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Magnetospheric line radiation (MLR) is a peculiar type of whistler‐mode emissions formed by several similarly spaced spectral lines, whose frequencies may vary with time. These emissions typically occur at frequencies between about 1 and 8 kHz and are observed in both ground‐based and satellite measurements. However, their origin and source locations are not yet understood, as their detection by spacecraft instruments is challenging due to the limited frequency resolution of onboard wave measurements. We use high‐resolution multicomponent wave data obtained by the Van Allen Probes to demonstrate that, in addition to the frequency modulation, MLR events possess a temporal modulation with periods on the order of seconds, which may be related to the wave bouncing between hemispheres. Observed modulation periods are used to estimate a tentative source L‐shell. The modulation periods are shorter for events with larger frequency spacing, and the estimated source L‐shells correlate with model plasmapause locations. Plain Language Summary: Electromagnetic waves with frequencies of a few kHz observed in the near‐Earth space, the magnetosphere, sometimes exhibit distinct frequency modulation. When represented in traditional frequency‐time spectrograms, with wave intensity color‐coded as a function of frequency and time, these waves appear as several nearly equidistant spectral lines. They are called magnetospheric line radiation (MLR). Although they have been observed by both ground‐based and spacecraft instruments, their origin is still not understood. We use high‐resolution data obtained by the Van Allen Probes spacecraft to show that MLR intensity is modulated not only in frequency but also in time, with modulation periods on the order of seconds. The available wave measurements allow us to determine not only wave intensity but also propagation directions. This is used to demonstrate that the observed temporal modulation corresponds, with some uncertainties, to a wave element bouncing back and forth between hemispheres. Using the theory of wave propagation in plasma, the bouncing periods can be used to calculate the distance of the magnetic field line where the wave bounces, that is, the distance of a tentative wave source. Our results help to understand possible generation mechanisms and source locations of these peculiar emissions. Key Points: Magnetospheric line radiation may have a fine temporal structure related to the wave bouncing between hemispheresAnalysis of the corresponding modulation periods allows estimation of the L‐shell of a tentative sourceTentative source locations of analyzed events with the fine temporal structure correlate with the model plasmapause locations [ABSTRACT FROM AUTHOR]

We use conjugate observations of magnetospheric whistler‐mode waves at frequencies up to 16 kHz by the DEMETER spacecraft (at an altitude of approximately 660 km) and the ground‐based Kannuslehto station in Finland (L≈5.38) $(L\approx 5.38)$ to investigate the wave propagation to the ground and their characteristic spatial scales. For this purpose, we evaluate correlations between the wave intensities measured by the spacecraft and the ground‐based station at various frequencies as a function of their longitudinal and L‐shell separations. Two different approaches are used: (a) direct correlation of wave intensities measured at the same times and (b) correlation of wave intensities within corresponding frequency‐time windows, focusing on the identification of the same frequency‐time wave signatures. We show that the characteristic longitudinal scales of the investigated waves are between about 60° $60{}^{\circ}$ and 90° $90{}^{\circ}$. We further demonstrate that, while the wave intensities measured by DEMETER are generally larger during periods of enhanced geomagnetic activity, wave intensities measured on the ground during increased activity are only slightly larger during the daytime and decrease during the nighttime. Key Points: Overall correlations of whistler‐mode wave intensities at low altitudes (660 km) and on the ground are evaluated for the first timeCharacteristic longitudinal scales of observed waves are approximately between 60 and 90°Nighttime wave intensities measured on the ground are lower during geomagnetically active periods [ABSTRACT FROM AUTHOR]

We evaluate average wave intensities at frequencies up to 10 kHz measured by two ground stations in Canada and two others in Finland at auroral and subauroral latitudes over a full year, as well as by the low‐altitude DEMETER spacecraft during the years 2004–2010. Lightning location and energy data obtained by the World Wide Lightning Location Network, along with geomagnetic activity characterized by the Kp index, are further used. Latitudinal, diurnal, and annual variations are analyzed, and the global intensities measured on the ground and by the spacecraft are systematically compared for the first time. We show that lightning‐generated waves often dominate the measured wave intensities, particularly during the night, in summer, and at higher frequencies. DEMETER observations, supported by ray‐tracing analysis, reveal a significant role of nonducted lightning‐generated whistler propagation between the hemispheres. Finally, the wave intensity response to geomagnetic activity variations is quite different on the ground compared to in space. While spacecraft‐measured wave intensities are considerably larger during periods of enhanced geomagnetic activity, the ground‐based intensities are only sporadically enhanced during geomagnetically active periods. Key Points: A global comparison of wave intensities measured by the DEMETER satellite and the Kannuslehto/PWING ground stations is performedLightning‐generated waves often dominate both DEMETER and ground observations, especially at night, in summer, and at higher frequenciesDaytime intensities measured by DEMETER are larger during active periods, while on the ground they are only sporadically enhanced [ABSTRACT FROM AUTHOR]

