Events

Guest: Prof. Dr. Günter Sigl, Universität Hamburg, II. Institut für Theoretische Physik, Hamburg, Germany

When: 1 August 2024, 11:00

Where: ISS, Auditorium

Abstract:

Origin and nature of ultra-high energy cosmic rays above ~ 10¹⁸ eV are still not very well understood. Progress on these questions requires on the one hand enhanced experiments providing multiple complementary observables, such as the Pierre Auger Observatory. On the other hand, there is a need for a better theoretical understanding of the relevant physics, in particular the nature of hadronic interactions that give rise to the detected giant air showers and the propagation of charged particles in a structured Universe. In addition, secondary gamma-rays and neutrinos can provide complementary multimessenger signatures. In this talk we will focus on a few key points on these topics.

Contact: Dr. Gina Isar <gina.isar[at]spacescience[dot]ro>

Gallery:

On Wednesday, 17 November 2021, MDPI and the Journal Universe organized the 3^rd webinar on Universe, entitled „Women Physicists in Astrophysics, Cosmology and Particle Physics”.

The webinar highlighted the Special Issue devoted to this subject and the results presented in it.

In this first webinar, were hosted four talks presenting new results and reviews covering different areas of high current interest regarding theoretical and experimental astro- and cosmo-particle physics. The main topics are:

1) Chair Introduction: Women Physicists in Astrophysics, Cosmology and Particle Physics by Prof. Dr. Norma G. Sanchez, CNRS, PSL-Paris Observatory and Chalonge de Vega International School Center, Paris, France;

2) Dark Matter Sterile Neutrino from Scalar Decays by Dr. Lucia Aurelia Popa, Institute of Space Science, Magurele, Ilfov, Romania;

3) New Advancements in AdS/CFT (Anti-de Sitter/Conformal Field Theory) in Lower Dimensions by Professor Yolanda Lozano, Department of Physics, University of Oviedo and ICTEA, Oviedo, Spain;

4) Superconformal Line Defects in Three Dimensions by Professor Silvia Penati, Department of Physics, University of Milano-Bicocca and INFN, Milano, Italy;

5) Environmental High-Energy Astrophysics in the context of space missions such as LISA, Solar Orbiter and JWST, and its implications for space weather science by Professor Catia Grimani, University of Urbino “Carlo Bo”, Urbino and INFN, Florence, Italy.

The webinar was offered via Zoom and required registration to attend. The full recording can be found on Sciforum website and YouTube.

Contact person (ISS): Dr. Lucia A. Popa <lpopa@spacescience[dot]ro>

Guest: Dr. Athina Meli, Liège University, Belgium and Athens Institute for Education and Research, Greece

When: 23 May 2018, from 11:00

Where: ISS, Auditorium

Abstract:

The Universe is filled with a rich diversity of high-energy phenomena and highly energetic processes. Great developments in astrophysical observations over the last years, as well as in-tandem simulation studies, opened a wide window into the understanding of the electromagnetic wavebands of astrophysical phenomena, from the radio waves up to the high-energy gamma-rays but also to high energy cosmic-rays, which carry a multitude of information about the most energetic phenomena in Cosmos. Accelerated particles (cosmic-rays) are believed to be created in the cataclysmic ”explosions” of astrophysical sources like Gamma-Ray-Bursts and in the jets of Active Galactic Nuclei. The acceleration of cosmic-rays and the emission of very high energy electromagnetic radiation (i.e., x-rays, gamma-rays) mostly occur in the relativistic superalfvenic cosmic plasmas and jets that act as cosmic accelerators. In this talk I will give an overview of these high-energy accelerators and will discuss the mechanisms responsible to producing very high-energy cosmic rays and radiation.

