Study of the auroral ionosphere with artificially injected plasma: the BROR experiment data analysis.

On 23 March 2023, the Barium Radio and Optical Rocket (BROR) experiment was successfully carried out at the Esrange rocket range near Kiruna, Sweden. The BROR project was funded by the Swedish National Space Agency (project 2020-000106).

The BROR experiment aims to study small-scale processes and structures in the auroral ionosphere by means of an active modification of the ionosphere using multiple releases of barium combined with simultaneous ground-based optical and radio observations of the resulting plasma clouds.

The BROR rocket carried the 8 canisters with the 2 kg Ba+Sr+CuO thermite mixture which were ejected at various altitudes in the 130-250 km range.

All releases were successful and were observed from the ground.The artificial neutral and plasma clouds resulting from the releases were observed by the ground-based optical and radio instruments.

The key optical facility was ALIS_4D (Auroral Large Imaging System 4D), a multi-station, a spectroscopic optical imaging system with unprecedented capabilities that allows applying tomography-like methods for reconstructing the 3D-structure of atmospheric optical phenomena.

The optical measurements were complemented by the imagers operated by NIPR(National Institute of Polar Research), Japan, and by the IRF all-sky camera. For the radio measurements, we used the EISCAT UHF radar.

This project aims to investigate the structure and dynamics of the auroral ionosphere by analysing the huge amount of optical and radar data obtained during the BROR experiment.

Particular attention will be paid to (1) the study of dynamics and physical kinetics of the E and lower F ionosphere regions based on the observations of the two lowest releases at the 130 and 160 km altitudes, and (2) the study of the electric field structure and dynamics in the vicinity of the auroral arc retrieved from the observed dynamic of the barium ion clouds at the altitudes higher than 200 km.

The absolute calibration of the ALIS_4D images is necessary for the successful analysis of the optical data. Such calibrations using laboratory and bright star observations are a part of this project.