Effects of solar wind variations on the midlatitude ionosphere

Huang, Chao‐Song; Foster, J. C.; Erickson, P. J.

doi:10.1029/2001ja009025

Cited by 37 publications

(46 citation statements)

References 37 publications

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“…This periodicity may be related to the variations of the same period in solar-wind density around the WHI. Huang, Foster, and Erickson (2002) showed that changes in solar-wind dynamical pressure can cause changes in electric fields and thus variations of global F2 peak electron densities. It is also possible that the periodicity was the results of the nonlinear interaction of the variations of different periods, such as the 9-day and 13.5-day variations.…”

Section: Discussionmentioning

confidence: 99%

Ionospheric Day-to-Day Variability Around the Whole Heliosphere Interval in 2008

et al. 2011

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Ionospheric F2 peak electron densities (NmF2) measured at ten ionosonde stations have been analyzed to investigate ionospheric day-to-day variability around the Whole Heliosphere Interval (WHI) in 2008 (Day of Year (DOY) 50 -140). The ionosonde data showed that there was significant global day-to-day variability in NmF2. This variability had 5-, 7-, 9-, 11-, 13.5-, and 16 -21-day periodicities. At middle latitudes, the ionosphere appeared to respond directly to the solar-wind and interplanetary-magnetic-field (IMF) induced geomagnetic-activity forcing, with the day-to-day variability having the same periods as those in the solar-wind/IMF and geomagnetic activity. At the geomagnetic Equator, the ionosphere had a strong 7-day periodicity, corresponding to the same periodicity in the IMF B z component. In the equatorial anomaly region, the ionosphere showed more complicated day-to-day variability, dominated by the 9-day periodicity. In addition, there were also peri- odicities of 11 days and 16 -21 days in the ionosonde data at some stations. The ionosonde data were compared with the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) simulations that were driven by the observed solar-wind and IMF data during the WHI. The CMIT simulations showed similar ionospheric daily variability seen in the data. They captured the positive and negative responses of the ionosphere at middle latitudes during the first corotating interaction region (CIR) event in the WHI. The response of the model to the second CIR event, however, was relatively weak.

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Section: Discussionmentioning

confidence: 99%

Ionospheric Day-to-Day Variability Around the Whole Heliosphere Interval in 2008

et al. 2011

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“…Various studies suggested that the ionospheric electron content perturbations were also caused by the penetration of magnetospheric electric fields, which were controlled or modulated by the oscillations in the IMF/solar wind pressure (Borovsky, et al, 1993;Fejer and Scherliess, 1998;Sobral et al, 1997;Huang et al, 2002;Unnikrishnan, et al, 2005). The energy and particle injection that takes place during magnetospheric disturbances produce multiple changes to the Earth's high latitude ionosphere-thermosphere system (Pincheira et al, 2002).…”

Section: Discussionmentioning

confidence: 99%

Comparison of chaotic aspects of magnetosphere under various physical conditions using AE index time series

Unnikrishnan

2008

Ann. Geophys.

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Abstract. The deterministic chaotic behaviour of magnetosphere was analyzed, using AE index time series. The significant chaotic quantifiers like, Lyapunov exponent, spatiotemporal entropy and nonlinear prediction error for AE index time series under various physical conditions were estimated and compared. During high solar activity (1991), the values of Lyapunov exponent for AE index time series representing quiet conditions (yearly mean = 0.5±0.1 min −1 ) have no significant difference from those values for corresponding storm conditions (yearly mean = 0.5±0.17 min −1 ). This implies that, for the cases considered here, geomagnetic storms may not be an additional source to increase or decrease the deterministic chaotic aspects of magnetosphere, especially during high solar activity. During solar minimum period (1994), the seasonal mean value of Lyapunov exponent for AE index time series belong to quiet periods in winter (0.7±0.11 min −1 ) is higher compared to corresponding value of storm periods in winter (0.36±0.09 min −1 ). This may be due to the fact that, stochastic part, which is D st dependent could be more prominent during storms, thereby increasing fluctuations/stochasticity and reducing determinism in AE index time series during storms. It is observed that, during low solar active period (1994), the seasonal mean value of entropy for time series representing storm periods of equinox is greater than that for quiet periods. However, significant difference is not observed between storm and quiet time values of entropy during high solar activity (1991), which is also true for nonlinear prediction error for both low and high solar activities. In the case of both high and low solar activities, the higher standard deviations of yearly mean Lyapunov exponent values for AE index time series for storm periods compared to those for quiet periods might be due to the strong interplay between stochasticity and determinism during storms.Correspondence to: K. Unnikrishnan (kaleekkal unni@yahoo.com) It is inferred that, the external driving forces, mainly due to solar wind, make the solar-magnetosphere-ionosphere coupling more complex, which generates many active degrees of freedom with various levels of coupling among them, under various physical conditions. Hence, the superposition of a large number of active degrees of freedom can modify the stability/instability conditions of magnetosphere.

