Energetic Electron Precipitation Research Articles

Mesospheric ionization during substorm growth phase

Many studies have been conducted about the impact of energetic charged particles on the atmosphere during geomagnetically active times, while quiet time effects are poorly understood. We identified two energetic electron precipitation (EEP) events during the growth phase of moderate substorms and estimated the mesospheric ionization rate for an EEP event for which the most comprehensive dataset from ground-based and space-born instruments was available. The mesospheric ionization signature reached below 70 km altitude and continued for ~15 min until the substorm onset, as observed by the PANSY radar and imaging riometer at Syowa Station in the Antarctic region. We also used energetic electron flux observed by the Arase and POES 15 satellites as the input for the air-shower simulation code PHITS to quantitatively estimate the mesospheric ionization rate. The calculated ionization level due to the precipitating electrons is consistent with the observed value of cosmic noise absorption. The possible spatial extent of EEP is estimated to be ~8 h MLT in longitude and ~1.5° in latitude from a global magnetohydrodynamic simulation REPPU and the precipitating electron observations by the POES satellite, respectively. Such a significant duration and spatial extent of EEP events suggest a non-negligible contribution of the growth phase EEP to the mesospheric ionization. Combining the cutting-edge observations and simulations, we shed new light on the space weather impact of the EEP events during geomagnetically quiet times, which is important to understand the possible link between the space environment and climate.

Modeling of Diffuse Auroral Emission at Mars: Contribution of MeV Protons

AbstractThe Solar Energetic Particle and imaging ultraviolet spectrograph (IUVS) instruments onboard the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft discovered diffuse aurora that span across the nightside of Mars due to the interaction of solar energetic particles (SEPs) with the Martian atmosphere. However, it is unclear whether the diffuse aurora originates from energetic electrons or protons. We have developed a Monte Carlo model to calculate the limb intensity profile of the CO2+ ultraviolet doublet (UVD) due to precipitation of energetic electrons and protons with energy ranges from 100 eV to 100 keV and from 50 keV to 5 MeV, respectively. We used electron and proton fluxes observed by MAVEN during the December 2014 SEP event and the September 2017 SEP event. Our results showed that proton‐induced CO2+ UVD emission has a lower peak altitude than electron‐induced CO2+ UVD emission. The calculated peak altitudes of the CO2+ UVD limb profiles are 76 and 68 km in the December 2014 event and the September 2017 event, respectively. Extending the energy to 500 keV for electrons and 20 MeV for protons further improved our comparison to the IUVS observations. We have succeeded in reproducing peak altitudes and shapes of the observed CO2+ UVD limb profiles using the SEP flux observed by MAVEN. This was possible by taking into account the contribution of energetic protons, indicating that both energetic electrons and protons contribute to producing the observed diffuse aurora.

Energetic Electron Precipitation Induced by Oblique Whistler Mode Chorus Emissions

AbstractEnergetic electron acceleration and precipitation in the Earth's outer radiation belt are highly associated with wave‐particle interactions between whistler mode chorus waves and electrons. We perform test particle simulations to investigate electrons interacting with parallel and oblique chorus emissions with maximum amplitude 2.1 nT and 370 pT at L = 4.5. We build up a database of Green's functions, which are treated as results of the input electrons interacting with one chorus emission. The loss process of electrons caused by consecutive chorus emissions in the outer radiation belt are traced by applying the convolution integrals of distribution functions and the Green's functions. Oblique chorus emissions lead to more electron precipitation than parallel chorus emissions in the range 370 pT–2.1 nT. By checking the resonance condition and resonant energies, we find that electrons are difficult to be scattered into the loss cone directly by Landau resonance. We propose a two‐step precipitation process for oblique chorus emissions that contributes to more electron loss: (a) Through Landau resonance interaction with a chorus emission, electrons at high pitch angles are effectively accelerated in the parallel direction, and their pitch angles become lower. (b) The electrons bounce back toward the equator, and they are pushed into loss cone through nonlinear scattering due to cyclotron resonance with another chorus emission. The combination of Landau resonance and cyclotron resonance by oblique chorus emissions results in a higher precipitation rate than the single cyclotron resonance by purely parallel chorus emissions.

