Ionospheric Plasma Bubbles Research Articles

An Empirical Model of the Occurrence Rate of Low Latitude Post‐Sunset Plasma Irregularities Derived From CHAMP and Swarm Magnetic Observations

AbstractThe prediction of post‐sunset equatorial plasma depletions (EPDs), often called ionospheric plasma bubbles, has remained a challenge for decades. In this study, we introduce the Ionospheric Bubble Probability (IBP) model, an empirical model to predict the occurrence probability of EPDs derived from 9 years of CHAMP and 9 years of Swarm magnetic field measurements. The model predicts the occurrence probability of EPDs for a given longitude, day of year, local time and solar activity, for the altitude range of about 350–510 km, and low geographic latitudes of ±45°. IBP has been found to successfully reconstruct the distribution of EPDs as reported in previous studies from independent data. IBP has been further evaluated using 1‐year of untrained data of the Ionospheric Bubble Index (IBI). IBI is a Level 2 product of the Swarm satellite mission used for EPD identification. The relative operating characteristics (ROC) curve shows positive excursion above the no‐skill line with Hanssen and Kuiper's Discriminant (H&KSS) score of 0.52, 0.51, and 0.55 at threshold model output of 0.16 for Swarm A, B, and C satellites. Additionally, the reliability plots show proximity to the diagonal line with a decent Brier Skill Score (BSS) of 0.249, 0.210, and 0.267 for Swarm A, B, and C respectively at 15% climatological occurrence rate. These tests indicate that the model performs significantly better than a no‐skill forecast. The IBP model offers compelling glimpses into the future of EPD forecasting, thus demonstrating its potential to reliably predict EPD occurrences. The IBP model is publicly available.

Investigation of the Physical Mechanisms of the Formation and Evolution of Equatorial Plasma Bubbles During a Moderate Storm on 17 September 2021

AbstractWe investigate in detail the occurrence and evolution of ionospheric equatorial plasma bubbles (EPBs) during a moderate storm on 17 September 2021, using Global‐scale Observations of the Limb and Disk (GOLD) observations and Whole Atmosphere Community Climate Model‐eXtended (WACCM‐X) simulations. GOLD observations show that there were no EPBs on 16 September before the storm but EPBs occurred after the storm commencement on 17 September. The EPBs extended to ∼30° magnetic latitude. A diagnostic analysis of WACCM‐X simulations reveals that the rapid enhancement of prompt penetration electric fields (PPEFs) after the sudden storm commencement is the main reason that triggered the occurrence of the EPBs. Further quantitative analysis shows that vertical plasma drifts, which are enhanced by the PPEF, played a dominant role in strengthening the Rayleigh‐Taylor instability, leading to the occurrence of the EPBs and the large latitudinal extension of the EPBs to ∼30° magnetic latitude during the night of 17 September.

A Novel Population of Slow Magnetosonic Waves and a Method for the Observation of the Roots of Plasma Bubbles in the Lower Ionosphere

AbstractUsing data from the Van Allen Probe and Swarm‐Bravo satellites, evidence for a persistent population of slow magnetosonic waves in the ionosphere is presented. Dispersion relations from two‐fluid analyses of waves in warm plasma are used to interpret and explicate these observations. These waves appear to be continuously present and globally distributed. Their amplitudes systematically decrease with increasing altitude. The amplitudes are also correlated with longitude in a manner consistent with the global distribution of lightning strikes. Evidence for narrow resonances in the Swarm data consistent with doppler shifted Schumann resonance frequencies is presented. In addition, nearly dispersionless fast magnetosonic waves are sometimes also seen. A new method for the analysis of these waves suggests they show the existence of “foamy” plasma bubble “roots” at the base of the ionosphere.

