COMPUTER AIDED MODELING OF ASTROPHYSICAL PLASMA

MIGUEL A. ALOY TORÁS

CAMAP project

P.I. of CAMAP Project: Miguel A. Aloy Torás
Project full title: CAMAP: Computer aided modeling of astrophysical plasma
Grant agreement no.: 259276
Duration: 60 months
CAMAP is an Starting Independent Researcher Grant funded by the European Research Councill
Link to the News of University of Valencia
Link to a recent price: Premio IDEA 2011.

Contents

• Project Summary
• Why is it CAMAP groundbreaking?
• Backup strategies
• CAMAP a multidisciplinary proposal
• CAMAP team
• CAMAP Legacy
• Follow the latest news of CAMAP in Facebook

Project Summary:

In a broad sense, this project will be aimed at obtaining a deeper insight into the physical processes taking place in astrophysical magnetized plasmas, which involve a broad range of length and time scales. To study these scenarios the PI will employ different numerical codes as virtual tools that enable me to experiment on virtual laboratories (computers) with distinct initial a...nd boundary conditions, in a fully analogous way to the experiments that can be done in an actual laboratory. Among the kind of sources the PI is interested to consider, the PI outlines the following: Gamma-Ray Bursts (GRBs), extragalactic jets from Active Galactic Nuclei (AGN), magnetars and collapsing stellar cores. A number of important questions are still open regarding the fundamental properties of these astrophysical sources. The complete description of the collimation and acceleration of astrophysical jets is still being elucidated.

The composition, high-energy emission, and the mechanisms by which jets propagate from their formation sites to the locations where they are observed is a subject of active scientific debate. Predicting source dynamics and gravitational waveforms is important to understand hoped-for observations in the current generation of ground-based, gravitational- wave detectors, and essential to achieve design sensitivity in future space-based detectors. Additionally, there are analytical issues on the formalism in relativistic dynamics that are not completely resolved, particularly in the covariant extension of resistive magnetohydrodynamics. All these problems are so complex that only a computational approach is feasible.

The PI plans to study them by means of (Magneto-)Hydrodynamics (MHD) numerical simulations with a suitable coupling with the dynamics of populations of non-thermal emitting particles. Most of these astrophysical plasmas are relativistic (e.g., GRBs, AGN jets). Thus, they must be treated with a suitable Special or General Relativity approach.

The virtual laboratory the PI plans to develop will therefore be fully equipped with the most modern algorithms to cope with Special Relativistic MHD (SRMHD) or General Relativistic MHD (GRMHD) fluids. Other scenarios can be appropriately described by a classical or Newtonian MHD approach; hence the virtual lab will also be prepared for that. A principal focus of the project will be to assess the relevance of magnetic fields in the generation, collimation and ulterior propagation of relativistic jets from the GRB progenitors and from AGNs. More generally, the PI will pursue the goal of understanding the process of amplification of seed magnetic fields until they become dynamically relevant, e.g., using semi-global and local simulations of representative boxes of collapsed stellar cores.

A big emphasis will be put on including all the relevant microphysics (e.g. neutrino physics), non-ideal effects (particularly, reconnection physics) and energy transport due to neutrinos and photons to account for the relevant processes in the former systems.

A milestone of this project will be to end up with a numerical tool that enables us to deal with General Relativistic Radiation Magnetohydrodynamics problems in Astrophysics.

Why is it CAMAP groundbreaking?

Because of the diversity of time and length scales, so far we have only models for different stages in the gamma-ray burst (GRB) phenomenon.
I will try to obtain a consistent model to explain gamma-ray bursts from the collapse of massive stellar cores to the late afterglow.

State-of-the-art COLLAPSE Stellar core collapse from pre-supernova models including (some) of the following: B-fields, GR, microphysics, 3D, v-transport OUTFLOW Ad-hoc model of the central engine hypercreating-BH + initial B (strenght + topology) Jet injection conditions Jet propagation: AMR, (ideal) (G)R(M)HD, estimate flow conditions at transparency RADIATION Assumed ejecta structure, kinematic models, analytic or simplified emission models

Magneto-rotational core collapse from pre-supernova models in full (time- evolving) GR, including microphysics, and (simplified) !-transport. Collapse followed beyond BH-formation, until a hyper-accreting BH forms. B-field consistently computed from the evolution of the pre-supernova core. Propagation of the jet in GRRMHD until it reaches transparency. Consistent calculation of the observational signature (radiation). Extensions: 3D, improved !-transport, more emission processes (IC), etc.

Backup strategies

Among our goals, we also pretend to improve on our previous work. Even if everything else fails, this might allow us to perform high-level science and obtain cutting-edge results (employing well tested methodology):

• Increasing dimensionality (computer scientists + increase in computing power):
  • From 2D to 3D in progenitors of GRBs: jet stability, mass entrainment.
  • From 1D to 2D in internal shocks: account for the lateral expansion, transition from early afterglow to late afterglow, efficiency of the model
• Including magnetic fields where we had neglected them before:
  • In progenitors of long-GRBs: effects of ad-hoc fields on the propagation and on the observational fingerprint of jets.
• Inferring the ejecta magnetization in the prompt GRB phase and in the early afterglow.
• Numerical study of relativistic (magneto-)fluid instabilities. E.g.: Rayleigh-Tailor instabilities in decelerating shells and its implication for GRBs.
• Using realistic magnetospheric models and studying the emission properties of the quasi periodic oscillations in the tail of giant flares of SGRs.

CAMAP a multidisciplinary proposal

CAMAP team

• CAMAP project relies on the interaction between postdocs which share a common expertise in numerical methods for magnetohydrodynamics.
• We request a Ph.D student from this project, but we expect to attract one or two additional ones (UV funds, Spanish FPI, USA Fulbright, German DAAD, etc.).
  • Nicolas DeBrye (Grisolia Fellow)
  • Jesús Rueda (Grisolia Fellow)
  • Carlos Cuesta (Master Student)
  • Sergio Miranda

CAMAP Legacy

• This project is aimed at obtaining a deeper insight into the physical processes taking place in astrophysical objects hosting plasma that can be modeled as a fluid, among them, I outline GRBs, AGN jets and compact objects.
• Understand the role of the magnetic field in the dynamics of these sources.
• When/Where non-ideal effects are relevant?
• We may try to bridge the gap between stellar core-collapse and the production of relativistic outflows and obtain a self-consistent picture from collapse to the observational signature (full Einstein, microphysics, transport, emission).
  • What is the jet composition?
  • How do the outflows collimate/accelerate in a dynamically evolving space-time?
• Characterization of the mechanism to build dynamically important B-fields from tiny seed values, and of the preferred field topology.
• Gravitational waveforms (stellar core-collapse, outflows). Needed to extract signals from the "detectable noise" in ground-based and space-based detectors.
• We will develop a number of numerical tools to deal with astrophysical sources where the physics can be is dominated by (non-ideal) (relativistic) (magneto-) HD.

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