Transition from VHE to EHE cosmic rays.Transition from VHE to EHE cosmic rays.

ContentsContents

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

A.A.Petrukhin

Moscow Engineering Physics Institute

13 ISVHECRI6-12 Sept. 2004

Pylos, Greece

Definition of energy regions.Definition of energy regions.

The terms HE, VHE, UHE, EHE are highly relative and are changed in time.

At present, the following definition can be suggested.

Term Energy

RemarksIn center-of-mass system In cosmic rays

HE < 2 TeV < 2·1015 eV Existing accelerators

VHE (2 – 14) TeV (2·1015 – 1017) eV LHC; the knee

UHE (14 – 140) TeV (1017 – 1019) eV The ankle

EHE >140 TeV >1019 eV Cut-off

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The knee and the ankle problems.The knee and the ankle problems.

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.

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

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EEAS < Eknee

(new particles are absent)

High altitudes

Earth’s surface

Muons

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Eknee< EEAS < Eankle

(new particles decay)

High altitudes

Earth’s surface

Muons

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Pylos, Greece

High altitudes

Earth’s surface

Muons

EEAS > Eankle

(new particles interact)

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EHE cosmic rays around cut-off.EHE cosmic rays around cut-off.

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-off2 – spectrum from Galaxy3 – uniform spectrumAccordingly 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?

1

4

3

2

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Theoretical modelsTheoretical modelsof primary spectrum formation.of primary spectrum formation.

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.

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Pylos, Greece

The model of cosmic ray The model of cosmic ray generation in plasma pinches.generation in plasma pinches.

B.A.Trubnikov, V.P.Vlasov, S.K.ZhdanovKurchatov 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.

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Energy spectrum Energy spectrum of accelerated particles.of accelerated particles.

B

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.

,- 1 3+dNE

dE

These parameters determine a proportionality coefficient only.

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Several important remarks.Several important remarks.

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.

13 ISVHECRI

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Pylos, Greece

Conclusions.Conclusions.

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

2. 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.

3. 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).

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Pylos, Greece