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We describe the computational techniques employed in the recently updated Fourier local correlation tracking (FLCT) method. The FLCT code is then evaluated using a series of simple, 2D, known flow patterns that test its accuracy and…

Astrophysics · Physics 2007-12-31 G. H. Fisher , B. T. Welsch

X-ray photon correlation spectroscopy (XPCS) allows for the resolution of dynamic processes within a material across a wide range of length and time scales. X-ray speckle visibility spectroscopy (XSVS) is a related method that uses a single…

Numerical Analysis · Mathematics 2023-01-09 Shaswat Mohanty , Christopher B. Cooper , Hui Wang , Mengning Liang , Wei Cai

Several lines of evidence suggest that the velocity amplitude in global simulations of solar convection, U, may be systematically over-estimated. Motivated by these recent results, we explore the factors that determine U and we consider how…

Solar and Stellar Astrophysics · Physics 2016-09-21 Bridget O'Mara , Mark S. Miesch , Nicholas A. Featherstone , K. C. Augustson

Downflows on the solar surface are suspected to play a major role in the dynamics of the convection zone. We investigate the existence of the long-lasting downflows whose effects influence the interior of the Sun and the outer layers. We…

Solar and Stellar Astrophysics · Physics 2021-03-05 T. Roudier , M. Švanda , J. M. Malherbe , J. Ballot , D. Korda , Z. Frank

We developed an automated method for sunspot detection using digital white-light solar images to achieve a performance similar to that of visual drawing observations in sunspot counting. To identify down to small, isolated spots correctly,…

Solar and Stellar Astrophysics · Physics 2022-12-05 Yoichiro Hanaoka

Magnetic features on the surfaces of cool stars cause variations of their brightness. Such variations have been extensively studied for the Sun. Recent planet-hunting space telescopes allowed measuring brightness variations in hundred…

Solar and Stellar Astrophysics · Physics 2020-04-15 N. -E. Nèmec , A. I. Shapiro , N. A. Krivova , S. K. Solanki , R. V. Tagirov , R. H. Cameron , S. Dreizler

Interpreting spectropolarimetric observations of the solar atmosphere takes much longer than the acquiring the data. The most important reason for this is that the model fitting, or "inversion", used to infer physical quantities from the…

Solar and Stellar Astrophysics · Physics 2020-12-16 Ivan Milic , Ricardo Gafeira

The methods for reducing the observations from the 150-foot Tower Telescope on Mt.~Wilson are reviewed and a new method for determining the North/South (sectoral) and the East/West (zonal) velocity components is described and applied. Due…

Solar and Stellar Astrophysics · Physics 2023-07-14 Roger K. Ulrich , Tham Tran , John Boyden

We study performance characteristics of convolutional neural networks (CNN) for mobile computer vision systems. CNNs have proven to be a powerful and efficient approach to implement such systems. However, the system performance depends…

Computer Vision and Pattern Recognition · Computer Science 2018-03-28 Jussi Hanhirova , Teemu Kämäräinen , Sipi Seppälä , Matti Siekkinen , Vesa Hirvisalo , Antti Ylä-Jääski

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

A reconnecting current layer is a `heart' of a solar flare, because it is a place of magnetic-field energy release. However there are no direct observations of these layers. The aim of our work is to understand why we actually do not…

Solar and Stellar Astrophysics · Physics 2014-04-18 A. V. Oreshina , I. V. Oreshina

It has long been known that the high-speed stream (HSS) peak velocity at Earth directly depends on the area of the coronal hole (CH) on the Sun. Different degrees of association between the two parameters have been shown by many authors. In…

One of the main obstacles in exoplanet detection when using the radial velocity (RV) technique is the presence of stellar activity signal induced by magnetic regions. In this context, a realistic simulated dataset that can provide…

Solar and Stellar Astrophysics · Physics 2025-01-29 Yinan Zhao , Xavier Dumusque , Michael Cretignier , Khaled Al Moulla , Momo Ellwarth , Ansgar Reiners , Alessandro Sozzetti

The occlusion of the sun by clouds is one of the primary sources of uncertainties in solar power generation, and is a factor that affects the wide-spread use of solar power as a primary energy source. Real-time forecasting of cloud movement…

Computer Vision and Pattern Recognition · Computer Science 2024-09-19 Leron Julian , Haejoon Lee , Soummya Kar , Aswin C. Sankaranarayanan

We carry out an unprecedented high-resolution simulation for the solar convection zone. Our calculation reproduces the fast equator and near-surface shear layer (NSSL) of differential rotation and the near-surface poleward meridional flow…

Solar and Stellar Astrophysics · Physics 2025-04-09 H. Hotta

Global climate models (GCMs), typically run at ~100-km resolution, capture large-scale environmental conditions but cannot resolve convection and cloud processes at kilometer scales. Convection-permitting models offer higher-resolution…

Atmospheric and Oceanic Physics · Physics 2026-05-12 Hungjui Yu , Lander Ver Hoef , Kristen L. Rasmussen , Imme Ebert-Uphoff

Photometric variability detection is often considered as a hypothesis testing problem: an object is variable if the null-hypothesis that its brightness is constant can be ruled out given the measurements and their uncertainties. Uncorrected…

Instrumentation and Methods for Astrophysics · Physics 2018-01-25 Ilya N. Pashchenko , Kirill V. Sokolovsky , Panagiotis Gavras

A saliency guided hierarchical visual tracking (SHT) algorithm containing global and local search phases is proposed in this paper. In global search, a top-down saliency model is novelly developed to handle abrupt motion and appearance…

Computer Vision and Pattern Recognition · Computer Science 2018-12-24 Fangwen Tu , Shuzhi Sam Ge , Yazhe Tang , Chang Chieh Hang

Spectral analysis of the spatial structure of solar subphotospheric convection is carried out for subsurface flow maps constructed using the time--distance helioseismological technique. The source data are obtained from the Helioseismic and…

Solar and Stellar Astrophysics · Physics 2022-09-27 Alexander V. Getling , Alexander G. Kosovichev

Large scale flows in the Sun play an important role in the dynamo process linked to the solar cycle. The important large scale flows are the differential rotation and the meridional circulation with an amplitude of km/s and few m/s ,…

Solar and Stellar Astrophysics · Physics 2018-04-25 Th. Roudier , M. Svanda , J. Ballot , J. M. Malherbe , M. Rieutord