scholarly journals Low frequency geomagnetic field fluctuations at low latitude during the passage of a higher pressure solar wind region

1997 ◽  
Vol 15 (6) ◽  
pp. 656-661
Author(s):  
U. Villante ◽  
P. Francia
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Low Frequency ◽  
Frequency Range ◽  
Low Latitude ◽  
Wind Region ◽  
Spectral Peaks ◽  
Field Fluctuations ◽  
Term Analysis

Abstract. The passage of a higher pressure solar wind region at the Earth's orbit marked the onset of low latitude (L=1.6) fluctuations in the frequency range (0.8–5.5 mHz) for both the horizontal geomagnetic field components. Spectral peaks mostly occur at the same frequencies as the spectral enhancements which appeared in the long term analysis of experimental measurements from the same station and were tentatively interpreted in terms of ground signatures of global magnetospheric modes. A comparison with simultaneous observations discussed by previous investigations allows us to conclude that the same set of frequencies is enhanced in a wide portion of the Earth's magnetosphere.

Polarization pattern of low-frequency geomagnetic field fluctuations (0.8-3.6 mHz) at high and low latitude

1999 ◽  
Vol 104 (A1) ◽  
pp. 305-310 ◽  
Author(s):  
S. Lepidi ◽  
P. Francia ◽  
U. Villante ◽  
L. J. Lanzerotti ◽  
A. Meloni
Keyword(s):  
Geomagnetic Field ◽  
Low Frequency ◽  
Polarization Pattern ◽  
Low Latitude ◽  
Field Fluctuations

scholarly journals The Earth's passage of the April 11, 1997 coronal ejecta: geomagnetic field fluctuations at high and low latitude during northward interplanetary magnetic field conditions

1999 ◽  
Vol 17 (10) ◽  
pp. 1245-1250 ◽  
Author(s):  
S. Lepidi ◽  
P. Francia ◽  
U. Villante ◽  
A. Meloni ◽  
A. J. Lazarus ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Interplanetary Magnetic Field ◽  
Geomagnetic Field ◽  
Field Conditions ◽  
Mhd Waves ◽  
Low Latitude ◽  
Terra Nova Bay ◽  
Field Fluctuations ◽  
Terra Nova

Abstract. An analysis of the low frequency geomagnetic field fluctuations at an Antarctic (Terra Nova Bay) and a low latitude (L'Aquila, Italy) station during the Earth's passage of a coronal ejecta on April 11, 1997 shows that major solar wind pressure variations were followed at both stations by a high fluctuation level. During northward interplanetary magnetic field conditions and when Terra Nova Bay is close to the local geomagnetic noon, coherent fluctuations, at the same frequency (3.6 mHz) and with polarization characteristics indicating an antisunward propagation, were observed simultaneously at the two stations. An analysis of simultaneous measurements from geosynchronous satellites shows evidence for pulsations at approximately the same frequencies also in the magnetospheric field. The observed waves might then be interpreted as oscillation modes, triggered by an external stimulation, extending to a major portion of the Earth's magnetosphere. Key words. Magnetospheric physics (MHD waves and instabilities; solar wind-magnetosphere interactions)

scholarly journals Pc5 geomagnetic field fluctuations at discrete frequencies at a low latitude station

2001 ◽  
Vol 19 (3) ◽  
pp. 321-325 ◽  
Author(s):  
U. Villante ◽  
P. Francia ◽  
S. Lepidi
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Wind Pressure ◽  
Mhd Waves ◽  
Low Latitude ◽  
Time Intervals ◽  
Latitude Station ◽  
Field Fluctuations ◽  
Mhd Waves And Instabilities ◽  
Solar Wind Pressure

Abstract. A statistical analysis of the geomagnetic field fluctuations in the Pc5 frequency range (1–5 mHz) at a low latitude station (L = 1.6) provides further evidence for daytime power peaks at discrete frequencies. The power enhancements, which become more pronounced during high solar wind pressure conditions, may be interpreted in terms of ground signatures of magnetospheric cavity/waveguide compressional modes driven by solar wind pressure pulses. In this sense, the much clearer statistical evidence for afternoon events can be related to corotating structures mainly impinging the postnoon magnetopause. A comparison with results obtained for the same time intervals from previous investigations at higher latitudes and in the Earth’s magnetosphere confirms the global character of the observed modes.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind-magnetospheric interactions)

scholarly journals Pc3 pulsations during variable IMF conditions

1999 ◽  
Vol 17 (4) ◽  
pp. 490-496 ◽  
Author(s):  
U. Villante ◽  
S. Lepidi ◽  
P. Francia ◽  
M. Vellante ◽  
A. Meloni ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Mhd Waves ◽  
Variable Frequency ◽  
Low Latitude ◽  
Terra Nova Bay ◽  
Field Fluctuations ◽  
Polarization Characteristics ◽  
Mhd Waves And Instabilities ◽  
Very High

Abstract. Pc3 geomagnetic field fluctuations detected at low latitude (L'Aquila, Italy) during the passage of a high velocity solar wind stream, characterized by variable interplanetary magnetic field conditions, are analyzed. Higher frequency resonant fluctuations and lower frequency phenomena are simultaneously observed; the intermittent appearance and the variable frequency of the longer period modes can be well interpreted in terms of the variable IMF elements; moreover their polarization characteristics are consistent with an origin related to external waves propagating in antisunward direction. A comparison with simultaneous observations performed at Terra Nova Bay (Antarctica) provides additional evidence for a clear relationship between the IMF and Pc3 pulsations also at very high latitudes.Key words. Magnetospheric physics (MHD waves and instabilities; solar wind · magnetosphere interactions)

