arXiv subjects

Loren Matilsky

Publications and source records attributed to Loren Matilsky.

4 recordsLinked to original sources

arXiv2026

Superrotation and Jet Migration in Simulations of Jupiter's Convective Zone and Weather Layer

The mean zonal flow observed on Jupiter consists of an intricate pattern of jets, or bands of zonal flow moving prograde or retrograde compared to the bulk planetary rotation. The strongest flow is a superrotating (prograde) jet near the equator, which is flanked by 6-7 retrograde/prograde pairs of weaker jets per hemisphere. The two primary drivers of Jupiter's zonal flows are thought to be "shallow" baroclinically driven quasi-two-dimensional turbulence in an outer, stably stratified weather layer (WL) and "deep" rotationally constrained buoyantly driven three-dimensional Busse columns in the convective zone (CZ) just underneath the WL. To study both driving mechanisms simultaneously, we implement two rotating, three-dimensional, spherical-shell, anelastic convection simulations of a Jovian-like planet. In one case, the CZ is isolated, whereas in the other case, the upflows are allowed to overshoot into a stably stratified near-surface region, representing an idealized weather layer. We find that in both cases, homogenization of potential vorticity (whose forms in the CZ and WL are distinct) initially creates multiple jets at high latitudes, whereas angular momentum transport by Busse columns drives equatorial superrotation at low latitudes. The presence of an idealized WL significantly alters the thermal wind balance, resulting in large deviations of the meridional contours of the zonal flow from alignment with the rotation axis. Although the superrotation remains stable, the weaker high-latitude jets slowly migrate poleward and/or merge on a very long time scale (O(10) diffusion time scales or thousands of eddy turnover times).

astro-ph.EP↗

arXiv2023

The Puzzling Structure of Solar Convection: Window into the Dynamo

The operation of the solar dynamo, with all of its remarkable spatio-temporal ordering, remains an outstanding problem of modern solar physics. A number of mechanisms that might plausibly contribute to its operation have been proposed, but the relative role played by each remains unclear. This uncertainty stems from continuing questions concerning the speed and structure of deep-seated convective flows. Those flows are in-turn thought to sustain both the Sun's turbulent EMF and the large-scale flows of differential rotation and meridional circulation suspected of influencing the dynamo's organization and timing. Continued progress in this area is complicated by (i) inconsistencies between helioseismic measurements of convective and meridional flow made with different techniques and instruments, and (ii) a lack of high-latitude data for convection, differential rotation, and meridional flow. We suggest that the path forward to resolving these difficulties is twofold. First, the acquisition of long-term helioseismic and emissivity measurements obtained from a polar vantage point is vital to complete our picture of the Sun's outer convection zone. Second, sustained and expanded investment in theory-oriented and combined theory/observational research initiatives will be crucial to fully exploit these new observations and to resolve inconsistencies between existing measurements.

astro-ph.SR↗

arXiv2020

Exploring Bistability in the Cycles of the Solar Dynamo through Global Simulations

The calling card of solar magnetism is the sunspot cycle, during which sunspots regularly reverse their polarity sense every 11 years. However, a number of more complicated time-dependent behaviors have also been identified. In particular, there are temporal modulations associated with active longitudes and hemispheric asymmetry, when sunspots appear at certain solar longitudes or else in one hemisphere preferentially. So far, a direct link between between this asymmetric temporal behavior and the underlying solar dynamo has remained elusive. In this work, we present results from global, 3D magnetohydrodynamic (MHD) simulations, which for the first time display both behavior reminiscent of the sunspot cycle (regular polarity reversals and equatorward migration of internal magnetic field) and asymmetric, irregular behavior that in the simulations we interpret as active longitudes and hemispheric asymmetry. The simulations are thus bistable, in that the turbulent convection can stably support two distinct flavors of magnetism at different times, in superposition, or with smooth transitions from one state to the other. We discuss this new family of dynamo models in the context of the extensive observations of the Sun's surface magnetic field with the Solar and Heliospheric Observatory (SOHO) and the Solar Dynamics Observatory (SDO), as well as earlier observations of sunspot number and synoptic maps. We suggest that the solar dynamo itself may be bistable in nature, exhibiting two types of temporal behavior in the magnetic field.

astro-ph.SR↗

arXiv2018

Rossby Vortices in Thin Magnetized Accretion Discs

We study the Rossby wave instability (RWI) in a thin accretion disc threaded by an initially toroidal magnetic field using the magnetohydrodynamics (MHD) code PLUTO. We find that for plasma $10^1 < β< 10^3$ , the growth rate and late-time density are suppressed, whereas for plasma $β> 10^3$, the magnetic field has negligible effect. The initially toroidal field is twisted inside the vortex and expelled at late times. This creates a radially directed field outside the vortex region, which can be understood via a simple kinematic model of a magnetic field in a rotating fluid and may be observable via polarised dust emission.

astro-ph.EP↗