Latitudinal Distribution of Dayside Magnetospheric Currents Based on Cluster Observations

• Published in: Journal of geophysical research. Space physics Vol. 129; no. 10
• Main Authors: Du, Yingshuai, Liu, Wenlong, Zhang, Dianjun, Tan, Xin, Dunlop, Malcolm W.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-10-2024
• Subjects: Anisotropy; Clusters; Current density; Current distribution; Dynamic pressure; Equator; Flow-density-speed relationships; Fluxgate magnetometers; magnetosphere; Magnetospheres; Magnetospheric currents; Plasma pressure; ring current; Saturn; Solar wind; Solar wind flow; Solar wind speed; Topology; Wind flow; Wind speed
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2024JA032943

Based on the curlometer method, we calculate the azimuthal component of the current density from nearly 19 years of Fluxgate Magnetometer (FGM) data of Cluster and investigate its latitudinal distribution in the dayside noon sector (09:00–15:00 magnetic local time, MLT). A crossing event in the noon meridian plane shows an unexpected eastward current at a geocentric distance of 8 RE, away from the equator with latitudes of 30–40°. Further statistical results of the current distribution show that, the topology of the current can be radially divided into the inner and outer branches over the whole rxy − z plane (rxy = x2+y2 $\sqrt{{x}^{2}+{y}^{2}}$ and z are in solar magnetic (SM) coordinates), with the separation point of these two branches at a geocentric distance of about 8 RE. The current variations of the inner and outer branches are different under different Kp, solar wind flow speed Vsw, and solar wind dynamic pressure Pdyn. It is shown that the current densities in both the inner and outer branches increase significantly with the Kp. High solar wind dynamic pressure enhances the current density of the outer branch, while high solar wind speed, on the contrary, enhances that of the inner branch. The formation of the outer branch may be related to the anisotropy of plasma pressure.
Key Points
In‐situ statistics of the current distribution in the dayside is presented
The topology of the current in the dayside can be divided into the inner and outer branches
The variation of the current density in the two branches with changes in solar wind conditions and geomagnetic activity are different