Investigating the conditions of ELF/VLF wave propagation from space to the ground.
| Project/Area Number |
22K14083
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| Research Category |
Grant-in-Aid for Early-Career Scientists
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| Allocation Type | Multi-year Fund |
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| Review Section |
Basic Section 17010:Space and planetary sciences-related
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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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| Project Status |
Granted (Fiscal Year 2022)
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| Budget Amount *help |
¥4,550,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥1,050,000)
Fiscal Year 2024: ¥1,560,000 (Direct Cost: ¥1,200,000、Indirect Cost: ¥360,000)
Fiscal Year 2023: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2022: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
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| Keywords | VLF waves / conjugated events / bursty-patches / ionospheric exit point / vlf waves / multipoint observations / magnetosphere / geospace / ionosphere |
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| Outline of Research at the Start |
Extremely Low and Very Low Frequency emissions at frequencies of 0.3-30 kHz interact with energetic electrons causing their acceleration or loss, playing an important role in radiation belt dynamics. We have little understanding on how these waves travel from the magnetosphere (alt: 1,000-60,000 km) to the ground. Using VLF ground receivers we will determine the likely position where waves exit the ionosphere. Using simultaneous detection of waves on satellites and ground we will study what affects wave propagation and discuss their effect on the loss of hazardous radiation belt electrons.
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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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Report
(1 results)
Research Products
(4 results)
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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
Related Report
Int'l Joint Research
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