Premium
Night‐time enhancements of ionospheric electron content at L = 4 during substorms
Author(s) -
Hargreaves John K.,
Hunsucker Robert D.
Publication year - 1981
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl008i007p00815
Subject(s) - riometer , ionosphere , incoherent scatter , electron density , electron , atmospheric sciences , ionization , physics , absorption (acoustics) , electron precipitation , environmental science , local time , computational physics , geophysics , magnetosphere , ion , plasma , optics , mathematics , statistics , quantum mechanics
Observations of the ATS‐6 radio beacon from Fairbanks show structured enhancements of the night‐time electron content during substorms. The probability of their occurrence increases with the level of magnetic disturbance, and they are most likely to be observed when the daily sum of K indices exceeds 20 in winter or 30 in summer. There is a remarkably close coincidence between these electron‐content enhancements and auroral absorption events detected by a riometer, though the relative magnitudes vary with the time of day. Electron density profiles measured with the Chatanika incoherent‐scatter radar confirm that the electron density at 90 km is enhanced during auroral absorption events. However, D and E‐region ionization is insufficient to account for the observed enhancement of the electron content, and an F‐region effect is a more likely cause. During one such event the F‐region critical frequency was 8 MHz.