ALMA operations suspended due to COVID-19 pandemic

Napisao/la Ivica Skokic on . Posted in News

ALMA COVID-19Due to the global COVID-19 pandemic, which has also spread into Chile, the ALMA director and executives decided to suspend ALMA operations until the situation normalizes. The call for proposals for Cycle 8, which was open during the beginning of the pandemic, has also been suspended. This bad news also affects our project, since we will not be able to submit observing proposals, no new data will be produced, and proprietary period for data will be prolonged and not accessible to the public.


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Polar and limb brightening in ALMA images

Napisao/la Ivica Skokic on . Posted in News

thumb Sudar limb brighteningIn a series of papers our team analyzed the effects of limb brightening and polar brightening in ALMA solar images. Limb brightening is an effect analogous to the familiar limb darkening visible in images of the solar photosphere which is explained as a consequence of seeing deeper (and hotter) layers of the photosphere near the center of the Sun. Near the limb, due to geometry, a shallower (and colder) photospheric layers are observed and hence they appear darker. However, as explained in the paper by Sudar et al. "Centre to Limb Brightness Variations from ALMA Full Disk Solar Images",  in chromospheric images of the Sun made with ALMA, due to inversion of the temperature profile when the temperature starts to rise again towards corona, an opposite effect is observed - limb brightening. In the paper, authors develop a method to remove the center-to-limb function from the data. In two papers by Sudar et al. "Polar Brightening in ALMA Full-disk Solar Images" and by Selhorst et al. "Solar Polar Brightening and Radius at 100 and 230 GHz Observed by ALMA", polar brightenings of the Sun at ALMA radio frequencies are studied and compared with several theoretical models. This can help in constraining different models and parameters of the solar atmosphere.

First MSOC papers published

Napisao/la Ivica Skokic on . Posted in News

thumb Skokic diffusion paper 2019The first several papers related to the MSOC project were published recently. A paper by Selhorst et al. "Solar Polar Brightening and Radius at 100 and 230 GHz Observed by ALMA" studies polar brightenings of the Sun at radio frequencies using ALMA observations and comparing them to several theoretical models. A paper by Skokić and Brajša "ALMA Solar Ephemeris Generator" published in the Mining-geological-petroleum engineering bulletin describes an online software tool developed by the authors for easy preparation of solar observations with ALMA.

Vršnak studied the physical background of the evolution of a coronal magnetic flux rope embedded in the magnetic arcade during the gradual-rise pre-eruptive stage in a paper "Gradual Pre-eruptive Phase of Solar Coronal Eruptions" published in Frontiers in Astronomy and Space Sciences.

Two MSOC papers were published in the same issue of Astrophysical Journal. Vršnak et al. in "Heliospheric Evolution of Magnetic Clouds" present analysis of interplanetary evolution of 11 magnetic clouds. The analysis reveals that in a statistical sense, the expansion of the studied magnetic coluds (MCs) is compatible with self-similar behavior. However, individual events expose a large scatter of expansion rates, ranging from very weak to very strong expansion. Also, a discrepancy between the magnetic field decrease and the increase of the MC size was found, indicating that magnetic reconnection and geometrical deformations play a significant role in the MC evolution. In the paper "Turbulent Diffusion Derived from the Motions of SDO/AIA Coronal Bright Points" Skokić et al. study the motions of coronal bright points to infer the character and intensity of the solar diffusion processes. Results indicate subdiffusion on meso- to supergranular scales.

First results from ALMA published in Astronomy & Astrophysics

Napisao/la Jaša Čalogović on . Posted in News

thumb Brajsa 2018 figOn 23rd May, Astronomy & Astrophysics published Brajša et al. paper “First analysis of solar structures in 1.21 mm full-disc ALMA image of the Sun” on the cover page where the first results using the ALMA (Atacama Large Millimeter/submillimeter Array) for solar observations were presented. The aim of the paper was to identify different structures and their intensities in the solar atmosphere in full-disc solar ALMA images. ALMA is currently the largest radio telescope in the world and it is composed of 66 high-precision antennas, which operate on wavelengths of 0.32 to 3.6 mm.