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Field‐aligned ionospheric E ‐region irregularities and sporadic E
Author(s) -
Basu Sunanda,
Vesprini Robert L.,
Aarons Jules
Publication year - 1973
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs008i003p00235
Subject(s) - daytime , ionosphere , sporadic e propagation , physics , quiet , ionospheric sounding , backscatter (email) , f region , magnetic field , atmospheric sciences , geology , geophysics , astrophysics , meteorology , astronomy , computer science , wireless , telecommunications , quantum mechanics
A continuous series of oblique backscatter observations at 19 MHz made at Plum Island, Massachusetts (56°N invariant), over nearly half a solar cycle is utilized to derive the occurrence characteristics of aspect‐sensitive field‐aligned irregularities in the E ‐layer and their association with ground‐backscattered echoes which are propagated via sporadic E ( E 8 ) reflection. Under quiet magnetic conditions, it is found that the field‐aligned echo from E ‐layer heights, FAE( E ), displays a summer evening maximum in conjunction with the E 8 echo. A weak secondary maximum is observed in the winter with no detectable field‐aligned structures being evident in the daytime E 8 . During disturbed magnetic conditions, the E 8 ground‐backscattered echo is greatly suppressed together with a simultaneous increase of the FAE( E ) which also appear in the daytime; no seasonal control is evident. One year's continuous observations at 49 MHz with a narrowbeam antenna showed the quiet time, E 8 ‐associated FAE( E ) to be of the discrete type, whereas the FAE( E ) obtained during storms were found to be diffuse in nature. These observations are discussed from the point of view of current plasma instability theories.