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Craig J. Rodger - One of the best experts on this subject based on the ideXlab platform.
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evidence of sub mev emic driven Electron Precipitation
Geophysical Research Letters, 2017Co-Authors: Aaron T Hendry, Craig J. Rodger, Mark A ClilverdAbstract:Electromagnetic ion cyclotron (EMIC) waves are potentially important drivers of the loss of energetic Electrons from the radiation belts. Numerous theoretical calculations exist with conflicting predictions of one of the key parameters: the minimum resonance energy of Electrons precipitated into the atmosphere by EMIC waves. In this study we initially analyze an EMIC Electron Precipitation event using data from two different spacecraft instruments to investigate the energies involved. Combining observations from these satellites, we find that the Electron Precipitation has a peak flux at ∼250 keV. Extending the analysis technique to a previously published database of similar scattering events, we find that the peak Electron Precipitation flux occurs predominantly around 300 keV, with only ∼11% of events peaking in the 1–4 MeV range. Such a significant population of low-energy EMIC-driven Electron Precipitation events highlights the possibility for EMIC waves to be significant drivers of radiation belt Electron losses.
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1 POES Satellite Observations of EMIC-wave driven Relativistic Electron Precipitation during 1998-2010
2016Co-Authors: Bonar R Carson, Craig J. Rodger, Mark A ClilverdAbstract:Abstract. Using six satellites that have carried the SEM-2 instrument package, a total of 436,422 individual half orbits between 1998 and 2010 were inspected by an automatic detection algorithm searching for EMIC-driven relativistic Electron Precipitation (REP). The algorithm searched for one of the key characteristics of EMIC-driven REP, identified as the simultaneity between spikes in the P1 (52 keV differential proton flux channel) and P6 (>800 keV Electron channel). In all, 2,331 proton Precipitation associated REP (PPAREP) events were identified. The majority of events were observed at L-values within the outer radiation belt (3<L<7) and were more common in the dusk and night sectors as determined by MLT. The majority of events occurred outside the plasmasphere, at L-values ~1 Re greater than the plasmapause location determined from two different statistical models. The events make up a subset of EMIC-driven proton spikes investigated by Sandanger et al. [2009], and potentially reflect different overall characteristics compared with proton spikes, particularly when comparing their location to that of the plasmapause, i.e., EMIC-driven proton Precipitation inside the plasmapause, and potentially EMIC-driven REP outside the plasmapause. There was no clear relationship between the location of plasmaspheric plumes and the locations of the PPAREP events detected. Analysis of the PPAREP event occurrence indicates that high sola
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confirmation of emic wave driven relativistic Electron Precipitation
Journal of Geophysical Research, 2016Co-Authors: Aaron T Hendry, Michel Lessard, Ian R. Mann, Tero Raita, Craig J. Rodger, Mark A Clilverd, M J Engebretson, David K. MillingAbstract:Electromagnetic ion cyclotron (EMIC) waves are believed to be an important source of pitch angle scattering driven relativistic Electron loss from the radiation belts. To date, investigations of this Precipitation have been largely theoretical in nature, limited to calculations of Precipitation characteristics based on wave observations and small-scale studies. Large-scale investigation of EMIC wave-driven Electron Precipitation has been hindered by a lack of combined wave and Precipitation measurements. Analysis of Electron flux data from the POES (Polar Orbiting Environmental Satellites) spacecraft has been suggested as a means of investigating EMIC wave-driven Electron Precipitation characteristics, using a Precipitation signature particular to EMIC waves. Until now the lack of supporting wave measurements for these POES-detected Precipitation events has resulted in uncertainty regarding the driver of the Precipitation. In this paper we complete a statistical study comparing POES Precipitation measurements with wave data from several ground-based search coil magnetometers; we further present a case study examining the global nature of this Precipitation. We show that a significant proportion of the Precipitation events correspond with EMIC wave detections on the ground; for Precipitation events that occur directly over the magnetometers, this detection rate can be as high as 90%. Our results demonstrate that the Precipitation region is often stationary in magnetic local time, narrow in L, and close to the expected plasmapause position. Predominantly, the Precipitation is associated with helium band rising tone Pc1 waves on the ground. The success of this study proves the viability of POES Precipitation data for investigating EMIC wave-driven Electron Precipitation.
