Ionospheric conductivity dependence of dayside region-0, 1, and 2 field-aligned current systems: statistical study with DMSP-F7

Abstract

Abstract. The present study statistically examines the dependence of the intensities of dayside (MLT=8-12 h) large-scale field-aligned currents (FACs) on the ionospheric conductance using the summary data of DMSP-F7 constructed by the procedure of Higuchi and Ohtani (2000). We have found that, in the dayside region, R1 and R0 have a higher correlation between ionospheric conductivity and FAC intensity than R2, suggesting that R0 and R1 are driven by a more voltage-like source than R2. This result is consistent with the idea that R1 and R0 are driven by the interaction between the solar wind and the open magnetospheric magnetic field. We have also found that dayside FAC intensities are latitudinally well balanced when they have a three sheet structure (R0, R1 and R2); on the other hand, for a two sheet structure (R1 and R2), the intensity of R1 is larger than that of R2, so that the net current has the polarity of R1.

Interhemispheric Asymmetry in Response of Low‐Latitude Ionosphere to Perturbation Electric Fields in the Main Phase of Geomagnetic Storms

“…The R1 (R2) FAC flows into the poleward (equatorward) boundary of auroral latitudes in midnight-noon (noon-midnight) sector centered around dawn (dusk) and flowing out of auroral ionosphere in noon-midnight (midnight-noon) sector centered around dusk (dawn). Coming to the interhemispheric asymmetry as observed in the present study, recent investigations on seasonal dependence of FACs have highlighted prominent differences accounting up to 2-3 times higher magnetic activity in summer (sunlit) than winter (dark) hemisphere although the conductivity in winter hemisphere could be one-tenth of the summer hemisphere (Haraguchi et al, 2004;Mishin et al, 2016). The current density and resulting ionospheric DP2 Hall currents and Pedersen currents due to each of the R0, R1, and R2 currents is highly specific for a given local time be it day or night (Haraguchi et al, 2004).…”

“…This brings to the simulation studies (e.g., Huang, Foster, & Kelley, 2005;Huba et al, 2005;Maruyama et al, 2005 andPeymirat et al, 2000) of under (over) shielding conditions and its relation with equatorial E × B drifts (Huang, 2015(Huang, , 2019 wherein imbalance between R1 and R2 currents has been shown as shape function of southward (northward) IMF Bz or more effectively as a step or linear shape function of PC potential. Thus, the effectiveness of either under and over shielding conditions at a time largely depends on response of R1 and R2 currents and its effect on PC potential drop as well as auroral electrojet variations (Haraguchi et al, 2004;Moon, 2012;Pulkkinen et al, 2016;Myllys et al, 2016). Thus, the effectiveness of either under and over shielding conditions at a time largely depends on response of R1 and R2 currents and its effect on PC potential drop as well as auroral electrojet variations (Haraguchi et al, 2004;Moon, 2012;Pulkkinen et al, 2016;Myllys et al, 2016).…”

Solar Illumination Dependence of the Auroral Electrojet Intensity: Interplay Between the Solar Zenith Angle and Dipole Tilt

“…On the dayside the large-scale field-aligned currents (FACs), Region 1 (R1) and Region 2 (R2) currents, are noticeably stronger (i.e., the FAC density is larger) and more intense (i.e., the FAC intensity is larger) in the summer/sunlit hemisphere than in winter/dark hemisphere (e.g., Coxon et al, 2016;Fujii et al, 1981;Haraguchi et al, 2004;Ohtani, Ueno, Higuchi, & Kawano, 2005;Wang et al, 2005), which can be attributed to the higher ionospheric conductance of the summer/sunlit hemisphere due to solar extreme ultraviolet (EUV) radiation. On the dayside the large-scale field-aligned currents (FACs), Region 1 (R1) and Region 2 (R2) currents, are noticeably stronger (i.e., the FAC density is larger) and more intense (i.e., the FAC intensity is larger) in the summer/sunlit hemisphere than in winter/dark hemisphere (e.g., Coxon et al, 2016;Fujii et al, 1981;Haraguchi et al, 2004;Ohtani, Ueno, Higuchi, & Kawano, 2005;Wang et al, 2005), which can be attributed to the higher ionospheric conductance of the summer/sunlit hemisphere due to solar extreme ultraviolet (EUV) radiation.…”

Modeling the UT effect in global distribution of ionospheric electric fields

“…The intensity of a voltagedriven current is proportional to the ionospheric Pedersen conductivity s P but that of the currentdriven current is not. Recently, Haraguchi et al (2004) investigated the correlation between the ionospheric conductivity and the FAC intensity in the dayside region using DMSP-F7 magnetometer data. These authors concluded that R0/R1 is associated with a voltage-like source and R2 is associated with a more current-like source.…”