Antisunward net Birkeland current system deduced from the Oersted satellite observation

Yamashita, S.; Iwamoto, Toshihiko; Nakano, S.; Kamei, T.; Araki, Tohru

doi:10.1029/2001ja900160

Cited by 5 publications

(20 citation statements)

References 17 publications

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“…This is also supported by other authors (e.g. Langel and Sweeney 1971;Iyemori 1990;Yamashita et al 2002) who found that residuals of Y and H components observed at the surface and at satellite altitude show a deflection in the same sense, thus implying that the source current is not in the ionosphere. The blue area of Fig.…”

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confidence: 78%

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Unmodelled magnetic contributions in satellite-based models

2016

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A complex system of electric currents flowing in the ionosphere and magnetosphere originates from the interaction of the solar wind and the Interplanetary Magnetic Field (IMF) with the Earth's magnetic field. These electric currents generate magnetic fields contributing themselves to those measured by both ground observatories and satellites. Here, low-resolution (1 Hz) magnetic vector data recorded between 1 March 2014 and 31 May 2015 by the recently launched Swarm constellation are considered. The core and crustal magnetic fields and part of that originating in the magnetosphere are removed from Swarm measurements using CHAOS-5 model. Low-and mid-latitude residuals of the geomagnetic field representing the ionospheric and the unmodelled magnetospheric contributions are investigated, in the Solar Magnetic frame, according to the polarity of IMF B y (azimuthal) and B z (north-south) components and to different geomagnetic activity levels. The proposed approach makes it possible to investigate the features of unmodelled contributions due to the external sources of the geomagnetic field. Results show, on one side, the existence of a relation between the analysed residuals and IMF components B y and B z , possibly due to the long distance effect of high-latitude field-aligned currents. On the other side, they suggest the presence of a contribution due to the partial ring current that is activated during the main phase of geomagnetic storms. The perturbation observed on residuals is also compatible with the effect of the net field-aligned currents. Moreover, we have quantitatively estimated the effect of these current systems on computed residuals.

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confidence: 78%

“…Evidences of net field-aligned currents have been discovered later in satellite observations (e.g. Yamashita et al 2002;Nakano and Iyemori 2003). According to Crooker and Siscoe (1981) they are expected to flow into the ionosphere on the day-side and out of the ionosphere on the night-side.…”

Section: Resultsmentioning

confidence: 99%

Unmodelled magnetic contributions in satellite-based models

2016

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“…This model of the antisunward current system well explains not only the dawn‐dusk asymmetry of the north‐south geomagnetic disturbances but also the characteristics of the east‐west geomagnetic disturbances that the westward and eastward disturbances are seen on the dayside and nightside, respectively, as indicated by many low and middle latitudes ground observations [e.g., Grafe et al , 1986; Iyemori , 1990; Nakano et al , 2002]. Yamashita et al [2002] have shown that the antisunward current system explains the latitudinal magnetic field profile at low and middle latitudes even above the ionosphere by using the magnetic data from the Ørsted satellite. Suzuki and Fukushima [1984, 1998] have also derived the antisunward net currents from an Ampère's law integral along the Magsat orbit.…”

Section: Introductionmentioning

confidence: 61%

“…This model of the antisunward current system well explains not only the dawn-dusk asymmetry of the north-south geomagnetic disturbances but also the characteristics of the east-west geomagnetic disturbances that the westward and eastward disturbances are seen on the dayside and nightside, respectively, as indicated by many low and middle latitudes ground observations [e.g., Grafe et al, 1986;Iyemori, 1990;Nakano et al, 2002]. Yamashita et al [2002] have shown that the antisunward current system explains the latitudinal JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO.…”

Section: Introductionmentioning

confidence: 68%

Local time distribution of net field‐aligned currents derived from high‐altitude satellite data

Nakano

Iwamoto

2003

J. Geophys. Res.

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[1] In order to explain features of geomagnetic disturbances observed at low and middle latitudes such as the dawn-dusk asymmetry in the north-south component, an antisunward current system has been proposed. The antisunward current system consists of net downward field-aligned currents on the dayside, antisunward auroral electrojet currents, and net upward field-aligned currents on the nightside. However, the net field-aligned currents consisting in this current system have not been established by spacecraft observations yet. In order to discuss whether this antisunward current system actually exists or not and whether this current system actually causes the features of geomagnetic disturbances at low and middle latitudes or not, we statistically investigated the global structure of the geomagnetic disturbances generated by the field-aligned currents in the inner magnetosphere by using the magnetic field data obtained by the DE-1 satellite. On the basis of the results, local time distribution of the net field-aligned currents was estimated. Net downward currents are found in the prenoon sector, and net upward currents are found in the premidnight sector. In the postnoon and the postmidnight sector, net field-aligned currents are rather small on an average. The net downward field-aligned currents in the prenoon would feed some portions of the auroral electrojets, and the portions would flow from the prenoon to the premidnight to connect with the net upward field-aligned currents in the premidnight. These results are consistent with ground geomagnetic observations in the auroral region. In addition, we proposed a possible current system, which consistently explains our results and many other observations. It was also confirmed that the current system can actually cause the features of geomagnetic disturbances on the ground.

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“…One of well‐known midlatitude east‐west magnetic disturbances caused by field‐aligned currents is a substorm current wedge effect, which indicates an eastward/westward disturbance in the premidnight and a westward/eastward disturbance in the postmidnight in the northern/southern hemisphere [ Clauer and McPherron , 1974]. On the other hand, an eastward/westward disturbance in the northern/southern hemisphere over the entire nightside is also common at midlatitudes (hereafter we will refer to eastward disturbances in the northern hemisphere and westward disturbances in the southern hemisphere as “positive” east‐west disturbances) [e.g., Iyemori , 1990; see also Yamashita et al , 2002]. These positive disturbances have been explained as a superposition of the effects of the Region 1 current system and those of the Region 2 current system by Nakano and Iyemori [2003].…”

Section: Introductionmentioning

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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Antisunward net Birkeland current system deduced from the Oersted satellite observation

Cited by 5 publications

References 17 publications

Unmodelled magnetic contributions in satellite-based models

Unmodelled magnetic contributions in satellite-based models

Local time distribution of net field‐aligned currents derived from high‐altitude satellite data

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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