COSMIC RAY ACCELERATION and TRANSPORT LECTURE 3: Research Topics. Pasquale Blasi INAF/Arcetri Astrophysical Observatory. 4th School on Cosmic Rays and Astrophysics UFABC - Santo André - São Paulo – Brazil. WHAT NEXT?. We have found the elegant results of the theory of DIFFUSIVE SHOCK
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
INAF/Arcetri Astrophysical Observatory
4th School on Cosmic Rays and Astrophysics UFABC - Santo André - São Paulo – Brazil
ALL THESE PHENOMENA SUGGEST THAT WE NEED TO MOVE BEYONDTHE TEST PARTICLE APPROXIMATION
NON LINEAR THEORY OF DIFFUSIVE SHOCK ACCELERATION
Conservation of Momentum
for cosmic rays
THIS IS THE LEAST UNDERSTOOD ASPECTS OF ALL !
Ideal Collisionless Shock (More) Real Collisionless Shock
WHICH PARTICLES AND HOW MANY PARTICLES
ENTER THE ACCELERATION CYCLE?
Maxwellian for the Downstream gas
Rsub, ξand η
Pinj = pth,2
OUTPUT OF THE
PB, Gabici & Vannoni 2005
Remember that we showed that a particle diffuses along a direction z where
there is an ordered magnetic field B0 because of a small perturbation dB
perpendicular to B0.
In this process the particles lose momentum in the z direction and this p
Is transferred to the dB waves.
This equals the momentum gained by the waves:
And imposing a perfect balance:
In the ISM this is ~10-3 yr-1 but
close to a shock front the grow
can be even larger!!!
dB IS AMPLIFIED BY PARTICLES
Bell 2004, Amato & PB 2009
SMALL PERTURBATIONS IN THE LOCAL
B-FIELD CAN BE AMPLIFIED BY THE
SUPER-ALFVENIC STREAMING OF THE
Particles are accelerated because there is
High magnetic field in the acceleration region
High magnetic field is present because particles
Are accelerated efficiently
Without this non-linear process, no acceleration
of cr to High energies (and especially not to the
TYPICAL THICKNESS OF FILAMENTS: ~ 10-2 pc
The synchrotron limited thickness is:
to higher values of the
Bohm Diff without
50 100 150 200
PB, Amato & Caprioli, 2007
Data from Bertaina et al. 2008
Morlino, Amato, PB & Caprioli 2010
ION Temperature LOWER because of CR acceleration
NEUTRAL Temperature HIGHER because of charge exchange
BROAD BALMER LINE IS NARROWER
NARROW BALMER LINE IS WIDER
Helder et al. 2009
INFERRED EFFICIENCY of CR ACCELERATION 50-60% !!!
Sollerman et al. 2003
Broadening of the narrow line hints to a mechanism for heating of the neutrals upstream
on scales shorter than ionization scales TURBULENT HEATING
CHARGE EXCHANGE UPSTREAM
A broadened narrow Ha line from upstream shows that the
neutrals and ions have some level of charge exchange
different bulk velocities and/or T’s between the two components
Morlino, Amato & PB 2009
Courtesy of S. Funk
Velocity of scattering centers in the shock frame NOT velocity of the plasma
In general the velocity of scattering centers is small and there is no problem
BUT AMPLIFIED MAGNETIC FIELD high velocity ???
VERY MACROSCOPIC CONSEQUENCES ON SPECTRA!
Caprioli, PB, Amato 2010
The dynamical reaction of nuclei on the shock structure
turns out to be VERY IMPORTANT
Caprioli, PB, Amato 2010
Berezinsky et al. 2005
Aloisio et al. 2007
Allard et al. 2005-2008
From Kampert 2008
Aloisio, Berezinsky, PB & Ostapchenko 2008