Solar Energetic Electrons Research Articles

A Rapid Sequence of Solar Energetic Particle Events Associated with a Series of Extreme-ultraviolet Jets: Solar Orbiter, STEREO-A, and Near-Earth Spacecraft Observations

A series of solar energetic electron (SEE) events was observed from 2022 November 9 to November 15 by Solar Orbiter, STEREO-A, and near-Earth spacecraft. At least 32 SEE intensity enhancements at energies >10 keV were clearly distinguishable in Solar Orbiter particle data, with 13 of them occurring on November 11. Several of these events were accompanied by ≲10 MeV proton and ≲2 MeV nucleon−1 heavy-ion intensity enhancements. By combining remote-sensing and in situ data from the three viewpoints (Solar Orbiter and STEREO-A were ∼20° and ∼15° east of Earth, respectively), we determine that the origin of this rapid succession of events was a series of brightenings and jetlike eruptions detected in extreme ultraviolet (EUV) observations from the vicinity of two active regions. We find a close association between these EUV phenomena, the occurrence of hard X-ray flares, type III radio bursts, and the release of SEEs. For the most intense events, usually associated with extended EUV jets, the distance between the site of these solar eruptions and the estimated magnetic connectivity regions of each spacecraft with the Sun did not prevent the arrival of electrons at the three locations. The capability of jets to drive coronal fronts does not necessarily imply the observation of an SEE event. Two peculiar SEE events on November 9 and 14, observed only at electron energies ≲50 keV but rich in ≲1 MeV nucleon−1 heavy ions, originated from slow-rising confined EUV emissions, for which the process resulting in energetic particle release to interplanetary space is unclear.

A Detailed Survey of the Parallel Mean Free Path of Solar Energetic Particle Protons and Electrons

In this work, more than a dozen solar energetic particle (SEP) events are identified where the source region is magnetically well connected to at least one spacecraft at 1 au. The observed intensity–time profiles, for all available proton and electron energy channels, are compared to results computed using a numerical one-dimensional SEP transport model in order to derive the parallel mean free paths (pMFPs) as a function of energy (or rigidity) at 1 au. These inversion results are then compared to theoretical estimates of the pMFP, using observed turbulence quantities with observationally motivated variations as input. For protons, a very good comparison between inversion and theoretical results is obtained. It is shown that the observed inter-event variations in the inversion pMFP values can be explained by natural variations in the background turbulence values. For electrons, there is relatively good agreement with pMFPs derived assuming the damping model of dynamical turbulence, although the theoretical values are extremely sensitive to the details of the turbulence dissipation range, which themselves display a high level of variation.

Solar Energetic Electron Access to the Moon Within the Terrestrial Magnetotail and Shadowing by the Lunar Surface

AbstractWe present measurements of 30–700 keV Solar Energetic Electrons (SEEs) near the Moon when within the terrestrial magnetotail by the Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun spacecraft. Despite their detection deep within the tail, the incident flux and spectral shape of these electrons are nearly identical to measurements taken upstream of Earth in the solar wind by the Wind spacecraft; however, their pitch angle distribution is isotropized compared to the more field‐aligned distribution upstream. We illustrate that SEEs initially traveling Earthward precipitate onto the lunar far‐side, generating extended shadows in the cis‐lunar electron distribution. By modeling the dynamics of these electrons, we show that their precipitation patterns on the lunar near‐side are comparatively reduced. The non‐uniform precipitation and accessibility of potentially hazardous electrons to the Moon's surface are highly relevant in the context of astronaut safety during the planned exploration of the lunar environment.

