Local time asymmetries of the SSC-associated hydromagnetic variations at the geosynchronous altitude

Kuwashima, Masayuki; Fukunishi, H.

doi:10.1016/0032-0633(85)90051-0

Cited by 27 publications

(21 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Both the declining and the ascending structures find clear correspondence in the magnetospheric field observations. These observations also confirm that the magnetospheric response in the noon quadrant is much more explicit than in the dawn and dusk sectors (Kokubun, 1983;Kuwashima and Fukunishi, 1985;Sastri et al, 2001): indeed, a sharp peak-to-peak variation of ∼19.2 nT was observed by Goes 8 (∼11:00 MLT, with a global rising time T of ∼10 min), while the same variation was remarkably smaller (∼13.8 nT) and smoother ( T ∼16 min) at Goes 10 position (∼07:00 MLT). When related to (P the noon quadrant.…”

Section: Introductionsupporting

confidence: 74%

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Villante¹,

Giuseppe²

2004

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. We examined geomagnetic field observations at low and middle latitudes in the Northern Hemisphere during a 50-min interval (12 May 1999), characterized by a complex behaviour of the solar wind dynamic pressure. For the entire interval, the aspects of the geomagnetic response can be organized into four groups of events which show common characteristics for the H and D components, respectively. The correspondence between the magnetospheric field and the ground components reveals different aspects of the geomagnetic response in different magnetic local time (MLT) sectors. For the H component, the correspondence is highly significant in the dusk and night sectors; in the dawn and prenoon sectors it shows a dramatic change across a separation line that extends approximately between (6 MLT, 35 • ) and (13 MLT, 60 • ). For the D component, the correspondence has significant values in the dawn and prenoon regions. We propose a new approach to the experimental data analysis which reveals that, at each station, the magnetospheric field has a close correspondence with the geomagnetic field projection along an axis (M1) that progressively rotates from north/south (night events) to east/west orientation (dawn events). When projected along M1, the geomagnetic signals can be interpreted in terms of a one-dimensional pattern that mostly reflects the field behaviour observed at geostationary orbit. Several features appear more evident in this perspective, and the global geomagnetic response to the SW pressure variations appears much clearer than in other representations. In particular, the MLT dependence of the geomagnetic response is much smaller than that one estimated by previous investigations. A clear latitudinal dependence emerges in the dusk sector. The occurrence of low frequency waves at ∼2.8 mHz can be interpreted in terms of global magnetospheric modes driven by the SW pulse. This event occurred in the recovery phase after the day the SW almost disappeared (11 May 1999): in this sense our results suggest a rapid recovery of almost typical magnetospheric conditionsCorrespondence to: U. Villante (umberto.villante@aquila.infn.it) soon after a huge expansion. Overshoot amplitudes, greater than in other cases, are consistent with a significant reduction of the ring current.

show abstract

Section: Introductionsupporting

confidence: 74%

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Villante¹,

Giuseppe²

2004

Ann. Geophys.

View full text Add to dashboard Cite

show abstract

“…Moreover, the distribution of the SC amplitude in these regions tends to be enhanced in the nighttime sector (20–03 h, MLT), again. This dependence of the SC amplitude on MLT in the daytime sector is similar to that at the subauroral latitudes (L = 3) [ Russell and Ginskey , 1995], but is quite different from that observed at the geostationary orbit [ Kokubun , 1983; Kuwashima and Fukunishi , 1985]. The maximum amplitude at the geostationary orbit tends to appear around noon.…”

Section: Statistical View Of Magnetic Latitude and Local Time Dependementioning

confidence: 50%

“…Therefore these magnetospheric currents are expected to produce magnetic field variations with a strong day‐night asymmetry. In fact, the SC amplitude observed at the geostationary orbit (r = 6.6 Re, Re: 6375 km) shows a clear MLT dependence with its maximum and minimum values around noon and midnight, respectively [ Kokubun , 1983; Kuwashima and Fukunishi , 1985]. Shinbori et al [2004] investigated electric and magnetic field variations in the plasmasphere associated with SCs, and showed that there is no clear MLT dependence of their amplitudes.…”

