25 Apr 2023
 | 25 Apr 2023
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Ground-based noontime D-region electron density climatology over northern Norway

Toralf Renkwitz, Mani Sivakandan, Juliana Jaen, and Werner Singer

Abstract. The bottom part of the earth’s ionosphere is the so-called D-region, which is typically less intense than the upper regions. Despite the comparably lower electron number density, the ionization state of the D-region has a significant influence on signal absorption for propagating lower to medium radio frequencies. We present local noon climatologies of electron number density in the middle atmosphere at high latitudes as observed by an active radar experiment. The radar measurements cover nine years from the solar maximum of cycle 24 to the beginning of cycle 25. Reliable electron densities are derived by employing signal processing, applying interferometry methods, and the Faraday International Reference Ionosphere (FIRI) model. For all years a consistent spring-autumn asymmetry of the electron number density pattern as well as a sharp decrease at the beginning of October was found. These findings are consistent with VLF studies showing equivalent signatures for nearby propagation paths. It has been suggested that the meridional circulation associated with downwelling in winter could cause enhanced electron densities through NO transport. However, this mechanism lacks to explain the reduction in electron density in early October.

Toralf Renkwitz et al.

Status: open (until 18 Jun 2023)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-815', Martin Friedrich, 08 May 2023 reply
    • AC1: 'Reply on RC1', Toralf Renkwitz, 25 May 2023 reply

Toralf Renkwitz et al.

Toralf Renkwitz et al.


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Short summary
The manuscript focuses on remote sensing of the lowermost part of the Ionosphere (D-region) between about 50 to 90 km altitude, which overlaps widely with the mesosphere. We present a climatology of electron number density over northern Norway, covering solar maximum and minimum conditions (2014–2022). Detecting energetic particle precipitation events we derived the quiet profile climatology. We also found a spring-fall asymmetry while a symmetric solar zenith angle dependence is expected.