Search

The electron/ion density/temperature and ion velocities observed by the ROCSAT-1 and DEMETER satellites are used to examine the daytime wavenumber-4 (WN4) feature in the equatorial/low latitude ionosphere during various months and solar activity levels of 1999–2010. A moving median process has been employed to isolate WN4 features and calculate their amplitudes, while the upward ion drift is used to estimate electric fields. The ROCSAT-1 and DEMETER ion density, ion temperature, and ion velocity generally yield prominent WN4 features over the center of Pacific Ocean, the west side of South America, the center of the Atlantic Ocean, and Southern India. The correlation coefficient between the deviation of ion density and upward ion drift is significant during high solar activity of 1999–2004, while it approaches to zero during low solar activity of 2004–2010. This confirms that the longitudinal variation of the upward ion drift is essential during high solar activity, and the associated amplitude of dynamo eastward electric field is in the range of 0.10–0.14 mV/m, which is 15–19% of daily dynamo electric field. By contrast, the deviation of the ion density and the northward field-aligned ion flow show a clear anti-correlation which yields a maximum coefficient in August during low solar activity but no correlation during high solar activity. These indicate that the longitudinal variation of the meridional field-aligned ion flow could play an important role during low solar activity, and its amplitude is in the range of 10.44–13.91 m/s, which is 10–13% of the ambient ion flows.

The receiver operating characteristic (ROC) and the area under the curve (AUC), initially developed for signal processing and psychology, are a test for assessing the performance of a binary classification problem at varying threshold values. The ion density (Ni) observed by FORMOSAT‐7/COSMIC‐2 is used to study traveling ionospheric disturbances (TIDs) triggered by the 15 January 2022 Tonga volcanic eruption. We examine parameters of Ni, differential Ni, and standard deviation Ni(STD_Ni) in January 2022, simulate TID wavefronts traveling with various speeds from 10 to 1,000 m/s, and apply the ROC curve to globally identify the significance of TIDs in STD_Ni triggered by the volcanic eruption. ROC and AUC results show that in addition to TIDs related to tsunami/tropospheric Lamb waves and a series of fast‐moving waves with propagation speeds of 180–350 and 450–600 m/s, respectively, those long‐lasting low‐speeds less than 70 m/s and high‐speeds about 690, 860, and 990 m/s meet 95% statistical significance, which confirms TIDs being detected. These show that the FORMOSAT‐7/COSMIC‐2 ion density can be used to globally detect various TIDs triggered by the Tonga volcanic eruption. The ROC test results also show a potential use case for detecting other geophysical signals in future applications. Large‐scale natural phenomena such as volcanoes and tsunami induce prominent traveling atmospheric disturbances (TADs) which also simultaneously and locally influence the above ionosphere activating prominent traveling ionospheric disturbances (TIDs). To assess the significance of such TIDs, we treat the TIDs as a series of signals, and the receiver operating characteristic (ROC) and the area under the curve (AUC), developed to address binary classification problems, are used to evaluate these signals at varying threshold values. The 15 January 2022 Tonga volcanic eruption triggers a series of TADs, TIDs, and tsunami waves propagating around the globe. Measurements of the ion density (Ni) by IVM (ion velocity meter) onboard FORMOSAT‐7/COSMIC‐2 (F7C2) are used to identify TIDs triggered by the volcanic eruption. We examine TIDs of F7C2 Ni, differential Ni, and standard deviation (STD) of Niin January 2022, and find that TIDs associated with the tsunami waves, tropospheric Lamb waves, and high‐speed waves within 450–600 m/s triggered by the Tonga volcanic eruption on the globe are very prominent on the eruption day. In addition, TIDs with long‐lasting low‐speeds less than 70 m/s and high‐speeds about 690, 860, and 990 m/s can be identified in the ROC curves and AUC indices. The FORMOSAT‐7/COSMIC‐2 ion density globally observes various traveling ionospheric disturbances triggered by the Tonga volcanic eruptionThe receiver operating characteristic (ROC) test can detect traveling ionospheric disturbances and potentially other geophysical signalsDisturbances with low‐speeds of 10–70 m/s, tsunami, tropospheric Lamb wave, and high‐speeds of 490/690/860/990 m/s are identified The FORMOSAT‐7/COSMIC‐2 ion density globally observes various traveling ionospheric disturbances triggered by the Tonga volcanic eruption The receiver operating characteristic (ROC) test can detect traveling ionospheric disturbances and potentially other geophysical signals Disturbances with low‐speeds of 10–70 m/s, tsunami, tropospheric Lamb wave, and high‐speeds of 490/690/860/990 m/s are identified

