The Effects of Changing Solar Euv Flux Upon The Location and Structure of The Dayside High-latitude Trough In Winter: Modelling Results and Experimental Validation
Abstract
The effects of changing solar EUV flux upon the location and structure of the dayside high-latitude trough are investigated, using a combination of modelling studies and ex- perimental ionospheric tomography. An increase in the EUV radiation incident upon the atmosphere causes thermal expansion, and an increase in ionisation. This drives ionospheric features such as troughs to a greater height. However, such behaviour is further complicated by increased solar activity changing the chemical composition of the atmosphere, and the fact that many of the chemical reactions of importance to the ionosphere are temperature dependent. Since a complete understanding of the variation of ionospheric temperature with solar activity remains elusive, the effects of the above processes upon the dayside high-latitude trough cannot be predicted. In the present paper results from theoretical modelling using the Coupled Thermosphere- Ionosphere-Plasmasphere model are compared with tomographic observations of the ionosphere. Calculations have been performed for low, medium and high solar activ- ity and compared with tomographic reconstructions of ionospheric electron density, taken under broadly similar conditions, when geomagnetic activity was low. The re- sults show that the trough is driven polewards in latitude, and that the density gradient equatorwards of the trough increases significantly, as solar activity increases. How- ever, the basic structure and form of the trough are little changed. There is broad agreement between the CTIP modelling calculations and the experimental tomogra- phy observations.
- Publication:
-
EGS General Assembly Conference Abstracts
- Pub Date:
- 2002
- Bibcode:
- 2002EGSGA..27.1388D