Role of Impact Angle on Equatorial Electrojet (EEJ) Response to Interplanetary (IP) Shocks

• Published in: Journal of geophysical research. Space physics 2024-06, Vol.129 (6), p.n/a
• Main Authors: Nilam, B., Tulasi Ram, S., Oliveira, Denny M., Dimri, A. P.
• Format: Article
• Language: English
• Subjects: Convection; Disturbances; Dynamic pressure; Earth; Earth magnetosphere; Electric fields; Electric power; Electrojets; Equatorial electrojet; Geomagnetic disturbances; Geomagnetic field; Geomagnetism; Impact angle; interplanetary (IP) shocks; Ionospheric currents; Latitude; Magnetic fields; Magnetospheric currents; Saturn; shock impact angle; Solar wind; Solar wind structure; Space weather; Transmission lines; Weather effects
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2024JA032638

Interplanetary (IP) shocks are one of the dominant solar wind structures that can significantly impact the Geospace when impinge on the Earth's magnetosphere. IP shocks severely distort the magnetosphere and induce dramatic changes in the magnetospheric currents, often leading to large disturbances in the geomagnetic field. Sudden enhancements in the solar wind dynamic pressure (PDyn) during IP shocks cause enhanced high‐latitude convection electric fields which penetrate promptly to equatorial latitudes. In response, the equatorial electrojet (EEJ) current exhibits sharp changes of magnitudes primarily controlled by the change in PDyn and the local time. In this paper, we further investigated the influence of shock impact angle on the EEJ response to a large number (306) of IP shocks that occurred during 2001–2021. The results consistently show that the EEJ exhibits a heightened response to the shocks that head‐on impact the magnetosphere (frontal shocks) than those with inclined impact (inclined shocks). The greater EEJ response during the frontal shocks could be due to a more intensified high‐latitude convection electric field resulting from the symmetric compression of the magnetosphere. Finally, an existing empirical relation involving PDyn and local time is improved by including the effects of impact angle, which can quantitatively better predict the EEJ response to IP shocks. Plain Language Summary Solar Wind, a continuous stream of high‐energy particles emanating from the Sun, is ubiquitous in interplanetary (IP) space. In unison, the energetic and/or transient eruptions on the Sun often release bursts of fast solar wind. When this fast solar wind interacts with the ambient solar wind in the IP space, a shock front is formed known as IP shock. These IP shocks (if Earth‐directed) can impinge on the Earth's magnetosphere and transfer tremendous amounts of energy and momentum. As a result, the Earth's magnetic field is often severely disturbed. Severe geomagnetic disturbances are known to cause a myriad of space weather effects from the loss of satellites in space to damage of electrical power grids and transmission lines on ground. Historically, geomagnetic field disturbances are known to be more cataclysmic at high latitudes and lessen at latitudes below the auroral region. However, these disturbances again dramatically enhance at equatorial latitudes due to a unique ionospheric current system, known as equatorial electrojet (EEJ). This study provid