Radio observations of the quiet sun and their implications on coronal heating

Alissandrakis, C. E.; Einaudi, G.

doi:10.1007/bfb0106451

Cited by 4 publications

(4 citation statements)

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“…As a matter of fact, we have plenty of negative answers. It is encouraging that there is sufficient energy associated with the granulation noise, as already pointed out by Schatzman (1949) and also in the random motion of magnetic flux tubes (Alissandrakis and Einaudi, 1997;Klimchuk, 2006), but this is not enough, as pointed up above, since this energy must be directed to the right place at the right time. Nanoflare heating is certainly attractive, but it evades observational confirmation so far.…”

Section: The Problemmentioning

confidence: 56%

“…We will now summarize radio observations that might have a bearing to the heating problem (see also Einaudi, 1997 andShibasaki et al, 2011). Radio fine structures show time variability comparable to that of the chromospheric network, on time scales of minutes to hours (Erskine and Kundu, 1982;Bastian et al, 1996).…”

Section: Pertinent Radio Datamentioning

confidence: 99%

“…More details can be found in a number of monographs on the Sun (Kuiper, 1953;Zirin, 1966Zirin, , 1988Priest, 1987Priest, , 2014Durrant, 1988;Foukal, 2004;Stix, 2004;Aschwanden, 2004;Engvold et al, 2019) and on solar radio astronomy (Kundu, 1965;Zheleznyakov, 1970;Krueger, 1979;McLean and Labrum, 1985;Gary and Keller, 2004). There are also reviews on the Quiet Sun radio emission that the reader might be interested in (Alissandrakis, 1994;Gary, 1996;Alissandrakis and Einaudi, 1997;Lantos, 1999;Shibasaki, 1999;Krucker, 2004 andShibasaki et al, 2011). Also of interest to the readers will be the reviews on Coherent Emission Mechanisms (Nindos, 2020) and on Radio Measurements of the Magnetic field (Alissandrakis and Gary, 2020), included in this special research topic collection.…”

Section: Introductionmentioning

confidence: 99%

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Structure of the Solar Atmosphere: A Radio Perspective

Alissandrakis

2020

Front. Astron. Space Sci.

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Solar radio emission has been providing information about the Sun for over half a century. In order to fully exploit this information, one needs to have a broader view of the solar atmosphere, which cannot be provided by radio observations alone. The purpose of this review is to present this background information, which is necessary to understand the physical processes that determine the solar radio emission and to link the radio domain with the rest of the electromagnetic spectrum. Both classic and modern results are presented in a concise manner. After a brief discussion of the solar interior, the basic physics of the solar atmosphere and some elements of radiative transfer are presented. Subsequently the atmospheric structure as a function of height is examined and one-dimensional models of the photosphere, the chromosphere, the transition region and the corona are presented and discussed. An introduction to basic magnetohydrodynamics precedes the discussion of the rich fine structure of the solar atmosphere as a 3D object. Active regions are briefly discussed in a separate section, and this is followed by a section on the problem of heating of the chromosphere and the corona. I finish with some thoughts on what to expect from the new instruments currently under development.

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Section: The Problemmentioning

confidence: 56%

Section: Pertinent Radio Datamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structure of the Solar Atmosphere: A Radio Perspective

Alissandrakis

2020

Front. Astron. Space Sci.

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“…Plasma processes -such as magnetic reconnection, shocks, and particle acceleration (e.g., Alissandrakis, 1994;Gary, 1996;Alissandrakis and Einaudi, 1997;Shibasaki, 1998;Shibasaki, Alissandrakis, and Pohjolainen, 2011;Messerotti, 2016;Nindos, 2020;Alissandrakis, 2020) -contribute to a complex and not fully understood radio emission picture. In this context, spatially-resolved and time-resolved radio data are crucial to complement the wealth of existing information in the UV, Optical, IR, and X-ray domains.…”

Section: Extended Author Information Available On the Last Page Of Th...mentioning

confidence: 99%

Solar Observations with Single-Dish INAF Radio Telescopes: Continuum Imaging in the 18 – 26 GHz Range

Righini¹,

Iacolina

Marongiu

et al. 2022

Sol Phys

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We present a new solar radio imaging system implemented through the upgrade of the large single-dish telescopes of the Italian National Institute for Astrophysics (INAF), not originally conceived for solar observations.During the development and early science phase of the project (2018 – 2020), we obtained about 170 maps of the entire solar disk in the 18 – 26 GHz band, filling the observational gap in the field of solar imaging at these frequencies. These solar images have typical resolutions in the 0.7 – 2 arcmin range and a brightness temperature sensitivity <10 K. Accurate calibration adopting the Supernova Remnant Cas A as a flux reference provided typical errors <3% for the estimation of the quiet-Sun level components and active regions flux measurements.As the first early scientific result of the project, we present a catalog of radio continuum solar imaging observations with Medicina 32-m and SRT 64-m radio telescopes, including the multi-wavelength identification of active regions, their brightness and spectral characterization. The interpretation of the observed emission as thermal bremsstrahlung components combined with gyro-magnetic variable emission paves the way for the use of our system for long-term monitoring of the Sun. We also discuss useful outcomes both for solar physics (e.g., study of the chromospheric network dynamics) and space weather applications (e.g., flare precursors studies).

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