A statistical study of BRIs (SMCs), isolated substorms, and individual sawtooth injections

DeJong, A. D.; Ridley, A. J.; Cai, X.; Clauer, C. R.

doi:10.1029/2008ja013870

Cited by 42 publications

(74 citation statements)

References 41 publications

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“…The SMC quartiles are much closer to the median velocity than the quartiles of other events. Similar steadiness was recently reported by (DeJong et al, 2009). Furthermore, the quartiles span a much larger range of velocities for sawtooth and storm-time events than they do for the isolated substorms and SMCs.…”

Section: Effect Of the Driving Solar Wind Electric Fieldsupporting

confidence: 86%

“…Steady magnetospheric convection (SMC (Sergeev et al, 1996)) events (also called convection bays (Pytte et al, 1978), continuous magnetospheric dissipation (CMD (Tanskanen et al, 2005)) events, or Balanced Reconnection Intervals (BRI (DeJong et al, 2009))) are periods during which the driving solar wind is steady and the ionospheric convection is enhanced but substorm activity is not observed (McPherron et al, 2005;Sergeev et al, 1996). The solar wind speed is typically rather low, and the magnitude of the interplanetary magnetic field (IMF) is moderate and stable.…”

Section: Introductionmentioning

confidence: 99%

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Different magnetospheric modes: solar wind driving and coupling efficiency

et al. 2009

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Abstract. This study describes a systematic statistical comparison of isolated non-storm substorms, steady magnetospheric convection (SMC) intervals and sawtooth events. The number of events is approximately the same in each group and the data are taken from about the same years to avoid biasing by different solar cycle phase. The very same superposed epoch analysis is performed for each event group to show the characteristics of ground-based indices (AL, PCN, PC potential), particle injection at the geostationary orbit and the solar wind and IMF parameters. We show that the monthly occurrence of sawtooth events and isolated non-stormtime substorms closely follows maxima of the geomagnetic activity at (or close to) the equinoxes. The most strongly solar wind driven event type, sawtooth events, is the least efficient in coupling the solar wind energy to the auroral ionosphere, while SMC periods are associated with the highest coupling ratio (AL/E Y ). Furthermore, solar wind speed seems to play a key role in determining the type of activity in the magnetosphere. Slow solar wind is capable of maintaining steady convection. During fast solar wind streams the magnetosphere responds with loading-unloading cycles, represented by substorms during moderately active conditions and sawtooth events (or other storm-time activations) during geomagnetically active conditions.

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Section: Effect Of the Driving Solar Wind Electric Fieldsupporting

confidence: 86%

Section: Introductionmentioning

confidence: 99%

Different magnetospheric modes: solar wind driving and coupling efficiency

et al. 2009

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“…We also find indications that the ionospheric convection pattern also remains fairly stable during SMC intervals and that the solar wind velocity was rather low for most of the SMC intervals of our dataset, generally below ∼ 400 km s −1 . The low solar wind velocity of SMCs was also found in several previous studies (O'Brien et al, 2002;DeJong et al, 2009;Huang et al, 2009;Partamies et al, 2009a, b). It is thought to be related to the lower reconnection electric field of the slower solar wind and with specific internal properties of the magnetosphere possibly regarding magnetotail convection, but a full understanding of the mechanism is still needed.…”

Section: Properties Of Smcssupporting

confidence: 84%

“…The behaviour of such a complex coupled system comprising the solar wind, the magnetosphere and the ionosphere can obviously not be reduced to just a few numbers, even though the amount of open magnetic flux and the reconnection rates are among the most important ones. This mode classification should not hide the key role of the solar wind properties in the dynamics of the magnetosphere, as has been statistically studied by DeJong et al (2009), who highlighted the importance of the IMF B z component and of the solar wind velocity, temperature and Mach number (which control the dayside reconnection rate in large measure). For example, the importance of having a low solar wind velocity for the development of the SMC mode does not appear in the present analysis.…”

Section: Intercomparison Of Magnetospheric Convection Modesmentioning

confidence: 97%

Magnetic reconnection during steady magnetospheric convection and other magnetospheric modes

Hubert¹,

Gérard²,

Milan

et al. 2017

Ann. Geophys.

