Open AccessObservations of 50-MHz type-II coherent echoes from within the polar cap
Author(s) -
A. V. Kustov,
J. A. Koehler,
G. J. Sofko,
D. W. Danskin,
M. McKibben
Publication year - 1994
Publication title -
annales geophysicae
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.522
H-Index - 93
eISSN - 1432-0576
pISSN - 0992-7689
DOI - 10.1007/s00585-994-0765-1
Subject(s) - noon , polar , ionosphere , polar cap , doppler effect , refraction , radar , physics , geology , intensity (physics) , spectral width , f region , geophysics , optics , computational physics , atmospheric sciences , astronomy , wavelength , telecommunications , computer science
50-MHz type-II coherent echoes at geometrical\udaspect angles of 11.5° have been observed in the northern polar cap during\udpre-noon hours. The echoes had an unusually large Doppler width of 1200-1400 m s-1\udand were well correlated with strong magnetic disturbances in the range 500-1000\udnT. The dependence of intensity, spectral width and skewness versus radial\udvelocity were similar to those known from previous experiments at lower\udlatitudes and at small aspect angles. It is concluded that echo onset was due to\udthe combination of several factors, including a highly conducting ionosphere,\udthe presence of a very intense electric field, and strong radar wave refraction