Preprints
https://doi.org/10.5194/angeo-2022-16
https://doi.org/10.5194/angeo-2022-16
 
18 May 2022
18 May 2022
Status: this preprint is currently under review for the journal ANGEO.

Modulation of Polar Mesospheric Summer Echoes (PMSE) during HF Heating

Tinna Gunnarsdottir1, Arne Poggenpohl1,2, Ingrid Mann1, Alireza Mahmoudian3, Peter Dalin4, Ingemar Haeggstroem5, and Michael Rietveld6 Tinna Gunnarsdottir et al.
  • 1Department of Physics and Technology, UiT Arctic University of Norway, Tromsø, Norway
  • 2Physics Faculty, TU Dortmund University, Germany
  • 3Institude of Geophysics, University of Tehran, Iran
  • 4Swedish Institute of Space Physics, IRF, Kiruna, Sweden
  • 5EISCAT Scientific Association, Kiruna, Sweden
  • 6EISCAT Scientific Association, Ramfjord, Norway

Abstract. The formation of Polar Mesospheric Summer Echoes (PMSE) is linked to the presence of charged dust/ice particles in the mesosphere and the PMSE modulation is a possible way to observe the effect of dust charging. We investigate the modulation of PMSE by HF radio waves based on measurements carried out with the EISCAT Heating facility and the EISCAT VHF radar in August 2018 and August 2020 toward the end of the PMSE season. The measurements were made during the night with reduced solar illumination. The EISCAT Heating was operated in subsequent 48s on and 168s off intervals. In our observations, the PMSE modulation by the HF heating disappears during ionospheric conditions of energetic particle precipitation. We observe more than half of the cycles being influenced by the heating with a reduced PMSE power when the heater is on and a similar amount of cycles showing an increase in power when the heater is turned off. In less than half of the observed cycles we see an overshoot and it seems to be largely influenced by the overall PMSE power; with smaller or nonexistent overshoot when the PMSE power is high. We observe instances of very large overshoots, where background PMSE power seems to be reduced. During periods when we observe modulation, they often vary strongly from one cycle to the next; they are highly variable on spatial scales smaller km and time scales of minutes that are shorter than the scales assumed for the variation of dust parameters. Averaged curves over several heating cycles are similar to the overshoot curves predicted by theory and observed previously. Some individual curves however, show a stronger overshoot than observed in previous studies. A possible explanation for this difference can lie in the dust charging conditions that are different during the night or other conditions might be at play. We observe two possible instances of sporadic E-layers that are influenced by heating but do not show overshoots, as is to be expected.

Tinna Gunnarsdottir et al.

Status: open (until 21 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on angeo-2022-16', Anonymous Referee #1, 20 Jun 2022 reply
  • RC2: 'Comment on angeo-2022-16', Stephan C. Buchert, 21 Jun 2022 reply

Tinna Gunnarsdottir et al.

Tinna Gunnarsdottir et al.

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Short summary
Temperatures at 85 km around Earths poles in the summer can be so cold that small ice particles form. These particles can become charged and combined with turbulence at these altitudes they can influence the many electrons present. This can cause large radar echoes called Polar Mesospheric Summer Echoes. We use radio waves to heat these echoes on and off when the sun is close or below the horizon. This allows us to gain some insight into these ice particles and how the sun influences the echoes.