Atmosphere-ionosphere System Research Articles

Electromagnetic ULF Fields from an Underground Seismic Source on the Earth’s Surface and in the Ionosphere

A theoretical formalism has been developed to calculate the electromagnetic fields generated in the atmosphere–ionosphere system by a finitelength underground horizontal current source. A numerical model with a realistic profile of the ionosphere in a vertical geomagnetic field has been designed based on this theory. It is shown that the apparent impedance of the electromagnetic field created by an underground source on the Earth’s surface is one order of magnitude higher than the Earth’s impedance, which can be used to discriminate perturbations from seismogenic sources. The presented results of numerical modeling allow us to relate perturbations created by a large-scale underground source in the Earth surface magnetic field and in the electric field in the ionosphere. Based on these model estimates it is concluded that many of the ULF electric field perturbations detected in satellite data before earthquakes cannot be attributed to direct emission from seismogenic sources.

Responses to the Preparation of the 2021 M7.4 Madoi Earthquake in the Lithosphere–Atmosphere–Ionosphere System

The purpose of this work is to investigate the responses of multiple parameters to the Madoi earthquake preparation. A new method is employed to extract anomalies in a geomagnetic field. The results show that there were abnormal changes in the lithosphere, atmosphere, and ionosphere near the epicenter before the earthquake. Despite the differences in spatial and temporal resolutions, the increase in geomagnetic residuals in the lithosphere exhibits similar temporal characteristics to the enhancement of thermal infrared radiation in the atmosphere. Two high–value regions are present in the ground–based geomagnetic high residuals and the ionospheric disturbances. The northern one is around the epicenter of the Madoi earthquake. Near the southern one, an M6.4 Yangbi earthquake occurred four hours before the Madoi earthquake. In this study, we have observed almost all of the physical phenomena that can occur during the preparation of an earthquake, as predicted using the electrostatic channel model. It can be inferred that the electrostatic channel is a possible mechanism for coupling between the lithosphere, atmosphere, and ionosphere during the Madoi earthquake.

Multi-altitude observations of the lower atmospheric disturbances and its ionospheric signatures over the Indian region

Tropospheric disturbances like tropical cyclones produce a spectrum of gravity waves which can propagate to higher altitudes and can even perturb the ionosphere-thermosphere system. The observations of a severe cyclonic storm Hudhud during 7–14 October 2014 using vertical total electron content (VTEC) from 11 stations and the brightness temperature from AIRS (atmospheric infrared sounder) imagery are analysed. Main results show ring-arc structures resembling concentric gravity waves (CGWs) in the brightness temperature and widespread, synchronized and episodic perturbations in VTEC during 10, 11 and 12 October. The stratospheric perturbations are found to spread in a range of radial distance between ∼ 730 and 2500 km with horizontal wavelengths between 307 and 541 km. A wavelet analysis of the daytime band-pass (5–60 min) filtered dVTEC perturbations shows enhancements in the spectral power associated with periods of ∼ 30–50 min on different days following the cyclone movement from east to west. The radial phase speed of the dVTEC for different temporal bands is found to vary between 114 and 320 m/s at different intervals during 10–11 October. Additionally, a comparative analysis of the past and present results is performed using the established dispersion relations which shows a compatible range of variability of wave parameters among all the studies including the present results. The results substantiate strong signatures of the Hudhud cyclone at multiple altitudes and depict vertical coupling of the atmosphere–ionosphere system through a theoretical framework.

Improving ionospheric predictability requires accurate simulation of the mesospheric polar vortex

The mesospheric polar vortex (MPV) plays a critical role in coupling the atmosphere-ionosphere system, so its accurate simulation is imperative for robust predictions of the thermosphere and ionosphere. While the stratospheric polar vortex is widely understood and characterized, the mesospheric polar vortex is much less well-known and observed, a short-coming that must be addressed to improve predictability of the ionosphere. The winter MPV facilitates top-down coupling via the communication of high energy particle precipitation effects from the thermosphere down to the stratosphere, though the details of this mechanism are poorly understood. Coupling from the bottom-up involves gravity waves (GWs), planetary waves (PWs), and tidal interactions that are distinctly different and important during weak vs. strong vortex states, and yet remain poorly understood as well. Moreover, generation and modulation of GWs by the large wind shears at the vortex edge contribute to the generation of traveling atmospheric disturbances and traveling ionospheric disturbances. Unfortunately, representation of the MPV is generally not accurate in state-of-the-art general circulation models, even when compared to the limited observational data available. Models substantially underestimate eastward momentum at the top of the MPV, which limits the ability to predict upward effects in the thermosphere. The zonal wind bias responsible for this missing momentum in models has been attributed to deficiencies in the treatment of GWs and to an inaccurate representation of the high-latitude dynamics. In the coming decade, simulations of the MPV must be improved.

