scholarly journals Magnetic local time dependency of radiation belt electron precipitation: impact on polar ozone

2020 ◽  
Author(s):  
Pekka T. Verronen ◽  
Daniel R. Marsh ◽  
Monika E. Szeląg ◽  
Niilo Kalakoski
Keyword(s):  
Local Time ◽  
Radiation Belt ◽  
Climate Model ◽  
Energetic Electron ◽  
Coupled Model ◽  
Magnetic Local Time ◽  
Polar Regions ◽  
Research Activity ◽  
Diurnal Variability ◽  
Polar Ozone

Abstract. The radiation belts are regions in the near-Earth space where solar wind electrons are captured by the Earth's magnetic field. A portion of these electrons is continuously lost into the atmosphere where they cause ionisation and chemical changes. Driven by solar activity, electron forcing leads to ozone variability in the polar regions. Understanding possible dynamical connections to regional climate is an on-going research activity which supports the assessment of greenhouse gas driven climate change by better definition of the solar-driven variability. In the context of the Coupled Model Intercomparison Project Phase 6 (CMIP6), energetic electron and proton precipitation is included in the solar forcing recommendation for the first time. For radiation belt electrons, CMIP6 forcing is from a daily, zonal mean proxy model. This zonal mean model ignores the well-known dependency of precipitation on magnetic local time (MLT), i.e. its diurnal variability. Here we use the Whole Atmosphere Community Climate Model with lower ionospheric chemistry extension (WACCM-D) to study the effect of MLT dependency of electron forcing on the polar ozone response. We analyse simulations applying MLT-dependent and MLT-independent forcings, and contrast ozone responses in monthly mean data as well as in monthly means of individual local time sectors. We consider two cases: 1) year 2003 and 2) extreme, long-duration forcing. Our results indicate that the ozone responses to MLT-dependent and MLT-independent forcings are very similar, and the differences found are small compared to those related to overall uncertainties in electron forcing. We conclude that electron forcing that ignores the MLT dependency will still provide an accurate ozone response in long-term climate simulations.

scholarly journals Magnetic-local-time dependency of radiation belt electron precipitation: impact on ozone in the polar middle atmosphere

2021 ◽  
Author(s):  
Pekka T. Verronen ◽  
Daniel R. Marsh ◽  
Monika E. Szeląg ◽  
Niilo Kalakoski
Keyword(s):  
Local Time ◽  
Radiation Belt ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Energetic Electron ◽  
Magnetic Local Time ◽  
Local Times ◽  
Ongoing Research ◽  
Diurnal Variability ◽  
Climate Simulations

<div> <div> <div> <p>The radiation belts are regions in the near-Earth space where solar wind electrons are captured by the Earth’s magnetic field. A portion of these electrons is continuously lost into the atmosphere where they cause ionization and chemical changes. Driven by the solar activity, the electron forcing leads to ozone variability in the polar stratosphere and mesosphere. Understanding the possible dynamical connections to regional climate is an ongoing research activity which supports the assessment of greenhouse-gas-driven climate change by a better definition of the solar-driven variability. In the context of the Coupled Model Intercomparison Project Phase 6 (CMIP6), energetic electron and proton precipitation is included in the solar-forcing recommendation for the first time. For the radiation belt electrons, the CMIP6 forcing is from a daily zonal-mean proxy model. This zonal-mean model ignores the well-known dependency of precipitation on magnetic local time (MLT), i.e. its diurnal variability. Here we use the Whole Atmosphere Community Climate Model with its lower-ionospheric-chemistry extension (WACCM-D) to study effects of the MLT dependency of electron forcing on the polar-ozone response. We analyse simulations applying MLT-dependent and MLT-independent forcings and contrast the resulting ozone responses in monthly-mean data as well as in monthly means at individual local times. We consider two cases: (1) the year 2003 and (2) an extreme, continuous forcing. Our results indicate that the ozone responses to the MLT-dependent and the MLT-independent forcings are very similar, and the differences found are small compared to those caused by the overall uncertainties related to the representation of electron forcing in climate simulations. We conclude that the use of daily zonal-mean electron forcing will provide an accurate ozone response in long-term climate simulations.</p> </div> </div> </div>

scholarly journals Magnetic-local-time dependency of radiation belt electron precipitation: impact on ozone in the polar middle atmosphere

2020 ◽  
Vol 38 (4) ◽  
pp. 833-844
Author(s):  
Pekka T. Verronen ◽  
Daniel R. Marsh ◽  
Monika E. Szeląg ◽  
Niilo Kalakoski
Keyword(s):  
Local Time ◽  
Radiation Belt ◽  
Climate Model ◽  
Middle Atmosphere ◽  
Energetic Electron ◽  
Magnetic Local Time ◽  
Local Times ◽  
Ongoing Research ◽  
Diurnal Variability ◽  
Climate Simulations

