| Ionospheric storm,which often causes layer confusions of ionosphere, dis-ruption of short-wave communications and phase anomaly of long-wave signals,represents an extreme form of"space weather". Moreover, ionospheric stormusually results in interference of satellite communications and deviations in nav-igation. The investigation of ionospheric storm is an important region in spaceweather. The main results of our works are list as follows:1. The heliosphereic current sheet (HCS) is a characteristic reference surfacefor the organization of solar wind plasma and has important influence on thepropagation and geoeflectiveness of solar disturbances in interplanetary space.Using 141 CME-interplanetary shock (CME-IPS) events and foF2 from eightionosonde stations from January 2000 to September 2005, from the statisticalresults we flnd that there is a"same side–opposite side eflect"in ionosphericnegative storms, i.e., a large portion of ionospheric negative disturbances areinduced by the same-side events (referring to the CMEs whose source located onthe same side of the heliospheric current sheet (HCS) as the Earth), while onlya small portion is associated with the opposite-side events (the CMEs sourcelocated on the opposite side of the HCS as the Earth), the ratio is 128 vs. 46,and which reaches to 41 vs. 14 for the intense ionospheric negative storms. Inaddition, the ionospheric negative storms associated with the same-side eventsare often more intense. The comparison of the same-side event(4 April 2000)and the opposite-side event(2 April 2001) shows that the intensity of ionosphericnegative storm caused by the same-side event is higher than that by the opposite-side event, although their initial conditions are quite similar. Our preliminaryresults show that the HCS has an"impeding"eflect to CME-IPS, which results ina shortage of energy injection in the auroral zone and restraining the developmentof ionospheric negative perturbations.2. Predicting the intensity of ionospheric disturbances plays an importantrole in prediction of ionospheric storms. However, many ionospheric models often get poor results in predicting the intensity of ionospheric storms. Using 86 CME-interplanetary shock (CME-IPS) events, we investigate the correlation betweenthe peak values of some useful parameters of interplanetary space, magnetosphereand ionosphere. The 86 events studied are a subset of the events responsiblefor geomagnetic storms (SYM-Hmin≤?50 nT) associated with CME-IPS eventsduring the period from 1999 to 2008. Based on the statistical results, we attemptto set up a method for predicting foF2 of a single station. The input is modi?edBzmin and the outputs are SYM-Hmin and△foF2min. Then 25 CME-IPS eventsthat caused geomagnetic storms in 1998 and 2009 are used to check the predictionmethod. The results show that our method can be used to predict SYM-Hminand△foF2min.3. Ionospheric storms related to minor geomagnetic disturbance are a topicfull of challenging because of the large variations in Ionosphere for weak en-ergy input from solar wind. In this work we investigate the ionospheric stormsusing multi-instrument observations on 23 June 2000, with a particular focuson periods during weak geomagnetic disturbances (SYM-H> -40 nT). Largeand long-lasting positive and later negative ionospheric storms were observedat middle and high latitudes in Northern Hemisphere by JPL GPS TEC data,and intense negative storms also observed at midlatitudes in Northern Hemi-sphere by ionosondes. We con?rm an enhanced energy input from disturbedsolar wind which last about 12 hours by calculating three coupling functions(Borovsky,Akasofu and Newell), global auroral precipitation and Joule heating,and suggest it as the main cause of the ionospheric storms, though the energyis not large. The ionosphere in Southern Hemisphere are quiet because of theweaker equator wind. Besides, we ?nd the Newell coupling function do the bestto re?ect the energy transfer from disturbed solar wind to magnetosphere. |
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