GLOBAL DIAGNOSTICS OF IONOSPHERIC ABSORPTION DURING X-RAY SOLAR FLARES BASED ON 8- TO 20-MHZ NOISE MEASURED BY OVER-THE-HORIZON RADARS ArticleBerngardt O.I., Ruohoniemi J.M., St-Maurice J.P., Marchaudon A., Kosch M.J., Yukimatu A.S., Nishitani N., Shepherd S.G., Marcucci M.F., Hu H., Nagatsuma T., Lester M.Space Weather. Vol. 17. 2019. P.. 907-924