Net field‐aligned currents controlled by the polar ionospheric conductivity

Nakano, S.; Iwamoto, Toshihiko; Yamashita, S.

doi:10.1029/2001ja900177

Cited by 11 publications

(13 citation statements)

References 12 publications

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“…The afternoon R1 and R2 current density maxima move from afternoon daytime in summer to the dark pre-midnight sector in winter, suggesting a redistribution of the FACs in response to the nightside location of particle produced, enhanced ionospheric conductivity. This redistribution of FAC to the nightside may also explain the increased FAC intensities near midnight during winter relative to summer observed by Nakano et al (2002) and Ohtani et al (2005a). The transfer of FAC from the dayside in summer to the nightside in winter also appears to have an IMF dependence.…”

Section: Summary Of Seasonal Fac Observationsmentioning

confidence: 73%

Seasonal and interplanetary magnetic field dependence of the field-aligned currents for both Northern and Southern Hemispheres

et al. 2009

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Abstract. The configuration of the Earth's magnetosphere under various Interplanetary Magnetic Field (IMF) and solar wind conditions alters the global distribution of FieldAligned Currents (FACs) at the high latitude ionospheres. We use magnetic field data obtained from the Iridium constellation to extend recent studies that infer the dependence of the global FAC configuration on IMF direction and magnitude, hemisphere and season. New results are a reduced IMF B y influence on the FAC configuration for the winter hemisphere and a redistribution of FAC to the nightside for winter relative to the summer hemisphere. These effects are linked to the winter ionosphere conductance distribution being dominated by localised nightside enhancement associated with ionisation from energetic particle precipitation. A comparison of an estimated open-closed field line boundary (OCFLB) with the Region 1 FAC locations shows reasonable agreement for summer FAC configurations. However, the OCFLB location is decoupled from the Region 1 FACs in winter, especially for IMF B z >0.

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Section: Summary Of Seasonal Fac Observationsmentioning

confidence: 73%

Seasonal and interplanetary magnetic field dependence of the field-aligned currents for both Northern and Southern Hemispheres

et al. 2009

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“…Moreover, observations from ground were also in the favor of the feedback conductivity mechanism. Nakano et al (2002) analyzed local characteristics of the geomagnetic field to extract information on the field-aligned current variation. They showed that the net field-aligned currents are upward in the nightside region and downward in the dayside.…”

Section: Discussionmentioning

confidence: 99%

Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

et al. 2004

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Abstract. The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite provides a global view of the north auroral region in three spectral channels, including the SI12 camera sensitive to Doppler shifted Lyman-α emission. FUV images are used to produce instantaneous maps of electron mean energy and energy fluxes for precipitated protons and electrons. We describe a method to calculate ionospheric Hall and Pedersen conductivities induced by auroral proton and electron ionization based on a model of interaction of auroral particles with the atmosphere. Different assumptions on the energy spectral distribution for electrons and protons are compared. Global maps of ionospheric conductances due to instantaneous observation of precipitating protons are calculated. The contribution of auroral protons in the total conductance induced by both types of auroral particles is also evaluated and the importance of proton precipitation is evaluated. This method is well adapted to analyze the time evolution of ionospheric conductances due to precipitating particles over the auroral region or in particular sectors. Results are illustrated with conductance maps of the north polar region obtained during four periods with different activity levels. It is found that the proton contribution to conductance is relatively higher during quiet periods than during substorms. The proton contribution is higher in the period before the onset and strongly decreases during the expansion phase of substorms. During a substorm which occurred on 28 April 2001, a region of strong proton precipitation is observed with SI12 around 14:00 MLT at ∼75 • MLAT. Calculation of conductances in this sector shows that neglecting the protons contribution would produce a large error. We discuss possible effects of the proton precipitation on electron precipitation in auroral arcs. The increase in the ionospheric conductivity, induced by a former proton precipitation can reduce the potential drop along field lines in the upward field-aligned currents by creating an opposite polarization electric field. This feedback mechanism possibly reduces the electron acceleration.

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“…We used the standard deviation within 2100–0300 MLT in this procedure because we can ensure that the variations of Δ D within this MLT range contain little ionospheric current effects and that they are regarded as pure field‐aligned current effects. We must also consider a seasonal dependence of Δ D as indicated by Nakano et al [2002] because the seasonal dependence may cause the difference in Δ D between the two hemispheres to affect the MLT profile of Δ D derived from the data obtained in both of the hemispheres. In order to avoid this problem, we analyzed events around the equinoxes in this paper except for a statistical analysis.…”

Section: Data Processingmentioning

confidence: 99%

Storm‐time field‐aligned currents on the nightside inferred from ground‐based magnetic data at midlatitudes: Relationships with the interplanetary magnetic field and substorms

Nakano

Iwamoto

2005

J. Geophys. Res.

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[1] On the basis of analysis of east-west geomagnetic disturbance fields at midlatitudes, we investigated the characteristics of temporal variations of field-aligned currents on the nightside during geomagnetic storms. The results indicate that upward field-aligned currents develop on the nightside, especially in the postmidnight, when the interplanetary magnetic field (IMF) is directed southward. This suggests that the upward field-aligned currents are principally associated with the convection electric field. It is also found that the upward field-aligned currents in the postmidnight can be intensified at substorm expansion, while they principally depend on the southward component of the IMF. The intensification of the upward currents is regarded as a different physical process from the formation of a substorm current wedge at a substorm expansion. We discuss some possible effects of the IMF and substorms on the generation of the upward currents on the nightside, especially in the postmidnight.Citation: Nakano, S., and T. Iyemori (2005), Storm-time field-aligned currents on the nightside inferred from ground-based magnetic data at midlatitudes: Relationships with the interplanetary magnetic field and substorms,

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Net field‐aligned currents controlled by the polar ionospheric conductivity

Cited by 11 publications

References 12 publications

Seasonal and interplanetary magnetic field dependence of the field-aligned currents for both Northern and Southern Hemispheres

Seasonal and interplanetary magnetic field dependence of the field-aligned currents for both Northern and Southern Hemispheres

Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations

Storm‐time field‐aligned currents on the nightside inferred from ground‐based magnetic data at midlatitudes: Relationships with the interplanetary magnetic field and substorms

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