The influence of meso-scale flow channels on polar cap patch formation

Every day plasma clouds are created in the upper atmosphere that move with velocities between 500 and 1000 m/s across the polar region. These clouds can disrupt electromagnetic signals between the ground and satellites, signals that are used for communication and navigation services in the arctic region. In order to predict when and where these disruptions occur, we must first understand how these plasma clouds are formed. It has been shown that channels of high plasma velocity occur in the same region where plasma clouds are created, but the connection between the two phenomena was unclear. We did a series of studies that show that the flow channels are indeed an important part of the plasma cloud formation process. Using years of data from GPS receiver stations and ionospheric radars we were able to show that the solar wind drives the formation process and that the dynamic high-velocity channels cut the continuous tongue of ionization into smaller pieces. With the help of these results forecast models for the formation of plasma clouds can now be developed.

Polar cap patches are islands of increased plasma density drifting across the polar cap. These patches are known to be a significant source of disturbances both for high-frequency radio communications and satellite navigation systems; they are therefore k ey elements in the understanding of space weather impacts on technological systems. Although it seems clear that the polar cap patch material originates from mid-latitude high-density plasma created by solar EUV radiation, their formation mechanism is sti ll poorly understood. In particular, it is unclear what impact localized flow shears and precipitation of particles have on the segmentation of the high-density reservoir into separate patches. During this three year research activity we plan to study in detail the influence of ionospheric meso-scale flow channels on the formation of polar cap patches by using a comprehensive set of data from radars, all-sky imagers, GPS receivers, and satellites which cover multiple spatial scales.