Dawn–dusk asymmetries in the coupled solar wind–magnetosphere–ionosphere system: a review

Walsh, A. P.; Haaland, Stein; Forsyth, C.; Keesee, A. M.; Kissinger, J.; Li, Kun; Runov, A.; Souček, J; Walsh, Brian M.; Wing, Simon; Taylor, M. G. G. T.

doi:10.5194/angeo-32-705-2014

Cited by 77 publications

(88 citation statements)

References 246 publications

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“…Likewise, the observations at lower MLTs showing an overlap of low and high energies relate to the simulation results, particularly to the Kp=2.3 and Kp=2.7 cases. It is known that there are persistent dawndusk asymmetries in particle populations and plasma convection in the magnetosphere, some of which are imposed by a nonzero y component of the interplanetary magnetic field [e.g., Cowley, 1981;Haaland et al, 2007;Walsh et al, 2014]. However, note also that the single-nose observations in Figure 5 and the calculated drift time in Figure 7 differ in some ways.…”

Section: 1002/2016ja022942mentioning

confidence: 94%

Ion nose spectral structures observed by the Van Allen Probes

et al. 2016

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We present a statistical study of nose‐like structures observed in energetic hydrogen, helium, and oxygen ions near the inner edge of the plasma sheet. Nose structures are spectral features named after the characteristic shapes of energy bands or gaps in the energy‐time spectrograms of in situ measured ion fluxes. Using 22 months of observations from the Helium Oxygen Proton Electron instrument onboard Van Allen Probe A, we determine the number of noses observed, and the minimum L shell reached and energy of each nose on each pass through the inner magnetosphere. We find that multiple noses occur more frequently in heavy ions than in H+ and are most often observed during quiet times. The heavy‐ion noses penetrate to lower L shells than H+ noses, and there is an energy‐magnetic local time (MLT) dependence in the nose locations and energies that is similar for all species. The observations are interpreted by using a steady state model of ion drift in the inner magnetosphere. The model is able to explain the energy and MLT dependence of the different types of nose structures. Different ion charge‐exchange lifetimes are the main cause for the deeper penetration of heavy‐ion noses. The species dependence and preferred geomagnetic conditions of multiple‐nose events indicate that they must be on long drift paths, leading to strong charge‐exchange effects. The results provide important insight into the spatial distribution, species dependence, and geomagnetic conditions under which nose structures occur.

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Section: 1002/2016ja022942mentioning

confidence: 94%

Ion nose spectral structures observed by the Van Allen Probes

et al. 2016

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“…Also, the occurrence is lower at the geomagnetic tail flanks (Figure , middle). The dawn‐dusk asymmetry with higher occurrence at positive Y GSM (dusk) is consistent with earlier studies of low‐energy ions [ Li et al ., ] and also with studies of ions at higher energies [ Walsh et al ., ].…”

Section: Observationsmentioning

confidence: 99%

Outflow of low‐energy ions and the solar cycle

2015

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Magnetospheric ions with energies less than tens of eV originate from the ionosphere. Positive low-energy ions are complicated to detect onboard sunlit spacecraft at higher altitudes, which often become positively charged to several tens of volts. We use two Cluster spacecraft and study low-energy ions with a technique based on the detection of the wake behind a charged spacecraft in a supersonic ion flow. We find that low-energy ions usually dominate the density and the outward flux in the geomagnetic tail lobes during all parts of the solar cycle. The global outflow is of the order of 10 26 ions/s and often dominates over the outflow at higher energies. The outflow increases by a factor of 2 with increasing solar EUV flux during a solar cycle. This increase is mainly due to the increased density of the outflowing population, while the outflow velocity does not vary much. Thus, the outflow is limited by the available density in the ionospheric source rather than by the energy available in the magnetosphere to increase the velocity.

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“…While there exists dawn‐dusk asymmetries in most of the magnetosheath plasma properties (Dimmock & Nykyri, ; Dimmock et al, , , ; Nykyri & Dimmock, ; Walsh et al, , ), probably, the asymmetry of the IMF orientation has the strongest influence on the KHI development in each flank. Because IMF is statistically in PS orientation (see, for example, solar wind and IMF distributions in Dimmock and Nykyri, ), dawnside magnetospheric flank statistically has smaller tangential magnetic field.…”

Section: Introductionmentioning

confidence: 99%

On the Dawn‐Dusk Asymmetry of the Kelvin‐Helmholtz Instability Between 2007 and 2013

et al. 2017

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Using data from Time History of Events and Macroscale Interactions during Substorms (THEMIS), a statistical study was performed to determine whether a dawn‐dusk asymmetry exists in the occurrence rates of the Kelvin‐Helmholtz instability during Parker‐Spiral (PS) and Ortho‐Parker‐Spiral (OPS) orientations of the interplanetary magnetic field (IMF). It is determined from the data that there is a strong preference toward the dawnside during PS orientation, and although a preference to the duskside during OPS is suggested, this requires further study for an unambiguous confirmation. The uncertainty in the OPS result is due to a low number of events, which satisfied our selection criteria. Because IMF is statistically in PS orientation, the Kelvin‐Helmholtz instability (KHI) preference for the dawn flank during this orientation may help explain the origin of the plasma sheet asymmetry of cold component ions because it has been shown that KHI can drive kinetic‐scale wave activity capable of ion heating.

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Dawn–dusk asymmetries in the coupled solar wind–magnetosphere–ionosphere system: a review

Cited by 77 publications

References 246 publications

Ion nose spectral structures observed by the Van Allen Probes

Ion nose spectral structures observed by the Van Allen Probes

Outflow of low‐energy ions and the solar cycle

On the Dawn‐Dusk Asymmetry of the Kelvin‐Helmholtz Instability Between 2007 and 2013

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