Precipitation Bursts Research Articles

First observation results of Macao Science Satellite 1 on lightning-induced electron precipitation

AbstractThe mid-energy electron detector (MEED) is a space-borne instrument onboard Macao Science Satellite 1 (MSS-1) dedicated to monitoring the typical charged particle radiation characteristics in the satellite orbit and the process of their occurrence and development, including short bursts of lightning-induced electron precipitation (LEP). This paper presents the first results of the LEP measurements by the MSS-1. 47 LEP events are identified with the routine operation for 3 months since satellite launch, all within the range of 1.5<L<3.0 (where L represents the McIlwain L-parameter), and the causative lightning discharges are definitively geo-located for these LEP events. The LEP events occur within <1 s of the causative lightning and consist of 40–300 keV electrons. A preliminary observation result indicates that, with medium-energy electron detectors, MSS-1 can present in-situ observations of large regions of enhanced background precipitation and reveal their fine spatiotemporal characteristics and spectral signatures. The collaborative VLF ground-based measurements at the Great Wall Station, Antarctica also have a good correspondence with LEP measurements of MSS-1. The observations also imply that lightning activity has a modulation effect on the energetic electron energy-spatial structure.

Electron Precipitation Driven by EMIC Waves: Two Types of Energy Dispersion

AbstractElectromagnetic ion cyclotron (EMIC) waves can very rapidly and effectively scatter relativistic electrons into the atmosphere. EMIC‐driven precipitation bursts can be detected by low‐altitude spacecraft, and analysis of the fine structure of such bursts may reveal unique information about the near‐equatorial EMIC source region. In this study, we report, for the first time, observations of EMIC‐driven electron precipitation exhibiting energy, E, dispersion as a function of latitude (and hence L‐shell): two predominant categories exhibit dE/dL > 0 and dE/dL < 0. We interpret precipitation with dE/dL < 0 as due to the typical inward radial gradient of cold plasma density and equatorial magnetic field (∼65% of the statistics). Precipitation with dE/dL > 0 is interpreted as due to an outward radial gradient of the equatorial magnetic field, likely produced by energetic ions freshly injected into the ring current (∼35% of the statistics). The observed energy dispersion of EMIC‐driven electron precipitation was reproduced in simulations.

Bursty Energetic Electron Precipitation by High‐Order Resonance With Very‐Oblique Whistler‐Mode Waves

AbstractResonant interactions with whistler‐mode waves are one of the most important drivers for rapid energetic electron precipitation. In this letter, we study a conjunction event, where bursts of energetic electron precipitation (50–800 keV) with timescales of several seconds are observed by the twin ELFIN Cubesats at low Earth orbit, while very‐oblique intense whistler‐mode waves are observed by the Time History of Events and Macroscale Interactions during Substorms E satellite at the conjugate magnetic equator. Our observation‐constrained test‐particle simulations reveal that the electron precipitation, particularly above 100 keV, results from high‐order resonant scattering by the very‐oblique whistler‐mode waves. Our study provides the first direct evidence for high‐order resonance driven precipitation, explaining a bursty precipitation event. The results demonstrate that high‐order resonant scattering could be important, not only in long‐term diffusion models, but also in models of short timescale events.

Relativistic Microburst Scale Size Induced by a Single Point‐Source Chorus Element

AbstractRelativistic microbursts are impulsive, sub‐second precipitation bursts of relativistic electrons. They are one of the main loss mechanisms of outer radiation belt electrons, and are driven by chorus waves. The scale size of relativistic microbursts is still not fully understood. In this work a global modeling of the microburst spatial distribution is conducted to study the scale size of relativistic microburst induced by chorus waves. A primary precipitation burst is induced near the source region by quasi‐parallel waves, and a secondary precipitation (SP) is induced on higher L‐shells by further‐propagating, oblique waves. The SP has a significant scale size even with a point‐source assumption because of wave spreading due to propagation effect. The secondary relativistic microburst scale size is ∼40(20) km on the counter (co)‐streaming side, consistent with previous observations. Our modeling results indicate chorus wave propagation effects are one of the primary factors controlling the relativistic microburst scale size.

