Transition from VHE to EHE cosmic rays'

1
Transition from VHE to EHE cosmic rays.
A.A.Petrukhin
Moscow Engineering Physics Institute
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece

• Contents

• Definition of energy regions

• The knee and the ankle problems

• EHE cosmic rays around cut-off

• Acceleration of particles in plasma pinches

• Consequences for cosmic ray origin

• Conclusions

2
Definition of energy regions.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
The terms HE, VHE, UHE, EHE are highly relative
and are changed in time.
At present, the following definition can be
suggested.
3
The knee and the ankle problems.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece

• Now the knee is explained as maximum particle
  energy
• which can be kept in Galaxy

• The ankle in its turn is explained as the
  energy at which flux of extragalactic
• cosmic rays begins to prevail over the flux
  of galactic ones

• But if to explain the knee by inclusion of new
  particles (states of matter)
• which decay into leptons (directly or
  through W? and Z0-bosons),
• then the ankle will correspond to critical
  energy for new particles
• at which probabilities of interaction and
  decay are equal.
• At higher energies, new particles mostly
  interact and missing energy is
• disappeared.

4
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
5
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
6
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
7
EHE cosmic rays around cut-off.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
Two various versions of the knee and the ankle
origin give the different behavior of cosmic ray
energy spectrum around cut-off.
Figure shows various models of primary
spectrum 1, 2, 3 without the knee and the
ankle, when the spectrum must return back to
the same slope as at energies below the knee 1
without cut-off 2 spectrum from Galaxy 3
uniform spectrum Accordingly 4 spectrum with
the knee and the ankle
In model with constant ? ?2.7 (without the knee
and the ankle) dip and bump appear very
naturally. But how to obtain the primary
spectrum with constant ? ?2.7?
8
Theoretical modelsof primary spectrum formation.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
The models of cosmic ray production and
acceleration can be divided in two basic
groups

• explosion type, f.e. Supernova

• multiple interaction type, f.e. Fermi
  mechanism.

However
1. There is no model, which describes primary
spectrum in the full energy region.
2. There is no model, which unambiguously
predicts the value of ?.
But
One very interesting model exists, in which
these problems were solved 15 years ago.
9
The model of cosmic ray generation in plasma
pinches.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
B.A.Trubnikov, V.P.Vlasov, S.K.Zhdanov Kurchatov
Institute, Moscow
1. Int. Conf. on Plasma Physics, New Delhi,
India, 1989, v.1, p.257.
2. In the book "Hydrodynamics of Unstable
Media", 1996, p.114, CRC Press. Inc. Boca
Raton, New York, London, Tokyo.
The main idea of this model is the following.
In cosmic plasma (of any origin) electrical
discharges "cosmic lightnings" can occur, at
which cylindrical pinches are formed, similar to
laboratory ones.
Two basic instabilities of plasma pinches are
known snaky and neck.
In the latter case plasma jets are squeezed out
of pinch neck.
These jets are the accelerated particle beams.
10
Energy spectrum of accelerated particles.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece
Snaky Neck
It is shown that energy distribution of particles
in jets has the following form
which does not depend on pinch sizes, currents in
pinches and other parameters.
These parameters determine a proportionality
coefficient only.
11
Several important remarks.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece

• In the model the well-known equations of
  plasma physics are used only.

• Model has no free parameters except for
  absolute intensity.

• Model predicts for the energy spectrum slope
  the unambiguous value ? 2.73

• Model has no limitation for accelerated
  particle energy since in plasma
• pinch neck

density ? ? ?, when its radius r ? 0

• The composition of accelerated particles will
  be the same as
• composition of cosmic plasma, which
  consists mainly of
• hydrogen.

• Model explains the absence of point sources of
  cosmic rays since
• pinches, f.e. near Supernova, can be
  oriented in any direction.

• At the same time, generation of particles in
  narrow jets in
• cylindrical pinches can explain the
  appearance of correlated
• particles.

12
Conclusions.
13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece

• It is impossible to solve the cut-off problem
  without solving
• the knee and the ankle problems.

• In any case, at interpretation of results of
  cut-off investigations,
• it is necessary to take into account the
  possibility of existence
• of primary spectrum with a constant slope.

• It is desirable to decrease the threshold energy
  in existing EAS detectors
• (f. e. South part of PAO) and especially in
  future projects
• (f. e. North part of PAO) to have a
  possibility of investigations
• of energy spectrum in more wide interval (at
  least lower than the ankle).