Browsing by Author "Zhao, B."
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Item Restricted Can a nightside geomagnetic Delta H observed at the equator manifest a penetration electric field?(American Geophysical Union, 2013-02-12) Wei, Y.; Fraenz, M.; Dubinin, E.; He, M.; Ren, Z.; Zhao, B.; Liu, J.; Wan, W.; Yumoto, K.; Watari, S.; Alex, S.A prompt penetration electric field (PPEF) usually manifests itself in the form of an equatorial ionospheric electric field being in correlation with a solar wind electric field. Due to the strong Cowling conductivity, a PPEF on the dayside can be inferred from Delta H (ΔH), which is the difference in the magnitudes of the horizontal (H) component between a magnetometer at the magnetic equator and one off the equator. This paper aims to investigate the performance of ΔH in response to a PPEF on the nightside, where the Cowling conductivity is not significant. We first examine the strongest geomagnetically active time during the 20 November 2003 superstorm when the Dst drops to −473 nT and show that the nightside ΔH can indeed manifest a PPEF but with local time dependence and longitude dependence. We then examine a moderately active time by taking advantage of the multiple‐penetration event during 11–16 November 2003 when the Dst remains greater than −60 nT. During this event, a series of PPEF pulses recorded in Peru, Japan, and India form a database, allowing us to examine PPEF effects at different local times and longitudes. The results show that (1) the nightside ΔH was caused by attenuation of the effects of the polar electric field with decreasing latitude; (2) the nightside ΔH can manifest a PPEF at least in the midnight‐dawn sector (0000–0500 LT), but not always; and (3) the magnitude of the nightside ΔH in the midnight‐dawn sector in Peru is on average only 1/18 of that of the dayside ΔH in response to a given PPEF.Item Restricted Stratification of the low-latitude and near-equatorial F2 layer, topside ionization ledge, and F3 layer: What we know about this? A review(Hindawi, 2012-02-06) Klimenko, M. V.; Zhao, B.; Karpachev, A. T.; Klimenko, V. V.A large number of researches have been devoted to the formation of additional layers in the F region of the equatorial ionosphere, first of which has been published in 1940s. Originally the occurrence of such layer was named “stratification of equatorial F2 layer.” The additional layer was later named as the F3 layer. The theoretical researches have shown that the F3 layer is formed by zonal component of electric field with assistance of meridional component of thermospheric wind and field-aligned plasma diffusion. The physical mechanism of the F3 layer formation is clearly formulated for the morning-noon period, although the F3 layer is also observed at other hours. This paper presents a brief review into the history of the additional layer researches, describes the current progress of these researches, and identifies the most important problems in this field of the ionospheric physics.Item Restricted Using IRI and GSM TIP model results as environment for HF radio wave propagation model during the geomagnetic storm occurred on September 26-29, 2011(Elsevier, 2015-05-16) Kotova, D. S.; Klimenko, M. V.; Klimenko, V. V.; Zakharov, V. E.; Ratovsky, K. G.; Nosikov, I. A.; Zhao, B.This paper analyses the geomagnetic storm on September 26–29, 2011. We compare the calculation results obtained using the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) and IRI-2012 (Bilitza et al., 2014) model with ground-based ionosonde data of stations at different latitudes and longitudes. We examined physical mechanisms responsible for the formation of ionospheric effects during the main phase of geomagnetic storm that occurred at the rising phase of the 24th solar cycle. We used numerical results obtained from IRI-2012 and GSM TIP models as propagation environment for HF signals from an equatorial transmitter during quiet and disturbed conditions. We used the model of HF radio wave propagation developed in I. Kant Baltic Federal University (BFU) that is based on the geometrical optics approximation. We compared the obtained radio paths in quiet conditions and during the main and recovery storm phases and evaluated radio wave attenuation in different media models.