Peak‐Height Distribution of Equatorial Ionospheric Plasma Bubbles: Analysis and Modeling of C/NOFS Satellite Observations

AbstractWe present the first observational determination of statistical limits on the rise of equatorial plasma bubbles as a function of solar flux. We analyzed in situ electron density data collected onboard the Communications/Navigations Outage Forecasting System (C/NOFS) satellite to characterize the distribution of peak altitudes of equatorial ionospheric plasma bubbles. We first describe our algorithm for detecting ionospheric irregularities within the observations and then use a series of statistical simulations to identify and compensate for the sampling biases inherent in observations from a single satellite in a low‐inclination elliptical orbit. The simulations also confirmed that space‐based orbital platforms such as the C/NOFS satellite undersample the existing irregularities in the ionosphere and provide a measure of the satellite’s inefficiency in observing those naturally occurring irregularities. In deducing the variation of the peak‐height distributions of the irregularities with solar activity, we find that the median maximum height of the bubbles increases linearly from about 490 km at the solar minimum (2008) to 740 km during the (2014) solar maximum in the longitude sector 80°W–10°E. The results will be valuable for the development of improved scintillation mapping models for both real‐time and postprocessing applications. We also confirm our observational findings with modeling results from a physics‐based model, allowing us to identify field‐line‐integrated Pedersen conductance as the key determinant of terminal bubble altitude: a bubble will cease to rise further when the conductance inside the bubble is equal to that of the background ionosphere.

Lessons Learned from IDEASSat: Design, Testing, on Orbit Operations, and Anomaly Analysis of a First University CubeSat Intended for Ionospheric Science

Given the pervasive use of satellite and over the horizon wireless communication technology in modern society, ionospheric disturbances that can disrupt such services are a crucial consideration. Ionospheric irregularities, plasma bubbles and other phenomena can have a great impact on satellite navigation and communications, impacting other systems reliant on such technologies. The Ionospheric Dynamics and Attitude Subsystem Satellite (IDEASSat) was a 3U developed by National Central University (NCU) to measure irregularities in the ionosphere, as well as to establish spacecraft engineering and operations capacity at NCU. The onboard Compact Ionospheric Probe (CIP) could measure high-resolution plasma parameters, which can be used for identifying ionospheric irregularities that can cause scintillation in satellite navigation and communications signals. Part of the spacecraft sub-systems were independently designed and developed by students, who were also responsible for integration, testing, and operations. IDEASSat was successfully launched into low Earth orbit on 24 January 2021, and then began mission operations. The spacecraft successfully demonstrated three-axis attitude stabilization and control, tracking, telemetry and command (TT&C), as well as flight software and ground systems that could support autonomous operation. The spacecraft experienced a critical anomaly 22 days after launch, followed by a 1.5-month communications blackout. The spacecraft briefly recovered from the blackout for long enough to replay flight data, which allowed for the cause of the blackout to be determined as an inability of the electrical power subsystem reset circuit to recover from an ionizing radiation induced single event latch-up. Although the mission was not completed, flight data obtained during the mission will help to improve the designs of future spacecraft in development at NCU. This paper will introduce IDEASSat’s final flight model design and implementation, integration, testing, environmental verification, and failure analysis, and will review the performance of the spacecraft during on-orbit operations. The results and experiences encountered in implementation and operations of the IDEASSat mission are presented here as a reference for other university small satellite teams.

Vertical characterization on global ionospheric variations during the magnetic storm in September 2017 with hierarchical subtraction method

This study investigates the global ionospheric responses at different altitudes during the geomagnetic storm in September 2017 by using the observations from IGS GIMs and GRACE, TerraSAR-X, COSMIC, Metop LEO satellite missions. According to different satellite heights, a hierarchical subtraction method is proposed to characterize the disturbance of total electron content (TEC) at the vertical regions of below 340 km , 340 ∼ 520 km , 520 ∼ 800 km and above 800 km , respectively. The integrated TEC from IRI-Plas2017 are applied to verify the feasibility and rationality of the proposed method and the electron density (Ne) profiles from the ionosonde and radio occultation (RO) measurements are used to explore the variations of Ne in different height regions. The resulting TEC disturbances ( Δ TEC) on a global scale show that: 1) There was significant increase on Ne peak in F2 region during the magnetic storm, due to the strong recombination in the lower ionosphere while more intense electron ionization in the upper ionosphere; 2) During the main phase, TEC enhancement had a tendency to drift westward, which may correlate with the twice Dst minimums. 3) The east–west and north–south hemispheric asymmetry of Δ TEC exist simultaneously in this magnetic storm. However, the former is mainly attributed to ionospheric plasma bubbles, while the latter might be the seasonal thermospheric effects or the energetic particle emissions.

