Search

We analyze the properties of relativistic (>700 keV) electron precipitation (REP) events measured by the low-Earth-orbit (LEO) POES/MetOp constellation of spacecraft from 2012 through 2023. Leveraging the different profiles of REP observed at LEO, we associate each event with its possible driver: waves or field line curvature scattering (FLCS). While waves typically precipitate electrons in a localized radial region within the outer radiation belt, FLCS drives energy-dependent precipitation at the edge of the belt. Wave-driven REP is detected at any MLT sector and L shell, with FLCS-driven REP occurring only over the nightside–a region where field line stretching is frequent. Wave-driven REP is broader in radial extent on the dayside and accompanied by proton precipitation over 03–23 MLT, either isolated or without a clear energy-dependent pattern, possibly implying that electromagnetic ion cyclotron (EMIC) waves are the primary driver. Across midnight, both wave-driven and FLCS-driven REP occur poleward of the proton isotropic boundary. On average, waves precipitate a higher flux of >700 keV electrons than FLCS. Both contribute to energy deposition into the atmosphere, estimated of a few MW. REP is more associated with substorm activity than storms, with FLCS-driven REP and wave-driven REP at low L shells occurring most often during strong activity (SML* < −600 nT). A preliminary analysis of the Solar Wind (SW) properties before the observed REP indicates a more sustained (∼5 h) dayside reconnection for FLCS-driven REP than for wave-driven REP (∼3 h). The magnetosphere appears more compressed during wave-driven REP, while FLCS-driven REP is associated with a faster SW of lower density. These findings are useful not only to quantify the contribution of >700 keV precipitation to the atmosphere but also to shed light on the typical properties of wave-driven vs FLCS-driven precipitation which can be assimilated into physics-based and/or predictive radiation belt models. In addition, the dataset of ∼9,400 REP events is made available to the community to enable future work. [ABSTRACT FROM AUTHOR]

Precipitation into the Earth's atmosphere due to pitch angle scattering by plasma waves has been recognized as one of the major loss mechanisms for energetic electrons. In this study, we quantitatively evaluate their roles in precipitating electrons during a conjunction event with modulated electron precipitation observed at low altitudes by Electron Loss and Fields INvestigation and three types of whistler mode waves (hiss, plume hiss, and chorus) measured near the equator by Time History of Events and Macroscale Interactions during Substorms. Electron precipitation was observed from ∼50 keV to <1 MeV with a spatial modulation, suggested by a good correlation between L shell‐sorted precipitation fluxes and wave intensities. A quasi‐linear analysis supports the observed energy range of precipitation and the ratio of precipitating‐to‐trapped flux. Our findings reveal that the modulated energetic electron precipitation is driven by hiss, plume hiss, and chorus waves. Plain Language Summary: Energetic electrons precipitated from the inner magnetosphere into the upper atmosphere can form diffuse and discrete aurora and modulate the ionospheric conductance. One of the major drivers of electron precipitation is wave‐particle interaction with whistler mode waves. In this study, we use the Electron Loss and Fields INvestigation CubeSats to measure electron precipitation at low altitudes and the Time History of Events and Macroscale Interactions during Substorms to provide wave and plasma measurements near the magnetic equator in the conjugate locations. We find that the electron precipitation rate is highly correlated to the whistler mode wave intensity near the equator. Through a quasi‐linear analysis, we demonstrate that the modulation of electron precipitation is driven by whistler mode hiss, plume hiss, and chorus waves that occur in an extensive region of the Earth's magnetosphere. Key Points: Modulated electron precipitation from tens to hundreds of keV over L shells of 4–9 is observed by Electron Loss and Fields INvestigation at low altitudesA good correlation is observed between the spatial variations of electron precipitation and wave intensities of hiss, plume hiss, and chorusQuasi‐linear modeling based on the observed wave and plasma parameters reproduced the observed electron precipitation [ABSTRACT FROM AUTHOR]

The built environment remains a strategic research and innovation domain in view of the goal of full decarbonization. The priority is the retrofitting of existing buildings as zero-emission to improve their energy efficiency with renewable energy technologies pulling the market with cost-effective strategies. From the first age of photovoltaics (PV) mainly integrated in solar roofs, we rapidly moved towards complete active building skins where all the architectural surfaces are photoactive (Building Integrated Photovoltaics - BIPV). This change of paradigm, where PV replaces a conventional building material, shifted the attention to relate construction choices with energy and cost effectiveness. However, systematic investigations which put into action a cross-disciplinary approach between construction, economic and energy related domains is still missing. This paper provides the detailed assessment of a real multifamily building, taking into account retrofit scenarios for making active the building skin, with the goal to identify the sensitive aspects of the energetic and economic effectiveness of BIPV design options. By assuming a real case study with monitored data, the analysis will consider a breakdown of the main individual parts composing the building envelope, by then combining alternative re-configurations in merged clusters with different energy and construction goals. Results will highlight the correlation between building skin construction strategies and the energy and cost parameters by identifying the cornerstones for enhancing efficiency. The outcomes, related to the total life cost, self-consumption/sufficiency, in combination with different building design options (façade, roof, balconies, surface orientations, etc.), provide a practical insight for researchers and professionals to identify renovation strategies by synergistically exploiting the solar active parts towards lower global costs and higher energy efficiency of the whole building system. [ABSTRACT FROM AUTHOR]

