Solar wind drivers of energetic electron precipitation

Asikainen, Timo; Ruopsa, Miro

doi:10.1002/2015ja022215

Cited by 36 publications

(51 citation statements)

References 72 publications

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“…In order to assess whether the occurrence rate of the different types of storms will cause a systematic bias using the model throughout a The year 2003 is characterized by a high number of HSSWS and CIR events (Zhang et al, 2008), which despite some strong CME events dominate the annual contributions to EEP fluxes (>30 keV). The relative contribution of HSSWS and CME to EEP fluxes (>30 keV) is approximately equal in 2005, whereas 2008 is a year without significant CME activity (Asikainen & Ruopsa, 2016). In summary, it appears that the Ap model exaggerates the flux level difference between solar maximum and solar minimum compared to the median and mean LC flux levels.…”

Section: Yearly Variabilitymentioning

confidence: 87%

“…The year 2003 is characterized by a high number of HSSWS and CIR events (Zhang et al, ), which despite some strong CME events dominate the annual contributions to EEP fluxes (>30 keV). The relative contribution of HSSWS and CME to EEP fluxes (>30 keV) is approximately equal in 2005, whereas 2008 is a year without significant CME activity (Asikainen & Ruopsa, ). Figure shows POES/MEPED >43 keV LC fluxes binned according to Ap index and L shell separately for the three years.…”

Section: Poes/meped Lc Electron Fluxes and The Cmip6 Mee Parametrizationmentioning

confidence: 99%

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Intercomparison of the POES/MEPED Loss Cone Electron Fluxes With the CMIP6 Parametrization

et al. 2019

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Quantitative measurements of medium energy electron (MEE) precipitation (>40 keV) are a key to understand the total effect of particle precipitation on the atmosphere. The Medium Energy Proton and Electron Detector (MEPED) instrument on board the NOAA/Polar Orbiting Environmental Satellites (POES) has two sets of electron telescopes pointing ~0° and ~90° to the local vertical. Pitch angle anisotropy, which varies with particle energy, location, and geomagnetic activity, makes the 0° detector measurements a lower estimate of the flux of precipitating electrons. In the solar forcing recommended for Coupled Model Intercomparison Project (CMIP) 6 (v3.2) MEE precipitation is parameterized by Ap based on 0° detector measurements hence providing a general underestimate of the flux level. In order to assess the accuracy of the Ap model, we compare the modeled electron fluxes with estimates of the loss cone fluxes using both detectors in combination with electron pitch angle distributions from theory of wave‐particle interactions. The Ap model falls short in respect to reproducing the flux level and variability associated with strong geomagnetic storms (Ap > 40) as well as the duration of corotating interaction region storms causing a systematic bias within a solar cycle. As the Ap‐parameterized fluxes reach a plateau for Ap > 40, the model's ability to reflect the flux level of previous solar cycles associated with generally higher Ap values is questioned. The objective of this comparison is to understand the potential uncertainty in the energetic particle precipitation applying the CMIP6 particle energy input in order to assess its subsequent impact on the atmosphere.

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Section: Yearly Variabilitymentioning

confidence: 87%

Section: Poes/meped Lc Electron Fluxes and The Cmip6 Mee Parametrizationmentioning

confidence: 99%

Intercomparison of the POES/MEPED Loss Cone Electron Fluxes With the CMIP6 Parametrization

et al. 2019

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“…We use here the geomagnetic Ap index (http://isgi.unistra.fr) as a proxy for energetic electron precipitation (EEP), since this index correlates well with the observed EEP fluxes (e.g., Asikainen & Ruopsa, 2016 (Fisher, 1922). We also estimate significances of our results by using Monte Carlo simulation.…”

Section: Methodsmentioning

confidence: 99%

“…Both EPP and solar radiation vary over the sunspot cycle but depend differently on the cycle phase. Whereas total and spectral solar irradiance vary in phase with the sunspot cycle, the EPP activity is enhanced by fast solar wind streams which typically maximize at Earth a few years after the sunspot maximum (Asikainen & Ruopsa, ; Meredith et al, ; Mursula et al, ). Gray et al () found a delayed effect related on sunspot cycle on the troposphere which maximizes a couple of years after the sunspot maximum.…”

