Current and Kinetic Helicity of Long-Lived Activity Complexes

Komm, R.

doi:10.1088/0004-637x/798/1/20

Cited by 22 publications

(21 citation statements)

References 33 publications

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“…The hemisphere preference has also been found in other studies (Gao, Zhang, and Zhao, 2009;Maurya, Ambastha, and Reddy, 2011;Seligman, Petrie, and Komm, 2014;Komm, Gosain, and Pevtsov, 2014). There are a few studies on the combined topology of sub-photospheric flows and photospheric magnetic helicities (Gao, Zhang, and Zhao, 2009;Maurya, Ambastha, and Reddy, 2011;Seligman, Petrie, and Komm, 2014;Komm and Gosain, 2015). In some of these studies, kinetic helicity has been found to show statistically opposite HSR than that of current helicities (Gao, Zhang, and Zhao, 2009).…”

Section: Introductionsupporting

confidence: 65%

Magnetic and Velocity Field Topology in Active Regions of Descending Phase of the Solar Cycle 23

Maurya,

Ambastha

2020

Preprint

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We analyse the topology of photospheric magnetic fields and sub-photospheric flows of several active regions (ARs) that are observed during the peak to descending phase of the solar cycle 23. Our analysis shows clear evidence of hemispheric preferences in all the topological parameters such as the magnetic, current and kinetic helicities, and the 'curl-divergence'. We found that 68%(67%) ARs in the northern (southern) hemisphere with negative (positive) magnetic helicities. Same hemispheric preference sign is found for the current helicities in 68%(68%) ARs. The hemispheric preferences are found to exist statistically for all the time except in few ARs observed during the peak and the end phases of the solar cycle. This means that magnetic fields are dominantly left(right)-helical in scales smaller than individual ARs of northern(southern) hemisphere. We found that magnetic and current helicities parameters show equator-ward propagation similar to the sunspot cycle. The kinetic helicity showed similar hemispheric trend to that of magnetic and current helicity parameters. There are 65%(56%) ARs with negative (positive) kinetic helicity as well as divergence-curl, at the depth of 2.4 Mm, in the northern (southern) hemisphere. The hemispheric distribution of the kinetic helicity becomes more evident at larger depths, e.g., 69%(67%) at the depth of 12.6 Mm. Similar hemispheric trend of kinetic helicity to that of the current helicity supports the mean field dynamo model. We also found that the hemispheric distribution of all the parameters increases with the field strength of ARs. The topology of photospheric magnetic fields and near surface sub-photospheric flow fields did not show good association but the correlation between them enhances with depths which could be indicating more aligned flows at deeper layers of ARs.

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Section: Introductionsupporting

confidence: 65%

Magnetic and Velocity Field Topology in Active Regions of Descending Phase of the Solar Cycle 23

Maurya,

Ambastha

2020

Preprint

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“…Such multiple buoyant segments of a single subsurface flux tube may be produced by intense turbulence of localized regions in the convection zone. Meanwhile, examining Carrington longitudes of recurrent magnetic flux emergence for several solar rotations (called "long-lived activity complexes"), Komm & Gosain (2015) revealed that each such activity complex typically has a mixture of positive and negative current helicity over its lifetime. In these activity complexes, newly emerging magnetic flux interacts with pre-existing flux of prior ARs, which may cause an increase in magnetic field complexity and lead to flares at an enhanced rate.…”

Section: Discussionmentioning

confidence: 99%

Magnetic Helicity Flux across Solar Active Region Photospheres: II. Association of Hemispheric Sign Preference with Flaring Activity during Solar Cycle 24

Park,

Leka,

Kusano

2021

Preprint

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In our earlier study of this series (Park et al. 2020, Paper I), we examined the hemispheric sign preference (HSP) of magnetic helicity flux dH/dt across photospheric surfaces of 4802 samples of 1105 unique active regions (ARs) observed during solar cycle 24. Here, we investigate any association of the HSP, expressed as a degree of compliance, with flaring activity, analyzing the same set of dH/dt estimates as used in Paper I. The AR samples under investigation are assigned to heliographic regions (HRs) defined in the Carrington longitude-latitude plane with a grid spacing of 45 • in longitude and 15 • in latitude. For AR samples in each of the defined HRs, we calculate the degree of HSP compliance and the average soft X-ray flare index. The strongest flaring activity is found to be in one distinctive HR with an extremely low HSP compliance of 41% as compared to the mean and standard deviation of 62% and 7%, respectively, over all HRs. This sole HR shows an anti-HSP (i.e., < 50%) and includes the highly flareproductive AR NOAA 12673, however this AR is not uniquely responsible for the HR's low HSP. We also find that all HRs with the highest flaring activity are located in the southern hemisphere, and they tend to have lower degrees of HSP compliance. These findings point to the presence of localized regions of the convection zone with enhanced turbulence, imparting a greater magnetic complexity and a higher flaring rate to some rising magnetic flux tubes.

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“…Observational interpretation can be found in, e.g., [46]. Later methods for the observational identification of magnetic helicity [47], hydrodynamic helicity [48] and even their joint contribution to the α-effect [49,50] have been suggested. There are many remaining problems, however the direction of development is clear.…”

Section: Quantifying Dynamo Driversmentioning

confidence: 99%

Magnetic Fields Around Galactic Discs

Moss

Sokoloff

2019

Galaxies

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Magnetic fields in the discs of spiral galaxies are quite well understood, although, of course, many details still require investigation and future observations with new generations of radio telescopes will be valuable here. Magnetic configurations around galactic discs and, in particular, the magnetic field components perpendicular to galactic discs seem to be much more poorly understood and deserve further investigation both observationally and by modelling. Another problem to be addressed in future investigations is the magnetic configuration in galactic halos and, in particular, interactions with the intergalactic medium and various winds. Finally, the importance of the observational determination of such drivers of galactic dynamo action as mirror asymmetry of the turbulent galactic flows are briefly discussed.

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Current and Kinetic Helicity of Long-Lived Activity Complexes

Cited by 22 publications

References 33 publications

Magnetic and Velocity Field Topology in Active Regions of Descending Phase of the Solar Cycle 23

Magnetic and Velocity Field Topology in Active Regions of Descending Phase of the Solar Cycle 23

Magnetic Helicity Flux across Solar Active Region Photospheres: II. Association of Hemispheric Sign Preference with Flaring Activity during Solar Cycle 24

Magnetic Fields Around Galactic Discs

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