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In the quiet region of the solar photosphere, turbulent convective motions of the granular flows naturally drive the subgranular-scale flows. However, evaluating such small-scale velocities is challenging because of the limited instrumental…

Solar and Stellar Astrophysics · Physics 2024-11-01 Ryohtaroh T. Ishikawa , Yukio Katsukawa

Observations of the solar surface reveal the presence of flows with length scales of around $35$ Mm, commonly referred to as supergranules. Inferring the sub-surface flow profile of supergranules from measurements of the surface and…

Solar and Stellar Astrophysics · Physics 2016-08-03 Jishnu Bhattacharya , Shravan M. Hanasoge

Exploding granules constitute the strongest horizontal flows on the quiet Sun and contribute to the structure of the surface horizontal velocity fields which build the large-scale organization of the discrete magnetic field. In this work we…

Solar and Stellar Astrophysics · Physics 2020-09-09 T. Roudier , J. M. Malherbe , B. Gelly , R. Douet , Z. Frank , K. Dalmasse

We investigated the vertical penumbral plasma flow on small spatial scales using data recorded by the spectropolarimeter of the solar optical telescope onboard Hinode. To this end we computed maps of apparent Doppler velocities by comparing…

Solar and Stellar Astrophysics · Physics 2015-05-14 Morten Franz , Rolf Schlichenmaier

We explore the general properties of near-surface flows around solar active regions. Helioseismic holography is applied to HMI Dopplergrams yielding nearly 5000 flow measurements of 336 unique active regions observed by the Solar Dynamics…

Solar and Stellar Astrophysics · Physics 2019-03-20 D. C. Braun

Meridional circulation regulates the Sun's interior dynamics and magnetism. While it is well accepted that meridional flows are poleward at the Sun's surface, helioseismic observations have yet to provide a definitive answer for the depth…

We perform helioseismic holography on realistic solar convection simulations and compare the observed travel-time perturbations with the expected travel times from the horizontal flows in the simulations computed from forward models under…

Astrophysics · Physics 2016-03-28 D. C. Braun , A. C. Birch , D. Benson , R. F. Stein , Å. Nordlund

Supergranulation is characterized by horizontally divergent flows with typical length scales of 32 Mm in the solar photosphere. Unlike granulation, the size of which is comparable to both the thickness of the radiative boundary layer and…

Solar and Stellar Astrophysics · Physics 2016-10-05 Jean-Francois Cossette , Mark Peter Rast

We compare horizontal velocities, vertical magnetic fields and evolution of trees of fragmenting granules (TFG, also named families of granules) derived in the quiet Sun at disk center from observations at solar minimum and maximum of the…

Solar and Stellar Astrophysics · Physics 2018-04-11 J. M. Malherbe , T. Roudier , R. Stein , Z. Frank

Recent observations from Parker Solar Probe have revealed that the solar wind has a highly variable structure. How this complex behaviour is formed in the solar corona is not yet known, since it requires omnipresent fluctuations, which…

Outflows of plasma at the edges of active regions surrounded by quiet Sun are now a common observation with the Hinode satellite. While there is observational evidence to suggest that the outflows are originating in the magnetic field…

Solar and Stellar Astrophysics · Physics 2015-05-14 M. J. Murray , D. Baker , L. van Driel-Gesztelyi , J. Sun

Results of forward modelling of acoustic wave propagation in a realistic solar sub-photosphere with two cases of steady horizontal flows are presented and analysed by the means of local helioseismology. The simulations are based on fully…

Astrophysics · Physics 2009-11-13 S. Shelyag , R. Erdelyi , M. J. Thompson

We report the discovery of supersonic downflows in a sunspot light bridge using measurements taken with the spectropolarimeter on board the Hinode satellite. The downflows occur in small patches close to regions where the vector magnetic…

Solar and Stellar Astrophysics · Physics 2015-05-14 Rohan Eugene Louis , Luis R. Bellot Rubio , Shibu K. Mathew , P. Venkatakrishnan

We report on a new phenomenon of `alignment' of supergranulation cells in the polar regions of the Sun. Recent high-resolution datasets obtained by the Solar Optical Telescope onboard the Hinode satellite enabled us to investigate…

Solar and Stellar Astrophysics · Physics 2010-12-20 Kaori Nagashima , Junwei Zhao , Alexander G. Kosovichev , Takashi Sekii

The meridional flow in the Sun is an axisymmetric flow that is generally poleward directed at the surface, and is presumed to be of fundamental importance in the generation and transport of magnetic fields. Its true shape and strength,…

Solar and Stellar Astrophysics · Physics 2015-06-11 Thomas Hartlep , Junwei Zhao , Alexander G. Kosovichev , Nagi N. Mansour

We model the solar horizontal velocity power spectrum at scales larger than granulation using a two-component approximation to the mass continuity equation. The model takes four times the density scale height as the integral (driving) scale…

Solar and Stellar Astrophysics · Physics 2015-06-22 J. W. Lord , R. H. Cameron , M. P. Rast , M. Rempel , T. Roudier

Light bridges are the most prominent manifestation of convection in sunspots. The brightest representatives are granular light bridges composed of features that appear to be similar to granules. An in-depth study of the convective motions,…

Solar and Stellar Astrophysics · Physics 2014-09-05 Andreas Lagg , Sami K. Solanki , Michiel van Noort , Sanja Danilovic

Persistent outflows have recently been detected at boundaries of some active regions. Although these outflows are suggested to be possible sources of the slow solar wind, the nature of these outflows is poorly understood. Through an…

Solar and Stellar Astrophysics · Physics 2015-05-19 L. -J. Guo , H. Tian , J. -S. He

We describe a new form of small-scale magnetic flux emergence in the quiet Sun. This process seems to take vertical magnetic fields from the solar interior to the photosphere, where they appear above granular convection cells. High-cadence…

Astrophysics · Physics 2009-11-13 D. Orozco Suarez , L. R. Bellot Rubio , J. C. del Toro Iniesta , S. Tsuneta

Measurements of the large cellular flows on the Sun were made by local correlation tracking of supergranules seen in full-disk Doppler images obtained by the HMI instrument on the NASA SDO satellite. The hourly measurements were averaged…

Solar and Stellar Astrophysics · Physics 2021-02-24 David H. Hathaway , Lisa A. Upton