Magnetospheric energy budget during huge geomagnetic activity using Cluster and ground‐based data

Rosenqvist, L.; Buchert, Stephan; Opgenoorth, H. J.; Vaivads, A.; Lu, G.

doi:10.1029/2006ja011608

Cited by 32 publications

(50 citation statements)

References 48 publications

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“…They found that in the simulation, the dayside load indeed appears adjacent to the reconnection region, while the generators are located behind the cusps in the tail lobes. Rosenqvist et al (2006) presented a method to investigate energy conversion using Cluster observations, and later the method was applied to both the load and generator cases (Rosenqvist et al, 2008). The most recent step using this methodology was to characterize the load-generator process systematically in a small data set using Cluster observations .…”

Section: Palmroth Et Al: Imf B Y and Tilt Dependence Of Energy Trmentioning

confidence: 99%

Magnetopause energy transfer dependence on the interplanetary magnetic field and the Earth's magnetic dipole axis orientation

2012

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Abstract. We examine the spatial variation of magnetospheric energy transfer using a global magnetohydrodynamic (MHD) simulation (GUMICS-4) and a large data set of flux transfer events (FTEs) observed by the Cluster spacecraft. Our main purpose is to investigate whether it is possible to validate previous results on the spatial energy transfer variation from the GUMICS-4 simulation using the statistical occurrence of FTEs, which are manifestations of magnetospheric energy transfer. Previous simulation results have suggested that the energy transfer pattern at the magnetopause rotates according to the interplanetary magnetic field (IMF) orientation, and here we investigate whether a similar rotation is seen in the locations at which FTE signatures are observed. We find that there is qualitative agreement between the simulation and observed statistics, as the peaks in both distributions rotate as a function of the IMF clock angle. However, it is necessary to take into account the modulation of the statistical distribution that is caused by a bias towards in situ FTE signatures being observed in the winter hemisphere (an effect that has previously been predicted and observed in this data set). Taking this seasonal effect into account, the FTE locations support the previous simulation results and confirm the earlier prediction that the energy transfers in the plane of the IMF. In addition, we investigate the effect of the dipole orientation (both the dipole tilt angle and its orientation in the plane perpendicular to the solar wind flow) on the energy transfer spatial distribution. We find that the energy transfer occurs mainly in the summer hemisphere, and that the dayside reconnection region is located asymmetrically about the subsolar position. Finally, we find that the energy transfer is 10 % larger at equinox conditions than at solstice, contributing to the discussion concerning the semiannual variation of magnetospheric dynamics (known as "the Russell-McPherron effect").

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Section: Palmroth Et Al: Imf B Y and Tilt Dependence Of Energy Trmentioning

confidence: 99%

Magnetopause energy transfer dependence on the interplanetary magnetic field and the Earth's magnetic dipole axis orientation

2012

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“…To our knowledge, the first experimental investigations of generator regions in the plasma sheet were presented in Marghitu et al (2006); Hamrin et al (2006). During a very strong geomagnetic activity a clear generator was identified at the magnetopause flank of the tail (Rosenqvist et al, 2006). The generators were identified as concentrated regions with negative power densities as obtained by Cluster.…”

Section: Introductionmentioning

confidence: 99%

Occurrence and location of concentrated load and generator regions observed by Cluster in the plasma sheet