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

2006 ◽  
Vol 24 (5) ◽  
pp. 1455-1468 ◽  
Author(s):  
U. Villante ◽  
M. Vellante ◽  
P. Francia ◽  
M. De Lauretis ◽  
A. Meloni ◽  
...  
Keyword(s):  
Solar Wind ◽  
Geomagnetic Field ◽  
Mass Density ◽  
Solar Wind Speed ◽  
Low Frequency ◽  
Ionospheric Currents ◽  
Ground Field ◽  
Low Latitudes ◽  
Field Fluctuations ◽  
Pulsation Activity

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.

scholarly journals Multifractal analysis of low-latitude geomagnetic fluctuations

2009 ◽  
Vol 27 (2) ◽  
pp. 569-576 ◽  
Author(s):  
M. J. A. Bolzan ◽  
R. R. Rosa ◽  
Y. Sahai
Keyword(s):  
Solar Wind ◽  
High Latitude ◽  
Geomagnetic Field ◽  
Large Deviation ◽  
Multifractal Spectrum ◽  
Low Latitude ◽  
Physical Mechanisms ◽  
Wavelet Transform Modulus Maxima ◽  
Variability Pattern ◽  
Modulus Maxima

Abstract. The technique of large deviation multifractal spectrum has shown that the high-latitude (77.5° N, 69.2° W) geomagnetic fluctuations can be described from direct dissipation process or loading-unloading regimes of the solar wind-magnetosphere coupling. In this paper, we analyze the H-component of low-latitude (22.4° S, 43.6° W) geomagnetic field variability observed during the month of July 2000 at the Geomagnetic Observatory, Vassouras, RJ, Brazil. The variability pattern during this period is a mixture of quiet and disturbed days including the Bastille Day intense geomagnetic storm on 15 July. Due to the complexity of this data, we pursue a detailed analysis of the geomagnetic fluctuations in different time scales including a multifractal approach using the singular power spectrum deviations obtained from the wavelet transform modulus maxima (WTMM). The results suggest, as observed from high-latitude data, the occurrence of low-latitude multifractal processes driving the intermittent coupling between the solar wind-magnetosphere and geomagnetic field variations. On finer scales possible physical mechanisms in the context of nonlinear magnetosphere response are discussed.

scholarly journals Study of the solar wind coupling to the time difference horizontal geomagnetic field

2005 ◽  
Vol 23 (5) ◽  
pp. 1949-1957 ◽  
Author(s):  
P. Wintoft
Keyword(s):  
Solar Wind ◽  
Standard Deviation ◽  
Geomagnetic Field ◽  
Network Models ◽  
Number Density ◽  
Neural Network Models ◽  
Proton Number ◽  
Solar Wind Magnetic Field ◽  
Field Fluctuations ◽  
Time Variations

Abstract. The local ground geomagnetic field fluctuations (Δ B) are dominated by high frequencies and 83% of the power is located at periods of 32 min or less. By forming 10-min root-mean-square (RMS) of Δ B a major part of this variation is captured. Using measured geomagnetic induced currents (GIC), from a power grid transformer in Southern Sweden, it is shown that the 10-min standard deviation GIC may be computed from a linear model using the RMS Δ X and Δ Y at Brorfelde (BFE: 11.67° E, 55.63° N), Denmark, and Uppsala (UPS: 17.35° E, 59.90° N), Sweden, with a correlation of 0.926±0.015. From recurrent neural network models, that are driven by solar wind data, it is shown that the log RMS Δ X and Δ Y at the two locations may be predicted up to 30 min in advance with a correlation close to 0.8: 0.78±0.02 for both directions at BFE; 0.81±0.02 and 0.80±0.02 in the X- and Y-directions, respectively, at UPS. The most important inputs to the models are the 10-min averages of the solar wind magnetic field component Bz and velocity V, and the 10-min standard deviation of the proton number density σn. The average proton number density n has no influence. Keywords. Magnetospheric physics (Solar wind - magnetosphere interactions) – Geomagnetism and paleomagnetism (Rapid time variations)

An analysis of geomagnetic field variations (3 min-2 h) at a low-latitude observatory (L=1.6)

1995 ◽  
Vol 13 (5) ◽  
pp. 522-531
Author(s):  
P. Francia ◽  
U. Villante ◽  
A. Meloni
Keyword(s):  
Geomagnetic Field ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Current System ◽  
Power Level ◽  
Low Frequency ◽  
Low Latitude ◽  
Wind Speeds ◽  
Low Frequency Power ◽  
Frequency Power

Abstract. An analysis of the geomagnetic field variations between 3 min and 2 h at L'Aquila (L=1.6) shows that the power level in the low-frequency range (i.e. for periods longer than approximately 10 min) at solar maximum (1989/90) is much higher than at solar minimum (1985/86). Conversely, at solar minimum, it emerges that there is a greater relative importance of fluctuations with periods smaller than 10 min which might be related to the greater percentage of solar wind speeds greater than approximately 540 km s–1. Diurnal, seasonal and solar cycle variations of both the high- and the low-frequency power are also discussed. We found that several aspects of these variations might be correlated with ionospheric features such as the ionisation of the F2 layer and the location and the intensity of the S current system.

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