Allen Telescope Array Multi-frequency Observations of the Sun

Saint-Hilaire, Pascal; Hurford, G. J.; Keating, Garrett K.; Bower, Geoffrey C.; Gutierrez-Kraybill, Colby

doi:10.1007/s11207-011-9906-3

Cited by 10 publications

(6 citation statements)

References 16 publications

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“…7, left panel) are in good accordance with the literature in the radio domain (e.g. Saint-Hilaire et al 2012;Ramesh et al 2020). A coronal analysis of the Sun (Chiuderi Drago et al 1999) -assuming hydrostatic equilibrium and using EUV and radio data -shows an electron density derived at the base of the corona (h A123, page 8 of 12 35 mm) N e (0) 3 × 10 8 cm −3 , in good accordance (within 3σ) with our results (N e (0)…”

Section: Discussionsupporting

confidence: 90%

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Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Marongiu,

Pellizzoni,

Righini

et al. 2024

A&A

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One of the most important objectives of solar physics is to gain a physical understanding of the solar atmosphere, whose structure can also be described in terms of the density ($N$) and temperature ($T$) distributions of the atmospheric matter. Several multi-frequency analyses have shown that the characteristics of these distributions are still under debate, especially for outer coronal emission. We aim to constrain the $T$ and $N$ distributions of the solar atmosphere through observations in the centimetric radio domain. We employed single-dish observations from two of the INAF radio telescopes at the K-band frequencies ($18$ -- $26$ GHz). We investigated the origin of the significant brightness temperature ($T_B$) detected up to the upper corona (at an altitude of $ 800$ Mm with respect to the photospheric solar surface). To probe the physical origin of the atmospheric emission and to constrain instrumental biases, we reproduced the solar signal by convolving specific 2D antenna beam models. We performed an analysis of the solar atmosphere by adopting a physical model that assumes the thermal bremsstrahlung as the emission mechanism, with specific $T$ and $N$ distributions. We compared the modelled $T_B$ profiles with those observed by averaging solar maps obtained at $18.3$ and $25.8$ GHz during the minimum of solar activity (2018 -- 2020). We probed any possible discrepancies between the $T$ and $N$ distributions assumed from the model and those derived from our measurements. The $T$ and $N$ distributions are compatible (within a $25<!PCT!>$ of uncertainty) with the model up to $ 60$ Mm and $ 100$ Mm in altitude respectively. Our analysis of the role of the antenna beam pattern on our solar maps proves the physical nature of the atmospheric emission in our images up to the coronal tails seen in our $T_B$ profiles. Our results suggest that the modelled $T$ and $N$ distributions are in good agreement (within $25<!PCT!>$ of uncertainty) with our solar maps up to altitudes of $ Mm. A subsequent, more challenging analysis of the coronal radio emission at higher altitudes, together with the data from satellite instruments, will require further multi-frequency measurements.

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Section: Discussionsupporting

confidence: 90%

“…The comparison between the theoretical and the observed data is crucial to improve the modelling of the solar corona and, hence, to better understand the atmospheric structures in terms of density and temperature (e.g. Saint-Hilaire et al 2012;Mercier & Chambe 2015;Vocks et al 2018;Ramesh et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Marongiu,

Pellizzoni,

Righini

et al. 2024

A&A

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“…Several articles in the literature report observations of limb brightening at high frequencies from 33 to 860 GHz (see a compilation of these results in Selhorst et al 2003). Moreover, this increase of temperature at the limb is also observed at lower radio frequencies due to the optically thin solar corona (Saint-Hilaire et al 2012). Observations of limb brightening at multiple frequencies could help to model the temperature variations in the stellar atmosphere.…”

Section: Discussionmentioning

confidence: 95%

Planetary Transits With the Atacama Large Millimeter/Submillimeter Array Radio Interferometer

Selhorst

Barbosa

Válio

2013

ApJ

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Planetary transits are commonly observed at visible wavelengths. Here we investigate the shape of a planetary transit observed at radio wavelengths. Solar maps of the Sun at 17 GHz are used as a proxy for the stellar eclipse by several sizes of planets from Super-Earths to Hot Jupiters. The relative depth at mid transit is the same as observed at visible wavelengths, but the limb brightening of the stellar disk at 17 GHz is clearly seen in the shape of the transit light curve. Moreover, when the planet occults an active region the depth of the transit decreases even further, depending on the brightness of the active region relative to the surrounding disk. For intense active region, with 50 times the brightness temperature of the surrounding disk, the decrease can supersede the unperturbed transit depth depending on the size of the eclipsing planet. For a Super-Earth (R p = 0.02R s ) crossing, the decrease in intensity is 0.04%, increasing to 0.86% in the case when a strong active region is present. On the other hand, for a hot Jupiter with R p = 0.17R s , the unperturbed transit depth is 3% increasing to 4.7% when covering this strong active region. This kind of behavior can be verified with observation of planetary transits with the ALMA radio interferometer.

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“…The benefit of using magnetic flux transport with global solar magnetic maps is that we can move away from an empirical model toward a physics‐based model for forecasting F 10.7 [e.g., Lionello et al , 2009]. Ultimately, daily spatially resolved F 10.7 observations [see Saint‐Hilaire et al , 2012] would permit long‐term feedback and refinement of flux transport models like ADAPT.…”

Section: Near‐future Goals and Improvementsmentioning

confidence: 99%

Forecasting F_10.7 with solar magnetic flux transport modeling

et al. 2012

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1] A new method is presented here to forecast the solar 10.7 cm (2.8 GHz) radio flux, abbreviated F 10.7 , utilizing advanced predictions of the global solar magnetic field generated by a flux transport model. Using indices derived from the absolute value of the solar magnetic field, we find good correlation between the observed photospheric magnetic activity and the observed F 10.7 values. Comparing magnetogram data observed within 6 hours of the F 10.7 measurements during the years 1993 through 2010, the Spearman correlation coefficient, r s , for an empirical model of F 10.7 is found to be 0.98. In addition, we find little change in the empirical model coefficients and correlations between the first and second 9 year intervals of the 18 year period investigated. By evolving solar magnetic synoptic maps forward 1-7 days, this new method provides a realistic estimation of the Earth-side solar magnetic field distribution used to forecast F 10.7 . Spearman correlation values of approximately 0.97, 0.95, and 0.93 are found for 1 day, 3 day, and 7 day forecasts, respectively. The method presented here can be expanded to forecast other space weather parameters, e.g., total solar irradiance and extreme ultraviolet flux. In addition, near-term improvements to the F 10.7 forecasting method, e.g., including far-side magnetic data with solar magnetic flux transport, are discussed.

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Allen Telescope Array Multi-frequency Observations of the Sun

Cited by 10 publications

References 16 publications

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Planetary Transits With the Atacama Large Millimeter/Submillimeter Array Radio Interferometer

Forecasting F_10.7 with solar magnetic flux transport modeling

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Allen Telescope Array Multi-frequency Observations of the Sun

Cited by 10 publications

References 16 publications

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Planetary Transits With the Atacama Large Millimeter/Submillimeter Array Radio Interferometer

Forecasting F10.7 with solar magnetic flux transport modeling

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Forecasting F_10.7 with solar magnetic flux transport modeling