A New MEPED‐Based Precipitating Electron Data Set (original) (raw)
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Journal of Geophysical Research: Space Physics, 2016
The impact of energetic electron precipitation (EEP) on the chemistry of the middle atmosphere (50-90 km) is still an outstanding question as accurate quantification of EEP is lacking due to instrumental challenges and insufficient pitch angle coverage of current particle detectors. The Medium Energy Proton and Electron Detectors (MEPED) instrument on board the NOAA/Polar Orbiting Environmental Satellites (POES) and MetOp spacecraft has two sets of electron and proton telescopes pointing close to zenith (0°) and in the horizontal plane (90°). Using measurements from either the 0°or 90°telescope will underestimate or overestimate the bounce loss cone flux, respectively, as the energetic electron fluxes are often strongly anisotropic with decreasing fluxes toward the center of the loss cone. By combining the measurements from both telescopes with electron pitch angle distributions from theory of wave-particle interactions in the magnetosphere, a complete bounce loss cone flux is constructed for each of the electron energy channels >50 keV, >100 keV, and >300 keV. We apply a correction method to remove proton contamination in the electron counts. We also account for the relativistic (>1000 keV) electrons contaminating the proton detector at subauroral latitudes. This gives us full range coverage of electron energies that will be deposited in the middle atmosphere. Finally, we demonstrate the method's applicability on strongly anisotropic pitch angle distributions during a weak geomagnetic storm in February 2008. We compare the electron fluxes and subsequent energy deposition estimates to OH observations from the Microwave Limb Sounder on the Aura satellite substantiating that the estimated fluxes are representative for the true precipitating fluxes impacting the atmosphere.
Total electron content modelling for space weather applications
As modern society continues to develop a new sophisticated infrastructure, its dependence on the properties and behavior of the Sun- Earth system becomes more and more sensitive. The reliance on space-based technologies for communication, navigation and resource management as well as fast growing commercialization of space increase vulnerability to disruptions caused by space weather events requiring in depth knowledge of the whole solar-terrestrial environment. Understanding, prediction and potential mitigation of space weather impact on our technologically reliant society is by no means straightforward for several more or less known reasons. By presenting a method of the ionospheric vertical total electron content (VTEC) empirical modelling in relation to its simple application in long-term prediction; briefly reviewing the VTEC global, regional and local mapping procedures based on data from the International GNSS Service (IGS) network as the standard means of ionospheric real-ti...
Annales Geophysicae, 2005
Energy maps are important for ionospheremagnetosphere coupling studies, because quantitative determination of field-aligned currents requires knowledge of the conductances and their spatial gradients. By combining imaging riometer absorption and all-sky auroral optical data it is possible to produce high temporal and spatial resolution maps of the Maxwellian characteristic energy of precipitating electrons within a 240×240 km 2 common field of view. These data have been calibrated by inverting EIS-CAT electron density profiles into equivalent energy spectra. In this paper energy maps produced by ground-based instruments (optical and riometer) are compared with DMSP satellite data during geomagnetic conjunctions. For the period 1995-2002, twelve satellite passes over the groundbased instruments' field of view for the cloud-free conditions have been considered. Four of the satellite conjunctions occurred during moderate geomagnetic, steady-state conditions and without any ion precipitation. In these cases with Maxwellian satellite spectra, there is ∼71% agreement between the characteristic energies derived from the satellite and the ground-based energy map method.
A new climatological electron density model for supporting space weather services
Journal of Space Weather and Space Climate, 2021
The ionosphere is the ionized part of the Earth atmosphere, ranging from about 60 km up to several Earth radii whereas the upper part above about 1000 km height up to the plasmapause is usually called the plasmasphere. We present a new three-dimensional electron density model aiming for supporting space weather services and mitigation of propagation errors for trans-ionospheric signals. The model is developed by superposing the Neustrelitz Plasmasphere Model (NPSM) to an ionosphere model composed of separate F and E-layer distributions. It uses the Neustrelitz TEC model (NTCM), Neustrelitz Peak Density Model (NPDM) and the Neustrelitz Peak Height Model (NPHM) for the total electron content (TEC), peak ionization and peak height information. These models describe the spatial and temporal variability of the key parameters as function of local time, geographic/geomagnetic location, solar irradiation and activity. The model is particularly developed to calculate the electron concentrati...
