Influence of anisotropic F region ion velocity distributions on ionospheric ion outflows into the magnetosphere

Journal Article · Wed Feb 01 04:00:00 EST 1989 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA094iA02p01347· OSTI ID:6191726

Suvanto, K; Lockwood, M; Fuller-Rowell, T J

The contribution to the field-aligned ionospheric ion momentum equation, due to coupling between pressure anisotropy and the inhomogeneous geomagnetic field, is investigated. We term this contribution the ''hydrodynamic mirror force'' and investigate its dependence on the ion drift and the resulting deformations of the ion velocity distribution function from an isotropic form. It is shown that this extra upforce increases rapidly with ion drift relative to the neutral gas but is not highly dependent on the ion-neutral collision model employed. An example of a burst of flow observed by EISCAT, thought to be the ionospheric signature of a flux transfer event at the magnetopause, is studied in detail and it is shown that the nonthermal plasma which results is subject to a hydrodynamic mirror force which is roughly 10% of the gravitational downforce. In addition, predictions by the coupled University College London: Sheffield University model of the ionosphere and thermosphere show that the hydrodynamic mirror force in the auroral oval is up to 3% of the gravitational force for Kp of about 3, rising to 10% following a sudden increase in cross-cap potential. The spatial distribution of the upforce shows peaks in the cusp region and in the post-midnight auroral oval, similar to that of observed low-energy heavy ion flows from the ionosphere into the magnetosphere. We suggest the hydrodynamic mirror force may modulate these outflows by controlling the supply of heavy ions to regions of ion acceleration and that future simulations of the effects of Joule heating on ion outflows should make allowance for it. copyright American Geophysical Union 1989

• Research Organization: Blackett Laboratory, Imperial College, London
• OSTI ID: 6191726
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 94:A2; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
AURORAL OVAL
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
F REGION
FUNCTIONS
ION DRIFT
ION TEMPERATURE
IONOSPHERE
MAGNETOPAUSE
PLANETARY IONOSPHERES
PLASMA ACCELERATION