Solar Eruptive Phenomena Associated with Solar Energetic Electron Spectral Types

The energy spectral shape of solar energetic electron events carries important information on the energetic electron source/acceleration at the Sun. We investigate the association of six newly identified solar energetic electron spectral types with solar eruptive phenomena, including the downward double-power-law (DDPL) spectrum with break energy E B above 20 keV (DDPL EB≥20keV ), DDPL with E B below 20 keV (DDPL EB<20keV ), upward double-power law (UDPL), single-power-law (SPL), Ellision–Ramaty–like (ER), and logarithmic-parabola (LP). We find that the SPL type shows (the other five types show) an association with hard X-ray flares of ∼38% (∼55%–82%) and an association with west-limb coronal mass ejections (CMEs) of ∼76% (∼85%–93%). Among the other five types, the DDPL EB<20keV and ER (LP and DDPL EB≥20keV ) types only have an association with type II radio bursts of ∼7%–8% (∼16%–20%) and an association with halo CMEs of ∼5%–9% (∼11%–21%); however, the UDPL type exhibits a significant (∼47% and ∼50%) association with type II bursts and halo CMEs, with a significantly faster median CME speed of 1000−120+550 km s−1. For DDPL EB≥20keV (DDPL EB<20keV ) with a positive (no) correlation between spectral indexes and no (a positive) correlation between the spectral index and break energy, the spectrum appears to be flatter as the associated CME (flare) becomes faster (stronger). These results suggest that the SPL type can result from the initial acceleration process that likely occurs high in the corona, and then provide seed populations for further acceleration processes to form the other five types: the DDPL EB<20keV and ER types via flare-related processes, the LP and DDPL EB≥20keV types via CME-related processes, and the UDPL type via CME-driven shocks.

The search for weak crustal magnetic fields on Mars using solar energetic electrons observed by the SEP instrument on-board the MAVEN spacecraft

The search for weak crustal magnetic fields on Mars using solar energetic electrons observed by the SEP instrument on-board the MAVEN spacecraft

Solar Type J Radio Bursts and the Associated Coronal Loop

The solar type J radio burst is a variant of type III bursts, which are a probe for understanding solar energetic electrons and local electron density. This study investigates a type J burst event on 2017 September 9. We have combined the data from the extreme-ultraviolet (EUV) imaging and the EUV Imaging Spectrometer (EIS) to analyze the event. Within 4 minutes several type J bursts with similar morphology occur. Two of them, with clear fundamental and second harmonic bands, are studied in detail. We find a delay of 2 ± 0.5 s between their different harmonic bands. During type J bursts, only one coronal loop brightens significantly at its northern footpoint, in correlation with the continuous injection of erupting jets into the loop. The EUV intensity of the brightening footpoint is correlated with the radio flux at 245 and 410 MHz, with correlation coefficients of 0.2 and 0.4, respectively. These observations suggest that the type J bursts should originate from this coronal loop. By analyzing the electron number density distribution along the coronal loop diagnosed from the EIS data and the time evolution of the plasma frequency calculated from the type J burst, we determine that the velocities of the energetic electrons exciting the two type Js are 0.10 ± 0.02c and 0.12 ± 0.02c. Our results confirm previous studies on type J bursts.

Exploring the Origin of Solar Energetic Electrons. I. Constraining the Properties of the Acceleration Region Plasma Environment

Solar flare electron acceleration is an efficient process, but its properties (mechanism, location) are not well constrained. Via hard X-ray (HXR) emission, we routinely observe energetic electrons at the Sun, and sometimes we detect energetic electrons in interplanetary space. We examine if the plasma properties of an acceleration region (size, temperature, density) can be constrained from in situ observations, helping to locate the acceleration region in the corona, and infer the relationship between electrons observed in situ and at the Sun. We model the transport of energetic electrons, accounting for collisional and non-collisional effects, from the corona into the heliosphere (to 1.0 au). In the corona, electrons are transported through a hot, over-dense region. We test if the properties of this region can be extracted from electron spectra (fluence and peak flux) at different heliospheric locations. We find that cold, dense coronal regions significantly reduce the energy at which we see the peak flux and fluence for distributions measured out to 1.0 au, the degree of which correlates with the temperature and density of plasma in the region. Where instrument energy resolution is insufficient to differentiate the corresponding peak values, the spectral ratio of [7–10) to [4–7) keV can be more readily identified and demonstrates the same relationship. If flare electrons detected in situ are produced in, and/or transported through, hot, over-dense regions close to HXR-emitting electrons, then this plasma signature should be present in their lower-energy spectra (1–20 keV), observable at varying heliospheric distances with missions such as Solar Orbiter.

Anisotropies of solar energetic electrons in the MeV range measured with Solar Orbiter/EPD/HET

Aims. This study analyses relativistic electron measurements obtained by the High Energy Telescope (HET) aboard Solar Orbiter in the energy range from 200 keV to above 10 MeV. Caveats of these measurements are discussed. The purpose of this study is to analyse anisotropies of relativistic solar energetic electrons utilising the different viewing directions of HET. Methods. We identified time periods of interest, that is, those with enhanced electron flux due to a significant solar component, and composed a list of these time periods, including additional observations such as maximum energy and flux as well as the first-order anistropy. Results. This study provides an overview of HET measurements of MeV electrons and a list of time periods of enhanced flux of relativistic solar electrons, 21 in total. For the first time with Solar Orbiter/EPD/HET, the anisotropies of high-energy electrons have been measured. Specifically, we find three time periods with significant anisotropy above 1 MeV within 0.5 au.

