scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Short term variability of the high and mid latitude ionosphere as a result of coupling
between the solar wind and magnetosphere
Lester Mark , Milan Stephen
University of Leicester
Ionospheric variability occurs on a range of time scales from days to years and probably
centuries. In this talk we focus on the variability which is introduced by the coupling between
the solar wind and magnetosphere. This coupling introduces variability on time scales of
hours, due to magnetospheric substorms, and days, due to magnetic storms. The changes in
the ionosphere are due to enhanced energy deposition into the ionosphere in the form of
particle precipitation which results in heating of the plasma and also enhanced electric field
resulting in Joule heating of the plasma. At high latitudes the changes in the ionospheric
plasma result from the enhanced ionisation from particle precipitation, which can lead to
enhanced absorption of radio waves should the particles penetrate to altitudes of 100 km and
less. Joule heating on the other hand leads to enhanced temperatures in the ionosphere
resulting in enhanced ion loss from either ion upflow or from enhanced recombination. This
tends to occur at altitude above about 250 km. At mid-latitudes the variability during
substorms may be more related to the propagation of atmospheric gravity waves stimulated by
the heating at cusp latitudes or auroral latitudes on the nightisde. These waves propagate to
mid and low latitudes resulting in variation in the ionospheric plasma density on time scales
of hours. Mid-latitude variations due to storms are extremely complex due to transport of
plasma due to winds. In this presentation we shall concentrate on observations of the
ionosphere made by the Super Dual Auroral Radar Network (SuperDARN) which extends
from the poles to about 40 degrees of latitude in both hemispheres. These radars provide
information on the electric fields responsible for Joule heating, ionospheric plasma
distributions, in particular enhanced absorption and changes in the F region peak density, and
gravity waves. With the continued extension to mid latitudes particularly in the American
sector, these radars now provide critical information on the ionospheric variability on the
short term.