Human c-mycis critical for cell homeostasis and growth but is a potent oncogenic factor if improperly regulated. The c-mycfar-upstream element (FUSE) melts into single-stranded DNA upon active transcription, and the noncoding strand FUSE recruits an activator [the FUSE-binding protein (FBP)] and a repressor [the FBP-interacting repressor (FIR)] to fine-tune c-myctranscription in a real-time manner. Despite detailed biological experiments describing this unique mode of transcriptional regulation, quantitative measurements of the physical constants regulating the protein−DNA interactions remain lacking. Here, we first demonstrate that the two FUSE strands adopt different conformations upon melting, with the noncoding strand DNA in an extended, linear form. FBP binds to the linear noncoding FUSE with a dissociation constant in the nanomolar range. FIR binds to FUSE more weakly, having its modest dissociation constants in the low micromolar range. FIR is monomeric under near-physiological conditions but upon binding of FUSE dimerizes into a 2:1 FIR2−FUSE complex mediated by the RRMs. In the tripartite interaction, our analysis suggests a stepwise addition of FIR onto an activating FBP−FUSE complex to form a quaternary FIR2−FBP−FUSE inhibitory complex. Our quantitative characterization enhances understanding of DNA strand preference and the mechanism of the stepwise complex formation in the FUSE−FBP−FIR regulatory system.

A moon shadow of the total solar eclipse swept through the continent of United States (CONUS) from west to east on 21 August 2017. Massive total electron content (integration of electron density from 0 km to 20,200 km altitude) observations from 2,255 ground‐based Global Navigation Satellite System receivers show that the moon shadow ship generates a great ionospheric bow wave front which extends ~1,500 km away from the totality path covering the entire CONUS. The bow wave front consists of the acoustic shock wave due to the supersonic/near‐supersonic moon shadow ship and the significant plasma recombination due to the reduction in solar irradiation within the shadow area. The deep bow wave trough (−0.02 total electron content unit (1 TECU = 1016el m−2) area) nearly coincides with the 100% obscuration moving along the totality path over the CONUS through the entire eclipse period. The supersonic moon shadow ship induces a bow wave crest in front of the ship (~80% obscuration). It is the first time to find the acoustic shock wave‐formed bow wave trough and crest near the totality. A 3,000 km wide ionospheric bow wave front is induced by the moon shadow ship of the 21 August 2017 total solar eclipse over CONUSThe TEC depression contributes to the wide bow wave frontThe acoustic shock wave induces the bow wave crest and trough near the totality

GluA2R is the edited isoform at the Q/R site of the AMPA receptor GluA2 subunit. In vivo, GluA2R assembles with other AMPA receptor subunits into a high-conductance, tetrameric complex. Here we study the functional role of GluA2R in the context of GluA1/2R and GluA2Q/2R heteromeric receptors, using whole-cell recording and a laser-pulse photolysis technique. We find the incorporation of GluA2R with GluA1 or GluA2Q slows the channel-opening and channel-closing rates; for GluA2Q/2R, it further lowers EC50, compared to the value of the GluA2Q homomeric channels. When a conserved leucine-to-tyrosine (L → Y) mutation is “placed” in each of these subunits, the L → Y mutation exhibits a greater effect in GluA2R than in GluA1. Together, our results show GluA2R is the dominating isoform that shapes the overall functional properties of the GluA2R-containing channels. Our results further suggest that glutamate most likely binds to GluA2R with an EC50of ∼0.5 mM, rather than a non-GluA2R subunit in a heteromeric AMPA receptor, and binding of two glutamate molecules to the two GluA2R subunits is sufficient to initiate a conformational change, leading to the opening of the channel.