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high resolution in situ observations of Electron Precipitation causing emic waves
Geophysical Research Letters, 2015Co-Authors: Craig J. Rodger, Aaron T Hendry, J B Brundell, C. A. Kletzing, Mark A Clilverd, Geoffrey D. ReevesAbstract:Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic Electron losses from the outer radiation belt through Precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental Precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of EMIC waves, with satellite and ground-based observations of the EMIC-induced Electron Precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of EMIC-induced Electron Precipitation inferred from coincident Precipitation data and relate them to the EMIC wave frequency, wave power, and ion band of the wave as measured in situ by the Van Allen Probes. These observations will better constrain modeling into the importance of EMIC wave-particle interactions.
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substorm induced energetic Electron Precipitation impact on atmospheric chemistry
Geophysical Research Letters, 2015Co-Authors: Annika Seppala, Craig J. Rodger, Mark A Clilverd, P T Verronen, Mathew James Beharrell, M E Andersson, David A NewnhamAbstract:Magnetospheric substorms drive energetic Electron Precipitation into the Earth's atmosphere. We use the output from a substorm model to describe Electron Precipitation forcing of the atmosphere during an active substorm period in April–May 2007. We provide the first estimate of substorm impact on the neutral composition of the polar middle atmosphere. Model simulations show that the enhanced ionization from a series of substorms leads to an estimated ozone loss of 5–50% in the mesospheric column depending on season. This is similar in scale to small to medium solar proton events (SPEs). This effect on polar ozone balance is potentially more important on long time scales (months to years) than the impulsive but sporadic (few SPE/year versus three to four substorms/day) effect of SPEs. Our results suggest that substorms should be considered an important source of energetic particle Precipitation into the atmosphere and included in high-top chemistry-climate models.
Mark A Clilverd - One of the best experts on this subject based on the ideXlab platform.
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evidence of sub mev emic driven Electron Precipitation
Geophysical Research Letters, 2017Co-Authors: Aaron T Hendry, Craig J. Rodger, Mark A ClilverdAbstract:Electromagnetic ion cyclotron (EMIC) waves are potentially important drivers of the loss of energetic Electrons from the radiation belts. Numerous theoretical calculations exist with conflicting predictions of one of the key parameters: the minimum resonance energy of Electrons precipitated into the atmosphere by EMIC waves. In this study we initially analyze an EMIC Electron Precipitation event using data from two different spacecraft instruments to investigate the energies involved. Combining observations from these satellites, we find that the Electron Precipitation has a peak flux at ∼250 keV. Extending the analysis technique to a previously published database of similar scattering events, we find that the peak Electron Precipitation flux occurs predominantly around 300 keV, with only ∼11% of events peaking in the 1–4 MeV range. Such a significant population of low-energy EMIC-driven Electron Precipitation events highlights the possibility for EMIC waves to be significant drivers of radiation belt Electron losses.
