Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves
Abstract Collisionless shocks can be nonstationary with periodic reformation shown in many simulation results, but direct observations are still tenuous and difficult to conclusively interpret. In this study, using Magnetospheric Multiscale (MMS) observations, we report direct observational evidence...
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| Format: | Article |
| Language: | English |
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Wiley
2021-01-01
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| Series: | Geophysical Research Letters |
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| Online Access: | https://doi.org/10.1029/2020GL091184 |
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| author | Terry Z. Liu Yufei Hao Lynn B. Wilson III Drew L. Turner Hui Zhang |
| author_facet | Terry Z. Liu Yufei Hao Lynn B. Wilson III Drew L. Turner Hui Zhang |
| author_sort | Terry Z. Liu |
| collection | DOAJ |
| description | Abstract Collisionless shocks can be nonstationary with periodic reformation shown in many simulation results, but direct observations are still tenuous and difficult to conclusively interpret. In this study, using Magnetospheric Multiscale (MMS) observations, we report direct observational evidence of Earth's oblique bow shock reformation driven by the foreshock Ultralow‐Frequency (ULF) waves. When the four MMS spacecraft were in a string‐of‐pearls formation roughly along the bow shock normal, they observed that when each period of foreshock ULF waves encountered the bow shock, a new shock ramp formed. Meanwhile, in the magnetosheath, the old bow shock's remnants were observed periodically convecting downstream. We propose that the reformation mechanism of the oblique bow shock is the variation of the upstream conditions by the periodic ULF waves as they encounter the bow shock. We also examine the nature of reflected ions during the reformation process. |
| format | Article |
| id | doaj-art-397b2e3bb0704478b4e93abffa13fd50 |
| institution | DOAJ |
| issn | 0094-8276 1944-8007 |
| language | English |
| publishDate | 2021-01-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geophysical Research Letters |
| spelling | doaj-art-397b2e3bb0704478b4e93abffa13fd502025-08-20T03:04:21ZengWileyGeophysical Research Letters0094-82761944-80072021-01-01482n/an/a10.1029/2020GL091184Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency WavesTerry Z. Liu0Yufei Hao1Lynn B. Wilson III2Drew L. Turner3Hui Zhang4Cooperative Programs for the Advancement of Earth System Science University Corporation for Atmospheric Research Boulder CO USAKey Laboratory of Planetary Sciences Purple Mountain Observatory Chinese Academy of Sciences Nanjing ChinaHeliophysics Science Division NASA Goddard Space Flight Center Greenbelt MD USAJohns Hopkins University Applied Physics Laboratory Johns Hopkins University Laurel MD USAGeophysical Institute University of Alaska Fairbanks AK USAAbstract Collisionless shocks can be nonstationary with periodic reformation shown in many simulation results, but direct observations are still tenuous and difficult to conclusively interpret. In this study, using Magnetospheric Multiscale (MMS) observations, we report direct observational evidence of Earth's oblique bow shock reformation driven by the foreshock Ultralow‐Frequency (ULF) waves. When the four MMS spacecraft were in a string‐of‐pearls formation roughly along the bow shock normal, they observed that when each period of foreshock ULF waves encountered the bow shock, a new shock ramp formed. Meanwhile, in the magnetosheath, the old bow shock's remnants were observed periodically convecting downstream. We propose that the reformation mechanism of the oblique bow shock is the variation of the upstream conditions by the periodic ULF waves as they encounter the bow shock. We also examine the nature of reflected ions during the reformation process.https://doi.org/10.1029/2020GL091184foreshock ULF wavesshockshock reformation |
| spellingShingle | Terry Z. Liu Yufei Hao Lynn B. Wilson III Drew L. Turner Hui Zhang Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves Geophysical Research Letters foreshock ULF waves shock shock reformation |
| title | Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves |
| title_full | Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves |
| title_fullStr | Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves |
| title_full_unstemmed | Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves |
| title_short | Magnetospheric Multiscale Observations of Earth's Oblique Bow Shock Reformation by Foreshock Ultralow‐Frequency Waves |
| title_sort | magnetospheric multiscale observations of earth s oblique bow shock reformation by foreshock ultralow frequency waves |
| topic | foreshock ULF waves shock shock reformation |
| url | https://doi.org/10.1029/2020GL091184 |
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