The Simulation Study On Middle Lightning Phenomenon

Nowadays, the middle lightning phenomena is key topic in the middle and upperatmosphere. In this dissertation, it is studied by numerical simulation.In section of introduction, it is described that the development of the middle lightninginvestigation. In the second and third section, they are simply introduced that the theory ofcharge structure in thundercloud, current characteristic of lightning, the theory on atmospherebreakdown and electron avalanche. All are the foundation of following physical modal.In forth section, a two dimensional, time-dependent quasi electrostatic field (QEF) aremade basing on Possion equation. Using the modal, all of temporal-space characteristic ofRed sprite are well simulated.In fifth section, a two dimensional, time-dependent electromagnetic field modal (EMmodal) is found on Maxwell equations. The simulation results indicated that the electric fieldproduced by lightning distribute in two regions, i.e. near field region and far field region. Thenear field, which is the source producing the Red sprite, is QEF produced by thunderstormsource charges and induced charges. The far field, namely radiated field, which is the sourceproducing the Elves, is caused by the lightning current pulse. The dependent of horizontalexpanding velocity of Elves on the different parameters of discharge current have beendiscussed.In sixth section, we simply discuss the space characteristic of Blue jet using the diffusebreakdown mechanism. It is simply investigated why the altitude of 40-50km is the upperbound of Blue jet and lower limit altitude of Red sprite.In a word, we improve the QEF and EM modal, find some new simulation results whichconsistent with observation and firstly explain some new phenomenon. All these provide agood foundation and indication for further study.