Data-based modelling of the Earth's dynamic magnetosphere: a review

Tsyganenko, N. A.

doi:10.5194/angeo-31-1745-2013

Cited by 81 publications

(124 citation statements)

References 103 publications

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“…Our result of the substorm triggered by a solar wind dynamic pressure enhancement is consistent with the previous results of Petrinec and Russell (1996) and Shue and Kamide (1998) finding that solar wind density variations during periods of southward IMF can trigger substorms. Likewise, there is evidence for the triggering of tail reconnection by sudden enhancements in solar wind dynamic pressure (see, e.g., Milan et al (2007) and references therein).…”

Section: Discussionsupporting

confidence: 93%

“…The second response is associated with slower processes such as magnetopause merging, plasma convection, particle losses due to pitch angle diffusion, charge exchange etc." (Tsyganenko, 2013). According to Lyons et al (2005), a P dyn enhancement under strongly southward interplanetary magnetic field (IMF) conditions "is found to cause both compressive auroral brightening away from the bulge region and a Harang-region substorm auroral brightening" -leading to a very broad auroral enhancement covering ∼ 10-15 h of MLT.…”

Section: P E Sandholt Et Al: the 25 July 2004 Interplanetary Cme Casementioning

confidence: 99%

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Transitions between states of magnetotail–ionosphere coupling and the role of solar wind dynamic pressure: the 25 July 2004 interplanetary CME case

2015

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Abstract. In a case study, we investigate transitions between fundamental magnetosphere-ionosphere (M-I) coupling modes during storm-time conditions (SYM-H between −100 and −160 nT) driven by an interplanetary coronal mass ejection (ICME). We combine observations from the near tail, at geostationary altitude (GOES-10), and electrojet activities across the auroral oval at postnoon-to-dusk and midnight. After an interval of strong westward electrojet (WEJ) activity, a 3 h long state of attenuated/quenched WEJ activity was initiated by abrupt drops in the solar wind density and dynamic pressure. The attenuated substorm activity consisted of brief phases of magnetic field perturbation and electron flux decrease at GOES-10 near midnight and moderately strong conjugate events of WEJ enhancements at the southern boundary of the oval, as well as a series of very strong eastward electrojet (EEJ) events at dusk, during a phase of enhanced ring current evolution, i.e., enhanced SYM-H deflection within −120 to −150 nT. Each of these M-I coupling events was preceded by poleward boundary intensifications and auroral streamers at higher oval latitudes. We identify this mode of attenuated substorm activity as being due to a magnetotail state characterized by bursty reconnection and bursty bulk flows/dipolarization fronts (multiple current wedgelets) with associated injection dynamo in the near tail, in their braking phase. The latter process is associated with activations of the Bostrøm type II (meridional) current system. A transition to the next state of M-I coupling, when a full substorm expansion took place, was triggered by an abrupt increase of the ICME dynamic pressure from 1 to 5 nPa. The brief field deflection events at GOES-10 were then replaced by a 20 min long interval of extreme field stretching (B z approaching 5 nT and B x ≈ 100 nT) followed by a major dipolarization ( B z ≈ 100 nT). In the ionosphere the latter stage appeared as a "full-size" stepwise poleward expansion of the WEJ. It thus appears that the ICME passage led to fundamentally different M-I coupling states corresponding to different levels of dynamic pressure (P dyn ) under otherwise very similar ICME conditions. Full WEJ activity, covering a wide latitude range across the auroral oval in the midnight sector, was attenuated by the abrupt dynamic pressure decrease and resumed after the subsequent abrupt increase.

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Section: Discussionsupporting

confidence: 93%

Section: P E Sandholt Et Al: the 25 July 2004 Interplanetary Cme Casementioning

confidence: 99%

Transitions between states of magnetotail–ionosphere coupling and the role of solar wind dynamic pressure: the 25 July 2004 interplanetary CME case

2015

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“…Therefore, we cannot exclude that, in our case, the more intense and spread FAC effect overwhelms that of the temporally more localised B y leakage. Let us finally recall that some empirical magnetospheric models include the phenomenon of IMF penetration (Tsyganenko 2013). Concerning the relation of dH residuals and Sym-H index we have found that residuals seem to be strongly affected by the effect of the partial ring current in accordance with previous results (e.g.…”

Section: Discussionsupporting

confidence: 90%

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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“…The mainstream of models for the static part of B, due to the Tsyganenko algorithms T89, T96 and TS05 (see Tsyganenko, 2013, and references therein), follows a data-based approach towards correlation with parameters of geomagnetic activity like P dyn , the IMF vector B, the planetary index Kp and the disturbance storm-time index Dst (Rostoker, 1972). In T89, a physics-based description of the magnetospheric currents and the corresponding vector potential was introduced; the T96 model improved T89 in the description of the magnetopause geometry and the equatorial tail physics, whereas TS05 upgraded T96 with the inclusion of storm and substorm dynamics.…”

Section: Geomagnetic Fieldmentioning

confidence: 99%

“…An advantage of studying the individual particle motions is the physics insight gained, as well as the statistics built from ensembles of particles. In such models, the Lorentz equation of motion is solved, either in its full form or reduced in terms of the guiding-center approximation, and the driving forces are (as above) the dynamic magnetic field coming from the superposition of the Earth's terrestrial magnet with the fields generated by the magnetospheric current sources (Tsyganenko, 2013), and the electric field due to large-scale plasma convection and corotation with the Earth (Volland, 1973). An important factor, however, is the modeling of the electric field component induced by the time variation in the magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Modeling of ion dynamics in the inner geospace during enhanced magnetospheric activity

Tsironis

Anastasiadis

Katsavrias³

et al. 2016

Ann. Geophys.

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Abstract.We investigate the effect of magnetic disturbances on the ring current buildup and the dynamics of the current systems in the inner geospace by means of numerical simulations of ion orbits during enhanced magnetospheric activity. For this purpose, we developed a particle-tracing model that solves for the ion motion in a dynamic geomagnetic field and an electric field due to convection, corotation and Faraday induction and which mimics reconfigurations typical to such events. The kinematic data of the test particles is used for analyzing the dependence of the system on the initial conditions, as well as for mapping the different ion species to the magnetospheric currents. Furthermore, an estimation of Dst is given in terms of the ensemble-averaged ring and tail currents. The presented model may serve as a tool in a Sunto-Earth modeling chain of major solar eruptions, providing an estimation of the inner geospace response.

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Data-based modelling of the Earth's dynamic magnetosphere: a review

Cited by 81 publications

References 103 publications

Transitions between states of magnetotail–ionosphere coupling and the role of solar wind dynamic pressure: the 25 July 2004 interplanetary CME case

Transitions between states of magnetotail–ionosphere coupling and the role of solar wind dynamic pressure: the 25 July 2004 interplanetary CME case

Unmodelled magnetic contributions in satellite-based models

Modeling of ion dynamics in the inner geospace during enhanced magnetospheric activity

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