First high-resolution look at the quiet Sun with ALMA at 3 mm
by A. Nindos et al.*

2018-11-27 451 views

Observations of the radio continuum at millimeter (mm) wavelengths provide a unique chromospheric diagnostic. The quiet Sun mm-wavelength emission mechanism is free-free and electrons are almost always in local thermodynamic equilibrium (e.g. Shibasaki et al. 2011 and Wedemeyer et al. 2016). The availability of mm-wavelength solar observations with ALMA can advance our knowledge on the chromosphere because of the instrument’s unique spatial resolution and sensitivity. In a previous study (Alissandrakis […]

Topical issue “Solar radio physics from the chromosphere to near Earth” published
by E.P Kontar and A. Nindos

2018-06-26 532 views

The 2016 CESRA workshop ( had a special emphasis on the complementarity of current and future space-based observations with ground-based radio observations. It was the place to discuss the new exciting science opportunities that arise from radio instruments such as the Atacama Large Millimeter/submillimeter Array (ALMA), the Expanded Owens Valley Solar Array (EOVSA), the Expanded Very Large Array (EVLA), the Low Frequency array (LOFAR), the Mingantu Spectral Radioheliograph (MUSER), and […]

Solar ALMA observations: constraining the chromosphere above sunspots
by M. Loukitcheva et al.*

2018-02-20 773 views

Our understanding of sunspots is far from complete despite intensive research over hundreds of years. Radiation at submillimeter and millimeter wavelengths is formed in local thermodynamic equilibrium (LTE) in the low to mid chromosphere, and its intensity depends linearly on the ambient temperature of the medium. Observations at these wavelengths thus provide important diagnostics of sunspot chromospheres (Loukitcheva et al. 2014). The largest radio telescope in the world, the Atacama […]

Solar Prominence Modelling at ALMA Wavelengths
by A. Rodger and N. Labrosse

2017-11-14 466 views

The small-scale temperature structure of prominences remains an outstanding question in solar physics. Theoretical models provide scenarios for how cool prominence plasma can be formed and maintained within the extreme conditions of the corona. However, knowledge of the detailed temperature structure of the prominence plasma and its evolution at small spatial and temporal scales is still lacking. The Atacama Large Millimeter/sub-millimeter Array (ALMA) provides a novel method for high spatial […]

Probing the Temperature Structure of the Solar Chromosphere with ALMA
by C. Alissandrakis et al.*

2017-08-01 874 views

Determining the detailed temperature structure of the solar atmosphere from observations is a basic means of constructing and testing atmospheric models. One avenue to address this problem is based on measuring the center-to-limb variation of the intensity in various spectral regions. Observations in the radio domain are particularly suited for such a task since they don’t suffer from a set of complications (e.g., departures from the ionization and local thermodynamic […]

The Brightness Temperature of the Quiet Solar Chromosphere at 2.6 mm
by Kazumasa Iwai et al

2017-04-25 983 views

The brightness temperature of the Sun constitutes a basic property of the solar atmosphere. The main emission mechanism of the Sun at millimeter and submillimeter wavelengths is thermal free–free emission from the chromosphere, which is an atmospheric layer with a temperature ranging between 6000 to 20,000 K. The opacity of thermal free–free emission depends on the temperature and density in the emission region. In addition, the Rayleigh– Jeans law is applicable […]