Sudden impulses at geosynchronous orbit and at ground

Villante, U.; Piersanti, Mirko

doi:10.1016/j.jastp.2010.01.008

Cited by 26 publications

(34 citation statements)

References 51 publications

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“…Borodkova et al (2005Borodkova et al ( , 2006 found that, in general, the changes of the SW pressure (positive and negative) were associated with corresponding variations of the magnetospheric field; they also remarked that all the events without an explicit response were located either before 7:30 LT or after 16:30 LT. Wang et al (2007) confirmed that the field variation peaked near local noon and decreased toward dawn and dusk. Figure 2a (after Villante and Piersanti, 2011) compares the amplitude of the geostationary response for events simultaneously detected at different LT: it clearly confirms a large data spread of the relative response in any time sector, together with an explicit LT modulation, with greater values at satellite located closer to the noon meridian; as can be seen, negligible and even negative magnetospheric responses are often detected in the dark sector.…”

Section: The General Aspects and The Local Time Dependencesupporting

confidence: 52%

“…The occurrence of negligible and negative responses makes the average values smaller than predicted in the dark region. It is worth noting, however, that, even in this region, the positive B z often show a substantial correspondence with the values predicted for the magnetopause current, especially for higher SW pressure jumps (Villante and Piersanti, 2011): it suggests that the dominant effects of the magnetopause current (i.e. the magnetospheric compression) might extend to a significant portion of the dark magnetosphere.…”

Section: The Role Of the Sw Parametersmentioning

confidence: 68%

“…Figure 1 (after Villante and Piersanti, 2011) shows the aspects of the SI manifestation at different LT (LT being the local time) along the geosynchronous orbit and the relationship between the magnetospheric field change (B, B being the total field) and the increase of the Villante and Piersanti, 2011). Three examples of SI events at geosynchronous orbit.…”

Section: The General Aspects and The Local Time Dependencementioning

confidence: 99%

“…On the other hand, the occurrence of negative variations in the nightside region (unpredictable in terms of the magnetopause current alone, solid line in Figure 2b) reveals, in several cases, a significant role of additional current systems. The interpretation of such events, however, requests a case by case analysis, paying attention to the SW and magnetospheric conditions in the period of interest (Villante and Piersanti, 2011). As a matter of facts, several approaches have been adopted to interpret the characteristics of the SI manifestation in the dark magnetosphere.…”

Section: The Role Of the Sw Parametersmentioning

confidence: 99%

“…Here, the H behaviour becomes more step-like, but a two pulse structure with reduced amplitude is still identified. Figure 4 (after Villante and Piersanti, 2011) compares the aspects of ground events at 36° (being the magnetic latitudewith the SW and geosynchronous observations. It confirms that, independently on LT, the low latitude response of the H component often consists of a simple monotonic increase with amplitude (H) often comparable (although smaller) with the field jump observed at geosynchronous orbit.…”

Section: The General Aspects and The Local Time Dependencementioning

confidence: 99%

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Sudden Impulses in the Magnetosphere and at Ground

Villante¹,

Piersanti²

2012

Exploring the Solar Wind

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Section: The General Aspects and The Local Time Dependencesupporting

confidence: 52%

Section: The Role Of the Sw Parametersmentioning

confidence: 68%

Section: The General Aspects and The Local Time Dependencementioning

confidence: 99%

Section: The Role Of the Sw Parametersmentioning

confidence: 99%

Section: The General Aspects and The Local Time Dependencementioning

confidence: 99%

See 3 more Smart Citations

Sudden Impulses in the Magnetosphere and at Ground

Villante¹,

Piersanti²

2012

Exploring the Solar Wind

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Sudden impulse observations in the dayside magnetosphere by THEMIS

et al. 2014

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We present a study of the magnetospheric response to interplanetary shocks. We show eight events with simultaneous observations of sudden impulses in the dayside magnetosphere and interplanetary shocks in the solar wind. The spacecraft measurements in the equatorial plane, even those very close to the Earth, can be interpreted in terms of the vortices predicted by previous studies employing global MHD models. In fact, these vortices are velocity oscillations with the properties of Alfvén waves. The amplitude and frequency of the oscillations depend on radial distance from the Earth. The amplitude of the velocity perturbations decreases with increase of the density and magnetic field magnitude, but the velocity amplitude shows no dependence on magnitude of the solar wind dynamic pressure change attending the interplanetary shocks. The oscillations are observed both in the outer magnetosphere and the plasmasphere, but they become less sinusoidal near the plasmapause, i.e., in the region with a large-density gradient. The amplitude of the magnetic field enhancement in the sudden impulses also depends on the radial distance. The MHD simulations successfully predict the amplitudes of magnetic field increase and the first cycles of the velocity oscillations in these events.

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Conjugate observations of traveling convection vortices associated with transient events at the magnetopause

et al. 2015

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Traveling convection vortices (TCVs) are generally produced by field-aligned currents (FACs) at high latitudes associated with transient changes of the magnetopause. This paper presents multipoint conjugate observations of transient events at the magnetopause measured in space and on the ground. The transient events showing radial fluctuation of the magnetopause in association with sudden increases in solar wind dynamic pressure were detected by both the Time History of Events and Macroscale Interactions during Substorms and the Geostationary Operational Environmental Satellite spacecraft. Geomagnetic signatures seen as TCVs in response to the transient events were observed by the ground magnetometer array in Greenland and Canada and their conjugate locations in Antarctica including recently developed Antarctic magnetometers, mostly located along the 40 • magnetic meridian. This new conjugate network provides a unique opportunity to observe geomagnetic field signatures over a relatively large region in both hemispheres. This study focuses mainly on the spatial and temporal features of the TCVs in the conjugate hemispheres in relation to the transient events at the magnetopause. The TCV events are characterized by their single or twin vortex, of which the centers are located approximately at 72 • -76 • magnetic latitude, propagating either dawnward or duskward away from local noon. While interhemispheric conjugacy is expected with an assumption that TCV signatures are created by FACs directed in both hemispheres, our observations suggest that there might be more complex mechanisms contributing the asymmetrical features, perhaps due to field line mapping and/or conductivity differences.

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Sudden impulses at geosynchronous orbit and at ground

Cited by 26 publications

References 51 publications

Sudden Impulses in the Magnetosphere and at Ground

Sudden Impulses in the Magnetosphere and at Ground

Sudden impulse observations in the dayside magnetosphere by THEMIS

Conjugate observations of traveling convection vortices associated with transient events at the magnetopause

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