The Polarity of IMF By Strongly Modulates Particle Precipitation During High-Speed Streams
Laitinen, J.; Holappa, L.; Vanhamäki, H. (2024-09-02)
John Wiley & Sons
02.09.2024
Laitinen, J., Holappa, L., & Vanhamäki, H. (2024). The polarity of IMF By strongly modulates particle precipitation during high-speed streams. Geophysical Research Letters, 51, e2024GL110877. https://doi.org/10.1029/2024GL110877.
https://creativecommons.org/licenses/by/4.0/
© 2024. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
https://creativecommons.org/licenses/by/4.0/
© 2024. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
https://creativecommons.org/licenses/by/4.0/
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:oulu-202409095747
https://urn.fi/URN:NBN:fi:oulu-202409095747
Tiivistelmä
Abstract
Recent studies have suggested that the interplanetary magnetic field (IMF) \({B}_{y}\) component modulates particle precipitation during solstices, or periods of high dipole tilt \({\Psi }\). So far this explicit IMF \({B}_{y}\)-effect has only been shown in statistical studies. Here we analyzed a sequence of high-speed stream (HSS) driven events of auroral (\({< } 30\) keV) and medium energy (\({> } 30\) keV and \({> } 100\) keV) particle precipitation. We show that when HSSs are comparable in terms of IMF and solar wind parameters, they can lead to systematically stronger particle precipitation in individual events when the signs of \({B}_{y}\) and \({\Psi }\) are opposite. We also perform a superposed epoch analysis of 485 HSSs giving further evidence that the \({B}_{y}\)-effect is especially significant during HSSs. This is likely due to the persistent IMF \({B}_{y}\) polarity during HSSs. We show evidence that the \({B}_{y}\) dependence in particle precipitation is caused by a similar \({B}_{y}\) dependence in substorm occurrence.
Recent studies have suggested that the interplanetary magnetic field (IMF) \({B}_{y}\) component modulates particle precipitation during solstices, or periods of high dipole tilt \({\Psi }\). So far this explicit IMF \({B}_{y}\)-effect has only been shown in statistical studies. Here we analyzed a sequence of high-speed stream (HSS) driven events of auroral (\({< } 30\) keV) and medium energy (\({> } 30\) keV and \({> } 100\) keV) particle precipitation. We show that when HSSs are comparable in terms of IMF and solar wind parameters, they can lead to systematically stronger particle precipitation in individual events when the signs of \({B}_{y}\) and \({\Psi }\) are opposite. We also perform a superposed epoch analysis of 485 HSSs giving further evidence that the \({B}_{y}\)-effect is especially significant during HSSs. This is likely due to the persistent IMF \({B}_{y}\) polarity during HSSs. We show evidence that the \({B}_{y}\) dependence in particle precipitation is caused by a similar \({B}_{y}\) dependence in substorm occurrence.
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