Heating of the polar wind due to ion beam instabilities

Journal Article · Thu Nov 01 00:00:00 EST 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA11p18949· OSTI ID:5132770

Chen, M W; Ashour-Abdalla, M ^[1]

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1. Univ. of California, Los Angeles (United States)

In the classical theory of the polar wind, there is a significant outflow of cold supersonic H{sup +} and limited O{sup +} from the polar ionosphere. Recent DE 1 observations in the polar cap region report upflowing field-aligned H{sup +} and O{sup +} beams ({approximately} 10 eV) which may interact with the polar wind. The source of these ion beams may be energetic ions in the dayside polar cusp that E {times} B convect into the polar cap region. These ion beams provide free energy to the polar wind which will alter its classical description. In the study described here, the linear as well as the nonlinear effects of O{sup +} and H{sup +} ion beams on an O{sup +} and H{sup +} polar wind are investigated. The O{sup +} and H{sup +} polar wind ions are modeled by isotropic Maxwellian distributions while the electrons, O{sup +} beam ions, and H{sup +} beam ions are modeled by drifting Maxwellian distributions. The electrostatic dispersion relation is solved for a range of O{sup +}/H{sup +} beam densities, T{sub e}/T{sub i}, and ion beam speeds. There is a parameter regime consistent with observations in which O{sup +} beam modes such as the slow O{sup +} acoustic and slow O{sup +} cyclotron modes are excited with growth rates {gamma} {approximately} {Omega}{sub O} while H{sup +} beam modes are damped. Simulations show that these O{sup +} beam modes heat both the O{sup +} and H{sup +} polar wind ions in the perpendicular direction. In fact, the O{sup +} ions are preferentially heated over the H{sup +} ions. This preferential heating of O{sup +} ions has important implications because it enhances the outflow of O{sup +} ions along polar cap field lines by effectively increasing the O{sup +} scale height.

• OSTI ID: 5132770
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:A11; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
OXYGEN IONS
HEATING
POLAR REGIONS
ION DRIFT
ACCELERATION
DAMPING
DISPERSION RELATIONS
FREE ENERGY
ION BEAMS
IONOSPHERE
MASS TRANSFER
MATHEMATICAL MODELS
POLAR CUSP
PROTONS
BARYONS
BEAMS
CHARGED PARTICLES
EARTH ATMOSPHERE
ELEMENTARY PARTICLES
ENERGY
FERMIONS
HADRONS
IONS
NUCLEONS
PHYSICAL PROPERTIES
PLANETARY IONOSPHERES
THERMODYNAMIC PROPERTIES
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena