The permeability of the magnetopause to a multispecies substorm injection of energetic particles

Westlake, J. H.; Cohen, I. J.; Mauk, B. H.; Anderson, B. J.; Mitchell, D. G.; Gkioulidou, M.; Walsh, Brian M.; Lanzerotti, L. J.; Strangeway, R. J.; Russell, C. T.

doi:10.1002/2016gl070189

Cited by 7 publications

(28 citation statements)

References 26 publications

(48 reference statements)

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“…Kelvin-Helmholz wave generation is one mechanism highlighted by Sorathia et al (2017). Here we would only proclaim that the observations of Westlake et al (2016) and Cohen et al (2016) of oxygen ions in the magnetosheath provide no support for escaping configurations. We have shown that those oxygen ions did not in fact escape but were entrained at the boundary executing Speiser-like orbits (see Event 1 discussed in section 2.1.1).…”

Section: 1029/2019ja026626mentioning

confidence: 67%

Investigation of Mass‐/Charge‐Dependent Escape of Energetic Ions Across the Magnetopauses of Earth and Jupiter

et al. 2019

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We present a continuing investigation of mass‐/charge‐dependent interactions between energetic ions (greater than tens of kiloelectron volts) and planetary magnetopauses and of the escape of the ions across the boundary. Previous studies at Earth using Magnetospheric Multiscale mission data are refined and advanced showing profound behavior differences between light (H, He) and singly charged heavy ions (O+). We highlight a distinctive feature of oxygen ions: an angular distribution bifurcation providing clear indication of entrainment along the magnetopause in Speiser‐like orbits during relatively stable magnetic conditions. This signature, interpreted using a simple kinetic model, suggests that these ions tend to be carried substantial distances along the boundary (even with boundary‐normal magnetic fields) in a fashion that impedes their full dayside escape. While large fluctuations and waves can likely sometimes disrupt the observed ordering, the following picture emerges. Energetic particles with gyroradii much smaller than the magnetopause thickness (e.g., electrons and absent boundary‐normal magnetic fields) and ions with gyroradii much larger than the thickness (e.g., O+) are impeded from fully escaping across the boundary. However, energetic ions with intermediate‐sized gyroradii commensurate with the thickness (e.g., H+, He++, and O6+) can be effectively scattered within the boundary causing them to escape much more readily, with and without boundary‐normal fields. This picture is supported by observations from the Juno spacecraft at the near‐dawn meridian side of Jupiter's magnetopause. There it is observed that energetic electrons and heavy ions are more strongly contained by the magnetopause than are the energetic protons and helium ions.

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Section: 1029/2019ja026626mentioning

confidence: 67%

Investigation of Mass‐/Charge‐Dependent Escape of Energetic Ions Across the Magnetopauses of Earth and Jupiter

et al. 2019

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“…Energetic particle (greater than or equivalent to tens of keV) escape from the magnetosphere has received renewed interested recently due to in situ observations made by the Magnetospheric Multiscale (MMS) mission at the dayside magnetopause [ Cohen et al , ; Westlake et al , ]. Historically, observations of magnetospheric ions and electrons in the magnetosheath have been associated with either finite Larmor radius effects [e.g., Sibeck et al , ; Kudela et al , ] or magnetic reconnection [e.g., Korth et al , ; Mitchell et al , ], the former mechanism favored due to poor correlation of particle escape with conditions required for reconnection [ Sibeck et al , ].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, Westlake et al [] used observations during the same MMS magnetopause crossing to highlight marked differences in the particle signatures of escape of the light (H and He) and heavy (O) ions. The observations showed specific agyrotropic signatures in the O distributions suggesting that the heavy ions were entrained within the boundary and drifted duskward, while the lighter ions escaped along the reconnected field lines.…”

Section: Introductionmentioning

confidence: 99%

Energetic particle loss through the magnetopause: A combined global MHD and test‐particle study

et al. 2017

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We study the spatiotemporal characteristics of energetic particle losses from the magnetosphere using test‐particle trajectories in electromagnetic fields from a global magnetosphere magnetohydrodynamic (MHD) simulation. We use a dynamically evolving distribution of high‐resolution electromagnetic fields from the Lyon‐Fedder‐Mobarry global MHD model and trace large ensembles of 100 keV hydrogen and oxygen ions as well as electrons from a near‐Earth plasma sheet location through their escape from the magnetosphere. In agreement with recent MMS observations, we demonstrate that both ions and electrons have access to and escape throughout the dayside magnetopause, including magnetically drift‐shadowed regions. Also, in agreement with MMS observations, the depth of penetration and persistence of particles in the magnetosheath has a clear mass dependence, heavier particles penetrating further and lingering longer. We demonstrate both magnetic local time and latitude dependence of particles losses as manifested by their crossings of the open‐closed boundary and relate them to the complex field topology. Finally, we establish a significant role of Kelvin‐Helmholtz instability in facilitating particle losses at the magnetopause flanks.