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1 POES Satellite Observations of EMIC-wave driven Relativistic Electron Precipitation during 1998-2010
2016Co-Authors: Bonar R Carson, Craig J. Rodger, Mark A ClilverdAbstract:Abstract. Using six satellites that have carried the SEM-2 instrument package, a total of 436,422 individual half orbits between 1998 and 2010 were inspected by an automatic detection algorithm searching for EMIC-driven relativistic Electron Precipitation (REP). The algorithm searched for one of the key characteristics of EMIC-driven REP, identified as the simultaneity between spikes in the P1 (52 keV differential proton flux channel) and P6 (>800 keV Electron channel). In all, 2,331 proton Precipitation associated REP (PPAREP) events were identified. The majority of events were observed at L-values within the outer radiation belt (3<L<7) and were more common in the dusk and night sectors as determined by MLT. The majority of events occurred outside the plasmasphere, at L-values ~1 Re greater than the plasmapause location determined from two different statistical models. The events make up a subset of EMIC-driven proton spikes investigated by Sandanger et al. [2009], and potentially reflect different overall characteristics compared with proton spikes, particularly when comparing their location to that of the plasmapause, i.e., EMIC-driven proton Precipitation inside the plasmapause, and potentially EMIC-driven REP outside the plasmapause. There was no clear relationship between the location of plasmaspheric plumes and the locations of the PPAREP events detected. Analysis of the PPAREP event occurrence indicates that high sola
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confirmation of emic wave driven relativistic Electron Precipitation
Journal of Geophysical Research, 2016Co-Authors: Aaron T Hendry, Michel Lessard, Ian R. Mann, Tero Raita, Craig J. Rodger, Mark A Clilverd, M J Engebretson, David K. MillingAbstract:Electromagnetic ion cyclotron (EMIC) waves are believed to be an important source of pitch angle scattering driven relativistic Electron loss from the radiation belts. To date, investigations of this Precipitation have been largely theoretical in nature, limited to calculations of Precipitation characteristics based on wave observations and small-scale studies. Large-scale investigation of EMIC wave-driven Electron Precipitation has been hindered by a lack of combined wave and Precipitation measurements. Analysis of Electron flux data from the POES (Polar Orbiting Environmental Satellites) spacecraft has been suggested as a means of investigating EMIC wave-driven Electron Precipitation characteristics, using a Precipitation signature particular to EMIC waves. Until now the lack of supporting wave measurements for these POES-detected Precipitation events has resulted in uncertainty regarding the driver of the Precipitation. In this paper we complete a statistical study comparing POES Precipitation measurements with wave data from several ground-based search coil magnetometers; we further present a case study examining the global nature of this Precipitation. We show that a significant proportion of the Precipitation events correspond with EMIC wave detections on the ground; for Precipitation events that occur directly over the magnetometers, this detection rate can be as high as 90%. Our results demonstrate that the Precipitation region is often stationary in magnetic local time, narrow in L, and close to the expected plasmapause position. Predominantly, the Precipitation is associated with helium band rising tone Pc1 waves on the ground. The success of this study proves the viability of POES Precipitation data for investigating EMIC wave-driven Electron Precipitation.
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high resolution in situ observations of Electron Precipitation causing emic waves
Geophysical Research Letters, 2015Co-Authors: Craig J. Rodger, Aaron T Hendry, J B Brundell, C. A. Kletzing, Mark A Clilverd, Geoffrey D. ReevesAbstract:Electromagnetic ion cyclotron (EMIC) waves are thought to be important drivers of energetic Electron losses from the outer radiation belt through Precipitation into the atmosphere. While the theoretical possibility of pitch angle scattering-driven losses from these waves has been recognized for more than four decades, there have been limited experimental Precipitation observations to support this concept. We have combined satellite-based observations of the characteristics of EMIC waves, with satellite and ground-based observations of the EMIC-induced Electron Precipitation. In a detailed case study, supplemented by an additional four examples, we are able to constrain for the first time the location, size, and energy range of EMIC-induced Electron Precipitation inferred from coincident Precipitation data and relate them to the EMIC wave frequency, wave power, and ion band of the wave as measured in situ by the Van Allen Probes. These observations will better constrain modeling into the importance of EMIC wave-particle interactions.