Unseasonal super ionospheric plasma bubble and scintillations seeded by the 2022 Tonga Volcano Eruption related perturbations

The Hunga–Tonga volcano eruption at 04:14:45 UT on 15 January 2022 produced various waves propagating globally, disturbing the background atmosphere and ionosphere. Coinciding with the arrival of perturbation waves, several equatorial plasma bubbles (EPBs) were consecutively generated at post-sunset hours over the East/Southeast Asian region, with the largest extension to middle latitudes. These EPBs caused intenseL-band amplitude scintillations at middle-to-low latitudes, with signal fading depths up to ~16 dB. Considering the very rare occurrence of EPBs during this season in the East/Southeast Asian sector and the significantly modulated background ionosphere, we believe that the perturbation waves launched by the volcano eruption triggered the generation of the unseasonal super EPBs. The ionospheric perturbations linked with the 2022 Tonga volcano eruption propagated coincidently through the East/Southeast Asia longitude sector near sunset, modulated the equatorial F region bottomside plasma density, and acted as the seeding source for the generation of the unseasonal super bubbles. Our results implicate that volcano eruption could indirectly affect the satellite communication links in the region more than ten thousand kilometers away.

Local ionospheric plasma bubble revealed by BDS Geostationary Earth Orbit satellite observations

Local ionospheric plasma bubble revealed by BDS Geostationary Earth Orbit satellite observations

COSMIC observation of stratospheric gravity wave and ionospheric scintillation correlation

A correlation study is performed to investigate possible connections between the stratospheric gravity waves and the ionospheric plasma bubble induced GPS signal scintillations. Using the COSMIC 1 neutral temperature data (10–30 km), we extract gravity wave amplitudes with vertical wavelengths from 2.5 to 10 km within the latitudinal range from 37.5S to 37.5N. We then calculated the occurrence of high GPS L1 amplitude scintillation (S4 > 0.2) in the equatorial region (25S and 25N). The high S4 values showed consistent higher correlations with gravity waves at the equator than those away from the equator for all vertical wavelengths between 2010 and 2013. While the peak correlation is only ~0.2, the consistency over different wavelengths and years suggests a possible link, which could be through seeding of plasma bubbles and/or modulation of the neutral wind dynamo by gravity waves. We see the need for further study based on statistics of simultaneous observations of gravity waves, ionospheric scintillations, and other ionospheric and thermospheric parameters, which can lead to a better understanding of the plasma bubble formation mechanism.

Ionospheric Turbulence and the Equatorial Plasma Density Irregularities: Scaling Features and RODI

In the framework of space weather, the understanding of the physical mechanisms responsible for the generation of ionospheric irregularities is particularly relevant for their effects on global positioning and communication systems. Ionospheric equatorial plasma bubbles are one of the possible irregularities. In this work, using data from the ESA Swarm mission, we investigate the scaling features of electron density fluctuations characterizing equatorial plasma bubbles. Results strongly support a turbulence character of these structures and suggest the existence of a clear link between the observed scaling properties and the value of the Rate Of change of electron Density Index (RODI). This link is discussed, and RODI is proposed as a reliable proxy for the identification of plasma bubbles.

Ground and satellite-based observations of ionospheric plasma bubbles and blobs at 5.65° latitude in the Brazilian sector

This investigation uses simultaneous observations from all-sky imager system and an ionosonde collocated at Araguatins (5.65° S, 48.07° W and dip-latitude of 4.17° S), a near-equatorial region in Brazil. These simultaneous observations were used to investigate the occurrence of plasma bubbles and blobs in the field of the imaging system and their association with atypical range Spread-F signature in ionograms. Also, in-situ observation of plasma density from Swarm satellites were used to support the ground-based observations. Using a few cases, a methodology will be established to identify in the plasma blobs (atypical ESF) in the ionograms when there is the simultaneous observation of plasma bubbles and blobs in the field of view of the ionosonde. For this purpose, simultaneous sequence of OI 630.0 nm nightglow images and ionograms are presented for different case studies; 1. when there is the absence of a plasma bubble or blob, 2. when there is only the occurrence of plasma bubbles and 3. when there is the occurrence of plasma bubbles and blobs, in order to compare traces in the ionogram in all these case studies. With these we can cover all kinds of signatures in the ionograms corresponding to no irregularities, plasma bubbles only and plasma bubbles-blobs. These OI 630.0 nm nightglow and ionograms recorded simultaneously make it possible to establish a novel methodology to recognize in ionograms cases when there is the occurrence of Spread-F signature associated with bubble-blob in the FOV of the ionosonde.

