Cancellation of Small-Scale Magnetic Features. (arXiv:1812.11496v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kaithakkal_A/0/1/0/all/0/1">Anjali J. Kaithakkal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Solanki_S/0/1/0/all/0/1">Sami K. Solanki</a>
We investigate small-scale flux cancellations in a young active region
observed with the high-resolution imaging magnetograph IMaX on the Sunrise
balloon-borne solar observatory. We identified 11 opposite-polarity cancelling
pairs using an automatic detection code, and derived their statistical
properties.We classified the cancellations into two groups. Class I events are
those for which cancellation happens between a pre-existing large magnetic
feature of one polarity and a smaller feature of the other polarity that
emerged/appeared nearby. For Class II events cancellations occur between two
pre-existing, previously unconnected features that converge toward each other.
All studied events have an apparent cancellation time less than 10 minutes and
display a significant transient linear polarization signal along the polarity
inversion line. The cancellation events are characterized by a flux decay rate
of about 10$^{15}$~Mx s$^{-1}$. Horizontal convergence speeds of Class II pairs
fall between 0.3 and 1.22~km s$^{-1}$. The elements often do not converge
directly towards each other, so that the proper motion speeds of the individual
elements is higher, in the range of 1 – 2.7~km s$^{-1}$. We propose that these
cancellation events result from either field-line submergence (Class I), or
reconnection followed by submergence (Class II and/or Class I). Ohmic
dissipation of magnetic energy could also play a role for both classes. We
propose that, at least for the Class II events, the granular motions could
possibly be driving magnetic reconnection, rather than the supergranular
motions proposed for the larger cancellation events studied earlier. Specific
flux cancellation rates of the Class II events seem to indicate that they
belong to somewhat different category of cancellations when compared with those
studied in SOT/Hinode and MDI/SOHO data.
We investigate small-scale flux cancellations in a young active region
observed with the high-resolution imaging magnetograph IMaX on the Sunrise
balloon-borne solar observatory. We identified 11 opposite-polarity cancelling
pairs using an automatic detection code, and derived their statistical
properties.We classified the cancellations into two groups. Class I events are
those for which cancellation happens between a pre-existing large magnetic
feature of one polarity and a smaller feature of the other polarity that
emerged/appeared nearby. For Class II events cancellations occur between two
pre-existing, previously unconnected features that converge toward each other.
All studied events have an apparent cancellation time less than 10 minutes and
display a significant transient linear polarization signal along the polarity
inversion line. The cancellation events are characterized by a flux decay rate
of about 10$^{15}$~Mx s$^{-1}$. Horizontal convergence speeds of Class II pairs
fall between 0.3 and 1.22~km s$^{-1}$. The elements often do not converge
directly towards each other, so that the proper motion speeds of the individual
elements is higher, in the range of 1 – 2.7~km s$^{-1}$. We propose that these
cancellation events result from either field-line submergence (Class I), or
reconnection followed by submergence (Class II and/or Class I). Ohmic
dissipation of magnetic energy could also play a role for both classes. We
propose that, at least for the Class II events, the granular motions could
possibly be driving magnetic reconnection, rather than the supergranular
motions proposed for the larger cancellation events studied earlier. Specific
flux cancellation rates of the Class II events seem to indicate that they
belong to somewhat different category of cancellations when compared with those
studied in SOT/Hinode and MDI/SOHO data.
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