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Kyle R. Murphy - One of the best experts on this subject based on the ideXlab platform.
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An explanation of auroral intensification during the substorm Expansion Phase
Journal of Geophysical Research: Space Physics, 2017Co-Authors: Zhonghua Yao, I. J. Rae, Anthony T. Y. Lui, Kyle R. Murphy, Christopher J. Owen, Colin Forsyth, Denis Grodent, Q. G. ZongAbstract:A multiple auroral onset substorm on 28 March 2010 provides an opportunity to understand the physical mechanism in generating auroral intensifications during a substorm Expansion Phase. Conjugate observations of magnetic fields and plasma from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft, of field-aligned currents (FACs) from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) satellites, and from ground-based magnetometers and aurora are all available. The comprehensive measurements allow us to further our understanding of the complicated causalities amongst dipolarization, FAC generation, particle acceleration and auroral intensification. During the substorm Expansion Phase, the plasma sheet expanded and was perturbed leading to the generation of a slow mode wave, which modulated electron flux in the outer plasma sheet. During this current sheet Expansion, field-aligned currents formed, and geomagnetic perturbations were simultaneously detected by ground-based instruments. However, a magnetic dipolarization did not occur until about 3 minutes later in the outer plasma sheet observed by THEMIS-A spacecraft (THA). We believe this dipolarization led to an efficient Fermi acceleration to electrons, and consequently the cause of a significant auroral intensification during the Expansion Phase as observed by the All-Sky Imagers (ASIs). This Fermi acceleration mechanism operating efficiently in the outer plasma sheet during the Expansion Phase could be a common explanation of the poleward auroral development after substorm onset. These results also show a good agreement between the upward FAC derived from AMPERE measurements and the auroral brightening observed by the ASIs.
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Automated determination of auroral breakup during the substorm Expansion Phase using all‐sky imager data
Journal of Geophysical Research: Space Physics, 2014Co-Authors: Kyle R. Murphy, Ian R. Mann, Clare E. J. Watt, I. Jonathan Rae, David M. Miles, Harald U. FreyAbstract:This paper describes a novel method for quantitatively and routinely identifying auroral breakup following substorm onset using the Time History of Events and Macroscale Interactions during Substorms all-sky imagers. Substorm onset is characterized by a brightening of the aurora that is followed by auroral poleward Expansion and auroral breakup. This breakup can be identified by a sharp increase in the auroral intensity i(t) and the time derivative of auroral intensity i(t). Utilizing both i(t) and i'(t), we have developed an algorithm for identifying the time interval and spatial location of auroral breakup during the substorm Expansion Phase based solely on quantifiable characteristics of the optical auroral emissions. We compare the time interval determined by the algorithm to independently identified auroral onset times from three previously published studies. In each case the time interval determined by the algorithm is within error of the onset independently identified by the prior studies. We further show the utility of the algorithm by comparing the breakup intervals determined using the automated algorithm to an independent list of substorm onset times. We demonstrate that 50% of the breakup intervals characterized by the algorithm are within the uncertainty of the times identified in the list. The quantitative description and routine identification of an interval of auroral brightening during the substorm Expansion Phase provides a foundation for unbiased statistical analysis of the aurora and to probe the physics of the auroral substorm and identify the processes leading to auroral substorm onset.
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The detailed spatial structure of field‐aligned currents comprising the substorm current wedge
Journal of Geophysical Research: Space Physics, 2013Co-Authors: Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Howard J. Singer, I. Jonathan Rae, A. Kale, C L Waters, B J Anderson, Haje KorthAbstract:[1] We present a comprehensive two-dimensional view of the field-aligned currents (FACs) during the late growth and Expansion Phases for three isolated substorms utilizing in situ observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and from ground-based magnetometer and optical instrumentation from the Canadian Array for Realtime Investigations of Magnetic Activity and Time History of Events and Macroscale Interactions during Substorms ground-based arrays. We demonstrate that the structure of FACs formed during the Expansion Phase and associated with the substorm current wedge is significantly more complex than a simple equivalent line current model comprising a downward FAC in the east and upward FAC in the west. This two-dimensional view demonstrates that azimuthal bands of upward and downward FACs with periodic structuring in latitude form across midnight and can span up to 8 h of magnetic local time. However, when averaged over latitude, the overall longitudinal structure of the net FACs resembles the simpler equivalent line current description of the substorm current wedge (SCW). In addition, we demonstrate that the upward FAC elements of the structured SCW are spatially very well correlated with discrete aurora during the substorm Expansion Phase and that discrete changes in the FAC topology are observed in the late growth Phase prior to auroral substorm Expansion Phase onset. These observations have important implications for determining how the magnetosphere and ionosphere couple during the late growth Phase and Expansion Phase, as well as providing important constraints on the magnetospheric generator of the FACs comprising the SCW.
