The vertical structure of rocket-exhausted ionospheric electron density depletion was captured by COSMIC-1 radio occultation data. Reconstructs the three-dimensional tubular electron density hole from rocket exhaust based on multi-source observations and simulation. The evolution of REDs should be mainly divided into three stages: “rapid formation, diffusion-driven growth, and diffusion-driven recovery”.
During rocket launches, the ionosphere undergoes a range of physical and chemical interactions, resulting in various disturbances. Rockets traveling at supersonic speeds through the mesosphere, alongside the explosive release of exhaust gases, generate shock waves and Atmospheric Acoustic-Gravity Waves (AGWs) (e.g., Arendt, 1971; Noble, 1990; Jacobson and Carlos, 1994; Li et al., 1994). These disturbances induce traveling ionospheric disturbances (TIDs), which are frequently observed within a certain range along the rocket's trajectory and have been extensively documented (e.g., Kakinami et al., 2013; Lin et al., 2017a, b; Chou et al., 2018; Yasyukevich et al., 2024). The rocket's propulsion relies on rapidly ejecting large volumes of combustion products, part of which are released into the atmosphere and can impact climate and stratospheric ozone (Barker et al., 2024). As the rocket ascends into the ionosphere, these exhaust gases expand rapidly in the ionosphere, they act like a “snowplow”, pushing background plasma outward and forming a density pile-up layer (e.g., Booker, 1961; Mendillo, 1988). Simultaneously, the exhaust pressure drops sharply to match the background ionosphere, transitioning into a free diffusion process. This exhaust, rich in H2O, H2, and CO2, undergoes a series of chemical reactions during diffusion, further depleting ionospheric electrons and forming ionospheric electron density “holes” known as rocket-exhausted depletions (REDs) (e.g., Mendillo et al., 1975, 2008; Bernhardt et al., 2001). These chemical reactions produce excited oxygen atoms (O(1D)) and hydroxyl radicals (OH), which emit 630 nm red light and 135.6 nm ultraviolet emissions, observable by airglow imagers, sounding rockets, and satellite instruments (e.g., Yau et al., 1985; Mendillo et al., 2008; Liu and Shepherd, 2006; Park et al., 2022).
REDs were first detected by sounding instruments (Booker, 1961) and through Faraday rotation of satellite signals (Mendillo et al., 1975; Wand and Mendillo, 1984). Subsequent studies primarily relied on GNSS-TEC data to capture the 2D horizontal distribution of REDs (e.g., Mendillo et al., 2008; Furuya and Heki, 2008; Nakashima and Heki, 2014). Furthermore, Park et al. (2015, 2016, 2022) observed associated electron density depletions using in situ satellite measurements even 6 h after the rocket launch, and captured 2D depletion distributions using satellite ultraviolet spectrometers. Numerous observations indicate that REDs typically emerge around 5–7 min after launch, persisting for 0.5 to 6 h (e.g., Bernhardt et al., 2001; Mendillo et al., 2008; Nakashima and Heki, 2014; Park et al., 2016). The depletion regions generally extend laterally along the rocket's trajectory, with widths of approximately 300–500 km and lengths exceeding 2000 km (e.g., Liu et al., 2018; Ozeki and Heki, 2010; Mendillo et al., 2008; Zhao et al., 2024). Inside REDs, total electron content (TEC) drops by 3–22 TECU compared to the background ionosphere (e.g., Liu et al., 2018; Park et al., 2022; Zhao et al., 2024), while maximum electron density reductions range from 20 % to 95 % (e.g., Furuya and Heki, 2008; Park et al., 2016; Wand and Mendillo, 1984; Mendillo et al., 2008; Zhao et al., 2024).
Current REDs observations largely rely on GNSS-TEC data, with a few nighttime launches observable through optical imaging (e.g., Mendillo et al., 2008; Park et al., 2022), which mainly capture horizontal 2D structures. Vertical structure observations remain scarce. A limited number of studies using incoherent scatter radar (e.g., Wand and Mendillo, 1984; Bernhardt et al., 1998, 2012; Zhao et al., 2024) have captured vertical profiles of REDs. Zhao et al. (2024) reported observations of ionospheric REDs structure during two rocket launches, and the results showed that REDs can extend to
In this study, we obtained clear observations of the vertical structure of REDs using COSMIC-1 occultation data. Combining multi-source observations from COSMIC-1, Swarm satellites, and ground-based GNSS, we revealed the 3D hollow-tube structure of REDs and their evolutionary characteristics, offering a new perspective on rocket launch ionospheric disturbances. Additionally, high-resolution 3D simulations further validated the feasibility and reliability of the depletion modeling.
