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High-resolution observations of the umbral filament in AR NOAA 12529
Get PDFRecent observations have shown in some sunspots the presence of structures that have been called umbral filaments (UFs). These consist of bright filamentary features intruding sunspot umbrae, different in morphology, evolution, and magnetic configuration from usually observed light bridges. We report on the properties of an UF observed inside the umbra of the giant leading sunspot in active region NOAA 12529. We analysed high-resolution observations taken in the photosphere with the spectropolarimeter aboard the Hinode satellite and in the upper chromosphere and transition region with the IRIS telescope. These observations were complemented with data from the Solar Dynamic Observatory satellite and from the INAF-OACT equatorial spar to study the evolution of this structure. We find that the UF harbours a strong horizontal component of the magnetic field and a portion with polarity opposite with respect to that of the umbra. In the upper atmospheric layers, the structure is cospatial to a bundle of filaments, which appears to be rooted in the sunspot umbra. We propose that the UF is the photospheric counterpart of a flux rope touching the sunspot and giving rise to penumbral-like filaments in the umbra via magneto-convection
Continuum emission enhancements and penumbral changes observed during flares by IRIS, ROSA, and Hinode
Get PDFIn this paper we describe observations acquired by satellite instruments (Hinode/SOT and IRIS) and ground-based telescopes (ROSA@DST) during two consecutive C7.0 and X1.6 flares occurred in active region NOAA 12205 on 2014 November 7. The analysis of these data show the presence of continuum enhancements during the evolution of the events, observed both in ROSA images and in IRIS spectra. Moreover, we analyze the role played by the evolution of the δ sunspots of the active region in the flare triggering, indicating the disappearance of a large portion of penumbra around these sunspots
Solar flare forecasting using photospheric active region properties
Get PDFDaily observations of the photosphere are performed by the Equatorial Spar of INAF- Catania Astrophysical Observatory (INAF-OACt). In this poster we describe the results obtained by a tool developed for solar flare forecasting on the base of photospheric active region properties. We measured five parameters describing the morphology of the active regions appeared on the solar disc from January 2002 up today: area, Zurich class, number of pores and sunspots, relative importance between leading spot and density of the sunspot population and type of penumbra of the main sunspot. By means of a linear combination of these parameters we determined the probability that a flare of C-, M- and X- class occurs in such active regions. Comparing our forecasting with the number of flares registered by GOES satellites in the 1 - 8 ˚A X-ray band during the subsequent 24 hrs we evaluate the accuracy of our method using different skill scores
Light hypernuclei —a testbed for charge symmetry breaking
Get PDFCharge symmetry can be considered as an approximate symmetry in nuclear structure and interactions. It is broken in quantum chromodynamics by the up and down quark mass difference and electromagnetic interactions on the level of 10−3. In Λ hypernuclei, charge symmetry breaking (CSB) manifests itself in a charge dependence of Λ separation energies. At the Mainz Microtron MAMI, the novel method of high-resolution spectroscopy of decay-pions in strangeness electroproduction was established to measure Λ separation energies. A sizable CSB effect was reaffirmed for the A = 4 mirror pair and until recently, it could not be reproduced in any ab initio 4-body calculation. The full understanding of this large and spin-dependent effect remains one of the unresolved issues of hypernuclear physics
Nuclear physics with an effective field theory around the unitarity limit
Get PDFI outline the first steps in the process of describing nuclear ground states with an expansion around two-body unitarity. At leading order, the effective field theory displays discrete scale invariance with a single dimensionful parameter, which determines all ground-state and low-lying excitation energies. Sub-leading corrections are smaller and perturbative. Results for light nuclei, large bosonic clusters at unitarity, and nuclear matter are reported
Investigation of precisely selected evaporation chains in the decay of 24,25Mg
Get PDFIn this proceeding an overview on the NUCLEX scientific campaign aimed at studying the decays of light excited nuclei is presented. After an introduction on the physics case and a description of the adopted experimental strategy, the main results related to the decays of the 24Mg and 25Mg are reported. On both systems, an excess in the fusion-evaporation branching ratios of the channels where only α particles can be emitted has been observed. A possible explanation of the observed non-statistical effects is suggested within a recent application of nuclear