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the detailed spatial structure of field aligned currents comprising the substorm current wedge
Journal of Geophysical Research, 2013Co-Authors: Kyle R. Murphy, A. Kale, H U Frey, I R Mann, Jonathan I Rae, C L Waters, H J Singer, B J Anderson, Haje KorthAbstract:[1] We present a comprehensive two-dimensional view of the field-aligned currents (FACs) during the late growth and Expansion Phases for three isolated substorms utilizing in situ observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and from ground-based magnetometer and optical instrumentation from the Canadian Array for Realtime Investigations of Magnetic Activity and Time History of Events and Macroscale Interactions during Substorms ground-based arrays. We demonstrate that the structure of FACs formed during the Expansion Phase and associated with the substorm current wedge is significantly more complex than a simple equivalent line current model comprising a downward FAC in the east and upward FAC in the west. This two-dimensional view demonstrates that azimuthal bands of upward and downward FACs with periodic structuring in latitude form across midnight and can span up to 8 h of magnetic local time. However, when averaged over latitude, the overall longitudinal structure of the net FACs resembles the simpler equivalent line current description of the substorm current wedge (SCW). In addition, we demonstrate that the upward FAC elements of the structured SCW are spatially very well correlated with discrete aurora during the substorm Expansion Phase and that discrete changes in the FAC topology are observed in the late growth Phase prior to auroral substorm Expansion Phase onset. These observations have important implications for determining how the magnetosphere and ionosphere couple during the late growth Phase and Expansion Phase, as well as providing important constraints on the magnetospheric generator of the FACs comprising the SCW.
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The correlation of ULF waves and auroral intensity before, during and after substorm Expansion Phase onset
Journal of Geophysical Research: Space Physics, 2012Co-Authors: I. Jonathan Rae, Kyle R. Murphy, Harald U. Frey, Clare E. J. Watt, David K. Milling, Louis G. Ozeke, Ian R. MannAbstract:[1] We present case studies of the evolution of Ultra-Low Frequency (ULF) magnetic wave amplitudes and auroral intensity through the late growth Phase and the Expansion Phase of the substorm cycle. We present strong evidence that substorm-related auroral enhancements are clearly and demonstrably linked to ULF wave amplitudes observed at the same location. In all three case studies presented, the correlation analysis shows that the ULF wave activity and auroral intensities are highly correlated at close to zero lag. We discuss four possible explanations that may be able to explain both the timing and the high correlations between these two phenomena, including a simple coincidence, an artifact of instrumental effects, the response of the ionosphere to magnetic waves and auroral particle precipitation, and finally, that ULF waves and auroral particle precipitation are physically linked at their source. We discount coincidence and instrumental effects since we present multiple events where instrumental effects have a negligible contribution, and we find that the ionospheric response to waves and precipitation can explain some, but not all, of the results contained within this paper. Specifically, the ionospheric response to substorm waves and auroral precipitation cannot explain the result backed up by previous studies that the onset of ULF wave activity and the onset of auroral particle precipitation occur at the same time and in the same location. This leaves the possibility that ULF waves and auroral particles are physically linked at their source. We therefore re-emphasize the importance of ULF wave observations in fully understanding the mechanism or mechanisms responsible for rapid auroral brightenings.
Harald U. Frey - One of the best experts on this subject based on the ideXlab platform.
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Automated determination of auroral breakup during the substorm Expansion Phase using all‐sky imager data
Journal of Geophysical Research: Space Physics, 2014Co-Authors: Kyle R. Murphy, Ian R. Mann, Clare E. J. Watt, I. Jonathan Rae, David M. Miles, Harald U. FreyAbstract:This paper describes a novel method for quantitatively and routinely identifying auroral breakup following substorm onset using the Time History of Events and Macroscale Interactions during Substorms all-sky imagers. Substorm onset is characterized by a brightening of the aurora that is followed by auroral poleward Expansion and auroral breakup. This breakup can be identified by a sharp increase in the auroral intensity i(t) and the time derivative of auroral intensity i(t). Utilizing both i(t) and i'(t), we have developed an algorithm for identifying the time interval and spatial location of auroral breakup during the substorm Expansion Phase based solely on quantifiable characteristics of the optical auroral emissions. We compare the time interval determined by the algorithm to independently identified auroral onset times from three previously published studies. In each case the time interval determined by the algorithm is within error of the onset independently identified by the prior studies. We further show the utility of the algorithm by comparing the breakup intervals determined using the automated algorithm to an independent list of substorm onset times. We demonstrate that 50% of the breakup intervals characterized by the algorithm are within the uncertainty of the times identified in the list. The quantitative description and routine identification of an interval of auroral brightening during the substorm Expansion Phase provides a foundation for unbiased statistical analysis of the aurora and to probe the physics of the auroral substorm and identify the processes leading to auroral substorm onset.