Section: Introductionmentioning

confidence: 99%

Magnetic latitude and local time dependence of the amplitude of geomagnetic sudden commencements

et al. 2009

View full text Add to dashboard Cite

[1] Statistical analysis of the main impulse (MI) amplitude of geomagnetic sudden commencements (SCs) in a region from the middle latitudes to equator has been made using the long-term geomagnetic field data obtained from the Yap (geomagnetic latitude, q = 0.38°), Guam (q = 5.22°), Okinawa (q = 16.54°), Kakioka (q = 27.18°), Memanbetsu (q = 35.16°), and St. Paratunka (q = 45.58°) stations. The magnetic local time (MLT) dependence of SC amplitude in the middle latitudes showed magnetic field variations produced by two-cell ionospheric currents (DP 2-type currents) which are driven by the dawn-to-dusk electric field accompanying a pair of field-aligned currents (FACs). The effect of the DP 2-type currents at least expands to the low latitude (q = 16.54°). In this region, the DL part of SC produced by the enhanced Chapman-Ferraro currents can be dominant, but the DP part of SC contaminated 7% of the DL one. On the other hand, at the daytime equator between 8:00 and 16:00 (MLT), the SC amplitude is considerably enhanced with its peak amplitude of 3.24 (normalized SYM-H value) around 11:00 (MLT) due to the Cowling effect. Another interesting point is that the SC amplitude in the nighttime sector was enhanced at all the stations again, and its peak value increases with increasing magnetic latitude. This result suggests that the effect of the FACs associated with the MI phase of SC expands to the equator.

show abstract

“…The magnetic field strength variations at GOES-8 are small, even by comparison with other variations seen on this day, which is perhaps surprising considering that they were associated with such large-amplitude magnetopause motion. However, previous studies reveal that the amplitudes of signatures seen at geosynchronous orbit diminish rapidly with distance from local noon [Kuwashima and Fukunishi, 1985]. In addition, we have inferred that the boundary wave has a very limited azimuthal extent.…”

Section: Magnetospheric and Ionospheric Observationsmentioning

confidence: 54%

Comprehensive study of the magnetospheric response to a hot flow anomaly

Sibeck¹,

Бородкова²,

Schwartz³

et al. 1999

J. Geophys. Res.

188

226

View full text Add to dashboard Cite

Abstract. We present a comprehensive observational study of the magnetospheric response to an interplanetary magnetic field (IMF) tangential discontinuity, which first struck the postnoon bow shock and magnetopause and then swept past the prenoon bow shock and magnetopause on July 24, 1996. Although unaccompanied by any significant plasma variation, the discontinuity interacted with the bow shock to form a hot flow anomaly (HFA), which was observed by Interball-1 just upstream from the prenoon bow shock. Pressures within and Earthward of the HFA were depressed by an order of magnitude, which allowed the magnetopause to briefly (-7 min) move outward some 5 R E beyond its nominal position and engulf Interball-1.A timing study employing nearby Interball-1 and Magion-4 observations demonstrates that this motion corresponded to an antisunward and northward moving wave on the magnetopause. The same wave then engulfed Geotail, which was nominally located downstream in the outer dawn magnetosheath. Despite its large amplitude, the wave produced only minor effects in GOES-8 geosynchronous observations near local dawn. Polar Ultraviolet Imager (UVI) observed a sudden brightening of the afternoon aurora, followed by an even more intense transient brightening of the morning aurora. Consistent with this asymmetry, the discontinuity produced only weak near-simultaneous perturbations in highlatitude postnoon ground magnetometers but a transient convection vortex in the prenoon Greenland ground magnetograms. The results of this study indicate that the solar wind interaction with the bow shock is far more dynamic than previously imagined and far more significant to the solar wind-magnetosphere interaction.

show abstract

Local time asymmetries of the SSC-associated hydromagnetic variations at the geosynchronous altitude

Cited by 27 publications

References 12 publications

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Some aspects of the geomagnetic response to solar wind pressure variations: a case study at low and middle latitudes

Magnetic latitude and local time dependence of the amplitude of geomagnetic sudden commencements

Comprehensive study of the magnetospheric response to a hot flow anomaly

Contact Info

Product

Resources

About