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substorm induced energetic Electron Precipitation impact on atmospheric chemistry
Geophysical Research Letters, 2015Co-Authors: Annika Seppala, Craig J. Rodger, Mark A Clilverd, P T Verronen, Mathew James Beharrell, M E Andersson, David A NewnhamAbstract:Magnetospheric substorms drive energetic Electron Precipitation into the Earth's atmosphere. We use the output from a substorm model to describe Electron Precipitation forcing of the atmosphere during an active substorm period in April–May 2007. We provide the first estimate of substorm impact on the neutral composition of the polar middle atmosphere. Model simulations show that the enhanced ionization from a series of substorms leads to an estimated ozone loss of 5–50% in the mesospheric column depending on season. This is similar in scale to small to medium solar proton events (SPEs). This effect on polar ozone balance is potentially more important on long time scales (months to years) than the impulsive but sporadic (few SPE/year versus three to four substorms/day) effect of SPEs. Our results suggest that substorms should be considered an important source of energetic particle Precipitation into the atmosphere and included in high-top chemistry-climate models.
Annika Seppala - One of the best experts on this subject based on the ideXlab platform.
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substorm induced energetic Electron Precipitation impact on atmospheric chemistry
Geophysical Research Letters, 2015Co-Authors: Annika Seppala, Craig J. Rodger, Mark A Clilverd, P T Verronen, Mathew James Beharrell, M E Andersson, David A NewnhamAbstract:Magnetospheric substorms drive energetic Electron Precipitation into the Earth's atmosphere. We use the output from a substorm model to describe Electron Precipitation forcing of the atmosphere during an active substorm period in April–May 2007. We provide the first estimate of substorm impact on the neutral composition of the polar middle atmosphere. Model simulations show that the enhanced ionization from a series of substorms leads to an estimated ozone loss of 5–50% in the mesospheric column depending on season. This is similar in scale to small to medium solar proton events (SPEs). This effect on polar ozone balance is potentially more important on long time scales (months to years) than the impulsive but sporadic (few SPE/year versus three to four substorms/day) effect of SPEs. Our results suggest that substorms should be considered an important source of energetic particle Precipitation into the atmosphere and included in high-top chemistry-climate models.
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missing driver in the sun earth connection from energetic Electron Precipitation impacts mesospheric ozone
Nature Communications, 2014Co-Authors: M E Andersso, P T Verrone, Craig J Rodge, Mark A Clilverd, Annika SeppalaAbstract:Energetic Electron Precipitation (EEP) from the Earth's outer radiation belt can lead to ozone loss in the mesosphere, yet long-term variability has not been quantified. Here, the authors present satellite observations and show that on solar cycle timescales EEP causes ozone to vary by up to 34%.
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direct observations of nitric oxide produced by energetic Electron Precipitation into the antarctic middle atmosphere
Geophysical Research Letters, 2011Co-Authors: David A Newnham, Craig J. Rodger, Mark A Clilverd, Annika Seppala, P J Espy, David J Maxfield, P Hartogh, Kim Holmen, Richard B HorneAbstract:[1] We report the first ground-based passive microwave observations made from Troll station, Antarctica, which show enhanced mesospheric nitric oxide (NO) volume mixing ratio reaching levels of 1.2 ppmv, or 2–3 orders of magnitude above background, at 70–80 km during small, relatively isolated geomagnetic storms in 2008. The mesospheric NO peaked 2 days after enhanced NO at higher altitudes (110–150 km) measured by the SABER satellite, and 2 days after peaks in the >30 keV and >300 keV Electron flux measured by POES, although the 300 keV Electron flux remained high. High time resolution data shows that mesospheric NO was enhanced at night and decayed during the day and built up to high levels over a period of 3–4 days. The altitude profile of mesospheric NO suggests direct production by ∼300 keV Electron Precipitation. Simulations using the Sodankyla Ion and Neutral Chemistry model show that the delay between thermospheric and mesospheric NO enhancements was primarily a result of the weaker production rate at lower altitudes by ∼300 keV Electrons competing against strong day-time losses.