Dust cycle and soiling issues affecting solar energy reductions in Australia using multiple datasets

Dust plays a vital role in the Earth’s climate system and can also modulate solar energy yield from photovoltaics due to soiling and it also impacts concentrated solar power outputs by up to 30%. Research examining decreased energy production on solar panels due to dust accumulation is limited. This is particularly important for dry arid regions of Australia, which are prone to dust storms. Thus, this paper examines the dust characteristics over Australia by comparing two reanalysis products, the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) and the Copernicus Atmosphere Monitoring Service (CAMS) with the satellite data (Himawari-8) to ascertain the capabilities of the reanalysis products in capturing dust cycles over Australia. The results are then used to explore the seasonal variability and trends in the radiative impacts, emissions, and depositions of dust. The energy reductions from seasonal averaged dust accumulations without natural removal or cleaning and later the impact of soiling with removal from precipitation bursts on selected operational solar farms are presented. Results show that MERRA-2 outperforms CAMS in capturing Dust Aerosol Optical Depth (AOD) near the Lake Eyre Basin in all seasons, consistent with satellite observations. The radiative trends showed contrasting differences during the Spring and Summer, whereas seasonal dust emissions and depositions peaked at 1.4 gm−2. Similarly, seasonal dust accumulations without natural removal on panels showed significant reductions in the energy of up to 3% around the Lake Eyre Basin, but most operational solar farms in Australia depicted energy reductions of 8–9% due to accumulated dust of up to 2.5–3 gm−2, which was naturally removed from regular seasonal rainfall bursts.

Riometer absorption during four similar storms

Absorption level by riometer was estimated at high-latitudes during four moderate magnetic storms that occurred in 2018 and were similar by several features. The data of riometer absorption at 30 MHz was obtained from Sodankylä Geophysical Observatory in Finland (67.36°N, 26.63°E). Particle precipitations were estimated by POES satellite data. According to our results, the character of development of the magnetic disturbance and the similarity/difference of Space Weather parameter variations (IMF magnitude, solar wind parameters, Dst variation) did not played the leading role in the absorption peak value. The absorption level in the auroral oval during the considered similar moderate magnetic disturbances depended on the combination of factors: simultaneous electron bursts of particular energies, the number of precipitating particles in these bursts and the moment of the storm at which such precipitation bursts occurred. The highest absorption was caused by the large electron precipitations with energies of >40 keV and >130 keV that occurred just after the maximal storm development at the very beginning of the recovery phase of the storm.

Polar Mesosphere Summer Echoes and Possible Signatures of Pulsating Aurora Detected by the Meteor Radar

AbstractUsing data of the all‐sky interferometric meteor radar (SKiYMET, 36.9 MHz) operating in the Sodankylä Geophysical Observatory (67°22′N, 26°38′E, Finland) we found a specific type of polar mesosphere summer echo (PMSE), the power of which exhibits irregular variations at a frequency of the order of a few Hz. We classified such radar echoes as pulsating PMSE. These echoes were observed in late June‐July in the morning sector (4–12 MLT) during geomagnetic storms. They were received from a narrow range of altitudes near 82 km, which corresponds to the altitude of noctilucent clouds where ice particles of about 50‐nm radii exist. During pulsating PMSE, the SGO ionosonde showed an electron density of the order of 3 × 1011 m−3 around 82 km, and enhanced D‐region ionization was manifested in the cosmic noise absorption. We suggest that the power of PMSE is modulated by bursts of electron precipitation corresponding to the few‐Hz internal modulation of pulsating aurora. During a short precipitation burst of 50–100 keV electrons, additional electrons can attach to the ice particles due to the presence of hyperthermal electrons according to the hypothesis proposed by Rosenberg et al. (2012, https://doi.org/10.1016/j.jastp.2011.10.011). This leads to an increase of the power of PMSE. After the burst is ended, the ice particles are deionized with a characteristic time of about 0.2 s due to attractive interaction with ions.

Quasiperiodic Emissions and Related Particle Precipitation Bursts Observed by the DEMETER Spacecraft

AbstractElectromagnetic 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.

Relativistic Electron Microbursts as High‐Energy Tail of Pulsating Aurora Electrons

AbstractIn this study, by simulating the wave‐particle interactions, we show that subrelativistic/relativistic electron microbursts form the high‐energy tail of pulsating aurora (PsA). Whistler‐mode chorus waves that propagate along the magnetic field lines at high latitudes cause precipitation bursts of electrons with a wide energy range from a few kiloelectron volts (PsA) to several megaelectron volts (relativistic microbursts). The rising tone elements of chorus waves cause individual microbursts of subrelativistic/relativistic electrons and the internal modulation of PsA with a frequency of a few hertz. The chorus bursts for a few seconds cause the microburst trains of subrelativistic/relativistic electrons and the main pulsations of PsA. Our simulation studies demonstrate that both PsA and relativistic electron microbursts originate simultaneously from pitch angle scattering by chorus wave‐particle interactions along the field line.

