Ying Zou, Brian M. Walsh, Yuxi Chen, Hongyang Zhou, Savvas Raptis
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Some fluctuations are correlated with the IMF strength but not all. The level of fluctuations in the IMF is positively correlated with <0.01 Hz fluctuations in the magnetosheath. A higher Mach number is associated with a larger fraction of compressional versus transverse fluctuations in the magnetosheath. Quantitatively, the correlation between magnetosheath fluctuations and individual solar wind parameters is weak, correlation magnitude being <0.5. However, by performing a multiple linear regression fit of the solar wind parameters to magnetosheath fluctuations, a reasonably good prediction can be achieved with correlation magnitude in the range of 0.5–0.7, except for the parallel magnetosheath fluctuations of 0.01–0.1 Hz. Our results are overall consistent with earlier studies, but our quantitative approach further permits forecast of how much the IMF changes inside the magnetosheath which is beneficial for scientific understanding and space weather forecasts.</p>","PeriodicalId":15894,"journal":{"name":"Journal of Geophysical Research: Space Physics","volume":"130 6","pages":""},"PeriodicalIF":2.9000,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Control of Solar Wind on Magnetic Field Fluctuations in the Subsolar Magnetosheath\",\"authors\":\"Ying Zou, Brian M. Walsh, Yuxi Chen, Hongyang Zhou, Savvas Raptis\",\"doi\":\"10.1029/2025JA033856\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>The magnetosheath modifies the solar wind and IMF before they reach Earth's magnetosphere, and hence plays a crucial role in regulating the solar wind-magnetosphere interaction. Although the steady component of the magnetosheath magnetic field has been reasonably well reproduced, the fluctuating component has been less accounted for despite its significant amplitude. This paper empirically determines the mean characteristics of the ultra-low-frequency magnetic field fluctuations, and constructs a functional form using solar wind parameters. We use 15 years of THEMIS A data for the magnetosheath, and OMNI for the upstream solar wind conditions. Qualitatively, fluctuations are negatively correlated with the IMF cone angle, and positively with the solar wind speed and dynamic pressure. Some fluctuations are correlated with the IMF strength but not all. The level of fluctuations in the IMF is positively correlated with <0.01 Hz fluctuations in the magnetosheath. A higher Mach number is associated with a larger fraction of compressional versus transverse fluctuations in the magnetosheath. Quantitatively, the correlation between magnetosheath fluctuations and individual solar wind parameters is weak, correlation magnitude being <0.5. However, by performing a multiple linear regression fit of the solar wind parameters to magnetosheath fluctuations, a reasonably good prediction can be achieved with correlation magnitude in the range of 0.5–0.7, except for the parallel magnetosheath fluctuations of 0.01–0.1 Hz. Our results are overall consistent with earlier studies, but our quantitative approach further permits forecast of how much the IMF changes inside the magnetosheath which is beneficial for scientific understanding and space weather forecasts.</p>\",\"PeriodicalId\":15894,\"journal\":{\"name\":\"Journal of Geophysical Research: Space Physics\",\"volume\":\"130 6\",\"pages\":\"\"},\"PeriodicalIF\":2.9000,\"publicationDate\":\"2025-06-11\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Geophysical Research: Space Physics\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://onlinelibrary.wiley.com/doi/10.1029/2025JA033856\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"ASTRONOMY & ASTROPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Geophysical Research: Space Physics","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1029/2025JA033856","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ASTRONOMY & ASTROPHYSICS","Score":null,"Total":0}
引用次数: 0
摘要
磁鞘在太阳风和IMF到达地球磁层之前就对其进行了修饰,因此在调节太阳风-磁层相互作用中起着至关重要的作用。虽然磁鞘磁场的稳定分量已经得到了相当好的再现,但波动分量却很少得到解释,尽管它的振幅很大。本文根据经验确定了超低频磁场波动的平均特征,并利用太阳风参数构造了函数形式。我们使用THEMIS A 15年的磁鞘数据,OMNI用于上游太阳风条件。定性上,波动与IMF锥角呈负相关,与太阳风速度和动压呈正相关。一些波动与IMF的实力有关,但并非全部。国际货币基金组织的波动水平与磁鞘的0.01 Hz波动呈正相关。马赫数越高,磁鞘中纵波波动和横波波动的比例越大。定量上,磁鞘波动与单个太阳风参数相关性较弱,相关量级为<;0.5。然而,通过对太阳风参数与磁鞘波动进行多元线性回归拟合,除磁鞘平行波动为0.01 ~ 0.1 Hz外,相关量级在0.5 ~ 0.7范围内均可获得较好的预测结果。我们的结果总体上与早期的研究一致,但我们的定量方法进一步允许预测磁鞘内IMF的变化程度,这有利于科学理解和空间天气预报。
Control of Solar Wind on Magnetic Field Fluctuations in the Subsolar Magnetosheath
The magnetosheath modifies the solar wind and IMF before they reach Earth's magnetosphere, and hence plays a crucial role in regulating the solar wind-magnetosphere interaction. Although the steady component of the magnetosheath magnetic field has been reasonably well reproduced, the fluctuating component has been less accounted for despite its significant amplitude. This paper empirically determines the mean characteristics of the ultra-low-frequency magnetic field fluctuations, and constructs a functional form using solar wind parameters. We use 15 years of THEMIS A data for the magnetosheath, and OMNI for the upstream solar wind conditions. Qualitatively, fluctuations are negatively correlated with the IMF cone angle, and positively with the solar wind speed and dynamic pressure. Some fluctuations are correlated with the IMF strength but not all. The level of fluctuations in the IMF is positively correlated with <0.01 Hz fluctuations in the magnetosheath. A higher Mach number is associated with a larger fraction of compressional versus transverse fluctuations in the magnetosheath. Quantitatively, the correlation between magnetosheath fluctuations and individual solar wind parameters is weak, correlation magnitude being <0.5. However, by performing a multiple linear regression fit of the solar wind parameters to magnetosheath fluctuations, a reasonably good prediction can be achieved with correlation magnitude in the range of 0.5–0.7, except for the parallel magnetosheath fluctuations of 0.01–0.1 Hz. Our results are overall consistent with earlier studies, but our quantitative approach further permits forecast of how much the IMF changes inside the magnetosheath which is beneficial for scientific understanding and space weather forecasts.