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Robust sensing and perception in adverse weather conditions remain one of the biggest challenges for realizing reliable autonomous vehicle mobility services. Prior work has established that rainfall rate is a useful measure for the…

Signal Processing · Electrical Eng. & Systems 2022-04-26 Robin Karlsson , David Robert Wong , Kazunari Kawabata , Simon Thompson , Naoki Sakai

Despite recent major advances, the opacity remains a source of substantial uncertainty in the calculation of solar models, and hence of solar oscillation frequencies. Hence it is of substantial interest to investigate the sensitivity of…

Astrophysics · Physics 2009-09-25 S. C. Tripathy , J. Christensen-Dalsgaard

Treatments of the radio scattering due to density turbulence in the solar wind typically employ asymptotic approximations to the phase structure function. We use a general structure function (GSF) that straddles the asymptotic limits and…

Solar and Stellar Astrophysics · Physics 2015-09-28 Madhusudan Ingale

Primary inversions of accurately measured solar oscillation frequencies coupled with the equations of thermal equilibrium and other input physics, enable us to infer the temperature and hydrogen abundance profiles inside the Sun. These…

Astrophysics · Physics 2009-11-07 H. M. Antia , S. M. Chitre

Context. The most recent determination of the solar chemical composition, using a time-dependent, 3D hydrodynamical model of the solar atmosphere, exhibits a significant decrease of C, N, O abundances compared to their previous values.…

Astrophysics · Physics 2011-03-28 A. Zaatri , J. Provost , G. Berthomieu , P. Morel , T. Corbard

Asteroseismic modelling is crucial for upcoming missions like PLATO, CubeSpec, and Roman. Despite significant progress, discrepancies between observations and theoretical predictions introduce biases in stellar characterisation at the…

Perturbation theory is used to calculate the frequency shift of acoustic modes of an homogeneous turbulent fluid and the frequency shifts of solar modes due to turbulent convection. For sound waves in a random flow, the fractional frequency…

Astrophysics · Physics 2009-10-30 Andrei V. Gruzinov

While it has been relatively easy to determine solar-cycle related changes in solar dynamics, determining changes in structure in the deeper layers of the Sun has proved to be difficult. By using helioseismic data obtained over two solar…

Solar and Stellar Astrophysics · Physics 2021-08-25 Sarbani Basu

Inhomogeneities in wave propagation conditions near and below the solar surface have been detected by means of time-distance helioseismology. Here we calculate the effect of temperature inhomogeneities on the travel times of sound waves. A…

Astrophysics · Physics 2015-06-24 M. Brüggen , H. C. Spruit

We have used 4752 days of data collected by the Birmingham Solar-Oscillations Network (BiSON) to determine very precise oscillation frequencies of acoustic low-degree modes that probe the solar core. We compare the fine (small frequency)…

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

Studying solar wind conditions is central to forecasting impact of space weather on Earth. Under the assumption that the structure of this wind is constant in time and corotates with the Sun, solar wind and thereby space weather forecasts…

Solar and Stellar Astrophysics · Physics 2023-01-30 Nachiketa Chakraborty , Harriet Turner , Mathew Owens , Matthew Lang

Solar wind properties are determined by the conditions of their solar source region and transport history. Solar wind parameters, such as proton speed, proton density, proton temperature, magnetic field strength, and the charge state…

Solar and Stellar Astrophysics · Physics 2023-10-11 Maximilian Hecht , Verena Heidrich-Meisner , Lars Berger , Robert F. Wimmer-Schweingruber

Normal-mode helioseismic data analysis uses observed solar oscillation spectra to infer perturbations in the solar interior due to global and local-scale flows and structural asphericity. Differential rotation, the dominant global-scale…

Solar and Stellar Astrophysics · Physics 2021-03-30 Samarth G. Kashyap , Srijan Bharati Das , Shravan M. Hanasoge , Martin F. Woodard , Jeroen Tromp

Observations of the Sun with the LOWL instrument provide a homogeneous set of solar p-mode frequencies from low to intermediate degree which allows one to determine the structure of much of the solar interior avoiding systematic errors that…

Aims: We develop a method for estimating the properties of stellar winds for low-mass main-sequence stars between masses of 0.4 and 1.1 solar masses at a range of distances from the star. Methods: We use 1D thermal pressure driven…

Solar and Stellar Astrophysics · Physics 2015-04-29 C. P. Johnstone , M. Güdel , T. Lüftinger , G. Toth , I. Brott

The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable…

The Sun is the most studied of all stars. It is a reference for all other observed stars and a laboratory of fundamental physics helping us understand processes occuring in conditions irreproducible on Earth. However, our understanding of…

We have investigated how the relative elemental abundances inferred from the solar upper atmosphere are affected by uncertainties in the dielectronic recombination (DR) rate coefficients used to analyze the spectra. We find that the…

Astrophysics · Physics 2007-05-23 Daniel Wolf Savin , J. Martin Laming

Several properties of the solar interior are determined with a very high accuracy, which in some cases is comparable to that achieved in the determination of the Newton constant $G_N$. We find that the present uncertainty $\Delta…

Astrophysics · Physics 2009-11-07 B. Ricci , F. L. Villante