Energetic Electron Precipitation Driven by the Combined Effect of ULF, EMIC, and Whistler Waves

AbstractEnergetic electron losses in the Earth's inner magnetosphere are dominated by outward radial diffusion and scattering into the atmosphere by various electromagnetic waves. The two most important wave modes responsible for electron scattering are electromagnetic ion cyclotron (EMIC) waves and whistler‐mode waves (whistler waves) that, acting together, can provide rapid electron losses over a wide energy range from few keV to few MeV. Wave‐particle resonant interaction resulting in electron scattering is well described by quasi‐linear diffusion theory using the cold plasma dispersion, whereas the effects of nonlinear resonances and hot plasma dispersion are less well understood. This study aims to examine these effects and estimate their significance for a particular event during which both wave modes are quasi‐periodically modulated by ultra‐low‐frequency (ULF) compressional waves. Such modulation of EMIC and whistler wave amplitudes provides a unique opportunity to compare nonlinear resonant scattering (important for the most intense waves) with quasi‐linear diffusion (dominant for low‐intensity waves). The same modulation of plasma properties allows better characterization of hot plasma effects on the EMIC wave dispersion. Although hot plasma effects significantly increase the minimum resonant energy, Emin, for the most intense EMIC waves, such effects become negligible for the higher frequency part of the hydrogen‐band EMIC wave spectrum. Nonlinear phase trapping of 300–500 keV electrons through resonances with whistler waves may accelerate and make them resonant with EMIC waves that, in turn, quickly scatter those electrons into the loss‐cone. Our results highlight the importance of nonlinear effects for simulations of energetic electron fluxes in the inner magnetosphere.

Early-Time Non-Equilibrium Pitch Angle Diffusion of Electrons by Whistler-Mode Hiss in a Plasmaspheric Plume Associated with BARREL Precipitation

In August 2015, the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) observed precipitation of energetic (<200 keV) electrons magnetically conjugate to a region of dense cold plasma as measured by the twin Van Allen Probes spacecraft. The two spacecraft passed through the high density region during multiple orbits, showing that the structure was spatial and relatively stable over many hours. The region, identified as a plasmaspheric plume, was filled with intense hiss-like plasma waves. We use a quasi-linear diffusion model to investigate plume whistler-mode hiss waves as the cause of precipitation observed by BARREL. The model input parameters are based on the observed wave, plasma and energetic particle properties obtained from Van Allen Probes. Diffusion coefficients are found to be largest in the same energy range as the precipitation observed by BARREL, indicating that the plume hiss waves were responsible for the precipitation. The event-driven pitch angle diffusion simulation is also used to investigate the evolution of the electron phase space density (PSD) for different energies and assumed initial pitch angle distributions. The results show a complex temporal evolution of the phase space density, with periods of both growth and loss. The earliest dynamics, within the ∼5 first minutes, can be controlled by a growth of the PSD near the loss cone (by a factor up to ∼2, depending on the conditions, pitch angle, and energy), favored by the absence of a gradient at the loss cone and by the gradients of the initial pitch angle distribution. Global loss by 1-3 orders of magnitude (depending on the energy) occurs within the first ∼100 min of wave-particle interaction. The prevalence of plasmaspheric plumes and detached plasma regions suggests whistler-mode hiss waves could be an important driver of electron loss even at high L-value (L ∼6), outside of the main plasmasphere.

Multi‐Point Observations of Modulated Whistler‐Mode Waves and Energetic Electron Precipitation

AbstractIn this study, we present simultaneous multi‐point observations of whistler‐mode waves detected by RBSP‐B, associated with conjugate electron precipitation observed through enhanced BARREL X‐rays at L ∼ 6 from noon to dusk. Both long period modulation at periods of several to tens of minutes and short period modulation at about tens of seconds are observed in X‐ray measurements. Similar periodicities are also observed for whistler‐mode wave amplitude. We show that the correlation coefficient between whistler‐mode waves and electron precipitation is high in several regions, including plumes and plasma trough. Ultra‐low‐frequency waves (8–30 mHz), which have been suggested to play a potential role in precipitating electrons by modulating whistler‐mode wave intensity or loss cone size, show a weak correlation with whistler‐mode wave amplitudes and the X‐ray counts during the conjunction. We further evaluate whistler‐mode wave driven electron precipitation using a physics‐based technique. The time evolution of the modeled electron precipitation is found to be remarkably consistent with the modulation in the BARREL X‐ray counts both in plumes and plasma trough. By taking advantage of the high‐resolution wave data and close conjunction, we provide strong evidence that whistler‐mode waves are not only directly responsible for the longer modulation (several to tens of minutes), but also the shorter modulation (tens of seconds) of the electron precipitation.

