Calendar
“3D MHD simulations from the onset of the supernova to the development of the full-fledged remnant”
Antonio Tutone
The aim of this thesis is to bridge the gap between Supernovae (SNe) and their remnants (SNRs) by investigating how the remnants keep memory of the physical and chemical properties of the stellar progenitors and of the anisotropies of the explosions. I performed three-dimensional magneto-hydrodynamical simulations starting soon after the SN event and following the interaction of the SN ejecta with the circumstellar medium (consisting in the wind of the stellar progenitor), obtaining the physical scenario of a SNR. I investigated how the ejecta distribution of two different progenitors can affect the matter mixing of heavy elements in the remnant from the onset of the SN to 500 years. An 16M-ejecta blue supergiant (BSG) progenitor and a 19M-ejecta red supergiant (RSG) progenitor are investigated. Both spherical and aspherical explosions are investigated. I found that the SNR keeps memory both of the physical and chemical properties of the stellar progenitor and of the anisotropies of the explosion.
“Esplosioni di Supernovae e loro interazione con il mezzo circostante”
Luca La Mantia
Una Supernova è l’esplosione di una stella alla fine della sua evoluzione che genera, fra l’altro, un ammasso eterogeneo di gas e polveri detto Supernova remnant. A causa dell’esplosione si forma un’onda d’urto o shock che investe il materiale circumstellare e, riscaldandolo, ne fa un plasma con temperature che possono raggiungere alcuni miliardi di Kelvin. L’obiettivo della seguente tesi è studiare l’interazione del plasma con il mezzo circumstellare del Supernova remnant IC443 attraverso una semplice simulazione numerica magneto-idrodinamica del remnant. Poiché, tramite le osservazioni, si è visto che IC443 interagisce con una nube atomica a Nord-Est e con una nube toroidale molecolare a Nord-Ovest e a Sud-Est, ho analizzato l’interazione del plasma shockato con le nubi al variare della densità di particelle delle stesse. Inoltre ho confrontato le varie simulazioni tra loro e ho studiato il comportamento del campo magnetico. Le simulazioni mostrano come la variazione della densità cambi la morfologia del remnant. Confrontando le simulazioni con le immagini del remnant ho potuto concludere anche che le nubi emettono fortemente in X e che la nube toroidale non emette in ottico.
In questo breve incontro, Caterina Boccato nelle veci del responsabile nazionale della didattica e divulgazione, Stefano Sandrelli, presenta la Struttura per la Comunicazione della Presidenza con particolare riguardo alla didattica e alla divulgazione (D&D).
Il seminario sara` un’importante occasione di incontro per illustrare ai ricercatori INAF in che modo questa struttura può essere loro utile e che cosa la struttura si aspetta da parte dei ricercatori. A tal fine ne racconterà la strategia e gli strumenti adottati con una panoramica di quanto è stato fatto nel 2017 e nel 2018, mettendo in evidenza aspetti, efficaci e non, delle attività svolte. Per finire, uno sguardo al programma futuro.
The study of the interaction of cosmic rays with the interstellar matter is a multi-disciplinary investigation that involves the analysis of several physical and chemical processes: ionisation of atomic and molecular hydrogen, energy loss by elastic and inelastic collisions, energy deposition by primary and secondary electrons, gamma-ray production by pion decay, the production of light elements by spallation reactions, and much more. Cosmic-ray ionisation activates the rich chemistry of dense molecular clouds and determines the degree of coupling of the gas with the local magnetic field, which in turn controls the collapse timescale and the star-formation efficiency of a molecular cloud. In recent years a wealth of observations from the ground and from space has provided information and constraints that still need to be incorporated in a consistent global theoretical framework. My goal is to use the results of chemical models and state-of-the-art numerical simulations supplemented by dedicated observations to provide a unifying interpretation of the data with a model of cosmic-ray propagation specifically developed to make predictions that can be tested against the observations. Finally, I will talk about my most recent study: a mechanism able to accelerate local thermal particles in protostars that can be used to explain the high ionisation rate as well as the synchrotron emission observed towards protostellar sources.
The accurate and timely prediction of solar eruptions is important for many space weather prediction tools and the Solar Orbiter mission. The aim of this study is to propose a new technique for the automated prediction of magnetic flux rope ejections in data driven NLFFF simulations hours in advance. We use a data-driven NLFFF model to describe the evolution of the 3D magnetic field of 8 active regions: 5 that produced an eruption and 3 where no eruption was observed. From the 3D magnetic field configuration, we determine a possible proxy for the loss of equilibrium of the magnetic flux rope based on the Lorentz force. Such proxy is significantly higher for the simulations of the eruptive active regions. For some cases, using a subset of the observed magnetograms, we ran a series of predictive simulations to test whether the time evolution of the proxy project forward in time can be used to predict the eruptions. We find that the identified proxy is useful in anticipating the magnetic flux rope ejection and that a meaningful prediction can be made up to 10 hours in advance. Although a number of issues need to be addressed for a fully operational application, this study presents an interesting solution for the prediction of CME onsets and future studies will address how to generalise the model such that it can be used.