Explicit IMF B -Dependence of Energetic Protons and the Ring Current

Area of Science:

• Space Physics
• Magnetospheric Physics
• Solar-Terrestrial Physics

Background:

• The solar wind-magnetosphere interaction is primarily driven by the southward interplanetary magnetic field (IMF) B_z component.
• The dawn-dusk (IMF) B_y component's role is significant but typically considered sign-independent.
• Previous studies have not fully explored the explicit dependence of magnetospheric phenomena on the sign of IMF B_y.

Purpose of the Study:

• To investigate and demonstrate a seasonally varying, explicit dependence of the ring current and Dst index on the IMF B_y component.
• To analyze how the sign of IMF B_y affects energetic particle flux and ring current development.

Main Methods:

• Utilizing satellite observations of the magnetosphere.
• Employing a global magnetohydrodynamic (MHD) model coupled with a ring current model.
• Analyzing data for seasonal variations in response to IMF B_y.

Main Results:

• A clear, seasonally dependent IMF B_y effect on the ring current and Dst index was identified.
• For a fixed solar wind input, the flux of energetic magnetospheric protons and the ring current growth rate are greater for B_y < 0 than B_y > 0 in Northern Hemisphere summer.
• Conversely, these values are greater for B_y > 0 than B_y < 0 in Northern Hemisphere winter.

Conclusions:

• The sign of the IMF B_y component has an explicit, seasonally varying impact on the ring current and Dst index.
• This explicit B_y effect suggests modulation of magnetospheric convection and plasma transport in the inner magnetosphere.
• Further research is needed to fully understand the underlying physical mechanisms driving this observed phenomenon.