Investigation of gravity wave characteristics in the equatorial ionosphere during the passage of the 15 January 2010 solar eclipse over Tirunelveli

Solar eclipses are known to produce gravity wave disturbances in the atmosphere–ionosphere system in addition to density reduction due to temporary changes in solar radiation. The magnetic equator is ideally located to investigate these waves and their coupling to the equatorial ionosphere due to its unique geometry. Accordingly, the response of the equatorial ionosphere to a rare Annular Solar Eclipse (ASE) observed on 15 January 2010 is investigated using high-resolution observations from Canadian Advanced Digital Ionosonde (CADI) located at Tirunelveli which is a magnetic equator and on the eclipse totality path in India. In addition, simultaneous observations of GPS TEC from Tirunelveli, electron density profiles from Constellation Observing System for Meteorology Ionosphere and Climate (COSMIC), and Equatorial Electrojet (EEJ) strength were analysed. The real height analysis has been performed on the ionosonde data using POLynomial ANalysis (POLAN). The isoheight/isofrequency analysis has been performed using real height on eclipse and control days. The results indicate a reduction of ∼33% in the lower ionosphere whereas no change has been noticed close to the F layer peak on the eclipse day. The isoheight analysis further indicates the presence of gravity waves with dominant periods in the range of 5–30 min. Further analyses have been performed on the altitude variation of dominant waves and their amplitudes/phases using ionosonde to identify whether they are generated in situ or propagated from below. The altitude variation of group and phase velocities showed opposite propagation indicating that they were propagated from the below. In addition, the simultaneous presence of gravity waves in the fmin, TEC, and EEJ strength on eclipse day supports our finding that these waves were propagated from the lower atmosphere.

Observations of Pole-to-Pole, Stratosphere-to-Ionosphere Connection

The behavior of the Earth’s middle atmosphere and ionosphere is governed by multiple processes resulting not only from downward energy transfer from the Sun and magnetosphere but also upward energy transfer from terrestrial weather. Understanding the relative importance of mechanisms beyond solar and geomagnetic activity is essential for progress in multi-day predictions of the Earth’s atmosphere-ionosphere system. The recent development of research infrastructure, particularly in Antarctica, allows the observation of new ionospheric features. Here we show for the first time that large disturbances observed in the Arctic winter polar stratosphere (20–50 km above ground and at 60–90°N) during a sudden stratospheric warming event are communicated across the globe and cause large disturbances in the summertime ionospheric plasma over Antarctica (60–90°S). Ionospheric anomalies reach ∼100% of the background level and are observed for multiple days. We suggest several possible terrestrial mechanisms that could contribute to the formation of upper atmospheric and ionospheric anomalies in the southern hemisphere.

Design of Multifunctional Mesosphere-Ionosphere Sounding System and Preliminary Results.

This paper describes a novel sounding system for which the functions of the medium frequency (MF) radar and the ionosonde are integrated on the same hardware platform and antenna structure, namely the middle atmosphere-ionosphere (MAI) system. Unlike the common MF radar, MAI system adopts the pseudo-random (PRN) phase-coded modulation technology, which breaks the limitation of the traditional monopulse mode. Through the pulse compression, only a small peak power is needed to achieve the signal-to-noise ratio (SNR) requirement. The excellent anti-jamming performance is also very suitable for the ionospheric sounding. One transmitting and six receiving modes are adopted for the MF sounding. While neglecting the structure of the T/R switches, the coupling interference between the transmitter and the receiver may also be avoided. Moreover, by employing a miniaturized antenna array composed of progressive-wave antennas for the MF receiving and ionospheric sounding, the MAI system takes account of the requirements of the inversion algorithms of MF radar and the large bandwidth need for the ionospheric sounding concurrently. Such an antenna structure can also greatly simplify the system structure and minimize the difficulty of deployment. The experiments verified the availability of the system scheme and its engineering application significance. Through further analysis of the sounding data, the wind field of the mesosphere, the electron density of D layer and electron density profile from layers E to F were obtained at the identical location. The capability of MAI system can play an important role in studying the interaction and coupling mechanism between the mesosphere and ionosphere.