Abstract. The radiation belts are regions in the near-Earth space where solar wind electrons are captured by the Earth's magnetic field. A portion of these electrons is continuously lost into the atmosphere where they cause ionization and chemical changes. Driven by the solar activity, the electron forcing leads to ozone variability in the polar stratosphere and mesosphere. Understanding the possible dynamical connections to regional climate is an ongoing research activity which supports the assessment of greenhouse-gas-driven climate change by a better definition of the solar-driven variability. In the context of the Coupled Model Intercomparison Project Phase 6 (CMIP6), energetic electron and proton precipitation is included in the solar-forcing recommendation for the first time. For the radiation belt electrons, the CMIP6 forcing is from a daily zonal-mean proxy model. This zonal-mean model ignores the well-known dependency of precipitation on magnetic local time (MLT), i.e. its diurnal variability. Here we use the Whole Atmosphere Community Climate Model with its lower-ionospheric-chemistry extension (WACCM-D) to study effects of the MLT dependency of electron forcing on the polar-ozone response. We analyse simulations applying MLT-dependent and MLT-independent forcings and contrast the resulting ozone responses in monthly-mean data as well as in monthly means at individual local times. We consider two cases: (1) the year 2003 and (2) an extreme, continuous forcing. Our results indicate that the ozone responses to the MLT-dependent and the MLT-independent forcings are very similar, and the differences found are small compared to those caused by the overall uncertainties related to the representation of electron forcing in climate simulations. We conclude that the use of daily zonal-mean electron forcing will provide an accurate ozone response in long-term climate simulations.

scholarly journals POLAR spacecraft observations of helium ion angular anisotropy in the Earth's radiation belts

1999 ◽  
Vol 17 (6) ◽  
pp. 723-733 ◽  
Author(s):  
W. N. Spjeldvik ◽  
T. A. Fritz ◽  
J. Chen ◽  
R. B. Sheldon
Keyword(s):  
Local Time ◽  
Pitch Angle ◽  
Radiation Belt ◽  
Radiation Belts ◽  
Magnetic Local Time ◽  
Angle Distribution ◽  
Pitch Angle Distribution ◽  
Helium Ion ◽  
Earth’S Radiation Belt ◽  
Earth's Radiation Belts

Abstract. New observations of energetic helium ion fluxes in the Earth's radiation belts have been obtained with the CAMMICE/HIT instrument on the ISTP/GGS POLAR spacecraft during the extended geomagnetically low activity period April through October 1996. POLAR executes a high inclination trajectory that crosses over both polar cap regions and passes over the geomagnetic equator in the heart of the radiation belts. The latter attribute makes possible direct observations of nearly the full equatorial helium ion pitch angle distributions in the heart of the Earth's radiation belt region. Additionally, the spacecraft often re-encounters the same geomagnetic flux tube at a substantially off-equatorial location within a few tens of minutes prior to or after the equatorial crossing. This makes both the equatorial pitch angle distribution and an expanded view of the local off-equatorial pitch angle distribution observable. The orbit of POLAR also permitted observations to be made in conjugate magnetic local time sectors over the course of the same day, and this afforded direct comparison of observations on diametrically opposite locations in the Earth's radiation belt region at closely spaced times. Results from four helium ion data channels covering ion kinetic energies from 520 to 8200 KeV show that the distributions display trapped particle characteristics with angular flux peaks for equatorially mirroring particles as one might reasonably expect. However, the helium ion pitch angle distributions generally flattened out for equatorial pitch angles below about 45°. Significant and systematic helium ion anisotropy difference at conjugate magnetic local time were also observed, and we report quiet time azimuthal variations of the anisotropy index.Key words. Magnetospheric physics (energetic particles · trapped; magnetospheric configuration and dynamics; plasmasphere)

scholarly journals Thermospheric Neutral Winds as the Cause of Drift Shell Distortion in Earth’s Inner Radiation Belt

2021 ◽  
Vol 8 ◽  
Author(s):  
Solène Lejosne ◽  
Mariangel Fedrizzi ◽  
Naomi Maruyama ◽  
Richard S. Selesnick
Keyword(s):  
Electric Field ◽  
Local Time ◽  
Large Scale ◽  
Radiation Belt ◽  
Energetic Electron ◽  
Recent Analysis ◽  
Quiet Time ◽  
Time Asymmetry ◽  
Electron Intensity

Recent analysis of energetic electron measurements from the Magnetic Electron Ion Spectrometer instruments onboard the Van Allen Probes showed a local time variation of the equatorial electron intensity in the Earth’s inner radiation belt. The local time asymmetry was interpreted as evidence of drift shell distortion by a large-scale electric field. It was also demonstrated that the inclusion of a simple dawn-to-dusk electric field model improved the agreement between observations and theoretical expectations. Yet, exactly what drives this electric field was left unexplained. We combine in-situ field and particle observations, together with a physics-based coupled model, the Rice Convection Model (RCM) Coupled Thermosphere-Ionosphere-Plasmasphere-electrodynamics (CTIPe), to revisit the local time asymmetry of the equatorial electron intensity observed in the innermost radiation belt. The study is based on the dawn-dusk difference in equatorial electron intensity measured at L = 1.30 during the first 60 days of the year 2014. Analysis of measured equatorial electron intensity in the 150–400 keV energy range, in-situ DC electric field measurements and wind dynamo modeling outputs provide consistent estimates of the order of 6–8 kV for the average dawn-to-dusk electric potential variation. This suggests that the dynamo electric fields produced by tidal motion of upper atmospheric winds flowing across Earth’s magnetic field lines - the quiet time ionospheric wind dynamo - are the main drivers of the drift shell distortion in the Earth’s inner radiation belt.