High energy resolution DEMETER satellite observations from the Instrument for the Detection of Particle (IDP) are analyzed during an electromagnetic ion cyclotron (EMIC)‐induced electron precipitation event. Analysis of an Interval Pulsation with Diminishing Periods (IPDP)‐type EMIC wave event, using combined satellite observations to correct for incident proton contamination, detected an energy precipitation spectrum ranging from ∼150 keV to ∼1.5 MeV. While inconsistent with many theoretical predictions of >1 MeV EMIC‐induced electron precipitation, the finding is consistent with an increasing number of experimentally observed events detected using lower resolution integral channel measurements on the POES, FIREBIRD, and ELFIN satellites. Revised and improved DEMETER differential energy fluxes, after correction for incident proton contamination shows that they agree to within 40% in peak flux magnitude, and 85 keV (within 40%) for the energy at which the peak occurred as calculated from POES integral channel electron precipitation measurements. This work shows that a subset of EMIC waves found close to the plasmapause, that is, IPDP‐type rising tone events, can produce electron precipitation with peak energies substantially below 1 MeV. The rising tone features of IPDP EMIC waves, along with the association with the high cold plasma density regime, and the rapidly varying electron density gradients of the plasmapause may be an important factor in the generation of such low energy precipitation, co‐incident with a high energy tail. Our work highlights the importance of undertaking proton contamination correction when using the high‐resolution DEMETER particle measurements to investigate EMIC‐driven electron precipitation. Plain Language Summary: Energetic electrons are lost rapidly from the outer radiation belt. Several processes are thought to drive the electron losses. One process is through interactions with electromagnetic ion cyclotron (EMIC) waves. Theoretical studies suggest that electrons primarily with energy >1 MeV are lost through this process, however, previous experimental satellite observations indicate that precipitation bursts with much lower electron energies are more common. One issue is that the previous satellite observations were made with poor energy resolution and are challenging to interpret due to coincident proton precipitation, which contaminate the electron measurements. Here we use observations from the DEMETER satellite which we have corrected for proton contamination. The measurements, made with higher energy resolution than before, confirm that indeed, low energy electron precipitation can happen when EMIC waves drive electron losses. The study finds that this lower energy characteristic is likely to be driven by a small subset of rising tone EMIC waves, known as Interval Pulsation with Diminishing Periods (IPDP), typically confined to the magnetic local time evening sector. Key Points: An electromagnetic ion cyclotron wave event (an interval of pulsations with diminishing period, IPDP) was studied from Low Earth OrbitCo‐incident satellite observations detected IPDP‐induced energetic electron precipitation, starting at 150 keV, peaking at 215 keVHigh‐resolution measurements from the DEMETER satellite show enhanced fluxes from 215 keV to 1.5 MeV exhibiting a "hard" power‐law spectrum [ABSTRACT FROM AUTHOR]

An open data lake stores various forms and types of open data, and there is an increasing demand to manage raw data in tables rather than files for efficient data exploration and analysis. In this paper, we investigate the data management of open data lakes and recognize the limitations of table migration and related problems. First, open data lakes have problems of preprocessing complexity, scale limitation, and platform dependency due to the traditional data management method and open data characteristics. Second, existing studies for table migration have problems of lack of scalability, migration incompleteness, and scale limitation. In this work, we present a novel automation framework, called Demeter, which solves three problems inherent in open data lakes by expanding automation. Specifically, it supports automating catalog collection and preprocessing tasks to solve preprocessing complexity and scale limitation. It also supports platform universality for representative data platforms through the automation of catalog analysis and detailed processing logic. Demeter then solves three problems in table migration by adopting Airbyte, an open‐source ELT platform, and by enhancing automation capability with the Airbyte manager. We verify that Demeter resolves all the problems above through extensive experiments and proves its scalability and universality. In addition, significantly outperforms CKAN by Demeter up to 508.5% in automation performance, up to 207.28% in processing time, and up to 917.17% in migration performance. These results indicate that Demeter is an excellent automation framework that increases the utilization of large‐scale open data and supports reliable Internet‐scale migration. [ABSTRACT FROM AUTHOR]

Summary: Ectomycorrhizas are an intrinsic component of tree nutrition and responses to environmental variations. How epigenetic mechanisms might regulate these mutualistic interactions is unknown.By manipulating the level of expression of the chromatin remodeler DECREASE IN DNA METHYLATION 1 (DDM1) and two demethylases DEMETER‐LIKE (DML) in Populus tremula × Populus alba lines, we examined how host DNA methylation modulates multiple parameters of the responses to root colonization with the mutualistic fungus Laccaria bicolor. We compared the ectomycorrhizas formed between transgenic and wild‐type (WT) trees and analyzed their methylomes and transcriptomes.The poplar lines displaying lower mycorrhiza formation rate corresponded to hypomethylated overexpressing DML or RNAi‐ddm1 lines. We found 86 genes and 288 transposable elements (TEs) differentially methylated between WT and hypomethylated lines (common to both OX‐dml and RNAi‐ddm1) and 120 genes/1441 TEs in the fungal genome suggesting a host‐induced remodeling of the fungal methylome. Hypomethylated poplar lines displayed 205 differentially expressed genes (cis and trans effects) in common with 17 being differentially methylated (cis).Our findings suggest a central role of host and fungal DNA methylation in the ability to form ectomycorrhizas including not only poplar genes involved in root initiation, ethylene and jasmonate‐mediated pathways, and immune response but also terpenoid metabolism. See also the Commentary on this article by Zimmermann & Gaillard, 238: 2259–2260. [ABSTRACT FROM AUTHOR]

Signals from the NWC ground‐based very low frequency (VLF) transmitter can leak into the magnetosphere and scatter trapped energetic electrons into drift loss cones. Recent studies also suggest that cosmic ray albedo neutron decay (CRAND) is probably an important source for quasi‐trapped electrons in the inner belt. To investigate their relative contributions, this study comprehensively analyzes the long‐term variations of quasi‐trapped 206 keV electrons at L = 1.7, which is roughly the L shell where NWC is located. Furthermore, a drift‐diffusion‐source model is used to reproduce longitudinal distributions of quasi‐trapped electrons and investigate sensitivities of simulation results to VLF transmitter intensities. These results suggest that CRAND is the main source of quasi‐trapped hundreds of keV electrons when the NWC station is at dayside. In contrast, pitch angle diffusions become the main source mechanism of these quasi‐trapped electrons when the NWC station operates at nightside with more VLF transmitter energy leaking into the magnetosphere. Plain Language Summary: Very low frequency (VLF) signals emitted from NWC transmitter locating at west Australia are used for submarine communications. The VLF signals propagate along the Earth‐ionosphere waveguide and a portion can leak into the magnetosphere. Low‐Earth orbit satellite observations demonstrate that the NWC transmitter signals in the magnetosphere can scatter trapped energetic electrons into the drift loss cone at L = 1.7, which is roughly of the L shell of the NWC location, resulting in the enhancement of approximately 200 keV quasi‐trapped electron fluxes. Cosmic ray albedo neutron decay (CRAND) describes the process that galaxy cosmic rays (the majority consist of high‐energy protons and helium nucleus) collide with atmosphere atoms and produce albedo neutrons, which have a mean lifetime of 887 s and then decay into protons, electrons, and antineutrinos, which is also considered as a source of >200 keV quasi‐trapped electrons in the inner belt. In this study, we compare the model results with DEMETER measurements and find that CRAND is the main source of quasi‐trapped hundreds of keV electrons when the NWC transmitter is at dayside. In contrast, the pitch angle diffusion induced by NWC transmitter signals becomes the main source mechanism of these quasi‐trapped electrons due to VLF signals leaking into the magnetosphere easily when the NWC transmitter operates at nightside. Key Points: CRAND is the main source of 200–700 keV quasi‐trapped electrons at L = 1.7 when NWC transmitter is at daysideFor quasi‐trapped 206 keV electrons at L = 1.7, pitch angle diffusion is the main source mechanism when NWC station operates at nightsideThe 〈Dαα〉 $\langle {D}_{\alpha \alpha }\rangle $ from NWC needs to be approximately 10−6 to 10−5 s−1 to reproduce the satellite observations of quasi‐trapped 206 keV electrons at L = 1.7 [ABSTRACT FROM AUTHOR]

Electromagnetic waves observed in the inner magnetosphere at frequencies between about 0.5 and 4 kHz sometimes exhibit a quasiperiodic (QP) time modulation of the wave intensity with modulation periods from tens of seconds up to a few minutes. Such waves are typically termed "QP emissions" and their origin is still not fully understood. We use a large set of more than 2,000 of these events identified in the low‐altitude DEMETER spacecraft data to check for energetic electron flux variations matching the individual QP wave elements. Altogether, seven such events are identified and their detailed analysis is performed. Energetic electron fluxes are found to be modulated primarily at energies lower than about 250 keV. While the waves may propagate unducted across L‐shells, the energetic particles follow magnetic field lines from the interaction region down to the observation point. This is used to estimate the locations of anticipated generation regions to L‐shells between about 4 and 6, and the respective source radial dimensions to about 0.6–1.2 Earth radii. The frequencies of the events are confined below half of the equatorial electron gyrofrequency in the determined source regions. Finally, it is shown that individual QP elements exhibit a fine inner structure corresponding to the wave bouncing between the hemispheres. Key Points: Energetic electron precipitation bursts corresponding to quasiperiodic emission peaks are identifiedInteraction regions occur at L‐shells between about 4 and 6 and have dimensions of about 0.6–1.2 Earth radiiIndividual wave elements exhibit a fine inner structure corresponding to the wave bouncing between the hemispheres [ABSTRACT FROM AUTHOR]

We constructed a program, we call "Iriatten," to calculate using parameters from the International Reference Ionosphere, attenuation of Very Low Frequency (VLF) radiation transiting the ionosphere. The calculations are performed as function of latitude, longitude, year, month, day, and hour and based upon the quasi‐longitudinal approximation put forth by Helliwell, where the wave vector k, is in the direction of propagation, and follows the Earth's magnetic field lines. The best values of various parameters are taken from the literature. Attenuation occurs through electron neutral collisions. In his seminal 1965 text, Helliwell presented atmospheric attenuation curves for day and night, 2 and 20 kHz, as a function of latitude. Program Iriatten is used to re‐calculate Helliwell's curves and then to fully exercise access to seasonality. High power VLF transmitters are utilized as a reference signal and two physical models are used to represent them. In the Vertically Inclined model, the attenuation is assumed to occur "straight up" from the location of the VLF transmitter. In the Crary model waves are launched from a dipole source and ionospheric attenuation is applied where the wave is turned up in the Earth‐ionospheric waveguide. Both representations reveal a seasonality that is unmistakable. Using the two models the ionospheric attenuation is calculated for four VLF transmitters and compared to observations by the DEMETER. Results from the Crary transmitter model more realistically portray seasonal variations exemplified by DEMETER satellite data. Crary model errors, which are within 11 dB, are lower than or comparable to Vertically Inclined errors. Key Points: There is a seasonality in VLF attenuation for waves transiting the ionosphereCrary model most accurately portrays the seasonality, as verified by DEMETER DataCrary model errors, within 11 dB, are lower than, or comparable to Vertically Inclined model errors [ABSTRACT FROM AUTHOR]

Quasiperiodic emissions are magnetospheric whistler mode waves at frequencies between about 0.5 and 4 kHz which exhibit a nearly periodic time modulation of the wave intensity. We use large data sets of events observed by the Van Allen Probes in the equatorial region at larger radial distances and by the low‐altitude DEMETER spacecraft. While Van Allen Probes observe the events at all local times and longitudes, DEMETER observations are limited nearly exclusively to the daytime and significantly less frequent at the longitudes of the South Atlantic Anomaly. Further, while the events observed by Van Allen Probes are smoothly distributed over seasons with only mild maxima in spring/autumn, DEMETER occurrence rate has a single pronounced minimum in July. The apparent inconsistency is explained by considering a nondipolar Earth's magnetic field and significant background wave intensities which in these cases prevent the quasiperiodic events from being identified in DEMETER data. Key Points: Van Allen Probes observe the quasiperiodic events at all local times and longitudes, but more often during spring and autumn seasonsDEMETER observes the events nearly exclusively during the day, with a significant longitudinal variation and minimum occurrence in JulyThe difference is explained by nondipolar Earth's magnetic field and by background wave intensities complicating DEMETER observations [ABSTRACT FROM AUTHOR]

The feasibility of detection of electromagnetic response in the upper ionosphere to ground large‐scale extremely low frequency (ELF) transmitters (e.g., submarine communication systems) by low‐orbiting satellites is discussed. Several times when the DEMETER satellite (660 km) was in the vicinity of the ELF transmitter on the Kola Peninsula, the electric and magnetic sensors operating in a burst mode detected a narrowband 82‐Hz emission. The same emission associated with the ELF transmitter was observed by a ground‐based magnetometer. We modeled the rate of the ELF wave energy leakage into the upper ionosphere from an oscillating 82‐Hz linear current with an infinite length suspended above a high‐resistive ground. A realistic altitudinal profile of the plasma parameters has been reconstructed with the use of the IRI ionospheric model. The modeled amplitudes and polarization of electromagnetic response of the upper ionosphere are in reasonable agreement with the properties of emission recorded by the satellite. Key Points: An 82‐Hz emission from ground ELF transmitter was recorded in the upper ionosphere by satellite DEMETERSpectral power of electric and magnetic components in the nightside ionosphere is about several nT2/Hz and tens of (μV/m)2/HzModeling the electromagnetic response to oscillating line current above a high‐resistive crust matches the observational result [ABSTRACT FROM AUTHOR]

Electromagnetic waves generated by lightning propagate into the plasmasphere as dispersed whistlers. They can therefore influence the overall wave intensity in space, which, in turn, is important for dynamics of the Van Allen radiation belts. We analyze spacecraft measurements in low‐Earth orbit as well as in high‐altitude equatorial region, together with a ground‐based estimate of lightning activity. We accumulate wave intensities when the spacecraft are magnetically connected to thunderstorms and compare them with measurements obtained when thunderstorms are absent. We show that strong lightning activity substantially affects the wave intensity in a wide range of L‐shells and altitudes. The effect is observed mainly between 500 Hz and 4 kHz, but its frequency range strongly varies with L‐shell, extending up to 12 kHz for L lower than 3. The effect is stronger in the afternoon, evening, and night sectors, consistent with more lightning and easier wave propagation through the ionosphere. Plain Language Summary: We analyze contribution of thunderstorms to the intensity of electromagnetic radiation at audible frequencies observed at altitudes between 600 and 32,000 km, where these waves can influence the Van Allen radiation belts. We use the World Wide Lightning Location Network to obtain information about lightning locations and times. Based on that, a lightning activity level is assigned to individual electromagnetic wave measurements of two spacecraft missions: the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions and the Van Allen Probes. Subsequently, we compare median wave intensities obtained at the times of high and low lightning activity. Their ratio reveals that the radio waves originating in strong lightning storms can significantly overpower all other natural waves in a wide range of frequencies and L‐shells. The strength of this effect substantially depends on the local time. Specifically, it is the best pronounced in the afternoon/evening/night sector and nearly absent in the morning/noon sector. This agrees with the local time dependence of both, lightning occurrence and the wave attenuation in the ionosphere. The observed lightning contribution mainly occurs at frequencies over 500 Hz and with a bandwidth decreasing from 12 to 4 kHz for L between 1.5 and 5. Key Points: WWLLN data are used to classify spacecraft measurements according to concurrent lightning activity levelLightning contributes substantially to the overall wave intensity, especially on the afternoon/evening/nightsideFrequencies of these waves start at 500 Hz with a bandwidth decreasing from 12 to 4 kHz for L between 1.5 and 5 [ABSTRACT FROM AUTHOR]

We present results of numerical simulation of quasiperiodic (QP) extra low frequency/very low frequency emissions performed by using a theoretical model of flow cyclotron maser based on a self‐consistent set of equations of the quasi‐linear plasma theory averaged over oscillations of waves and particles in a geomagnetic flux tube. Calculations were made for a wide range of plasma parameters (i.e., cold plasma density, L‐shell, and energetic electron flux) in order to obtain a statistical relationship between various properties of QP emissions, such as the repetition period, the frequency bandwidth, the frequency drift rate, and the characteristic wave spectral energy density. The theoretical results are compared with the results of a statistical study of QP emissions measured by the DEMETER spacecraft (Hayosh et al., 2014, https://doi.org/10.1002/2013JA019731). The simulation results are in a good agreement with the observation data in the case of reasonable choice of cold plasma density value and its dependence on the QP‐source location (L‐shell). In particular, an increase in the frequency bandwidth of QP very low frequency waves with increasing central frequency of QP emissions, a decrease in the frequency drift rate of QP elements with increasing repetition period, and a decrease in the characteristic wave spectral energy density with increasing repetition period are confirmed. Key Points: Numerical simulation of QP emissions for a wide range of plasma parameters is performedTheoretical results are in a good agreement with DEMETER spacecraft observationsA realistic choice of radial profile of cold plasma density is important for this agreement [ABSTRACT FROM AUTHOR]

Very low frequency electromagnetic waves in the inner magnetosphere sometimes exhibit either frequency or time modulation. These phenomena are called, respectively, magnetospheric line radiation (MLR) and quasiperiodic (QP) emissions. Data from Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions spacecraft were used to analyze their properties, such as MLR frequency spacing, QP modulation period, and QP intensity as functions of geomagnetic activity and solar wind parameters. Altogether, 1,152 MLR events and 2,172 QP emissions were analyzed. It is shown that the influence of the analyzed parameters on QP emissions is different for QP events with modulation periods shorter/longer than 20 s. While the properties of QP events with long modulation periods are significantly related to the geomagnetic activity and solar wind parameters, no such dependences are observed for events with short modulation periods. This suggests that there might be two types of QP emissions generated by two different mechanisms. It is further shown that there seems to be no relation between the properties of QP and MLR events observed at the same times. Finally, the event properties do not seem to be related to the whistler occurrence rate. Key Points: Dependences obtained for quasiperiodic emissions with short/long modulation periods are differentProperties of quasiperiodic emissions and magnetospheric line radiation observed at the same times are not relatedEvent properties are not affected by the whistler occurrence [ABSTRACT FROM AUTHOR]

Cosmic Ray Albedo Neutron Decay (CRAND) has been recently confirmed as a source of energetic electrons at the inner edge of the inner belt by the Colorado Student Space Weather Experiment (CSSWE) mission. Here we use observations from the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) mission, to investigate the CRAND contribution to inner belt electrons quantitatively over a broad energy range (~100–800 keV). Spectral fitting analysis supports the conclusion that CRAND is the most important electron source at the inner edge of the inner belt. For the first time, we show that CRAND is the dominant source of >250‐keV quasitrapped electrons throughout the inner belt and slot region during quiet times. We suggest that additional sources for <250‐keV electrons exist, perhaps from inward transport. In contrast, dynamics of electrons in the inner belt and slot region is dominated by injections during active times. Plain Language Summary: Albedo neutrons are produced when cosmic ray particles (energetic protons and alpha particles) enter the Earth's atmosphere and then decay into protons, electrons, and antineutrinos, which is known as the Cosmic Ray Albedo Neutron Decay (CRAND) process. The produced energetic protons fill up the inner proton radiation belt, but the CRAND‐produced electrons were not expected to be an important source of the electron belts until measurements from the Colorado Student Space Weather Experiment (CSSWE) mission recently showed that 500‐keV electrons at the inner edge of the inner belt are produced by CRAND. This study uses measurements from the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) mission and analyze the electron energy spectrum over a broad energy range (~100–800 keV), combining the theoretical calculation of the energy spectrum of CRAND‐produced electrons, to confirm CRAND is the dominant electron source at the inner edge of the inner belt. Furthermore, we show that CRAND is also an important source of >250‐keV quasitrapped electrons (freshly produced ones) in the inner belt and slot region during quiet times. This study discusses the CRAND contribution to the radiation belt electrons and shows that with the knowledge of this new electron source, some other physics processes, such as pitch angle scattering, need to be revisited and quantified. Key Points: CRAND‐produced electrons are identified unequivocally by both CSSWE and DEMETER at the inner edge of the inner beltThe electron source at low L, where no trapped electrons exist, is validated to be CRAND through a study of energy spectraDuring quiet times, CRAND is the dominant source of >250‐keV quasitrapped electrons for the entire inner belt and slot region [ABSTRACT FROM AUTHOR]

