heating results in runaway of the atmospheric temperature. We introduce a simplified one-dimensional model of the equatorial substellar region of a hot Jupiter that includes the temperature dependence and time depend...

Hot jupiter atmospheres may be subject to a thermo-resistive instability where an increase in the electrical conductivity due to ohmic heating results in runaway of the atmospheric temperature. We introduce a simplified one-dimensional model of the equatorial sub-stellar region of a hot jupiter which includes the temperature-dependence and time-dep...

In this paper, written as a general historical and technical introduction to the various contributions of the collection “Solar and Stellar Dynamo: A New Era”, we review the evolution and current state of dynamo theory and modelling, with emphasis on the solar dynamo. Starting with a historical survey, we then focus on a set of “tension points” tha...

In this paper, written as a general historical and technical introduction to the various review papers collected in the special issue ``Solar and Stellar Dynamo: A New Era'', we review the evolution and current state of dynamo theory and modelling, with emphasis on the solar dynamo. Starting with a historical survey, we then focus on a set of ``ten...

Solaris is a transformative Solar Polar Discovery-class mission concept to address crucial outstanding questions that can only be answered from a polar vantage. Solaris will image the Sun's poles from ~75 degree latitude, providing new insight into the workings of the solar dynamo and the solar cycle, which are at the foundation of our understandin...

The atmosphere of a hot Jupiter may be subject to a thermoresistive instability, in which the increasing electrical conductivity with temperature leads to runaway ohmic heating. We introduce a simplified model of the local dynamics in the equatorial region of a hot Jupiter that incorporates the back reaction on the atmospheric flow as the increasin...

The prediction of solar flares is still a significant challenge in space weather research, with no techniques currently capable of producing reliable forecasts performing significantly better than climatology methods. In this article, we present a flare forecasting technique using data assimilation coupled with computationally inexpensive cellular...

The atmosphere of a hot jupiter may be subject to a thermo-resistive instability, in which the increasing electrical conductivity with temperature leads to runaway Ohmic heating. We introduce a simplified model of the local dynamics in the equatorial region of a hot jupiter that incorporates the back reaction on the atmospheric flow as the increasi...

The prediction of solar flares is still a significant challenge in space weather research, with no techniques currently capable of producing reliable forecasts performing significantly above climatology. In this paper, we present a flare forecasting technique using data assimilation coupled with computationally inexpensive cellular automata called...

In this paper I examine whether external forcing of the solar dynamo on long timescales can produce detectable signal in the form of long term modulation of the magnetic cycle. This task is motivated in part by some recent proposals (Abreu et al., 2012; Astron. Ap., 548, A88; Stefani et al., 2021; Solar Phys., 296, 88), whereby modulation of the so...

One of the leading theories for the origin of life includes the hypothesis according to which life would have evolved as cooperative networks of molecules. Explaining cooperation$-$and particularly, its emergence in favoring the evolution of life-bearing molecules$-$is thus a key element in describing the transition from nonlife to life. Using agen...

One of the leading theories for the origin of life includes the hypothesis according to which life would have evolved as cooperative networks of molecules. Explaining cooperation—and particularly, its emergence in favoring the evolution of life-bearing molecules—is thus a key element in describing the transition from nonlife to life. Using agent-ba...

We use the anelastic spherical harmonic code to model the convective dynamo of solar-type stars. Based on a series of 15 3D MHD simulations spanning four bins in rotation and mass, we show what mechanisms are at work in these stellar dynamos with and without magnetic cycles and how global stellar parameters affect the outcome. We also derive scalin...

We use the ASH code to model the convective dynamo of solar-type stars. Based on a series of 15 3-D MHD simulations spanning 4 bins in rotation and mass, we show what mechanisms are at work in these stellar dynamos with and without magnetic cycles and how global stellar parameters affect the outcome. We also derive scaling laws for the differential...

This paper reviews recent advances and current debates in modeling the solar cycle as a hydromagnetic dynamo process. Emphasis is placed on (relatively) simple dynamo models that are nonetheless detailed enough to be comparable to solar cycle observations. After a brief overview of the dynamo problem and of key observational constraints, I begin by...

Coverage of plasma motions is limited to the line-of-sight component at the Sun's surface. Multiple tracking and inversion methods were developed to infer the transverse motions from observational data. Recently, the DeepVel neural network was trained with computations performed by numerical simulations of the solar photosphere to recover the missi...

div class="abstract">
We examine the impact of surface inflows into activity belts on the operation of solar cycle models based on the Babcock-Leighton mechanism of poloidal field regeneration. Towards this end we introduce in the solar cycle model of Lemerle \& Charbonneau (2017, ApJ 834, 133) a magnetic flux-dependent variation of the surface m...

