Previous abstract Next abstract

Session 59 - HEAD II: Cosmic Particle Accelerators.
Oral session, Tuesday, January 14
Frontenac Ballroom,

[59.03] The Highest Energy Cosmic Rays

J. W. Cronin (Enrico Fermi Inst., U. Chicago)

There is strong scientific motivation to study cosmic rays at energies >10^19 eV. It is very difficult to understand how protons or nuclei are accelerated to those energies and little is known about their sources. Recently cosmic rays of energies 3\times10^20 eV and 2\times10^20 eV have been observed. Energy loss due to interaction with the cosmic background radiation limits their source to be \leq30 Mpc from the Earth. No known astronomical object, capable of producing these energies, either in our galaxy or in the volume of 30 Mpc about us, lies near the trajectory of these cosmic rays. This fact raises the possibility that there may be sources of these cosmic rays that are not among the identified nearby (on a cosmological scale) astrophysical objects.

The flux of cosmic rays at these energies is very low, about 1/km^2/year above 10^19 eV and estimated to be about 1/km^2/century above 10^20 eV. This scientific problem will not be solved by gradualism. We have all the knowledge necessary to design a cosmic ray detector for these energies. An expansion by a factor of 60 from the 100 km^2 array in Japan is completely reasonable. The recent success of the fluorescence technique at Utah suggests that a hybrid detector of a 3000 km^2 surface array with a fluorescence detector is ideal.

The recent observation of the highest energy cosmic rays coming from the same direction suggests that point sources of charged particles exist. If these resuts are verified we will have established a "new" astronomy with charged particles, but also found another means to probe galactic and extragalactic magnetic fields.

Program listing for Tuesday