Magnetospheric impulse response for many levels of geomagnetic activity

Bargatze, L. F.; Baker, D. N.; McPherron, R. L.; Hones, E. W.

doi:10.1029/ja090ia07p06387

Cited by 372 publications

(334 citation statements)

References 30 publications

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“…(13) in the following manner. The majority of the bursty events in the near-Earth magnetospheric tail with clear signatures in high-latitude observatory time series appear due to the energy and mass accumulation-release processes (loading±unload-ing cycle) on time scales larger than 20 (min) (Bargatze et al, 1985) while the sampling interval of Thule data is 1 (min). On the other hand, no bursty energy release is expected on the time scales of <20 (min).…”

Section: Discussionmentioning

confidence: 99%

“…Equation (14) brings into connection the weighted inputs preceding the output by time lag j Á dt. Bargatze et al (1985) have analyzed the magnetospheric impulse response for many levels of geomagnetic activity using the solar wind V Á B s (V ± solar wind speed, B s the southward component of the magnetic ®eld) as the input data, and the magnetospheric AL index as the output data. Two peaks in impulse response were identi®ed.…”

Section: Discussionmentioning

confidence: 99%

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On multifractality of high-latitude geomagnetic fluctuations

Vörös

2000

Ann. Geophys.

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Abstract. In order to contribute to the understanding of solar wind±magnetosphere interactions the multifractal scaling properties of high-latitude geomagnetic uctuations observed at the Thule observatory have been studied. Using the local observatory data and the present experimental knowledge only it seems hard to characterize directly the, presumably intermittent, mesoscale energy accumulation and dissipation processes taking place at the magnetotail, auroral region, etc. Instead a positive probability measure, describing the accumulated local geomagnetic signal energy content at the given time scales has been introduced and its scaling properties have been studied. There is evidence for the multifractal nature of the so de®ned intermittent ®eld , a result obtained by using the recently introduced technique of large deviation multifractal spectra. This technique allows us to describe the geomagnetic¯uctuations locally in time by means of singularity exponents a, which represent a generalization of the local degree of di erentiability and characterize the power-law scaling dependence of the introduced measure on resolution. A global description of the geomagnetic¯uctuations is insured by the spectrum of exponents f a which represents a rate function quantifying the deviations of the observed singularities a from the expected value. The results show that there exists a multifractal counterpart of the previously reported spectral break and di erent types of f a spectra describe thē uctuations in direct dissipation or loading-unloading regimes of the solar wind±magnetosphere interaction. On the time scale of substorms and storms the multifractal structure of the loading±unloading mode¯uc-tuations seems to be analogous to the simple multiplicative P-model, while the f a spectra in direct dissipation regime are close but not equal to the features of a uniform distribution. Larger deviations from the multiplicative model are observed when the in¯uence of the solar wind¯uctuations is examined. On this basis it is expected that an extended multifractal analysis of the singularity structure of nearEarth plasma system¯uctuations would lead to improved geomagnetic diagnosis of the magnetospheric dynamics.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

On multifractality of high-latitude geomagnetic fluctuations

Vörös

2000

Ann. Geophys.

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“…For example, substorms at Earth are known to exhibit both "driven" responses that can be predicted using linear "filters" and knowledge of the upstream solar wind and IMF (Bargatze et al, 1985) and an unpredictable, "spontaneous" component related to the magnetic energy stored in the lobes. Lacking a conductive ionosphere, it may be that Mercury's magnetosphere cannot store significant amounts of energy and the spontaneous component of substorm energy dissipation will be small or absent (Luhmann et al, 1998).…”

Section: How Will Substorm Activity Be Identified In the Messenger Mementioning

confidence: 99%

MESSENGER: Exploring Mercury’s Magnetosphere

et al. 2007

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Abstract. The MESSENGER mission to Mercury offers our first opportunity to explore this planet's miniature magnetosphere since the brief flybys of Mariner 10. Mercury's magnetosphere is unique in many respects. The magnetosphere of Mercury is among the smallest in the solar system; its magnetic field typically stands off the solar wind only -1000 to 2000 km above the surface. For this reason there are no closed drift paths for energetic particles and, hence, no radiation belts. The characteristic time scales for wave propagation and convective transport are short and kinetic and fluid modes may be coupled. Magnetic reconnection at the dayside magnetopause may erode the subsolar magnetosphere allowing solar wind ions to impact directly the regolith. Inductive currents in Mercury's interior may act to modify the solar wind interaction by resisting changes due to solar wind pressure variations. Indeed, observations of these induction effects may be an important source of information on the state of Mercury's interior. In addition, Mercury's magnetosphere is the only one with its defining magnetic flux tubes rooted in a planetary regolith as opposed to an atmosphere with a conductive ionospheric layer. This lack of an ionosphere is probably the underlying reason for the brevity of the very intense, but short-lived, -1-2 min, substorm-like energetic particle events observed by Mariner 10 during its first traversal of Mercury's magnetic tail. Because of Mercury's proximity to the sun, 0.3 -0.5 AU, this magnetosphere experiences the most extreme driving forces in the solar system. All of these factors are expected to produce complicated interactions involving the exchange and re-cycling of neutrals and ions between the solar wind, magnetosphere, and regolith. The electrodynamics of Mercury's magnetosphere are expected to be equally complex, with strong forcing by the solar wind, magnetic reconnection at the magnetopause and in the tail, and the pick-up of planetary ions all driving field-aligned electric currents.However, these field-aligned currents do not close in an ionosphere, but in some other manner. In addition to the insights-into magnetospheric physics offered by study of the solar wind -Mercury system, quantitative specification of the "external" magnetic field generated by magnetospheric currents is necessary for accurate determination of the strength and multi-polar decomposition of Mercury's intrinsic magnetic field.MESSENGER'S highly capable instrumentation and broad orbital coverage will greatly advance our understanding of both the origin of Mercury's magnetic field and the acceleration of charged particles in small magnetospheres. In. this article, we review what is known about Mercury's magnetosphere and describe the MESSENGER science team's strategy for obtaining answers to the outstanding science questions surrounding the interaction of the solar wind with Mercury and its small, but dynamic, magnetosphere.2

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“…The relations can be highly complicated, particularly during substorms when the magnetospheric response to the solar wind contain a dominating nonlinear component [Bargatze et al, 1985 …”

Section: Introductionmentioning

confidence: 99%