Calendar

Speaker: Emanuele Greco (INAF)
Titolo: Jitter radiation as an alternative for the nonthermal filaments in Supernova Remnants
Abstract: Synchrotron radiation from relativistic electrons is usually invoked as the responsible for the nonthermal emission observed in Supernova Remnants (SNRs). Diffusive shock acceleration (DSA) is the most popular mechanism to explain the process of particles acceleration and within its framework a crucial role is played by the turbulent magnetic-field. However, the standard models commonly used to fit X-ray synchrotron emission do not take into account the effects of turbulence in the shape of the resulting photon spectra. An alternative mechanism that properly includes such effects is the jitter radiation, that provides for an additional power-law beyond the classical synchrotron cutoff. In this talk, i will show the results of applying the jitter spectral model to various X-ray observations of Cassiopeia A and found that it describes the X-ray soft-to-hard range better than any of the standard cutoff models. I will also show what relevant turbulence and electrons’ parameters can be measured from the spectra in the jitter radiation framework.

Speaker: Kevin France (University of Colorado at Boulder)

Title:  Exploring Extreme Exoplanets and Stellar Activity with Small Satellite Missions

Abstract: Atmospheric escape is a process that affects the structure, composition, and evolution of many planets.  Atmospheric escape rates depend critically on the extreme-ultraviolet (EUV) and far-ultraviolet (FUV) photon fluxes from the host star.  Owing to high levels of EUV and FUV irradiance from their nearby parent stars, the signatures of rapid atmospheric escape are detectable on close-in, gaseous exoplanets transiting bright stars.  In this talk, I will present current and future small satellite missions designed to directly observe atmospheric escape from exoplanets and to investigate the EUV luminosity and energy partition of EUV flares on nearby stars. The majority of the talk will focus on the Colorado Ultraviolet Transit Experiment (CUTE), a 6U CubeSat mission designed to take advantage of the near-ultraviolet (250 – 330 nm) stellar brightness distribution to conduct novel observations of the extended atmospheres of nearby close-in planets.  CUTE is NASA’s first dedicated exoplanet spectroscopy mission and has collected 6 – 11 transits of each of seven short-period exoplanets.  I will present an overview of the CUTE mission, including its development path and on-orbit observations of excess NUV absorption on ultra-hot Jupiters.  I will conclude the talk by describing the upcoming Monitoring Activity from Nearby sTars with uv Imaging and Spectroscopy (MANTIS) mission, a 12U CubeSat that will make simultaneous observations of nearby stars in four spectral bands from the EUV through the optical (~10 – 1000 nm).  MANTIS will conduct two surveys over its planned two-year mission lifetime: deep EUV observations of nearby stars and contemporaneous stellar characterization data in support of James Webb Space Telescope exoplanet spectroscopy observations.

Speaker: Ileana Chinnici (INAF)
Titolo:Piazzi, Fratelli muratori, logge e documenti massonici
Abstract: TBD

Speaker: Francesco Malara (UniCal)

Titolo del talk: “MHD waves and turbulence in plasmas of the solar corona”

Abstract:
“The solar corona is made of extremely tenuous plasmas having different physical conditions, e.g., temperature, density, and magnetic fields. In response to perturbations, restoring forces determined by pressure and the local magnetic field can determine the formation and propagation of magnetohydrodynamic (MHD) waves. Coronal loops sustain the propagation of different types of MHD with a broad range of periods and amplitude, with the most easily observed and studied one being the kink mode. Kink waves in loops, usually excited in impulsive events (e.g. flares) with amplitude of 4-5 Mm and periods of 3-5 min, are strongly damped within few wave periods. However, high-resolution observations from different space missions in the last decade have shown the omnipresence of so-called “decayless fluctuations”, i.e., kink oscillations with a small amplitude (< 1 Mm) and no damping. Their discovery in the solar corona has posed new questions about their driver and the mechanisms for energy transfer in the solar atmosphere. In fact, the dissipation of the fluctuation energy is one of the possible mechanisms that are believed to be resposible for the heating of the solar corona. In an extremely high Reynolds/Lundquist number plasma, such as in the corona, a key role is played by fluctuation-inhomogeneity couplings, as well as by nonlinear effects that generate a turbulent cascade. In the last few decades such effects have been studied in great detail. Here we present a numerical investigation aiming at clarifying the interplay of these two mechanims in the dissipation of Alfvén waves. We find that, in a regime representative of coronal magnetic structures, fluctuation-inhomogeneity couplings and turbulence synergically work to significantly speed up the conversion of fluctuating kinetic/magnetic energy into thermal energy. Their potential contribution to solving the coronal heating problem is emphasized, as well as the potentialities offered by the MUSE mission in studying the formation and evolution of MHD waves in the corona.”