ULF geomagnetic pulsations in the southern polar cap: Simultaneous measurements near the cusp and the geomagnetic pole

Lauretis, M. De; Francia, P.; Vellante, M.; Piancatelli, A.; Villante, U.; Memmo, D. Di

doi:10.1029/2005ja011058

Cited by 19 publications

(28 citation statements)

References 23 publications

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“…The most accepted mechanisms for the entry of upstream wave energy into the magnetosphere are basically two: a direct propagation through the subsolar region (Russell et al, 1983) and an indirect process involving particle and current modulation at the near-cusp ionosphere (Engebretson et al, 1991). Recently, in order to interpret some aspects of the Pc3 activity in the polar cap, Chugunova et al (2004Chugunova et al ( , 2006 proposed an additional propagation path of upstream waves to the ground via the magnetotail lobes (see also De Lauretis et al, 2005). In the magnetosphere, due to the latitudinal dependence of the field line length, upstream waves can couple to fundamental FLRs at low and mid latitudes, and to higher harmonics at high latitudes (Howard and Menk, 2005).…”

Section: Introductionmentioning

confidence: 99%

ULF geomagnetic pulsations at different latitudes in Antarctica

et al. 2009

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Section: Introductionmentioning

confidence: 99%

ULF geomagnetic pulsations at different latitudes in Antarctica

et al. 2009

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“…When corrected by means of our method, the azimuthal angle at TNB changes, becoming similar to the angle at TLD, while the polarization ratio and ellipticity do not change significantly. These results indicate that the azimuthal angle of polarized ULF waves at the coastal station of TNB is probably affected by horizontal ground conductivity anomalies, attributable to the sea saltwater, as suggested by De Lauretis et al (2005).…”

Section: Discussionmentioning

confidence: 60%

“…This example clearly shows that the polarization characteristics (more evident in the azimuthal angle in this case study) may be affected by ground conductivity anomalies, probably due to the closeness of TNB to the coastline, as suggested by De Lauretis et al (2005) and also observed by Regi et al (2017) in the higher Pc1-2 frequency range and evidenced by the interstation induction arrows at coastal stations.…”

Section: Vertical and Horizontal Transfer Functions Using The Interstmentioning

confidence: 94%

“…Moreover, by examining a Pc5 case event, we observed different polarization characteristics in the horizontal geomagnetic field variations at TNB and TLD, which can be due to the closeness of TNB to the coastline, as suggested by De Lauretis et al (2005).…”

Section: Introductionmentioning

confidence: 99%

“…These results indicate that the signal power at TNB tends to be higher along the east-west magnetic component. As suggested by De Lauretis et al (2005), the polarization characteristics may be affected by ground conductivity anomalies, due to the closeness of TNB to the coast.…”

Section: Introductionmentioning

confidence: 99%

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The geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF range

et al. 2018

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Abstract. We examined the coast effect in Antarctica along the 80 • S magnetic parallel. We used the geomagnetic field measurements at the two coastal stations of Mario Zucchelli Station and Scott Base, and, as a reference, at the inland temporary station Talos Dome, during 18 January-14 March 2008. Spectral analysis in the Pc5 frequency range (1-7 mHz) revealed large differences between coastal and inland stations, such as higher spectral power levels in the vertical component and higher coherence between horizontal and vertical components at coastal stations. Using the interstation method on selected active time intervals, with Talos Dome as a remote reference station, we found that remote reference induction arrows are directed almost perpendicularly with respect to their respective coastlines. Moreover, the singlestation analysis shows that at Talos Dome the amplitude of the induction arrows is much smaller than at coastal stations. These results clearly indicate that coast effect at a few hundred kilometers from the coastline is relatively small. The coast effect on polarization parameters was examined, for a Pc5 event that occurred on 11 March 2008. The results evidenced that the azimuthal angle of polarized signals at one of the coastal stations is largely different with respect to the inland station (by ∼ 110 • ), while the polarization ratio and ellipticity attain comparable values. We proposed a correction method of the polarization parameters, which operates directly in the frequency domain, obtaining comparable azimuthal angles at coastal and inland stations.

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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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ULF geomagnetic pulsations in the southern polar cap: Simultaneous measurements near the cusp and the geomagnetic pole

Cited by 19 publications

References 23 publications

ULF geomagnetic pulsations at different latitudes in Antarctica

ULF geomagnetic pulsations at different latitudes in Antarctica

The geomagnetic coast effect at two 80° S stations in Antarctica, observed in the ULF range

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

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