Event-1: on 22 May 2014, an Atlas-V Rocket was launched from Cape Canaveral Air Force Station by United Launch Alliance (ULA) at 13:09 UT. Event-2: on 20 May 2015, a similar Atlas-V was launched at the same station by ULA at 15:09 UT. REDs from two launch events were reported by Park et al. (2016) using satellite in situ observations. This study primarily focuses on Event-1, while Event-2 serves as a supplementary case to provide horizontal observational data where Event-1 lacks coverage. Detailed trajectories of these two launches were not available; therefore, we derived the trajectories based on the rocket depletion observations by Park et al. (2015, 2016) and the Atlas-V user manual, as depicted in Fig. 1c. The launch information and Atlas-V user manual can be accessed from the ULA website:
Observation Data Distribution and Details.
The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation data have been widely applied in studies of the atmosphere, climate, and ionosphere. The gridded data products derived from COSMIC occultation observations have been used in rocket-induced depletion (RED) studies (Park et al., 2022). Moreover, COSMIC occultation data are frequently employed to monitor and investigate ionospheric disturbances caused by special events such as earthquakes, tsunamis, and sporadic Es layers (Astafyeva et al., 2011; Arras and Wickert, 2017; Yan et al., 2018, 2020, 2022; Qiu et al., 2021). A detailed assessment of the feasibility and reliability of COSMIC radio occultation data can be found in Lei et al. (2007) for COSMIC-1 and in Lin et al. (2020) for COSMIC-2. In this study, we utilize the electron density and total electron content (TEC) data derived from COSMIC-1 occultations (Level 1b, 1/60 Hz; product identifiers: ionPhs_repro and podTec_repro) to identify electron density depletions induced by rocket exhausts and to determine their corresponding altitude information. The COSMIC-1 datasets are provided by the COSMIC Data Analysis and Archive Center (CDAAC) and are available at
To investigate the horizontal spatial distribution of the REDs, we used data from ground-based GNSS receivers. The vertical total electron content (TEC) was calculated following the method described by Yan et al. (2017). The GNSS receiver data were obtained from the SOPAC & CSRC database service website (
The calculated STEC was projected onto the sub-ionospheric point (SIP) on the Earth's surface using an ionospheric single-layer model. The vertical TEC (VTEC) can then be derived from the following equation (Jin et al., 2008):
Based on the TEC data, the identification method proposed by Pradipta et al. (2015) for ionospheric plasma bubbles was adopted and optimized using a third-order polynomial fitting to capture the specific characteristics of REDs. This approach allows for a more accurate extraction of the absolute vertical TEC depletion values and provides a clearer representation of the horizontal distribution features of the REDs.
The Swarm constellation, comprising three satellites at orbital altitudes of 450–550 km, is equipped with Langmuir probes to measure electron density, enabling the observation of REDs. Park et al. (2016) first reported Swarm observations of REDs, with detailed descriptions of the instruments and data available in their study. The Swarm data are sourced from the European Space Agency (ESA):
The formation of ionospheric electron density depletion is closely linked to the diffusion patterns and chemical reactions of rocket-exhaust (e.g. Bowden et al., 2020; Zhao et al., 2024). Previous studies have shown that releasing around 4 kg of water vapor at 210 km altitude can cause significant depletions, with the affected area expanding at higher altitudes (e.g. Hu et al., 2010, 2011, 2013; Huang et al., 2011). Factors like release trajectory, exhaust flow rate, source speed, geomagnetic declination, and background winds further influence depletion patterns (e.g. Zhao et al., 2016; Feng et al., 2021; Gao et al., 2017). In this study, we also incorporate the effects of daytime electric fields and photoionization to improve simulation accuracy.
Rocket launches consume up to 79 % of their fuel below 80 km altitude, representing the predominant portion of total fuel consumption (Barker et al., 2024). The ATLAS-V first-stage core carries 284 t of fuel, with boosters attached to it, while the second stage carries 20.83 t. The first stage alone accounts for over 93 % of the total fuel load. As it releases most exhaust in the lower atmosphere and below the ionospheric D-region, the influence of first-stage exhaust on the REDs analyzed in this study is negligible. We selected the second stage ignition (
The main chemical equations involved in the simulation release.