An algebraic method for the reconstruction and potentially prediction of the solar dipole moment value at sunspot minimum (known to be a good predictor of the amplitude of the next solar cycle) was suggested in the first paper in this series. The method sums up the ultimate dipole moment contributions of individual active regions in a solar cycle:...

We present a non-kinematic axisymetric $\alpha^2\Omega$ mean-field dynamo model in which the complete $\alpha$-tensor and mean differential rotation profile are both extracted from a global magnetohydrodynamical simulation of solar convection producing cycling large-scale magnetic fields. The nonlinear backreaction of the Lorentz force on different...

An algebraic method for the reconstruction and potentially prediction of the solar dipole moment value at sunspot minimum (known to be a good predictor of the amplitude of the next solar cycle) was suggested in the first paper in this series. The method sums up the ultimate dipole moment contributions of individual active regions in a solar cycle:...

Heliophysics is the system science of the physical connections between the Sun and the solar system. As the physics of the local cosmos, it embraces space weather and planetary habitability. The wider view of comparative heliophysics forms a template for conditions in exoplanetary systems and provides a view over time of the aging Sun and its magne...

The solar dipole moment at activity minimum is a good predictor of the strength of the subsequent solar cycle. Through a systematic analysis using a state-of-the-art 2$\times$2 D solar dynamo model, we found that bipolar magnetic regions (BMR) with atypical characteristics can modify the strength of the next cycle via their impact on the buildup of...

Reconstructions of past solar activity based on cosmogenic radioisotopes have reavealed that the Sun spends a significant fraction (\({\approx}\, 20\)%) of its time in aperiodically recurring states of so-called Grand Minima or Grand Maxima, namely epochs of strongly supressed and markedly above-average levels of magnetic activity, respectively. Th...

We present a data-driven version of the solar cycle model of Lemerle and Charbonneau (Astrophys. J.
834, 133; 2017), which we use to forecast properties of the upcoming sunspot Cycle 25. The two free parameters of the model are fixed by requiring the model to reproduce Cycle 24 upon being driven by active region data for Cycle 23. Our forecasting m...

The solar dipole moment at activity minimum is a good predictor of the strength of the subsequent solar cycle. Through a systematic analysis using a state-of-the-art 2×2D solar dynamo model, we found that bipolar magnetic regions (BMR) with atypical characteristics can modify the strength of the next cycle via their impact on the buildup of the dip...

The periods of magnetic activity cycles in the Sun and solar-type stars do not exhibit a simple or even single trend with respect to rotation rate or luminosity. Dynamo models can be used to interpret this diversity and can ultimately help us understand why some solar-like stars do not exhibit a magnetic cycle, whereas some do, and for the latter w...

The periods of magnetic activity cycles in the Sun and solar-type stars do not exhibit a simple or even single trend with respect to rotation rate or luminosity. Dynamo models can be used to interpret this diversity, and can ultimately help us understand why some solar-like stars do not exhibit a magnetic cycle, whereas some do, and for the latter...

We present a set of four global Eulerian/semi-Lagrangian fluid solver (EULAG) hydrodynamical (HD) and magnetohydrodynamical (MHD) simulations of solar convection, two of which are restricted to the nominal convection zone, and the other two include an underlying stably stratified fluid layer. While all four simulations generate reasonably solar-lik...

The origin of cycle-to-cycle variations in solar activity is currently the focus of much interest. It has recently been pointed out that large individual active regions with atypical properties can have a significant impact on the long-term behavior of solar activity. We investigate this possibility in more detail using a recently developed \(2\tim...

Is the Sun a solar-type star?
The Sun's activity, including sun-spot activity, varies on an 11-year cycle driven by changes in its magnetic field. Other nearby solar-type stars have their own cycles, but the Sun does not seem to match their behavior. Strugarek et al. used magnetohydrodynamic simulations to show that stellar activity periods should...

The largest solar flares, of class X and above, are often associated with strong energetic particle acceleration. Based on the self-similar distribution of solar flares, self-organized criticality models such as sandpiles can be used to successfully reproduce their statistics. However, predicting strong (and rare) solar flares turns out to be a sig...