et al. 2009

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Abstract.Here, and in a companion paper by Hamrin et al. (2009) [Scale size and life time of energy conversion regions observed by Cluster in the plasma sheet], we investigate localized energy conversion regions (ECRs) in the Earth's plasma sheet. In total we have studied 151 ECRs within 660 h of plasma sheet data from the summer and fall of 2001 when Cluster was close to apogee at an altitude of about 15-20 R E . Cluster offers appropriate conditions for the investigation of energy conversion by the evaluation of the power density, E·J , where E is the electric field and J the current density. From the sign of the power density, we have identified more than three times as many Concentrated Load Regions (CLRs) as Concentrated Generator Regions (CGRs). We also note that the CLRs appear to be stronger. To our knowledge, these are the first in situ observations confirming the general notion of the plasma sheet, on the average, behaving as a load. At the same time the plasma sheet appears to be highly structured, with energy conversion occurring in both directions between the fields and the particles. From our data we also find that the CLRs appear to be located closer to the neutral sheet, while CGRs prefer locations towards the plasma sheet boundary layer (PSBL). For both CLRs and CGRs, E and J in the GSM y (cross-tail) direction dominate the total power density, even though the z contribution occasionally can be significant. The prevalence of the y-direction seems to be weaker for the CGRs, possibly related to a higher fluctuation level near the PSBL.

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“…A popular notion is hence that the aurora is powered by the solar wind. Indeed, an open magnetopause at a few R E tailward of the dawndusk meridian has been observed to act like a generator with a significant component of the magnetic tension directed against the solar wind flow, thus producing Poynting flux pointing into the magnetotail [Rosenqvist et al, 2006]. According to Rosenqvist et al [2006], estimates of the global Joule heating in the Earth's upper atmosphere and ionosphere during an intense storm amounted to roughly 35% of the power extracted from the solar wind at the magnetopause.…”

Section: Introductionmentioning

confidence: 99%

“…Indeed, an open magnetopause at a few R E tailward of the dawndusk meridian has been observed to act like a generator with a significant component of the magnetic tension directed against the solar wind flow, thus producing Poynting flux pointing into the magnetotail [Rosenqvist et al, 2006]. According to Rosenqvist et al [2006], estimates of the global Joule heating in the Earth's upper atmosphere and ionosphere during an intense storm amounted to roughly 35% of the power extracted from the solar wind at the magnetopause. However, under normal circumstances we can expect that a considerable fraction of the electromagnetic power dissipated in the ionosphere is not directly generated at the magnetopause, since nightside auroral field lines on the equatorward edge of the oval, and at least up into the central part, map from the ionosphere rather into the tail region (specifically the plasma sheet).…”

Section: Introductionmentioning

confidence: 99%

Energy conversion regions as observed by Cluster in the plasma sheet

et al. 2011

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[1] In this article we present a review of recent studies of observations of localized energy conversion regions (ECRs) observed by Cluster in the plasma sheet at altitudes of 15-20R E . By examining variations in the power density, E · J, where E is the electric field and J is the current density, we show that the plasma sheet exhibits a high level of fine structure. Approximately three times as many concentrated load regions (CLRs) (E · J > 0) as concentrated generator regions (CGRs) (E · J < 0) are identified, confirming the average load character of the plasma sheet. Some ECRs are found to relate to auroral activity. While ECRs are relevant for the energy conversion between the electromagnetic field and the particles, bursty bulk flows (BBFs) play a central role for the energy transfer in the plasma sheet. We show that ECRs and BBFs are likely to be related, although details of this relationship are yet to be explored. The plasma sheet energy conversion increases rather simultaneously with increasing geomagnetic activity in both CLRs and CGRs. Consistent with large-scale magnetotail simulations, most of the observed ECRs appear to be rather stationary in space but varying in time. We estimate that the ECR lifetime and scale size are a few minutes and a few R E , respectively. It is conceivable that ECRs rise and vanish locally in significant regions of the plasma sheet, possibly oscillating between load and generator character, while some energy is transmitted as Poynting flux to the ionosphere.

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Magnetospheric energy budget during huge geomagnetic activity using Cluster and ground‐based data

Cited by 32 publications

References 48 publications

Magnetopause energy transfer dependence on the interplanetary magnetic field and the Earth's magnetic dipole axis orientation

Magnetopause energy transfer dependence on the interplanetary magnetic field and the Earth's magnetic dipole axis orientation

Occurrence and location of concentrated load and generator regions observed by Cluster in the plasma sheet

Energy conversion regions as observed by Cluster in the plasma sheet

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