A statistical analysis of the low-energy geosynchronous plasma environment—II. Ions

Garrett, Henry; Schwank, D. C.; Deforest, S. E.

doi:10.1016/0032-0633(81)90002-7

Cited by 25 publications

(5 citation statements)

References 9 publications

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“…This feature makes the hot‐ion density have a clear asymmetric LT distribution around Dst * min during storms, which is also noted by several previous studies [e.g., Korth et al , 1999; Liemohn et al , 2001; Fok et al , 2003; Ebihara et al , 2005; Denton et al , 2005, 2006]. However, during low geomagnetic activity, it was found that hot‐ion density peaks near local midnight, drops toward both dawn and dusk and is minimized near noon [ DeForest and McIlwain , 1971; Garrett et al , 1981; Thomsen et al , 1996b; Maurice et al , 1998]. This quiet‐time LT variation is consistent with those in the first and last 12 epoch hours on the density LT‐UT maps in Figures 3–6.…”

Section: Results: Similarities and Differencessupporting

confidence: 63%

“…Moreover, ions detected by MPA have a distinct population separation at the energy level of ∼100 eV [ McComas et al , 1993]. The low‐energy (≤100 eV) ion populations are believed to originate from the ionosphere [e.g., Reasoner et al , 1983; Moldwin et al , 1994], while the high‐energy (>100 eV) ones are those in the inner plasma sheet [e.g., Gurnett and Frank , 1974; Garrett et al , 1981] or in the ring current [e.g., Balsiger et al , 1980]. In the present paper, we study the average behaviors of fluxes in four energy channels (ϕ with energies ∼30, ∼18, ∼7, and ∼1 keV) and several derived bulk properties of hot ions before and during storm events.…”

Section: Data Processingmentioning

confidence: 99%

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A statistical comparison of hot‐ion properties at geosynchronous orbit during intense and moderate geomagnetic storms at solar maximum and minimum

Zhang¹,

Liemohn²,

Thomsen³

et al. 2006

J. Geophys. Res.

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Hot‐ion measurements at geosynchronous orbit from the Los Alamos Magnetospheric Plasma Analyzer (MPA) instrument during geomagnetic storms at solar maximum (July 1999–June 2002) and at solar minimum (July 1994–June 1997) are collected, categorized, and analyzed through the superposed epoch technique. To investigate this source of the storm‐time ring current, the local time (LT) and universal time (UT) dependence of the average variations of hot‐ion fluxes (at the energies of ∼30, ∼17, ∼8, and ∼1 keV), density, temperature, entropy, and temperature anisotropy are examined and compared among four storm categories, i.e., 44 intense storms and 120 moderate storms, defined by the pressure corrected Dst (Dst*), at the two solar extrema. All the hot‐ion parameters are highly disturbed around Dst*min; they show distinct peaks or minima and display obvious increase or decrease regions, whose locations do not change much with levels of geomagnetic activity and solar activity. It is also found that intense storms at solar minimum always have the highest (lowest) average peak value (minimum) in each hot‐ion parameter. Around Dst*min in each storm category, hot ions are clearly denser near dawn than those near dusk. On the nightside and in the afternoon sector, temperature and entropy during solar minimum storms are usually higher than those during solar maximum storms; there is actually no clear temperature and entropy enhancement during solar maximum storms. During each type of storm, hot ions are isotropic on the nightside but anisotropic (Tper/Tpar > 1) close to noon.

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Section: Results: Similarities and Differencessupporting

confidence: 63%

Section: Data Processingmentioning

confidence: 99%

A statistical comparison of hot‐ion properties at geosynchronous orbit during intense and moderate geomagnetic storms at solar maximum and minimum

Zhang¹,

Liemohn²,

Thomsen³

et al. 2006

J. Geophys. Res.

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“…This discrepancy may be due to differences in the energy ranges of the instruments and the method chosen for the moments calculation. The ATS 6 proton density curve differs vastly from the other measurements because it includes measurements that extend down to • 1 eV, whereas ATS 5 extends down to 50 eV [Garrett et al, 1981b] The qualitative dependence of the MPA electron density on local time is in agreement with both the ATS 5 and ATS 6 measurements, although the absolute value is instrument dependent (Figure 4b). Furthermore, the independence of the MPA electron density on the Kp index in the range shown in the graph agrees with the results of the ATS study [cf.…”

Section: Density On the Nightside The Density Profiles (Plates 4a Ansupporting

confidence: 60%

Plasma sheet access to geosynchronous orbit

Korth¹,

Thomsen²,

Borovsky³

et al. 1999

J. Geophys. Res.

181

291

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“…Previous multisatellite studies at geosynchronous orbit have been somewhat ambiguous about this point. For instance, in their study of the distribution at geosynchronous orbit of 1 eV-80keV ions, Garrett et al [1981Garrett et al [ , p. 1047 used plasma data collected by ATS 5 and ATS 6. Their analysis of the density .distribution as a function of local time gave interesting results but suffered from the problem: "the ATS 5 and ATS 6 ion data are not ... easily reconciled."…”

Section: Using Measurements From Three Satellites Improvesmentioning

confidence: 99%

Quiet time densities of hot ions at geosynchronous orbit

Maurice¹,

Thomsen²,

McComas³

et al. 1998

J. Geophys. Res.

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Abstract. Densities of hot (100eV-40keV) ions vary with local time at geosynchronous orbit. Typically, the density is maximum near midnight, falls off toward both terminators, and is minimum near noon. This local time dependence is routinely observed in the Los Alamos geosynchronous plasma data. We use a month of these data (June 1996) and a simple model of particle drifts within the magnetosphere to explore its origins. We first show that the nightside density profile is shaped according to the drift path topology: trapped orbits are depleted, and only particles drifting on open trajectories contribute to this population, particularly for observations taken at times of low Kp. Then, we highlight spectral absorption in dayside fluxes, which occurs when the particles pass through the geocorona. A model of charge exchange accounts for the shape and energy range of the absorption signatures observed at low Kp for varying pitch angles. The density absorption computed versus local time matches the observations. Hence these basic principles of particle motion in the terrestrial magnetosphere readily explain the local time dependence of the hot ion density at geosynchronous orbit.

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A statistical analysis of the low-energy geosynchronous plasma environment—II. Ions

Cited by 25 publications

References 9 publications

A statistical comparison of hot‐ion properties at geosynchronous orbit during intense and moderate geomagnetic storms at solar maximum and minimum

A statistical comparison of hot‐ion properties at geosynchronous orbit during intense and moderate geomagnetic storms at solar maximum and minimum

Plasma sheet access to geosynchronous orbit

Quiet time densities of hot ions at geosynchronous orbit

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