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Transition from VHE to EHE cosmic rays.

A.A.Petrukhin. Moscow Engineering Physics Institute. Transition from VHE to EHE cosmic rays. 13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece. Definition of energy regions. Contents. The knee and the ankle problems. EHE cosmic rays around cut-off.

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Transition from VHE to EHE cosmic rays.

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

  3. 13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece • Now the knee is explained as maximum particle energy which can be kept in Galaxy 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.

  4. 13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece

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  7. 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 EHE cosmic rays around cut-off. 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. 13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece The models of cosmic ray production and acceleration can be divided in two basic groups: Theoretical modelsof primary spectrum formation. • 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. 13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece B.A.Trubnikov, V.P.Vlasov, S.K.Zhdanov Kurchatov Institute, Moscow The model of cosmic ray generation in plasma pinches. 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. 13 ISVHECRI 6-12 Sept. 2004 Pylos, Greece Energy spectrum of accelerated particles. 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. 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. Several important remarks. • 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. 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. Conclusions. • 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).

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