Study of Substorm‐Related Auroral Absorption: Latitudinal Width and Factors Affecting the Peak Intensity of Energetic Electron Precipitation

AbstractPreviously, suggesting a scenario of “injected and drifting electron cloud” to describe the enhancements and precipitations of energetic electrons during substorms we used the linear prediction filter (LPF) method to build the empirical dynamical model of auroral absorption in the middle of auroral zone, driven by the midlatitude positive bay (MPB) index time series. In this paper, to understand better the relationship between magnetic dipolarization, injection, and energetic electron precipitation, we quantitatively explore correlations between dipolarization proxies (MPB and SML indices, substorm current wedge (SCW) intensity, location, and size) and precipitation‐related auroral absorption in the morning maximum region for 148 isolated substorms. We confirm good correlation of precipitation peak values with dipolarization proxies and show that the absorption amplitude is most strongly controlled by total SCW current and its azimuthal size, and is also influenced by solar wind‐dependent background energetic electron flux in the conjugate plasma sheet. This result confirms the adequacy of our starting assumption that there is a close relationship between the intensities and size of substorm dipolarizations and energetic particle injections. To extend the latitudinal coverage, we computed the LPF response functions for individual riometers of NORSTAR array. Finding similar shapes and amplitudes of their response at latitudes 63°–69° in the regions where maximal precipitation is statistically observed, we suggest, test, and approve that the auroral absorption in the belt 63°–69° may be predicted using a set of LPFs determined empirically in the center of auroral zone for various magnetic local times.

A New MEPED‐Based Precipitating Electron Data Set

The work presented here introduces a new data set for inclusion of energetic electron precipitation (EEP) in climate model simulations. Measurements made by the medium energy proton and electron detector (MEPED) instruments onboard both the Polar Orbiting Environmental Satellites and the European Space Agency Meteorological Operational satellites are used to create global maps of precipitating electron fluxes. Unlike most previous data sets, the electron fluxes are computed using both the 0° and 90° MEPED detectors. Conversion of observed, broadband electron count rates to differential spectral fluxes uses a linear combination of analytical functions instead of a single function. Two dimensional maps of electron spectral flux are created using Delaunay triangulation to account for the relatively sparse nature of the MEPED sampling. This improves on previous studies that use a 1D interpolation over magnetic local time or L‐shell zonal averaging of the MEPED data. A Whole Atmosphere Community Climate Model (WACCM) simulation of the southern hemisphere 2003 winter using the new precipitating electron data set is shown to agree more closely with observations of odd nitrogen than WACCM simulations using other MEPED‐based electron data sets. Simulated EEP‐induced odd nitrogen increases led to ozone losses of more than 15% in the polar stratosphere near 10 hPa in September of 2003.

Statistical Study of Electron Density Enhancements in the Ionospheric F Region Associated With Pulsating Auroras

AbstractPulsating auroras (PsAs) are considered to be caused by energetic (>a few keV) electron precipitation. Additionally, soft electron precipitation (<a few keV) has often been observed in PsAs. This soft electron precipitation enhances the electron density in the ionospheric F region. However, to date, the relationship between PsAs and soft electron precipitation has not been well understood. In this study, using the data taken by the European incoherent scatter radar and the auroral all‐sky imager at Tromsø, we conducted two case studies to investigate, in detail, the relationship between the electron density height profile and the type of aurora. Additionally, we conducted statistical studies for 14 events to elucidate how often F region electron density enhancement occurs with a PsA. We consequently found that 76% of electron density height profiles showed a local peak in the F region, with electron temperature enhancements. It was also found that 89% of the F region peak altitudes were above the peak altitude of the ionization rate produced by electrons of characteristic energy below 100 eV. The occurrence rate of these profiles in the hourly magnetic local time (MLT) exceeded 80% in the 22–3 MLT sectors. We suggest that the electron density enhancement in the F region would have been caused by electrostatic electron cyclotron harmonic waves in the magnetosphere. Another candidate would have been polar patches that had traveled from the dayside ionosphere.