Frequency‐time spectrograms measured by the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft (2004–2010, altitude about 700 km) at frequencies below 20 kHz sometimes contain lightning‐generated whistlers whose intensity is significantly reduced at specific frequencies. The frequencies of the reduced intensity vary smoothly over the event duration, forming apparent curves in frequency‐time spectrograms. Events at frequencies higher than the Earth‐ionosphere waveguide cutoff frequency were explained by the interference of the first few waveguide modes of lightning‐generated spherics propagating therein (Záhlava et al., 2015, https://doi.org/10.1002/2015JA021607. Here we present an analysis of events observed at frequencies lower than about 1 kHz. Altogether, we analyze 263 events identified at the times when DEMETER operated in the burst mode. The vast majority of the events (95%) took place during the nighttime, and they occurred more frequently during spring/autumn than during winter/summer. We present an overview of event properties. Moreover, measurements of all six electromagnetic field components performed by DEMETER allow us to perform a detailed wave analysis. It is shown that the emissions propagate with high wave normal angles inclined toward the Earth. We suggest that the events might be due to the wave propagation in the ionospheric waveguide formed around the refractive index maximum at the altitude of about 105 km. Key Points: We analyze ELF events formed by lightning‐generated whistlers with intensity significantly reduced at specific frequenciesWe perform a study of 263 events identified in the DEMETER spacecraft data, including their detailed wave analysisWe suggest that the events might be created in the waveguide formed around the refractive index maximum in the lower ionosphere [ABSTRACT FROM AUTHOR]

U‐shaped spectrograms observed by the DEMETER satellite in the equatorial region of the upper ionosphere are presented and explained for the first time. These spectra are characterized by the latitude‐dependent upper cutoff frequency that increases with the latitude during nighttime. The observations suggest that this very low frequency wave phenomenon is closely connected with the anomalous increase in cold plasma density at and below the satellite. We show that restricting the analysis to propagation effects is insufficient to explain U‐shaped spectra, and other effects, in particular, the collisional wave damping should be taken into consideration. To calculate the wave damping, we use the method of successive approximations. In the first approximation, we calculate the ray trajectory and the wave normal vector along it, using the equations of geometrical optics neglecting collisions. In the second approximation we calculate the collisional wave damping along the precalculated trajectory. We show that the effects of very low frequency wave propagation and attenuation in the equatorial region of the upper ionosphere explain the main features of the phenomenon under discussion. Key Points: U‐shaped spectrum registered in the equatorial region of the upper ionosphere during nighttime is formed by lightning‐induced whistler wavesLatitudinal dependence of the upper cutoff frequency is determined by the peculiarities of oblique wave propagation and attenuationThe wave attenuation can be calculated along the trajectories found from the equations of geometrical optics that disregard collisions [ABSTRACT FROM AUTHOR]

We use the measurements performed by the DEMETER (2004–010) and the Van Allen Probes (2012–016, still operating) spacecraft to investigate the longitudinal dependence of the intensity of whistler mode waves in the Earth's inner magnetosphere. We show that a significant longitudinal dependence is observed inside the plasmasphere on the nightside, primarily in the frequency range 400 Hz to 2 kHz. On the other hand, almost no longitudinal dependence is observed on the dayside. The obtained results are compared to the lightning occurrence rate provided by the Optical Transient Detector/Lightning Imaging Sensor mission normalized by a factor accounting for the ionospheric attenuation. The agreement between the two dependencies indicates that lightning‐generated electromagnetic waves may be responsible for of the observed effect, thus substantially affecting the overall wave intensity in the given frequency range. Finally, we show that the longitudinal dependence is most pronounced for waves with oblique wave of normal angles. Key Points: Longitudinal dependence of whistler mode waves in the inner magnetosphere is investigatedSignificant longitudinal dependence at frequencies between about 0.4 and 2 kHz is found inside the plasmasphereThe dependence is primarily observed on the nightside and is likely related to lightning activity [ABSTRACT FROM AUTHOR]

Abstract: We investigate the influence of lightning‐generated whistlers on the overall intensity of electromagnetic waves measured by the Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions spacecraft (2004–2010, quasi Sun‐synchronous polar orbit with an altitude of about 700 km) at frequencies below 18 kHz. Whistler occurrence rate evaluated using an onboard neural network designed for automated whistler detection is used to distinguish periods of high and low whistler occurrence rates. It is shown that especially during the night and particularly in the frequency‐geomagnetic latitude intervals with a low average wave intensity, contribution of lightning‐generated whistlers to the overall wave intensity is significant. At frequencies below 1 kHz, where all six electromagnetic wave components were measured during specific intervals, the study is accompanied by analysis of wave propagation directions. When we limit the analysis only to fractional‐hop whistlers, which propagate away from the Earth, we find a reasonable agreement with results obtained from the whole data set. This also confirms the validity of the whistler occurrence rate analysis at higher frequencies. [ABSTRACT FROM AUTHOR]

Abstract: This paper concurrently investigates the midlatitude trough and the plasmapause positions in the ionosphere by colocated measurements of the electron density, electron temperature, and whistler count probed by DEMETER (Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions) satellite in the nighttime at 2230 LT (local time; 1900–0100 MLT, magnetic local time, mainly in the premidnight period) during the 4‐year period of 2006–2009. More than 13,000 Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions orbits of the electron density and the electron temperature are used to search the trough position, while the same amount of the whistler count is employed to determine the plasmapause position at the satellite altitude. The plasmapause is more sensitive to solar activity, which moves equatorward 1.0–1.2° form the low to high solar activity of the study period. On the other hand, the midlatitude trough is more sensitive to seasonal variation, which shifts poleward 1.7–2.5° from the winter to summer month in the study period. The midlatitude trough usually appears in the poleward side of the plasmapause during the study period. Both of the midlatitude trough and the plasmapause move equatorward during the magnetic disturbed condition. For the magnetic disturbed Kp ≥ 6−, the midlatitude trough can appear in the equatorward side of the plasmapause. [ABSTRACT FROM AUTHOR]