Correlations between space weather parameters during intense geomagnetic storms: Analytical study

We explore the correlation between different parameters of space weather events associated with intense geomagnetic disturbances that occurred during the solar cycles (SCs) 23 and 24 (1996–2019). The space weather events under this study are the Solar Flares (SFs), Coronal Mass Ejections (CMEs), Geomagnetic Storms (GSs), Solar Energetic Protons (SEPs) and Electrons (SEEs), respectively. The severity of the GSs is identified based on the Dst ⩽-100 nT and a list of 111 GSs with their associated space weather counterparts is obtained over the pre-selected time period. The utilized association procedure between the different space weather events is described and their observed properties are listed. For the performed analysis, Pearson correlation metrics is employed. The results are summarized and discussed.

On the Onset Delays of Solar Energetic Electrons and Protons: Evidence for a Common Accelerator

The processes responsible for the acceleration of solar energetic particles (SEPs) are still not well understood, including whether SEP electrons and protons are accelerated by common or separate processes. Using a numerical particle transport model that includes both pitch-angle and perpendicular spatial diffusion, we simulate, among other quantities, the onset delay for MeV electrons and protons and compare the results to observations of SEPs from widely separated spacecraft. Such observations have previously been interpreted, in a simple scenario assuming no perpendicular diffusion, as evidence for different electron and proton sources. We show that, by assuming a common particle source together with perpendicular diffusion, we are able to simultaneously reproduce the onset delays for both electrons and protons. We argue that this points toward a common accelerator for these particles. Moreover, a relatively broad particle source is required in the model to correctly describe the observations. This is suggestive of diffusive shock acceleration occurring at large shock structures playing a significant role in the acceleration of these SEPs.

Solar activity relations in energetic electron events measured by the MESSENGER mission

Aims. We perform a statistical study of the relations between the properties of solar energetic electron (SEE) events measured by the MESSENGER mission from 2010 to 2015 and the parameters of the respective parent solar activity phenomena in order to identify the potential correlations between them. During the time of analysis, the MESSENGER heliocentric distance varied between 0.31 and 0.47 au. Methods. We used a published list of 61 SEE events measured by MESSENGER, which includes information on the near-relativistic electron peak intensities, the peak-intensity energy spectral indices, and the measured X-ray peak intensity of the flares related to the SEE events. Taking advantage of multi-viewpoint remote-sensing observations, we reconstructed, whenever possible, the associated coronal mass ejections (CMEs) and shock waves; and we determined the three-dimensional (3D) properties (location, speed, and width) of the CMEs and the maximum speed of the 3D CME-driven shocks in the corona. We used different methods (Spearman, Pearson, and a Bayesian approach, namely the Kelly method to linear regression) to estimate the correlation coefficients between the flare intensity, maximum speed at the apex of the CME-driven shock, CME speed at the apex, and CME width with the electron peak intensities and with the energy spectral indices. In this statistical study, we considered and addressed the limitations of the particle instrument on board MESSENGER (elevated background intensity level, anti-Sun pointing). Results. There is an asymmetry to the east in the range of connection angles (CAs) for which the SEE events present the highest peak intensities, where the CA is the longitudinal separation between the footpoint of the magnetic field connecting to the spacecraft and the flare location. Based on this asymmetry, we define a subsample of well-connected events as when −65° ≤ CA ≤ +33°. For the well-connected sample, we find moderate to strong correlations between the near-relativistic electron peak intensity and the 3D CME-driven shock maximum speed at the apex (Spearman: cc = 0.53 ± 0.05; Pearson: cc = 0.65 ± 0.04; Kelly: cc = 0.87 ± 0.20), the flare peak intensity (Spearman: cc = 0.63 ± 0.03; Pearson: cc = 0.59 ± 0.03; Kelly: cc = 0.74 ± 0.30), and the 3D CME speed at the apex (Spearman: cc = 0.50 ± 0.04; Pearson: cc = 0.46 ± 0.03; Kelly: cc = 0.60 ± 0.39). When including poorly connected events (full sample), the relations between the peak intensities and the solar-activity phenomena are blurred, showing lower correlation coefficients. Conclusions. Based on the comparison of the correlation coefficients presented in this study using near 0.4 au data, (1) both flare and shock-related processes may contribute to the acceleration of near relativistic electrons in large SEE events, in agreement with previous studies based on near 1 au data; and (2) the maximum speed of the CME-driven shock is a better parameter to investigate particle-acceleration-related mechanisms than the average CME speed, as suggested by the stronger correlation with the SEE peak intensities.

