Identification

Title

Ion-neutral coupling effects on low-latitude thermospheric evening winds

Abstract

We examine the forces that determine zonal wind structure in the low-latitude evening thermosphere and its relation with ion-neutral coupling. These winds drive the evening F region dynamo that affects the equatorial ionization anomaly (EIA) and the generation of plasma irregularities. Forces are calculated using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model coupled with the Global Ionosphere-Plasmasphere model. At 19 LT, the horizontal pressure gradient dominates the net acceleration of neutral winds below ∼220 km, while it tends to be offset by ion drag and viscosity higher up. The eastward pressure-gradient acceleration above 200 km increases approximately linearly with height and tends to be similar for different latitudes and different levels of solar activity. The pressure-gradient and ion-drag forces in the central F region approximately balance for field lines that pass through the EIA. Viscosity is an important additional force at non-EIA latitudes and in the bottomside and topside EIA ionosphere. An increase in E region drag on plasma convection due to increased nighttime ionization causes both the ion and neutral velocities in the F region to decrease, while the velocity difference tends to be maintained. The presence of a low-latitude evening time vertical shear in the zonal wind is associated primarily with a strong eastward pressure-gradient acceleration at high altitude that reverses the daytime westward wind and a weak low-altitude pressure-gradient acceleration of either eastward or westward direction that fails to reverse the low-altitude westward wind present in the afternoon.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7g73gd6

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

North bounding latitude

South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2016-05-01T00:00:00Z

Frequency of update

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Conformity

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version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact