Geomagnetic control of polar mesosphere summer echoes.

• Main Authors: Bremer, J., Hansen, T.L., Hoffmann, P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: European Geophysical Society 2000
• Subjects: ionosphere; auroral ionosphere; Magnetospheric physics; energetic particles; precipitating; radio science; remote sensing; VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Elektromagnetisme; akustikk; optikk: 434; VDP::Matematikk og Naturvitenskap: 400::Fysikk: 430::Rom- og plasmafysikk: 437; Alomar; Ivalo; Andenes
• Online Access: https://hdl.handle.net/10037/558

Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N, 16.0°E) from 1994 until 1997 polar mesosphere summer echoes (PMSE) have been investigated in dependence on geomagnetic K indices derived at the Auroral Observa- tory Tromsù (69.66°N, 18.94°E). During night-time and morning hours a significant correlation between the signal-to-noise ratio (SNR) of the radar results and the geomagnetic K indices could be detected with a maxi- mum correlation near midnight. The correlation be- comes markedly smaller in the afternoon and early evening hours with a minimum near 17 UT. This diurnal variation is in reasonable agreement with riometer absorption at Ivalo (68.55°N, 27.28°E) and can be explained by the diurnal variation of ionization due to precipitating high energetic particles. Therefore, a part of the diurnal PMSE variation is caused by this particle precipitation. The variability of the solar EUV varia- tion, however, has no significant influence on the PMSE during the observation period.