time-dependent density functional theor
The r-process nucleosynthesis and related challenges
Get PDFThe rapid neutron-capture process, or r-process, is known to be of fundamental importance for explaining the origin of approximately half of the A > 60 stable nuclei observed in nature. Recently, special attention has been paid to neutron star (NS) mergers following the confirmation by hydrodynamic simulations that a non-negligible amount of matter can be ejected and by nucleosynthesis calculations combined with the predicted astrophysical event rate that such a site can account for the majority of r-material in our Galaxy. We show here that the combined contribution of both the dynamical (prompt) ejecta, expelled during binary NS or NS-black hole (BH) mergers, and the neutrino as well as viscously driven outflows generated during the post-merger remnant evolution of relic BH-torus systems can lead to the production of r-process elements from mass number A 90 up to actinides. The corresponding abundance distribution is found to reproduce the solar distribution extremely well. It can also account for the elemental distributions observed in low-metallicity stars. However, major uncertainties still affect our understanding of the composition of the ejected matter. These concern (i) the
β-interactions of electron (anti)neutrinos with free neutrons and protons, as well as their inverse reactions, which may affect the neutron-richness of the matter at the
early phase of the ejection, and (ii) the nuclear physics of exotic neutron-rich nuclei, including nuclear structure as well as nuclear interaction properties, which impact
the calculated abundance distribution. Both aspects are discussed in the light of recent hydrodynamical simulations of NS mergers and microscopic calculations of nuclear decay and reaction probabilities
Exploring neutron channel solutions at CERN/n TOF for the Cosmological Lithium Problem
Get PDFNew measurements of the 7Be(n, α) 4He and 7Be(n, p)
7Li reaction cross sections from thermal to keV neutron energies have been performed at CERN/n TOF. High purity 7Be material was produced at the Paul Scherrer Institute (PSI) and implanted at CERN/ISOLDE, demonstrating the feasibility of neutron measurements on samples produced at radioactive beam facilities. The cross sections are significantly higher than previously determined, at low energies. The new estimate of the 7Be destruction rate based on these new results yields a decrease of the predicted cosmological 7Li abundance, insufficient to provide a viable solution to the Cosmological Lithium Problem (CLiP). The two n TOF measurements can finally rule out neutron-induced reactions as a potential explanation of the CLiP, leaving all alternative physics and astronomical scenarios still open
A new measurement of the 2H(p,γ)3He cross section at the BBN energies
Get PDFThe Big Bang Nucleosynthesis (BBN) models describe the production of light nuclei in the first minutes of cosmic time. When, as a consequence of temperature decrease of the Universe, the equilibrium between deuteron production through p(n, γ) 2H and its photo-dissociation was broken, the deuterium nuclei just created were destroyed through the 2H(2H,p)3H, the 2H(2H,n)3He and the 2H(p,γ) 3He reactions. The overall primordial deuterium abundance is thus determined by the cross sections of all these reactions, experimentally studied in nuclear laboratories since the middle of last century. Recently, precise measurements of the primordial deuterium abundance have opened the possibility to precisely constrain the primordial baryon-to-photon ratio, independently from evaluations based on the Cosmic Microwave Background (CMB) measurements. For their interpretation, the deuterium abundance data require equally precise nuclear physics data: the main obstacle to an accurate theoretical 2H abundance evaluation is the poor knowledge of the 2H(p,γ)
3He cross section at the relevant energies. The aim of the present work is to describe the experimental effort undertaken by the LUNA collaboration, aimed to measure with unprecedented precision the reaction cross section in the
BBN energy range (30<Ec.m.[keV ]<300)
High precision data on elastic dd scattering at 65 MeV/nucleon
Get PDFWe present the results of measurements of differential cross section and analyzing powers for the elastic 2H(d, d )d scattering process. The data were obtained using a 130 MeV polarized deuteron beam impinging a liquid-deuterium
target. The experiments were conducted at the AGOR facility at KVI using the BINA 4π-detection system. Our measurements are compared to results of previous studies and to a different set of data taken with the BBS at KVI. The data are found to be in excellent agreement with each other. The results can be used to confront upcoming state-of-the-art calculations in the four-nucleon scattering domain, and
will, thereby, provide further insights in the dynamics of three- and four-nucleon forces in few-nucleon systems