Magnetospheric Multiscale observations of energetic oxygen ions at the duskside magnetopause during intense substorms

Zeng, Chen; Duan, Suping; Wang, Chi; Dai, Lei; Fuselier, Stephen; Burch, James; Torbert, Roy; Giles, Barbara; Russell, Christopher

Energetic oxygen ions (1–40 keV) observed by the Magnetospheric Multiscale (MMS) satellites at the duskside magnetopause boundary layer during phase 1 are investigated. There are 57 duskside magnetopause crossing events identified during intense substorms (inline-formulaAE>500 nT). These 57 events of energetic inline-formulaO+ at the duskside magnetopause include 26 events during the expansion phase and 31 events during the recovery phase of intense substorms. It is found that the inline-formulaO+ density in the duskside magnetopause boundary layer during the recovery phase (0.081 cminline-formula−3) is larger than that during the expansion phase (0.069 cminline-formula−3). The 26 events of energetic inline-formulaO+ ions at the duskside magnetopause during intense substorm expansion phase are all under the southward interplanetary magnetic field (IMF). There are only seven events under northward IMF, and they all occurred during the intense substorm recovery phase. The density of energetic inline-formulaO+ at the duskside magnetopause ranges from 0.007 to 0.599 cminline-formula−3. The maximum density of inline-formulaO+ occurred during the intense substorm recovery phase and under southward IMF. When the IMF is southward, the inline-formulaO+ density shows an exponential increase with the IMF inline-formulaBz absolute value. Meanwhile, the inline-formula M12inlinescrollmathml chem normal O + / normal H + 36pt14ptsvg-formulamathimg381c4c0cf06e56af75023ee66d0cebd1 angeo-38-123-2020-ie00001.svg36pt14ptangeo-38-123-2020-ie00001.png density ratio shows an exponential growth with the IMF inline-formulaBy. These results agree with previous studies in the near-Earth magnetosphere during intense substorm. It is suggested that inline-formulaO+ abundance in the duskside magnetopause boundary layer has a close relation to inline-formulaO+ variations in the near-Earth magnetosphere during intense substorms.

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Zeng, Chen / Duan, Suping / Wang, Chi / et al: Magnetospheric Multiscale observations of energetic oxygen ions at the duskside magnetopause during intense substorms. 2020. Copernicus Publications.

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