The Solar Internetwork. I. Contribution to the Network Magnetic Flux

Gošić, Milan; Rubio, L. R. Bellot; Suárez, D. Orozco; Katsukawa, Y.; Iniesta, J. C. del Toro

doi:10.1088/0004-637x/797/1/49

Cited by 95 publications

(122 citation statements)

References 36 publications

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“…4.3 has been carried out by Lamb et al (2008) based on SOHO MDI magneto-graph data, and by Zhou et al (2010); Wang et al (2012); Lamb et al (2013); Gošić et al (2014Gošić et al ( , 2016 based on Hinode/SOT/NFI data. Their approach differs somewhat from ours in the definition of the events and the type of data used and partly also in the aims of the studies.…”

Section: Discussionmentioning

confidence: 99%

“…This code is applied to time series of high resolution magnetograms obtained in the quiet Sun with the Imaging Magnetograph eXperiment (IMaX, see Martínez Pillet et al 2011) on the Sunrise balloon-borne telescope (see Solanki et al 2010;Barthol et al 2011). The earlier studies using highresolution data to which our results can be compared have used Hinode/NFI data with a spatial resolution of 0 ′′ .3 (6×10 15 Mx, 6.5×10 15 Mx and 5×10 16 Mx being the lowest detected values of flux per feature reported by Zhou et al 2013, Gošić et al 2014and Thornton & Parnell 2011. The higher spatial resolution (a factor of 5 per pixel, see Sect.…”

Section: Introductionmentioning

confidence: 90%

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Statistical evolution of quiet-Sun small-scale magnetic features using Sunrise observations

Anusha¹,

Solanki²,

Hirzberger³

et al. 2017

A&A

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The evolution of small magnetic features in quiet regions of the Sun provides a unique window to probing solar magnetoconvection. Here we analyze small scale magnetic features in the quiet Sun, using the high resolution, seeing-free observations from the Sunrise balloon borne solar observatory. Our aim is to understand the contribution of different physical processes, such as splitting, merging, emergence and cancellation of magnetic fields to the rearrangement, addition and removal of magnetic flux in the photosphere. We employ a statistical approach for the analysis and the evolution studies are carried out using a feature tracking technique. In this paper we provide a detailed description of the feature tracking algorithm that we have newly developed and we present the results of a statistical study of several physical quantities. The results on the fractions of the flux in the emergence, appearance, splitting, merging, disappearance and cancellation qualitatively agrees with other recent studies (see e.g., Lamb et al. 2008Lamb et al. , 2013. To summarize, the total flux gained in unipolar appearance is an order of magnitude larger than the total flux gained in emergence. On the other hand, the bi-polar cancellation contributes nearly an equal amount to the loss of magnetic flux as unipolar disappearance. The total flux lost in cancellation is nearly 6 − 8 times larger than the total flux gained in emergence. One big difference between our study and previous similar studies is that thanks to the higher spatial resolution of Sunrise we can track features with fluxes as low as 9 × 10 14 Mx. This flux is nearly an order of magnitude lower than the smallest fluxes of the features tracked in the highest resolution previous studies based on Hinode data. The area and flux of the magnetic features follow power-law type distribution, while the lifetimes show either power-law or exponential type distribution depending on the exact definitions used to define various birth and death events. We also statistically determine the evolution of the flux within the features in the course of their lifetime, finding that this evolution depends very strongly on the birth and death process that the features undergo.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 90%

Statistical evolution of quiet-Sun small-scale magnetic features using Sunrise observations

Anusha¹,

Solanki²,

Hirzberger³

et al. 2017

A&A

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“…Thus, they concluded that the magnetic network was unable to fully relax to its ground state even during the extended period of the last solar cycle around 2009. On the other hand Gošić et al (2014) found that the whole network magnetic field can be sustained, at least during the last extended minimum solar cycle phase, via transported and accumulated weak internetwork fields. Thus the found minimum number and/or the ratio with the maximum number of detected MBPs during the maximum phase can help us, in the future, to estimate the strength of the acting surface dynamo in relation to the global magnetic field dynamo and/or the decaying time constant for the global magnetic fields.…”

