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Astrophysics and Astrononmy
Multi-wavelength view of Dark Halos around active regions | Serena Maria Lezzi
Natural Sciences (Astrophysics and Astrononmy)
Date of upload:
02.03.2023
Co-author:
Vincenzo Andretta, Mariarita Murabito
Caption:
The Dark Halos (DHs) are regions of reduced emission in the neighborhood of solar active regions (ARs). Since their discovery (Hale & Ellerman, 1903), DHs have been called with various names, the first one being circumfacules (Deslanders, 1930), as they were first identified in the chromosphere as faint areas surrounding plages in the Ca II K-line, and later also in the Ca II 8542 Å line (D’Azumbuja, 1930). Bumba & Howard (1965) proposed that the Ca II circumfacules are composed of dark features corresponding to dark Hα fibrils, and this suggestion was supported by different authors (e.g. Rutten et al. 2007, Pietarila et al. 2009). Read more at https://espos.stream/2023/02/16/Lezzi/.
New insights about the past, present and future of solar magnetism | Quentin Noraz
Natural Sciences (Astrophysics and Astrononmy)
Date of upload:
19.01.2023
Caption:
The magnetic field of solar-type stars is generated and sustained through an internal dynamo process. This process is mostly determined by the combined action of turbulent convective motions and differential rotation. It can sometimes lead to magnetic cyclic variabilities, like the 11-years solar cycle. Evidence of magnetic cycles have been detected for other solar-type stars as well, ranging from a few years to a few tens of years. How are these cycles controlled? Observations and stellar evolution models show that solar-like stars spin-down during their main-sequence. In parallel, numerical simulations of these stars show that different regimes of differential rotation can be reach and are characterized with the Rossby number.
Read more at https://espos.stream/2022/12/01/Noraz/.
Solar corona diagnostics with Metis observations | Giuseppe Capuano
Natural Sciences (Astrophysics and Astrononmy)
Date of upload:
06.04.2023
Caption:
The solar corona has been investigated in the last decades through observations coming from several spacecraft. The Metis coronagraph, aboard the ongoing Solar Orbiter mission, extends the UVCS/SOHO spectrocoronagraph observations of the scattered ultraviolet emission of the coronal plasma performed during solar activity cycle 23, by simultaneously imaging the coronal visible light polarized brightness (VL pB), in the spectral bandpass 580-640 nm, and the coronal ultraviolet H I Lyα emission, in the spectral window 121.6 ± 10 nm. We present here some specific observations, such as those taken on May 15, 2020, from which detailed information about the coronal outward velocity were inferred by applying the Doppler dimming technique. Read more at https://espos.stream/2023/03/30/Capuano/.
Searching for signatures of Hα spicule-like features in the solar transition region | Nived Vilangot Nhalil
Natural Sciences (Astrophysics and Astrononmy)
Date of upload:
29.09.2023
Caption:
New instrumental and telescopes covering the optical and UV spectral regions have revealed a range of small-scale dynamic features, many of which may be related. Direct observational evidence in terms of tracking spicules across multiple wavelengths is needed to understand their role in heating the solar atmosphere. This study uses the Hα filtergrams obtained by the CRISP on SST and co-aligned IRIS data to study the signature of the Rapid Blue-shifted Excursions (RBEs) in the transition region. By studying the spatio-temporal evolution of RBEs in Hα and SJI 1400 Å channels, we found that ∼53 % of the RBEs have a transition region counterpart. From the RBE-like events that have a Si iv 1394 Å line profile, 78% of them show a Si iv line flux increase. The events that show line flux enhanceme
Small EUV brightenings detected by HRI-EUV on board Solar Orbiter: estimation of their temperature with SDO/AIA, Solar Orbiter/SPICE and Hinode/EIS | Antoine Dolliou
Natural Sciences (Astrophysics and Astrononmy)
Date of upload:
01.12.2023
Co-author:
Susanna Parenti, Karine Bocchialini
Caption:
The solar corona temperature is maintained to more than 1 MK. One of the main theories of the coronal formation (Parker 1988) suggests that the energy is dissipated into the corona through a high number of impulsive, low energy (10²⁴ ergs) heating events, called “nanoflares”. On 30 May 2020, during its first high temporal and spatial resolutions observations, 1463 small (400 – 4000 km) and short lived (10-100 s) EUV brightenings were detected in the Quiet Sun by the high resolution UV imager HRI-EUV (174 Å) on board Solar Orbiter. These may be the signatures of nanoflare heating. As HRI-EUV is sensitive to both coronal and transition region emission, our goal is to verify if these brightenings indeed do reach coronal temperatures. As spectroscopic data were not available during the 2020 Ma
Phase Mixing of Propagating Alfvén Waves in a Single-fluid Partially Ionized Solar Plasma | Max Mcmurdo
Natural Sciences (Astrophysics and Astrononmy)
Date of upload:
25.01.2024
Caption:
The phase mixing of Alfvén waves is one of the most promising mechanisms for the heating of the solar atmosphere. The damping of waves in this case requires small transversal scales, relative to the magnetic field direction; this requirement is achieved by considering a transversal inhomogeneity in the equilibrium plasma density profile. Using a single-fluid approximation of a partially ionized chromospheric plasma, we study the effectiveness of the damping of phase-mixed shear Alfvén waves and investigate the effect of varying the ionization degree on the dissipation of waves. Read more at https://espos.stream/2024/01/25/Mcmurdo/.
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