The Changing Polar Ionosphere: A Comparative Climatology of Solar Cycles 23 and 24

The polar ionosphere has a range of effects on technological systems produced by the coupling of the solar wind with the magnetosphere, and the resulting electrodynamic interaction between magnetosphere, ionosphere and atmosphere. These effects include the degradation of trans-ionospheric satellite communications and point-to-point radio communications, clutter effects in over-the-horizon radars, and increased levels (and decreased predictability) of satellite drag.

Such effects are known to be strongly influenced by the activity level of the sun, and hence the phase of the 11-year solar activity cycle. Recent changes in solar activity have taken the scientific community by surprise, in that the recent solar minimum was both extended in time, and much lower in activity than predicted. As we now approach solar maximum we see an increasing solar activity, but this rise in activity is also less than expected.

We propose an extensive statistical investigation of the profound changes imposed on a number of fundamental ionospheric characteristics by the changing solar cycle, focussing on the inter-cycle differences between solar cycle 23, a "standard" solar cycle, and the most recent, unusual solar cycle 24.

Furthermore, we will extend this analysis of solar cycle dependence and inter-cycle differences to a number of ionospheric and atmospheric characteristics which have a direct effect on the operational characteristics of key technologies such as trans-ionospheric communication, satellite navigation and radar systems.

This major step forward in defining and understanding these effects and their dependence on the level of solar activity will allow a prediction of their consequences for the polar ionosphere and atmosphere, and for the technological systems we operate in the polar regions.

The impact of the proposed research will be focussed on the following groups:

HF users. The ionospheric density at high latitudes plays a critical role in the availability of HF communication paths, as used by both civil aviation and the military. Maps of ionospheric morphology as a function of season, solar cycle phase, and the analysis of inter-cycle differences will form important new inputs for users in these areas.

GNSS users. Maps of seasonal, solar cycle, and inter-cycle variations in ionospheric irregularity occurrence will be of direct applicability to the assessment of space weather effects on GPS navigational systems.

Over-the-Horizon radar (OTHR) users. Irregularity occurrence is a major contribution to radar clutter in OTHR systems. The location and intensity of such structures will provide a highly valuable input to enhance our understanding of the operational impact of ionospheric perturbations.

Space infrastructure operators. Thermospheric heating causes the Earth's atmosphere to expand, increasing the atmospheric drag on satellites in low Earth orbits. This increases the risk of spacecraft collisions and results in large uncertainties in the re-entry location of de-orbiting spacecraft.

The ionospheric modelling community. The ionospheric changes dependent on long time-scale variations in solar activity; the effect of inter-cycle variation on future ionospheric structure, and the statistical analysis of ionospheric convection morphology will be of direct applicability as input to the current efforts of the UK global ionospheric modelling community.

Society. The pursuit of scientific discovery and knowledge is a cultural endeavour which enriches society through its power to inspire and educate, and directly contributes to the wider knowledge-based economy.

We will define and disseminate our research results through peer-reviewed publications, through presentations at meetings such as the annual European Space Weather Week, and through the two workshops planned as part of the research programme.

Our outreach activities will continue to be delivered through public events involving, for example, the Planeterela and the National Space Centre.