Location
Yosemite National Park
Start Date
2-10-2014 5:10 PM
End Date
2-10-2014 5:25 PM
Description
We investigated electron density enhancements at ~9000 km altitude and ion flows in the polar magnetosphere during geomagnetic storms at solar maximum using data obtained by the Akebono and Polar satellites, to understand supply mechanisms of high density plasma from the ionosphere to the regions of enhanced electron densities in the polar magnetosphere, and significance of the high density ions in O+ ion supply toward the magnetosphere. Event studies indicated that the electron density enhancements (exceeded 1000 /cm3 (100 /cm3) at ~7000 (~9000) km altitude, which were higher than the quiet time level with a factor of >10 (>4)) tended to persist through the main phase and around the minimum of the SYM-H index of geomagnetic storms. In the region of enhanced electron densities in the dayside polar cap, ions were dominated by O+ ions with upward velocities of 4–10 km/s (streaming energies of 1.3–8.4 eV). Owing to large spatial scale, long duration, and high densities, the total amount of very-low-energy O+ ions that flow through the region would be large (~2 × 1026 /s based on a rough estimation). Spatial distributions of parallel velocities in noon-midnight direction and temperatures of ions indicate that the very-low-energy component of the cleft ion fountain that is dominated by O+ ions drifted deep into the polar cap, and increased the density in the polar cap. Although the energy of O+ ions were low, the energy is sufficient to reach the near-Earth plasmasheet (GSM X >~−20 RE) on the basis of trajectory calculations of very-low-energy O+ ions under strong convection. Thus, these very-low-energy O+ ions may affect the global dynamics of the magnetosphere (e.g., cross polar cap potential) and triggering of storm-time substorms (reconnection), and would play a major role in the development of geomagnetic storms (ring current formation) at solar maximum.
Very-low-energy O+ ion outflows during geomagnetic storms
Yosemite National Park
We investigated electron density enhancements at ~9000 km altitude and ion flows in the polar magnetosphere during geomagnetic storms at solar maximum using data obtained by the Akebono and Polar satellites, to understand supply mechanisms of high density plasma from the ionosphere to the regions of enhanced electron densities in the polar magnetosphere, and significance of the high density ions in O+ ion supply toward the magnetosphere. Event studies indicated that the electron density enhancements (exceeded 1000 /cm3 (100 /cm3) at ~7000 (~9000) km altitude, which were higher than the quiet time level with a factor of >10 (>4)) tended to persist through the main phase and around the minimum of the SYM-H index of geomagnetic storms. In the region of enhanced electron densities in the dayside polar cap, ions were dominated by O+ ions with upward velocities of 4–10 km/s (streaming energies of 1.3–8.4 eV). Owing to large spatial scale, long duration, and high densities, the total amount of very-low-energy O+ ions that flow through the region would be large (~2 × 1026 /s based on a rough estimation). Spatial distributions of parallel velocities in noon-midnight direction and temperatures of ions indicate that the very-low-energy component of the cleft ion fountain that is dominated by O+ ions drifted deep into the polar cap, and increased the density in the polar cap. Although the energy of O+ ions were low, the energy is sufficient to reach the near-Earth plasmasheet (GSM X >~−20 RE) on the basis of trajectory calculations of very-low-energy O+ ions under strong convection. Thus, these very-low-energy O+ ions may affect the global dynamics of the magnetosphere (e.g., cross polar cap potential) and triggering of storm-time substorms (reconnection), and would play a major role in the development of geomagnetic storms (ring current formation) at solar maximum.