Stratospheric X‐Rays Detected at Midlatitudes With a Miniaturized Balloon‐Borne Microscintillator‐PiN Diode System

AbstractA miniaturized scintillator (“microscintillator”), was flown on a meteorological radiosonde to observe energetic particles in the lower atmosphere. A PiN diode was used to measure the light from the microscintillator to count rates and energies of ionizing radiation from the ground up to the stratosphere (32 km). The flight, over the southern UK on August 27, 2018, occurred during a geomagnetic storm. Low‐energy (50–150 keV) particles in the stratosphere were detected in addition to the usual signal from higher‐energy cosmic rays. Unusually for these miniaturized radiosonde systems, which are designed to be disposable, the payload was retrieved. This allowed for re‐calibration of the microscintillator, which confirmed the low‐energy particle detection. Laboratory tests excluded thermal effects on the microscintillator instrument as the origin of the signal. Data from the NOAA POES spacecraft offer the explanation that the microscintillator detected bremstrahhlung X‐rays from energetic electron precipitation (EEP). EEP events may affect weather and climate through a range of physical mechanisms, and this midlatitude observation, well away from the auroral oval, extends the region over which meteorological effects of EEPs need to be assessed. Our findings underline the value of balloon measurements in providing rapid response to space weather events. The energy‐discriminating and altitude‐sensitive capability of the microscintillator augments spacecraft observations from below.

Atmospheric Effects during the Precipitation of Energetic Electrons

Atmospheric Effects during the Precipitation of Energetic Electrons

Energetic electron precipitation during lightning activities over Indian landmass as observed from WWLLN and NOAA-15 satellite

Lightning is a sudden release of electrostatic energy that plays a significant role in the ionospheric-magnetospheric coupling process. A short-term increase in the particle count rates (CR) in the Van Allen Radiation Belt (VAB) is known as the particle bursts. Due to lightning events, the increase in the number of high-energy particles in the inner region of the VAB (L < 2) is a fascinating research to implement. This paper tries to determine the number of lightning-induced particles, which can successfully establish a connection between the two regions of the atmosphere (the ionosphere and the magnetosphere). Lightning-generated electromagnetic radiation propagates through the Earth Ionosphere Waveguide (EIWG), where some energy leaks through and scatters particles in the radiation belt. By lowering the pitch angle, some particles precipitate into the ionosphere and cause secondary ionization. This excess particle count caused by lightning strokes is detected using data from the NOAA-15 satellite and data from the World Wide Lightning Location Network (WWLLN) is used to verify the relationship between lightning stroke and particle count. In this paper, we process our work by using lightning locations over a specific region of India and the geographic/geomagnetic conjugate locations. The monthly variation shows a high correlation between the lightning stroke number and the particle counts within the conjugate geomagnetic location, while the correlation with the particle counts within the conjugate geographic location is significantly lower. In the second half of the paper, we use an automated energy filtration method, for the computation of the particle counts induced by maximum energetic lightning (having lightning energy value > 10 4 J and the particle counts induced by minimum energetic lightning (having lightning energy value < 10 4 J). The results of this analysis demonstrate that the variation of PCs in the conjugate geomagnetic location is more closely related to the maximum energetic lightning variation than the lowest energetic lighting variation. This paper will demonstrate the coupling process between the ionosphere and the magnetosphere based on counting the particles produced by lightning.

Electron Lifetimes and Diffusion Rates Inferred From ELFIN Measurements at Low Altitude: First Results

AbstractIn the radiation belts, energetic and relativistic electron precipitation into the atmosphere is expected to be mainly controlled over the long term by quasilinear pitch‐angle scattering by whistler‐mode and electromagnetic ion cyclotron waves. Accordingly, statistical electron lifetimes have been derived from quasilinear diffusion theory on the basis of multi‐year wave statistics. However, the full consistency of such statistical quasilinear models of electron lifetimes with both measured electron lifetimes, spectra of trapped and precipitated electron fluxes, and wave‐driven diffusion rates inferred from electron flux measurements, has not yet been verified in detail. In the present study, we use data from Electron Loss and Fields Investigation (ELFIN) mission CubeSats, launched in September 2018 in low Earth orbit, to carry out such comparisons between quasi‐linear diffusion theory and observed electron flux variations. We show that statistical theoretical lifetime models are in reasonable agreement with electron pitch‐angle diffusion rates inferred from the precipitated to trapped 100 keV electron flux ratio measured by ELFIN after correction for atmospheric backscatter, as well as with timescales of trapped electron flux decay independently measured over several days by ELFIN. The present results demonstrate for the first time a broad consistency between timescales of trapped electron flux decay, the pitch‐angle distribution of precipitated electrons, and quasilinear models of wave‐driven electron loss, showing the reliability of such statistical electron lifetime models parameterized by geomagnetic activity for evaluating electron precipitation into the atmosphere during not too disturbed periods.