scholarly journals The magnetic local time distribution of energetic electrons in the radiation belt region

2017 ◽  
Vol 122 (8) ◽  
pp. 8108-8123 ◽  
Author(s):  
Hayley J. Allison ◽  
Richard B. Horne ◽  
Sarah A. Glauert ◽  
Giulio Del Zanna
Keyword(s):  
Local Time ◽  
Time Distribution ◽  
Radiation Belt ◽  
Magnetic Local Time ◽  
Energetic Electrons

Ozone super recovery cancelled in the Antarctic upper stratosphere

2021 ◽  
Author(s):  
Ville Maliniemi ◽  
Pavle Arsenovic ◽  
Hilde Nesse Tyssøy ◽  
Christine Smith-Johnsen ◽  
Daniel R. Marsh
Keyword(s):  
21St Century ◽  
Radiative Forcing ◽  
Climate Model ◽  
Energetic Electron ◽  
Ozone Production ◽  
The Arctic ◽  
Future Scenarios ◽  
Antarctic Ozone ◽  
The Antarctic ◽  
Polar Ozone

<p>Ozone is expected to fully recover from the CFC-era by the end of the 21st century. Furthermore, because of the anthropogenic climate change, cooler stratosphere accelerates the ozone production and is projected to lead to a super recovery. We investigate the ozone distribution over the 21st century with four different future scenarios using simulations of the Whole Atmosphere Community Climate Model (WACCM). At the end of the 21st century, higher polar ozone levels than pre CFC-era are obtained in scenarios that have highest atmospheric radiative forcing. This is true in the Arctic stratosphere and the Antarctic lower stratosphere. The Antarctic upper stratosphere forms an exception, where different scenarios have similar level of ozone during winter. This results from excess nitrogen oxides (NOx) descending from above in stronger future scenarios. NOx is formed by energetic electron precipitation (EEP) in the thermosphere and the upper mesosphere, and descends faster through the mesosphere in stronger scenarios. This indicates that the EEP indirect effect will be important factor for the future Antarctic ozone evolution, and is potentially able to prevent the super recovery in the upper stratosphere.</p>

Investigating the dynamics of an Antarctic coastal polynya using a regional climate model

2020 ◽  
Author(s):  
Pierre-Vincent Huot ◽  
Thierry Fichefet ◽  
Christoph Kittel ◽  
Nicolas Jourdain ◽  
Xavier Fettweis
Keyword(s):  
Sea Ice ◽  
Climate Model ◽  
Regional Climate ◽  
Coupled Model ◽  
Polar Regions ◽  
Coupled Models ◽  
Polar Climate ◽  
Coastal Polynya ◽  
The Impact ◽  
Regional Coupled Model

<p>Coastal polynyas of the Southern Ocean, such as the Mertz Glacier Polynya, are paramount features of the polar climate. They allow for exchanges of heat, momentum and moisture between the atmosphere and ocean where sea ice usually prevents such interactions. Polynyas are believed to have a profound impact on polar and global climate, thanks to their sustained sea ice production and the associated formation of Dense Shelf Waters. Less is known, however, about the impact of polynyas on the atmosphere. Changes in air properties and winds induced by heat and moisture flux could for instance affect precipitation regime over the ice sheet or sea ice. As the formation and evolution of coastal polynyas are tied to the state of the atmosphere, such changes can also induce important feedbacks to polynyas dynamics. Such processes have almost never been studied, whether on the field or with the help of coupled models. Here, we propose to describe the behavior of a coastal polynya and its relationship with the ocean and atmosphere. To do so, we developed a regional coupled model of the ocean, sea ice and atmosphere (including interactive basal melt of ice shelves) and applied it to the Adélie Land area, in East Antarctica. The dynamics of the Mertz Glacier Polynya is described, together with its impact on the atmosphere, sea ice growth, dense water production and ice shelf melt. To assess the importance of potential feedbacks, we compare the dynamics of the polynya from the coupled model to a forced ocean-sea ice model. We then use the regional coupled model to investigate the implications of the Mertz ice tongue calving in early 2010 which led to a drastic decrease of the Mertz Glacier Polynya extent. This experiment aims at investigating the sensitivity of the atmosphere to the activity of the polynya and to evaluate the impact of the calving on regional climate. This work improves the understanding of the Mertz Glacier Polynya dynamics, and of the impact of coastal polynyas on polar climate. It also constitutes an additional step in the modelling of the polar regions in Earth System Models.</p>

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