Substorm Signatures in the Dayside Magnetosphere

Abstract. We investigate variations in the position of the magnetopause in response to the interplanetary magnetic field (IMF), and different phases of magnetospheric substorms. The average location of magnetopause is examined using magnetic field observations from multiple satellites (THEMIS, RBSP, and MMS), and the Shue model utilizing OMNI solar wind data for a period of five years from 2016–2020. We estimate average position of the magnetopause using Shue model through superposed epoch analysis of standoff distance and tail flaring angle at different substorm timings (onset, peak and end) and from in-situ measurements through 2D equatorial maps of average Δ B_Z under IMF |B_z|> 0 conditions. Our findings reveal the occurrence of substorms during both northward and southward IMF orientations and highlight an earthward movement of the magnetopause during substorm onset and peak, followed by a relaxation during the substorm end time, for both northward and southward IMF orientations. Notably, the magnetopause undergoes significant compression and reaches its closest point to the Earth during instances of strong southward IMF (B_Z < -5), particularly during the substorm peak. The empirical model provides accurate estimation of the magnetopause location during periods of both strong northward and southward IMF |B_z|>5, as the model curve traverses a distinct location (Δ B_Z = 0) representing the magnetopause shown in the 2D average map of Δ B_Z.