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Attracted by the fascinating magnetism of the Sun
Get PDFThe Sun is a quite active star, where still enigmatic phenomena characterize its life. This one is modulated at large scales by a remarkable degree of order (11-yr cycle and other superimposed cycles) even if the regenerating convective source of the whole magnetic activity is characterized by a chaotic and turbulent behavior. Several aspects of the solar magnetic activity are still not completely understood, such as the time-length of cycles, the dependency of the activity on the latitude, the actual role of the tachocline with the exact location of the dynamo regenerating sources. Here the solar dynamo problem is reviewed in the light of recent developments in theories and observations. In particular, global spherical simulations of convective dynamos and numerical experiments on Parker dynamo waves will be discussed. This latter are recently drawing a possible way for an unitary view of both large-scale and small-scale dynamo, contrary to the conventional theory that considers these as complementary approaches of the same problem: the astrophysical magnetism
Solar activity cycles and grand minima occurrence
Get PDFSunspot number reconstructions (SNRs) based on dendrochronologically dated radiocarbon concentrations are analyzed through the Empirical Mode Decomposition (EMD) to provide a deeper characterization of the solar activity long-term periodicities and to investigate the role of the Gleissberg and Suess cycles in the grand minima occurrence. The Gleissberg and Suess cycles, with timescales of 60–120 yr and 200–300 yr respectively, represent the most energetic contribution in SNR records. The EMD approach reveals that these cycles are characterized by multiple scales of variation and that the grand minima sequence is produced by the coupling between Gleissberg and Suess cycles, the latter being responsible for the most intense and longest Sp¨orer-like minima, with typical duration longer than 80 yr
Two different approaches to the observation of solar flares: Science or forecasting?
Get PDFSolar flares are the main sources of acceleration of energetic particles from the solar atmosphere through the Heliosphere to the circum-terrestrial Environment. At present, several space-born telescopes in collaboration with small, medium and large class telescopes provide plenty of data at the different wavelengths and resolutions, which allow us to study these phenomena in detail. In this review, I describe some of the recent results obtained in the international context by our Italian community concerning the study of the mechanisms at the base of the storage and release of free energy in solar flares. I highlight the main aspects which characterize two different approaches to the observation of the flares: the attempt to provide a further contribution to the physics of the processes involved by such events and the answer to the increasing request of forecasting in order to prevent the damage to the technological systems which permeate our life. Both approaches require a vision as complete as possible of the whole solar atmosphere and synergies among different methods of analysis
Grad-Shafranov reconstruction of a magnetic cloud: Effects of the magnetic-field topology on the galactic cosmic-ray intensity
Get PDFThe passage of the interplanetary counterpart of a coronal mass ejection was observed at L1 between 2016 August 2 at 14:00 UT and August 3 at 03:00 UT. The transit of shock, sheath and magnetic cloud (MC) regions are identified and the MC configuration is studied through the Grad-Shafranov reconstruction technique. A classical Forbush decrease (FD) in the galactic cosmic ray (GCR) intensity was observed by the particle detector (PD) aboard the European Space Agency LISA Pathfinder (LPF) mission on 2016 August 2. The PD allowed to monitor the GCR intensity at energies above 70 MeV n−1 with a statistical uncertainty of 1% on one-hour binned data. The observed fractional decrease of the GCR intensity around the dip of the event is investigated through a full-orbit particle propagation in the MC and related to the reconstructed magnetic field topology
Photonuclear spectroscopy with the ELIADE array at ELI-NP
Get PDFThe Extreme Light Infrastructure – Nuclear Physics in BucharestM˘agurele, Romania, is a major European undertaking with the aim of constructing a facility that can produce the worlds highest intensity laser beams as well as unique high-brilliance, narrow-bandwidth gamma-ray beams using laser-based inverse Compton scattering. One of the main instruments being constructed for the nuclear physics and applications with high-brilliance gamma-beams research activity is the ELIADE detector array of eight segmented HPGe clover detectors. Using the nuclear resonance fluorescence technique this setup will provide us with access to several nuclear observables like spins, parities, level widths, and branching ratios in the decay. From these observables we expect to draw conclusions about, for example, nuclear dipole response, properties of pygmy resonance and collective scissors mode excitations, parity violation in nuclear excitations, and matrix elements
for neutrinoless double-beta decay, among other topics. The uniqueness of the environment in which ELIADE will operate presents several challenges in the design and construction of the array. In this contribution we will present some of these challenges and how these challenges are overcome
Silicon carbide for future intense luminosity nuclear physics investigations
Get PDFSilicon carbide (SiC) is one of the compound semiconductor which has been considered as a potential alternative to Silicon for the fabrication of radiation hard particles detectors. Material, detectors implementation and possible
application in the future INFN projects has been discussed
Heavy-flavour production measurements in heavy-ion collisions with ALICE at the LHC
Get PDFThe measurement of heavy-flavour production in ultra-relativistic heavy-ion collisions provides insights into the properties of the Quark-Gluon Plasma (QGP), the state of strongly-interacting matter characterised by high temperature
and energy density where quarks and gluons are deconfined. ALICE results on heavy-flavour production in p–Pb and Pb–Pb collisions are presented
Time scales in nuclear structure and nuclear reactions of exotic nuclei
Get PDFTwo relevant time scales are introduced to describe the interplay of nuclear structure and nuclear reactions for exotic nuclei. The collision time represents the time dependence of the external field created by the target on the projectile. The excitation time represents the characteristic time dependence of the projectile degrees of freedom due to its internal Hamiltonian. The comparison of
these two time scales indicate when approximate treatments of the reaction, such as the sudden approximation, implicit in the eikonal treatment, is applicable. An approach based on these time scales is used to describe recent experimental data as well as theoretical calculation involving Coulomb break-up, stripping reactions and (p, pN) reactions. It is suggested that the dependence of the stripping cross sections on the difference of binding energies of protons and neutrons may be associated to
inadequacy of the eikonal approximation to describe the removal of strongly bound nucleons at intermediate energies
Nuclear structure solving problems of fundamental physics
Get PDFNuclear-structure calculations are important inputs for solving problems of fundamental physics. Such problems are related with, e.g., neutrinos and dark-matter particles and their interactions with atomic nuclei. In this article the
focus is directed to the important problem of the renormalization of the weak axial coupling gA and accurate treatment of β spectrum shapes. As particular applications of the spectral shapes the spectrum-shape method (SSM) and the hot topic of “reactor antineutrino anomaly” are introduced
Light and heavy fragments mass correlation in the 197Au + 130Te transfer reaction
Get PDFWe studied multinucleon transfer (MNT) processes in the 197Au + 130Te at Elab=1.07 GeV system coupling the PRISMA magnetic spectrometer to NOSE, an ancillary particle detector. We constructed a mass correlation matrix
associating to each light fragment identified in PRISMA the corresponding mass distribution of the heavy partner detected in NOSE and, through the comparison with Monte Carlo simulations, we could infer about the role of neutron evaporation in multinucleon transfer reactions for the population of neutron-rich heavy nuclei