Space–Time Structure of Energetic Electron Precipitations according to the Data of Balloon Observations and Polar Satellite Measurements on February 1–6, 2015

Space–Time Structure of Energetic Electron Precipitations according to the Data of Balloon Observations and Polar Satellite Measurements on February 1–6, 2015

Frequency‐Dependent Responses of Plasmaspheric Hiss to the Impact of an Interplanetary Shock

AbstractPlasmaspheric hiss waves are essential for the pitch‐angle scattering and precipitation of energetic electrons and interplanetary shocks may affect these waves. We present a case study on the responses of plasmaspheric hiss after an interplanetary shock arrival on September 7, 2017. Based on the observation by RBSP‐B, the plasmaspheric hiss in different frequency ranges shows three different responses simultaneously: hiss waves with frequency below 0.08fce are weakened, waves within 0.08–0.18fce are weakened in magnetic power and modulated by the ultra‐low frequency (ULF) waves in the electric power, while waves above 0.18fce are intensified in magnetic power and modulated by the ULF waves. Further analysis suggests that the hiss waves have different sources: low‐frequency (&lt;∼0.18fce) hiss waves are transmitted from chorus outside the plasmasphere, while high‐frequency (&gt;∼0.18fce) hiss waves are locally amplified. Our results provide a comprehensive view of the frequency‐dependent hiss wave behavior after the impact of interplanetary shocks.

Ionization in the Earth’s Atmosphere Due to Isotropic Energetic Electron Precipitation: Ion Production and Primary Electron Spectra

Energetic electron precipitation (EEP) via atmospheric ion production rates is a natural force acting on the atmosphere and climate systems. The correct estimation of EEP ion production and spectra for the computation of ionization rates is an important issue for estimating climate forces. In the present paper, we propose a favorable method for the computation of ionization rates forced by EEP using the new parameterization of ion production and a new spectrum shape, which allow one to take into account the range of precipitating particles from tens of keV to several MeV. A new function of spectral fit will also be helpful in obtaining information about EEP from satellite and balloon observations. Presented here, the parameterization of atmospheric ionization in the Earth’s atmosphere includes a new yield function of isotropically precipitating monoenergetic electrons and ionization via Bremsstrahlung radiation. Look-up tables with ion production/yield function for isotropically precipitating monoenergetic electrons (30 keV–5 MeV) can be easily used for the computation of ionization rates and can further be used by atmospheric and chemistry-climate models for accurate quantification of atmospheric parameters during energetic electron precipitation.

Simulated seasonal impact on middle atmospheric ozone from high-energy electron precipitation related to pulsating aurorae

Abstract. Recent simulation studies have provided evidence that a pulsating aurora (PsA) associated with high-energy electron precipitation is having a clear local impact on ozone chemistry in the polar middle mesosphere. However, it is not clear if the PsA is frequent enough to cause longer-term effects of measurable magnitude. There is also an open question of the relative contribution of PsA-related energetic electron precipitation (PsA EEP) to the total atmospheric forcing by solar energetic particle precipitation (EPP). Here we investigate the PsA-EEP impact on stratospheric and mesospheric odd hydrogen, odd nitrogen, and ozone concentrations. We make use of the Whole Atmosphere Community Climate Model and recent understanding on PsA frequency, latitudinal and magnetic local time extent, and energy-flux spectra. Analysing an 18-month time period covering all seasons, we particularly look at PsA-EEP impacts at two polar observation stations located at opposite hemispheres: Tromsø in the Northern Hemisphere (NH) and Halley Research Station in the Southern Hemisphere (SH). We find that PsA EEP can have a measurable impact on ozone concentration above 30 km altitude, with ozone depletion by up to 8 % seen in winter periods due to PsA-EEP-driven NOx enhancement. We also find that direct mesospheric NOx production by high-energy electrons (E&gt; 100 keV) accounts for about half of the PsA-EEP-driven upper stratospheric ozone depletion. A larger PsA-EEP impact is seen in the SH where the background dynamical variability is weaker than in the NH. Clearly indicated from our results, consideration of polar vortex dynamics is required to understand PsA-EEP impacts seen at ground observation stations, especially in the NH. We conclude that PsA-EEP has the potential to make an important contribution to the total EPP forcing; thus, it should be considered in atmospheric and climate simulations.

