S ep 2 00 5 Cosmic Ray Acceleration by E ‖ — Reconnection of Force - Free Fields

We suggest an unconventional view of the origin of most cosmic rays (CRs) in the universe. We propose that nearly every accelerated CR was part of the parallel current that maintains all force-free (f-f) magnetic fields. Charged particles are accelerated by the E‖ (to the magnetic filed B) produced by reconnection. The inferred total energy in extra-galactic cosmic rays is ∼ 10 ergs per galaxy spacing volume, provided that acceleration mechanisms assumed do not preferentially only accelerate ultra high energy cosmic rays (UHECRs). This total energy is quite large, about ×10 the parent galactic CR or magnetic energy. We argue that the formation energy of supermassive black holes (SMBHs) at galaxy centers, ∼ 10 ergs, becomes the only feasible source. We propose an efficient dynamo process which converts gravitational free energy into magnetic energy in an accretion disk around a SMBH. Aided by Keplerian winding, this dynamo converts a poloidal seed field into f-f fields, which are transported into the general inter-galactic medium (IGM) eventually. This magnetic energy must also have been efficiently converted into particle energies, as evidenced by the radiation from energetic particles. In this view CRs of the IGM are the result of the continuing dissipation, in a Hubble time, of this free energy, by acceleration in situ within the f-f fields confined within the super-galactic walls and filaments of large scale structures. In addition, UHECRs are diffusively lost to the galactic voids before the GZK attenuation time, ∼ 10 years. Similarly within the galaxy we expect that the winding by the disk rotation of the galaxy, by the rotation energy of magnetized neutron stars, and by the Keplerian winding of star formation disks are efficient sources of f-f magnetic field energy and hence the sources of galactic CR acceleration.