The 2013 November 12 Solar Energetic Electron Event Associated with Solar Jets

We investigate the hard X-ray (HXR) flare-associated “prompt” solar energetic electron (SEE) 2013 November 12 event with joint EUV jet observations from Solar Dynamics Observatory/Atmospheric Imaging Assembly and STEREO-A/EUVI. The SEE energy spectrum observed by Wind/3D Plasma and Energetic Particle shows a triple-power-law shape with a low-energy break of 10.0 ± 1.7 keV and a high-energy break of 56.6 ± 8.9 keV, which has never been reported before for jet-related SEE events. Associated HXR emissions observed by RHESSI and FGST/Gamma-ray Burst Monitor show three distinctive peaks with different spectral indices β HPE of HXR-producing electrons (HPEs) derived by means of thick-target bremsstrahlung model. The high-energy spectral index β 3 = 4.63 ± 0.65 of SEE is consistent with the HPE spectral index β HPE derived in HXR peak 1 but different from β HPE of HXR peak 2 and peak 3. The main stream of EUV jets reaches a speed of 370 ± 25 km s−1 after an acceleration of up to 2.9 ± 0.4 km s−2 in a timescale of ∼2 minutes, and the acceleration time coincides with the decay phase of HXR peak 1. EUV observations from two different viewing directions help to reconstruct the jet magnetic configurations. After the investigation on HXR emissions and jet configurations, the interchange-reconnection model triggered by the emerging flux could be a satisfactory explanation for this jet event.

Energy Spectrum of Solar Energetic Electron Events over 25 Years

We investigate the peak flux energy spectrum of 458 solar energetic electron (SEE) events with a clear velocity dispersion detected at energies from ≤4.2 to ≥108 keV by Wind/3DP from 1994 December through 2019 December, utilizing a pan-spectrum fitting method. According to the fitted spectral parameters, these 458 events are self-consistently classified into five spectral types: 304 downward double-power-law (DDPL) events, 32 upward double-power-law (UDPL) events, 23 single-power-law (SPL) events, 44 Ellison–Ramaty (ER) events, and 55 logarithmic–parabola (LP) events. The DDPL events can be further divided into two types: 231 events and 73 events, since their break energy E B exhibits a double-peak distribution separated by a dip at ∼20 keV. The () events show a power-law spectral index of () at energies below () keV and an index of () at energies above. The UDPL events have a spectral index of at energies below keV and an index of at energies above. The SPL events exhibit a spectral index of . The ER events show a spectral index of at energies below keV. The LP events are characterized by a spectral slope of () at 2.8 keV (108 keV). The six spectral types also behave differently in the relationship between spectral parameters and in solar cycle variations. The spectral shape of most SEE events appears to be unrelated to the estimated electron path lengths. These results suggest that the formation of SEE events can involve complex processes/sources.

Statistical Study of Release Time and Its Energy Dependence of In Situ Energetic Electrons in Impulsive Solar Flares

AbstractUsing the fraction velocity dispersion analysis method, it has been shown recently that in two impulsive solar energetic electron (SEE) events, the release times of near‐relativistic electrons at the Sun for outward‐propagating electrons are energy dependent and are delayed compared to those of the downward‐propagating electrons. In this work, we perform a statistical study of the release time and its energy dependence of near‐relativistic electrons in impulsive SEE events. We use in situ observations from the WIND spacecraft and remote hard X‐ray observations from the RHESSI and/or Fermi spacecraft. The difference in the release times between outward electrons and downward electrons for 29 events is obtained. In all events, the release of the outward‐propagating electrons is delayed from those precipitating downward. In 26 of the 29 events, the release times of outward‐propagating electrons also show clear energy dependence. In 15 of these 26 events, in situ electron data from more than five energy channels were available. The delay time as a function of energy for nine of these can be fitted by a form proposed by G. Li et al. (2021, https://doi.org/10.1029/2021GL095138). The implication of this energy‐dependent release on the Magnetohydrodynamics turbulence property at the electron acceleration site is discussed.