Section: Discussionmentioning

confidence: 99%

Long-term trends of magnetic bright points

Utz

Müller

Thonhofer

et al. 2015

A&A

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Context. The Sun shows an activity cycle that is caused by its varying global magnetic field. During a solar cycle, sunspots, i.e. extended regions of strong magnetic fields, occur in activity belts that are slowly migrating from middle to lower latitudes, finally arriving close to the equator during the cycle maximum phase. While this and other facts about the strong extended magnetic fields have been well known for centuries, much less is known about the solar cycle evolution of small-scale magnetic fields. Thus the question arises if similar principles exist for small-scale magnetic fields. Aims. To address this question, we study magnetic bright points (MBPs) as proxies for such small-scale, kG solar magnetic fields. This study is based on a homogeneous data set that covers a period of eight years. The number of detected MBPs versus time is analysed to find out if there is an activity cycle for these magnetic features too and, if so, how it is related to the sunspot cycle.Methods. An automated MBP identification algorithm was applied to the synoptic Hinode/SOT G-band data over the period November 2006 to August 2014, i.e. covering the decreasing phase of Cycle 23 and the rise, maximum, and early decrease of Cycle 24. This data set includes, at the moment of investigation, a total of 4162 images, with about 2.9 million single MBP detections. Results. After a careful preselection and monthly median filtering of the data, the investigation revealed that the number of MBPs close to the equator is coupled to the global solar cycle but shifted in time by about 2.5 yr. Furthermore, the instantaneous number of detected MBPs depends on the hemisphere, with one hemisphere being more prominent, i.e. showing a higher number of MBPs. After the end of Cycle 23 and at the starting point of Cycle 24, the more active hemisphere changed from south to north. Clear peaks in the detected number of MBPs are found at latitudes of about ±7 • , in congruence with the positions of the sunspot belts at the end of the solar cycle. Conclusions. These findings suggest that there is indeed a coupling between the activity of MBPs close to the equator with the global magnetic field. The results also indicate that a significant fraction of the magnetic flux that is visible as MBPs close to the equator originates from the sunspot activity belts. However, even during the minimum of MBP activity, a percentage as large as 60% of the maximum number of detected MBPs has been observed, which may be related to solar surface dynamo action.

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“…The close spatiotemporal correlation is tempting to infer an intrinsic relation between the RBE and the flux cancellation. This kind of cancellation may be a consequence of magnetic interaction between network and intranetwork fields, as the supergranular convective flows sweep the latter toward the former (e.g., Wang et al 1998;Gošć et al 2014). Later, p2 cancels again with another negative element n2' (Figures 3(h)-(j)), which could be associated with a recurrent RBE event.…”

Section: Rbes Associated With Photospheric Magnetic Flux Emergence Anmentioning

confidence: 97%

Chromospheric Rapid Blueshifted Excursions Observed With Ibis and Their Association With Photospheric Magnetic Field Evolution

Deng¹,

Chen²,

Liu³

et al. 2015

ApJ

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Chromospheric rapid blueshifted excursions (RBEs) are suggested to be the disk counterparts of type II spicules at the limb and believed to contribute to the coronal heating process. Previous identification of RBEs was mainly based on feature detection using Dopplergrams. In this paper, we study RBEs on 2011 October 21 in a very quiet region at the disk center, which were observed with the high-cadence imaging spectroscopy of the Ca ii 8542 Å line from the Interferometric Bidimensional Spectrometer (IBIS). By using an automatic spectral analysis algorithm, a total of 98 RBEs are identified during an 11 minute period. Most of these RBEs have either a round or elongated shape, with an average area of 1.2 arcsec 2 . The detailed temporal evolution of spectra from IBIS makes possible a quantitative determination of the velocity (∼16 km s −1 ) and acceleration (∼400 m s −2 ) of Ca ii 8542 RBEs, and reveals an additional deceleration (∼−160 m s −2 ) phase that usually follows the initial acceleration. In addition, we also investigate the association of RBEs with the concomitant photospheric magnetic field evolution, using coordinated high-resolution and high-sensitivity magnetograms made by Hinode. Clear examples are found where RBEs appear to be associated with the preceding magnetic flux emergence and/or the subsequent flux cancellation. However, further analysis with the aid of the Southwest Automatic Magnetic Identification Suite does not yield a significant statistical association between these RBEs and magnetic field evolution. We discuss the implications of our results in the context of understanding the driving mechanism of RBEs.

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The Solar Internetwork. I. Contribution to the Network Magnetic Flux

Cited by 95 publications

References 36 publications

Statistical evolution of quiet-Sun small-scale magnetic features using Sunrise observations

Statistical evolution of quiet-Sun small-scale magnetic features using Sunrise observations

Long-term trends of magnetic bright points

Chromospheric Rapid Blueshifted Excursions Observed With Ibis and Their Association With Photospheric Magnetic Field Evolution

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