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“…When the magnetosphere is compressed by an enhancement of the solar wind pressure, the dayside magnetopause current is intensified, resulting in an increase of the low-latitude geomagnetic field. IMF reorientations influence the low-latitude geomagnetic field through an electric field penetration process [Nishida, 1968;Fejer et al, 1979;Kelley et al, 1979Kelley et al, , 2003Kikuchi and Araki, 1979;Huang and Foster, 2001;Huang et al, 2002Huang et al, , 2004Huang et al, , 2005Huang et al, , 2006. When the IMF turns from northward to southward, the interplanetary electric field can penetrate into the equatorial ionosphere and cause an eastward electric field in the dayside ionosphere, resulting in disturbances in the ionospheric currents and magnetic field.…”

Section: Introductionmentioning

confidence: 99%

Quantification and hemispheric asymmetry of low‐latitude geomagnetic disturbances caused by solar wind pressure enhancements

Huang¹,

Yumoto²

2006

J. Geophys. Res.

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[1] The solar wind dynamic pressure has significant influence on the magnetic field of the Earth. When the magnetosphere is compressed by a solar wind pressure enhancement, the dayside magnetopause current is enhanced, resulting in an increase in the magnetic field inside the magnetosphere and on the ground. In this paper we present the statistical results of low-latitude geomagnetic disturbances caused by solar wind pressure enhancements under different interplanetary magnetic field (IMF) orientations, including northward, southward, and fluctuating IMF. One of the prominent features of the geomagnetic disturbances revealed in this study is the hemispheric asymmetry and its seasonal dependence. Geomagnetic disturbances in the Northern Hemisphere summer are in general larger than those found simultaneously in the Southern Hemisphere and are smaller in the Northern Hemisphere winter than in the corresponding southern stations. The ratio of the average geomagnetic disturbance at magnetic latitude 36°S to that at magnetic latitude 36°N in winter is 1.36 for northward IMF, 1.64 for fluctuating IMF, and 1.79 for southward IMF. The corresponding ratio at 24°magnetic latitude is 1.49, 1.64, and 2.0, respectively. We suggest that the hemispheric asymmetry is caused by the tilt of the Earth's magnetic axis. Our statistics includes a large data set (160 cases in total), and we derive an empirical formula between the solar wind pressure enhancement and geomagnetic disturbances:, where DH is the change of the low-latitude geomagnetic field and measured with nT, P sw is the solar wind pressure and measured with nPa, and k is a constant. The value of k depends on seasons and is 18.4 if all data are included.Citation: Huang, C.-S., and K. Yumoto (2006), Quantification and hemispheric asymmetry of low-latitude geomagnetic disturbances caused by solar wind pressure enhancements,

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Effects of solar wind variations on the midlatitude ionosphere

Cited by 37 publications

References 37 publications

Ionospheric Day-to-Day Variability Around the Whole Heliosphere Interval in 2008

Ionospheric Day-to-Day Variability Around the Whole Heliosphere Interval in 2008

Comparison of chaotic aspects of magnetosphere under various physical conditions using AE index time series

Quantification and hemispheric asymmetry of low‐latitude geomagnetic disturbances caused by solar wind pressure enhancements

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