A New Technique for Estimating the Lifetime of Bursts of Electron Precipitation From Sounding Rocket Measurements

AbstractAt 0735 UT on 13 December 2015, the Rocket Experiment for Neutral Upwelling‐2 experiment launched north toward the auroral cusp region from Andoya, Norway. The instrumented rocket included an electron spectrometer, photometers that measured the auroral redline and greenline, and an instrument that measured ionospheric thermal electron temperature. On the down leg, just south of Svalbard, the rocket entered a region of poleward moving auroral forms that were characterized by narrow structures due to a combination of spatial and temporal variations. A noticeable feature was that the redline to greenline brightness ratio was much smaller than expected. A model is developed that shows that these emissions can be used to estimate the lifetimes of bursty electron precipitation. This model is shown to be consistent with some poleward moving auroral form lifetimes being on the order of 100 ms. The correlation between the precipitation and temperature bursts suggest that some transport occurred.

Hybrid-Vlasov modelling of nightside auroral proton precipitation during southward interplanetary magnetic field conditions

Abstract. Particle precipitation plays a key role in the coupling of the terrestrial magnetosphere and ionosphere by modifying the upper atmospheric conductivity and chemistry, driving field-aligned currents, and producing aurora. Yet quantitative observations of precipitating fluxes are limited, since ground-based instruments can only provide indirect measurements of precipitation, while particle telescopes aboard spacecraft merely enable point-like in situ observations with an inherently coarse time resolution above a given location. Further, orbit timescales generally prevent the analysis of whole events. On the other hand, global magnetospheric simulations can provide estimations of particle precipitation with a global view and higher time resolution. We present the first results of auroral (∼1–30 keV) proton precipitation estimation using the Vlasiator global hybrid-Vlasov model in a noon–midnight meridional plane simulation driven by steady solar wind with a southward interplanetary magnetic field. We first calculate the bounce loss-cone angle value at selected locations in the simulated nightside magnetosphere. Then, using the velocity distribution function representation of the proton population at those selected points, we study the population inside the loss cone. This enables the estimation of differential precipitating number fluxes as would be measured by a particle detector aboard a low-Earth-orbiting (LEO) spacecraft. The obtained differential flux values are in agreement with a well-established empirical model in the midnight sector, as are the integral energy flux and mean precipitating energy. We discuss the time evolution of the precipitation parameters derived in this manner in the global context of nightside magnetospheric activity in this simulation, and we find in particular that precipitation bursts of <1 min duration can be self-consistently and unambiguously associated with dipolarising flux bundles generated by tail reconnection. We also find that the transition region seems to partly regulate the transmission of precipitating protons to the inner magnetosphere, suggesting that it has an active role in regulating ionospheric precipitation.

Integrating risk perceptions into flood risk management: Trinidad case study

Flooding disasters are frequent and devastating events in Trinidad. Moderate amounts of precipitation burst riverbanks in central business districts, cities, and towns within the country. These burst riverbanks result in flooding disasters that negatively impact the economic, social, and physical environmental facets of development in this small island developing state. As the severity and frequency of flooding disasters increase, there is a greater need to increase Trinidad’s risk reduction initiatives towards the flood risk. With the continued shrinking of Trinidad’s economy, there is an absence of sustainable disaster reduction initiatives. Therefore, every dollar that is spent on the implementation of disaster risk reduction initiatives should be efficient, effective, and sustainable. Flood risk models play a fundamental role in the implementation of efficient, effective, and sustainable disaster risk reduction initiatives. Most flood risk models primarily utilize quantitative methods in their analysis. The goal of efficient, effective, and comprehensive disaster risk reduction initiatives, however, may not be achievable through the sole use of quantitative methods since most formulae are unable to embody the social, psychological, or cultural components of risk. A more effective approach is to broaden the analysis process by integrating qualitative indigenous knowledge with quantitative methods. This research sought to present a methodology that integrates qualitative information and quantitative geomatic methods to create a comprehensive flood assessment method. Results indicate that this integration can positively influence risk modelling since pertinent information concerning potential risks, excluded by past statistical summaries, can now be included, analysed, and modelled.

A statistical study over Europe of the relative locations of lightning and associated energetic burst of electrons from the radiation belt

Abstract. The DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) spacecraft detects short bursts of lightning-induced electron precipitation (LEP) simultaneously with newly injected upgoing whistlers. The LEP occurs within < 1 s of the causative lightning discharge. First in situ observations of the size and location of the region affected by the LEP precipitation are presented on the basis of a statistical study made over Europe using the DEMETER energetic particle detector, wave electric field experiment, and networks of lightning detection (Météorage, the UK Met Office Arrival Time Difference network (ATDnet), and the World Wide Lightning Location Network (WWLLN)). The LEP is shown to occur significantly north of the initial lightning and extends over some 1000 km on each side of the longitude of the lightning. In agreement with models of electron interaction with obliquely propagating lightning-generated whistlers, the distance from the LEP to the lightning decreases as lightning proceed to higher latitudes.

Remote sensing and modeling of energetic electron precipitation into the lower ionosphere using VLF/LF radio waves and field aligned current data

Abstract. A model for the development of electron density height profiles based on space time distributed ionization sources and reaction rates in the lower ionosphere is described. Special attention is payed to the definition of an auroral oval distribution function for energetic electron energy input into the lower ionosphere based on a Maxwellian energy spectrum. The distribution function is controlled by an activity parameter which is defined proportional to radio signal amplitude disturbances of a VLF/LF transmitter. Adjusting the proportionality constant allows to model precipitation caused VLF/LF signal disturbances using radio wave propagation calculations and to scale the distribution function. Field aligned current (FAC) data from the new Swarm satellite mission are used to constrain the spatial extent of the distribution function. As an example electron precipitation bursts during a moderate substorm on the 12 April 2014 (midnight–dawn) are modeled along the subauroral propagation path from the NFR/TFK transmitter (37.5 kHz, Iceland) to a midlatitude site.

Observations of coincident EMIC wave activity and duskside energetic electron precipitation on 18–19 January 2013

AbstractElectromagnetic ion cyclotron (EMIC) waves have been suggested to be a cause of radiation belt electron loss to the atmosphere. Here simultaneous, magnetically conjugate measurements are presented of EMIC wave activity, measured at geosynchronous orbit and on the ground, and energetic electron precipitation, seen by the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) campaign, on two consecutive days in January 2013. Multiple bursts of precipitation were observed on the duskside of the magnetosphere at the end of 18 January and again late on 19 January, concurrent with particle injections, substorm activity, and enhanced magnetospheric convection. The structure, timing, and spatial extent of the waves are compared to those of the precipitation during both days to determine when and where EMIC waves cause radiation belt electron precipitation. The conjugate measurements presented here provide observational support of the theoretical picture of duskside interaction of EMIC waves and MeV electrons leading to radiation belt loss.

Azimuthal flow bursts in the inner plasma sheet and possible connection with SAPS and plasma sheet earthward flow bursts

AbstractWe have combined radar observations and auroral images obtained during the Poker Flat Incoherent Scatter Radar Ion Neutral Observations in the Thermosphere campaign to show the common occurrence of westward moving, localized auroral brightenings near the auroral equatorward boundary and to show their association with azimuthally moving flow bursts near or within the subauroral polarization stream (SAPS) region. These results indicate that the SAPS region, rather than consisting of relatively stable proton precipitation and westward flows, can have rapidly varying flows, with speeds varying from ~100 m/s to ~1 km/s in just a few minutes. The auroral brightenings are associated with bursts of weak electron precipitation that move westward with the westward flow bursts and extend into the SAPS region. Additionally, our observations show evidence that the azimuthally moving flow bursts often connect to earthward (equatorward in the ionosphere) plasma sheet flow bursts. This indicates that rather than stopping or bouncing, some flow bursts turn azimuthally after reaching the inner plasma sheet and lead to the bursts of strong azimuthal flow. Evidence is also seen for a general guiding of the flow bursts by the large‐scale convection pattern, flow bursts within the duskside convection being azimuthally turned to the west, and those within the dawn cell being turned toward the east. The possibility that the SAPS region flow structures considered here may be connected to localized flow enhancements from the polar cap that cross the nightside auroral poleward boundary and lead to flow bursts within the plasma sheet warrants further consideration.

Assessment of flood hazard in a combined sewer system in Reykjavik city centre.