Responses to the preparation of strong Kamchatka earth-quakes in the lithosphere–atmosphere–ionosphere system, based on new data from integrated ground and iono-spheric monitoring

The experience of short-term forecasting of Kamchatka earthquakes based on complex well measurements at the Petropavlovsk-Kamchatsky geody-namic polygon (PGP) shows that, as a rule, the preparation of strong Kamchatka earthquakes is fairly reliable in the medium-term time scale (months or years be-fore the earthquake). However the determination of the stage beginning imme-diately preceding an earthquake (weeks or days before the main event) is a very difficult task. At present time, the solution of this problem is largely associated with the involvement in the preparation of forecast conclusions of data from continuous monitoring of the ionosphere, carried out by ground-based means of vertical radiosonding and measurements of total electronic content (TEC) using the global navigation satellite system GLONASS and GPS. This is due to the fact that significant changes in a number of ionospheric parameters occur mainly 1-5 days before the Kamchatka earthquakes. The results of the compar-ison of the data of daily monitoring of the ionosphere, including information on TEC, with the data integrated downhole measurements showed a rather high correlation of occurrence of anomalies in the ionosphere before strong earth-quakes with changes in the complex parameters in borehole measurements. As one example, the report presents the results of ionospheric and borehole monitoring obtained in the time neighborhood of the strong (MW= 7.5) the earth-quake that occurred on March 25, 2020 in the area of the Northern Kurils. The results show a high correlation between changes in the specific electrical resis-tivity of the Geospace in the area of the PGP with variations in the TEC and the formation of a number of other anomalies in the ionosphere a few days be-fore the earthquake. These results indicate that it is possible to determine fairly reliably the beginning of the final stage of preparation for a strong earthquake. Currently, methods based on atmospheric parameters monitoring are used quite successfully for predictive estimates of the epicenter and magnitude of an earth-quake: the method of chemical potential corrections for measurements at an altitude of ∼ 100 m, as well as data from measurements of outgoing long-wave infrared radiation (OLR) at the level of the upper edge of clouds (heights of 10 -15 km).

Periodicity Variation of Solar Activity and Cosmic Rays During Solar Cycles 22 – 24

The solar radio flux at 2800 MHz (F10.7) and the sunspot number (SSN) are excellent indicators of solar activity. Data from 1986 to 2016 have been used to investigate long-term and mid-term periodicities of the F10.7 solar radio flux, the sunspot number, and galactic cosmic rays (GCRs) intensity, mainly from Oulu and Moscow, using fast Fourier Transform and Morlet wavelet techniques. The ≈ 148 days period, among other periods, is the one seen prominently in SSN, F10.7, and GCRs throughout Solar Cycles 22 to 24. This period could be the third harmonic of ≈ 1.24 years, i.e. ≈ 444 days period. The period of ≈ 1.24 years, found in SSN, F10.7 flux, and GCRs, is ascribed to the rotation of the convective envelope within the Sun during these cycles. Another period found significantly present in F10.7, SSN, and GCRs, is the Quasi-Biennial Oscillation (QBO), with a period of ≈ 1.94 years. The QBO amplitudes are found to vary significantly from one solar cycle to the other, with a minimum during Solar Cycle 24. The decreasing QBO amplitudes during Solar Cycle 24 in all three datasets are well correlated with the QBOs found in the Earth’s atmosphere-ionosphere system reported elsewhere.

Transmission of electric fields due to distributed cloud charges in the atmosphere-ionosphere system

The transmission of electric fields in the lower atmosphere by thunder clouds with a suitable charge distribution profile has been modeled. The electromagnetic responses of the atmosphere are presented through Maxwell’s equations together with a time-varying source charge distribution. The conductivities are taken to be exponentially graded function of altitude. The radial and vertical electric field components are derived for isotropic, anisotropic and thundercloud regions. The analytical solutions for the total Maxwell’s current which flows from the cloud into the ionosphere under DC and quasi-static conditions are obtained for isotropic region. We found that the effect of charge distribution in thunderclouds produced by lightning discharges diminishes rapidly with increasing altitudes. Also, it is found that time to reach Maxwell’s currents a maximum is higher for higher altitudes.

