Coronae as Consequence of Large Scale Magnetic Fields in Turbulent Accretion Disks
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Coronae as Consequence of Large Scale Magnetic Fields in Turbulent Accretion Disks. / G. Blackman, Eric; Pessah, Martin Elias.
In: Astrophysical Journal Letters, Vol. 704, No. 2, 20.10.2009, p. L113-L117.Research output: Contribution to journal › Journal article › Research › peer-review
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TY - JOUR
T1 - Coronae as Consequence of Large Scale Magnetic Fields in Turbulent Accretion Disks
AU - G. Blackman, Eric
AU - Pessah, Martin Elias
PY - 2009/10/20
Y1 - 2009/10/20
N2 - Non-thermal X-ray emission in compact accretion engines can be interpreted to result from magnetic dissipation in an optically thin magnetized corona above an optically thick accretion disk. If coronal magnetic field originates in the disk and the disk is turbulent, then only magnetic structures large enough for their turbulent shredding time to exceed their buoyant rise time survive the journey to the corona. We use this concept and a physical model to constrain the minimum fraction of magnetic energy above the critical scale for buoyancy as a function of the observed coronal to bolometric emission. Our results suggest that a significant fraction of the magnetic energy in accretion disks resides in large scale fields, which in turn provides circumstantial evidence for significant non-local transport phenomena and the need for large scale magnetic field generation. For the example of Seyfert AGN, for which of order 30 per cent of the bolometric flux is in the X-ray band, we find that more than 20 per cent of the magnetic energy must be of large enough scale to rise and dissipate in the corona.
AB - Non-thermal X-ray emission in compact accretion engines can be interpreted to result from magnetic dissipation in an optically thin magnetized corona above an optically thick accretion disk. If coronal magnetic field originates in the disk and the disk is turbulent, then only magnetic structures large enough for their turbulent shredding time to exceed their buoyant rise time survive the journey to the corona. We use this concept and a physical model to constrain the minimum fraction of magnetic energy above the critical scale for buoyancy as a function of the observed coronal to bolometric emission. Our results suggest that a significant fraction of the magnetic energy in accretion disks resides in large scale fields, which in turn provides circumstantial evidence for significant non-local transport phenomena and the need for large scale magnetic field generation. For the example of Seyfert AGN, for which of order 30 per cent of the bolometric flux is in the X-ray band, we find that more than 20 per cent of the magnetic energy must be of large enough scale to rise and dissipate in the corona.
KW - astro-ph.HE
U2 - 10.1088/0004-637X/704/2/L113
DO - 10.1088/0004-637X/704/2/L113
M3 - Journal article
VL - 704
SP - L113-L117
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2
ER -
ID: 34382997