Forcing From Lower Thermosphere and Quiet Time Scintillation Longitudinal Dependence

AbstractThe quiet time ionospheric plasma bubbles that occur almost every day become a significant threat for radio frequency (RF) signal degradation that affects communication and navigation systems. We have analyzed multi‐instrument observations to determine the driving mechanism for quiet time bubbles and to answer the longstanding problem, what controls the longitudinal and seasonal dependence of ionospheric irregularity occurrence rate? While VHF scintillation and GNSS ROTI are used to characterize irregularity occurrence, the vertical drifts from JRO and IVM onboard C/NOFS, as well as gravity waves (GWs) amplitudes, extracted SABER temperature profiles, are utilized to identify the potential driving mechanism for the generation of small‐scale plasma density irregularities. We demonstrated that the postsunset vertical drift enhancement may not always be a requirement for the generation of equatorial plasma bubbles. The tropospheric GWs with a vertical wavelength (4 km < λv < 30 km) can also penetrate to higher altitudes and provide enough seeding to the bottom side ionosphere and elicit density irregularity. This paper, using a one‐to‐one comparison between GWs amplitudes and irregularity occurrence distributions, also demonstrated that the GWs seeding plays a critical role in modulating the longitudinal dependence of equatorial density irregularities. Thus, it is becoming increasingly clear that understanding the forcing from a lower thermosphere is critically essential for the modeling community to predict and forecast the day‐to‐day and longitudinal variabilities of ionospheric irregularities and scintillations.

Global Modeling of Equatorial Spread F with SAMI3/WACCM‐X

AbstractWe report the first results of a global ionosphere/thermosphere simulation study that self‐consistently generates large‐scale equatorial spread F (ESF) plasma bubbles in the postsunset ionosphere. The coupled model comprises the ionospheric code SAMI3 and the atmosphere/thermosphere code WACCM‐X. Two cases are modeled for different seasons and geophysical conditions: the March case (low solar activity: F10.7 = 70) and the July case (high solar activity: F10.7 = 170). We find that equatorial plasma bubbles formed and penetrated into the topside F layer for the March case but not the July case. For the March case, a series of bubbles formed in the Atlantic sector with irregularity spacings in the range 400–1,200 km, rose to over 800 km, and persisted until after midnight. These results are consistent with recent GOLD observations. Calculation of the generalized Rayleigh‐Taylor instability (GRTI) growth rate shows that the e‐folding time was shorter for the March case than the July case.

Investigation of the latitudinal occurrence rate of ionospheric plasma bubble in case of strong and weak pre–reversal enhancement in Southeast Asia

We used ionosonde and GPS receivers during March–April in 2004–2005 and 2011–2015 to investigate the latitudinal variation of equatorial plasma bubble (EPB) occurrence rate in cases of strong and weak pre-reversal enhancement (PRE). The ionosonde at Chumphon in Thailand was used to estimate the PRE strength. Ten GPS receivers in Southeast Asia, ranging from magnetic latitude (ML) of 4.4°S to 21.6°S, were used to investigate the latitudinal variation of EPB occurrence rate. In the case of strong PRE, the EPB occurrence rates decrease from 38.9% to 34.9% at ML of 4.4°S–7.2°S. Continuously, the occurrence rate increases and reaches the peak (44%) at ML of 9.3°S; afterward, the occurrence rate rapidly decreases and reaches below 5% at ML of 21.6°S. In the case of weak PRE, the occurrence rate decreases from 21.8% at ML of 4.4°S, seems constant (15.3%–16%) at ML of 8.2°S–12.1°S, and reaches less than 5% at ML of 16.1°S. Generally, the EPB occurrence rate and its latitudinal extension in case of strong PRE are higher than that in case of weak PRE. Interestingly, we found that the latitudinal occurrence rate peak of the EPB in case of strong is farther than that in case of weak PRE.

