Geomagnetic response at low latitude to continuous solar wind pressure variations during northward interplanetary magnetic field

Francia, P.; Lepidi, S.; Villante, U.; Giuseppe, P. Di; Lazarus, A. J.

doi:10.1029/1999ja900229

Cited by 33 publications

(27 citation statements)

References 13 publications

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“…We used 6-min running averages (with a step size of 1-min) of both the SW and geomagnetic data to rule out the shortest period variations and then detrended the geomagnetic data to eliminate the long-term variations. At all stations, we found the highest values of ρ coefficients for a time delay of 37 min, which is comparable to the SW estimated transit time along the radial direction between ACE and the subsolar point of the bowshock (∼31 min, at an average speed of ∼800 km/s) plus a few minutes due to the propagation to the ground (similar results on the time delay between spacecraft and ground observations were also found in the analysis by Francia et al, 1999); in Fig. 7, we show the square root of the SW pressure (the data have been shifted for the time delay of 37 min) and the H component at the different stations in the time interval of interest.…”

Section: Resultssupporting

confidence: 71%

“…In particular, it can be seen that the value of the response at AQU (21 nT/(nPa) 1/2 ) is slightly higher than the value found previously just after the local noon (17.5 nT /(nPa) 1/2 ) in the statistical analysis of Francia et al (1999) and that at the subauroral station NUR, it is higher (42 nT/(nPa) 1/2 ) than the geomagnetic response level (between 20-30 nT/(nPa) 1/2 ) observed after local noon by Russell and Ginskey (1995) in the statistical analysis of SIs at subauroral latitudes. Figure 8 also shows that, along the 210 MM array, situated in premidnight sector, the latitudinal dependence of the response is not clearly defined: in particular, some evidence for a latitudinal increase in the response (although less steep than along the European array) emerges up to ZYK; however, an anomalous high response is observed at MSR, with a value (26 nT/(nPa) 1/2 ) much higher than observed previously at approximately the same latitude during the local evening (∼14 nT/(nPa) 1/2 ) in the statistical study of Francia et al (1999). Also, the response at MGD is much higher with respect to the value found for the same local time by Russell and Ginskey (1995) at subauroral latitudes.…”

Section: Resultsmentioning

confidence: 75%

“…We noted previously the lack of a geomagnetic response to the continuous SW pressure variations observed between 03:00-07:40 UT, not only along the European array in the local morning (when the amplitude of the response at midlatitudes should be minimum, Francia et al, 1999), but also at the 210 MM stations after the local noon (when its amplitude at mid-latitudes should be high, Francia et al, 1999); this feature seems to indicate that the magnetosphere, which is still recovering from a major geomagnetic storm, does not clearly respond to the continuous SW pressure variations. We noted, however, that some correspondence with the SW pressure variations emerges at CHD from ∼05:00 UT (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, in a statistical study, Francia et al (1999) analyzed some events occurring during northward IMF conditions and showed that the geomagnetic field horizontal component H at a low-latitude station (L'Aquila) responds very well to the SW pressure variations on a time scale of few minutes. The amplitude of the geomagnetic response was found to be linearly related to the change in the square root of the SW dynamic pressure, and its average amplitude (∼13 nT/(nPa) 1/2 ) is comparable with the values found by Russell et al (1994) and Russell and Ginskey (1995) at low and subauroral latitudes in the analysis of the sudden impulse (SI) response to the passage of interplanetary shocks.…”

Section: Introductionmentioning

confidence: 99%

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Geomagnetic field fluctuations during the passage at the Earth’s orbit of the tail of the 15–16 July 2000 ejecta

2002

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Abstract. In this work we present the analysis of the geomagnetic field fluctuations observed at different ground stations (approximately along two latitudinal arrays, separated by several hours in local time) during the passage at the Earth's orbit of the tail of the 15-16 July 2000 coronal ejecta. The time interval of interest is characterized by northward interplanetary magnetic field conditions and several changes in the solar wind dynamic pressure. We found at all stations, both in the local morning and in the local evening, simultaneous and highly coherent waves at the same discrete frequencies (∼1.8 and ∼3.6 mHz) and suggest a possible interpretation in terms of global compressional modes driven by an impulsive variation of the solar wind pressure. Along the array situated in the morning sector, at the highest latitudes, the higher frequency mode seems to couple with the local field line resonance; on the other hand, along the array situated in the evening sector, the characteristics of the observed fluctuations suggest that the highest latitude station could be located at the footprint of open field lines. Our results also show that solar wind pressure variations observed during the recovery phase of the storm do not find correspondence in the geomagnetic field variations, regardless of local time and latitude; conversely, some hours later continuous solar wind pressure variations find a close correspondence in the geomagnetic field variations at all stations.

