Relative contribution of ionospheric conductivity and electric field to ionospheric current

Sugino, M.

doi:10.1029/2001ja007545

Cited by 22 publications

(31 citation statements)

References 34 publications

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“…An extension of the conductivity-driven region into the late morning up to 09:00 MLT suggested by the present study is also in rough agreement with the conductivitydominant interval of 20:00-08:00 MLT proposed by Sugino et al (2002). These authors observed two peaks of conductivity dominance: one near midnight and one in the late morning around 06:00 MLT.…”

Section: Electric Field and Conductance Control Of Currentssupporting

confidence: 80%

“…Extending the same argument further towards the dayside, one can propose that a drop in ρ(δH, U i ) at 06:00-09:00 MLT is due to relative weakening of the electric field control in this time sector. Statistically, Sugino et al (2002) showed that for all K p conditions the electric field orientation switched from southward to northward in the late morning sector, just prior to 12:00 MLT, which is normally a characteristic of a change from the westward to eastward convection electrojets. The substantial increase in ρ(δH, U i ) across the 12:00 MLT boundary and considerable ρ(δH, U i ) correlations at 09:00-21:00 MLT observed in this study thus suggest that the entire eastward convection electrojet is dominated by the electric field including the dayside.…”

Section: Electric Field and Conductance Control Of Currentsmentioning

confidence: 99%

“…Kamide and Vickrey (1983) thus found that the electric field exerts a dominant role in the evening and late morning sectors. More recently, Sugino et al (2002) showed that the conductivity-dominant region can extend to 08:00 MLT just after the dawn terminator.…”

mentioning

confidence: 99%

“…From this information the ionospheric currents are inferred using Ohm's law (e.g. Sugino et al, 2002). In this approach all 3 parameters are provided by the same instrument at the same resolution and all the measurements are coincident and simultaneous.…”

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On the relationship between auroral absorption, electrojet currents and plasma convection

et al. 2009

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Abstract. In this study, the relationship between auroral absorption, electrojet currents, and ionospheric plasma convection velocity is investigated using a series of new methods where temporal correlations are calculated and analysed for different events and MLT sectors. We employ cosmic noise absorption (CNA) observations obtained by the Imaging Riometer for Ionospheric Studies (IRIS) system in Kilpisjärvi, Finland, plasma convection measurements by the European Incoherent Scatter (EISCAT) radar, and estimates of the electrojet currents derived from the Tromsø magnetometer data. The IRIS absorption and EISCAT plasma convection measurements are used as a proxy for the particle precipitation component of the Hall conductance and ionospheric electric field, respectively. It is shown that the electrojet currents are affected by both enhanced conductance and electric field but with the relative importance of these two factors varying with magnetic local time (MLT). The correlation between the current and electric field (absorption) is the highest at 12:00-15:00 MLT (00:00-03:00 MLT). It is demonstrated that the electric-field-dominant region is asymmetric with respect to magnetic-noon-midnight meridian extending from 09:00 to 21:00 MLT. This may be related to the recently reported absence of mirror-symmetry between the effects of positive and negative IMF B y on the high-latitude plasma convection pattern. The conductivity-dominant region is somewhat wider than previously thought extending from 21:00 to 09:00 MLT with correlation slowly declining from midnight towards the morning, which is interpreted as being in part due to highenergy electron clouds gradually depleting and drifting from midnight towards the morning sector. The conductivitydominant region is further investigated using the extensive Correspondence to: R. A. Makarevich (r.makarevich@latrobe.edu.au) IRIS riometer and Tromsø magnetometer datasets with results showing a distinct seasonal dependence. The region of high current-absorption correlation extends from 21:00 to 06:00 MLT near both equinoxes, however, it is narrower and rotated towards the morning (02:00-07:00 MLT) in summer, while in winter the correlation shows much greater variability with MLT. During periods of high current-electricfield correlation, the relationship between electric field and absorption can be described as an inverse proportionality, which can be explained by limitation of the electrojet current by the magnetospheric generator. Possible cases of electron heating absorption are also investigated with absorption showing no obvious dependence on the ion velocity or electron temperature.

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Section: Electric Field and Conductance Control Of Currentssupporting

confidence: 80%

Section: Electric Field and Conductance Control Of Currentsmentioning

confidence: 99%

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confidence: 99%

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On the relationship between auroral absorption, electrojet currents and plasma convection

et al. 2009

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“…Hardy et al, 1985), that the difference between the h peak in the EJ as compared to the WJ, is due to the difference in the hardness of the precipitating particles. This also shows up in the mean altitude of the electrojets (Kamide and Brekke, 1977;Sugino et al, 2002). If we take the values of h peak given above (Fig.…”

Section: Eiscat Statistics In Search For Vptmentioning

confidence: 99%

Auroral E-region electron density height profile modificationby electric field driven vertical plasma transport:some evidence in EISCAT CP-1 data statistics

et al. 2004

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Abstract.A model developed several years ago by Huuskonen et al. (1984) predicted that vertical transport of ions in the nocturnal auroral E-region ionosphere can shift the electron density profiles in altitude during times of sufficiently large electric fields. If the vertical plasma transport effect was to operate over a sufficiently long enough time, then the real height of the E-region electron maximum should be shifted some km upwards (downwards) in the eastward (westward) auroral electrojet, respectively, when the electric field is strong, exceeding, say, 50 mV/m. Motivated by these predictions and the lack of any experimental verification so far, we made use of the large database of the European Incoherent Scatter (EISCAT) radar to investigate if the anticipated vertical plasma transport is at work in the auroral E-region ionosphere and thus to test the Huuskonen et al. (1984) model. For this purpose a new type of EIS-CAT data display was developed which enabled us to order a large number of electron density height profiles, collected over 16 years of EISCAT operation, according to the electric field magnitude and direction as measured at the same time at the radar's magnetic field line in the F-region. Our analysis shows some signatures in tune with a vertical plasma transport in the auroral E-region of the type predicted by the Huuskonen et al. model. The evidence brought forward is, however, not unambiguous and requires more rigorous analysis.

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Magnetic reconnection in the auroral acceleration region

Chaston

2015

Geophysical Research Letters

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Evidence is presented for the operation of extreme guide field magnetic reconnection in the presence of sheared flows in a narrow current sheet through the auroral acceleration region. Using auroral imagery, magnetically conjugate particle measurements and a 3‐D reduced MHD simulation, vortical motions in a narrow, rapidly evolving auroral arc indicative of the operation of magnetic tearing are identified. An estimate of the contribution of this process to the observed rate of energy deposition at the ionosphere shows that while this contribution can be significant it remains a minor fraction of the total. These observations are placed in the context of low magnetic shear reconnection made possible in plasmas with low plasma beta.

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Relative contribution of ionospheric conductivity and electric field to ionospheric current

Cited by 22 publications

References 34 publications

On the relationship between auroral absorption, electrojet currents and plasma convection

On the relationship between auroral absorption, electrojet currents and plasma convection

Auroral E-region electron density height profile modificationby electric field driven vertical plasma transport:some evidence in EISCAT CP-1 data statistics

Magnetic reconnection in the auroral acceleration region

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