Quantification of Diffuse Auroral Electron Precipitation Driven by Whistler Mode Waves at Jupiter

AbstractWhile previous studies suggested whistler mode waves as a potential driver of Jupiter's diffuse aurora, their quantitative contribution to generate diffuse aurora remains unclear. We perform an in‐depth analysis of an intriguing diffuse auroral electron precipitation event using coordinated observations of precipitating electrons and whistler mode waves from the Juno satellite. A physics‐based technique is used to quantify energetic electron precipitation driven by whistler mode waves. We find that the modeled electron precipitation features are consistent with the electron measurements from several keV to several hundred keV over M‐shells of 8–18, while additional mechanisms are needed to explain the observed electron precipitation at lower energies (&lt;several keV). Our result provides new quantitative evidence that whistler mode waves are potentially a primary driver of precipitating electrons from several keV to several hundred keV through pitch angle scattering over M ∼ 8–18 and thus generate Jupiter's diffuse aurora.

The Predictive Capabilities of the Auroral Electrojet Index for Medium Energy Electron Precipitation

The chemical imprint of the energetic electron precipitation on the atmosphere is now acknowledged as a part of the natural forcing of the climate system. It has, however, been questioned to which degree current proxies are able to quantify the medium energy electron (MEE) (≳30 keV) precipitation and the associated daily and decadal variability. It is particularly challenging to model the high energy tail (≳300 keV) of MEE, both in terms of the intensity as well as the timing. This study explores the predictive capabilities of the AE index for the MEE precipitation. MEE measurements from the NOAA/POES over a full solar cycle from 2004 to 2014 are applied. We combine observations from the MEPED 0° and 90° detectors together with theory of pitch angle diffusion by wave-particle interaction to estimate the precipitating fluxes. To explore the energy dependent time scales, each of the MEPED energy channels, &amp;gt; 43, &amp;gt;114, and &amp;gt;292 keV are evaluated independently. While there is a strong correlation between the daily resolved AE index and &amp;gt;43 keV fluxes, it is a poor predictor for the &amp;gt;292 keV fluxes. We create new AE based MEE proxies by accumulating the AE activity over multiple days, including terms counting for the associated lifetimes. The results indicate that AE based proxies can predict at least 70% of the observed MEE precipitation variance at all energies. The potential link between the AE index, substorms and the MEE precipitation is discussed.

Solar Cycle-Modulated Deformation of the Earth–Ionosphere Cavity

The Earth–ionosphere cavity resonator is occupied primarily by the electromagnetic radiation of lightning below 100 Hz. The phenomenon is known as Schumann resonances (SR). SR intensity is an excellent indicator of lightning activity and its distribution on global scales. However, long-term measurements from high latitude SR stations revealed a pronounced in-phase solar cycle modulation of SR intensity seemingly contradicting optical observations of lightning from satellite, which do not show any significant solar cycle variation in the intensity and spatial distribution of lightning activity on the global scale. The solar cycle-modulated local deformation of the Earth–ionosphere cavity by the ionization of energetic electron precipitation (EEP) has been suggested as a possible phenomenon that may account for the observed long-term modulation of SR intensity. Precipitating electrons in the energy range of 1–300 keV can affect the Earth–ionosphere cavity resonator in the altitude range of about 70–110 km and modify the SR intensities. However, until now there was no direct evidence documented in the literature supporting this suggestion. In this paper we present long-term SR intensity records from eight stations, each equipped with a pair of induction coil magnetometers: five high latitude (|lat| &amp;gt; 60°), two mid-high latitude (50° &amp;lt; |lat| &amp;lt; 60°) and one low latitude (|lat| &amp;lt; 30°). These long-term, ground-based SR intensity records are compared on the annual and interannual timescales with the fluxes of precipitating 30–300 keV medium energy electrons provided by the POES NOAA-15 satellite and on the daily timescale with electron precipitation events identified using a SuperDARN radar in Antarctica. The long-term variation of the Earth–ionosphere waveguide’s effective height, as inferred from its cutoff frequency, is independently analyzed based on spectra recorded by the DEMETER satellite. It is shown that to account for all our observations one needs to consider both the effect of solar X-rays and EEP which modify the quality factor of the cavity and deform it dominantly over low- and high latitudes, respectively. Our results suggest that SR measurements should be considered as an alternative tool for collecting information about and thus monitoring changes in the ionization state of the lower ionosphere associated with EEP.