The transition from active growth to dormancy is critical for the survival of perennial plants. We identified a DEMETER-like ( CsDML) cDNA from a winter-enriched cDNA subtractive library in chestnut ( Castanea sativa Mill .), an economically and ecologically important species. Next, we characterized this DNA demethylase and its putative ortholog in the more experimentally tractable hybrid poplar ( Populus tremula × alba), under the signals that trigger bud dormancy in trees. We performed phylogenetic and protein sequence analysis, gene expression profiling, and 5-methyl-cytosine methylation immunodetection studies to evaluate the role of CsDML and its homolog in poplar, PtaDML6. Transgenic hybrid poplars overexpressing CsDML were produced and analysed. Short days and cold temperatures induced CsDML and PtaDML6. Overexpression of CsDML accelerated short-day-induced bud formation, specifically from Stages 1 to 0. Buds acquired a red-brown coloration earlier than wild-type plants, alongside with the up-regulation of flavonoid biosynthesis enzymes and accumulation of flavonoids in the shoot apical meristem and bud scales. Our data show that the CsDML gene induces bud formation needed for the survival of the apical meristem under the harsh conditions of winter. [ABSTRACT FROM AUTHOR]

Annual dormancy-growth cycle is a developmental and physiological process essential for the survival of deciduous trees in temperate and boreal forests. Seasonal control of shoot growth in woody perennials requires specific genetic programmes responding to environmental signals. The environmental-controlled mechanisms that regulate the shift between winter dormancy and the growth-promoting genetic programmes are still unknown. Here, we show that dynamics in genomic DNA methylation levels are involved in the regulation of dormancy-growth cycle in poplar. The reactivation of growth in the apical shoot during bud break process in spring is preceded by a progressive reduction of genomic DNA methylation in apex tissue. The induction in apex tissue of a chilling-dependent poplar DEMETER-LIKE 10 ( PtaDML10) DNA demethylase precedes shoot growth reactivation. Transgenic poplars showing downregulation of PtaDML8/10 caused delayed bud break. Genome-wide transcriptome and methylome analysis and data mining revealed that the gene targets of DEMETER-LIKE-dependent DNA demethylation are genetically associated with bud break. These data point to a chilling-dependent DEMETER-like DNA demethylase mechanisms being involved in the shift from winter dormancy to a condition that precedes shoot apical vegetative growth in poplar. [ABSTRACT FROM AUTHOR]

Quasiperiodic (QP) electromagnetic emissions are whistler mode waves at typical frequencies of a few kHz characterized by a periodic time modulation of their intensity. The DEMETER spacecraft observed events where the QP emissions exhibit a sudden change in the wave vector and Poynting vector directions. The change happens in a short interval of latitudes. We explain this behavior by ionospheric reflection and present a ray-tracing simulation which matches resulting wave vector directions. We also attempt to locate the source region of these emissions and conclude that they are most probably generated at the inner boundary of the plasmapause which also acts as a guide during the propagation of the QP emissions. [ABSTRACT FROM AUTHOR]

Electromagnetic wave data measured by the low-altitude Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft sometimes exhibit intense emissions at discrete, harmonically spaced frequencies. We present a comprehensive analysis of this type of phenomenon, and we demonstrate that it is caused by very low frequency (VLF) transmitters in Europe. All available data were investigated for a possible presence of the events. Altogether, 87 events were identified, occurring exclusively during the nighttime. The occurrence of the events does not show any clear relation to the A E and D s t geomagnetic activity indices. The events are clearly localized, occurring either close to Great Britain or in the vicinity of its geomagnetically conjugated region. The frequency spectra of the events typically consist of up to four spectral peaks at multiples of about 1.3 kHz. Additional weaker spectral peaks at frequencies of about 1.9 kHz and 3.2 kHz are occasionally present. The events observed in the Northern Hemisphere tend to have larger-frequency bandwidths than the events observed in the Southern Hemisphere. The occurrence of these events is correlated with the simultaneous detection of signals from VLF transmitters. A bicoherence analysis is employed to demonstrate that wave-wave coupling takes place. Finally, it is shown that the occurrence of the events is associated with a significantly increased precipitation of energetic electrons in a wide range of energies. [ABSTRACT FROM AUTHOR]

Parental genomes in the endosperm are marked by differential DNA methylation and are therefore epigenetically distinct. This epigenetic asymmetry is established in the gametes and maintained after fertilization by unknown mechanisms. In this manuscript, we have addressed the key question whether parentally inherited differential DNA methylation affects de novo targeting of chromatin modifiers in the early endosperm. Our data reveal that polycomb-mediated H3 lysine 27 trimethylation (H3K27me3) is preferentially localized to regions that are targeted by the DNA glycosylase DEMETER ( DME), mechanistically linking DNA hypomethylation to imprinted gene expression. Our data furthermore suggest an absence of de novo DNA methylation in the early endosperm, providing an explanation how DME-mediated hypomethylation of the maternal genome is maintained after fertilization. Lastly, we show that paternal-specific H3K27me3-marked regions are located at pericentromeric regions, suggesting that H3K27me3 and DNA methylation are not necessarily exclusive marks at pericentromeric regions in the endosperm. [ABSTRACT FROM AUTHOR]