Optical observation of plasma bubbles and comparative study of multiple methods of observing the ionosphere over China

Ionospheric plasma bubbles and scintillation phenomena often occur at low latitudes in China. The all-sky airglow imager located at Fuke station in Hainan (19.5°N, 109.2°E) is part of the Meridian project in China. In this work, we used mainly the observation data obtained by the imager and a digisonde to study plasma bubbles. Optical image processing—including image enhancement, azimuth correction and image projection—was performed on the original airglow observation images, and clear high-resolution images of the bubbles were obtained. Based on these, the morphological features, spatial and temporal variations, spatial scale, drift velocity of the plasma bubbles in the F region of the ionosphere were investigated and analyzed. The plasma bubbles appeared as long, dark stripes on the bright airglow emission background. Their large-scale structures often bifurcated vertically, and were usually tilted westward with north-south extension along the magnetic field lines. The east-west scale of the plasma bubbles was usually greater than 200 km and these increased gradually with time. Moreover, the distance between the adjacent plasma bubbles also increased over time, and was in the 100–400 km range. Plasma bubbles generally drifted eastward with an average drift velocity of approximately 90 m/s. The occurrence and duration of the plasma bubbles were compared with digisonde observations, and it was shown that plasma bubbles lasted for nearly four hours. Additionally, the main characteristics of the plasma bubbles were obtained using both optical and radio observations and the study of which can be beneficial for monitoring and predicting ionospheric scintillations.

Satellite Formation Flight Simulation Using Multi-Constellation GNSS and Applications to Ionospheric Remote Sensing

The Virginia Tech Formation Flying Testbed (VTFFTB) is a global navigation satellite system (GNSS)-based hardware-in-the-loop (HIL) simulation testbed for spacecraft formation flying with ionospheric remote sensing applications. Past applications considered only the Global Positioning System (GPS) constellation. The rapid GNSS modernization offers more signals from other constellations, including the growing European system—Galileo. This study presents an upgrade of VTFFTB with the incorporation of Galileo and the associated enhanced capabilities. By simulating an ionospheric plasma bubble scenario with a pair of LEO satellites flying in formation, the GPS-based simulations are compared to multi-constellation GNSS simulations including the Galileo constellation. A comparison between multi-constellation (GPS and Galileo) and single-constellation (GPS) shows the absolute mean and standard deviation of vertical electron density measurement errors for a specific Equatorial Spread F (ESF) scenario are decreased by 32.83% and 46.12% with the additional Galileo constellation using the 13 July 2018 almanac. Another comparison based on a simulation using the 8 March 2019 almanac shows the mean and standard deviation of vertical electron density measurement errors were decreased further to 43.34% and 49.92% by combining both GPS and Galileo data. A sensitivity study shows that the Galileo electron density measurements are correlated with the vertical separation of the formation configuration. Lower C/N 0 level increases the measurement errors and scattering level of vertical electron density retrieval. Relative state estimation errors are decreased, as well by utilizing GPS L1 plus Galileo E1 carrier phase instead of GPS L1 only. Overall, superior performance on both remote sensing and relative navigation applications is observed by adding Galileo to the VTFFTB.

Ionospheric Plasma Bubble Zonal Drift Derived From Total Electron Content Measurements

AbstractEquatorial plasma bubbles consist of field‐aligned large‐scale depletions, or irregularities, characterized by drastic ion density rarefactions of the nocturnal low latitude/equatorial ionosphere. Understanding their behavior is important because of their degrading effects on radio wave signals and, consequently, their respective technological applications such as, for example, Global Positioning System applications. In this sense, a methodology of pattern recognition was developed and implemented here using the Long‐Term Ionospheric Anomaly Monitoring in order to infer the plasma bubbles zonal drift velocities, using two receiving stations of global navigation satellite systems data from the Brazilian Continuous Monitoring Network, located near to each other, in Salvador (BA) during geomagnetically quiet periods. The study covered the years of 2012, 2013, and 2014 for the months from September to January of the following year, choosing 10 representative days for each month. The average results for the plasma bubble zonal velocities provided by the model calculations were in agreement with the well‐known values. However, monthly individual analysis showed a behavior anticorrelated with that expected for high solar flux. Probably, the unexpected behavior is due to atypical configuration of the solar activity ascending phase.

