Emerging Active Regions Studied with Ring‐Diagram Analysis

Komm, R.; Morita, Shinichi; Howe, R.; Hill, F.

doi:10.1086/523998

Cited by 32 publications

(35 citation statements)

References 12 publications

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“…This "moat" of flow has also been observed helioseismically (Lindsey et al 1996;Gizon et al 2000;Braun & Lindsey 2003). Related outflows have also been observed surrounding newly emerged active regions that have yet to fray and form a region of extended plage (Hindman et al 2006b;Komm et al 2008;Kosovichev & Duvall 2008). Figure 2 shows the flows around an active region that emerged just two days prior.…”

Section: Introductionmentioning

confidence: 94%

Subsurface Circulations Within Active Regions

Hindman¹,

Haber²,

Toomre³

2009

ApJ

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Using high-resolution ring analysis (HRRA) we deduce subsurface flows within magnetic active regions and within quiet sun. With this procedure we are capable of measuring flows with a horizontal spatial resolution of 2• in heliographic angle (or roughly 20 Mm). From the resulting flow fields we deduce mean inflow rates into active regions, mean circulation speeds around active regions, and probability density functions (PDFs) of properties of the flow field. These analyses indicate that active regions have a zonal velocity that exceeds that of quiet sun at the same latitude by 20 m s −1 , yet active regions advect poleward at the same rate as quiet sun. We also find that almost all active regions possess a mean inflow (20-30 m s −1 ) and a cyclonic circulation (≈ 5 m s −1 ) at their peripheries, whereas their cores, where the sunspots are located, are zones of strong anticyclonic outflow (≈ 50 m s −1 ). From the PDFs, we find that active regions modify the structure of convection with a scale greater than that of supergranulation. Instead of possessing an asymmetry between inflows and outflows (with a larger percentage of the surface occupied by outflows), as is seen in quiet sun, active regions possess symmetric distributions.

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Section: Introductionmentioning

confidence: 94%

Subsurface Circulations Within Active Regions

Hindman¹,

Haber²,

Toomre³

2009

ApJ

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“…The ring-diagram method has provided important results about the structure and evolution of large-scale and meridional flows and dynamics of active regions (Haber et al, 2000(Haber et al, , 2002Howe, 2008;Komm et al, 2008). In particular, large-scale patterns of subsurface flows converging around magnetic active regions were discovered Haber et al (2004).…”

Section: Time-distance Helioseismologymentioning

confidence: 99%

Local Helioseismology of Sunspots: Current Status and Perspectives

Kosovichev

2012

Sol Phys

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Mechanisms of the formation and stability of sunspots are among the longeststanding and intriguing puzzles of solar physics and astrophysics. Sunspots are controlled by subsurface dynamics hidden from direct observations. Recently, substantial progress in our understanding of the physics of the turbulent magnetized plasma in strong-field regions has been made by using numerical simulations and local helioseismology. Both the simulations and helioseismic measurements are extremely challenging, but it becomes clear that the key to understanding the enigma of sunspots is a synergy between models and observations. Recent observations and radiative MHD numerical models have provided a convincing explanation to the Evershed flows in sunspot penumbrae. Also, they lead to the understanding of sunspots as self-organized magnetic structures in the turbulent plasma of the upper convection zone, which are maintained by a large-scale dynamics. Local helioseismic diagnostics of sunspots still have many uncertainties, some of which are discussed in this review. However, there have been significant achievements in resolving these uncertainties, verifying the basic results by new high-resolution observations, testing the helioseismic techniques by numerical simulations, and comparing results obtained by different methods. For instance, a recent analysis of helioseismology data from the Hinode space mission has successfully resolved several uncertainties and concerns (such as the inclined-field and phase-speed filtering effects) that might affect the inferences of the subsurface wave-speed structure of sunspots and the flow pattern. It becomes clear that for the understanding of the phenomenon of sunspots it is important to further improve the helioseismology methods and investigate the whole life cycle of active regions, from magnetic-flux emergence to dissipation. The Solar Dynamics Observatory mission has started to provide data for such investigations.

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“…Employing ring-diagram analysis of GONG data for 13 new or growing active regions (and contrasting with control areas), Komm et al (2008) found evidence for upflows prior to the appearance of emerging flux at the surface, followed by a transition to predominantly downflows once the active region was established.…”

Section: Introductionmentioning

confidence: 99%

Helioseismology of Pre-Emerging Active Regions. I. Overview, Data, and Target Selection Criteria

Leka

Barnes

Birch

et al. 2012

ApJ

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This first paper in a series describes the design of a study testing whether pre-appearance signatures of solar magnetic active regions were detectable using various tools of local helioseismology. The ultimate goal is to understand fluxemergence mechanisms by setting observational constraints on pre-appearance subsurface changes, for comparison with results from simulation efforts. This first paper provides details of the data selection and preparation of the samples, each containing over 100 members, of two populations: regions on the Sun that produced a numbered NOAA active region, and a "control" sample of areas that did not. The seismology is performed on data from the GONG network; accompanying magnetic data from SOHO/MDI are used for co-temporal analysis of the surface magnetic field. Samples are drawn from [2001][2002][2003][2004][2005][2006][2007], and each target is analyzed for 27.7 hr prior to an objectively determined time of emergence. The results of two analysis approaches are published separately: one based on averages of the seismology-and magnetic-derived signals over the samples, another based on Discriminant Analysis of these signals, for a statistical test of detectable differences between the two populations. We include here descriptions of a new potential-field calculation approach and the algorithm for matching sample distributions over multiple variables. We describe known sources of bias and the approaches used to mitigate them. We also describe unexpected bias sources uncovered during the course of the study and include a discussion of refinements that should be included in future work on this topic.

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Emerging Active Regions Studied with Ring‐Diagram Analysis

Cited by 32 publications

References 12 publications

Subsurface Circulations Within Active Regions

Subsurface Circulations Within Active Regions

Local Helioseismology of Sunspots: Current Status and Perspectives

Helioseismology of Pre-Emerging Active Regions. I. Overview, Data, and Target Selection Criteria

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