O-30 - The Fly's Eye stereo spectrum shows a dip centered at 10^18.5 eV and a flattening above 10^19 eV
Akeno, Haverah Park and Yakutsk see qualitatively consistent breaks (Table 5); every group observes a deficit between 10^18 and 10^19 eV relative to a single power law. Systematic offsets in fitted slope between experiments are < 0.2.
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Why this is evidence
Both H-21 (Galactic-heavy to extragalactic-light transition at the break) and H-9 (pair-production dip of extragalactic protons) predict a dip at about this energy, and its confirmation by Akeno, Haverah Park and Yakutsk is unlikely under the instrumental branch of H-37 — so this raises H-9 and H-21 jointly against the residual, without separating the two from each other.