Real‐time HF ray tracing through a tilted ionosphere

Abstract

[1] High-frequency (HF) direction-finding (DF) systems measure the angles of arrival of signals at selected frequencies. With this information, ray tracing can accurately determine the location of the HF transmitters if the three-dimensional (3-D) electron density (Ne) distribution between the DF site and the transmitters is known. The usual approach is to use an ionospheric model like the International Reference Ionosphere (IRI) as a proxy for the density distribution. We describe a more realistic approach developed in cooperation with Codem Systems in Merrimack, New Hampshire. A collocated digisonde at the DF site measures the vertical electron density profile and the local ionospheric tilt, providing, in real time, the inputs for the construction of the 3-D Ne distribution. The vertical profile is automatically obtained from the Automated Real Time Ionogram Scaler with True Height (ARTIST)-scaled ionogram and the local tilt from the sky maps recorded after each ionogram. The characteristics of each layer, for example, critical frequencies and peak heights, are expressed as a function of latitude l and longitude Ψ. In the neighborhood of the DF site each characteristic, for example,The coefficients C 7 and C 8 for any given azimuth direction are determined with the use of the Union Radio Scientifique Internationale/CCIR coefficients (which are also used in IRI), and the calculation of C l and C Ψ makes use of the measured ionospheric tilt data; f o F 2 m is the local, measured f o F 2 value. When the measured density profile and tilt data are available, the derived 3-D density distribution represents the instantaneous ionosphere structure near the site. The numerical ray tracing includes the effects of the magnetic field and properly treats the spitze effect, making the ray-tracing program especially useful for small distances. Ray tracing through simulated tilts shows that the differences in ground distances for one-hop high-frequency (HF) propagation vary from about 1 to 100 km depending on the assumed tilts and distances. Operational tests for distances up to approximately 100 km have demonstrated good results in determining the transmitter location in real time and have illustrated the importance of using the actual ionospheric profiles and tilts in the ray tracing.

Application of the nudged elastic band method to the point-to-point radio wave ray tracing in IRI modeled ionosphere

“…For quiet conditions, radio wave ray tracing calculations usually show good agreement with the observational data (Huang et al, 2006;Kotovich et al, 2010;Settimi et al, 2013), while storm time conditions cause problems. Another important issue concerns the methods for the ionospheric ray tracing, where position of the receiver and transmitter is fixed.…”

Using IRI and GSM TIP model results as environment for HF radio wave propagation model during the geomagnetic storm occurred on September 26–29, 2011

“…Different methods are widely used to determine ionospheric parameters: simplified analytical representation, observational data, tomography, models, etc. (Huang and Reinisch, 2006;Tsai et al, 2010;Zhbankov et al, 2010;Coleman, 2011;Kryukovsky and Kiryanova, 2011;Pezzopane et al, 2011;Azzarone et al, 2012;Karpachev et al, 2012;Warrington et al, 2012;Settimi et al, 2013;Cervera and Harris, 2014). Many published articles analyze RWP modeling in the middle (Borisova et al, 2009;Lockwood, 1981;Houpis and Nickisch, 1991;Settimi et al, 2013), high (Mingalev et al, 1988;Hunsucker and Hargreaves, 2003;Zaalov et al, 2003;Blagoveshchensky et al, 2010;Warrington et al, 2012;de Larquier et al, 2013) and low latitude ionosphere (Tsai et al, 2010;Zhbankov et al, 2010;Karpachev et al, 2012).…”

Pilot Ionosonde Network for Identification of Traveling Ionospheric Disturbances

“…The component “ i ” with the maximum amplitude A Ni is currently used for the FAS TID analysis described in section 2.2. Huang et al (), using the Huang and Reinisch () ray tracing code, have verified that the time variations of the measured HF signal parameters are equivalent to those of a free‐space signal reflected at a sinusoidally undulated mirror at height z 0 moving with velocity V p . This mirror is represented by the dashed line in Figure .…”