The possibility of estimating the height of the ionospheric inhomogeneities based on TEC variations maps obtained from dense GPS network

A state of the ionosphere can be effectively studied using electromagnetic signals received from global navigation satellite systems (GNSS). Utilization of the dual frequency observations allows estimating values of the total electron content (TEC). They can be used for a number of scientific studies such as detection and monitoring of traveling ionospheric disturbances or plasma bubbles. Moreover, maps of TEC variations allow to classify ionospheric heterogeneities and to evaluate their parameters. However, most of the research describes ionospheric parameters only in 2D space and time. In this paper, we focus on the determination of the height of the ionospheric inhomogeneities. We used a dense network of GPS receivers to obtain the sequences of TEC variation maps for different heights of the ionospheric layer. For each satellite observed above 70°, we constructed separate sets of maps. For each ionospheric height, the cross-correlation function between maps corresponding to different satellites was calculated. The biggest cross-correlation coefficient value determines the height of the ionospheric irregularities. This paper describes the methodology and the results obtained for a geomagnetic storm on St. Patrick’s Day in March 2013. We have found that in quiet geomagnetic conditions the ionospheric irregularities are localized predominantly within the interval 180–220 km close to the maximum of the ionospheric F2 layer. In disturbed conditions, the height of their localization was increased up to several hundreds of kilometers. These estimations correspond to the changes in the slab thickness of the ionosphere.

Multi‐Instrumental Observation of Storm‐Induced Ionospheric Plasma Bubbles at Equatorial and Middle Latitudes

AbstractJune solstice is considered as a period with the lowest probability to observe typical equatorial plasma bubbles (EPBs) in the postsunset period. The severe geomagnetic storm on 22–23 June 2015 has drastically changed the situation. Penetrating electric fields associated with a long‐lasting southward IMF support favorable conditions for postsunset EPBs generation in the dusk equatorial ionosphere for several hours. As a result, the storm‐induced EPBs were progressively developed over a great longitudinal range following the sunset terminator. The affected area has a large longitudinal range of ~100° in the American sector and a rather localized zone of ~20° in longitude in the African sector. Plasma depletions of equatorial origin were registered at midlatitudes (30°–40° magnetic latitude) of both hemispheres in the African and American longitudinal sectors. We examine global features of the large‐scale plasma depletion by using a combination of ground‐based and space‐borne measurements—ground‐based Global Positioning System/Global Navigation Satellite System (GPS/GNSS) networks, Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) GPS Radio Occultation (RO), Swarm upward looking GPS data, and in situ plasma density observations provided by Swarm, Communications/Navigation Outage Forecasting System (C/NOFS), and Defense Meteorological Satellite Program (DMSP) missions. Joint analysis of the satellite observations revealed that these storm‐induced EPBs structures had extended over 500 km in altitude, at least from ~350 to ~850 km. These irregularities caused strong amplitude and phase scintillations of GPS/GNSS signals for ground‐based and space‐borne (COSMIC RO) measurements and seriously affected performance of navigation‐based services.

The Effect of Plasma Releases on Equatorial Spread F—a Simulation Study

A currently unfulfilled goal of active experimentalists is to control the occurrence of instabilities in the ionosphere such as Equatorial Spread F (ESF), which generates large-scale electron density depletions (plasma bubbles) in the night-time ionosphere at low latitudes. It has been theorized that by artificially injecting ionizing chemicals (such as barium) into the ionosphere, ESF may be suppressed. Large plasma releases modify the ionospheric conductance, which affects the electrodynamics of the system and may thereby influence the growth (or suppression) of ESF. In this study, the feasibility of controlling ESF growth via plasma releases in the ionosphere is examined for the first time using a fully three-dimensional, first-principles model of the ionosphere: SAMI3/ESF (Sami is Another Model of the Ionosphere). The numerical simulations show that under certain circumstances plasma injections may be able to trigger or suppress ESF growth. The results indicate that the plasma density must be above a threshold level to sufficiently modify the ionospheric conductance. In addition, the plasma must be injected at a suitable location and time. The results of this numerical investigation provide guidance for future experimental campaigns.