The Abel inversion of ionospheric electron density profiles with the assumption of spherical symmetry applied for radio occultation soundings could introduce a greater systematic error or sometimes artifacts if the occultation rays trespass regions with larger horizontal gradients in electron density. The aided Abel inversions have been proposed by considering the asymmetry ratio derived from ionospheric total electron content (TEC) or peak density (NmF2) of reconstructed observation maps since knowledge of the horizontal asymmetry in ambient ionospheric density could mitigate the inversion error. Here we propose a new aided Abel inversion using three‐dimensional time‐dependent electron density (Ne) based on the climatological maps constructed from previous observations, as it has an advantage of providing altitudinal information on the horizontal asymmetry. Improvement of proposed Ne‐aided Abel inversion and comparisons with electron density profiles inverted from the NmF2‐ and TEC‐aided inversions are studied using observation system simulation experiments. Comparison results show that all three aided Abel inversions improve the ionospheric profiling by mitigating the artificial plasma caves and negative electron density in the daytime Eregion. The equatorial ionization anomaly crests in the Fregion become more distinct. The statistical results show that the Ne‐aided Abel inversion has less mean and RMS error of error percentage above 250 km altitudes, and the performances for all aided Abel inversions are similar below 250 km altitudes. A new method of aided Abel inversion using Ne (Ne aided) is proposed for ionospheric electron density retrievalPerformances between proposed Ne‐aided and two other existing TEC‐ and NmF2‐aided inversions are evaluated using OSSENe‐aided Abel inversion gives better results by mitigating artificial plasma caves in the Eregion and making the Fregion EIA crests more distinct

Seismic waves can be detected in the Earth's atmosphere and ionosphere; however, their impacts on ionospheric electron density (Ne) structures near the altitude of peak Ne(hmF2) have not yet been fully determined due to the lack of sufficient observations sampled in the vertical direction. Here we apply a ground-based Global Positioning System (GPS) receiving network in Asia as well as the space-based GPS occultation experiment on board the FORMOSAT-3/COSMIC (F3/C) satellite to vertically scan the ionospheric Nestructures, which were perturbed by the magnitude Mw7.8 Nepal earthquake that occurred on 25 April 2015. The F3/C altitudinal Neprofiles show that the Nepal earthquake-induced air perturbations penetrate into the ionosphere at supersonic speeds of approximately 800?m/s and change the Nestructure by 10% near hmF2. The vertical scale of the Neperturbation is 150?km, while the hmF2is uplifted by more than 30?km within 1?min. Those results reveal that the earthquake-induced ground displacement should be considered as a significant force that perturbs the vertical Nestructure of the ionosphere. Coseismic ionospheric disturbance observed by FORMOSAT-3/COSMICNear-supersonic uplifting of the ionospheric F2peak caused by the Nepal earthquakeVertical scale of the coseismic disturbance is near 150?km in the F2region

