Comprehensive Studies On Solar Storm

Solar eruptive phenomena, such as ?are, erupting prominence and coronamass ejection (CME), usually induce radiation storm, particle storm and fastejection of plasma, which may be impact the Earth greatly and result in geomag-netic storm, ionospheric storm, thermospheric storm and so on. Solar storms,the manifestation of hazard weather in space mentioned above, have a number ofphysical effects in the solar-terrestrial environment. As an important cause thatcan inffuence the performance and reliability of space- and ground-based techno-logical systems and can endanger human life, solar storm plays an pivotal role inspace weather research. On the basis of the observations of the solar-terrestrialenvironment, the following aspects are studied observationally, theoretically andnumerically.1. Study on forecast model of solar storm. Aiming at two intense shockevents on 28 and 29 October 2003, this paper presents a Two-Step method,which combines synoptic analysis of space weather–"observing"and quantita-tive prediction–"palpating", and uses it to test predictions. In the first step,"observing", on the basis of observations of the solar source surface magneticfield, interplanetary scintillation (IPS) and ACE spacecraft, we find that thepropagation of the shocks is asymmetric relative to the normal direction of theirsolar sources, and the Earth is located near the direction of the fastest speedand the greatest energy of the shocks. Being two fast ejection shock events, thefast explosion of coronal mass of the extremely high temperature and the strongmagnetic field, and the high speed background solar wind, are also helpful totheir rapid propagation. In the second step,"palpating", we adopt a new mem-bership function of the fast shock events for the ISF method. The predictedresults here show that for the arrival time of the shock at the Earth, the relativeerrors between the observational and the predicted results are 1.8% and 6.7%;and for the magnetic disturbance magnitude, the relative errors are 4.1% and3.1%, respectively. Furthermore, the comparison among the predicted results of our Two-Step method with those of five other prevailing methods shows that theTwo-Step method is advantageous.2. Statistical study of the propagation of solar storms. Using 180 interplan-etary (IP) shock events associated with CMEs during 1997–2005, we investigatethe inffuence of heliospheric current sheet (HCS) upon the propagation and geo-effectiveness of IP shocks Statistically. Our preliminary results are: (1) Themajority of CME–driving IP shocks occurred near the HCS. (2) The numbers ofshock events and related geomagnetic storms observed when the Earth and thesolar source are located on the same side of the HCS, are obviously higher thanthose when the Earth and the solar source are located on the opposite sides ofthe HCS. (3) Parameter jumps across the shock fronts for the same-side eventsare also higher than those for the opposite-side events, and the stronger shocksare mainly attributed to be same-side events. (4) The level of the geomagneticdisturbances is higher for the same-side events than that for the opposite-sideevents. (5) We propose an empirical model to predict the arrival time of theshock at the Earth, whose accuracy is comparable to the other prevailing mod-els. These results show that the HCS is an important physical structure, whichprobably plays an important role in the propagation of interplanetary shocks andtheir geoeffectiveness.3. 3-D kinematic simulation study of the propagation of solar storms. Usingthe 3-D kinematic model, HAF model, to predict the shock arrival time at theEarth and the occurrence of recurrent magnetic storm, and to analyze the impactof CMEs on HCS. Taking the shock associated with CME, erupted on 2004 April4, for example, its arrival time at the Earth predicted by the HAF model is about6 hours later than the observations. The HAF model forecasts the recurrentmagnetic storms in Carrington Rotation 1995 fairly well. In addition, simulationresults show that the ejected plasma of CME and its driving IP shocks willinteract with the sector boundary. Then the interactions will change both theshape of the sector boundary and its arrival time at the Earth substantially.