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The detailed spatial structure of field‐aligned currents comprising the substorm current wedge
Journal of Geophysical Research: Space Physics, 2013Co-Authors: Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Howard J. Singer, I. Jonathan Rae, A. Kale, C L Waters, B J Anderson, Haje KorthAbstract:[1] We present a comprehensive two-dimensional view of the field-aligned currents (FACs) during the late growth and Expansion Phases for three isolated substorms utilizing in situ observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and from ground-based magnetometer and optical instrumentation from the Canadian Array for Realtime Investigations of Magnetic Activity and Time History of Events and Macroscale Interactions during Substorms ground-based arrays. We demonstrate that the structure of FACs formed during the Expansion Phase and associated with the substorm current wedge is significantly more complex than a simple equivalent line current model comprising a downward FAC in the east and upward FAC in the west. This two-dimensional view demonstrates that azimuthal bands of upward and downward FACs with periodic structuring in latitude form across midnight and can span up to 8 h of magnetic local time. However, when averaged over latitude, the overall longitudinal structure of the net FACs resembles the simpler equivalent line current description of the substorm current wedge (SCW). In addition, we demonstrate that the upward FAC elements of the structured SCW are spatially very well correlated with discrete aurora during the substorm Expansion Phase and that discrete changes in the FAC topology are observed in the late growth Phase prior to auroral substorm Expansion Phase onset. These observations have important implications for determining how the magnetosphere and ionosphere couple during the late growth Phase and Expansion Phase, as well as providing important constraints on the magnetospheric generator of the FACs comprising the SCW.
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The correlation of ULF waves and auroral intensity before, during and after substorm Expansion Phase onset
Journal of Geophysical Research: Space Physics, 2012Co-Authors: I. Jonathan Rae, Kyle R. Murphy, Harald U. Frey, Clare E. J. Watt, David K. Milling, Louis G. Ozeke, Ian R. MannAbstract:[1] We present case studies of the evolution of Ultra-Low Frequency (ULF) magnetic wave amplitudes and auroral intensity through the late growth Phase and the Expansion Phase of the substorm cycle. We present strong evidence that substorm-related auroral enhancements are clearly and demonstrably linked to ULF wave amplitudes observed at the same location. In all three case studies presented, the correlation analysis shows that the ULF wave activity and auroral intensities are highly correlated at close to zero lag. We discuss four possible explanations that may be able to explain both the timing and the high correlations between these two phenomena, including a simple coincidence, an artifact of instrumental effects, the response of the ionosphere to magnetic waves and auroral particle precipitation, and finally, that ULF waves and auroral particle precipitation are physically linked at their source. We discount coincidence and instrumental effects since we present multiple events where instrumental effects have a negligible contribution, and we find that the ionospheric response to waves and precipitation can explain some, but not all, of the results contained within this paper. Specifically, the ionospheric response to substorm waves and auroral precipitation cannot explain the result backed up by previous studies that the onset of ULF wave activity and the onset of auroral particle precipitation occur at the same time and in the same location. This leaves the possibility that ULF waves and auroral particles are physically linked at their source. We therefore re-emphasize the importance of ULF wave observations in fully understanding the mechanism or mechanisms responsible for rapid auroral brightenings.
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Seasonal and interplanetary magnetic field–dependent polar cap contraction during substorm Expansion Phase
Journal of Geophysical Research: Space Physics, 2010Co-Authors: Karl Magnus Laundal, Nikolai Østgaard, Harald U. Frey, James M. WeygandAbstract:[1] Recent observations from simultaneous imaging in two hemispheres have shown that the polar caps can attain considerably different shapes as the auroral ovals contract during the substorm Expansion Phase. We use images from 2770 substorms to study the evolution of the polar cap boundary location statistically. We show that, during the first 26 min after substorm Expansion Phase onset, the polar cap boundary location depends on seasons, interplanetary magnetic field (IMF) By, and IMF Bx. For different signs of By, with ∣By∣ > 3 nT, the asymmetry in polar cap boundary observed at onset increases during the Expansion Phase, consistent with an increase in tail reconnection of field lines with asymmetrical footpoints. When Bx > 2 nT and ∣By∣ < 2 nT, the polar cap boundary dawnward of the onset propagates slightly farther poleward compared to negative Bx conditions. In the sunlit hemisphere, the polar cap boundary evolves from a pronounced equatorward displacement at onset to an almost reversed displacement during the Expansion Phase, compared to substorms observed in darkness. Substorms in the dark hemisphere also have a much more pronounced bulge than substorms in the sunlit hemisphere. If the interpretation of the poleward auroral boundary as being coincident with the open/closed field line boundary (OCB) is correct, the seasonal differences in OCB locations imply seasonal differences in the ionospheric convection during the substorm Expansion Phase.
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Wavelet‐based ULF wave diagnosis of substorm Expansion Phase onset
Journal of Geophysical Research, 2009Co-Authors: Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Clare E. J. Watt, I. Jonathan Rae, David K. Milling, Vassilis Angelopoulos, Louis G. Ozeke, Christopher T. RussellAbstract:[1] Using a discrete wavelet transform with a Meyer wavelet basis, we present a new quantitative algorithm for determining the onset time of Pi1 and Pi2 ULF waves in the nightside ionosphere with � 20- to 40-s resolution at substorm Expansion Phase onset. We validate the algorithm by comparing both the ULF wave onset time and location to the optical onset determined by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE)–Far Ultraviolet Imager (FUV) instrument. In each of the six events analyzed, five substorm onsets and one pseudobreakup, the ULF onset is observed prior to the global optical onset observed by IMAGE at a station closely conjugate to the optical onset. The observed ULF onset times expand both latitudinally and longitudinally away from an epicenter of ULF wave power in the ionosphere. We further discuss the utility of the algorithm for diagnosing pseudobreakups and the relationship of the ULF onset epicenter to the meridians of elements of the substorm current wedge. The importance of the technique for establishing the causal sequence of events at substorm onset, especially in support of the multisatellite Time History of Events and Macroscale Interactions During Substorms (THEMIS) mission, is also described.
Ian R. Mann - One of the best experts on this subject based on the ideXlab platform.
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Automated determination of auroral breakup during the substorm Expansion Phase using all‐sky imager data
Journal of Geophysical Research: Space Physics, 2014Co-Authors: Kyle R. Murphy, Ian R. Mann, Clare E. J. Watt, I. Jonathan Rae, David M. Miles, Harald U. FreyAbstract:This paper describes a novel method for quantitatively and routinely identifying auroral breakup following substorm onset using the Time History of Events and Macroscale Interactions during Substorms all-sky imagers. Substorm onset is characterized by a brightening of the aurora that is followed by auroral poleward Expansion and auroral breakup. This breakup can be identified by a sharp increase in the auroral intensity i(t) and the time derivative of auroral intensity i(t). Utilizing both i(t) and i'(t), we have developed an algorithm for identifying the time interval and spatial location of auroral breakup during the substorm Expansion Phase based solely on quantifiable characteristics of the optical auroral emissions. We compare the time interval determined by the algorithm to independently identified auroral onset times from three previously published studies. In each case the time interval determined by the algorithm is within error of the onset independently identified by the prior studies. We further show the utility of the algorithm by comparing the breakup intervals determined using the automated algorithm to an independent list of substorm onset times. We demonstrate that 50% of the breakup intervals characterized by the algorithm are within the uncertainty of the times identified in the list. The quantitative description and routine identification of an interval of auroral brightening during the substorm Expansion Phase provides a foundation for unbiased statistical analysis of the aurora and to probe the physics of the auroral substorm and identify the processes leading to auroral substorm onset.
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The detailed spatial structure of field‐aligned currents comprising the substorm current wedge
Journal of Geophysical Research: Space Physics, 2013Co-Authors: Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Howard J. Singer, I. Jonathan Rae, A. Kale, C L Waters, B J Anderson, Haje KorthAbstract:[1] We present a comprehensive two-dimensional view of the field-aligned currents (FACs) during the late growth and Expansion Phases for three isolated substorms utilizing in situ observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and from ground-based magnetometer and optical instrumentation from the Canadian Array for Realtime Investigations of Magnetic Activity and Time History of Events and Macroscale Interactions during Substorms ground-based arrays. We demonstrate that the structure of FACs formed during the Expansion Phase and associated with the substorm current wedge is significantly more complex than a simple equivalent line current model comprising a downward FAC in the east and upward FAC in the west. This two-dimensional view demonstrates that azimuthal bands of upward and downward FACs with periodic structuring in latitude form across midnight and can span up to 8 h of magnetic local time. However, when averaged over latitude, the overall longitudinal structure of the net FACs resembles the simpler equivalent line current description of the substorm current wedge (SCW). In addition, we demonstrate that the upward FAC elements of the structured SCW are spatially very well correlated with discrete aurora during the substorm Expansion Phase and that discrete changes in the FAC topology are observed in the late growth Phase prior to auroral substorm Expansion Phase onset. These observations have important implications for determining how the magnetosphere and ionosphere couple during the late growth Phase and Expansion Phase, as well as providing important constraints on the magnetospheric generator of the FACs comprising the SCW.
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The correlation of ULF waves and auroral intensity before, during and after substorm Expansion Phase onset
Journal of Geophysical Research: Space Physics, 2012Co-Authors: I. Jonathan Rae, Kyle R. Murphy, Harald U. Frey, Clare E. J. Watt, David K. Milling, Louis G. Ozeke, Ian R. MannAbstract:[1] We present case studies of the evolution of Ultra-Low Frequency (ULF) magnetic wave amplitudes and auroral intensity through the late growth Phase and the Expansion Phase of the substorm cycle. We present strong evidence that substorm-related auroral enhancements are clearly and demonstrably linked to ULF wave amplitudes observed at the same location. In all three case studies presented, the correlation analysis shows that the ULF wave activity and auroral intensities are highly correlated at close to zero lag. We discuss four possible explanations that may be able to explain both the timing and the high correlations between these two phenomena, including a simple coincidence, an artifact of instrumental effects, the response of the ionosphere to magnetic waves and auroral particle precipitation, and finally, that ULF waves and auroral particle precipitation are physically linked at their source. We discount coincidence and instrumental effects since we present multiple events where instrumental effects have a negligible contribution, and we find that the ionospheric response to waves and precipitation can explain some, but not all, of the results contained within this paper. Specifically, the ionospheric response to substorm waves and auroral precipitation cannot explain the result backed up by previous studies that the onset of ULF wave activity and the onset of auroral particle precipitation occur at the same time and in the same location. This leaves the possibility that ULF waves and auroral particles are physically linked at their source. We therefore re-emphasize the importance of ULF wave observations in fully understanding the mechanism or mechanisms responsible for rapid auroral brightenings.
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Comprehensive ground-based and in situ observations of substorm Expansion Phase onset
Journal of Geophysical Research: Space Physics, 2010Co-Authors: Andrew Walsh, I. J. Rae, Kyle R. Murphy, Colin Forsyth, Andrew Fazakerley, Ian R. Mann, Clare E. J. Watt, Martin Volwerk, Howard J. Singer, Eric DonovanAbstract:[1] In this paper, we present comprehensive ground-based and space-based in situ geosynchronous observations of a substorm Expansion Phase onset on 1 October 2005. The Double Star TC-2 and GOES-12 spacecraft were both located within the substorm current wedge during the substorm Expansion Phase onset, which occurred over the Canadian sector. We find that an onset of ULF waves in space was observed after onset on the ground by extending the AWESOME timing algorithm into space. Furthermore, a population of low-energy field-aligned electrons was detected by the TC-2 PEACE instrument contemporaneous with the ULF waves in space. These electrons appear to be associated with an enhancement of field-aligned Poynting flux into the ionosphere which is large enough to power visible auroral displays. The observations are most consistent with a near-Earth initiation of substorm Expansion Phase onset, such as the Near-Geosynchronous Onset (NGO) substorm scenario. A lack of data from further downtail, however, means other mechanisms cannot be ruled out.
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Wavelet‐based ULF wave diagnosis of substorm Expansion Phase onset
Journal of Geophysical Research, 2009Co-Authors: Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Clare E. J. Watt, I. Jonathan Rae, David K. Milling, Vassilis Angelopoulos, Louis G. Ozeke, Christopher T. RussellAbstract:[1] Using a discrete wavelet transform with a Meyer wavelet basis, we present a new quantitative algorithm for determining the onset time of Pi1 and Pi2 ULF waves in the nightside ionosphere with � 20- to 40-s resolution at substorm Expansion Phase onset. We validate the algorithm by comparing both the ULF wave onset time and location to the optical onset determined by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE)–Far Ultraviolet Imager (FUV) instrument. In each of the six events analyzed, five substorm onsets and one pseudobreakup, the ULF onset is observed prior to the global optical onset observed by IMAGE at a station closely conjugate to the optical onset. The observed ULF onset times expand both latitudinally and longitudinally away from an epicenter of ULF wave power in the ionosphere. We further discuss the utility of the algorithm for diagnosing pseudobreakups and the relationship of the ULF onset epicenter to the meridians of elements of the substorm current wedge. The importance of the technique for establishing the causal sequence of events at substorm onset, especially in support of the multisatellite Time History of Events and Macroscale Interactions During Substorms (THEMIS) mission, is also described.