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ground based estimates of outer radiation belt energetic Electron Precipitation fluxes into the atmosphere
Journal of Geophysical Research, 2010Co-Authors: Mark A Clilverd, Thomas Ulich, Tero Raita, J. C. Green, Craig J. Rodger, Annika Seppala, Neil R Thomson, Rory J. Gamble, Jean‐andré SauvaudAbstract:[1] AARDDVARK data from a radio wave receiver in Sodankyla, 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, 44°N, 67°W, 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 and 90 km. Our analysis of the NAA observations shows that Electron Precipitation fluxes can vary by 3 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 ground‐based >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.
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Radiation belt Electron Precipitation due to geomagnetic storms: Significance to middle atmosphere ozone chemistry
Journal of Geophysical Research Space Physics, 2010Co-Authors: Craig J. Rodger, Mark A Clilverd, Annika Seppala, N.r. Thomson, Michel Parrot, Rory J. Gamble, Jean‐andré Sauvaud, Thomas UlichAbstract:[1] Geomagnetic storms triggered by coronal mass ejections and high‐speed solar wind streams can lead to enhanced losses of energetic Electrons from the radiation belts into the atmosphere, both during the storm itself and also through the poststorm relaxation of enhanced radiation belt fluxes. In this study we have analyzed the impact of Electron Precipitation on atmospheric chemistry (30–90 km altitudes) as a result of a single geomagnetic storm. The study conditions were chosen such that there was no influence of solar proton Precipitation, and thus we were able to determine the storm‐induced outer radiation belt Electron Precipitation fluxes. We use ground‐based subionospheric radio wave observations to infer the Electron Precipitation fluxes at L = 3.2 during a geomagnetic disturbance which occurred in September 2005. Through application of the Sodankylä Ion and Neutral Chemistry model, we examine the significance of this particular period of Electron Precipitation to neutral atmospheric chemistry. Building on an earlier study, we refine the quantification of the Electron Precipitation flux into the atmosphere by using a time‐varying energy spectrum determined from the DEMETER satellite. We show that the large increases in odd nitrogen (NO x) and odd hydrogen (HO x) caused by the Electron Precipitation do not lead to significant in situ ozone depletion in September in the Northern Hemisphere. However, had the same Precipitation been deposited into the polar winter atmosphere, it would have led to >20% in situ decreases in O 3 at 65–80 km altitudes through catalytic HO x cycles, with possible additional stratospheric O 3 depletion from descending NO x beyond the model simulation period. Citation: Rodger, C. J., M. A. Clilverd, A. Seppälä, N. R. Thomson, R. J. Gamble, M. Parrot, J.‐A. Sauvaud, and T. Ulich (2010), Radiation belt Electron Precipitation due to geomagnetic storms: Significance to middle atmosphere ozone chemistry,
J. C. Green - One of the best experts on this subject based on the ideXlab platform.
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calculation of whistler mode wave intensity using energetic Electron Precipitation
URSI General Assembly and Scientific Symposium, 2014Co-Authors: R M Thorne, C. A. Kletzing, J. C. Green, J Bortnik, W S Kurth, G B HospodarskyAbstract:The energetic Electron population measured by multiple low-altitude POES satellites is used to infer whistlermode wave amplitudes using a physics-based inversion technique. We validate this technique by quantitatively analyzing a conjunction event between the Van Allen Probes and POES, and find that the inferred hiss wave amplitudes from POES Electron measurements agree remarkably well with directly measured hiss waves amplitudes. We also use this technique to construct the global distribution of chorus wave intensity with extensive coverage over a broad L-MLT region during the 8–9 October 2012 storm and demonstrate that the inferred chorus wave amplitudes agree well with conjugate measurements of chorus wave amplitudes from the Van Allen Probes. The evolution of the whistler-mode wave intensity inferred from low-altitude Electron measurements can provide real-time global estimates of the wave intensity, which cannot be obtained from in-situ wave measurements by equatorial satellites alone, but are crucial in quantifying radiation belt Electron dynamics.
