High-Frequency Channel Modeling Based on the Multi-Source Ionospheric Assimilation Model

Round 1

Reviewer 1 Report

The paper deals with a problem of oblique sounding of the ionosphere. This topic is very important for monitoring and determination of key parameters of the ionosphere in remote and hardly accessible regions such as oceans and high mountains. The authors use an assimilation model of the ionosphere in a particular region above the mountain area in China in order to model the propagation of a HF signal. For several time intervals (quiet and disturbed), several key parameters of the signal distortion were estimated during the propagation for long distances and reflection from the model ionosphere such as group delay, propagation mode, propagation loss, time delay, Doppler shift, etc. The results look very promising. However, the modeling technique and results need more accurate and complete description (see comments below).

 

 

Comments:

1. Equation (1): what is the difference between h and h*?

2. Line 133: The function S is not presented in Eq (1)

3. Line 146: Where is tu used?

4. Equation (4). What is the dimension of tc?

5. Line 176: What is “angular frequency”?

6. Line 182: How do the authors distinguish between ordinary and extraordinary waves?

7. Line 204: Why do the authors not take the F1 layer into account?

8. Line 210: Is the TECm vertical TEC?

9. Figures 2 – 7, 9-14 should be described in more detail.

10. Captions of Figures 3 – 7: What are “other parameters” shown in Figure 2? I see only Group Path vs Doppler shift. Please clarify

11. Line 308: What is the origin of disturbance?

12. Line 309: “Figures 1 and 5 show a similar pattern.” Please check the numeration of Figures.

13. Line 315: I did not find Equation (13)

14. Lines 370-371: What is the meaning of the ionospheric disturbance period? Please explain.

15. Lines 380-384: The “experimental results” are not shown. How the authors can conclude that the “simulation prediction was close to the HF oblique sounding experi-383 mental results.”

16. Lines 388-393: This paragraph is more appropriate for the Discussion Section rather than for Conclusions.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

It cannot be said that the problem considered еру the manuscript is completely new. A large number of articles have been published on HF channel modeling.

This manuscript is an illustration of the possibilities of high frequency channel modeling using two closely spaced oblique sounding radio paths to measure the characteristics of HF signals at 4 MHz and 10.8 MHz. The simulation is carried out using the background electron density generated by the ionospheric assimilation model and ray tracing calculations. Standard relationships are used for Doppler shift, received signal amplitude estimation, etc. The scattering functions of the received signal in the HF channel are presented. As a result, the authors conclude that the proposed HF channel model in the form of Doppler broadening is close to the results of oblique sounding on two radio paths. The scattering functions of the received signal in the HF channel are presented. As a result, the authors conclude that the proposed HF channel model in the form of Doppler broadening is close to the results of oblique sounding on two radio paths.

The article can probably be accepted for publication, but the authors should make some corrections.

1. The main drawback of the manuscript is the insufficient discussion of the results. Observations were carried out around the clock, so the state of the ionosphere over the region of oblique sounding changed over time. In the manuscript, there is absolutely no analysis of the state of the ionosphere during the experiments.

2. It is necessary to quantify and present in the manuscript the deviation of the difference between the simulation results and the experimental ones.

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

All my comments have been addressed properly. Perhaps, Section 5 might be called “5. Discussion and Summary”

Reviewer 2 Report

The authors paid great attention to the revision of the manuscript in accordance with my comments. An analysis of the ionosphere condition during the experiments was carried out. The authors added a figure arguing the influence of the ionosphere on the Doppler shift on both oblique paths. The deviations of the difference between the simulation and experimental results are discussed. With these changes, the article has improved a lot.

I think that the manuscript can be accepted for publication.