Magnetosphere‐Ionosphere Convection Under the Due Northward IMF

Tanaka, Toshiaki; Obara, Takao; Watanabe, Midori; Fujita, Shigeru; Ebihara, Yusuke; Kataoka, Ryuho; Den, Mitsue

doi:10.1029/2019ja026547

Cited by 10 publications

(30 citation statements)

References 64 publications

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“…For such comparison in the ionosphere, validity of the global simulation has been confirmed also under the northward interplanetary magnetic field (IMF), in reproducing the Sun‐aligned arc (Tanaka, Obara, et al, ), the theta aurora (Tanaka et al, , ), and the fan‐shaped arc (Tanaka, Obara, et al, ). These phenomena have been known for a long time, but consideration for their causes have been staying at the level of estimation.…”

Section: Introductionmentioning

confidence: 90%

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Reproduction of Ground Magnetic Variations During the SC and the Substorm From the Global Simulation and Biot‐Savart's Law

et al. 2020

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In this paper, currents causing the sudden commencement (SC), the AU/AL indices, and the positive bay during the substorm are identified from the global simulation and Biot‐Savart's law. Candidate currents assumed as causes of these ground magnetic variations are the ionospheric Hall current, the ionospheric Pedersen current, the field‐aligned current (FAC), and other magnetospheric currents than the FAC. In general, FAC effect and Pedersen current effect cancel out each other under the restriction of Fukushima's theorem. During the SC, for instance, the midlatitude preliminary positive impulse appears in the prenoon and midlatitude preliminary reverse impulse (PRI) appears in the postnoon, due to the remaining effect of the Hall current. However, violations of the Fukushima's theorem are also common such as in the cases of the equatorial PRI, the auroral electrojet, and the positive bay. The equatorial PRI caused by the Pedersen current appears both in the prenoon and postnoon regions. In the auroral region, the Hall current effect prevails over other currents so much and determines the AU/AL indices only from it regardless other currents. The midlatitude positive bay on the nightside is generated by the effect of the FAC. From these diverse reproduction of ground magnetic variations, a further verification is given for the global simulation in reproductions of the magnetosphere‐ionosphere coupling process.

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Section: Introductionmentioning

confidence: 90%

“…The fundamental role of convection is to form a pathway to transport, dissipate, and discharge stress caused by the solar wind‐magnetosphere interaction (Tanaka, Obara, et al, ). Stress is first converted to thermal energy through force balance.…”

Section: Substorm Disturbancesmentioning

confidence: 99%

Reproduction of Ground Magnetic Variations During the SC and the Substorm From the Global Simulation and Biot‐Savart's Law

et al. 2020

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“…The substorm is discussed in this paper as the convection transient which acts a core role in the M-I coupling by discharging stress generated through the solar wind-magnetosphere interaction (Tanaka et al, 2017a(Tanaka et al, , 2019a(Tanaka et al, , 2019b. Convection necessarily accompanies the dynamo that generate the FAC and Poynting flux (Ebihara & Tanaka, 2017;Tanaka et al, 2016).…”

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confidence: 99%

Formation and Release of the Harang Reversal Relating With the Substorm Onset Process

et al. 2021

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With the interplanetary magnetic field (IMF) that turns from northward to southward, the global simulation successively reproduces the growth phase, the onset, and the expansion phase of the substorm. The calculated ionospheric convection for the growth phase reproduces the development of the Harang reversal (HR), the upward field‐aligned current (FAC), and the upcoming onset point as observed. Magnetic field lines traced from the center of the nightside upward FAC are open, while the magnetic field line traced from the onset point is closed. These open magnetic field lines map to flow shear just outside the O/C boundary. Seen from the magnetic configuration, the growth phase proceeds as the replacement process of nulls. Two new nulls appear on the dayside under the southward IMF, while two old nulls under the northward IMF retreat tailward forming two bifurcation regions on the dawn and dusk flanks. Flow shear around the O/C boundary forms by magnetospheric convection that returns to the dayside via bifurcation regions. The expansion phase proceeds through a topological change by the near‐earth neutral line (NENL). The NENL occurs inside the thinned structure of the northward IMF remnant, on the low‐latitude side of the flow shear, and projects down to the low‐latitude edge of the upward FAC. Associated with the NENL, the convection return path changes to the center of the plasma sheet and reveals in the ionosphere as the release of the HR. By the shrinkage of projecting magnetic field line, the O/C boundary migrates poleward in the ionosphere.

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“…Principally, the origin of convection is the solar wind‐magnetosphere interaction, which causes a fraction of solar wind energy to penetrate into the magnetosphere. Overall, convection is the process to discharge this energy from the magnetosphere (Tanaka, Obara, et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

“…The former produces the FAC by converting motional energy to electromagnetic energy and the latter produces the FAC by converting internal energy to electromagnetic energy. In the cusp‐mantle dynamo, the slow‐mode motion acts to convert internal energy to electromagnetic energy (Tanaka et al., 2016; Watanabe et al., 2019), and the main discharging route of penetrated energy is downstream emission of plasma via the mantle (Tanaka, Obara, et al., 2019). Energy conversion is built into this path, causing the FAC and ionospheric convection.…”

Section: Introductionmentioning

confidence: 99%