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“…In an attempt to highlight the novelty of the statistical study presented here amidst the extremely rich history of the study of energetic electrons beyond the magnetopause, a substantial (but admittedly nonexhaustive) literature review is provided in section 1.1. It must be emphasized that this paper (and the review included) will focus specifically on observations of energetic (greater than tens of keV) electrons observed in the magnetosheath and upstream of the bow shock and is independent of the extremely rich literature regarding the well‐documented history of lower energy (eV to several keV) particles at/beyond the magnetopause [e.g., Freeman et al , ; Montgomery et al , ; Scarf et al , ; Hones et al , ; Scudder et al , ; Reasoner , ; Eastman et al , ; Cowley , ; Fuselier et al , , ; Lefebvre et al , ; Lee et al , , and references therein] and observations of escaping magnetospheric ions [e.g., West and Buck , ; Anagnostopoulos et al , ; Sibeck et al , , ; Zong et al , ; Eccles and Fritz , ; Kronberg et al , ; Westlake et al , , and references therein], upstream ion events [e.g., Asbridge et al , ; Lin et al , ; Scholer et al , , ; Desai et al , , and references therein], and shock‐related ion acceleration [e.g., Ipavich et al , ; Gosling , ; Armstrong et al , ; Forman and Webb , ; Scholer , ; Thomsen , ; Sibeck et al , ; Burgess et al , ; Lee et al , , and references therein]. We focus here on electrons because ions have a broader array of escape mechanisms [ Mauk et al , ] that make their study substantially more complex.…”

Section: Introductionmentioning

confidence: 99%

Statistical analysis of MMS observations of energetic electron escape observed at/beyond the dayside magnetopause

et al. 2017

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Observations from the Energetic Particle Detector (EPD) instrument suite aboard the Magnetospheric Multiscale (MMS) spacecraft show that energetic (greater than tens of keV) magnetospheric particle escape into the magnetosheath occurs commonly across the dayside. This includes the surprisingly frequent observation of magnetospheric electrons in the duskside magnetosheath, an unexpected result given assumptions regarding magnetic drift shadowing. The 238 events identified in the 40 keV electron energy channel during the first MMS dayside season that exhibit strongly anisotropic pitch angle distributions indicating monohemispheric field‐aligned streaming away from the magnetopause. A review of the extremely rich literature of energetic electron observations beyond the magnetopause is provided to place these new observations into historical context. Despite the extensive history of such research, these new observations provide a more comprehensive data set that includes unprecedented magnetic local time (MLT) coverage of the dayside equatorial magnetopause/magnetosheath. These data clearly highlight the common escape of energetic electrons along magnetic field lines concluded to have been reconnected across the magnetopause. While these streaming escape events agree with prior studies which show strong correlation with geomagnetic activity (suggesting a magnetotail source) and occur most frequently during periods of southward IMF, the high number of duskside events is unexpected and previously unobserved. Although the lowest electron energy channel was the focus of this study, the events reported here exhibit pitch angle anisotropies indicative of streaming up to 200 keV, which could represent the magnetopause loss of >1 MeV electrons from the outer radiation belt.

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The permeability of the magnetopause to a multispecies substorm injection of energetic particles

Cited by 7 publications

References 26 publications

Investigation of Mass‐/Charge‐Dependent Escape of Energetic Ions Across the Magnetopauses of Earth and Jupiter

Investigation of Mass‐/Charge‐Dependent Escape of Energetic Ions Across the Magnetopauses of Earth and Jupiter

Energetic particle loss through the magnetopause: A combined global MHD and test‐particle study

Statistical analysis of MMS observations of energetic electron escape observed at/beyond the dayside magnetopause

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