This paper describes the recommended solar forcing dataset for CMIP6 and highlights changes with respect to CMIP5. The solar forcing is provided for radiative properties, namely total solar irradiance (TSI), solar spectral irradiance (SSI), and the F10.7 index as well as particle forcing, including geomagnetic indices Ap and Kp, and ionization rate...

We present results from a global MHD simulation of solar convection in which the heat transported by convective flows varies in-phase with the total magnetic energy. The purely random initial magnetic field specified in this experiment develops into a well-organized large-scale antisymmetric component undergoing hemispherically synchronized polarit...

The surprising thinness of the solar tachocline is still not understood with certainty today. Among the numerous possible scenarios suggested to explain its radial confinement, one hypothesis is based on Maxwell stresses that are exerted by the cyclic dynamo magnetic field of the Sun penetrating over a skin depth below the turbulent convection zone...

Surface observations indicate that the speed of the solar meridional circulation in the photosphere varies in anti-phase with the solar cycle. The current explanation for the source of this variation is that inflows into active regions alter the global surface pattern of the meridional circulation. When these localized inflows are integrated over a...

In this paper we complete the presentation of a new hybrid 2 × 2D flux transport dynamo (FTD) model of the solar cycle based on the Babcock-Leighton mechanism of poloidal magnetic field regeneration via the surface decay of bipolar magnetic regions (BMRs). This hybrid model is constructed by allowing the surface flux transport (SFT) simulation desc...

The origin of magnetic cycles in the Sun and other cool stars is one of the great theoretical challenge in stellar astrophysics that still resists our understanding. Ab-initio numerical simulations are today required to explore the extreme turbulent regime in which stars operate and sustain their large-scale, cyclic magnetic field. We report in thi...

Observations of X-ray emission [mdash] a diagnostic tool for the mechanisms driving stellar magnetic fields [mdash] from four cool stars call into question accepted models of magnetic-field generation in the Sun and stars. See Letter p.526

The 11 year solar activity cycle is the most prominent periodic manifestation of the magnetohydrodynamical (MHD) large-scale dynamo operating in the solar interior, yet longer and shorter (quasi-) periodicities are also present. The so-called "quasi-biennial" signal appearing in many proxies of solar activity has been gaining increasing attention s...

This paper describes the solar forcing dataset for CMIP6 and highlights in particular changes with respect to the CMIP5 recommendation. The solar forcing is provided for radiative properties, i.e., total solar irradiance (TSI) and solar spectral irradiance (SSI), and F10.7 cm radio flux, as well as particle forcing, i.e., geomagnetic indices Ap and...

The impressive development of global numerical simulations of turbulent stellar interiors unveiled a variety of possible differential rotation (solar or anti-solar), meridional circulation (single or multi-cellular), and dynamo states (stable large scale toroidal field or periodically reversing magnetic fields). Various numerical schemes, based on...

We perform a mean-field analysis of the EULAG-MHD millenium simulation of global magnetohydrodynamical convection presented in Passos and Charbonneau (2014). The turbulent electromotive force (emf) operating in the simulation is assumed to be linearly related to the cyclic axisymmetric mean magnetic field and its first spatial derivatives. At every...

The solar meridional circulation is a "slow", large scale flow that transports magnetic field and plasma throughout the convection zone in the (r, θ) plane and plays a crucial role in controlling the magnetic cycle solutions presented by flux transport dynamo models. Observations indicate the this flow speed varies in anti-phase with the solar cycl...

After more than half a century of community support related to the science of
"solar activity'', IAU's Commission 10 was formally discontinued in 2015, to be
succeeded by C.E2 with the same area of responsibility. On this occasion, we
look back at the growth of the scientific disciplines involved around the world
over almost a full century. Solar a...

We investigate the possible development of magnetohydrodynamical
instabilities in the EULAG-MHD "millenium simulation" of Passos & Charbonneau
(2014). This simulation sustains a large-scale magnetic cycle characterized by
solar-like polarity reversals taking place on a regular multidecadal cadence,
and in which zonally-oriented bands of strong magn...

The need for reliable predictions of the solar activity cycle motivates the development of dynamo models incorporating a representation of surface processes sufficiently detailed to allow assimilation of magnetographic data. In this series of papers we present one such dynamo model, and document its behavior and properties. This first paper focuses...

After more than half a century of community support related to the science of “solar activity”, IAU's Commission 10 was formally discontinued in 2015, to be succeeded by C.E2 with the same area of responsibility. On this occasion, we look back at the growth of the scientific disciplines involved around the world over almost a full century. Solar ac...