The diffusion equation proposed by Bernhardt (1976) for neutral material release calculates the molecular density of a point source as:
The diffusion coefficient (
By moving point sources along the rocket trajectory, we simulate continuous rocket exhaust diffusion (e.g. Zhao et al., 2016; Feng et al., 2021). H2O and H2 released into the ionosphere mainly participates in the following reactions as Table 1, to deplete ionospheric electrons:
Parameter settings and background model for numerical simulation.
Figure 1a and b presents the rocket trajectory and observed depletion locations for Event-1. Figure 1d and e presents the vertical profiles of TEC and electron density from COSMIC-1 satellite C01 paired with navigation satellites G01 and G11, labeled as C01–G11 and C01–G01. Both radio occultation events occurred within 10 min, with triangular markers indicating the depletion centers and corresponding UT timestamps. For the C01–G11 at UT 13:58, about 40 min after the ATLAS-V rocket's second-stage ignition, depletion was observed between 197–300 km altitude, showing a maximum TEC drop of
As supporting evidence, these REDs were previously reported by Park et al. (2015, 2016) using Swarm in situ measurements, which are also retrieved in this study (Fig. 1c). Swarm-Alpha/Bravo/Charlie are marked in different colors, with times of minimum depletion labeled. The Swarm observations occurred around 14:00 UT. Altitudes are shown in Fig. 1c, where Swarm A and C orbited at 469.9 km, and Swarm B at 518.5 km. The north-south REDs lengths recorded by Swarm A, C, and B were 419, 491, and 277 km, respectively, with maximum electron density reductions of about 45 %, 39 %, and 5 %. The horizontal distribution of REDs measured by Swarm closely followed the rocket's projected ground track.
Figure 2 presents the REDs characteristics extracted from ground-based GNSS TEC data for Event-1 and Event-2. Figure 2a shows the GNSS data distribution for Event-1, Fig. 2b shows the corresponding time series of the identified REDs in differential TEC (DTEC). The vertical axis is arranged according to the closest distance from the observation points to the rocket trajectory, indicating the observed REDs' distance from the rocket path. Due to the offshore launch and limited temporal coverage, most GNSS data failed to capture the REDs. Some ionospheric piercing points (IPPs) near the second-stage ignition site and occultation region did not capture RED signatures because they arrived 2–3 h after launch, by which time the RED had drifted northward out of the area. To improve visualization, the data points without detected REDs signatures are semi-hidden. Figure 2a also shows the horizontal TEC distribution map, where red small triangles indicate the recording position for each data curve at the launch time, and black arrows mark the time sequence of data measurement. For Event-1, the GNSS effective observation data is sparse; the maximum depletion amplitude observed occurred approximately 1.5 h after the launch, with a magnitude of about 9 TECU (1 TECU
GNSS TEC data for Event-1 and Event-2.
Due to sparse GNSS coverage along Event-1's rocket trajectory, accurate horizontal depletion scales could not be determined. Therefore, Event-2 serves as a reference, given the identical rocket model, similar launch trajectory, and matching local time. Figure 2c–f depicts the horizontal TEC distribution and time-series depletion signals from Event-2. Figure 2c and e shows the IPPs for TEC observed at 300 km by the G14 and G31. The corresponding time-series signals in Fig. 2d and f are arranged by the shortest distance to the rocket trajectory, similar to Fig. 2b. For Event-2, the REDs extended up to
Figure 3 shows the simulation result of H2O release and electron density depletion for Event-1. Figure 3a–d illustrates the evolution of H2O molecular density along the rocket flight path. Water vapor diffuses rapidly within the first few minutes, spreading laterally along the trajectory, with a vertical range of around 100 km. Molecular density decreases gradually as diffusion slows, reaching maximum spread at about 25 min, before gravitational settling pulls it to lower altitudes, ceasing its contribution to depletion consistent with Zhao et al. (2024). Figure 3e–h shows electron density changes during water release. Depletion forms within 1–2 min, spreading for about 20 min. And depletion mainly extends laterally along the trajectory, reaching 180 km upwards and 50 km downwards. Recovery follows, with faster recovery at lower altitudes due to higher background density, showing an upward drift pattern consistent with Zhao et al. (2024). At 50 min, the depletion reaches a thickness of 150–300 and 200–500 km in vertical range. We have included multiple detailed depletion evolution videos in the video materials (Videos S1–S3 in the Supplement), which visualize the simulated 3D spatiotemporal evolution processes.
Simulation molecular density distribution of H2O and electrons.