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energetic Electron Precipitation during high speed solar wind stream driven storms
Journal of Geophysical Research, 2011Co-Authors: Nigel P Meredith, Richard B Horne, Mai Mai Lam, M H Denton, Joseph E Borovsky, J. C. GreenAbstract:Electron Precipitation from the Earth's inner magnetosphere transmits solar variability to the Earth's upper atmosphere and may affect surface level climate. Here we conduct a superposed epoch analysis of energetic Electrons observed by the NOAA POES spacecraft during 42 high-speed solar wind stream (HSS) driven geomagnetic storms to determine the temporal evolution and global distribution of the precipitating flux. The flux of trapped and precipitating E > 30 keV Electrons increases immediately following storm onset and remains elevated during the passage of the HSS. In contrast, the trapped and precipitating relativistic Electrons (E > 1 MeV) drop out following storm onset and subsequently increase during the recovery phase to levels which eventually exceed the prestorm levels. There is no evidence for enhanced Precipitation of relativistic Electrons during the MeV flux drop out, suggesting that flux drop outs during the main phase of HSS-driven storms are not due to Precipitation to the atmosphere. On average, the flux of precipitating E > 30 keV Electrons is enhanced by a factor of similar to 10 during the passage of the high-speed stream at all geographic longitudes. In contrast, the precipitating relativistic Electron count rate is observed to peak in the region poleward of the South Atlantic Anomaly. During the passage of the high-speed stream, the flux of precipitating E > 30 keV Electrons peaks in the region from 2100 to 1200 magnetic local time at low L (4 30 keV Electrons in both regions.
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ground based estimates of outer radiation belt energetic Electron Precipitation fluxes into the atmosphere
Journal of Geophysical Research, 2010Co-Authors: Mark A Clilverd, Thomas Ulich, Tero Raita, J. C. Green, Craig J. Rodger, Annika Seppala, Neil R Thomson, Rory J. Gamble, Jean‐andré SauvaudAbstract:[1] AARDDVARK data from a radio wave receiver in Sodankyla, 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, 44°N, 67°W, 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 and 90 km. Our analysis of the NAA observations shows that Electron Precipitation fluxes can vary by 3 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 ground‐based >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.
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energetic Electron Precipitation from the outer radiation belt during geomagnetic storms
Geophysical Research Letters, 2009Co-Authors: Richard B Horne, J. C. GreenAbstract:[1] Relativistic Electron Precipitation changes the chemistry of the upper atmosphere and depletes ozone, but the spatial and temporal distributions are poorly known. Here we survey more than 9 years of data from low altitude satellites for different phases of geomagnetic storms. We find that for the outer radiation belt, Electron Precipitation >300 keV peaks during the main phase of storms whereas that >1 MeV peaks during the recovery phase. Precipitation >300 keV can occur at all geographic longitudes in both hemispheres whereas that >1 MeV occurs mainly poleward of the South Atlantic anomaly (SAA) region. The data suggest that wave-particle interactions are strong enough to precipitate >300 keV Electrons into the bounce loss cone, but precipitate >1 MeV Electrons into the drift loss cone. We find that whistler mode chorus waves alone cannot account for the higher MeV Precipitation flux during the recovery phase. We suggest that whistler mode chorus waves accelerate Electrons up to MeV energies during the recovery phase which are then precipitated by EMIC waves. The effects on atmospheric chemistry due to MeV Electron Precipitation are more likely to occur in the southern hemisphere poleward of the SAA region with a delay of 1–2 days or more from the peak of the storm.
Richard B Horne - One of the best experts on this subject based on the ideXlab platform.
