A Feasibility Study for D-Region Equatorial Ionosphere Research Using VLF Radiowaves
Abstract
This research report establishes experiment feasibility and presents a plan to explore dynamic properties of the equatorial D-region ionosphere. The objective is to derive geophysical information on the lower ionosphere at nighttime in near equatorial regions through the use of a new VLF radiowave measurement method which uses ionosphere mode conversion. The measurement technique uses VLF signals, that when propagating at a range of azimuthal angles (typically 190 to 360 deg) through the equatorial region (about + or - 20 magnetic latitude), undergo marked mode conversion. The mode conversion, as predicted by theory and shown by measurement, is so strong that many modes become near equal in amplitude, even modes that when entering the equatorial zone are more than 30 dB below the dominant mode. Signals are strongly mode 1 on entering the mode conversion zone, thus converted modal components provide information on ionosphere parameters causing the mode conversion process. This process is shown to be highly sensitive to ionosphere parameters. Spaced receivers located just within the mode conversion zone will provide data from a small reflection region, even though the transmitter is far away. Theoretical models of VLF propagation, used in an iterative inversion process, infer the parameters of the ionosphere. Topics covered include; measurement concept, mode conversion theory and measurement, literature review, geophysics phenomena to explore, research goals, technical approach and experiment plan. (jhd)
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 15, 1990
- Accession Number
- ADA223685
Entities
People
- V. E. Hildebrand