Mathematics – Logic
Scientific paper
Apr 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aps..aprj11001t&link_type=abstract
American Physical Society, April Meeting, April 29-May 2, 2000 Long Beach, CA, abstract #J11.001
Mathematics
Logic
Scientific paper
Gamma Ray Bursts (GRB) deliver very high intensity photons with energies from 10 keV to over 100 MeV at a irradiance of 10^30 (30 km/R)^2 Watt/cm^2. This is in the nonlinear QED regime and the induced wakefield is close to the Schwinger field (E ~^16 V/cm). Protons and electrons can be accelerated in such a strong field to 10^21 eV/km in the vicinity of the GRB source. The maximum acceleration is limited by the critical Schwinger field times the length of the field: q ( E (= 10^16.5 V/cm) ( L ((1000 km) = 10^24 eV. Trains of such wakefields are expected in the outflow of photons from GRB's, which gives a Chapman-Kolmogorov type power energy spectrum [Chandrasekhar, 1953; Mima et al. 1991], which is close to a Bremsstrahlung-type spectrum, f(E) = E^-a (a = 1). Some of the accelerated protons can have energies as high as 10^23 eV. The secondary pions and their daughters (neutrinos) that may be produced in-situ near the acceleration site of the GRB can have energies around 10^22 eV (= 1.6 ( 10^10 erg). The neutrino flux from the semi-daily occurrence of GRB's (with energy output of ~ 10^52 erg can provide a flux of high intensity EHE neutrinos in the universe as a function of the acceleration efficiency coefficient (k): I( (E ( 10^21 eV) = 5k (10^52 eV)/(1.6 ( 10^10 erg)/4(pi)R^2/day = 1 /km^2 yr (for k = 1% *). *(cf. Laser wakefield experiments with Petawatt indicated k = 5 ~ 10% for protons [M. Key, 1999].) A compact photonic acceleration mechanism is thus suggested as a candidate for the origin of extremely high energy cosmic rays (EECR). Observed characteristics of EECR beyond energies of several 1019 eV pose a number of challenges and opportunities for physics and astrophysics. Foremost among them is the apparent defiance or violation of the proton energy cutoff of Greisen-Zatsepin-Kuzmin (GZK). The other is the apparent correlation in some of ECR events. And the most important is the difficulty to accelerate particles by the conventional Fermi mechanism to reach such high energies. We suggest that the intense photon flux emanating from a gamma ray burst is capable of yielding a sufficiently robust and rugged plasma structure suitable to accelerate protons and other charged particles to extreme high energies ( ~ 10^22 eV) over thousands of kilometers in the GRB atmosphere. Photon flux above a certain threshold can self-modulate in the plasma to create longitudinal (as well as transverse) structures that help snowplow and accelerate charged particles. The sustained large flux of photons maintains the acceleration by successive flux to repeat the process once a particular class of photons give up energies to particles and red-shift. The decrease of plasma density away from the GRB further facilitates this process, providing ever greater coherence (acceleration) length. The stochastic repetition of this process yields a power-law energy spectrum with an exponent of -1. Such compact prompt intense acceleration of protons in the vicinity of GRB manifests through neutrinos (by proton-proton or proton-photon collisions near GRB). These neutrinos can propagate over a cosmological distance without decay or loss until reaching and colliding with relic neutrinos in our Super-Cluster (Virgo), eventually converting themselves into EECR particles such as protons and photons of energies of ~ 10^20 eV. The estimated neutrino energy flux and spectrum are consistent with observation and have a number of implications on EHECR, cosmological origin, and neutrino physics. Other high field astronomical sites such as the core and jets of Active Galactic Nuclei can have lesser but similar accelerations.
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