Observations from Ogo 5 of the thermal ion density and temperature within the magnetosphere

Serbu, G. P.; Maier, E. J.

doi:10.1029/ja075i031p06102

Cited by 75 publications

(30 citation statements)

References 24 publications

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“…The GEOS 1 temperatures, when compared to the analysis of Serbu and Maier [1970], are lower by up to an order of magnitude over almost the entire L range within the plasmasphere, although the trends are qualitatively similar. Comparing our findings with those obtained by Prognoz Gringauz, 1983], we have a plasmasphere which, broadly speaking, consists of, to use their terminology, a "cold zone."…”

Section: Comparison Of Temperature Measurementsmentioning

confidence: 87%

“…Starting with the systematic measurements of ion densities by the low-mass (1 to 6 amu) Bennett radio frequency mass spectrometer on OGO 1 two decades ago [Taylor et al, 1965], there have been numerous efforts using spacecraftborne instruments to characterize the cold plasma population in the Earth's plasmasphere in terms of its composition, and its temperature and density distribution. One major effort at such a characterization was the report by Serbu and Maier [ 1970] Often, only the main mass peaks are sampled, or one mass peak is sampled repeatedly. In such cases, detailed profiles of the ion bulk parameters are obtained for these species.…”

Section: Introductionmentioning

confidence: 99%

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The composition, temperature, and density structure of cold ions in the quiet terrestrial plasmasphere: GEOS 1 results

Farrugia¹,

Young²,

Geiss³

et al. 1989

J. Geophys. Res.

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We present a comprehensive study of the composition, and the density and temperature distributions of the thermal (energy < 110 eV) ion population in the terrestrial plasmasphere under quiet geomagnetic conditions. The data were collected by the Ion Composition Experiment (ICE) on board the European Space Agency's GEOS 1 satellite and cover the period from June 1977 to May 1978. For the data reduction we employ a method based on the modulation of the detector count rates by the rotation of the spacecraft. We find typical quiet time proton densities to vary smoothly between ---102 cm -3 (L • 6) and 2 x 103 cm -3 (L • 3). In the local time sector 1700-2200 the equatorial proton concentration obeys an inverse fourth power dependence with dipole L. He + is a major ionic component in all L ranges investigated. Its concentration relative to H + is highly variable, ranging from ---1% to, on occasion, over 100%. The most frequent values we obtain lie in the range ---2-6%. The averaged variation ofHe + with dipole L in the 1700-2200 local time range shows a somewhat more rapid decrease with increasing L than does H +. The temperatures in the quiet plasmasphere are between 4 x 103 K and 1.5 x 104 K and generally exhibit a slow increase with L value. The average radial temperature gradient near the equator is ---0.15 K/km. The main ionic constituents are usually in thermal equilibrium throughout the plasmasphere. There are indications that the ionic component is in a state of thermal equilibration with the electronic component in the outer plasmasphere. Using alternate passes in the same region, we discuss the poststorm recovery of the plasmasphere on L shells > 4 for both H + and He +. Data are also presented on the minor ions O +, O ++, D +, and He ++. The O + densities around L • 3 are -< 1 cm-3, and the densities of O + + are comparable. Cases are shown where the mass/charge = 2 ion is predominantly D + and others where it is mainly He ++. Typical densities of this ion in the L range 2.6-3.6 are a few tenths per cubic centimeter. With one exception we found these minor ions to share a common temperature with the main constituents of the plasmasphere. The results of our survey are compared with previous studies and with theoretical modeling. In particular, the GEOS 1 H + temperature structure is in substantial agreement with those from the Plasma Composition Experiment (PCE) on ISEE 1 and the retarding ion mass spectrometer (RIMS) on DE 1. We confirm the enhanced O ++ to O + density ratio in the equatorial plasmasphere with respect to values in the mid-latitude ionosphere. Our observations on this ratio are compared with the predictions of three theoretical works. 1. equatorial proton temperatures and densities for the period March-April 1968. Density measurements by the light ion mass spectrometer, also on OGO 5, were given in a series of papers by Chappell and coworkers [Chappell et al., 1970a, b, 1971; Harris et al., 1970; Chappell, 1972] spanning the periods March-April 1968 (for the nightside magnetosphere), June-No...

