Inference of the ring current ion composition by means of charge exchange decay

Smith, Paul H.; Bewtra, N. K.; Hoffman, R. A.

doi:10.1029/ja086ia05p03470

Cited by 54 publications

(27 citation statements)

References 26 publications

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“…On the other hand, the lower energy protons also decay much faster than those of higher energies. This is consistent with previous studies on the charge exchange lifetimes of ions with different energies [Smith and Bewtra, 1978;Smith et al, 1981], which showed that the charge exchange lifetime of protons increases with proton for energies >~10 keV, although the original studies only focused on energies up to~100 keV.…”

Section: 1002/2015ja021533supporting

confidence: 81%

The evolution of ring current ion energy density and energy content during geomagnetic storms based on Van Allen Probes measurements

et al. 2015

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Enabled by the comprehensive measurements from the Magnetic Electron Ion Spectrometer (MagEIS), Helium Oxygen Proton Electron mass spectrometer (HOPE), and Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instruments onboard Van Allen Probes in the heart of the radiation belt, the relative contributions of ions with different energies and species to the ring current energy density and their dependence on the phases of geomagnetic storms are quantified. The results show that lower energy (<50 keV) protons enhance much more often and also decay much faster than higher‐energy protons. During the storm main phase, ions with energies <50 keV contribute more significantly to the ring current than those with higher energies; while the higher‐energy protons dominate during the recovery phase and quiet times. The enhancements of higher‐energy proton fluxes as well as energy content generally occur later than those of lower energy protons, which could be due to the inward radial diffusion. For the 29 March 2013 storm we investigated in detail that the contribution from O+ is ~25% of the ring current energy content during the main phase and the majority of that comes from <50 keV O+. This indicates that even during moderate geomagnetic storms the ionosphere is still an important contributor to the ring current ions. Using the Dessler‐Parker‐Sckopke relation, the contributions of ring current particles to the magnetic field depression during this geomagnetic storm are also calculated. The results show that the measured ring current ions contribute about half of the Dst depression.

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Section: 1002/2015ja021533supporting

confidence: 81%

The evolution of ring current ion energy density and energy content during geomagnetic storms based on Van Allen Probes measurements

et al. 2015

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“…The difference in the values of z during the main and recovery phases of magnetic storms is due to the prevailing mechanisms of ring-current decay, namely, the interaction with hydromagnetic waves during injections (Cornwall et al, 1970;Bespalov et al, 1989) and the charge exchange with the geocoronal hydrogen during recovery phase (Smith and Bewtra, 1978).…”

Section: The Results Of Modelling the Hourly Mean Values Of The Stormmentioning

confidence: 98%

“…Calculating the pitch-angle diffusion of ions in resonance with ion-cyclotron waves has shown that the resonance ion lifetime is a few hours. The ion-wave interactions seem to define the r value during the storm main phase, but must be allowed for also during the recovery phase when the processes of energetic ion charge exchange with neutral hydrogen constitute the principal mechanism of ion loss from ring current (Smith and Bewtra, 1978). The position of the region of the most intensive wave-particle interactions changes throughout a storm.…”

Section: Dr(t)mentioning

confidence: 98%

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Modelling of the magnetic field of magnetospheric ring current as a function of interplanetary medium parameters

Feldstein

1992

Space Sci Rev

102

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Abstract. The models are examined which are proposed elsewhere for describing the magnetic field dynamics in ring-current DR during magnetic storms on the basis of the magnetospheric energy balance equation. The equation parameters, the functions of injection F and decay % are assumed to depend on interplanetary medium parameters (F and r during the storm main phase) and on ring-current intensity (z during the recovery phase). The present-day models are shown to be able of describing the DR variations to within a good accuracy (the r.m.s, deviation 5 < b < 15 nT, the correlation coefficient 0.85 < r < 1). The models describe a fraction of the geomagnetic field variation during a magnetic storm controlled by the geoeffective characteristic of interplanetary medium and, therefore responds directly to the variation of the latter. The fraction forms the basis of the geomagnetic field variations in low and middle latitudes. The shorter-term variations of DR are affected by the injections into the inner magnetosphere during substorm intervals.During magnetic storms, the auroral electrojets shift to subanroral latitudes. When determining the AE indices, the data from the anroral-zone stations must be supplemented with the data from subauroral observatories. Otherwise, erratic conclusions may be obtained concerning the character of the relationships of DR to AE or of AE to interplanetary medium parameters. Considering this circumstance, the auroral electrojet intensity during the main phase is closely related to the energy flux supplied to the ring current. It is this fact that gives rise simultaneously to the intensification of auroral electrojets and to the large-scale decrease of magnetic field in low latitudes.The longitudinal asymmetry of magnetic field on the Earth's surface is closely associated with the geoeffective parameters of interplanetary medium, thereby making it possible to model-estimate the magnetic field variations during magnetic storms at given observatories. The inclusion of the field asymmetry due to the system of large-scale currents improves significantly the agreement between the predicted and model field variations at subauroral and midlatitude observatories. The first harmonic amplitude of field variation increases with decreasing latitude. This means that the long-period component of the Ds,-variation asymmetry is due rather to the ring-current asymmetry, while the shorter-term fluctuations are produced by electrojets. The asymmetry correlates better with the AL indices (westward electrojet) than with the A U indices (eastward electrojet).The total ion energy in the inner magnetosphere during the storm main phase is sufficient for the magnetic field observed on the Earth's surface to be generated. The energy flux to the ring current is ~ 15 ~ of the e-energy flux into the magnetosphere.

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“…An accepted explanation is that there are losses along the drift paths. The main loss mechanism for energetic (keV) ions is charge exchange with the neutral hydrogen geocorona [ Lyons and Evans , ; Tinsley , ; Smith and Bewtra , ; Smith et al ., ; Fok et al ., ; Sheldon and Hamilton , ; Noël , ]. Kistler et al .…”

Section: Introductionmentioning

confidence: 99%

Heavy‐ion dominance near Cluster perigees

et al. 2015

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Time periods in which heavy ions dominate over H+ in the energy range of 1–40 keV were observed by the Cluster Ion Spectrometry (CIS)/COmposition DIstribution Function (CODIF) instrument onboard Cluster Spacecraft 4 at L values less than 4. The characteristic feature is a narrow flux peak at around 10 keV that extends into low L values, with He+ and/or O+ dominating. In the present work we perform a statistical study of these events and examine their temporal occurrence and spatial distribution. The observed features, both the narrow energy range and the heavy‐ion dominance, can be interpreted using a model of ion drift from the plasma sheet, subject to charge exchange losses. The narrow energy range corresponds to the only energy range that has direct drift access from the plasma sheet during quiet times. The drift time to these locations from the plasma sheet is > 30 h, so that charge exchange has a significant impact on the population. We show that a simple drift/loss model can explain the dependence on L shell and MLT of these heavy‐ion‐dominant time periods.

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Inference of the ring current ion composition by means of charge exchange decay

Cited by 54 publications

References 26 publications

The evolution of ring current ion energy density and energy content during geomagnetic storms based on Van Allen Probes measurements

The evolution of ring current ion energy density and energy content during geomagnetic storms based on Van Allen Probes measurements

Modelling of the magnetic field of magnetospheric ring current as a function of interplanetary medium parameters

Heavy‐ion dominance near Cluster perigees

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