arXiv subjects

Antonio Eff-Darwich

Publications and source records attributed to Antonio Eff-Darwich.

5 recordsLinked to original sources

arXiv2026

Focal-Plane Diagnostics of Atmospheric and Dome-Induced Turbulence: Exploring techniques and applications

Atmospheric turbulence remains the dominant source of image degradation in ground-based astronomy. Its impact depends not only on the integrated turbulence strength but also on the wavefront spatial-coherence outer scale (\LO) and on turbulence generated within the telescope enclosure (dome seeing). While seeing, coherence time, and related parameters are routinely monitored at major observatories, measurements of \LO\ and dome-induced turbulence remain sparse, limiting our ability to predict image quality and to construct accurate point-spread function (PSF) models. Building on methodology recently developed for seeing-limited integral-field spectroscopic (IFS) data, we present a series of complementary studies showing how spatial information encoded in standard observations can be used to diagnose both atmospheric and dome turbulence. We investigate the feasibility of extending these techniques beyond IFS observations to other seeing-limited instruments through the analysis of wavelength-dependent spatial profiles. We also present the development of data-driven three-dimensional PSF models based on atmospheric statistics for the reconstruction of seeing-limited IFS observations. These results show that widely available seeing-limited scientific observations, both from archival data and routine observatory operations, can provide meaningful and operationally useful constraints on key turbulence parameters and on the spectral behavior of dome seeing, complementing dedicated site-testing instrumentation. The resulting turbulence diagnostics have direct applications to PSF modelling, image reconstruction, image-quality prediction, and the optimization of future ELT operations.

astro-ph.IM↗

arXiv2026

Resolving the Tachocline using Inversion of Rotational Splitting Derived from Fitting Very Long and Long Time Series

We use rotation splittings derived from very long and long time series, namely 25.2, 12.6 and 6.3 year long, computed by Korzennik (2023) independent methodology to characterize the solar tachocline and its variation with latitude and time. We use two different inversion methodologies and a model of the tachocline to derive its position, width and the amplitude of the radial shear. To validate our methodology we present results from simulated rotational splittings, whether including or not random noise commensurable with the current observational precision. We also describe how we leverage the fact that one of our methodologies uses an initial guess that can be chosen to include a priori information. In order to try to resolve the tachocline, we increased the radial density of the inversion grid and showed how it affect the inferences. We also show how the trade off between smoothing and noise magnification affects these, as well as the effectiveness of using an informed initial guess. Results derived from high-precision rotational splittings show clearly that the location of the tachocline at low latitudes is different for its position at high latitudes. The latitudinal variation of its width is not significantly constrained, but our results agree with estimates based on forward modeling. When using splittings derived from somewhat shorter time series, we find temporal variations that are neither definitive nor significant, since we see systematic differences when using different methodologies.

astro-ph.SR↗

arXiv2024

A SART-Based Iterative Inversion Methodology to Infer the Solar Rotation Rate from Global Helioseismic Data

We present a new iterative rotation inversion technique based on the Simultaneous Algebraic Reconstruction Technique developed for image reconstruction. We describe in detail our algorithmic implementation and compare it to the classical inversion techniques like the Regularized Least Squares (RLS) and the Optimally Localized Averages (OLA) methods. In our implementation, we are able to estimate the formal uncertainty on the inferred solution using standard error propagation, and derive the averaging kernels without recourse to any Monte-Carlo simulation. We present the potential of this new technique using simulated rotational frequency splittings. We use noiseless sets that cover the range of observed modes and associate to these artificial splittings observational uncertainties. We also add random noise to present the noise magnification immunity of the method. Since the technique is iterative we also show its potential when using an apriori solution. With the right regularization this new method can outperform our RLS implementation in precision, scope and resolution. Since it results in very different averaging kernels where the solution is poorly constrained, this technique infers different values. Adding such a technique to our compendium of inversion methods will allow us to improve the robustness of our inferences when inverting real observations and better understand where they might be biased and/or unreliable, as we push our techniques to maximize the diagnostic potential of our observations.

astro-ph.SR↗

arXiv2012

The Dynamics of the Solar Radiative Zone

The dynamics of the solar radiative interior are still poorly constrained by comparison to the convective zone. This disparity is even more marked when we attempt to derive meaningful temporal variations. Many data sets contain a small number of modes that are sensitive to the inner layers of the Sun, but we found that the estimates of their uncertainties are often inaccurate. As a result, these data sets allow us to obtain, at best, a low resolution estimate of the solar core rotation rate down to approximately 0.2R. We present inferences based on mode determination resulting from an alternate peak-fitting methodology aimed at increasing the amount of observed modes that are sensitive to the radiative zone, while special care was taken in the determination of their uncertainties. This methodology has been applied to MDI and GONG data, for the whole Solar Cycle 23, and to the newly available HMI data. The numerical inversions of all these data sets result in the best inferences to date of the rotation in the radiative region. These results and the method used to obtain them are discussed. The resulting profiles are shown and analyzed, and the significance of the detected changes discussed.

astro-ph.SR↗

arXiv2011

The long term dynamics of the solar radiative zone associated to new results from SoHO and young solar analogs

The Standard Solar Model (SSM) is no more sufficient to interpret all the observations of the radiative zone obtained with the SoHO satellite. We recall our present knowledge of this internal region and compare the recent results to models beyond the SSM assumptions. Then we discuss the missing processes and quantify some of them in using young analog observations to build a more realistic view of our star. This progress will be useful for solar-like stars observed by COROT and KEPLER.

astro-ph.SR↗