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Section: Resultssupporting

confidence: 71%

Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geomagnetic field fluctuations during the passage at the Earth’s orbit of the tail of the 15–16 July 2000 ejecta

2002

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“…Their analysis, however, did not include ground observations. On the other hand, a clear correlation between the variations of the H component and the variations of the SW dynamical pressure on time scales of few minutes was found in a case study by Francia et al (1999). This aspect has been corroborated recently by Villante et al (2005b), who presented a joint analysis of SW, magnetospheric and ground observations, and showed that remarkable ground events at "selected" frequencies found a clear correspondence in the magnetospheric field at geostationary orbit, as well as in the SW density (and dynamical pressure).…”

Section: Low Frequency Magnetospheric Modes During the Stormmentioning

confidence: 99%

ULF fluctuations of the geomagnetic field and ionospheric sounding measurements at low latitudes during the first CAWSES campaign

Villante¹,

Vellante²,

Francia³

et al. 2006

Ann. Geophys.

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Abstract.We present an analysis of ULF geomagnetic field fluctuations at low latitudes during the first CAWSES campaign (29 March-3 April 2004). During the whole campaign, mainly in the prenoon sector, a moderate Pc3-4 pulsation activity is observed, clearly related to interplanetary upstream waves. On 3 April, in correspondence to the Earth's arrival of a coronal mass ejection, two SIs are observed whose waveforms are indicative of a contribution of the high-latitude ionospheric currents to the low-latitude ground field. During the following geomagnetic storm, low frequency (Pc5) waves are observed at discrete frequencies. Their correspondence with the same frequencies detected in the radial components of the interplanetary magnetic field and solar wind speed suggests that Alfvénic solar wind fluctuations may act as direct drivers of magnetospheric fluctuations. A cross-phase analysis, using different pairs of stations, is also presented for identifying field line resonant frequencies and monitoring changes in plasmaspheric mass density. Lastly, an analysis of ionospheric vertical soundings, measured at the Rome ionosonde station (41.8 • N, 12.5 • E), and vertical TEC measurements deduced from GPS signals within an European network shows the relation between the ULF resonances in the inner magnetosphere and thermal plasma density variations during geomagnetically quiet conditions, in contrast to various storm phases at the end of the CAWSES campaign.

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Van Allen probes, NOAA, GOES, and ground observations of an intense EMIC wave event extending over 12 h in magnetic local time

et al. 2015

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Although most studies of the effects of electromagnetic ion cyclotron (EMIC) waves on Earth's outer radiation belt have focused on events in the afternoon sector in the outer plasmasphere or plume region, strong magnetospheric compressions provide an additional stimulus for EMIC wave generation across a large range of local times and L shells. We present here observations of the effects of a wave event on 23 February 2014 that extended over 8 h in UT and over 12 h in local time, stimulated by a gradual 4 h rise and subsequent sharp increases in solar wind pressure. Large‐amplitude linearly polarized hydrogen band EMIC waves (up to 25 nT p‐p) appeared for over 4 h at both Van Allen Probes, from late morning through local noon, when these spacecraft were outside the plasmapause, with densities ~5–20 cm−3. Waves were also observed by ground‐based induction magnetometers in Antarctica (near dawn), Finland (near local noon), Russia (in the afternoon), and in Canada (from dusk to midnight). Ten passes of NOAA‐POES and METOP satellites near the northern foot point of the Van Allen Probes observed 30–80 keV subauroral proton precipitation, often over extended L shell ranges; other passes identified a narrow L shell region of precipitation over Canada. Observations of relativistic electrons by the Van Allen Probes showed that the fluxes of more field‐aligned and more energetic radiation belt electrons were reduced in response to both the emission over Canada and the more spatially extended emission associated with the compression, confirming the effectiveness of EMIC‐induced loss processes for this event.

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Geomagnetic response at low latitude to continuous solar wind pressure variations during northward interplanetary magnetic field

Cited by 33 publications

References 13 publications

Geomagnetic field fluctuations during the passage at the Earth’s orbit of the tail of the 15–16 July 2000 ejecta

Geomagnetic field fluctuations during the passage at the Earth’s orbit of the tail of the 15–16 July 2000 ejecta

ULF fluctuations of the geomagnetic field and ionospheric sounding measurements at low latitudes during the first CAWSES campaign

Van Allen probes, NOAA, GOES, and ground observations of an intense EMIC wave event extending over 12 h in magnetic local time

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