TY - JOUR

T1 - Substorm‐Ring Current Coupling

T2 - A Comparison of Isolated and Compound Substorms

AU - Sandhu, J. K.

AU - Rae, I.J.

AU - Freeman, M.P.

AU - Gkioulidou, M.

AU - Forsyth, C.

AU - Reeves, G. D.

AU - Murphy, K. R.

AU - Walach, Maria

N1 - An edited version of this paper was published by AGU. Copyright 2019 American Geophysical Union. Sandhu, J. K., Rae, I. J., Freeman, M. P., Gkioulidou, M., Forsyth, C., Reeves, G. D., et al. ( 2019). Substorm‐ring current coupling: A comparison of isolated and compound substorms. Journal of Geophysical Research: Space Physics, 124. https://doi.org/10.1029/2019JA026766. To view the published open abstract, go to http://dx.doi.org and enter the DOI.

PY - 2019/8/31

Y1 - 2019/8/31

N2 - Substorms are a highly variable process, which can occur as an isolated event or as part of a sequence of multiple substorms (compound substorms). In this study we identify how the low‐energy population of the ring current and subsequent energization varies for isolated substorms compared to the first substorm of a compound event. Using observations of H+ and O+ ions (1 eV to 50 keV) from the Helium Oxygen Proton Electron instrument onboard Van Allen Probe A, we determine the energy content of the ring current in L‐MLT space. We observe that the ring current energy content is significantly enhanced during compound substorms as compared to isolated substorms by ∼20–30%. Furthermore, we observe a significantly larger magnitude of energization (by ∼40–50%) following the onset of compound substorms relative to isolated substorms. Analysis suggests that the differences predominantly arise due to a sustained enhancement in dayside driving associated with compound substorms compared to isolated substorms. The strong solar wind driving prior to onset results in important differences in the time history of the magnetosphere, generating significantly different ring current conditions and responses to substorms. The observations reveal information about the substorm injected population and the transport of the plasma in the inner magnetosphere.

AB - Substorms are a highly variable process, which can occur as an isolated event or as part of a sequence of multiple substorms (compound substorms). In this study we identify how the low‐energy population of the ring current and subsequent energization varies for isolated substorms compared to the first substorm of a compound event. Using observations of H+ and O+ ions (1 eV to 50 keV) from the Helium Oxygen Proton Electron instrument onboard Van Allen Probe A, we determine the energy content of the ring current in L‐MLT space. We observe that the ring current energy content is significantly enhanced during compound substorms as compared to isolated substorms by ∼20–30%. Furthermore, we observe a significantly larger magnitude of energization (by ∼40–50%) following the onset of compound substorms relative to isolated substorms. Analysis suggests that the differences predominantly arise due to a sustained enhancement in dayside driving associated with compound substorms compared to isolated substorms. The strong solar wind driving prior to onset results in important differences in the time history of the magnetosphere, generating significantly different ring current conditions and responses to substorms. The observations reveal information about the substorm injected population and the transport of the plasma in the inner magnetosphere.

U2 - 10.1029/2019JA026766

DO - 10.1029/2019JA026766

M3 - Journal article

VL - 124

SP - 6776

EP - 6791

JO - Journal of Geophysical Research: Space Physics

JF - Journal of Geophysical Research: Space Physics

SN - 2169-9402

IS - 8

ER -