2022 Fiscal Year Research-status Report
Investigating the conditions of ELF/VLF wave propagation from space to the ground.
| Project/Area Number |
22K14083
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| Research Institution | Nagoya University |
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Principal Investigator |
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| Project Period (FY) |
2022-04-01 – 2025-03-31
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| Keywords | VLF waves / conjugated events / bursty-patches / ionospheric exit point |
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| Outline of Annual Research Achievements |
We installed a VLF receiver in Oulujarvi, Finland (OUJ) located 450 km south of the existing receiver at Kannuslehto (KAN). KAN is 400 km west of the receiver at Lovozero (LOZ). We investigated characteristics of conjugated events between KAN and LOZ. A 1-month study of conjugated events between OUJ and KAN found 33 cases of one-to-one correspondence (same waves/source region). These cases give us an estimation of the latitudinal extent of VLF waves (450 km) and insight into VLF occurrence (~30% of total observations show one-to-one correspondence). Through polarization analysis, the investigation of the evolution of their ionospheric exit point is underway. We have also started long term plans for statistical analysis of OUJ and KAN data for conjugated events and VLF bursty-patches.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The main objective of installing the new VLF receiver at OUJ was achieved in October 2022. We have started analyzing the data for short term statistics (1 month) of conjugated VLF waves with KAN, and have set up a plan for long term statistics for both VLF conjugated events and bursty-patches. We have created a polarization analysis code and are currently validating it so we can continue with triangulation of the ionospheric exit point. While the installation of the antenna was delayed the analysis is going well. However, data analysis for statistics needs to be done by eye so this process is taking longer than expected.
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| Strategy for Future Research Activity |
Using 1-month conjugated event data we get preliminary details on latitudinal wave propagation. Once the polarization analysis has been validated, we will triangulate the location of ionospheric exit point and publish our findings. Depending on the advancement, we need to consider including ray tracing analysis or consider this as a separate topic.
We will then focus on long-term statistics for both conjugated VLF emissions (comparison with longitudinal extend) and for bursty-patches. Ideally, we require at least one year of data so that might delay the analysis slightly. We might then initially focus on the specific mode or propagation path for bursty-patches in case-by-case scenarios (comparing properties at OUJ and KAN) considering geomagnetic parameters and solar wind conditions.
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| Causes of Carryover |
Because of the pandemic and the low yen value, travel in FY2022 remained limited and very expensive. Moving the leftover money to the next fiscal year will allow us to secure a visit to Finland to check on the instrument in FY2023 (planned for July 2023) and visit ray tracing experts + participate in an international conference (Dec 2023). We also expect to cover paper publication expenses and any material needs for the receiver or data.
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[Presentation] Propagation of VLF conjugated events at sub-auroral latitudes from multi-point observations in Fennoscandia and the inner magnetosphere.2022
Author(s)
Martinez-Calderon, C., Y. Katoh, O. Santolik, M. Hanzelka, J. Manninen, Y. Miyoshi, Y. Kasahara, F. Tsuchiya, S. Matsuda, A. Kumamoto, S. Nakamura, M. Kitahara, I. Shinohara and K. Shiokawa
Organizer
AGU Fall meeting 2022, Chicago, USA
Int'l Joint Research
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