Contact person: Dr. Ioana Dutan <idutan[at]spacescience[dot]ro>

Instructor: Dr. Ken-Ichi Nishikawa, University of Alabama, Huntsville, SUA

When: 21-25 May 2018. Course hours:

Mo: 2pm-4pm;
 Tu: 10am-12am and 2pm-4pm; Wed: 2pm-4pm;
 Thu: 10am-12am and 2pm-4pm; Fri: 10am-12am

Where: ISS, Auditorium

Abstract:

This course is intended to provide students/researchers with basic concepts of computer simulations using a particle-in-cell (PIC) numerical code in order to understand kinetic processes in plasmas. PIC simulation is, in principle, an accurate method and provides the widest range of plasma effects. Nowadays, the computer power is powerful enough to perform reasonable 3-dimensional (3D) simulations to investigate realistic plasma dynamics. The course will cover the fundamental concepts of plasma simulation by performing small 3D electromagnetic codes with applications to relativistic jets. Starting with a brief introduction to plasma physics, the mathematics and physics behind the algorithms will be described. We will explore how PIC simulations reveal plasma behaviors as they are highly nonlinear phenomena. Some examples of how to run the PIC simulations will be also given.

Overview:

1. Plasma physics on computer (general description)
2. Kinetic plasma simulations (nonphysical instability, approximate nonlinear analysis, plasma behavior, linear weighting, nonphysical effects)
3. How PIC works (cold plasma dispersion, plasma dispersion function)
4. Electrostatic codes (grid quantities, beat heating)
5. Electromagnetic codes (hybrid oscillation, warm and unmagnetized plasmas)
6. Finite-difference time-domain Maxwell solver on Yee grid: leapfrog algorithm
7. Particle movers: Boris’s algorithm
8. Conservative charge deposition method
9. Boundary conditions (particles and fields)
10. Simulations for astrophysical plasmas
11. Recent work: (1) Weibel instability in relativistic jets (radiation, weighted beam) and (2) Reconnection (particle acceleration)

Reference: “Plasma Physics via Computer Simulation (Series in Plasma Physics)”, C.K. Birdsall & A.B. Langdon; Programs in the text book are written in Fortran.

Prerequisites: Elementary physics (Bachelor level)

Registration: Subscription for attending the course should be sent to Dr. Ioana Dutan <idutan[at]spacescience[dot]ro>, with your name, status (e.g., student, researcher) and affiliation, no later than May 15th 2018.

The event can be followed live on the ISS Facebook and YouTube channels.

List of participants

Photo Gallery:

Guest: Dr. Ken-Ichi Nishikawa, University of Alabama in Huntsville, USA

When: 21th May 2018, from 11:00

Where: Institute of Space Science – ISS (Auditorium)

Abstract:

The discovery by Advanced LIGO/Virgo of gravitational waves from the binary neutron star (BNS) merger GW170817 triggered sequential observations of the electromagnetic counterparts, which has opened the era of multi-messenger astronomy. These multi-frequency observations provide us profound information to investigate the processes from the generation of gravitational wave, associated relativistic jets and merger ejecta, and consequently radiation from the interaction of jets and ejecta with interstellar medium. The investigation of these phenomena requires extensive and systematic theoretical and computational research with various observations. In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. We have studied the initial evolution of both electron–proton and electron–positron relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed particle-in-cell simulations of “global” jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI) using a larger jet radius. In our previous simulation study, these kinetic instabilities are suppressed and new types of instabilities can grow. In the electron-proton jet simulation a recollimation-like instability occurs near the center of jet. In the electron-positron jet simulation mixed kinetic instabilities grow and the jet electrons are accelerated. In this talk, I will present results of synthetic radiation spectra that are obtained directly from simulations using much larger systems for global jets containing helical magnetic fields., which can then be compared with observations of gamma-ray burst objects. I will also present possible mechanisms of X-ray flare production for such objects due to magnetic reconnection.

Contact person: Dr. Ioana Dutan <idutan[at]spacescience[dot]ro>

Guest: Dr. Andrea Zacchei, Astronomical Observatory of Trieste

When: November 22th, 2017, 11h00

Where: Institute of Space Science – ISS (Auditorium)

Abstract:

The organization, development and operation of a Science Ground Segment for a Space Mission is a very complex system. Its costs are at the level of an instrument development with the additional complexity of a NOT centralized system. Strategy used in the creation of the Euclid Ground Segment will be discussed with emphasis on the technical solution adopted.

Contact person: Dr. Lucia A. Popa (ISS) <lpopa[at]spacescience[dot]ro>