Identification of fast magnetic reconnection events in accretion disks under the action of MHD instabilities LUรS H.S. KADOWAKI ELISABETE M. DE GOUVEIA DAL PINO JAMES M. STONE OCTOBER 17, 2017 MAGNETIC FIELDS IN THE UNIVERSE VI: FROM LABORATORY AND STARS TO THE PRIMORDIAL STRUCTURES
34
Embed
fast magnetic reconnection events in accretion disks under ...โข4st step: Evaluate the eigenvectors of the Hessian matrix ๐ป= ๐ ๐๐ ๐๐ ๐ ๐ ๐๐ ๐๐
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Identification of fast magnetic reconnection events in accretion disks under the action of MHD instabilitiesL U ร S H . S . K A D O WA K I
E L I S A B E T E M . D E G O U V E I A D A L P I N O
J A M E S M . S TO N E
O C TO B E R 1 7 , 2 0 1 7
M A G N E T I C F I E L D S I N T H E U N I V E R S E V I : F R O M L A B O R ATO R Y A N D S TA R S TO T H E P R I M O R D I A L S T R U C T U R E S
Outline
โข Magnetic reconnection in accretion disk systems
โข Numerical simulations with a shearing-box approach
โข MHD instabilities in accretion disks
โข Identification of fast magnetic reconnection events in the surroundings of accretion disks
โข Conclusions
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 2
Accretion disk systems
โข Accretion disks systems are believed to be very common structures in the Universe
โข These systems are associated to:โข Black Hole Binaries (BHBs)
โข Active Galactic Nuclei (AGNs)
โข Young Stellar Objects (YSOs) and so protoplanetary disks
โข The formation of a turbulent corona above and below accretion disks plays an important role in magnetic reconnection events
โข These events could explain the flare emissions in X-ray (YSOs) and in radio and gamma-ray (BHBs and AGNs)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 3
Turbulent magnetic reconnection in collisional flowsโข Lazarian & Vishiniac (1999) model (Kowalโs talk):โข Reconnection triggered by tubulence
โข Several reconnection points (at all scales) due to the wandering magnetic field lines
โข โFastโ reconnection
โข ๐๐๐๐ โ ๐๐ด๐๐ด2
Numerical simulations (Kowal et al. 2009, 2012)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 4
MHD numerical simulations of accretion disks and coronaMAGNETIC RECONNECTION UNDER THE ACTION OF MHD INSTABILITIES
Aims
โข The formation of a large scale poloidal magnetic field by the arising of loops due to the Parker-Rayleigh-Taylor instability
โข The role of Parker-Rayleigh-Taylor and magnetorotationalinstabilities in the formation of a turbulent magnetized corona around accretion disksโข Where magnetic reconnection events could occur
โข The identification of fast magnetic reconnection events by the statistical analysis of the reconnection rate in the corona and disk
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 6
Numerical method (shearing-box)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 7
Kadowaki (masterโs thesis, 2011)
โข Shearing-Box (Hawley et al., 1995):โข A steady flow with a linear shearing velocity:
โข For a Keplerian disk:
Kadowaki et al. (2017, in prep.)
Numerical method (shearing-box)โข MHD equations:
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 8
๐๐ ๐๐โข ๐๐: Indicates the fastest decaying of ๐ (Thickness)
โข Projection of the magnetic and velocity fields along ๐๐, ๐๐ and ๐๐ directions
Algorithm
25Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017
โข We have adapted the algorithm of Zhdankin et al. (2013) and extended to a 3D analysis
โข 5st step: Evaluate the magnetic reconnection rate
๐๐
๐๐
๐๐๐๐๐ด
=1
2แค
๐๐1๐๐ด ๐๐๐ค๐๐
โ แค๐๐1๐๐ด ๐ข๐๐๐๐
๐๐ด =๐ต๐1
2 + ๐ต๐22 + ๐ต๐3
2
๐๐๐๐ค๐๐
๐ข๐๐๐๐
๐ <1
2๐๐๐๐ฅ
๐ <1
2๐๐๐๐ฅ
๐ >1
2๐๐๐๐ฅ
Similar to Kowal et al. (2009)
Magnetic reconnection rate (Resolution: 2563)
26Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017
Upper Corona
Confirmed!Rejected!
Magnetic reconnection rate (Resolution: 2563)
27Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017
Upper Corona
Magnetic reconnection rate (Resolution: 2563)
28Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017
Magnetic reconnection rate (Resolution: 2563)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 29
Magnetic reconnection rate (Resolution: 2563)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 31
Power spectrum (Resolution: 2563)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 32
t = 1 (Orbits) t = 2 (Orbits)
Power spectrum (Resolution: 2563)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 33
t = 4 (Orbits) t = 5 (Orbits)
Conclusions
โข Our simulations have revealed the arising of magnetic loops due to the PRTI followed by the development of turbulence due to PRTI and MRI
โข Even with an initial high magnetized regime, the disk evolves to a gas-pressure dominant regime with a magnetized coronaโข Transport of magnetic field from the disk to the corona by buoyance process
โข We have evaluated the magnetic reconnection rates and detected the presence of fast magnetic reconnection events, as predicted by the theory of turbulence-induced fast reconnection (Lazarian & Vishiniac, 1999)
โข The algorithm applied to this work has demonstrated to be an efficient tool for the identification of magnetic reconnection sites in numerical simulations
Kadowaki, de Gouveia Dal Pino & Stone (2017, in prep.)
Kadowaki, de Gouveia Dal Pino and Stone MFU VI - 2017 34