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direct observations of nitric oxide produced by energetic Electron Precipitation into the antarctic middle atmosphere
Geophysical Research Letters, 2011Co-Authors: David A Newnham, Craig J. Rodger, Mark A Clilverd, Annika Seppala, P J Espy, David J Maxfield, P Hartogh, Kim Holmen, Richard B HorneAbstract:[1] We report the first ground-based passive microwave observations made from Troll station, Antarctica, which show enhanced mesospheric nitric oxide (NO) volume mixing ratio reaching levels of 1.2 ppmv, or 2–3 orders of magnitude above background, at 70–80 km during small, relatively isolated geomagnetic storms in 2008. The mesospheric NO peaked 2 days after enhanced NO at higher altitudes (110–150 km) measured by the SABER satellite, and 2 days after peaks in the >30 keV and >300 keV Electron flux measured by POES, although the 300 keV Electron flux remained high. High time resolution data shows that mesospheric NO was enhanced at night and decayed during the day and built up to high levels over a period of 3–4 days. The altitude profile of mesospheric NO suggests direct production by ∼300 keV Electron Precipitation. Simulations using the Sodankyla Ion and Neutral Chemistry model show that the delay between thermospheric and mesospheric NO enhancements was primarily a result of the weaker production rate at lower altitudes by ∼300 keV Electrons competing against strong day-time losses.
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energetic Electron Precipitation during high speed solar wind stream driven storms
Journal of Geophysical Research, 2011Co-Authors: Nigel P Meredith, Richard B Horne, Mai Mai Lam, M H Denton, Joseph E Borovsky, J. C. GreenAbstract:Electron Precipitation from the Earth's inner magnetosphere transmits solar variability to the Earth's upper atmosphere and may affect surface level climate. Here we conduct a superposed epoch analysis of energetic Electrons observed by the NOAA POES spacecraft during 42 high-speed solar wind stream (HSS) driven geomagnetic storms to determine the temporal evolution and global distribution of the precipitating flux. The flux of trapped and precipitating E > 30 keV Electrons increases immediately following storm onset and remains elevated during the passage of the HSS. In contrast, the trapped and precipitating relativistic Electrons (E > 1 MeV) drop out following storm onset and subsequently increase during the recovery phase to levels which eventually exceed the prestorm levels. There is no evidence for enhanced Precipitation of relativistic Electrons during the MeV flux drop out, suggesting that flux drop outs during the main phase of HSS-driven storms are not due to Precipitation to the atmosphere. On average, the flux of precipitating E > 30 keV Electrons is enhanced by a factor of similar to 10 during the passage of the high-speed stream at all geographic longitudes. In contrast, the precipitating relativistic Electron count rate is observed to peak in the region poleward of the South Atlantic Anomaly. During the passage of the high-speed stream, the flux of precipitating E > 30 keV Electrons peaks in the region from 2100 to 1200 magnetic local time at low L (4 30 keV Electrons in both regions.
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energetic Electron Precipitation from the outer radiation belt during geomagnetic storms
Geophysical Research Letters, 2009Co-Authors: Richard B Horne, J. C. GreenAbstract:[1] Relativistic Electron Precipitation changes the chemistry of the upper atmosphere and depletes ozone, but the spatial and temporal distributions are poorly known. Here we survey more than 9 years of data from low altitude satellites for different phases of geomagnetic storms. We find that for the outer radiation belt, Electron Precipitation >300 keV peaks during the main phase of storms whereas that >1 MeV peaks during the recovery phase. Precipitation >300 keV can occur at all geographic longitudes in both hemispheres whereas that >1 MeV occurs mainly poleward of the South Atlantic anomaly (SAA) region. The data suggest that wave-particle interactions are strong enough to precipitate >300 keV Electrons into the bounce loss cone, but precipitate >1 MeV Electrons into the drift loss cone. We find that whistler mode chorus waves alone cannot account for the higher MeV Precipitation flux during the recovery phase. We suggest that whistler mode chorus waves accelerate Electrons up to MeV energies during the recovery phase which are then precipitated by EMIC waves. The effects on atmospheric chemistry due to MeV Electron Precipitation are more likely to occur in the southern hemisphere poleward of the SAA region with a delay of 1–2 days or more from the peak of the storm.