We propose to use a deterministically-driven class of self-organized criticality sandpile models to carry out predictions of the largest, most dangerous, and hardest to predict solar flares.

We present calculations of stratospheric chemical abundances variations between different levels of solar activity using a simple photochemistry model in transient chemistry mode. Different models for the reconstruction of the solar spectrum, as well as observations from the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and Spectral Irr...

Observations of the Sun's corona during the space era have led to a picture of relatively constant, but cyclically varying solar output and structure. Longer-term, more indirect measurements, such as from 10Be, coupled by other albeit less reliable contemporaneous reports, however, suggest periods of significant departure from this standard. The Ma...

The form of the solar meridional circulation is a very important ingredient
for mean field flux transport dynamo models. Yet a shroud of mystery still
surrounds this large-scale flow, given that its measurement using current
helioseismic techniques is challenging. In this work we use results from 3D
global simulations of solar convection to infer t...

Onboard the International Space Station (ISS), two instruments are observing the solar spectral irradiance (SSI) at wavelengths from 16 to 2900 nm. Although the ISS platform orientation generally precludes pointing at the Sun more than 10 – 14 days per month, in November/December 2012 a continuous period of measurements was obtained by implementing...

Over the past several decades, Flux-Transport Dynamo (FTD) models have emerged as a popular paradigm for explaining the cyclic nature of solar magnetic activity. Their defining characteristic is the key role played by the mean meridional circulation in transporting magnetic flux and thereby regulating the cycle period. Most FTD models also incorpor...

Numerical simulations that reproduce solar-like magnetic cycles can be used
to generate long-term statistics. The variations in N-S hemispheric cycle
synchronicity and amplitude produced in simulations has not been widely
compared to observations. The observed limits on asymmetry show that
hemispheric sunspot area production is no more than 20% asy...

We present a numerical simulation of the formation and evolution of the solar photospheric magnetic network over a full solar cycle. The model exhibits realistic behavior as it produces large, unipolar concentrations of flux in the polar caps, a power-law flux distribution with index –1.69, a flux replacement timescale of 19.3 hr, and supergranule...

Requiring that numerical estimates of the flow trajectories comply with the fundamental Euler expansion formula that governs the evolution of a volume of fluid leads to a second-order nonlinear Monge–Ampère partial differential equation (MAE). In Cossette and Smolarkiewicz (2011) [15], a numerical algorithm based on solving the MAE with an inexact...

The Sun's magnetic field is the engine and energy source driving all phenomena collectively defining solar activity, which in turn structures the whole heliosphere and significantly impacts Earth's atmosphere down at least to the stratosphere. The solar magnetic field is believed to originate through the action of a hydromagnetic dynamo process ope...

We analyse the statistical properties of the stable magnetic cycle unfolding in an extended 3D magnetohydrodynamic simulation of solar convection produced with the EULAG-MHD code. The millennium simulation spans over 1650 years, in the course of which forty polarity reversals take place on a regular ~40 yr cadence, remaining well-synchronized acros...

We assess the predictive capabilities of various classes of avalanche models
for solar flares. We demonstrate that avalanche models cannot generally be used
to predict specific events due to their high sensitivity to their embedded
stochastic process. We show that deterministically driven models can
nevertheless alleviate this caveat and be efficie...

Proper numerical simulation of the Earth’s climate change requires reliable knowledge of solar irradiance and its variability on different time scales, as well as the wavelength dependence of this variability. As new measurements of the solar spectral irradiance have become available, so too have new reconstructions of historical solar irradiance v...

We present a reconstruction of the solar spectrum in the near and mid-ultraviolet spectral range during the Maunder Minimum, a period of strongly suppressed magnetic activity spanning the second half of the 17th century. This spectral reconstruction is based on an extension of the Monte Carlo Solar Spectral Irradiance Model (MOCASSIM). The new vers...

We develop and discuss the properties of a new class of lattice-based
avalanche models of solar flares. These models are readily amenable to a
relatively unambiguous physical interpretation in terms of slow twisting of a
coronal loop. They share similarities with other avalanche models, such as the
classical stick--slip self-organized critical mode...

This chapters establishes the physical and mathematical bases of
magnetohydrodynamics, the theory describing the dynamical interactions
of the flow of an electrically conducting fluid with a magnetic field.
After an overview of classical hydrodynamics, the magnetohydrodynamical
induction equation is derived from Maxwell's equations, together with
t...