Magnetized plasma is emerging continually from the solar interior into its atmosphere. Magnetic flux emergence events and their consequences at different levels in the solar atmosphere are being observed with high space, time and spectral resolution by a large number of space missions in operation at present (e.g. SOHO, Hinode, Stereo, Rhessi), sent by different international space agencies (ESA, NASA, ISAS). The collision of an emerging and a preexisting magnetic flux system in the solar atmosphere leads to the formation of current sheets and to field line reconnection. Reconnection under solar coronal conditions is an energetic event; the reconnecting outfllows lead to launching of high-speed (hundreds of 1000 km/s), high-temperature (order 10 million K) plasma jets, which are conspicuous features in the observations with the X-Ray and EUV dectectors currently in orbit. Further, the spectacular increase in computational power in recent years thanks to the new supercomputer installations permits to carry out three-dimensional numerical experiments of the time evolution of magnetic flux emerging systems that include magnetofluid and radiative transfer aspects in large computational grids.

In this review, the state-of-the-art in this field of research will be reviewed. The spectacular observations of X-Ray jets in the solar corona by the satellite missions Hinode and Stereo will be presented. The focus of the lecture will be on the theoretical understanding of these processes from a plasma physics point of view. An important computational effort is being done by teams in different countries to model and understand the physics of flux emergence events and its related phenomena. Recent advances obtained through the interplay of theory, numerical simulation and direct observation will be presented.