In the simulation results, Fig. 4a shown the distribution of the vertical TEC variation. The simulated TEC variation intensity is approximately 10 TECU, and the simulated depletion is primarily distributed along the release trajectory, with a horizontal width perpendicular to the trajectory of about 500 km. Figure 4b–d presents a comparison of electron density between the Swarm A, Swarm C, and Swarm B satellites and the simulations. The simulation results show that at the location corresponding to Swarm A, the electron density reduction amplitude is
Comparison of the simulated dTEC calculation at the 40th minute with observational data.
TEC signals of the depletion observed within the REDs at several different time intervals.
The ionospheric piercing points (IPPs) for TEC data derived from ground-based GPS receivers shift over time, providing temporal sequences of REDs observations at different intervals. As shown in Fig. 5, for the IPPs closest to the rocket trajectory (blue line), the TEC begins to drop approximately 10 min after launch – this 10 min delay corresponds to the time required for the rocket to reach the vicinity of this IPPs. The decrease occurs rapidly within 3–5 min, followed by a slower decline. Since this location (blue line) is at the edge of the main REDs, the maximum depletion amplitude observed here is about 10 TECU, which is weaker than the values recorded later by IPPs that pass directly through the depletion (green and pink lines). For IPPs entering the REDs more than 20 min after launch, the TEC variations exhibit smoother curves. The maximum depletion amplitude for this entire event is recorded around 90 min post-launch. Furthermore, as indicated in Fig. 2, most TEC variations observed after 90 min are collectively weaker than the maximum amplitude captured by the green line. This suggests that the REDs subsequently entered a diffusion-driven recovery stage after 90 min, gradually returning to background levels.
The horizontal evolution of REDs in Event-1 is consistent with Event-2 (same rocket type) and prior cases (e.g. Mendillo et al.,2008), where depletions exceeded
Simulations show water vapor rapidly diffuses within 1–2 min, expand more slowly over
Figure 1 shows COSMIC-1 occultation data and rocket data. Previous studies (Park et al., 2015, 2016) reported similar REDs lasting nearly 6 h using DMSP satellite data. For Event-1, GNSS data measured depletions
Swarm A and C, observing along the latter half of the trajectory, detected reductions around 40 %. Time differences between these four datasets were
The observational period of the radio occultation data falls within the first 50 min after the rocket launch. Relative to the RED's total lifetime of nearly 6 h, this observational period places the RED in the early stage of its diffusion recovery phase, a period characterized by a considerable horizontal extent. According to previous studies summarized in Table 3, the horizontal width of the RED ranges from 150 to 520 km, depending on factors such as rocket type and launch trajectory. The RED generated by rockets of the same type performing the same orbital mission exhibit similar widths. Therefore, the REDs produced by Event-1 and Event-2 can be assumed to have comparable widths, approximately 500 km, which is used as the horizontal constraint for the three-dimensional RED structure.
The Characteristics of RED by Rocket Launch Events in previous studies; TSLC is Taiyuan Satellite Launch Center of China (38.5° N, 111.6° E), KSC is Kennedy Space Center of USA (28.5° N, 80.7° W).
Figure 6 illustrates the simulated electron density distribution and the estimated spatial extent of the HIREs constrained by multi-dimensional observational data. The horizontal extent of the HIREs is constrained by GNSS TEC observations, while the vertical scale is jointly constrained by COSMIC and Swarm satellite altitude observations. The boundary of the vertical cross-section of the HIREs derived from numerical simulations is approximately elliptical. Based on the horizontal and vertical constraints, the ellipse-like boundaries are fitted to the COSMIC radio occultation and Swarm satellite observations. Polynomial fitting is then used to connect these boundaries, producing the red dashed tubular volume in Fig. 6, representing the observed HIREs extent. The three-dimensional simulated electron density distribution is displayed in cross-sectional view as six parallel colored panels in Fig. 6. By comparing the simulated HIREs with the fitted observational HIREs, the horizontal distance between the centers of the simulated and observed HIREs does not exceed 120 km, and for the COSMIC-1 C01–G11 occultation event, the distance between the observed and simulated HIREs centers is less than 30 km. The simulated HIREs is about 20 % wider than the observed electron depletion, likely due to discrepancies between the background parameters used in the simulation and the actual ionospheric conditions. Differences between IRI model outputs and real ionospheric TEC can exceed 20 % (He et al., 2023). As the HIREs extends over thousands of kilometers, it is subjected to varying background wind intensities and associated uncertainties at different locations. These variations, in turn, induce differential HIREs drift distances, resulting in positional discrepancies between the simulated HRIEs centerline and the observed 3D centerline.