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Abstract. We use remote sensing of the proton aurora with the IMAGE-FUV SI12 (Imager for Magnetopause to Aurora Global Exploration-Far Ultraviolet-Spectrographic Imaging at 121.8 nm) instrument and radar measurements of the ionospheric convection from the SuperDARN (Super Dual Aurora Radar Network) facility to estimate the open magnetic flux in the Earth's magnetosphere and the reconnection rates at the dayside magnetopause and in the magnetotail during intervals of steady magnetospheric convection (SMC). We find that SMC intervals occur with relatively high open magnetic flux (average ∼ 0.745 GWb, standard deviation ∼ 0.16 GWb), which is often found to be nearly steady, when the magnetic flux opening and closure rates approximately balance around 55 kV on average, with a standard deviation of 21 kV. We find that the residence timescale of open magnetic flux, defined as the ratio between the open magnetospheric flux and the flux closure rate, is roughly 4 h during SMCs. Interestingly, this number is approximately what can be deduced from the discussion of the length of the tail published by Dungey (1965), assuming a solar wind speed of ∼ 450 km s −1 . We also infer an enhanced convection velocity in the tail, driving open magnetic flux to the nightside reconnection site. We compare our results with previously published studies in order to identify different magnetospheric modes. These are ordered by increasing open magnetic flux and reconnection rate as quiet conditions, SMCs, substorms (with an important overlap between these last two) and sawtooth intervals.

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“…Although there is sporadic activity that emerges intermittently in both the inner magnetosphere and the plasma sheet, the large-scale configuration of the magnetosphere is fairly stable [Sergeev et al, 1996, and references therein]. Statistical results have shown that solar wind speed may play an important role in modulating isolated substorms, sawtooth events and SMCs, but those results are mainly focusing on solar wind-magnetosphere coupling [Partamies et al, 2009;DeJong et al, 2009]. Global MHD simulations have made progress in modeling SMCs as suggested by Raeder et al [2008] that almost all of them tend to produce SMC-like state during steady southward IMF.…”

Section: Introductionmentioning

confidence: 99%

Role of depleted flux tubes in steady magnetospheric convection: Results of RCM‐E simulations

2010

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[1] We present results of a simulation of an idealized steady magnetospheric convection (SMC) event during steady southward IMF B Z using a version of the Rice Convection Model that is coupled to an equilibrium magnetic field solver (RCM-E) and compare that to a simulation of a substorm growth phase. In contrast to the 1-hour growth phase, the 5-hour SMC event is modeled by placing a plasma distribution with substantially depleted entropy parameter PV 5/3 on the RCM's high-latitude boundary. We find that the modeled largescale configuration on the nightside during the SMC event differs significantly from the growth phase simulation. First, in the magnetotail tailward of X ≈ −10 R E , the magnetic field is dipole-like associated with thick plasma sheet. Second, near geosynchronous orbit, the magnetic field is more stretched associated with the strongly enhanced partial ring current and the inner edge of the plasma sheet moves well inside geosynchronous orbit. Third, the electric field shows strong shielding or even overshielding during the SMC; while a penetration electric field emerges in the growth phase simulation. Fourth, the ground magnetogram calculation shows large horizontal magnetic field disturbances in a much thicker auroral zone which is mainly attributed to Hall currents. Meantime, fairly negative magnetic disturbance emerges in the mid and low latitudes which is mainly attributed to the partial ring current approximately extended to terminators. Contrary to previous studies, our simulation does not produce a deep B Z minimum during strong magnetospheric convection, which implies that the pressure balance inconsistency may be dramatically alleviated if the inner magnetosphere is continuously fed with under-populated flux tubes. We also suggest that strong magnetic field without B Z minimum in the plasma sheet may explain why SMCs can last for hours without a substorm expansion since certain instabilities may not build up to threshold in such a configuration.

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A statistical study of BRIs (SMCs), isolated substorms, and individual sawtooth injections

Cited by 42 publications

References 41 publications

Different magnetospheric modes: solar wind driving and coupling efficiency

Different magnetospheric modes: solar wind driving and coupling efficiency

Magnetic reconnection during steady magnetospheric convection and other magnetospheric modes

Role of depleted flux tubes in steady magnetospheric convection: Results of RCM‐E simulations

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