Observations of solar wind directly driven auroral electrojets and gravity waves

Huang, Chao-Song; André, D.; Sofko, G. J.

doi:10.1029/98ja02297

Cited by 11 publications

(3 citation statements)

References 26 publications

(22 reference statements)

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“…Some earlier studies, focusing at higher magnetic latitudes, have suggested a close causal relationship between solar wind‐magnetosphere‐ionosphere (SW‐M‐I) coupling and MSTID occurrence [e.g,. Huang et al , ; Sofko and Huang , ]. Samson et al [] suggested that MSTIDs at high latitudes were likely to be related to Earth‐reflected AGW produced by Lorentz forcing or Joule heating of the atmosphere.…”

Section: Discussionmentioning

confidence: 99%

Characteristics of medium‐scale traveling ionospheric disturbances observed near the Antarctic Peninsula by HF radar

et al. 2013

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[1] We present a survey of medium-scale traveling ionospheric disturbances (MSTIDs) observed by a Super Dual Auroral Radar Network HF radar located in the Falkland Islands between May 2010 and April 2011. The radar has a field of view that overlooks the Antarctic Peninsula, a known hot spot of gravity wave activity. We present observations of radar ground-backscatter data, in which the signatures of MSTIDs are manifested as structured enhancements in echo power. Observed periods were in the range 30-80 min, corresponding to frequencies of 0.2-0.6 mHz. Wavelengths were generally in the range 200-800 km and phase speeds in the range 100-300 m s -1 . These values are within the ranges typically associated with medium-scale gravity waves. We find a primary population of northward (equatorward) propagating MSTIDs, which demonstrate an association with enhanced solar wind-magnetosphere coupling and a smaller, westward propagating population, that could be associated with atmospheric gravity waves excited by winds over the Andean and Antarctic Peninsula mountains or by the high winds of the Antarctic Polar Vortex.

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Section: Discussionmentioning

confidence: 99%

Characteristics of medium‐scale traveling ionospheric disturbances observed near the Antarctic Peninsula by HF radar

et al. 2013

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“…If there are gravity waves generated in the auroral zone, the Super Dual Auroral Radar Network (SuperDARN) should be able to register the wave signature. In particular, Huang et al [1998] reported that quasiperiodic southward turnings of the IMF could result in a series of gravity wave pulses in the dayside high‐latitude ionosphere, and Huang et al [2000] found that the high‐latitude gravity waves may be related to internal magnetospheric oscillations during northward IMF. However, we checked the SuperDARN data in the present cases and did not find periodic gravity wave signatures at high latitudes poleward of Millstone Hill.…”

Section: Discussionmentioning

confidence: 99%

Effects of solar wind variations on the midlatitude ionosphere

2002

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[1] It is known that the solar wind has significant effect on the magnetospheric convection and that magnetospheric electric fields can penetrate into the midlatitude and low-latitude ionosphere. In this paper, we present observations of midlatitude ionospheric plasma perturbations during two events. In one event, the interplanetary magnetic field (IMF) oscillated between southward and northward with a period of $2 hours, while the solar wind pressure was relatively stable. In the other event the solar wind dynamic pressure oscillated with a period of $1 hour, while the IMF remained strongly northward and stable. In both events the Millstone Hill incoherent scatter radar detected quasiperiodic perturbations in all F region plasma parameters (electron density, ion velocity, electron temperature, and ion temperature) in the midlatitude dayside ionosphere. The midlatitude ionospheric perturbations were well correlated with the IMF or solar wind pressure variations. Near the F peak altitude the electron density could be increased or decreased by $30% within 30-70 min. We suggest that the midlatitude ionospheric electron density perturbations were caused by the penetration of magnetospheric electric fields which were controlled or modulated by the oscillations in the IMF or solar wind pressure.

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“…With respect to point (ii), for example, several authors have shown that fluctuations in the IMF appear to drive Pc6/Pc7 band oscillations in the magnetosphere and ionosphere [e.g., Huang et al , ; Stephenson and Walker , ; Walker , ]. Kepko et al [] also showed observations that suggested that such oscillations can also be driven by solar wind density structures.…”

Section: Discussionmentioning

confidence: 99%

Rethinking the polar cap: Eccentric dipole structuring of ULF power at the highest corrected geomagnetic latitudes

et al. 2016

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The day‐to‐day evolution and statistical features of Pc3‐Pc7 band ultralow frequency (ULF) power throughout the southern polar cap suggest that the corrected geomagnetic (CGM) coordinates do not adequately organize the observed hydromagnetic spatial structure. It is shown that that the local‐time distribution of ULF power at sites along CGM latitudinal parallels exhibit fundamental differences and that the CGM latitude of a site in general is not indicative of the site's projection into the magnetosphere. Thus, ULF characteristics observed at a single site in the polar cap cannot be freely generalized to other sites of similar CGM latitude but separated in magnetic local time, and the inadequacy of CGM coordinates in the polar cap has implications for conjugacy/mapping studies in general. In seeking alternative, observationally motivated systems of “polar cap latitudes,” it is found that eccentric dipole (ED) coordinates have several strengths in organizing the hydromagnetic spatial structure in the polar cap region. ED latitudes appear to better classify the local‐time ULF power in both magnitude and morphology and better differentiate the “deep polar cap” (where the ULF power is largely UT dependent and nearly free of local‐time structure) from the “peripheral polar cap” (where near‐magnetic noon pulsations dominate at lower and lower frequencies as one increases in ED latitude). Eccentric local time is shown to better align the local‐time profiles in the magnetic east component over several PcX bands but worsen in the magnetic north component. It is suggested that a hybrid ED‐CGM coordinate system might capture the strengths of both CGM and ED coordinates. It is shown that the local‐time morphology of median ULF power at high‐latitude sites is dominantly driven by where they project into the magnetosphere, which is best quantified by their proximity to the low‐altitude cusp on the dayside (which is not necessarily quantified by a site's CGM latitude), and that variations in the local‐time morphology at sites similar in ED latitude are due to both geographic local‐time control (relative amplification or dampening by the diurnal variation in the local ionospheric conductivity) and geomagnetic coastal effects (enhanced power in a coastally mediated direction). Regardless of cause, it is emphasized that the application of CGM latitudes in the polar cap region is not entirely meaningful and likely should be dispensed with in favor of a scheme that is in better accord with the observed hydromagnetic spatial structure.

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Observations of solar wind directly driven auroral electrojets and gravity waves

Cited by 11 publications

References 26 publications

Characteristics of medium‐scale traveling ionospheric disturbances observed near the Antarctic Peninsula by HF radar

Characteristics of medium‐scale traveling ionospheric disturbances observed near the Antarctic Peninsula by HF radar

Effects of solar wind variations on the midlatitude ionosphere

Rethinking the polar cap: Eccentric dipole structuring of ULF power at the highest corrected geomagnetic latitudes

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