The Evolution of a Polar Cap Patch Into a Blob in the Nightside Ionosphere: Direct Observations of Multiple Blob Formation Mechanisms Acting Simultaneously on the Same Plasma
Year: 2026
Type: article
Abstract: A polar cap patch was observed to exit the polar cap to become a blob as it entered the auroral oval on the nightside of the Earth under moderately quiet geomagnetic conditions (=3-). Auroral particle precipitation led to an increase in the electron density of the blob. Blobs can be formed by multiple formation mechanisms, including transportation effects and auroral precipitation. This blob exhibits characteristics which fit within the definitions of both boundary and auroral blobs. This study therefore presents direct observations of multiple blob formation mechanisms acting simultaneously on the same plasma. These observations were made using the European Incoherent SCATter (EISCAT) radars. The polar cap patch was first observed in the EISCAT Svalbard Radar (ESR) and is later observed as a blob by the EISCAT VHF and UHF radars as the plasma moves antisunward from the polar cap and into the auroral oval. The Super Dual Auroral Radar Network (SuperDARN) radars showed that the plasma was moving antisunward and data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) provided support for the location of the auroral boundary. In addition, Global Navigation Satellite System (GNSS) receivers monitored the associated scintillation effects that were associated with large-scale structures. Overall, very low scintillation was observed suggesting that small-scale structures did not develop significantly during this period.
DOI: 10.1029/2025ja034402
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,070
Funders: National Science Foundation, Alberta Agricultural Research Institute, Florida Institute of Technology, UK Research and Innovation, Met Office, Sveriges Geologiska Undersökning, Universitetet i Oslo, Università degli Studi dell'Aquila, National Institute of Polar Research, Goddard Space Flight Center, Engineering and Physical Sciences Research Council, Natural Environment Research Council, Science and Technology Facilities Council, Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ, Office of Naval Research, British Antarctic Survey, HORIZON EUROPE European Research Council
Awards: Unveiling the timescales and intensities of solar-terrestrial interactions using novel datasets and techniques, G4153498110, EISCAT_3D: Fine-scale structuring, scintillation, and electrodynamics (FINESSE), EISCAT_3D: Fine-scale structuring, scintillation, and electrodynamics (FINESSE), G5308898452, DRivers and Impacts of Ionospheric Variability with EISCAT-3D (DRIIVE)
OpenAlex ID: W7134164946