Dispersion of small magnetic elements inside active regions on the Sun. (arXiv:1812.05469v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Abramenko_V/0/1/0/all/0/1">Valentina I. Abramenko</a>
A process of diffusion of small-scale magnetic elements inside four active
regions (ARs) was analyzed. Line-of-sight magnetograms acquired by the
Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory
(SDO) during a two-day time interval around the AR culmination time were
utilized. Small magnetic elements of size of 3-100 squared HMI pixels with the
field strength above the detection threshold of 30 Mx cm$^{-2}$ were detected
and tracked. The turbulent diffusion coefficient was retrieved using the
pair-separation technique. Comparison with the previously reported quiet-sun
(QS) diffusivity was performed. It was found that: i) dispersion of small-scale
magnetic elements inside the AR area occurs in the regime close to normal
diffusion, whereas well-pronounced super-diffusion is observed in QS; ii) the
diffusivity regime operating in an AR (the magnitude of the spectral index and
the range of the diffusion coefficient) does not seem to depend on the
individual properties of an AR, such as total unsigned magnetic flux, state of
evolution, and flaring activity. We conclude that small-scale magnetic elements
inside an AR do not represent an undisturbed photosphere, but they rather are
intrinsic part of the whole coherent magnetic structure forming an active
region. Moreover, turbulence of small-scale elements in an AR is not closely
related to processes above the photosphere, but it rather carries the footprint
of the sub-photospheric dynamics.
A process of diffusion of small-scale magnetic elements inside four active
regions (ARs) was analyzed. Line-of-sight magnetograms acquired by the
Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory
(SDO) during a two-day time interval around the AR culmination time were
utilized. Small magnetic elements of size of 3-100 squared HMI pixels with the
field strength above the detection threshold of 30 Mx cm$^{-2}$ were detected
and tracked. The turbulent diffusion coefficient was retrieved using the
pair-separation technique. Comparison with the previously reported quiet-sun
(QS) diffusivity was performed. It was found that: i) dispersion of small-scale
magnetic elements inside the AR area occurs in the regime close to normal
diffusion, whereas well-pronounced super-diffusion is observed in QS; ii) the
diffusivity regime operating in an AR (the magnitude of the spectral index and
the range of the diffusion coefficient) does not seem to depend on the
individual properties of an AR, such as total unsigned magnetic flux, state of
evolution, and flaring activity. We conclude that small-scale magnetic elements
inside an AR do not represent an undisturbed photosphere, but they rather are
intrinsic part of the whole coherent magnetic structure forming an active
region. Moreover, turbulence of small-scale elements in an AR is not closely
related to processes above the photosphere, but it rather carries the footprint
of the sub-photospheric dynamics.
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