FORMOSAT-3/COSMIC (F3/C) constellation of six micro-satellites was launched into the circular low-earth orbit at 800 km altitude with a 72-degree inclination angle on 15 April 2006, uniformly monitoring the ionosphere by the GPS (Global Positioning System) Radio Occultation (RO). Each F3/C satellite is equipped with a TIP (Tiny Ionospheric Photometer) observing 135.6 nm emissions and a TBB (Tri-Band Beacon) for conducting ionospheric tomography. More than 2000 RO profiles per day for the first time allows us globally studying three-dimensional ionospheric electron density structures and formation mechanisms of the equatorial ionization anomaly, middle-latitude trough, Weddell/Okhotsk Sea anomaly, etc. In addition, several new findings, such as plasma caves, plasma depletion bays, etc., have been reported. F3/C electron density profiles together with ground-based GPS total electron contents can be used to monitor, nowcast, and forecast ionospheric space weather. The S4 index of GPS signal scintillations recorded by F3/C is useful for ionospheric irregularities monitoring as well as for positioning, navigation, and communication applications. F3/C was officially decommissioned on 1 May 2020 and replaced by FORMOSAT-7/COSMIC-2 (F7/C2). F7/C2 constellation of six small satellites was launched into the circular low-Earth orbit at 550 km altitude with a 24-degree inclination angle on 25 June 2019. F7/C2 carries an advanced TGRS (Tri Gnss (global navigation satellite system) Radio occultation System) instrument, which tracks more than 4000 RO profiles per day. Each F7/C2 satellite also has a RFB (Radio Reference Beacon) on board for ionospheric tomography and an IVM (Ion Velocity Meter) for measuring ion temperature, velocity, and density. F7/C2 TGRS, IVM, and RFB shall continue to expand the F3/C success in the ionospheric space weather forecasting.

The sudden eruption of the Tonga underwater volcano (20.53°S, 175.38°W) on 15 January 2022 generated explosions that triggered blast waves traveling away from the eruption. In this study, the analysis of the geomagnetic field observations on the ground shows that the eruption perturbed the E‐region current density by 22–55 mA/m within a radius of 8,000 km away from the eruption. The perturbation evolved into large scales of ∼5 hr and thousands of kilometers as it traveled away. The traveling speed of the leading front is ∼740 m/s that is near acoustic in the ionosphere. The magnetic fields and total electron content observations suggest that the dynamics changes further induced significant ionospheric disturbances that lasted ∼10 hr after the eruption. The examination of the Tonga volcanic eruption inspires us that a near‐surface perturbation can change the dynamics of the upper atmosphere. As we drop a stone into the still water, the water piles up around the rock and induces ripples in the form of concentric circles that expand and travel away from the center point. A similar phenomenon happened in the atmosphere after the eruption of the Tonga underwater volcano (20.53°S, 175.38°W) at ∼04:15 UT on 15 January 2022. The Earth's atmosphere is a pond of air. The explosive eruption triggered prosperous waves, which is similar to dropping a stone into water. The waves, ripples, and disturbances in different spheres are fantastic due to the eruption (Figure S8 in Supporting Information S1). Besides the tsunamis, atmospheric concentric ripples, and ionospheric traveling disturbances, this study for the first time showed that the blast wave due to the eruption changed the dynamics of the ionosphere or thermosphere (upper atmosphere). It is well known that a significant volcanic eruption can release tremendous ashes and gases into the troposphere and stratosphere (lower atmosphere), which change the chemical and dynamic process there. The observations in this study surprisingly show that the eruption changed the dynamics of the upper atmosphere, where the volcanic cloud cannot reach. The eruption of the Tonga underwater volcano perturbed the E‐region current and, in turn, changed the geomagnetic field by ∼20–50 nTA large near‐surface perturbation can modulate the ionospheric dynamics and further induce ionospheric disturbancesThe significant ionospheric disturbances with periods ranging from several minutes to hours lasted more than 10 hr after the eruption The eruption of the Tonga underwater volcano perturbed the E‐region current and, in turn, changed the geomagnetic field by ∼20–50 nT A large near‐surface perturbation can modulate the ionospheric dynamics and further induce ionospheric disturbances The significant ionospheric disturbances with periods ranging from several minutes to hours lasted more than 10 hr after the eruption

The longest total solar eclipse in the 21st century occurred in Southeast Asia on 22 July 2009 from 00:55 to 04:15 UT, and was accompanied by a moderate magnetic storm starting at 03:00 UT with a Dstreduction of −78 nT at 07:00 UT. In this study, we use the ionospheric reference model IRI, the data assimilation model MAGIC, and ground-based GPS receivers to simulate and examine the ionospheric solar eclipse and geomagnetic storm signatures in Taiwan and Japan. Cross-comparisons between the two model results and observations show that IRI fails to simulate the two signatures while MAGIC partially reproduces the storm features. It is essential to include ground-based GPS measurements to improve the IRI performance.

The electrochemical polymerization conditions for the synthesis of spirobifluorene-based polymer (EF-CN1) films with adequate properties to be applied in an organic light emitting diode (OLED) were studied. We demonstrate that, after optimization in the parameters of electrochemical polymerization, we were able to obtain a conducting polymeric film with very smooth surface, absence of pinholes, and high optoelectronic activity, which was compatible as an efficient hole transporting layer in OLED. The electrochemical deposited polymers, and polymer films obtained through drop casting from solution of chemically synthesized polymer (C-CN1),were characterized and the results compared. The films were studied by cyclic voltammetry, UV–vis, fluorescence spectra, scanning electron mictroscopy, and atomic force microscopy. The built OLEDs achieve current-luminous efficiency and external quantum efficiency of 2.6 cd/A and 0.50%, respectively.

The effect of thermal annealing on the performance of polymer light-emitting diodes (PLEDs) with a cationic conjugated polyelectrolyte as an electron injection layer is investigated. Thermal annealing at 180 °C leads to the loss of ionic content via Hofmann elimination and, hence, increases the device turn-on voltage. The ability to reduce the ionic charge density opens opportunities to design experiments for disentangling the operating mechanism for the reduction of electron injection barriers in PLEDs.

The synthesis and photophysical, electrochemical, and spectroelectrochemical characterization of a novel donor−acceptor (D−A) bichromophore system composed of two D−A segments linking through a spiro center are reported. The electron-donating (D) moieties are triphenylamine (TPA) groups, whereas the electron-withdrawing (A) moieties are cyano groups. The particular “spiro” configuration that perpendicularly bonds the D−A chromophores by a tetrahedral carbon, impedes orbital interactions between the branches. Thus, the two TPA substituents act independently, rendering an efficient electropolymerization process feasible. The polymer film obtained showed reversible electrochemical oxidation accompanied by strong color changes with high coloration efficiency and contrast ratio, which can be switched by potential modulation. The remarkable electrochromic behavior of the film is clearly interpreted on the basis of spectroelectrochemical studies. A plausible polymerization mechanism involved with the TPA dimerization reaction is proposed for the electropolymerization process.

This study shows that a supersonic moon shadow of a total solar eclipse can steepen the ionospheric total electron content (TEC) wave on August 21, 2017. A data‐adaptive method named Hilbert‐Huang transform is employed to examine the nonlinear and non‐stationary evolution of the waves. The results show that the TEC wave behaves as a traveling ionospheric disturbance before the totality appearance, turns later into steepening, and breaks eventually. A TEC wave with a period of ∼40 min and wavelength of ∼1,000 km propagates mainly in an east‐southward direction before the totality appearance. The wave amplitude and scales, respectively, increases and reduce by near ∼50% as the moon shadow approaches the western coast of the continental United States. The short‐period TEC waves (period ∼2 min) reveal that the wave may break eventually when the wave gets steeper. The steepness of the TEC wave is reconstructed according to the constructive interference. A water wave increasing in height and shortening in wavelength as it propagating is the best‐known example of wave steepening that we often can see near the shore. For the first time, this study shows that a supersonic moon shadow of a total solar eclipse can also steepen the wave of electron density in the Earth's ionosphere over the western coast of the continental United States. The wave propagates in an east‐southward direction over Oregon and California. The evolution of electron density wave (wavelength ∼1,000 km) is similar to a big water wave for surfing in the ionosphere (Movie S1). The results suggest that the dense GNSS arrays developing in the recent decade turn the Earth's ionosphere into one of the best available outdoor laboratories for detecting and examining the wave and dynamics. The TEC wave gets steeper as the supersonic moon shadow approaches the western coast of the continental United States on August 21, 2017The intense bow‐wave crest ahead of the moon shadow can be attributed to the constructive interferenceThe data‐adaptive method, Hilbert‐Huang transform, benefits to extract the nonlinear and non‐stationary waves from TEC time series The TEC wave gets steeper as the supersonic moon shadow approaches the western coast of the continental United States on August 21, 2017 The intense bow‐wave crest ahead of the moon shadow can be attributed to the constructive interference The data‐adaptive method, Hilbert‐Huang transform, benefits to extract the nonlinear and non‐stationary waves from TEC time series

The ionospheric total electron content (TEC) derived from dense ground‐based Global Navigation Satellite System receivers over the continental United States and those from global ionosphere maps are utilized to find the ionosphere response to the August 21, 2017 total solar eclipse. Maximum obscurations and their associated TEC major depressions appear simultaneously at midlatitudes, while major depressions elongate toward the magnetic equator with some delays in the equatorial ionization anomaly (EIA) region. The former is due to the photochemical loss process, while the latter is caused by the plasma transport of E×Bdrifts and lunar gravitation forces. TECs of predawn reductions, morning enhancements, afternoon reductions, and nighttime enhancements reveal that the semidiurnal lunar tide are essential. Since a solar eclipse always occurs on a new moon day, the lunar tide results in the early EIA appearance and major depressions being underestimated/diminished before and overestimated/enhanced after about 14:00 local time. Observations during an eclipse offer a special opportunity for studying the Earth's ionospheric response to changes in solar ionizing radiation. Although ionospheric solar eclipse signatures in many events have been studied, we report the lunar tide effect on the signatures for the first time. A total solar eclipse swept across the continental United States (CONUS) from the west to east coast on August 21, 2017. The total electron content (TEC) along seven longitudes of the US continent derived from more than 2,200 ground‐based Global Navigation Satellite System receivers in the CONUS and extracted from global ionosphere maps (GIMs) is employed to study ionospheric solar eclipse signatures. The most prominent solar eclipse signature is major depressions (MDs) in both the CONUS and GIM TECs, when the maximum obscuration occurs. TEC extrema of predawn reductions, morning enhancements, afternoon reductions, and nighttime enhancements reveal that the semidiurnal lunar tide of about 12.42‐h period is prominent. The lunar tide causes the early appearance of equatorial ionization anomalies, which further results in the MDs being weakened in the morning and enhanced in the afternoon on the solar eclipse day. The lunar tide has to be taken into consideration for studying ionospheric solar eclipse effects. The lunar tide results in the early appearance of the equatorial ionization anomaly on solar eclipse daysTotal electron contents tend to enhance before and decrease after 14:00 local time (LT) on a solar eclipse dayThe lunar tide causes major depressions being weakened before and enhanced after 14:00 LT The lunar tide results in the early appearance of the equatorial ionization anomaly on solar eclipse days Total electron contents tend to enhance before and decrease after 14:00 local time (LT) on a solar eclipse day The lunar tide causes major depressions being weakened before and enhanced after 14:00 LT