Ground-based acoustic parametric generator impact on the atmosphere and ionosphere in an active experiment

Abstract. We develop theoretical basics of active experiments with two beams of acoustic waves, radiated by a ground-based sound generator. These beams are transformed into atmospheric acoustic gravity waves (AGWs), which have parameters that enable them to penetrate to the altitudes of the ionospheric E and F regions where they influence the electron concentration of the ionosphere. Acoustic waves are generated by the ground-based parametric sound generator (PSG) at the two close frequencies. The main idea of the experiment is to design the output parameters of the PSG to build a cascade scheme of nonlinear wave frequency downshift transformations to provide the necessary conditions for their vertical propagation and to enable penetration to ionospheric altitudes. The PSG generates sound waves (SWs) with frequencies f1 = 600 and f2 = 625 Hz and large amplitudes (100–420 m s−1). Each of these waves is modulated with the frequency of 0.016 Hz. The novelty of the proposed analytical–numerical model is due to simultaneous accounting for nonlinearity, diffraction, losses, and dispersion and inclusion of the two-stage transformation (1) of the initial acoustic waves to the acoustic wave with the difference frequency Δf = f2 − f1 in the altitude ranges 0–0.1 km, in the strongly nonlinear regime, and (2) of the acoustic wave with the difference frequency to atmospheric acoustic gravity waves with the modulational frequency in the altitude ranges 0.1–20 km, which then reach the altitudes of the ionospheric E and F regions, in a practically linear regime. AGWs, nonlinearly transformed from the sound waves, launched by the two-frequency ground-based sound generator can increase the transparency of the ionosphere for the electromagnetic waves in HF (MHz) and VLF (kHz) ranges. The developed theoretical model can be used for interpreting an active experiment that includes the PSG impact on the atmosphere–ionosphere system, measurements of electromagnetic and acoustic fields, study of the variations in ionospheric transparency for the radio emissions from galactic radio sources, optical measurements, and the impact on atmospheric aerosols. The proposed approach can be useful for better understanding the mechanism of the acoustic channel of seismo-ionospheric coupling.

A review of vertical coupling in the Atmosphere–Ionosphere system: Effects of waves, sudden stratospheric warmings, space weather, and of solar activity

This brief introductory review of some recent developments in atmosphere–ionosphere science is written for the “Vertical Coupling Special Issue” that is motivated by the 5th IAGA/ICMA/SCOSTEP Workshop on Vertical Coupling in the Atmosphere–Ionosphere System. Basic processes of vertical coupling in the atmosphere–ionosphere system are discussed, focusing on the effects of internal waves, such as gravity waves and solar tides, sudden stratospheric warmings (SSWs), and of solar activity on the structure of the atmosphere. Internal waves play a crucial role in the current state and evolution of the upper atmosphere–ionosphere system. SSW effects extend into the upper atmosphere, producing changes in the thermospheric circulation and ionospheric disturbances. Sun, the dominant energy source for the atmosphere, directly impacts the upper atmosphere and modulates wave-induced coupling. The emphasis is laid on the most recent developments in the field, while giving credits to older works where necessary. Various international activities in atmospheric vertical coupling, such as SCOSTEP's ROSMIC project, and a brief contextual discussion of the papers published in the special issue are presented.

Electrodynamic model of atmospheric and ionospheric processes on the eve of an earthquake

Electric field generation and its accompanying phenomena in the atmosphere–ionosphere system have been intensively studied in recent years. This paper considers the results of these studies, which have served as the physical basis for the model of lithosphere–ionosphere coupling. According to our model, the intensive processes in the lower atmosphere and lithosphere have an electrodynamic effect on the ionospheric plasma. The model was used to conduct theoretical studies of plasma and electromagnetic effects accompanying the generation of conduction current in the global circuit. It has been shown that the electrodynamic model of the influence of seismic and meteorological processes on cosmic plasma can serve as a physical basis for a satellite system to monitor earthquake precursors and the catastrophic phase of typhoon development. The model makes it possible to couple the satellite data of electromagnetic and plasma measurements with electrophysical and meteorological characteristics of the lower atmosphere at the stage of earthquake preparation and typhoon initiation. The model suggests that the numerous effects in the cosmic plasma have a single source: a change in the conduction current flowing in the atmosphere–ionosphere circuit.

