Propagation and stability of relativistic jets. (arXiv:1912.00235v1 [astro-ph.HE])

Propagation and stability of relativistic jets. (arXiv:1912.00235v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Perucho_M/0/1/0/all/0/1">Manel Perucho</a>

A simple look at the steady high-energy Universe reveals a clear correlation
with outflows generated around compact objects (winds and jets). In the case of
relativistic jets, they are thought to be produced as a consequence of the
extraction of rotational energy from a Kerr black hole (Blandford-Znajek), or
from the disc (Blandford-Payne). A fraction of the large energy budget provided
by accretion and/or black hole rotational energy is invested into jet
formation. After formation, the acceleration and collimation of these outflows
allow them to propagate to large distances away from the compact object. The
synchrotron cooling times demand that re-acceleration of particles takes place
along the jets to explain high-energy and very-high-energy emission from
kiloparsec scales. At these scales, jets in radio galaxies are divided in two
main morphological/luminosity types, namely, Fanaroff-Riley type I and II (FRI,
FRII), the latter being more luminous, collimated and edge-brightened than the
former, which show clear hints of decollimation and deceleration. In this
contribution, I summarise a set of mechanisms that may contribute to dissipate
magnetic and kinetic energy: Magnetohydrodynamic instabilities or jet-obstacle
interactions trigger shocks, shearing and mixing, which are plausible scenarios
for particle acceleration. I also derive an expression for the expected
distance in which the entrainment by stellar winds starts to be relevant, which
is applicable to FRI jets. Finally, I discuss the differences in the
evolutionary scenarios and the main dissipative mechanisms that take place in
extragalactic and microquasar jets.

A simple look at the steady high-energy Universe reveals a clear correlation
with outflows generated around compact objects (winds and jets). In the case of
relativistic jets, they are thought to be produced as a consequence of the
extraction of rotational energy from a Kerr black hole (Blandford-Znajek), or
from the disc (Blandford-Payne). A fraction of the large energy budget provided
by accretion and/or black hole rotational energy is invested into jet
formation. After formation, the acceleration and collimation of these outflows
allow them to propagate to large distances away from the compact object. The
synchrotron cooling times demand that re-acceleration of particles takes place
along the jets to explain high-energy and very-high-energy emission from
kiloparsec scales. At these scales, jets in radio galaxies are divided in two
main morphological/luminosity types, namely, Fanaroff-Riley type I and II (FRI,
FRII), the latter being more luminous, collimated and edge-brightened than the
former, which show clear hints of decollimation and deceleration. In this
contribution, I summarise a set of mechanisms that may contribute to dissipate
magnetic and kinetic energy: Magnetohydrodynamic instabilities or jet-obstacle
interactions trigger shocks, shearing and mixing, which are plausible scenarios
for particle acceleration. I also derive an expression for the expected
distance in which the entrainment by stellar winds starts to be relevant, which
is applicable to FRI jets. Finally, I discuss the differences in the
evolutionary scenarios and the main dissipative mechanisms that take place in
extragalactic and microquasar jets.

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