Magnetic Local Time‐Resolved Examination of Radiation Belt Dynamics during High‐Speed Solar Wind Speed‐Triggered Substorm Clusters

Rodger, Craig J.; Turner, D. L.; Clilverd, Mark A.; Hendry, Aaron T.

doi:10.1029/2019gl083712

Cited by 11 publications

(31 citation statements)

References 42 publications

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“…This work initially identified HILDCAA activity present in the magnetosphere linked to large amplitude Alfvén waves in the solar wind and leading to intense auroral activity (Tsurutani & Gonzalez, 1987), with intense substorm activity (Tsurutani et al, 1995, https://doi.org/10.1029/95ja01476). Subsequent work demonstrated that 94% of the HILDCAA periods were associated with high-speed solar wind streams (Hajra et al, 2013), much like the recurrent substorm clusters reported by Rodger et al (2016Rodger et al ( , 2019, and that HILDCAA periods consistently produced enhancements in whistler mode chorus and relativistic electrons measured in geostationary orbit (Hajra et al, 2015).…”

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confidence: 81%

Examination of Radiation Belt Dynamics During Substorm Clusters: Activity Drivers and Dependencies of Trapped Flux Enhancements

et al. 2022

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It has long been recognized that electron fluxes in the outer radiation belt are highly dynamic. This high dynamism is thought to be due to competing drivers causing acceleration, loss, and transport, with growing evidence regarding the importance of nonlinear processes (see, e.g., the review, Ripoll et al., 2020). Typically, the occurrence and magnitude of the differing drivers are dependent upon distance from the Earth (expressed, e.g., through the L-shell), particularly due to the changing cold plasma density and the strong gradients around the plasmapause. At the same time, these driving processes also depend very strongly on magnetic local time (MLT). The drive to understand the spatial and temporal dynamism of the outer radiation belts encapsulates the primary science questions around that physical system.A long-term focus for the radiation belt physics has been predicting the variation of trapped energetic and relativistic electron fluxes by understanding the physical processes driving the rapid, large magnitude changes seen in experimental data. About 15 years ago it was common for the community to try and understand changes occurring during very large geomagnetic disturbances, often looking at times around very large Dst changes. Unfortunately, this hampered deeper physical understanding of the processes occurring in the radiation belts, due to the combination of multiple large amplitude drivers competing during such large storms (Reeves et al., 2003). This focus on case studies during the largest disturbances has been described as the "Dst mistake" (Denton et al., 2009;, summarized by Geoff Reeves with the expression "If you have seen one storm, you have seen one storm" (Koskinen, 2011, p. 323). Following the "Dst mistake," there has been a stronger focus on trying to understand the "typical" or "consistent" variations in trapped fluxes when processes occur. One example of this approach is the use of superposed epoch analysis to focus electron flux decreases termed "dropouts," seen in GPS data, following high speed streams , and subsequently examined using low-Earth POES observations (Meredith et al., 2011, Hendry et al., 2012. The value of similar approaches has been

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confidence: 81%

Examination of Radiation Belt Dynamics During Substorm Clusters: Activity Drivers and Dependencies of Trapped Flux Enhancements

et al. 2022

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“…Hence, during indirect magnetopause shadowing the initial particle drift path does not have to directly intersect the magnetopause boundary. Indirect magnetopause shadowing explains electron loss at comparatively low L shells where the magnetopause would never directly impact (e.g., Brautigam & Albert, 2000;Loto'Aniu et al, 2010;Miyoshi et al, 2003;Morley et al, 2010;Rodger et al, 2019;Shprits et al, 2006;Turner et al, 2012).…”

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confidence: 99%

Do Statistical Models Capture the Dynamics of the Magnetopause During Sudden Magnetospheric Compressions?

et al. 2020

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Under periods of strong solar wind driving, the magnetopause can become compressed, playing a significant role in draining electrons from the outer radiation belt. Also termed "magnetopause shadowing," this loss process has traditionally been attributed to a combination of magnetospheric compression and outward radial diffusion of electrons. However, the drift paths of relativistic electrons and the location of the magnetopause are usually calculated from statistical models and, as such, may not represent the time-varying nature of this highly dynamic process. In this study, we construct a database ∼20,000 spacecraft crossings of the dayside magnetopause to quantify the accuracy of the commonly used Shue et al. (1998, https://doi.org/10.1029/98JA01103) model. We find that, for the majority of events (74%), the magnetopause model can be used to estimate magnetopause location to within ±1 R E . However, if the magnetopause is compressed below 8 R E , the observed magnetopause is greater than 1 R E inside of the model location on average. The observed magnetopause is also significantly displaced from the model location during storm sudden commencements, when measurements are on average 6% closer to the radiation belts, with a maximum of 42%. We find that the magnetopause is rarely close enough to the outer radiation belt to cause direct magnetopause shadowing, and hence rapid outward radial transport of electrons is also required. We conclude that statistical magnetopause parameterizations may not be appropriate during dynamic compressions. We suggest that statistical models should only be used during quiescent solar wind conditions and supplemented by magnetopause observations wherever possible.

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“…To reduce overlap between events, we filtered this list down to a list of 6,276 "clustered" (or "recurrent") substorms (cf. Cresswell-Moorcock et al, 2013 andRodger et al, 2019). The results of this analysis are plotted in Figure S1 in the Supporting Information.…”

Section: Sea Resultsmentioning

confidence: 99%

Evidence of Sub‐MeV EMIC‐Driven Trapped Electron Flux Dropouts From GPS Observations

Hendry

Rodger

Clilverd

et al. 2021

Geophysical Research Letters

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Magnetic Local Time‐Resolved Examination of Radiation Belt Dynamics during High‐Speed Solar Wind Speed‐Triggered Substorm Clusters

Cited by 11 publications

References 42 publications

Examination of Radiation Belt Dynamics During Substorm Clusters: Activity Drivers and Dependencies of Trapped Flux Enhancements

Examination of Radiation Belt Dynamics During Substorm Clusters: Activity Drivers and Dependencies of Trapped Flux Enhancements

Do Statistical Models Capture the Dynamics of the Magnetopause During Sudden Magnetospheric Compressions?

Evidence of Sub‐MeV EMIC‐Driven Trapped Electron Flux Dropouts From GPS Observations

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