On the Creation, Depletion, and End of Life of Polar Cap Patches
Ionospheric convection patterns from the Super Dual Auroral Radar Network are used to determine the trajectories, transit times, and decay rates of three polar cap patches from their creation in the dayside polar cap ionosphere to their end of life on the nightside. The first two polar cap patches were created within 12 min of each other and traveled through the dayside convection throat, before entering the nightside auroral oval after 104 and 92 min, respectively. When the patches approached the nightside auroral oval, an intensification in the poleward auroral boundary occurred close to their exit point, followed by a decrease in the transit velocity. The last patch (patch 3) decayed completely within the polar cap and had a lifetime of only 78 min. After a change in drift direction, patch 3 had a radar backscatter power half‐life of 4.23 min, which reduced to 1.80 min after a stagnation, indicating a variable decay rate. 28 minutes after the change in direction, and 16 min after coming to a halt within the Clyde River radar field‐of‐view, patch 3 appeared to reach its end of life. We relate this rapid decay to increased frictional heating, which speeds up the recombination rate. Therefore, we suggest that the slowed patch motion within the polar cap convection pattern is a major factor in determining whether the patch survives as a recognizable density enhancement by the time the flux tubes comprising the initial patch cross into the nightside auroral oval.
Norges Forskningsråd. Grant Number: 223252/F50
A Consolidated Grant Proposal for Solar and Planetary Science at the University of Leicester, 2022 - 2025
Science and Technology Facilities CouncilFind out more...
A multi-instrument exploration of the cusp ionosphere
Natural Environment Research CouncilFind out more...
Research Council of Norway. Grant Number: 245683
NASA. Grant Number: NAS5-02099
NSF. Grant Number: AGS-1004736
Japan Society for Promotion of Science. Grant Numbers: 16H06286, 26302006, 21H04518, 22K21345
STFC. Grant Number: ST/W00089X/1
NERC. Grant Number: NE/V000748
Canadian Foundation for Innovation
New Brunswick Innovation Foundation
Canadian Space Agency. Grant Number: 21SUSTCHAI
US National Science Foundation. Grant Number: AGS-1952737
Author affiliationSchool of Physics & Astronomy, University of Leicester
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