A statistical approach to determining energetic outer radiation belt electron precipitation fluxes
Journal of Geophysical Research: Space Physics, 2014
Subionospheric radio wave data from an Antarctic-Arctic Radiation-Belt (Dynamic) Deposition VLF Atmospheric Research Konsortia (AARDDVARK) receiver located in Churchill, Canada, is analyzed to determine the characteristics of electron precipitation into the atmosphere over the range 3 < L < 7. The study advances previous work by combining signals from two U.S. transmitters from 20 July to 20 August 2010, allowing error estimates of derived electron precipitation fluxes to be calculated, including the application of time-varying electron energy spectral gradients. Electron precipitation observations from the NOAA POES satellites and a ground-based riometer provide intercomparison and context for the AARDDVARK measurements. AARDDVARK radiowave propagation data showed responses suggesting energetic electron precipitation from the outer radiation belt starting 27 July 2010 and lasting~20 days. The uncertainty in >30 keV precipitation flux determined by the AARDDVARK technique was found to be ±10%. Peak >30 keV precipitation fluxes of AARDDVARK-derived precipitation flux during the main and recovery phase of the largest geomagnetic storm, which started on 4 August 2010, were >10 5 el cm À2 s À1 sr À1. The largest fluxes observed by AARDDVARK occurred on the dayside and were delayed by several days from the start of the geomagnetic disturbance. During the main phase of the disturbances, nightside fluxes were dominant. Significant differences in flux estimates between POES, AARDDVARK, and the riometer were found after the main phase of the largest disturbance, with evidence provided to suggest that >700 keV electron precipitation was occurring. Currently the presence of such relativistic electron precipitation introduces some uncertainty in the analysis of AARDDVARK data, given the assumption of a power law electron precipitation spectrum. Energetic electron precipitation into the atmosphere over 3 < L < 7 acts as a loss mechanism for the outer radiation belt electron population [
Journal of Geophysical Research: Space Physics
A detailed comparison is undertaken of the energetic electron spectra and fluxes of two precipitation events that were observed in 18/19 January 2013. A novel but powerful technique of combining simultaneous ground-based subionospheric radio wave data and riometer absorption measurements with X-ray fluxes from a Balloon Array for Relativistic Radiation-belt Electron Losses (BARREL) balloon is used for the first time as an example of the analysis procedure. The two precipitation events are observed by all three instruments, and the relative timing is used to provide information/insight into the spatial extent and evolution of the precipitation regions. The two regions were found to be moving westward with drift periods of 5-11 h and with longitudinal dimensions of~20°and~70°(1.5-3.5 h of magnetic local time). The electron precipitation spectra during the events can be best represented by a peaked energy spectrum, with the peak in flux occurring at~1-1.2 MeV. This suggests that the radiation belt loss mechanism occurring is an energy-selective process, rather than one that precipitates the ambient trapped population. The motion, size, and energy spectra of the patches are consistent with electromagnetic ion cyclotron-induced electron precipitation driven by injected 10-100 keV protons. Radio wave modeling calculations applying the balloon-based fluxes were used for the first time and successfully reproduced the ground-based subionospheric radio wave and riometer observations, thus finding strong agreement between the observations and the BARREL measurements.
2010
AARDDVARK data from a radiowave receiver in Sodankylä, Finland have been used to monitor transmissions across the auroral oval and just into the polar cap from the very low frequency communications transmitter, call sign NAA, (24.0 kHz, 44N, 67W, L=2.9) in Maine, USA, since 2004. The transmissions are influenced by outer radiation belt (L=3-7) energetic electron precipitation. In this study we have been able to show that the observed transmission amplitude variations can be used to determine routinely the flux of energetic electrons entering the upper atmosphere along the total path, and between 30-90 km. Our analysis of the NAA observations shows that electron precipitation fluxes can vary by three orders of magnitude during geomagnetic storms. Typically when averaging over L=3-7 we find that the >100 keV POES 'trapped' fluxes peak at about 10 6 el.cm -2 s -1 sr -1 during geomagnetic storms, with the DEMETER >100 keV drift loss cone showing peak fluxes of 10 5 el.cm -2 s -1 sr -1 , and both the POES >100 keV 'loss' fluxes and the NAA groundbased >100 keV precipitation fluxes showing peaks of ~10 4 el.cm -2 s -1 sr -1 . During a geomagnetic storm in July 2005 there were systematic MLT variations in the fluxes observed: electron precipitation flux in the midnight sector (22-06 MLT) exceeded the fluxes from the morning side (0330-1130 MLT) and also from the afternoon sector (1130-1930 MLT). The analysis of NAA amplitude variability has the potential of providing a detailed, near real-time, picture of energetic electron precipitation fluxes from the outer radiation belts.
Relativistic electron precipitation (REP) in the atmosphere can contribute significantly to electron loss from the outer radiation belts. In order to estimate the contribution to this loss, it is important to estimate the spatial extent of the precipitation region. We observed REP with the zenith pointing (0 ∘) Medium Energy Proton Electron Detector (MEPED) on board Polar Orbiting Environmental Satellites (POES), for 15 years (2000–2014) and used both single-satellite and multisatellite measurements to estimate an average extent of the region of precipitation in L shell and magnetic local time (MLT). In the duration of 15 years (2000–2014), 31,035 REP events were found in this study. Events were found to split into two classes; one class of events coincided with proton precipitation in the P1 channel (30–80 keV), were located in the dusk and early morning sector, and were more localized in L shell (dL < 0.5), whereas the other class of events did not coincide with proton precipitation, were located mostly in the midnight sector, and were wider in L shell (dL ∼ 1–2.5). Both classes were highly localized in MLT (dMLT ≤ 3 h), occurring mostly during the declining phase of the solar cycle and geomagnetically active times. The events located in the midnight sector for both classes were found to be associated with tail magnetic field stretching which could be due to the fact that they tend to occur mostly during geomagnetically active times or could imply that precipitation is caused by current sheet scattering.
A comparison of precipitating electron energy flux on March 22, 1979 with an empirical model: CDAW 6
Journal of Geophysical Research, 1985
Data recorded by Defense Meteorological Satellite Program, TIROS and P-78-1 satellites for the CDAW 6 event on March 22, 1979, have been compared with a statistical model of precipitating electron fluxes. Comparisons have been made on both an orbit-by-orbit basis and on a global basis by sorting and binning the data by AE index, invariant latitude and magnetic local time in a manner similar to which the model was generated. We conclude that the model flux agrees with the data to within a factor of two, although small features and the exact locations of features are not consistently reproduced. In addition, the latitude of highest electron precipitation usually occurs about 3 ø more poleward in the model than in the data. We attribute this discrepancy to ring current inflation of the storm time magnetosphere (as evidenced by negative Dst's). We suggest that a similar empirical model based on AL instead of AE and including some indicator of the history of the event would provide an even better comparison. Alternatively, in situ data such as electroJet location should be used routinely to normalize the latitude of the auroral precipitation.