High cadence spectropolarimetry of moving magnetic features observed around a pore

Abstract

Context. Moving magnetic features (MMFs) are small-size magnetic elements that are seen to stream out from sunspots, generally during their decay phase. Several observational results presented in the literature suggest them to be closely related to magnetic filaments that extend from the penumbra of the parent spot. Nevertheless, few observations of MMFs streaming out from spots without penumbra have been reported. The literature still lacks analyses of the physical properties of these features. Aims. We investigate physical properties of monopolar MMFs observed around a small pore that had developed penumbra in the days preceding our observations and compare our results with those reported in the literature for features observed around sunspots.Methods. We analyzed NOAA 11005 during its decay phase with data acquired at the Dunn Solar Telescope in the Fe i 617.3 nm and the Ca ii 854.2 nm spectral lines with IBIS, and in the G-band. The field of view showed monopolar MMFs of both polarities streaming out from the leading negative polarity pore of the observed active region. Combining different analyses of the data, we investigated the temporal evolution of the relevant physical quantities associated with the MMFs as well as the photospheric and chromospheric signatures of these features. Results. We show that the characteristics of the investigated MMFs agree with those reported in the literature for MMFs that stream out from spots with penumbrae. Moreover, observations of at least two of the observed features suggest them to be manifestations of emerging magnetic arches.

Dynamic properties of bright points in an active region

“…Our transverse velocities compare well with studies of BPs around active regions. Most of these (Berger et al 1998;Möstl et al 2006;Criscuoli et al 2012) find mean horizontal velocities for BPs in active regions in the range 1-2 km s −1 , similar to those found here. It is also noteworthy that some observations (Berger et al 1998;Möstl et al 2006) find that BP velocities are attenuated in active regions compared to quiet Sun regions, as in the present work.…”

“…Criscuoli et al (2012) find similar lifetimes for quiet Sun BPs in their study. It should be noted that Möstl et al (2006) report a mean lifetime of 263 ± 137 s for BPs observed in an active region which is longer than the value derived in the present study.…”

“…83. Criscuoli et al (2012) studied both a decaying active region and a quiet Sun region with the Interferometric BIdimensional Spectrometer (IBIS; Cavallini 2006) and found that the velocities follow a Gaussian distribution with values as high as 2 km s −1 , but did not highlight any differences between BPs found in an active region compared to a quiet region. Likewise, Möstl et al (2006) observed BPs in a sunspot moat and found a mean velocity of 1.11 ± 0.7 km s −1 .…”

The evolution of arch filament systems and moving magnetic features around a sunspot

“…As a kind of basic magnetic elements on the Sun, MMFs play a key role in the decay phase of an AR (e.g., Criscuoli et al 2012). They are described as streaming out of sunspot penumbrae and moving toward the outer boundary of the moat regions.…”

“…The previous two types of MMFs have velocities of about 0.5−1 km s −1 , and the last one had speeds in the range of 2−3 km s −1 (Shine & Title 2001;Zhang et al 2007). It has been suggested that bipolar MMFs are the manifestations of Ω-shaped or U-shaped loops traveling along penumbral filaments, while unipolar MMFs are considered as the movement of single magnetic elements (Zhang et al 2003;Zuccarello et al 2009;Criscuoli et al 2012). According to Thomas et al (2002), MMFs should be the emerging effects of submerged penumbral flux tubes raised by convection.…”