Ion composition and energy distribution during 10 magnetic storms

Abstract

Data from the plasma composition experiment on ISEE 1 were used to investigate the relative quantities and energy characteristics of H+, He++, He+, and O+ in the near‐equatorial magnetosphere at R ≤15 RE during magnetic storms, principally during the early main phase. The ions included in this study had energies in the range of 0.1 ≤E/Q ≤17 keV/e. The number densities were characterized by a large to dominant fraction of terrestrial ions throughout this energy window. Terrestrial O+ ions were most clearly identified, but strong evidence for a significant contribution of terrestrial H+ ions was also found. On occasions, the O+ alone contributed 50% or more of the integral number density, as well as the energy density, over distances of several earth radii along the orbit. The largest fractions of O+ (≲75%) and He+ (≲25%) were found at R <3 RE (L <5). In general, the He+ only represented a few percent, however. Small fractions of O+ (<10%) and He+ (<1%) were mostly found in the 0100‐0600 LT sector, at R ≳7 RE. The He++ was often obscured by background and rarely exceeded 2%, except in the 0100–0600 LT sector, at R ≳7 RE, where it reached several percent relatively frequently, suggesting a larger solar wind component here. It is argued, based on certain signatures in the energy spectra, that solar wind ions may enter the inner magnetosphere through this region and thereby contribute a larger portion of the high‐energy ring current population (50–100 keV). The data do not suggest, however, that the solar wind is always the dominant source of ions for the high‐energy ring current.

Multifluid Block‐Adaptive‐Tree Solar wind Roe‐type Upwind Scheme: Magnetospheric composition and dynamics during geomagnetic storms—Initial results

“…Observational studies of composition also are in accord with our results. Work by Lennartsson et al [1981] examined composition data inside of 15 R e from the ISEE 1 satellite for 10 geomagnetic and found that O + can up as much as 80% of the entire ion population, a result consistent with our simulation.…”

Multifluid Block‐Adaptive‐Tree Solar wind Roe‐type Upwind Scheme: Magnetospheric composition and dynamics during geomagnetic storms—Initial results

“…Observational studies of composition also are in accord with our results. Work by Lennartsson et al [1981] examined composition data inside of 15 R e from the ISEE 1 satellite for 10 geomagnetic and found that O + can up as much as 80% of the entire ion population, a result consistent with our simulation.…”

A comparison of the 0.1–17 keV/e ion composition in the near equatorial magnetosphere between quiet and disturbed conditions

“…Assuming that the O+/H + ratio of the ionospheric contribution remains roughly the same during both quiet and disturbed conditions, one would expect a strongly increasing number of O + ions to be accompanied by a decrease in the He++/H + ratio, since by all evidences the He ++ is primarily of solar wind origin [cf. Balsiger et al, 1980;Lennartsson et al, 1981]. This is inconsistent with Figures 4 and 7, The present set of data from L > 5 would seem selfconsistent if a strong correlation did indeed exist between the O+/H + ratio in the ionospheric particle source and the early main phase of major magnetic storms.…”

“…It increases markedly in both relative and absolute numbers during the early main phase of the magnetic storms. This increase occurs at all local times, although, on the average, the increase at large L is less pronounced in the 0100-0600 LT sector than at other local times [Lennartsson et al, 1981]. A similar storm-related increase of the O + was previously found in the GEOS data [Balsiger et al, 1980].…”

Field‐aligned currents as a diagnostic tool: Result, a renovated model of the magnetosphere

“…1. There is a local time variation in ionic composition of the plasma sheet and ring current plasma such that it is concluded that the solar wind makes a significant contribution in the predawn sector [Lennartson et al, 1981;Hultqvist, 1982] and in the postdawn sector [Balsiger et al, 1980;Balsiger, 1981]. This is entirely consistent with the favored model.…”

Multifluid Block‐Adaptive‐Tree Solar wind Roe‐type Upwind Scheme: Magnetospheric composition and dynamics during geomagnetic storms—Initial results

“…Observational studies of composition also are in accord with our results. Work by Lennartsson et al [1981] examined composition data inside of 15 R e from the ISEE 1 satellite for 10 geomagnetic and found that O + can up as much as 80% of the entire ion population, a result consistent with our simulation.…”

A comparison of the 0.1–17 keV/e ion composition in the near equatorial magnetosphere between quiet and disturbed conditions

“…Assuming that the O+/H + ratio of the ionospheric contribution remains roughly the same during both quiet and disturbed conditions, one would expect a strongly increasing number of O + ions to be accompanied by a decrease in the He++/H + ratio, since by all evidences the He ++ is primarily of solar wind origin [cf. Balsiger et al, 1980;Lennartsson et al, 1981]. This is inconsistent with Figures 4 and 7, The present set of data from L > 5 would seem selfconsistent if a strong correlation did indeed exist between the O+/H + ratio in the ionospheric particle source and the early main phase of major magnetic storms.…”

“…It increases markedly in both relative and absolute numbers during the early main phase of the magnetic storms. This increase occurs at all local times, although, on the average, the increase at large L is less pronounced in the 0100-0600 LT sector than at other local times [Lennartsson et al, 1981]. A similar storm-related increase of the O + was previously found in the GEOS data [Balsiger et al, 1980].…”

Field‐aligned currents as a diagnostic tool: Result, a renovated model of the magnetosphere

“…1. There is a local time variation in ionic composition of the plasma sheet and ring current plasma such that it is concluded that the solar wind makes a significant contribution in the predawn sector [Lennartson et al, 1981;Hultqvist, 1982] and in the postdawn sector [Balsiger et al, 1980;Balsiger, 1981]. This is entirely consistent with the favored model.…”

Multifluid Block‐Adaptive‐Tree Solar wind Roe‐type Upwind Scheme: Magnetospheric composition and dynamics during geomagnetic storms—Initial results

“…Observational studies of composition also are in accord with our results. Work by Lennartsson et al [1981] examined composition data inside of 15 R e from the ISEE 1 satellite for 10 geomagnetic and found that O + can up as much as 80% of the entire ion population, a result consistent with our simulation.…”

A comparison of the 0.1–17 keV/e ion composition in the near equatorial magnetosphere between quiet and disturbed conditions

“…Assuming that the O+/H + ratio of the ionospheric contribution remains roughly the same during both quiet and disturbed conditions, one would expect a strongly increasing number of O + ions to be accompanied by a decrease in the He++/H + ratio, since by all evidences the He ++ is primarily of solar wind origin [cf. Balsiger et al, 1980;Lennartsson et al, 1981]. This is inconsistent with Figures 4 and 7, The present set of data from L > 5 would seem selfconsistent if a strong correlation did indeed exist between the O+/H + ratio in the ionospheric particle source and the early main phase of major magnetic storms.…”

“…It increases markedly in both relative and absolute numbers during the early main phase of the magnetic storms. This increase occurs at all local times, although, on the average, the increase at large L is less pronounced in the 0100-0600 LT sector than at other local times [Lennartsson et al, 1981]. A similar storm-related increase of the O + was previously found in the GEOS data [Balsiger et al, 1980].…”

Field‐aligned currents as a diagnostic tool: Result, a renovated model of the magnetosphere

“…1. There is a local time variation in ionic composition of the plasma sheet and ring current plasma such that it is concluded that the solar wind makes a significant contribution in the predawn sector [Lennartson et al, 1981;Hultqvist, 1982] and in the postdawn sector [Balsiger et al, 1980;Balsiger, 1981]. This is entirely consistent with the favored model.…”