the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 21 Jul 2025
Rocket-Induced Lower Ionosphere Disturbances Derived from Measurements of VLF Transmitter Signals
Abstract. Rocket launch can induce large-scale atmospheric disturbances, which were mainly investigated using measurements of total electron content (TEC) in previous studies. In this study, we report the perturbations in Very-Low-Frequency (VLF) transmitter signals triggered by three rocket launch events, which, different from TEC measurements, are directly related to the D-region ionosphere. Although the rocket type, launch site, transmitting frequency, and receiver location were different, the perturbations in VLF measurements were similar in all three events. They typically occurred ~4–14 minutes after the liftoff, resulted in an amplitude change of up to 14 dB, and had a common period of ~3–7 minutes. Moreover, all perturbations consisted of two isolated pulses and this feature is notably different from previous measurements. The VLF amplitude change, in general, increases with the rocket weight and decreases with the distance from the launch site. Given the close correlation between rocket launch and VLF measurements, as well as the similarity between these events, these perturbations were likely caused by the shock acoustic waves generated during rocket launch since both the propagation speed and periods were similar.
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Status: final response (author comments only)
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RC1: 'Comment on egusphere-2025-3338', Paul Bernhardt, 26 Aug 2025
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AC1: 'Reply on RC1', Jingyuan Feng, 16 Sep 2025
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3338/egusphere-2025-3338-AC1-supplement.pdf
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AC1: 'Reply on RC1', Jingyuan Feng, 16 Sep 2025
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CC1: 'Comment on egusphere-2025-3338', Mark Clilverd, 24 Sep 2025
The events shown on the NWC transmitter for 20 September 2021 and 31 October 2022 are part of a series of on/off periods as the transmitter comes back on after it's weekly maintenance period. I attach a pdf of the NWC transmitter amplitude from Seattle covering 3 hours of interest on each day. Initially the transmitter is off and only local background noise is recorded. The NWC transmitter powers on about 06 UT, switching on/off periodically for serval hours after that. This is fairly normal behaviour for NWC after its weekly maintenance period. It is therefore unlikely that rocket launches are the cause of the large amplitude changes reported in the paper. The data shown in the pdf was recorded in Seattle. The NWC - Seattle great circle path does not pass over the rocket launch area. This also reduces the likelihood that the large amplitude changes are rocket-induced.
The first event described, on 04 August 2022, is less clearly a transmitter artifact. However the NLK transmitter switches off at 15:00 UT on the 4th August, and that is observed as a small drop in amplitude in Figure 1 as recorded at GWS in Antarctica. Thus the blue 'estimated quiet time' line shown in Figure 1 is actually the noise floor after 15:00 UT. There were no transmitter on/off periods around the start of the event, i.e., at about 14 UT as shown in the plots in the attached pdf. NLK is shown from nearby in Seattle. A clear transmitter off occurs at 15:00 UT. Also plotted in the pdf are the amplitude variations of NLK and NML received at Rothera Base in Antarctica over the same time period as Figure 1, and approximately the same amplitude range. The NLK off at 15:00 is weakly seen, but no other variations occur that like those shown in Figure 1. The great circle paths of the NLK and NML transmitter signals received at Rothera, Antarctica would be very similar to those shown to GWS in the map in Figure 1, and would this be expected to show the same behaviour for a D-region perturbation located around the rocket launch site LSO.
In summary it is unclear that a good case has been made in the paper for rocket launch influences on VLF propagation.
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RC2: 'Comment on egusphere-2025-3338', Morris Cohen, 01 Oct 2025
Review of "Rocket-Induced Lower Ionosphere Disturbances Derived 1 from Measurements of VLF Transmitter Signals" by Feng et al
Review by Morris Cohen, Georgia TechThe authors of this manuscript present three cases of VLF remote sensing associated with rocket launches, and state that VLF perturbations are indications that gravity waves launched by the rockets disturbed the D-region ionosphere and therefore VLF propagation. While rockets have been observed to create acoustic waves in the F-region, observed with GPS TEC data, the evidence for disturbances in the D-region is more limited, in part due to the difficulty of measuring it.
The manuscript is generally well written and easy to follow, although the extremely small text in the figures was a little difficult to read. But that's no big deal.
Having read the authors manuscript, I unfortunately do not agree that the reported anomalies in the VLF signal have anything to do with the associated rocket launches. Or even anything geophysical.
Let me start with a couple of zeroth-order concerns that hit me before I even got into the details. The authors report disturbances in VLF amplitude of up to 14 dB. This is an absolutely gigantic disturbance by VLF remote sensing standards. Very intense solar flares typically have only a few dB of impact on VLF. So it does not make sense that such a large disturbance would be from a rocket launch, if it were true this would have reported and observed many many times in the past. And these were not large rocket launches. Event #1 did not even reach the ionosphere, it was suborbital.