We statistically evaluate the global distribution and energy spectrum of electron precipitation at low‐Earth‐orbit, using unprecedented pitch‐angle and energy resolved data from the Electron Losses and Fields INvestigation CubeSats. Our statistical results indicate that during active conditions, the ∼63 keV electron precipitation ratio peaks at L > 6 at midnight, whereas the spatial distribution of precipitating energy flux peaks between the dawn and noon sectors. ∼1 MeV electron precipitation ratio peaks near midnight at L > ∼6 but is enhanced near dusk during active times. The energy spectrum of the precipitation ratio shows reversal points indicating energy dispersion as a function of L shell in both the slot region and at L > ∼6, consistent with hiss‐driven precipitation and current sheet scattering, respectively. Our findings provide accurate quantification of electron precipitation at various energies in a broad region of the Earth's magnetosphere, which is critical for magnetosphere‐ionosphere coupling. Plain Language Summary: Precipitation into the Earth's upper atmosphere is an important loss process of radiation belt electrons and can change the ionospheric conductance and atmospheric chemistry. Electrons can be moved into the loss cone through either wave‐particle interactions or due to special magnetic field geometries, such as current sheet scattering (CSS). To determine the relative contribution of wave‐particle interactions and CSS, it is crucial to investigate the global distribution and energy spectra of the electron precipitation rate. Previous measurements of energetic electron precipitation at low‐Earth‐orbit either had low resolution in pitch angle and energy or were contaminated by ions and penetrating particles. In this study, we used data from the twin Electron Losses and Fields INvestigation CubeSats, which do not suffer from similar deficiencies, to statistically analyze the dependence of energetic electron precipitation rates on geomagnetic activity, with high resolution in both pitch angle and energy. These findings cast new light on the physical mechanisms that determine the precipitation rate from the magnetosphere into the atmosphere and may have implications for future studies of the ionospheric conductivity and atmospheric chemistry. Key Points: A global survey of electron precipitation is performed using the pitch angle and energy resolved data from Electron Losses and Fields INvestigation CubeSatsAt ∼1 MeV, electron precipitation is strongest at L > ∼6 near midnight and is enhanced near dusk during active timesThe energy spectrum of the precipitation ratio shows reversal points indicating energy dispersion in L shells in the slot region and L > ∼6 [ABSTRACT FROM AUTHOR]

Whistler mode waves in the plasmasphere and plumes drive significant losses of energetic electrons from the Earth's radiation belts into the upper atmosphere. In this study, we conducted a survey of amplitude‐dependent whistler wave properties and analyzed their associated background plasma conditions and electron fluxes in the plasmasphere and plumes. Our findings indicate that extremely large amplitude (>400 pT) whistler waves (a) tend to occur at L > 4 over the midnight‐dawn‐noon sectors and have small wave normal angles; (b) are more likely to occur during active geomagnetic conditions associated with higher fluxes of anisotropic electrons at 10 s keV energies; and (c) tend to occur at higher latitudes up to 20° with increasing amplitude. These results suggest that extremely large amplitude whistler waves in the plasmasphere and plumes could be generated locally by injected electrons during substorms and further amplified when propagating to higher latitudes. Plain Language Summary: Whistler mode waves are known as one of the primary drivers of precipitating energetic electrons from the Earth's radiation belts into the upper atmosphere. We utilize plasma wave observations from the Van Allen Probes mission and conduct a survey of whistler mode waves inside the plasmasphere and plumes, which are plasma regions surrounding the Earth and filled with high‐density cold electrons. Statistical results indicate that extremely large amplitude whistler waves are more likely to occur at large L shells (L shell is defined as the distance from magnetic field lines to the center of the Earth at the magnetic equator) in the post‐midnight sectors during active geomagnetic conditions associated with high fluxes of tens of keV electrons exhibiting anisotropic pitch angle distributions (with a flux peak in the direction that is perpendicular to the background magnetic field). These waves tend to occur at higher latitudes with increasing amplitude. Results suggest that these waves could be generated locally by injected electrons during substorm activity and may be further amplified when propagating to higher latitudes. Key Points: Van Allen Probes wave measurements are used to statistically analyze the whistler waves in the plasmasphere or plume regionsExtremely large amplitude (>400 pT) whistler waves tend to occur at L shells >4 over 0–18 hr MLT with small wave normal angles (<10°)Larger amplitude whistler waves are observed during more active substorm activities and higher magnetic latitudes [ABSTRACT FROM AUTHOR]

Compositional NOx changes caused by energetic electron precipitation (EEP) at a specific altitude and those co-dependent on vertical transport are referred to as the EEP direct and indirect effect, respectively. The direct effect of EEP at lower mesospheric and upper stratospheric altitudes is linked to the high-energy tail of EEP (> 300 keV). The relative importance of this direct effect on NOx, ozone, and atmospheric dynamics remains unresolved due to inadequate particle measurements and scarcity of polar mesospheric NOx observations. An accurate parameterization of the high-energy tail of EEP is, therefore, crucial. This study utilizes EEP flux data from MEPED aboard the POES/Metop satellites from 2004-2014. Data from both hemispheres (55-70° N/S) are combined in daily flux estimates. 164 peaks above the 90th percentile of the > 30 keV flux are identified. These peaks are categorized into absolute E1 and E3 events representing weak and strong > 300 keV responses, respectively. A subset of absolute E1 and E3 events with similar > 30 keV responses is termed overlapping events. Additionally, relative E1 and E3 events are determined by the relative strength of the > 300 keV response, scaled by the initial > 30 keV flux. A comparison between E1 and E3 events aims to identify solar wind and geomagnetic conditions leading to high-energy EEP responses and to gain insight into the conditions that generate a high-energy tail, independent of the initial > 30 keV flux level. Superposed epoch analysis of mesospheric NO density from SOFIE confirms an observable direct impact on lower mesospheric chemistry associated with the absolute E3 events. A probability assessment based on absolute events identifies specific thresholds in the solar wind- magnetosphere coupling function (epsilon) and the geomagnetic indices Kp*10 and Dst, capable of determining the occurrence or exclusion of absolute E1 and E3 events. Elevated solar wind speeds persisting in the recovery phase of a deep Dst trough appear characteristic of overlapping and relative E3 events. This study provides insight into which parameters are important for accurately modeling the high-energy tail of EEP. [ABSTRACT FROM AUTHOR]

Goal 7 of Agenda 2030 is focused on renewable energy. This study proposes a multi-criteria and multi-disciplinary methodology for analysing different incentive scenarios in Italy according to the varying conditions of system installation and the chosen photovoltaic technology (PV). The method is based on three key factors: energy, economic, and life cycle assessment of the photovoltaic system to achieve the improvement of the energy performance through technical and financial solutions that suit the existing buildings and strategies to limit environmental impacts. For the validation of the methodology was chosen the engineering campus of the University of L'Aquila, Italy, was chosen since the energy retrofit of public buildings must be dealt with by considering numerous parameters. These include economic constraints related to the public budget; technical constraints, as not all the solutions on the market, are compatible with the existing building body; and social constraints, as public administrations set an example for their communities and pioneer positive actions inspired by sustainability from every standpoint. The study showed as for defining the optimal scenario a multi-criteria approach is necessary and that a decision based on only technical and economic evaluations can not conduct to an optimal scenario selection. Furthermore, it has shown how subsidies are fundamental for the profitability of PV investments, which, although considered a renewable energy source, can derive non-negligible environmental impacts from these investments. Thus, the methodology adopted, which can be exported to other contexts, allows policy-makers choices to be weighed from many points of view. [Display omitted] • Integrated approach for renewable energy technologies (photovoltaic) is proposed. • Energy, economic, life cycle analysis for sustainable photovoltaic technologies. • Existing public building management promotes sustainable retrofitting. [ABSTRACT FROM AUTHOR]

Electromagnetic ion cyclotron (EMIC) waves could cause a simultaneous dropout of radiation belt electrons and ring current protons. However, their effects on the dropout of both plasma populations have not been quantified in previous studies. In this paper, we model the simultaneous dropout of MeV electrons and hundreds of keV protons observed by Van Allen Probes within ∼40 min on 27 February 2014. The wave and particle measurements during the period of most intense EMIC waves at L ∼ 5.2 are used to calculate the quasilinear diffusion coefficients and simulate the evolution of both energetic electrons and protons. Our model well captures the dropout of electrons with energies >1 MeV and pitch angles <75°, and the concurrent dropout of protons with energies >200 keV and pitch angles >40°. This is the first modeling work quantitatively reproducing the simultaneous dropout of both populations due to EMIC wave scattering. Plain Language Summary: Electromagnetic ion cyclotron (EMIC) waves are one of the plasma waves in the Earth's magnetosphere. Both radiation belt electrons and ring current protons can be scattered by EMIC waves into the atmosphere within a short timescale (∼hours). However, the role of EMIC waves in driving the simultaneous fast depletion of both populations has not been quantified. In this study, for the first time, we quantitatively modeled the temporal evolution of radiation belt electrons and ring current protons during a geomagnetic storm event based on the particle and wave observations by Van Allen Probes. The results suggest that EMIC wave scattering can efficiently cause the simultaneous depletion of both energetic electrons and protons on a timescale of ∼40 min. Key Points: Van Allen Probes observed a simultaneous dropout of radiation belt electrons and ring current protons within 40 min accompanied by electromagnetic ion cyclotron (EMIC) wavesThe simulation indicates that fast EMIC wave scattering causes the dropout of electrons with energies >1 MeV and pitch angles <75°Concurrent dropout of protons with energies >200 keV and pitch angles >40° is also reproduced by EMIC wave scattering [ABSTRACT FROM AUTHOR]