Introduction to the special section on Sun‐Earth system response to extreme solar and seismic events

Introduction to the special section on Sun‐Earth system response to extreme solar and seismic events

Preface to the Special Issue on Thunderstorm Effects in the Atmosphere–Ionosphere System

The first summer school of the “Thunderstorm Effects in the Atmosphere–Ionosphere System” (TEA–IS) funded by the European Science Foundation through its Research Network Programme took place in Torremolinos (Spain) on June 17–22, 2012. The meeting gathered almost 100 scientists with different backgrounds (plasma physics, electrical and signal engineering, geophysics, space physics and computational science) coming from 20 countries, both from inside and outside TEA–IS member countries. We very briefly comment here on the five review papers included in this Special Issue of Surveys in Geophysics devoted to the 2012 TEA–IS summer school.

Oscillations detected near the lower boundary of the Venus ionosphere from the radio occultation measurements of the Venera-15 and Venera-16 satellites

The possibility of detecting wave processes in the atmosphere-ionosphere system of the planet from perturbations of radio signals in radio occultation experiments is studied. A method of interpretation of the radio-raying data that does not employ integral transforms and is well-adapted to problems of detecting refractive index oscillations observed during sensing of the stratified gas envelope of the planet is presented. Periodic oscillations of the radio signal power that are linearly related with the rate of variation in the frequency of the signal used for probing of the atmosphere and ionosphere are found, which evidences wave perturbations of the medium near the lower boundary of the daytime ionosphere of Venus.

Inter-hemispheric analysis of daytime low ionosphere behavior from 2007 to 2011

The lower ionosphere behavior from 2007 to 2011 is studied using VLF signals propagating over long distances and received at Comandante Ferraz Brazilian Antarctic Station and Atibaia/Brazil. The VLF signals show high day-to-day variations of the mid-day amplitude, which present a clear seasonal behavior occurring predominantly during wintertime in all years. These high VLF amplitude variations show a significant component with 16-day period, which is typical of planetary waves of stratospheric/tropospheric origin. These results reinforced the solar control of the lower ionosphere and the evidence of vertical couplings in the atmosphere-ionosphere system, even during the 24th solar cycle increasing activity.

Planetary wave coupling of the atmosphere–ionosphere system during the Northern winter of 2008/2009

This paper presents the global spatial (latitude and altitude) structure and temporal variability of the ∼23-day ionospheric zonally symmetric (s=0) planetary wave (PW) seen in the Northern winter of 2008/2009 (October 2008–March 2009). It is shown that these ∼23-day ionospheric oscillations are forced from PWs propagating from below. The COSMIC ionospheric parameters foF2 and hmF2 and electron density at fixed altitudes and the SABER temperatures were utilized in order to define the waves which are present simultaneously in the atmosphere and ionosphere. The long-period PWs from the two data sets have been extracted through the same data analysis method. The similarity between the lower thermospheric ∼23-day (s=0) temperature PW and its ionospheric electron density response provides valuable and strong experimental evidence for confirming the paradigm of atmosphere–ionosphere coupling.

On the role of ozone in long-term trends in the upper atmosphere-ionosphere system

Abstract. Origin of long-term trends in the thermosphere-ionosphere system has been discussed since the beginning of trend studies. The two most prioritized explanations have been those via long-term increase of atmospheric concentration of greenhouse gases and long-term increase of geomagnetic activity throughout the 20th century. Secular changes of the Earth's main magnetic field play an important role in trends in a limited region. Recently, Walsh and Oliver (2011) suggested that the long-term cooling of the upper thermosphere (above 200 km) may be due largely to the stratospheric ozone depletion. Here, we show that the role of ozone is very important in the mesosphere and lower thermosphere but not in the upper thermosphere. The suggestion of Walsh and Oliver (2011) is based on historical (before 1988) data from Saint-Santin radar, whereas more recent data do not support their conclusion.

Analysis of daytime ionosphere behavior between 2004 and 2008 in Antarctica

In this paper we present 5-year study of the lower ionosphere behavior obtained from VLF sounding done at Comandante Ferraz Brazilian Antarctic Station. The results suggested a strong influence of ‘meteorological processes’ especially during wintertime, when VLF measurements showed that the D-region was strongly affected by planetary waves in all years. This effect was superposed to the well known control by solar radiation. The 16-day wave was the most important PW modulating the lower ionosphere behavior. Since planetary waves are very predominantly of tropospheric origin, this result is an evidence of the vertical couplings in the atmosphere–ionosphere system.