1 / 13

Mikhail V. Medvedev (U Kansas)

Theory and numerical modeling of radiation from sub- Larmor -scale magnetic turbulence. Mikhail V. Medvedev (U Kansas). In collaboration with : Aake Nordlund , Troels Haugboelle , Jacob Frederiksen ( Niels Bohr Inst.).

mab
Download Presentation

Mikhail V. Medvedev (U Kansas)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Theory and numerical modeling of radiation from sub-Larmor-scale magnetic turbulence Mikhail V. Medvedev (U Kansas) In collaboration with: AakeNordlund, TroelsHaugboelle, Jacob Frederiksen (Niels Bohr Inst.) HEDLA 2012 Tallahassee, FL, 3 May 2012

  2. GRBs are relativistic shocks How to tell Weibel-mediated shocks apart from other types of shocks (if any)? (credit: Hededal, Haugbolle, 2005)

  3. Weibel-like Inst. are ubiquitous Beam through plasma Gamma-Ray Bursts Astrophysical Jets, … Collisionless shock Magnetic reconnection How diagnose Weibel-generated B-fields? (credit: Kato, Takabe, 2009; Swisdak, et al, 2008; Silva et al 2009)

  4. Concept: “GRB in a Lab” /originally proposed on HEDLA 2006/ Scaling from Lab to Astro scales is not an issue  ongoing Collisionless Shock experiments Radiation observed as GRB gamma-ray emission can directly be obtained in Lab Experiments (!)

  5. Universal diagnostics Radiation produced by this particles must carry unique information about B-field statistical properties | look for radiation spectra (credit: Hededal, Haugbolle)

  6. Dedicated PIC simulations of Weibel Time = 6 τplasma B2/8π Time = 8 τplasma Time = 10 τplasma

  7. Angular dependence of radiation One can probe: orientation of filaments + PDF anisotropy observers

  8. Time dependence of radiation Time = 6 τplasma Time = 8 τplasma time Time = 10 τplasma One can probe: evolution of B-field + PDF

  9. Two regimes δjitter~ (deflection angle)/(beaming) ~ eBλ/mc2 ~ 0.6 BkGλcm <<1 ω0 ω-ξ Small-angle deflections B δjitter < 1 ω1 ωj~ kBc γ2 ω-η B Large-angle deflections ω1/3 1 < δjitter < γ ω0 exp(-ω/ωs) ωs ωj~ δjitt-3ωs

  10. Extrapolate: Radiation at later times γ=10 large-angle regime γ=4 small-angle regime small-angle regime large-angle regime small-angle regime

  11. What can we learn from spectra? measures B-field correlation length, λ, via <λ-1 γ2> measures B via <Bγ2> measures electron N(γ)distribution measures B-field spectrum, Bk index • monoenergetic electron beam with known Lorentzγ • power-law B-field spatial spectrum, Bk ~ k-ξ

  12. Suggestion: stacking data can help Spectrum construction requires lots of photons  may be difficult for a single pulse (too short) Shots are statistically independent and so are the resultant field structure  averaging over many pulses increases S/N by √Nshots, but keeps statistical properties of Weibel B-fields  equivalent to ensemble-averaging

  13. Summary Weibel-type filamentation instabilities are ubiquitous in High-Energy-Density environments: Laser Plasmas, Collisionless Shocks, some set-ups of Magnetic Reconnection, Astrophysical Sources Radiation production from sub-Larmor-scale magnetic fields contains unique information on the B-field structure “GRB in a Lab” – tremendous opportunity to not only observe and study collisionless shocks with minimal scaling (if any) to astrophysical systems, but also to generate and explore radiation properties of real emission from astrophysical sources of GRBs Spectral properties of produced radiation provide powerful diagnostic: they can tell the magnitude of B-field, its characteristic correlation scale, the B-field spatial spectrum, along with the energy distribution of emitting particles.

More Related