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A possible cause for the October effect in the D-region

Wendt, Vivien and Schneider, Helen and Verronen, Pekka T. and Banyś (geb. Wenzel), Daniela and Hansen, Marc and Clilverd, Mark and Raita, Tero (2024) A possible cause for the October effect in the D-region. DPG Frühjahrstagung 2024 Greifswald, 2024-02-26 - 2024-02-29, Greifswald.

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Abstract

Radar waves with very low frequency (VLF) are reflected in the D-region, the lower edge of the ionosphere. The D-region (60 - 90km) is influenced by the solar zenith angle and space weather from above and by the mesosphere's dynamic and chemical processes. During October there is a sharp decrease of the daytime VLF amplitude between transmitter and receiver combinations whose great circle paths lie in polar latitudes. Until now we do not know what causes the October effect. Space weather phenomena can be ruled out as a cause since their time scales are too short or too long. The solar zenith angle can also be ruled out as a similar behavior is not observed in spring. Thus, there is an assumption that dynamical processes in the mesosphere play a major role. Previous studies showed that a strong warming occurs in the lower mesosphere shortly before the October effect is observed. While the characteristics of this warming help us to explain why the October effect occurs during daytime only, the warming alone cannot explain the sharp decrease in the VLF daytime amplitude. We suspect and confirm that the water vapor in the lower mesosphere, having similar characteristics as the warming and the VLF amplitude decrease, plays a crucial role in the formation mechanism of the October effect.

Item URL in elib:https://elib.dlr.de/203074/
Document Type:Conference or Workshop Item (Speech)
Title:A possible cause for the October effect in the D-region
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Wendt, VivienUNSPECIFIEDhttps://orcid.org/0000-0003-1806-4507UNSPECIFIED
Schneider, HelenUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Verronen, Pekka T.University of Oulo, Sodankylä, FinlandUNSPECIFIEDUNSPECIFIED
Banyś (geb. Wenzel), DanielaUNSPECIFIEDhttps://orcid.org/0000-0001-6623-6612UNSPECIFIED
Hansen, MarcUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Clilverd, MarkBritish Antarctic Survey, High Cross, Cambridge, UKhttps://orcid.org/0000-0002-7388-1529UNSPECIFIED
Raita, TeroSodankylä Geophysical ObservatoryUNSPECIFIEDUNSPECIFIED
Date:26 February 2024
Refereed publication:No
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Status:Published
Keywords:October Effect, VLF observations, D-region, atmosphere coupling
Event Title:DPG Frühjahrstagung 2024 Greifswald
Event Location:Greifswald
Event Type:national Conference
Event Start Date:26 February 2024
Event End Date:29 February 2024
Organizer:Deutsche Physikalische Gesellschaft
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Solar-Terrestrial coupling processes
Location: Neustrelitz
Institutes and Institutions:Institute for Solar-Terrestrial Physics > Solar-Terrestrial Coupling Processes
Deposited By: Wendt, Dr. Vivien
Deposited On:05 Apr 2024 21:41
Last Modified:24 Apr 2024 21:03

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