Solar and seasonal dependence of ion frictional heating
Item
Title (Dublin Core)
Solar and seasonal dependence of ion frictional heating
Description (Dublin Core)
Ion frictional heating constitutes one of the
principal mechanisms whereby energy, originating in the solar wind, is deposited
into the Earth's ionosphere and ultimately the neutral atmosphere. Common
programme observations by the EISCAT UHF radar system, spanning the years 1984
to 1995, provide the basis for a comprehensive statistical study of ion
frictional heating, results of which are documented in this and a previous paper
by the authors. In the present work, the authors demonstrate the solar and
seasonal dependence of the universal time distribution of frictional heating,
and explain these results with reference to corresponding dependences of the ion
velocity. Although EISCAT observes a significant increase in the occurrence of
enhanced ion velocities associated with increased solar activity, the latter
characterised according to the prevailing 10.7 cm solar flux, this is not
reflected to such an extent in the occurrence of frictional heating. It is
suggested that this is a consequence of the decreased neutral atmosphere
response times associated with active solar conditions, resulting from the
higher ionospheric plasma densities present. Seasonal effects on the diurnal
distribution of ion frictional heating are well explained by corresponding
variations in ionospheric convection, the latter principally a result of
geometrical factors. It is noted that, over the entire dataset, the variations
in the unperturbed F-region ion temperature, required to implement the
identification criterion for ion heating, are highly correlated with model
values of thermospheric temperature.<br><br><b>Keywords.</b> Ionosphere (auroral ionosphere;
ionosphere-atmosphere interactions; plasma temperature and density)
principal mechanisms whereby energy, originating in the solar wind, is deposited
into the Earth's ionosphere and ultimately the neutral atmosphere. Common
programme observations by the EISCAT UHF radar system, spanning the years 1984
to 1995, provide the basis for a comprehensive statistical study of ion
frictional heating, results of which are documented in this and a previous paper
by the authors. In the present work, the authors demonstrate the solar and
seasonal dependence of the universal time distribution of frictional heating,
and explain these results with reference to corresponding dependences of the ion
velocity. Although EISCAT observes a significant increase in the occurrence of
enhanced ion velocities associated with increased solar activity, the latter
characterised according to the prevailing 10.7 cm solar flux, this is not
reflected to such an extent in the occurrence of frictional heating. It is
suggested that this is a consequence of the decreased neutral atmosphere
response times associated with active solar conditions, resulting from the
higher ionospheric plasma densities present. Seasonal effects on the diurnal
distribution of ion frictional heating are well explained by corresponding
variations in ionospheric convection, the latter principally a result of
geometrical factors. It is noted that, over the entire dataset, the variations
in the unperturbed F-region ion temperature, required to implement the
identification criterion for ion heating, are highly correlated with model
values of thermospheric temperature.<br><br><b>Keywords.</b> Ionosphere (auroral ionosphere;
ionosphere-atmosphere interactions; plasma temperature and density)
Creator (Dublin Core)
J. A. Davies
M. Lester
I. W. McCrea
Subject (Dublin Core)
Science
Q
Physics
QC1-999
Geophysics. Cosmic physics
QC801-809
Publisher (Dublin Core)
Copernicus Publications
Date (Dublin Core)
1999-05-01T00:00:00Z
Type (Dublin Core)
article
Identifier (Dublin Core)
10.1007/s00585-999-0682-4
0992-7689
1432-0576
https://doaj.org/article/3ce8a426d7144ea2824b2a66e2cd37c3
Source (Dublin Core)
Annales Geophysicae, Vol 17, Pp 682-691 (1999)
Language (Dublin Core)
EN
Relation (Dublin Core)
https://www.ann-geophys.net/17/682/1999/angeo-17-682-1999.pdf
https://doaj.org/toc/0992-7689
https://doaj.org/toc/1432-0576
Provenance (Dublin Core)
Journal Licence: CC BY