Simulation models are widely employed to make probability forecasts of future conditions on seasonal to annual lead times. Added value in such forecasts is reflected in the information they add, either to purely empirical statistical models or to simpler simulation models. An evaluation of seasonal probability forecasts from the Development of a European Multimodel Ensemble system for seasonal to inTERannual prediction (DEMETER) and ENSEMBLES multi-model ensemble experiments is presented. Two particular regions are considered: Nino3.4 in the Pacific and the Main Development Region in the Atlantic; these regions were chosen before any spatial distribution of skill was examined. The ENSEMBLES models are found to have skill against the climatological distribution on seasonal time-scales. For models in ENSEMBLES that have a clearly defined predecessor model in DEMETER, the improvement from DEMETER to ENSEMBLES is discussed. Due to the long lead times of the forecasts and the evolution of observation technology, the forecast-outcome archive for seasonal forecast evaluation is small; arguably, evaluation data for seasonal forecasting will always be precious. Issues of information contamination from in-sample evaluation are discussed and impacts (both positive and negative) of variations in cross-validation protocol are demonstrated. Other difficulties due to the small forecast-outcome archive are identified. The claim that the multi-model ensemble provides a 'better' probability forecast than the best single model is examined and challenged. Significant forecast information beyond the climatological distribution is also demonstrated in a persistence probability forecast. The ENSEMBLES probability forecasts add significantly more information to empirical probability forecasts on seasonal time-scales than on decadal scales. Current operational forecasts might be enhanced by melding information from both simulation models and empirical models. Simulation models based on physical principles are sometimes expected, in principle, to outperform empirical models; direct comparison of their forecast skill provides information on progress toward that goal. [ABSTRACT FROM AUTHOR]

Effective statistical downscaling schemes based on singular value decomposition (SVD) for boreal autumn (September-October-November) precipitation over China were developed. It was found that rainfall over China is closely tied to large-scale atmospheric and oceanic circulation over specific regions. The general circulation models (GCMs), which are from DEMETER project (Development of a European Multi-model Ensemble System for Seasonal to Interannual Prediction), perform reasonably well in simulating the mean states of geopotential height at 500 hPa (GH5) during autumns from 1960 to 2001. Consequently, the variable GH5 over East Asia from DEMETER GCMs was used as one predictor for downscaling. Meanwhile, another predictor is the preceding sea surface temperature (SST) signal from observed data over the tropical Pacific. The downscaling results involving only the GH5 predictor (GH5 scheme) or both the GH5 and SST predictors (GH5 + SST scheme) were discussed and compared in this study. Downscaling based on two kinds of schemes showed considerable improvement compared with original DEMETER GCMs in predicting regional autumn precipitation. In particular, downscaling predictions based on the GH5 + SST scheme showed lower root mean square errors than those based on the GH5 scheme, especially for the precipitation anomaly pattern of the El Niño event in 1997 and the La Niña event in 1998. Copyright © 2012 Royal Meteorological Society [ABSTRACT FROM AUTHOR]

Imprinting, i.e. parent-of-origin expression of alleles, plays an important role in regulating development in mammals and plants. DNA methylation catalyzed by DNA methyltransferases plays a pivotal role in regulating imprinting by silencing parental alleles. DEMETER (DME), a DNA glycosylase functioning in the base-excision DNA repair pathway, can excise 5-methylcytosine from DNA and regulate genomic imprinting in Arabidopsis. DME demethylates the maternal MEDEA ( MEA) promoter in endosperm, resulting in expression of the maternal MEA allele. However, it is not known whether DME interacts with other proteins in regulating gene imprinting. Here we report the identification of histone H1.2 as a DME-interacting protein in a yeast two-hybrid screen, and confirmation of their interaction by the in vitro pull-down assay. Genetic analysis of the loss-of-function histone h1 mutant showed that the maternal histone H1 allele is required for DME regulation of MEA, FWA and FIS2 imprinting in Arabidopsis endosperm but the paternal allele is dispensable. Furthermore, we show that mutations in histone H1 result in an increase of DNA methylation in the maternal MEA and FWA promoter in endosperm. Our results suggest that histone H1 is involved in DME-mediated DNA methylation and gene regulation at imprinted loci. [ABSTRACT FROM AUTHOR]

On the basis of the observed all-India rainfall (AIR), Climate Prediction Center (CPC) merged analysis of precipitation (CMAP), and the multimodel rainfall simulated in the Development of a European multimodel ensemble system for seasonal to interannual prediction (DEMETER) project, the model performance in terms of forecast quality of the seasonal mean Indian summer monsoon rainfall (ISMR) was evaluated. The approach used included the individual model (single-model ensemble) comparison as well as its comparison with the multimodel ensemble (MME). The results obtained reveal that systematic biases are the main source of the low skill in predicting the ISMR, while improved reproduction of interannual variability may increase the overall forecast quality for the ISMR. The MME shows superior performance in reproducing AIR features than the single-model ensembles. This improved forecast quality achieved by the MME with respect to the ISMR variations primarily depends on model performance and secondly on ensemble size. The MME has improved capability of simulating the ISMR variations during 1972-1990 decades, whereas it exhibits a lower performance in the 1990s. The reason of this decadal varying forecast quality clearly deserves more investigation. In summary, these results suggest that the MME's increase in skill absolutely depends on enhancing the individual model quality. Copyright © 2011 Royal Meteorological Society [ABSTRACT FROM AUTHOR]