2023 September KNAG Meeting

Post: 2023-08-24 / Last Update: 2023-10-26

The Korea Numerical Astrophysics Group (KNAG) is pleased to invite you to our upcoming meeting on September 15th at Korea Astronomy and Space Science Institute (KASI).
This meeting will bring together astrophysicists and researchers to discuss the latest developments in astrophysics research.

Meeting Details

1. Date: 15th September (Fri.) 2023
2. Time: 14:00 ~ 17:00 (tentative)
3. Venue: Korea Astronomy and Space Science Institute (KASI), Jangyoungsil Hall 331-2
4. Program

• 14:00 ~ 14:40 Mageshwaran Tamilan, CBNU
• 14:40 ~ 15:00 Discussion & Coffee Break 1
• 15:00 ~ 15:40 EMC-eHybrid: An Explicit Hybrid Particle-in-Cell Code that Conserves Energy and Momentum (Sunjung Kim, UNIST)
• 15:40 ~ 16:00 Discussion & Coffee Break 2
• 16:00 ~ 16:40 A Simulation Study of Low-Power Relativistic Jets: Structures and Dynamics of FR-I Jets (Bhattacharjee Ayan, UNIST)
• 16:40 ~ 17:00 Discussion & Coffee Break 3
• 17:00 ~ Dinner

Sessions

• EMC-eHybrid: An Explicit Hybrid Particle-in-Cell Code that Conserves Energy and Momentum

  • Speaker: Sunjung Kim (UNIST)
  • Languages:
    • Speaking: English
    • Slide: English
  • Abstract: Hybrid simulation with ion particles and inertialess charge-neutralizing electron fluid is a powerful tool for bridging the gap between magnetohydrodynamic (MHD) and full particle-in-cell (PIC) simulations. We have developed a new explicit electromagnetic code for hybrid simulation. In contrast to typical hybrid codes that do not ensure energy and momentum conservation, our code is based on a scheme that conserves total energy and momentum. The degree of conservation is controlled within desired error through an iterative method. In this talk, we describe the mathematical and numerical details of the new code. We then present a number of tests, including quiet plasma, linear waves, firehose instability, ion-beam instability, non-resonant streaming instability, collisionless shocks, and magnetic reconnection. The tests demonstrate that the code correctly reproduces the results of previous studies or analytic solutions. With its explicit nature and yet excellent energy and momentum conservation, our code would provide a valuable tool for studies of collisionless plasmas in space and astrophysical environments.

• A Simulation Study of Low-Power Relativistic Jets: Structures and Dynamics of FR-I Jets

  • Speaker: Bhattacharjee Ayan (UNIST)
  • Languages:
    • Speaking: English
    • Slide: English
  • Abstract: Relativistic jets from AGNs are broadly classified into two morphological types based on radio observations: FR-I, center-brightened and diffused jets, and FR-II, edge-brightened and strongly collimated jets with hotspots at the edges (FR: Fanaroff-Riley). While low jet power is believed to be the primary quantity that governs the dynamics of FR-I jets, observations reveal that these systems show orders of magnitude variations of radio luminosity and they are found in host galaxies with a varying range of optical luminosity, star formation rates and angle of observation. This suggests that multiple factors play important role in governing the structure and dynamics of FR-I jets. It is believed that the FR-I jets start of with ultra-relativistic speeds but decelerate and de-collimate through the formation of a spine/shear layer along the jet-back flow interface. We performed high-resolution, three-dimensional relativistic hydrodynamic simulations for a set of jet models, covering the realm of FR-I jets under different background conditions, and produce synthetic radio maps adopting models for cosmic-ray electron population and a physically motivated magnetic field distribution, which include relativistic boosting. We find that, with decreasing power, the deceleration and decollimation of the jet flow become stronger, and more extended cocoons filled with turbulence form. These in turn give rise to the flaring expansion of the jet, when it is propagating in a stratified background. The jet morphology, in the synthetic radio maps, shows a strong connection between the turbulent structures of the system and the radio emission, through the formation and growth of the spine/shear layer. Furthermore, the morphology also show a complex dependence on the angle of observation, due to boosting and projection effects. We find jets with lower angles appear more like tailed FR-I, and jets viewed edge-on appear more like lobed FR-I. On the other hand, variations of the the background profile, and the mass loading from stellar winds seem to have effects on the amount of the decollimation and deceleration of the jets, as well as the region of geometric flaring. Our results also provide a possible explanation for the observed range of jet and host luminosities for the FR-I jets.

Direction

To visit KASI, please use the map applications below.
Kakao Map   Naver Map

Registeration

To attend the meeting, interested individuals must register by filling out the registration form at the following link:
Register September Meeting

We look forward to your participation in this exciting event and hope to see you at the meeting.