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Section: Comparison Of Temperature Measurementsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

The composition, temperature, and density structure of cold ions in the quiet terrestrial plasmasphere: GEOS 1 results

Farrugia¹,

Young²,

Geiss³

et al. 1989

J. Geophys. Res.

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“…It is clear that in principle the expression ( [1977] show that on the basis of the expression (60) the charge exchange induced fluxes for equatorial and middle latitudes are more important than the corresponding Jeans flux Fj(H). In their work the density profiles nu and nu+ were made consistent with recent satellite measurements, and realistic temperature profiles were employed [Serbu and Maier, 1970], although the proton profiles did not take into account the effects of reaction (R2) at lower altitudes. It is important to mention that the proton distribution function may depart significantly from Maxwellian.…”

Section: Recent Collisional Models Of Nonthermal Escape Have Considermentioning

confidence: 99%

Modern exospheric theories and their observational relevance

Fahr¹,

Shizgal²

1983

Reviews of Geophysics

113

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A review and critique of present‐day kinetic theory models of planetary exospheres is presented. Models of ionized exospheres, specifically the solar and the terrestrial polar wind, are also discussed. The objective of the paper is to point out the need for a rigorous kinetic theory treatment of the atmosphere in the altitude region between the thermosphere and the exosphere. This is the region where the atmosphere undergoes a transition from a collision‐dominated to a collisionless situation. The various aspects of the exospheric problem are introduced and developed around this main theme. The exospheric problem and its considerable overlap with several related problems in physics and chemistry are noted. The calculation of the velocity distribution function of exospheric constituents with the spherically symmetric collisionless model is then presented. Various modifications of this standard model with regard to planetary rotation, nonuniform exobasic density and temperature distributions, and time‐dependent effects are subsequently discussed and compared. The extent to which collisionless models suffice to explain observational data of planetary exospheres is assessed. This assessment is given in terms of a comparison of density profiles or reduction factors determined with hydrogen and/or helium cells. A comparison of experimental measurements of the diurnal variation of terrestrial atomic hydrogen densities and theoretical models to explain the asymmetry is presented. The collisionless approach is criticized on theoretical grounds for the neglect of a consideration of the transition region and the resulting artificial boundary between the thermosphere and the exosphere. The aim of collisional models with regard to escape‐induced non‐Maxwellian effects, modifications of the temperature structure, nonthermal escape processes, and satellite particle populations from Monte Carlo simulations and/or kinetic theory models based on a Boltzmann equation is discussed, and the various results are compared. The various attempts to introduce collisional concepts are shown to be incomplete, each considering the problem with different objectives. Throughout, the importance of a more rigorous collisional treatment is stressed, in particular with respect to the description of nonthermal escape processes and satellite particle populations which cannot be considered in a collisionless context. The effects of charge exchange reactions, photoionization, and solar radiation pressure on satellite particles are examined. With regard to nonthermal escape processes, the absence of a detailed kinetic theory of product velocity distributions based on a collisional theory is also noted.

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“…We assume the thermal plasma in the plasmasphere to have a temperature Tc = 1 eV, a typical magnetic field B • 0.01 G, and a density nc • 11Y cm -a [Serbu and Maier, 1970;Chappell et al, 1970]…”

Section: Plasma Modelmentioning

confidence: 99%

Gyroharmonic emissions induced by energetic ions in the equatorial plasmasphere

Curtis¹,

Wu²

1979

J. Geophys. Res.

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The general problem of the excitation of ion gyroharmonic electrostatic and electromagnetic waves by energetic ions (E ≳ 0.1 MeV) in a thermal plasma as observed in the earth's plasmasphere is considered. The thermal plasma is taken to be predominantly H+ with trace higher Z ion constituents of ionospheric origin such as He+ and O+. This plasma component has a Maxwellian distribution and supports the waves which may be excited by energetic ions with Z ≳ 1. The energetic ions possess a power law distribution in energy with strong pitch angle anisotropy. Coupling of the free energy source of the energetic ions to the waves is obtained via the velocity dependence of the ion gyrofrequency Ωα. Owing to constraints imposed by free energy coupling, wave amplification, and ion cyclotron damping, the dominant growth rates are found for nearly perpendicularly propagating fast magnetosonic waves closely confined to the magnetic equator. Growth is restricted to frequencies immediately below the ion gyroharmonics by the resonance condition and implies line widths of ∼ 10−3Ωα. The fast magnetosonic waves are found to have a significant electromagnetic component which decreases with increasing gyroharmonic number. The polarization becomes almost entirely electrostatic where the fast magnetosonic and ion Bernstein branches merge above the lower hybrid frequency. When it is compared to observations of ion gyroharmonic emissions, the theory implies that there exist a significant number of charge states for Z ≳ 2 MeV ions in the plasmasphere.

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Observations from Ogo 5 of the thermal ion density and temperature within the magnetosphere

Cited by 75 publications

References 24 publications

The composition, temperature, and density structure of cold ions in the quiet terrestrial plasmasphere: GEOS 1 results

The composition, temperature, and density structure of cold ions in the quiet terrestrial plasmasphere: GEOS 1 results

Modern exospheric theories and their observational relevance

Gyroharmonic emissions induced by energetic ions in the equatorial plasmasphere

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