Dynamics of solar mesogranulation

Leitzinger, M.; Brandt, Peter; Hanslmeier, A.; Pötzi, W.; Hirzberger, J.

doi:10.1051/0004-6361:20053152

Cited by 16 publications

(18 citation statements)

References 23 publications

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“…The exponential distribution corresponds to a memoryless random process, which means that the probability for a mesogranule to disappear (by splitting or dissolving) is constant (i.e., independent of its age). Similar exponential distributions of the mesogranule properties were found by Leitzinger et al (2005) when analysing the LCT velocity divergence obtained from the SOHO/MIDI instrument.…”

Section: Intergranular Lane Agesupporting

confidence: 77%

“…The pattern in Fig. 16 is similar to the mesogranulation images obtained from observations and numerical simulations, with regular cell-like structures (November et al 1981;November 1989;Muller et al 1992;Roudier et al 1998;Ueno et al 1998 ;Shine et al 2000;Cattaneo et al 2001;Roudier et al 2004;Leitzinger et al 2005).…”

Section: Horizontal Velocity Divergence Areassupporting

confidence: 76%

“…One way to detect mesogranulation in observational data is by means of "corks", artificial test particles which are passively advected by the horizontal flow as determined by local correlation tracking of intensity features (Simon & Weiss 1989;Shine et al 2000;Leitzinger et al 2005). The corks tend to gather in the long-lived intergranular downflow lanes, which represent places of horizontal velocity convergence.…”

Section: Definitionmentioning

confidence: 99%

“…3, we define the mesogranular pattern by considering the age of intergranular lanes. The age is taken as a measure of the number of "corks" they would accumulate in the observational "cork method" based on horizontal motions detected by local correlation tracking (Simon & Weiss 1989;Leitzinger et al 2005). The idea is the following: the corks tend to gather in the long-lived intergranular lanes, which mark places of horizontal velocity convergence (downflows).…”

Section: Mesogranulationmentioning

confidence: 99%

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Modelling of solar mesogranulation

Matloch

Cameron

Schmitt

et al. 2009

A&A

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We study whether mesogranulation flow patterns at the solar surface can arise solely from the statistical properties of granules and intergranular lanes. We have developed one-and two-dimensional models with local interaction rules between the artificial "granules" mimicking the actual physical processes on the solar surface. Defining mesogranulation according to the age of intergranular (downflow) lanes corresponding to the often applied "cork method", as well as the areas of divergence of the horizontal velocity (two-dimensional model), we find that mesogranular patterns are present in our models. Our study of the dependence of the properties of the mesogranular patterns on the model parameter and interaction rules reveals that the patterns do not possess intrinsic length and time scales.

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Section: Intergranular Lane Agesupporting

confidence: 77%

Section: Horizontal Velocity Divergence Areassupporting

confidence: 76%

Section: Definitionmentioning

confidence: 99%

Section: Mesogranulationmentioning

confidence: 99%

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Modelling of solar mesogranulation

Matloch

Cameron

Schmitt

et al. 2009

A&A

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“…The v s obtained in our investigation is also in good agreement with that of Del Moro et al (2007), who found a horizontal flow speed of 0.75 ± 0.05 km s −1 inside a supergranule via cork tracking. Our determined systematic velocity is, however, slightly larger than the mean horizontal flow velocity of ≈0.4 km s −1 within supergranules, reported by Title et al (1989), Wang et al (1995), and Hathaway et al (2002) and the ≈0.3 km s −1 reported for mesogranular flows by Leitzinger et al (2005).…”

Section: Migration Of Mbps Over a Supergranulecontrasting

confidence: 73%

Migration of Ca II H bright points in the internetwork

Jafarzadeh

Cameron

Solanki

et al. 2014

A&A

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Context. The migration of magnetic bright point-like features (MBP) in the lower solar atmosphere reflects the dispersal of magnetic flux as well as the horizontal flows of the atmospheric layer they are embedded in.Aims. We analyse trajectories of the proper motion of intrinsically magnetic, isolated internetwork Ca ii H MBPs (mean lifetime 461± 9 s) to obtain their diffusivity behaviour. Methods. We use seeing-free high spatial and temporal resolution image sequences of quiet-Sun, disc-centre observations obtained in the Ca ii H 3968 Å passband of the Sunrise Filter Imager (SuFI) onboard the Sunrise balloon-borne solar observatory. Small MBPs in the internetwork are automatically tracked. The trajectory of each MBP is then calculated and described by a diffusion index (γ) and a diffusion coefficient (D). We also explore the distribution of the diffusion indices with the help of a Monte Carlo simulation. Results. We find γ = 1.69 ± 0.08 and D = 257 ± 32 km 2 s −1 averaged over all MBPs. Trajectories of most MBPs are classified as super-diffusive, i.e. γ > 1, with the determined γ being the largest obtained so far to our knowledge. A direct correlation between D and timescale (τ) determined from trajectories of all MBPs is also obtained. We discuss a simple scenario to explain the diffusivity of the observed, relatively short-lived MBPs while they migrate within a small area in a supergranule (i.e. an internetwork area). We show that the scatter in the γ values obtained for individual MBPs is due to their limited lifetimes. Conclusions. The super-diffusive MBPs can be described as random walkers (due to granular evolution and intergranular turbulence) superposed on a large systematic (background) velocity, caused by granular, mesogranular, and supergranular flows.

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Structure and Evolution of Supergranulation from Local Helioseismology

Hirzberger¹,

Gizon²,

Solanki³

et al. 2008

Helioseismology, Asteroseismology, and MHD Connections

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Supergranulation is visible at the solar surface as a cellular pattern of horizontal outflows. Although it does not show a distinct intensity pattern, it manifests itself indirectly in, for example, the chromospheric network. Previous studies have reported significant differences in the inferred basic parameters of the supergranulation phenomenon. Here we study the structure and temporal evolution of a large sample of supergranules, measured by using local helioseismology and SOHO/MDI data from the year 2000 at solar activity minimum. Local helioseismology with f modes provides maps of the horizontal divergence of the flow velocity at a depth of about 1 Mm. From these divergence maps supergranular cells were identified by using Fourier segmentation procedures in two dimensions and in three dimensions (two spatial dimensions plus time). The maps that we analyzed contain more than 10 5 supergranular cells and more than 10 3 lifetime histories, which makes possible a detailed analysis with high statistical significance. We find that the supergranular cells have a mean diameter of 27.1 Mm. The mean lifetime is estimated to be 1.6 days from the measured distribution of lifetimes (three-dimensional segmentation), with a clear tendency for larger cells to live longer than smaller ones. The pair and mark correlation functions do not show pronounced features on scales larger than the typical cell size, which suggests purely random cell positions. The temporal histories of supergranular cells indicate a smooth evolution from their emergence and growth in the first half of their lives to their decay in the second half of their lives (unlike exploding granules, which reach their maximum size just before they fragment).

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Dynamics of solar mesogranulation

Cited by 16 publications

References 23 publications

Modelling of solar mesogranulation

Modelling of solar mesogranulation

Migration of Ca II H bright points in the internetwork

Structure and Evolution of Supergranulation from Local Helioseismology

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