Short-duration precipitation bursts can cause substantial property damage and pose operational risks for wastewater managers. The objective of this study was to assess the present and possible future flood hazard in the combined sewer system in Reykjavik city centre. The catchment is characterised by two hills separated by a plain. A large portion of the pipes in the aging network are smaller than the current minimum diameter of 250 mm. Runoff and sewer flows were modelled using the MIKE URBAN software package incorporating both historical precipitation and synthetic storms derived from annual maximum rainfall data. Results suggest that 3% of public network manholes were vulnerable to flooding during an 11-year long rainfall sequence. A Chicago Design Storm (CDS) incorporating a 10-minute rainfall burst with a 5-year return period predicted twice as many flooded manholes at similar locations. A 20% increase in CDS intensity increased the number of flooded manholes and surface flood volume by 70% and 80%, respectively. The flood volume tripled if rainfall increase were combined with urban re-development, leading to a 20% increase in the runoff coefficient. Results highlight the need for reducing network vulnerabilities, which include decreased pipe diameters and low or drastically varying pipe grades.

Burst increases of precipitating electrons recorded by the DEMETER satellite before strong earthquakes

Abstract. This case study developed a method for data processing over six years, from 2004 to 2010, of 70 keV–2.3 MeV electrons recorded by the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite. Short time increases in electron counting rates, having 99% probabilities of not being Poisson fluctuations, were statistically selected using geomagnetic invariant space and called electron bursts. Temporal series were analysed confirming the seasonal variations in low energy bands of 70–450 keV. Differently from previous results, the DEMETER results exhibited two peaks of electron bursts: one in the period June–August and one in the period December–February annually. Specifically, six earthquake cases are presented in detail having increases in electron burst number prior to events. Moreover, electron burst precipitation occurring before each strong earthquake of the entire period over the life of the satellite with M ≥ 7.0 was verified as having a probability greater than 97% of not being of a statistical origin. Low energetic electrons in 70–330 keV resulted occurring more frequently near seismic activity than those observed in 330 keV–2.34 MeV energy bands at the satellite altitude in the ionosphere.

Energetic particle injection, acceleration, and loss during the geomagnetic disturbances which upset Galaxy 15

On 5 April 2010 a series of energetic electron injections, acceleration, and loss events appeared to induce an operational anomaly in the Galaxy 15 geosynchronous communications satellite. We describe the energetic electron precipitation conditions leading to the anomaly. A few hours prior to the anomaly electron acceleration at >0.6 MeV, and loss at >30 keV, were observed simultaneously. The acceleration took place in the region of the Galaxy 15 satellite on the nightside and the precipitation of electrons primarily on the dayside. The precipitation was confined to L‐shells outside of the plasmapause and appeared to be driven by chorus waves via a weak diffusion process. An hour prior to the anomaly, a solar wind shock event generated a few minutes of 30–150 keV electron precipitation but only on the dayside, over a largeL‐shell range (4.8 <L < 13). The timing of the precipitation burst was consistent with electromagnetic ion cyclotron (EMIC) waves seen on the dayside, but the high geomagnetic latitude of the precipitation suggests that EMIC wave growth associated with high cold density regions in the plasmasphere is unlikely to have played a role. A substorm injection event shortly after the shock appears to have ultimately triggered the upset on Galaxy 15. However, the peak >30 keV electron precipitation fluxes of 1.35 × 107 el cm−2 s−1 sr−1 were roughly the same level as other large substorm events previously analyzed, indicating either a sensitivity to the energetic electron environment prior to the event or that the satellite was in a vulnerable situation.

Characteristics of flux-time profiles, temporal evolution, and spatial distribution of radiation-belt electron precipitation bursts in the upper ionosphere before great and giant earthquakes

The analysis of energetic electron observations made by the DEMETER satellite reveals that radiation belt electron precipitation (RBEP) bursts are observed in general several (~1-6 days) before a large (M > 6.5) earthquake (EQ) in the presence of broad band (~1-20 kHz) VLF waves. The EBs show in general a relative peak-to-background flux increase usually < 100, they have a time duration of ~0.5 – 3 min, and their energy spectrum reach up to energies <~500 keV. The RBEP activity is observed as one, two or three EBs throughout a semi-orbit, depended on the magnetic field structure above the EQ epicenter. A statistical analysis has been made for earthquakes in Japan, which reveals a standard temporal variation of the number of EBs, which begins with an incremental rate several days before major earthquakes, and after a maximum, decreases so that the electron precipitation ceases above the epicenter. Some earthquake induced EBs were observed not only in the nightside ionosphere, but also in the dayside ionosphere.