Polar Mesospheric Summer Echo Characteristics in Magnetic Local Time and Height Profiles
We conducted a statistical study of polar mesospheric summer echoes (PMSEs) in relation to magnetic local time (MLT), considering the geomagnetic conditions using the K-index (or K). Additionally, we performed a case study to examine the velocity profile, specifically for high velocities (≥ ~100 m...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
The Korean Space Science Society
2023-09-01
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| Series: | Journal of Astronomy and Space Sciences |
| Subjects: | |
| Online Access: | https://www.janss.kr/archive/view_article?pid=jass-40-3-101 |
| Summary: | We conducted a statistical study of polar mesospheric summer echoes (PMSEs) in relation to magnetic local time (MLT),
considering the geomagnetic conditions using the K-index (or K). Additionally, we performed a case study to examine the
velocity profile, specifically for high velocities (≥ ~100 m/s) varying with high temporal resolution at high K-index values. This
study utilized the PMSE data obtained from the mesosphere–stratosphere–troposphere radar located in Esrange, Sweden
(63.7°N, 21°E). The change in K-index in terms of MLT was high (K ≥ 4) from 23 to 04 MLT, estimated for the time PMSE was
present. During the near-midnight period (0–4 MLT), both PMSE occurrence and signal-to-noise ratio (SNR) displayed an
asymmetric structure with upper curves for K ≥ 3 and lower curves for K < 3. Furthermore, the occurrence of high velocities
peaked at 3–4 MLT for K ≥ 3. From case studies focusing on the 0–3 MLT period, we observed persistent eastward-biased high
velocities (≥ 200 m/s) prevailing for ~18 min. These high velocities were accompanied with the systematic motion of profiles
at 85–88 km, including large shear formation. Importantly, the rapid variations observed in velocity could not be attributed to
neutral wind effects. The present findings suggest a strong substorm influence on PMSE, especially in the midnight and early
dawn sectors. The large zonal drift observed in PMSE were potentially energized by local electromagnetic fields or the global
convection field induced by the electron precipitation during substorms. |
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| ISSN: | 2093-5587 2093-1409 |