Simulated electron density distribution at 40 min and the range of HIREs.
Combining simulation and observational results, the three-dimensional structure of the REDs is a “flattened hollow tube” with a wider top. The entire “flattened 3D hollow tube” envelops the launch trajectory, with the trajectory located closer to the lower side of the tube, resulting in an asymmetric vertical distribution of the RED along the trajectory. Simulation results indicate that the width and thickness of the “flattened 3D hollow tube” are primarily controlled by the amount and altitude of exhaust release and the background electron density distribution. The High-density area electron density layer is mainly located around 300 km in the ionospheric
By integrating the simulated vertical electron density, the equivalent vTEC as observed by ground-based GNSS can be obtained. In this study, equivalent observational integrals were also performed along the ray paths of two COSMIC radio occultation events, and the simulation results were compared with electron density measurements from the Swarm satellites, as shown in Fig. 4. The simulated vTEC depletion amplitude and spatial scale are generally consistent with ground-based GNSS observations; the discrepancies between the simulation and Swarm satellite observations primarily arise from the fact that the background electron density output by the IRI model is significantly lower than the observed values. In the chemical process of depletion formation, the recombination efficiency (
This is the first study that utilizes COSMIC-1 occultation data to resolve the vertical structure of REDs, integrates Swarm and GNSS-TEC observations, and reconstructs its 3D hollowtube morphology. Observation-simulation comparisons validate model reliability and support a three-stage RED evolution framework: rapid formation, diffusion-driven growth, and recovery. The main conclusions are as follows: Using COSMIC-1 radio occultation data, we for the first time observed the vertical distribution of REDs at different locations along the rocket trajectory. At a location 700 km from the launch site, the RED vertical extent is 197–300 km, while at another location 2600 km away, the observed vertical extent is 310–400 km. By combining multi-dimensional observational data with three-dimensional numerical simulations, we reconstructed the three-dimensional tubular structure of the RED. Its vertical cross-section is an upper-wide, lower-narrow quasi-elliptical shape, with a vertical-to-horizontal thickness-to-width ratio of approximately Based on observations and simulations, the evolution of rocket-exhausted ionospheric electron density depletion can be divided into three stages: rapid formation, diffusive growth, and diffusive recovery. During the first 3–5 min after exhaust release, the REDs undergoes rapid growth, with the fastest rate of electron density decrease. It then enters a 15–30 min diffusive growth stage, during which the REDs expands to its maximum spatial extent, with a vertical thickness ranging from 100–500 km and a horizontal width along the trajectory of 300–500 km. Finally, the REDs evolves into the diffusive recovery stage, lasting more than 50 min, longer than the preceding two stages. During this stage, the REDs slowly returns to background values while undergoing drift motions at different rates due to the influence of the magnetic field and background wind.
Due to the influence of factors such as local time, propellant characteristics, and orbital insertion, understanding of REDs' 3D evolution remains limited. Broader observational coverage and more diverse cases are needed to identify common patterns and better assess REDs' physical drivers and space weather impacts.
The code developed for this study is openly accessible via the GitHub repository at
The GNSS data used in this study are publicly accessible from the Scripps Orbit and Permanent Array Center (SOPAC) and the California Spatial Reference Center (CSRC) at
The supplement related to this article is available online at
CD conceived the study, performed the data analysis, and wrote the manuscript. XY contributed to the research design, interpretation of the results, and revision of the manuscript. TY and XX contributed to the analysis of the results and partial data processing. QQ contributed to the analysis of the results and partial data processing. All authors contributed to the discussion and approved the final manuscript.
The contact author has declared that none of the authors has any competing interests.
Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this paper. The authors bear the ultimate responsibility for providing appropriate place names. Views expressed in the text are those of the authors and do not necessarily reflect the views of the publisher.
This work is supported by the National Natural Science Foundation of China (NSFC, 42230207, 42574223, 42074191). We gratefully acknowledge the Scripps Orbit and Permanent Array Center (SOPAC) and the California Spatial Reference Center (CSRC) for providing publicly accessible GNSS data (
This research has been supported by the National Natural Science Foundation of China (NSFC, 42230207, 42574223, 42074191).
This paper was edited by John Plane and reviewed by Paul Bernhardt and one anonymous referee.