Solar energetic electron events measured by MESSENGER and Solar Orbiter

Context. We present a list of 61 solar energetic electron (SEE) events measured by the MESSENGER mission and the radial dependences of some parameters associated with these SEE events. The analysis covers the period from 2010 to 2015, when the heliocentric distance of MESSENGER varied between 0.31 and 0.47 au. We also show the radial dependences for a shorter list of 12 SEE events measured in February and March 2022 by spacecraft near 1 au and by Solar Orbiter at about its first close perihelion at 0.32 au. Aims. We study the radial dependences of the electron peak intensity and the energy spectrum of the electron intensity at the time of the SEE event peak intensity, taking advantage of multi-spacecraft measurements. Methods. We compiled the list of SEE events measured by MESSENGER and Solar Orbiter using hourly averages to find the prompt component of the near-relativistic (∼70–110 keV) electron peak intensities and to calculate the peak-intensity energy spectra. We also obtained the peak intensities and energy spectra for the same events as measured by the STEREO-A, -B, ACE, or Wind spacecraft when one of these spacecraft was in close nominal magnetic connection with MESSENGER or Solar Orbiter to derive the radial dependences of these SEE parameters. Results. (1) Because the background intensity level of the particle instrument on board MESSENGER is high, the SEE events measured by this mission are necessarily large and intense; most of them are accompanied by a shock driven by a coronal mass ejection and are widely spread in heliolongitude. The SEE events display relativistic (∼1 MeV) electron intensity enhancements. For this SEE sample, we found that (2) the SEE peak intensity shows a radial dependence that can be expressed as Rα, where the median value of the α index is αMed = −3.3±1.4 for a subsample of 28 events for which the nominal magnetic footpoints of the near 0.3 au and 1 au spacecraft were close in heliographic longitude. (3) The mean spectral index δ of a subset of 42 events for which the energy spectrum could be analysed is ⟨δ⟩= − 1.9 ± 0.3, which is harder than the value found in previous studies using data from spacecraft near 1 au. SEE events observed by Solar Orbiter also display harder energy spectra than previous studies using data obtained near 1 au. Conclusions. There is a wide variability in the radial dependence of the electron peak intensities, but on average and within uncertainties, the ∝R−3 dependence found in previous observational and modelling studies is confirmed. The electron spectral index found in the energy range around ∼200 keV (δ200) of the backward-scattered population near 0.3 au measured by MESSENGER is harder by a median factor of ∼20% and ∼10% when comparing to the near 1 au anti-sunward propagating beam and the backward-scattered population, respectively.

Solar Radio Bursts Associated with In Situ Detected Energetic Electrons in Solar Cycles 23 and 24

The first comprehensive analysis between the in situ detected solar energetic electrons (SEEs) from ACE/EPAM satellite and remotely observed radio signatures in solar cycles (SCs) 23 and 24 (1997–2019) is presented. The identified solar origin of the SEEs (in terms of solar flares, SFs, and coronal mass ejections, CMEs) is associated with solar radio emission of types II, III and IV, where possible. Occurrence rates are calculated as a function of the radio wavelength, from the low corona to the interplanetary space near Earth. The tendencies of the different burst appearances with respect to SC, helio-longitude, and SEE intensity are also demonstrated. The corresponding trends of the driver (in terms of median values of the SF class and CME projected speed) are also shown. A comparison with the respective results when using solar energetic protons is presented and discussed.

On the Role of Coronal Shocks for Accelerating Solar Energetic Electrons

Abstract We study the role of coronal mass ejection (CME) driven shocks in the acceleration of solar energetic electrons. Using observations by the two STEREO spacecraft, we correlate electron peak intensities of solar energetic particle events measured in situ with various parameters of the associated coronal shocks. These shock parameters were derived by combining 3D shock reconstructions with global modeling of the corona. This modeling technique provides also shock properties in the specific shock regions that are magnetically connected to the two STEREO spacecraft. We find significant correlations between the peak intensities and the Mach number of the shock with correlation coefficients of about 0.7, which are similar for electrons at ∼1 MeV and protons at &gt;60 MeV. Lower-energy electrons with &lt;100 keV show a smaller correlation coefficient of 0.47. The causal relationship between electron intensities and the shock properties is supported by the vanishing correlations when peak intensities at STEREO A are related with the Alfvénic Mach number at the magnetic footpoint of STEREO B and vice versa, which yields correlation coefficients of 0.03 and −0.13 for ∼1 MeV and &lt;100 keV electron peak intensities, respectively. We conclude that the high-energy electrons are accelerated mainly by the shock, while the low-energy electrons are likely produced by a mixture of flare and shock-related acceleration processes.

