The Intense Substorm Incidence in Response to Interplanetary Shock Impacts and Influence on Energetic Electron Fluxes at Geosynchronous Orbit

Abstract

The interaction between interplanetary (IP) shocks and the Earth's magnetosphere would generate/excite various types of geomagnetic phenomena. In order to analyze what kind of IP shock is more likely to trigger intense substorms (SME/AE > 1,000 nT) and how the energetic electrons response to intense substorms at geosynchronous orbit, we perform a systematic survey of 246 IP shock events using SuperMag and LANL observations between 2001 and 2013. The statistical analysis shows that intense substorms (SME > 1,000 nT) triggered by IP shocks are most likely to occur under the southward interplanetary magnetic field (IMF) and fast solar wind preconditions. Besides, intense substorms after the IP shock arrival are much more likely to occur when IMF points toward (away from) the Sun around spring (autumn) equinox, which can be ascribed to the Russell‐McPherron effect. Thus, the IMF Bs precondition of an IP shock and the Russell‐McPherron effect can be considered as precursors of an intense substorm. Furthermore, after the shock arrival associated with intense substorms, low‐energy (<200 keV) electron fluxes increase significantly at geosynchronous orbit, and high‐energy (>200 keV) electron fluxes decrease. The spectral index becomes softer with intense substorms and remains almost unchanged with moderate substorms no matter whether the IMF precondition is southward or northward.

Simultaneous Cross‐Energy Ion Response and Wave Generation After the Impact of an Interplanetary Shock

“…Liu and Zong (2015) emphasized the critical role of the radial gradient of phase space density (PSD) in the change of electron fluxes by the compressional effect of IP shock. Ma, Zong, and Liu (2019) found softer energy distributions of electrons during intense substorms driven by IP shocks.…”

Energetic Electron Enhancement and Dropout Echoes Induced by Solar Wind Dynamic Pressure Decrease: The Effect of Phase Space Density Profile

“…Ma et al. (2019) further found that during intense substorms triggered by IP shocks, the electron spectrum index in geosynchronous orbits became significantly larger.…”

Energetics of Shock-triggered Supersubstorms (SML < −2500 nT)

“…Yue et al (2017) noted that after the shock impingement, chorus waves intensified in the postmidnight to the prenoon sector, while the plasmaspheric hiss decreased on the dayside and intensified during night (however, see the contrary findings in Tsurutani et al 2019 andMa et al 2022). Ma et al (2019) found that for shock-triggered substorms with SME > 1000 nT (including both traditional substorms and supersubstorms), E < 200 keV electron fluxes increased significantly. At the same time, >200 keV electron fluxes decreased.…”

“…It is well recognized that local midnight-sector substorms (Akasofu 1964) are often triggered by interplanetary shock impingements onto the magnetosphere (Heppner 1955;Schieldge & Siscoe 1970;Kawasaki et al 1971;Burch 1972;Kokubun et al 1977;Akasofu & Chao 1980;Chua et al 2001;Boudouridis et al 2003;Tsurutani & Zhou 2003;Liou et al 2004;Yue et al 2010Yue et al , 2011Yue et al , 2016Ma et al 2019;Oliveira et al 2021;Zong et al 2021). , using Polar UV data (Torr et al 1995), have shown that midnight-sector substorm onsets started within ∼2 minutes of the shock compression of the magnetosphere, and that the energy for shock-induced substorms could be provided by precursor interplanetary magnetic field (IMF) southward (B s ) components up to ∼1.5 hr prior to the shock arrival.…”