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Rishbeth, H.

Publications and source records attributed to Rishbeth, H..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

How the effects of winds and electric fields in F2-layer storms vary with latitude and longitude - A theoretical study

The effects of thermospheric winds and electric fields on the ionospheric F2-layer are controlled by the geometry of the magnetic field, and so vary with latitude and longitude. A simple model of the daytime F2-layer is adopted and the effects at midlatitudes (25-65 deg geographic) of three processes that accompany geomagnetic storms: (1) thermospheric changes due to auroral heating; (2) equatorward winds that tend to cancel the quiet-day poleward winds; and (3) the penetration of magnetospheric electric fields are studied. At +/- 65 deg, the effects of heating and electric fields are strongest in the longitudes toward which the geomagnetic dipole is tilted, i.e., the North American and the South Indian Ocean sectors. Because of the proximity of the geomagnetic equator to the East Asian and South American sectors, the reverse is true at +/- 25 deg.

Mendillo, M.↗
NASA NTRS1986

The quadrupole ionosphere

The principal features that might exist in the terrestrial paleoionosphere, if the geomagnetic field were to assume a quadrupole form during a polarity reversal are discussed. Complicated phenomena would be expected to occur at magnetic equators and magnetospherically-driven plasma convection might occur at latitudes where the magnetic field is steeply inclined. The influence of magnetic field strength on ionospheric structure is considered in general terms.

Rishbeth, H.↗
NASA NTRS1986

EISCAT velocity patterns for theoretical plasma convection models

Theoretical line-of-sight velocities, as would be observed by the EISCAT radar, are computed for idealized models of plasma convection in the polar ionosphere. The calculations give the velocity as a function of range and Universal Time. For several variants of the Volland and Heelis convection models, how the maxima, minima and reversals of velocity depend on beam azimuth is examined. The analysis is designed to be applied to data from the UK-POLAR experiment, an example of which is shown.

Rishbeth, H.↗
NASA NTRS1980

The dynamic F2-layer over Arecibo

The idealized 'servo' model of the ionospheric F2-layer of Rishbeth et al. (1978) is used to simulate the observed behavior of the daytime Fe-peak at Arecibo at sunspot minimum. The meridional pressure-gradient force associated with the meridional neutral-air wind is determined empirically. The local time variation during the day is found to be consistent with the semidiurnal variation given by the MSIS atmospheric model of Hedin et al. (1977). The values of the F2-layer loss and diffusion coefficients needed to match the data are broadly consistent with the MSIS model.

Ganguly, S.↗
NASA NTRS1978

Field-aligned and field-perpendicular velocities in the ionospheric F2-layer

The correlation between variations in the components of the ionospheric F2-layer parallel and perpendicular to the geomagnetic field is theoretically examined. The servo model of Rishbath (1967) is used as a basis for further calculations. The equations involved are presented in full and results are given for various assumed conditions. The response of the model to both steplike and periodic perturbations of the perpendicular component is considered along with the effects of winds and the Coriolis force. Arecibo and Malvern data are reviewed on the basis of theoretically predicted behavior.

Rishbeth, H.↗
NASA NTRS1977

Ion temperature troughs in the equatorial topside ionosphere

It is noted that the retarding potential analyzer aboard OGO 6 sometimes records pronounced minima of ion temperature when the satellite crosses the magnetic equator and that the variation of ion temperature along the satellite path takes the form of a trough about 20 to 30 deg wide in latitude and up to 1200 K in depth. Observations of night-time, daytime, and dawn-dusk ion-temperature troughs are discussed along with ion concentration and composition in the troughs, ion drift velocities, and comparisons with Jacchia's (1971) thermospheric model. An explanation of trough morphology is given in terms of thermospheric winds which produce a transequatorial plasma flow along geomagnetic field lines. The effect of such a plasma flow on 630-nm nightglow is considered, and it is shown how ion composition affects the extent of ion-temperature troughs. Some questions for further study are suggested.

Rishbeth, H.↗
NASA NTRS1974

A comment on plasma 'pile-up' in the F-region

At ionospheric heights, the geomagnetic field is virtually incompressible. In consequence, an electromagnetic drift can only compress the F-region plasma by moving it in a direction in which the field becomes stronger. This paper examines the rate of compression at mid-latitudes for three different assumptions about the ion motion.

Rishbeth, H.↗
NASA NTRS1972

Molecular ions in the F2 layer.

Data on ion concentrations at heights of 400-500 km, obtained by the OGO VI satellite, suggest that the O(+) and molecular ion concentrations are sometimes anticorrelated. To assist in explaining this phenomenon, a table of the chemical reactions most likely to control the molecular ion concentrations is drawn up, and its validity tested with the aid of data from rocket-borne mass spectrometers at heights of 220-400 km. The anticorrelation of O(+) and NO(+) ions by day is thought to be due to the importance of a reaction between N2(+) ions and O atoms; the main source of N2(+) above 300 km is probably charge-exchange between N2 and O(+), the latter being produced by photoionization. However, at night another source of NO(+) ions is required, which may be N(+) ions that are either stored in the magnetosphere or are produced from He(+) and N2.

Rishbeth, H.↗
NASA NTRS1969

Introduction to Ionospheric Physics

Book on ionospheric physics covering neutral atmosphere, ionospheric measurements, photochemical processes, morphology, phenomena, geomagnetism, storms, etc

Garriott, O. K.↗