I. Jonathan Rae - One of the best experts on this subject based on the ideXlab platform.
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Automated determination of auroral breakup during the substorm Expansion Phase using all‐sky imager data
Journal of Geophysical Research: Space Physics, 2014Co-Authors: Kyle R. Murphy, Ian R. Mann, Clare E. J. Watt, I. Jonathan Rae, David M. Miles, Harald U. FreyAbstract:This paper describes a novel method for quantitatively and routinely identifying auroral breakup following substorm onset using the Time History of Events and Macroscale Interactions during Substorms all-sky imagers. Substorm onset is characterized by a brightening of the aurora that is followed by auroral poleward Expansion and auroral breakup. This breakup can be identified by a sharp increase in the auroral intensity i(t) and the time derivative of auroral intensity i(t). Utilizing both i(t) and i'(t), we have developed an algorithm for identifying the time interval and spatial location of auroral breakup during the substorm Expansion Phase based solely on quantifiable characteristics of the optical auroral emissions. We compare the time interval determined by the algorithm to independently identified auroral onset times from three previously published studies. In each case the time interval determined by the algorithm is within error of the onset independently identified by the prior studies. We further show the utility of the algorithm by comparing the breakup intervals determined using the automated algorithm to an independent list of substorm onset times. We demonstrate that 50% of the breakup intervals characterized by the algorithm are within the uncertainty of the times identified in the list. The quantitative description and routine identification of an interval of auroral brightening during the substorm Expansion Phase provides a foundation for unbiased statistical analysis of the aurora and to probe the physics of the auroral substorm and identify the processes leading to auroral substorm onset.
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The detailed spatial structure of field‐aligned currents comprising the substorm current wedge
Journal of Geophysical Research: Space Physics, 2013Co-Authors: Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Howard J. Singer, I. Jonathan Rae, A. Kale, C L Waters, B J Anderson, Haje KorthAbstract:[1] We present a comprehensive two-dimensional view of the field-aligned currents (FACs) during the late growth and Expansion Phases for three isolated substorms utilizing in situ observations from the Active Magnetosphere and Planetary Electrodynamics Response Experiment and from ground-based magnetometer and optical instrumentation from the Canadian Array for Realtime Investigations of Magnetic Activity and Time History of Events and Macroscale Interactions during Substorms ground-based arrays. We demonstrate that the structure of FACs formed during the Expansion Phase and associated with the substorm current wedge is significantly more complex than a simple equivalent line current model comprising a downward FAC in the east and upward FAC in the west. This two-dimensional view demonstrates that azimuthal bands of upward and downward FACs with periodic structuring in latitude form across midnight and can span up to 8 h of magnetic local time. However, when averaged over latitude, the overall longitudinal structure of the net FACs resembles the simpler equivalent line current description of the substorm current wedge (SCW). In addition, we demonstrate that the upward FAC elements of the structured SCW are spatially very well correlated with discrete aurora during the substorm Expansion Phase and that discrete changes in the FAC topology are observed in the late growth Phase prior to auroral substorm Expansion Phase onset. These observations have important implications for determining how the magnetosphere and ionosphere couple during the late growth Phase and Expansion Phase, as well as providing important constraints on the magnetospheric generator of the FACs comprising the SCW.
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The correlation of ULF waves and auroral intensity before, during and after substorm Expansion Phase onset
Journal of Geophysical Research: Space Physics, 2012Co-Authors: I. Jonathan Rae, Kyle R. Murphy, Harald U. Frey, Clare E. J. Watt, David K. Milling, Louis G. Ozeke, Ian R. MannAbstract:[1] We present case studies of the evolution of Ultra-Low Frequency (ULF) magnetic wave amplitudes and auroral intensity through the late growth Phase and the Expansion Phase of the substorm cycle. We present strong evidence that substorm-related auroral enhancements are clearly and demonstrably linked to ULF wave amplitudes observed at the same location. In all three case studies presented, the correlation analysis shows that the ULF wave activity and auroral intensities are highly correlated at close to zero lag. We discuss four possible explanations that may be able to explain both the timing and the high correlations between these two phenomena, including a simple coincidence, an artifact of instrumental effects, the response of the ionosphere to magnetic waves and auroral particle precipitation, and finally, that ULF waves and auroral particle precipitation are physically linked at their source. We discount coincidence and instrumental effects since we present multiple events where instrumental effects have a negligible contribution, and we find that the ionospheric response to waves and precipitation can explain some, but not all, of the results contained within this paper. Specifically, the ionospheric response to substorm waves and auroral precipitation cannot explain the result backed up by previous studies that the onset of ULF wave activity and the onset of auroral particle precipitation occur at the same time and in the same location. This leaves the possibility that ULF waves and auroral particles are physically linked at their source. We therefore re-emphasize the importance of ULF wave observations in fully understanding the mechanism or mechanisms responsible for rapid auroral brightenings.
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Wavelet‐based ULF wave diagnosis of substorm Expansion Phase onset
Journal of Geophysical Research, 2009Co-Authors: Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Clare E. J. Watt, I. Jonathan Rae, David K. Milling, Vassilis Angelopoulos, Louis G. Ozeke, Christopher T. RussellAbstract:[1] Using a discrete wavelet transform with a Meyer wavelet basis, we present a new quantitative algorithm for determining the onset time of Pi1 and Pi2 ULF waves in the nightside ionosphere with � 20- to 40-s resolution at substorm Expansion Phase onset. We validate the algorithm by comparing both the ULF wave onset time and location to the optical onset determined by the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE)–Far Ultraviolet Imager (FUV) instrument. In each of the six events analyzed, five substorm onsets and one pseudobreakup, the ULF onset is observed prior to the global optical onset observed by IMAGE at a station closely conjugate to the optical onset. The observed ULF onset times expand both latitudinally and longitudinally away from an epicenter of ULF wave power in the ionosphere. We further discuss the utility of the algorithm for diagnosing pseudobreakups and the relationship of the ULF onset epicenter to the meridians of elements of the substorm current wedge. The importance of the technique for establishing the causal sequence of events at substorm onset, especially in support of the multisatellite Time History of Events and Macroscale Interactions During Substorms (THEMIS) mission, is also described.