The Impact of Energetic Particles on the Martian Ionosphere During a Full Solar Cycle of Radar Observations: Radar Blackouts

AbstractWe present the first long‐term characterization of ionization layers in the lower ionosphere of Mars (below ∼90 km), a region inaccessible to orbital in‐situ observations, based on an analysis of radar echo blackouts observed on Mars Express and the Mars Reconnaissance Orbiter from 2006 to 2017. A blackout occurs when the expected surface reflection is partly or totally attenuated for portions of an observation. Enhanced ionization at altitudes of 60–90 km, below the main ionospheric electron density peak, leads to increased absorption of the radar signal, resulting in the blackouts. We find that (a) MARSIS, operating at frequencies between 1.8 and 5 MHz, suffered more blackouts than SHARAD, which has a higher carrier frequency (20 MHz), (b) there is a clear correlation of blackout occurrence with solar cycle, (c) there is no apparent relationship between blackout occurrence and crustal magnetic fields, and (d) blackouts occur during both nightside and dayside observations, although the peak occurrence is deep on the nightside. Analysis of Mars Atmosphere and Volatile EvolutioN Solar Energetic Particle electron counts between 20 and 200 keV demonstrates that these electrons are likely responsible for attenuating the radar signals. We investigate the minimum SEP electron fluxes required to ionize the lower atmosphere and produce measurable attenuation. When both radars experience a blackout, the SEP electron fluxes are at their highest. Based on several case studies, we find that the average SEP spectrum responsible for a blackout is particularly enhanced at its higher energy end, that is, above 70 keV.

Connecting solar flare hard X-ray spectra to in situ electron spectra

Aims. We aim to constrain the acceleration, injection, and transport processes of flare-accelerated energetic electrons by comparing their characteristics at the Sun with those injected into interplanetary space. Methods. We have identified 17 energetic electron events well-observed with the SEPT instrument aboard STEREO which show a clear association with a hard X-ray (HXR) flare observed with the RHESSI spacecraft. We compare the spectral indices of the RHESSI HXR spectra with those of the interplanetary electrons. Because of the frequent double-power-law shape of the in situ electron spectra, we paid special attention to the choice of the spectral index used for comparison. Results. The time difference between the electron onsets and the associated type III and microwave bursts suggests that the electron events are detected at 1 AU with apparent delays ranging from 9 to 41 min. While the parent solar activity is clearly impulsive, also showing a high correlation with extreme ultraviolet jets, most of the studied events occur in temporal coincidence with coronal mass ejections (CMEs). In spite of the observed onset delays and presence of CMEs in the low corona, we find a significant correlation of about 0.8 between the spectral indices of the HXR flare and the in situ electrons. The correlations increase if only events with significant anisotropy are considered. This suggests that transport effects can alter the injected spectra leading to a strongly reduced imprint of the flare acceleration. Conclusions. We conclude that interplanetary transport effects must be taken into account when inferring the initial acceleration of solar energetic electron events. Although our results suggest a clear imprint of flare acceleration for the analyzed event sample, a secondary acceleration might be present which could account for the observed delays. However, the limited and variable pitch-angle coverage of SEPT could also be the reason for the observed delays.

Catalogue ofin situobserved solar energetic electrons from ACE/EPAM instrument

ABSTRACTWe present the first comprehensive catalogue of in situ observed solar energetic electron (SEE) events that covers solar cycles [SCs] 23 and 24 in the energy range 103–315 keV. The electron enhancements are detected by the Electron, Proton, and Alpha Monitor − Deflected Electrons instrument [EPAM-DE] aboard the ACE spacecraft. Onset time, peak time, background-subtracted peak electron intensity, and onset-to-peak fluence have been analysed for each event where possible. We describe the utilized procedure to identify the electron events and the criteria of their association to their solar origin: solar flares (SFs) and coronal mass ejections (CMEs). A statistical study between the peak electron intensity/fluence and the SF/CME properties, also with respect to the SC, is presented. In addition, we investigated the properties of the SEEs that are accompanied with solar energetic protons. Furthermore, the correlation between the intensity and fluence of the SEEs and those of the solar energetic protons are examined with respect to the SCs. The SEE catalogue is generated and posted on-line and will be updated whenever data are available. The purpose of this catalogue is to provide a publicly available service to solar and space physics communities. In addition, such catalogues are considered as a novel tool that can be used in real-time particle forecasting systems which are also relied upon to mitigate against harmful space weather effects due to particle events.