VLF Phase Changes Produced by Particle Precipitation into the Geomagnetic Anomaly During Solar Proton Events


  • A. Mendes,

  • S. Ananthakrishnan


Solar protons in the events of August 28 and September 2, 1966, produced phase disturbances on the 21.4–kHz VLF transmissions from station NSS, Annapolis, Maryland, to São Paulo, Brazil, and also on the 26.1-kHz VLF transmissions from station NPM, Hawaii, to São Paulo, Brazil. Both these paths lie well below the polar zone, but partially traverse the geomagnetic anomaly. A quantitative connection between the observed phase advances and satellite observations of the proton flux is used to calculate the length of path affected and the height changes in the disturbed portion of the waveguide. The VLF variations are accounted for by exponential ionospheric models with a reference height equal to the effective reflecting height of the sharply bound model.