Characteristics of field-aligned density depletion irregularities in the auroral ionosphere that duct Z- and X-mode waves

被引:11
作者
James, H. G. [1 ]
机构
[1] Commun Res Ctr Canada, Ottawa, ON K2H 8S2, Canada
关键词
D O I
10.1029/2006JA011652
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The small-scale and two-point nature of the Observations of Electric-field Distributions in the Ionospheric Plasma - A Unique Strategy C (OEDIPUS-C, OC) dual-payload propagation experiment in the auroral ionosphere in 1995 has permitted improved measurements of the parameters of magnetic field-aligned density irregularities. Comparatively strong and dispersed pulses were observed at frequencies f just above the electron plasma frequency f(p) when the electron gyrofrequency f(c) was less than f(p). The waves are interpreted as quasielectrostatic Z-mode propagation with dispersion surfaces close to those of the Langmuir solutions in wave vector space, albeit at somewhat lower refractive indices of about 50. If mission length surveys of the Z-wave intensities are aligned with histories of f(p) at the payload and of the strength of X- and fast Z-mode ionospheric reflection echoes, a strong positive correlation is found at momentary relative depletions of the ambient density. These observations are taken as evidence of ducting in the field-aligned depletions. The spectra of these strong Z-mode transmissions are similar to those of slow Z ducted spectra observed at similar f, f(p), and f(c) values in the OEDIPUS-A experiment in 1989. The magnitudes of the density depletions are found to lie in the range 7-21% and to have cross-field dimensions of a few kilometers. The present duct dimensions are of the same order as the previous findings from ionospheric X- mode electromagnetic echoes on OC, but the depletions are up to 10 times deeper. Measurements of ducting irregularities can lead to insights into their formation. This will be important for our understanding of the interfaces of the ionospheric or magnetospheric topologies where irregularity formation is an important link in the large-scale flow of energy.
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页数:11
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共 32 条
[1]  
[Anonymous], 1996, EOS T AM GEOPHYS UNI
[2]  
Benson RF, 2006, LECT NOTES PHYS, V687, P3
[4]  
Budden K.G., 1985, The Propagation of Radio Waves: The Theory of Radio Waves of Low Power in the Ionosphere and Magnetosphere, V1st ed.
[5]   WAVE DUCTING IN DIFFERENT WAVE MODES [J].
CALVERT, W .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 1995, 100 (A9) :17491-17497
[6]  
Chugunov YV, 2003, RADIO SCI, V38, DOI 10.1029/2001RS002531
[7]   THE GLOBAL DISTRIBUTION OF IONOSPHERIC SMALL-SCALE IRREGULARITIES FROM TOPSIDE SOUNDING DATA [J].
DENISENKO, PF ;
ZABOTIN, NA ;
BRATSUN, DS ;
PULINETS, SA .
JOURNAL OF ATMOSPHERIC AND TERRESTRIAL PHYSICS, 1992, 54 (10) :1303-1309
[8]   First 100 ms of HF modification at Tromso, Norway [J].
Djuth, FT ;
Isham, B ;
Rietveld, MT ;
Hagfors, T ;
La Hoz, C .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2004, 109 (A11)
[9]   Modeling of field-aligned guided echoes in the plasmasphere [J].
Fung, SF ;
Green, JL .
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS, 2005, 110 (A1)
[10]   Guided echoes in the magnetosphere: Observations by Radio Plasma Imager on IMAGE [J].
Fung, SF ;
Benson, RF ;
Carpenter, DL ;
Green, JL ;
Jayanti, V ;
Galkin, IA ;
Reinisch, BW .
GEOPHYSICAL RESEARCH LETTERS, 2003, 30 (11) :43-1