Abstract
The influence of IMF components on meso-scale field-aligned currents (FACs) is investigated with an aim to establish how different IMF components influence the occurrence and distribution of FACs. The field-aligned currents (FACs) are calculated from the curl of the Ampere’s law to the magnetic field recorded by CHAMP satellite during 24 major geomagnetic storms. To determine the field-aligned currents at extreme mesoscale range ∼150 - 250 km, a low-pass filter to FACs with a cutoff period of 20s is applied. The peak-to-peak amplitude of FAC density, with the maximum difference ≤ 3<sup>0</sup> MLAT, is determined and used to define the FAC range. The results indicate high occurrence of FACs centered about IMF ≈ 0, for large values of Dst. The magnitude of FACs is in general affected by all the three IMF components, alongside other ionospheric factors such as solar wind speed and density. Magnetic reconnection, under -B<sub>Z</sub> is a major FACs drivers and is significant in the dayside northern hemisphere. The reconnection is not symmetric in both hemispheres. We find a possible electrodynamic similarity between the dayside northern hemisphere and nightside southern hemisphere, prominent along B<sub>X</sub> when B<sub>Z</sub> is negative. This interesting observation can further be investigated.
Highlights
A number of systems of global-scale electrical currents are generated in the near-Earth environments due to the interaction between the solar wind and interplanetary magnetic field
Higher field-aligned currents (FACs) range occurrence is exhibited during positive Interplanetary magnetic field (IMF) BX than during negative IMF BX during the dayside magnetic local time (MLT) sector and the reverse is observed in the nightside
The IMF BX component had dayside FAC range distribution and magnitude responding to positive IMF BX compared to negative IMF BX while the reverse is observed during the nightside MLT sector (Figure 6d)
Summary
A number of systems of global-scale electrical currents are generated in the near-Earth environments due to the interaction between the solar wind and interplanetary magnetic field One of such currents is the field-aligned currents (FACs), commonly referred to as Birkeland currents after he first suggested their existence in the upper atmosphere in 1908. This current system plays a role in coupling the energy from the magnetosphere to the high latitude conducting ionospheres. Joule heating of the thermosphere can have undesired effects on satellites in low Earth orbits [7] These effects result from large currents, totaling approximately 4 MA for typical solar wind and IMF conditions and increasing as more extreme driving occurs [34].
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