Heavy‐ion dominance near Cluster perigees

Ferradas, C.; Zhang, J.-C.; Kistler, L. M.; Spence, H. E.

doi:10.1002/2015ja021063

Cited by 22 publications

(43 citation statements)

References 93 publications

(158 reference statements)

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“…Drifting plasma sheet ions are energized by the increased magnetic field strength (as well as temporarily energized by field fluctuations). Aging of the drifting plasma over a~24 h period led to an enhanced heavy ion content [Smith and Bewtra, 1978;Fok et al, 1991;Ebihara et al, 1998;Ferradas et al, 2015;Kistler and Mouikis, 2016]. This plasma mimics the presence of local in situ acceleration of the low-energy population.…”

Section: Discussionmentioning

confidence: 90%

“…Since O + is a major constituent of the ionosphere, and not of the solar wind, the presence of high-density O + (along with He + ) is strongly indicative of an ionospheric source. These losses result in changes in the composition that are energy (i.e., drift) dependent [Ferradas et al, 2015;Kistler and Mouikis, 2016]. (a) Direct and local acceleration of ionosphere and/or plasmasphere ions.…”

Section: Introductionmentioning

confidence: 99%

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The complex nature of storm‐time ion dynamics: Transport and local acceleration

Denton

Reeves

Thomsen

et al. 2016

Geophysical Research Letters

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Data from the Van Allen Probes Helium, Oxygen, Proton, and Electron (HOPE) spectrometers reveal hitherto unresolved spatial structure and dynamics in ion populations. Complex regions of O+ dominance, at energies from a few eV to >10 keV, are observed throughout the magnetosphere. Isolated regions on the dayside that are rich in energetic O+ might easily be interpreted as strong energization of ionospheric plasma. We demonstrate, however, that both the energy spectrum and the limited magnetic local time extent of these features can be explained by energy‐dependent drift of particles injected on the nightside 24 h earlier. Particle tracing simulations show that the energetic O+ can originate in the magnetotail, not in the ionosphere. Enhanced wave activity is colocated with the heavy ion‐rich plasma, and we further conclude that the waves were not a source of free energy for accelerating ionospheric plasma but rather the consequence of the arrival of substorm‐injected plasma.

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Section: Discussionmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

The complex nature of storm‐time ion dynamics: Transport and local acceleration

Denton

Reeves

Thomsen

et al. 2016

Geophysical Research Letters

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“…While H + and O + pressures are similar further out, at lower L values the O + pressure is about double the H + pressure at its peak. Previous work [ Lundin et al ., ; Ferradas et al ., ] has shown that charge exchange can lead to O + dominance inside L = 4 during quiet times because the charge exchange rate for H + is higher than O + for energies less than 45 keV. However, during storm times, the convection is faster, so charge exchange only significantly impacts the lowest L values.…”

Section: Discussionmentioning

confidence: 99%

The role of convection in the buildup of the ring current pressure during the 17 March 2013 storm

et al. 2017

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On 17 March 2013, the Van Allen Probes measured the H+ and O+ fluxes of the ring current during a large geomagnetic storm. Detailed examination of the pressure buildup during the storm shows large differences in the pressure measured by the two spacecraft, with measurements separated by only an hour, and large differences in the pressure measured at different local times. In addition, while the H+ and O+ pressure contributions are about equal during the main phase in the near‐Earth plasma sheet outside L = 5.5, the O+ pressure dominates at lower L values. We test whether adiabatic convective transport from the near‐Earth plasma sheet (L > 5.5) to the inner magnetosphere can explain these observations by comparing the observed inner magnetospheric distributions with the source distribution at constant magnetic moment, mu. We find that adiabatic convection can account for the enhanced pressure observed during the storm. Using a Weimer 1996 electric field we model the drift trajectories to show that the key features can be explained by variation in the near‐Earth plasma sheet population and particle access that changes with energy and L shell. Finally, we show that the dominance of O+ at low L shells is due partly to a near‐Earth plasma sheet that is preferentially enhanced in O+ at lower energies (5–10 keV) and partly due to the time dependence in the source combined with longer drift times to low L shells. No source of O+ inside L = 5.5 is required to explain the observations at low L shells.

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“…They decreased down to <1 at the inner edge (Lm~2). The high ratios seemingly spatially localized in the radial direction are beyond the scope of this paper; it is probably related to the events observed by Cluster at its perigees (Ferradas et al, 2015) and by Van Allen Probes (Zhao et al, 2015) and will be investigated in near future with a larger database of MEP-i observations. The He+ energy density was more than 1 order of magnitude lower through all L shell ranges.…”

Section: 1029/2018gl080047mentioning

confidence: 95%

Ion Energies Dominating Energy Density in the Inner Magnetosphere: Spatial Distributions and Composition, Observed by Arase/MEP‐i

Keika

Kasahara

Yokota

et al. 2018

Geophysical Research Letters

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We investigate the spatial distributions and composition of contributing energies, which we term an energy range that makes the dominant contribution to energy density, in the inner magnetosphere during the main phase of magnetic storms. We analyze data from the medium‐energy particle experiments‐ion mass analyzer (MEP‐i) on board the Arase satellite during six magnetic storms in year 2017 with the SYM‐H minimum smaller than −50 nT. The results show that the inner part (L ≤ 5) is dominated by relatively low‐energy ions adiabatically transported from the plasma sheet by enhanced convection. The contributing energies are higher for O+ than for H+ at higher L shells (L > 5), particularly during the storms driven by coronal mass ejections. The results provide in situ evidence of the contribution from mass‐dependent/selective acceleration processes associated with substorm activity to the buildup of the outer part the ring current.

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Heavy‐ion dominance near Cluster perigees

Cited by 22 publications

References 93 publications

The complex nature of storm‐time ion dynamics: Transport and local acceleration

The complex nature of storm‐time ion dynamics: Transport and local acceleration

The role of convection in the buildup of the ring current pressure during the 17 March 2013 storm

Ion Energies Dominating Energy Density in the Inner Magnetosphere: Spatial Distributions and Composition, Observed by Arase/MEP‐i

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