[PEM19-02] Magnetic field dipolarization and low-energy O+ ion flux variations in the inner magnetosphere observed by Arase
Keywords:Inner magnetosphere, Substorm, Ion composition
In the present study, we examine the low-energy O+ ion flux variations observed by the Arase satellite in the inner magnetosphere. Magnetic field dipolarization is selected from the magnetic field data obtained by the fluxgate magnetometer (MGF) [Matsuoka et al., 2018] in the period of April 1–October 31, 2017 and July 1, 2018–January 31, 2019, and we find 243 events. Data from the low-energy particle experiments–ion mass analyzer (LEPi) [Asamura et al., 2018] are examined to check if the selected dipolarization events are accompanied by low-energy O+ ion flux variations in the direction along the local magnetic field. There are some events of the low-energy O+ ion flux enhancement, which (1) starts ~10 minutes after the dipolarization onset, (2) has energy-dispersed signatures with decreasing energy down to a few 10s of eV, (3) appears down to L ~ 4 with the lowest energy (10 eV), (4) can be observed in both storm and non-storm periods, and (5) has a field-aligned distribution (α ~ 0° below the equator and α ~ 180° above the equator). In the presentation, we will show the analysis results in more detail and discuss their contribution to the O+ content of the inner magnetospheric plasma.