Global profiles of compressional ultralow frequency wave power at geosynchronous orbit and their response to the solar wind

Sanny, Jeff; Judnick, Daniel; Moldwin, M. B.; Berube, D.; Sibeck, D. G.

doi:10.1029/2006ja012046

Cited by 8 publications

(15 citation statements)

References 33 publications

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“…ULF oscillations are of particular interest for their potential role in energizing the outer electron radiation belt through drift‐resonance interactions and through radial diffusion [ Elkington et al , 1999; Shprits et al , 2008]. During long intervals of fast wind the electron radiation belt is energized in particular [ Paulikas and Blake , 1979; Reeves et al , 2011] and the levels of ULF magnetic field oscillations inside the magnetosphere is seen to be high during those intervals [ Anderson et al , 1990; Sanny et al , 2007; Borovsky and Denton , 2010b]. This is also a time when the velocity shears in the solar wind are plentiful (cf.…”

Section: Discussionmentioning

confidence: 99%

The effect of sudden wind shear on the Earth's magnetosphere: Statistics of wind shear events and CCMC simulations of magnetotail disconnections

Borovsky

2012

J. Geophys. Res.

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[1] The solar wind is filled with strong current sheets and sudden velocity shears; often the two are co-located. Sudden velocity shears at 1 AU are statistically analyzed using ACE measurements from 1998 to 2008. The occurrence rates of passage and the orientations of the shear planes are examined. For shear layers with vector velocity changes |Dv| > 50 km/s, an average of $12 pass the Earth per day. In the fast wind, $60 sudden shear layers pass the Earth per day (about 2.5 per hour). To explore the effects of sudden wind shears on the Earth's magnetosphere, global magnetospheric MHD simulations with four different simulation codes are performed at the Community Coordinated Modeling Center (CCMC) with north-south and east-west wind shears. Windsock movement of the magnetotail is analyzed and comet-like disconnections of the magnetotail and magnetosheath are examined. Sudden changes in the cross-polar-cap potential and ionospheric Joule dissipation are seen as the shear layers pass the Earth. Other potential effects of sudden wind shear on the magnetosphere are discussed.

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Section: Discussionmentioning

confidence: 99%

The effect of sudden wind shear on the Earth's magnetosphere: Statistics of wind shear events and CCMC simulations of magnetotail disconnections

Borovsky

2012

J. Geophys. Res.

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“…Sanny et al . [] found that the IMF cone angle did not correlate significantly with compressional Pc5 wave power at geosynchronous orbit when compared with pristine solar wind pressure and flow speed correlations. The statistical results from these studies casts doubt on the importance (relative to other energy sources) of the ion foreshock as a driver of Pc5 ULF wave activity.…”

Section: Introductionmentioning

confidence: 95%

The role of transient ion foreshock phenomena in driving Pc5 ULF wave activity

et al. 2013

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[1] The ion foreshock is a source of energy for magnetospheric ULF waves, but it is usually only considered effective at driving ULF waves with frequencies above the Pc5 (2-7 mHz) range. We present observations for an 8 h high speed solar wind interval on 14 July 2008 during which three distinct types of transient ion foreshock phenomena (TIFP) were observed just upstream of the dayside bow shock. We demonstrate that TIFP generate global magnetospheric Pc5 ULF waves with amplitudes as large as 10 mV/m in the electric field and 10 nT in the magnetic field. We characterize the magnetospheric ULF response to several different TIFP that occur during this interval, including the first report of the ULF response to a foreshock bubble. Using a novel spacecraft configuration, we find that the local time with the highest Pc5 wave amplitude is closely related to the location of the ion foreshock. Statistical studies of Pc5 ULF wave activity, other case studies of ULF waves driven by processes in the ion foreshock, and recent theoretical and simulation work on TIFP place these results in context: TIFP are an important energy source for Pc5 ULF waves in the magnetosphere.

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“…Then the magnetic field data are filtered with the 150 s to 600 s band‐pass filter (ULF Pc5 wave frequency band), and we use the maximum value of the filtered magnetic field magnitude for the 12 h prior and 12 h after the zero epoch time for each event in the three categories (ICME, SIR, and Alfénic) to represent the amplitude of the ULF wave activity. Sanny et al [] found a local time dependence of ULF wave power, which varies by at most 1 order of magnitude during strong magnetic storms. However, the variation pattern of the ULF wave power shows to be a two‐cycle sinusoidal function, while the peaks of the two cycles (∼12 h interval) change by at most half an order (the wave amplitude change at most a quarter order).…”

Section: Methodsmentioning

confidence: 99%

Probabilistic forecasting analysis of geomagnetic indices for southward IMF events

Zhang

Moldwin

2015

Space Weather

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Geomagnetic disturbances that drive space weather impacts such as ground-induced currents and radiation belt enhancements are usually driven by strong southward interplanetary magnetic field (IMF) intervals. However, current heliospheric models either do not predict or provide low-accuracy forecasts of IMF B z . Here we examine the probability distribution function of geomagnetic activity indices for southward IMF intervals. We analyze the in situ plasma and magnetic field measurements long-duration large-amplitude southward IMF intervals (called B s events). The statistical profiles of other solar wind and IMF parameters show significant differences during the periods 1 day before the B s events for different solar wind transients (such as interplanetary coronal mass ejections and stream interaction regions). As is well known, we find that the solar wind speed is positively correlated with geomagnetic indices and that strong southward IMF is the key in storm triggering but not necessarily for substorms. We find that the solar wind density weakly affects geomagnetic field activity, but the response depends on the type of solar wind transient that includes the strong B s events. We also find that magnetospheric ultralow-frequency waves are induced by both strong southward IMF and solar wind dynamic pressure disturbances. We suggest that strong B s events could be predicted from the preceding characteristics of solar wind and IMF changes and that probabilistic forecasting of geomagnetic activity occurrence is potentially useful in space weather forecasting. We present preliminary analysis to demonstrate the out-of-sample ability to predict IMF B s events with in situ solar wind data.

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Global profiles of compressional ultralow frequency wave power at geosynchronous orbit and their response to the solar wind

Cited by 8 publications

References 33 publications

The effect of sudden wind shear on the Earth's magnetosphere: Statistics of wind shear events and CCMC simulations of magnetotail disconnections

The effect of sudden wind shear on the Earth's magnetosphere: Statistics of wind shear events and CCMC simulations of magnetotail disconnections

The role of transient ion foreshock phenomena in driving Pc5 ULF wave activity

Probabilistic forecasting analysis of geomagnetic indices for southward IMF events

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