Section: Introductionmentioning

confidence: 99%

Dependence of Sudden Stratospheric Warmings on Internal and External Drivers

Salminen

Asikainen

Maliniemi

et al. 2020

Geophysical Research Letters

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A sudden stratospheric warming (SSW) is a large‐scale disturbance of the wintertime stratosphere, which occurs especially in the Northern Hemisphere. Earlier studies have shown that SSW occurrence depends on atmospheric internal factors and on solar activity. We examine SSW occurrence in northern winters 1957/1958–2016/2017, considering several factors that may affect the SSW occurrence: Quasi‐Biennial Oscillation (QBO), El Niño–Southern Oscillation (ENSO), geomagnetic activity, and solar radiation. We confirm the well‐known result that SSWs occur more often in easterly QBO phase than in westerly phase. We show that this difference depends on how the QBO phase is determined. We find that the difference in SSW occurrence between easterly and westerly QBO winters strengthens (weakens) if geomagnetic activity or solar activity is low (high), or if the ENSO is in a cold (warm) phase. In easterly QBO phase significantly more SSWs occur during low geomagnetic activity than high activity.

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“…As a general feature, one can see that the precipitation is mostly concentrated on two belts, the outer belt between about 60 • and 75 • and another one most clearly visible in 90 • telescope ( Figure 2) between 45 • and 60 • with a clear slot region with weaker fluxes in between around 60 • . One can also see the systematic solar cycle variation in the fluxes peaking in the declining phase of the cycles in 1984-1985, 1994, and 2003, which was recently discussed in more detail by Asikainen and Ruopsa (2016). In many cases, one can see large enhancements of the fluxes (esp.…”

Section: 1029/2018ja026214mentioning

confidence: 99%

New Homogeneous Composite of Energetic Electron Fluxes From POES Satellites: 1. Correction for Background Noise and Orbital Drift

Asikainen

Ruopsa

2019

JGR Space Physics

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One of the most popular long‐term data sets of energetic particles used in, for example, long‐term radiation belt studies and in atmospheric/climate studies is perhaps the National Oceanic and Atmospheric Administration/Polar Orbiting Environmental Satellites (POES) data set, which extends nearly continuously from 1979 to present. The energetic particle measurements by the Medium Energy Proton and Electron Detector instrument onboard the POES satellites have had many instrumental problems, which have made quantitative estimates of energetic particle fluxes somewhat difficult. However, in the recent years, these instrumental deficiencies have been studied and corrected. Here we aim to construct a new long‐term composite record of energetic electrons based on the Medium Energy Proton and Electron Detector data. In this study we point out that there are also other remaining factors, not related to instrument construction, which still severely impact the overall homogeneity of the 39‐year POES data set. We concentrate here on studying and correcting two issues: (1) temporally varying background noise related to cosmic rays and (2) drift in the orientation of satellite orbital planes, which changes the sampling location of the satellites over time. In particular, we show that the drift of satellite orbital planes leads to rather large changes in the electron fluxes over time, which could be misinterpreted as true temporal changes without the corrections. These changes can be rather large, a factor of 3 or more in the poleward edge of the precipitation zone, and are likely to have a large impact, for example, on atmospheric ionization estimates based on POES data.

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Solar wind drivers of energetic electron precipitation

Cited by 36 publications

References 72 publications

Intercomparison of the POES/MEPED Loss Cone Electron Fluxes With the CMIP6 Parametrization

Intercomparison of the POES/MEPED Loss Cone Electron Fluxes With the CMIP6 Parametrization

Dependence of Sudden Stratospheric Warmings on Internal and External Drivers

New Homogeneous Composite of Energetic Electron Fluxes From POES Satellites: 1. Correction for Background Noise and Orbital Drift

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