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Timing and localization of ionospheric signatures associated with substorm Expansion Phase onset
Journal of Geophysical Research, 2009Co-Authors: I. Jonathan Rae, Kyle R. Murphy, Harald U. Frey, Ian R. Mann, Clare E. J. Watt, David K. Milling, Adrienne Parent, Vassilis Angelopoulos, A. Kale, Stephen B. MendeAbstract:[1] In this paper, we present case studies of the optical and magnetic signatures of the characteristics of the first minute of substorm Expansion Phase onset observed in the ionosphere. We find that for two isolated substorms, the onset of magnetic pulsations in the 24–96 s period wavelet band are colocated in time and space with the formation and development of small-scale optical undulations along the most equatorward preexisting auroral arc prior to auroral breakup. These undulations undergo an inverse spatial cascade into vortices prior to the release of the westward traveling surge. We also present a case study of a multiple activation substorm, whereby discrete onsets of ULF wave power above a predetermined quiet time threshold are shown to be associated with specific optical intensifications and brightenings. Moreover, in the multiple activation substorm event, we show that neither the formation of the small-scale undulations nor the formation of similar structures along a north–south aligned arc is sufficient to produce auroral breakup associated with Expansion Phase onset. It is only ∼10 min after these two disparate activation regions initiate that auroral breakup and the subsequent formation of a westward traveling surge occur. We discuss the implications of these results in terms of the triggering mechanisms likely to be occurring during these specific events.
Junji Tsurutani - One of the best experts on this subject based on the ideXlab platform.
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trastuzumab deruxtecan ds 8201a in patients with advanced her2 positive breast cancer previously treated with trastuzumab emtansine a dose Expansion Phase 1 study
Lancet Oncology, 2019Co-Authors: Kenji Tamura, Hiroji Iwata, Shunji Takahashi, Haeseong Park, Junji Tsurutani, Ian E Krop, Charles H Redfern, Yasuaki Sagara, Rashmi Krishna MurthyAbstract:Summary Background Trastuzumab deruxtecan (DS-8201a) is a novel HER2-targeted antibody–drug conjugate with a humanised anti-HER2 antibody, cleavable peptide-based linker, and potent topoisomerase I inhibitor payload. A Phase 1, non-randomised, open-label, multiple-dose study was done to assess the safety, tolerability, and activity of trastuzumab deruxtecan in HER2-expressing, advanced solid tumours. The dose escalation (part 1) has previously been reported and the recommended doses for Expansion of 5·4 mg/kg or 6·4 mg/kg were established. In this Article, we report the safety and preliminary activity results from this Phase 1 trial in all patients with HER2-positive advanced-stage breast cancer with previous trastuzumab emtansine treatment who received trastuzumab deruxtecan at the recommended doses for Expansion. Methods We did an open-label, dose-escalation and dose-Expansion Phase 1 trial at eight hospitals and clinics in the USA and six in Japan. Eligible patients were at least 18 years old in the USA and at least 20 years of age in Japan and had advanced solid tumours (regardless of HER2 expression in dose escalation or HER2 expression or mutation in dose Expansion). The recommended doses for Expansion of 5·4 mg/kg or 6·4 mg/kg trastuzumab deruxtecan were administered intravenously to patients once every 3 weeks until withdrawal of consent, unacceptable toxicity, or progressive disease. In this Article, all patients with HER2-positive advanced-stage breast cancer with previous trastuzumab emtansine treatment who received trastuzumab deruxtecan at the recommended doses for Expansion were analysed together. The primary endpoints of the study were safety and preliminary activity (proportion of patients who achieved an objective response as assessed by the investigators). The activity evaluable set included all patients who received at least one dose of trastuzumab deruxtecan at the recommended doses for Expansion, and for whom both baseline and post-treatment activity data were available. The safety analysis set included all patients who received at least one dose of trastuzumab deruxtecan at the recommended doses for Expansion. Enrolment for patients with HER2-positive breast cancer has been completed. This trial is registered at ClinicalTrials.gov, number NCT02564900, and ClinicalTrials.jp, number JapicCTI-152978. Findings Between Aug 28, 2015, and Aug 10, 2018, 115 of 118 patients with HER2-positive breast cancer were treated with at least one dose of trastuzumab deruxtecan at the recommended doses for Expansion. All patients had at least one treatment-emergent adverse event. Frequent grade 3 or worse treatment-emergent adverse events included anaemia (19 [17%] of 115) and decreased neutrophil (16 [14%]), white blood cell (ten [9%]), and platelet (nine [8%]) counts. At least one serious treatment-emergent adverse event occurred for 22 (19%) patients. Investigators reported 20 cases of interstitial lung disease, pneumonitis, or organising pneumonia, including one grade 3 event and two treatment-related deaths due to pneumonitis. One death unrelated to study treatment was due to progressive disease. 66 (59·5%; 95% CI 49·7–68·7) of 111 patients had a confirmed objective response. Interpretation Trastuzumab deruxtecan had a manageable safety profile and showed preliminary activity in trastuzumab emtansine-pretreated patients with HER2-positive breast cancer. These results suggest that further development in Phase 2 and 3 clinical trials for HER2-positive breast cancer is warranted. Funding Daiichi Sankyo Co, Ltd.