The FORMOSAT‐7/COSMIC‐2 (F7/C2) satellite mission was launched on 25 June 2019 with six low‐Earth‐orbit satellites and can provide thousands of daily radio occultation (RO) soundings in the low‐latitude and midlatitude regions. This study shows the preliminary results of space weather data products based on F7/C2 RO sounding: global ionospheric specification (GIS) electron density and Ne‐aided Abel and Abel electron density profiles. GIS is the ionospheric data assimilation product based on the Gauss‐Markov Kalman filter, assimilating the ground‐based Global Positioning System and space‐based F7/C2 RO slant total electron content, providing continuous global three‐dimensional electron density distribution. The Ne‐aided Abel inversion implements four‐dimensional climatological electron density constructed from previous RO observations, which has the advantage of providing altitudinal information on the horizontal gradient to reduce the retrieval error due to the spherical symmetry assumption of the Abel inversion. The comparisons show that climatological structures are consistent with each other above 300 km altitude. Both the Abel electron density profiles and GIS detect electron density variations during a minor geomagnetic storm that occurred within the study period. Moreover, GIS is further capable of reconstructing the variation of equatorial ionization anomaly crests. Detailed validations of all the three products are carried out using manually scaled digisonde NmF2(hmF2), yielding correlation coefficients of 0.885 (0.885) for both Abel inversions and 0.903 (0.862) for GIS. The results show that both GIS and Ne‐aided Abel are reliable products in studying ionosphere climatology, with the additional advantage of GIS for space weather research and day‐to‐day variations. This study presents two ionosphere products from the innovative satellite constellation mission launched recently. Global ionospheric specification is an ionospheric data product that assimilates ground‐based Global Positioning System and FORMOSAT‐7/COSMIC‐2 radio occultation observation of total electron content, to generate hourly global three‐dimensional electron density for monitoring space weather condition. Ne‐aided Abel electron density profile is an improved retrieval product of FORMOSAT‐7/COSMIC‐2 radio occultation observations by imposing asymmetry information of ionosphere to mitigate the error introduced by the assumption of spherical symmetry in the Abel inversion. The comparisons and validations confirm that these two data products are reliable for the study of ionosphere climatology and weather. They are operationally produced and released at Taiwan Analysis Center for COSMIC. All the three F7/C2 products capture similar climatological structure of ionosphere in longitudes (Wave 4) and latitudes (EIA crests)Abel electron density profiles detect responses to geomagnetic storm, but GIS performs better in reconstructing the EIA crests variationsDigisonde validations demonstrate that the GIS NmF2has excellent performance when there are RO observations available for assimilation

The strength, appearance time, and latitudinal location of the equatorial ionization anomaly (EIA) crest response to the lunar phase are examined using the total electron content of global ionosphere maps during the 18‐year period of 2000–2017. The total electron content of the EIA crest reveals semidiurnal tides with 12.42‐hr period, while the appearance time and latitude of the EIA crests present prominent semimonthly lunar tides of 14.77‐day period. The EIA crests on new/full moon (first/third quarter) lead (lag) those of the overall 18‐year average by about 20–40 min, while the EIA crests move the furthest poleward and equatorward 2–5 days after new/full moon and first/third quarter, respectively. Amplitudes of the semimonthly lunar tide in the EIA crest appearance times and latitudes yield the greatest value around perihelion and the smallest value around aphelion, which shows that the solar declination and seasonal effects are important. The most prominent feature in the ionosphere is the equatorial ionization anomaly (EIA), which is characterized by two enhanced plasma crests at low latitudes straddling the magnetic equator. Global ionosphere maps of total electron content are analyzed to see how the ionospheric EIA crests respond to changes in lunar phases and solar declinations. The results show that the EIA crests exhibit prominent semimonthly lunar tides with 14.77‐day period. Appearance times of the EIA crests on new/full moon (first/third quarter) lead (lag) those on the associated overall 18‐year average by about 20–40 min, while the EIA crests move the furthest poleward during new/full moon and equatorward during first/third quarter with the delays of about 2–5 days. These indicate that the lunar phase can significantly modulate the ionospheric EIA. The semimonthly lunar tide in the crest appearance times and latitudes become most prominent around perihelion but the least around aphelion, which shows that the solar declination and seasonal effects are important. Appearance times of the EIA crests on new/full moon lead those on first/third quarterThe EIA crests move most poleward (equatorward) 2–5 days after new/full moon (first/third quarter)The semimonthly lunar tide of the EIA crest becomes most prominent around perihelion

Tsunami waves can induce tsunami traveling ionospheric disturbances (TTIDs) of the total electron content (TEC). In this study, we examine the TEC derived by ground-based receivers of the global positioning system (GPS) and identify TTIDs induced by 2004 Indian Ocean tsunami. Simulations of the COMCOT (Cornell multi-grid coupled tsunami) model and analyses of the circle method, the ray-tracing technique, and the beam-forming technique are used to show that TTIDs can be quickly detected and confirmed after the tsunami occurrence. Finally, the ionospheric TEC derived by existing ground-based GNSS (Global Navigation Satellite Systems) receiving stations is demonstrated to be useful to support the tsunami early warning system.