Cosmic ray ionization in the D region at sunrise: Evidence from VLF phase measurements


  • M. A. Abdu,

  • S. Ananthakrishnan,

  • B. A. Krishnan,

  • O. Massambani


A temporary phase recovery observed on long-distance VLF propagation paths at sunrise is shown to be associated with cosmic-ray ionization. Simultaneous measurements of the phase carried out at Atibaia, Säo Paulo, and Jaguaräo, Rio Grande de SuI, appear to demonstrate a latitudinal effect in this phenomenon.