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Trastuzumab deruxtecan (DS-8201a) in patients with advanced HER2-positive gastric cancer: a dose-Expansion, Phase 1 study
The Lancet. Oncology, 2019Co-Authors: Kohei Shitara, Hiroji Iwata, Shunji Takahashi, Kenji Tamura, Haeseong Park, Shanu Modi, Junji Tsurutani, Shigenori Kadowaki, Kensei Yamaguchi, Satoru IwasaAbstract:Summary Background Trastuzumab deruxtecan (DS-8201a) is a novel HER2-targeted antibody–drug conjugate with a humanised anti-HER2 antibody, cleavable peptide-based linker, and topoisomerase I inhibitor payload. A Phase 1, non-randomised, open-label, multiple-dose study was done to assess the safety, tolerability, and activity of trastuzumab deruxtecan in HER2-expressing advanced solid tumours. The dose escalation (part 1) has previously been reported and the recommended doses for Expansion of 5·4 mg/kg or 6·4 mg/kg were established. In this Article, we report the safety and preliminary activity results from this Phase 1 trial in all patients with HER2-positive gastric or gastro-oesophageal junction cancer who received trastuzumab deruxtecan at the recommended doses for Expansion. Methods This was an open-label, dose-escalation and dose-Expansion Phase 1 trial done at eight hospitals and clinics in the USA and six in Japan. Eligible patients were at least 18 years old in the USA and at least 20 years old in Japan and had advanced solid tumours (regardless of HER2 expression in dose escalation or HER2 expression or mutation in dose Expansion). The recommended doses for Expansion of 5·4 mg/kg or 6·4 mg/kg trastuzumab deruxtecan were administered intravenously to patients once every 3 weeks until withdrawal of consent, unacceptable toxicity, or progressive disease. In this Article, all patients with HER2-positive gastric or gastro-oesophageal junction cancer with previous trastuzumab treatment who received trastuzumab deruxtecan were analysed together. The primary endpoints of the study were safety and preliminary activity (proportion of patients who achieved an objective response as assessed by the investigators). The activity evaluable set included all patients who received at least one dose of trastuzumab deruxtecan at the recommended doses for Expansion, and for whom both baseline and post-treatment activity data were available. The safety analysis set included all patients who received at least one dose of trastuzumab deruxtecan at the recommended doses for Expansion. Enrolment for patients with gastric or gastro-oesophageal junction cancer has completed. This trial is registered at ClinicalTrials.gov , number NCT02564900 , and ClinicalTrials.jp, number JapicCTI-152978. Findings Between Aug 28, 2015, and Aug 10, 2018, 44 patients with HER2-positive gastric or gastro-oesophageal junction cancer received at least one dose of trastuzumab deruxtecan at the recommended doses for Expansion. All patients had at least one treatment-emergent adverse event. The most frequent grade 3 or worse treatment-emergent adverse events included anaemia (13 [30%]) and decreases in neutrophil (nine [20%]), platelet (eight [18%]), and white blood cell (seven [16%]) counts. Serious treatment-emergent adverse events occurred in 11 (25%) patients. There were four pneumonitis cases (three grade 2 and one grade 3). There were no drug-related deaths due to treatment-emergent adverse events. 19 (43·2%; 95% CI 28·3–59·0) of 44 patients had a confirmed objective response. Interpretation Trastuzumab deruxtecan had a manageable safety profile and showed preliminary activity in heavily pretreated patients with HER2-positive gastric or gastro-oesophageal junction cancer. These results support further investigation of trastuzumab deruxtecan for HER2-positive gastric or gastro-oesophageal junction cancer post-trastuzumab. Funding Daiichi Sankyo Co, Ltd.