But apart from that skepticism, let me examine each event, with the benefit of a lot of experience looking at VLF data, and my own network of VLF receivers to look at:
EVENT #1
This bizarre signature in Figure 1b is, in my judgment, not a proper/working VLF recording. I had my group's set of VLF receivers operating that day across North America, so I took a look at our data to try and confirm what this signature is. In my data, I can see that the NLK transmitter turned off exactly at 15 UT, and it actually stayed off for several weeks after that, likely for maintenance. This is common late in the summer for repair work for VLF transmitters in the US, and the authors happened to pick a day when this long turn-off began. But, what's important is that you can see in Figure 1b that the amplitude of NLK drops right at 15 UT. So that level it drops to represents the noise floor. Which means the "estimated quiet time" curve, the blue curve, which is drawn for NLK, is also just measuring noise. Which also means that the strange stepping pattern between 14-15 UT is something weird. It's not really a perturbation of the signal because the authors were not measuring the signal to begin with. For NML, I again examined my data and saw that the transmitter turned off briefly, for almost exactly one minute, right at 13:55 UT. I know this because the same one-minute shutdown was visible in at least three of my receivers, so that cannot be a coincidence. But looking at 13:55 in the authors data, I do not see the 1-minute disappearance of the NML signal. This confirms the same thing as with NLK - that the data being shown is not actually a transmitter signal but some sort of receiver or local noise.
I do not know if the receiver is not sensitive enough to pick up these transmitters from so far away, or if the receiver was simply not working. But unfortunately Event #1 does not represent a geophysical measurement.
EVENT #2
I do not have corresponding data from this region, but I did have multiple receivers in Alaska which can detect the NWC transmitter. I was able to verify that the sudden dropoff in VLF amplitude observed at 7:26 UT and 7:37 UT was the transmitter actually turning off briefly, for about a minute. It was observed at precisely the same time in Alaska as the authors report. So, this was not a geophysical event at all. Therefore, the wave-like signature shown in Figure 1 was really just an artifact of the impulses from the transmitter turning off.
EVENT #2
Same as event #2, this same disappearance of the transmitter for a short time is observed in North America, at exactly the same time. This is not consistent with the idea of a gravity wave being launched by a rocket.
SUMMARY
I am sorry to say that I do not see any value in the manuscript, given that it is reporting what appears to be either a nonfunctioning receiver, or local noise. At best it is misinterpreting common VLF transmitter turn-off times as geophysical events. To be honest I am a little surprised this dataset was even worked on enough to be written up in a full manuscript and then submitted to a serious journal. I can only assume the authors put in a significant amount of time preparing this work, text and figures, and I'm sorry to say that it has not provided any useful geophysical data or result, despite the apparent time put in.
In the interest of being able to provide more information later, I have decided to de-anonymize my review. I hope the authors have better VLF data collections they can work with in future submissions.
Citation: https://doi.org/10.5194/egusphere-2025-3338-RC2 -
EC1: 'Comment on egusphere-2025-3338', John Plane, 02 Oct 2025
The authors address in this paper an interesting geophysical question: do rocket launches cause perturbations in the ionosphere which can be detected in very low frequency (VLF) transmissions? However, the second referee's report, and the comment posted by Mark Clilverd, raise serious issues concerning the quality and appropriateness of the VLF data used for the study, and hence the interpretation of apparent perturbations being caused by rocket launches. Unless the authors can provide substantive arguments to rebut these issues, submission of a revised paper is not encouraged.
Citation: https://doi.org/10.5194/egusphere-2025-3338-EC1
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Review of Rocket-Induced Lower Ionosphere Disturbances Derived from Measurements of VLF Transmitter Signals by Jingyuan Feng, Wei Xu, Xudong Gu, Binbin Ni, Shiwei Wang, Bin Li, Ze-Jun Hu, Fang He, Xiang-Cai Chen, and Hong-Qiao Hu
This paper describes new observations of in the D-region from rocket launches. This paper should be published after considering the follow changes:
(1) The authors should start with a statement of the discovery first and then discuss how they are different from previous measurements. Besides VLF waveguide amplitude and phase and radio beacon TEC data, mention should be made of ionosonde observations. We recommend the abstract be rewritten as:
Very-Low-Frequency (VLF) signals from ground transmitters propagating for long distances in the earth-ionosphere waveguide showed changes that were coincident with three rocket launch events. These launches produced acoustic disturbances in the D-region ionosphere. Although the rocket type, launch site, transmitting frequency, and receiver location were different, the perturbations in VLF measurements were similar in all three events. Moreover, all perturbations consisted of two isolated pulses and this feature is notably different from previous measurements. The VLF amplitude change, in general, increases with the rocket weight and decreases with the distance from the launch site. Given the close correlation between rocket launch and VLF measurements, as well as the similarity between these events, these perturbations were likely caused by the shock acoustic waves generated during rocket launch since both the propagation speed and periods were similar.
These events are different than rocket launches that induce (a) large-scale atmospheric disturbances in the F-region, which were mainly investigated using measurements of total electron content (TEC) in previous studies [Mendillo et al., 1975; Bernhardt, 1987] or (b) acoustic wave disturbances that are detected with high frequency sounders of the ionosphere [Mabie, et al., 2016 or Mabie and Bullett, 2022].
(2) Mention that VLF measurements along long propagation paths in the earth-ionosphere waveguide has also shown impacts of the lunar tide and man’s lack of activity on the weekend [Bernhardt, Price, and Crary, 1981].
(3) Please add these references:
Paul A. Bernhardt, Kent M. Price, James H. Crary, Periodic fluctuations in the earth-ionosphere waveguide, Journal of Geophysical Research, Vol. 86, No. A4, pages 2461-2466, April 1, 1981
Mabie, J.; Bullett, T. Multiple Cusp Signatures in Ionograms Associated with Rocket-Induced Infrasonic Waves. Atmosphere 2022, 13, 958. https://doi.org/10.3390/atmos13060958
Mabie, J.; Bullett, T.; Moore, P.; Vieira, G. Identification of rocket-induced acoustic waves in the ionosphere. Geophys. Res. Lett. 2016, 32, 43.