Determination of essential reconnection parameters

Magnetic reconnection is one of the most fundamental processes in space plasmas. Our sun emits a stream of magnetized plasma (the solar wind), which collides with Earth`s magnetic field. Since the solar plasma and the terrestrial magnetic field cannot interpenetrate, the solar wind is forced to flow around Earth`s magnetic field. This leads to the establishment of a magnetosphere. Downstream of the Earth, the magnetosphere is stretched into a long magnetotail. The layer separating magnetosphere and solar wind is called magnetopause. In the magnetotail and at the magnetopause special conditions lead to the occurrence of magnetic reconnection. Acceleration and heating of the plasma is a consequence of this process. After decades of describing and confirming this process, the reconstruction of essential reconnection parameters out of satellite observations is the new challenge. Among these parameters, the most important are the reconnection rate, giving information about the effectiveness of the process, the reconnected flux, which can be regarded as a quantity for the impulsivity of the reconnection, as well as the location where reconnection takes place. All of these parameters imply information about the reconnection process and its relevance in the frame of magnetospheric activity. Reconstructing reconnection parameters is a relatively new scientific field, and therefore, the results are largely unverified. One reason why the reconnection process is still not completely understood, is the fact that reconnection has to be investigated over macroscopic as well as microscopic scale lengths. We combine a macroscopic MHD approach with a kinetic one. Latter, by using a PIC simulation with open boundaries. Thus, we can implement investigations on length scales of the order of the ion and electron inertial length and investigate the influence of the Hall term, turbulent, inertial and non-gyrotropic electron pressure tensor terms as well as the role of instabilities on the generation of the reconnection electric field. With this project, we are the first to face the challenge of verifying current reconstruction methods. Firstly, we develop a new method to reconstruct the reconnection rate, the reconnected flux, as well as the location where reconnection is initiated and compare our results with those obtained from previous methods. In a second step, we simulate reconnection in the Earth`s magnetotail under realistic conditions, which can not be implemented in analytical models. This allows us to determine the application domain of our analytical reconstruction method, to adapt and improve it and take kinetic effects into account. Finally, we apply our method to reconnection events observed in-situ by spacecrafts at the Earth`s magnetopause and in the magnetotail. In this frame, we can capitalize on the large Cluster-separation in the year 2005 and beyond, to determine and compare reconnection parameters from satellites at different positions. An important point in this case is the implementation of data from the THEMIS-mission. This work will be done in cooperation with the University of St. Petersburg, the University of New Hampshire, the Mullard Space Science Laboratory in Surrey, U.K., the University of Tokyo, as well as further international partners. This cooperation exists over many years. The results, obtained by this work, will be published in renowned international scientific journals, as the "Journal of Geophysical Research", "Annales Geophysicae", or "Planetary and Space Science". The working group of Prof. Biernat has extensive experience in the field of magnetic reconnection and solar-terrestrial relations, and the Magnetotail group of the Space Research Institute in Graz is strongly involved in the Cluster- and THEMIS-missions.

Magnetic reconnection is one of the most fundamental processes in space plasmas. Our sun emits a stream of magnetized plasma (the solar wind), which collides with Earth`s magnetic field. Since the solar plasma and the terrestrial magnetic field cannot interpenetrate, the solar wind is forced to flow around Earth`s magnetic field. This leads to the establishment of a magnetosphere. Downstream of the Earth, the magnetosphere is stretched into a long magnetotail. The layer separating magnetosphere and solar wind is called magnetopause. In the magnetotail and at the magnetopause special conditions lead to the occurrence of magnetic reconnection. Acceleration and heating of the plasma is a consequence of this process. After decades of describing and confirming this process, the reconstruction of essential reconnection parameters out of satellite observations is the new challenge. Among these parameters, the most important are the reconnection rate, giving information about the effectiveness of the process, the reconnected flux, which can be regarded as a quantity for the impulsivity of the reconnection, as well as the location where reconnection takes place. All of these parameters imply information about the reconnection process and its relevance in the frame of magnetospheric activity. Reconstructing reconnection parameters is a relatively new scientific field, and therefore, the results are largely unverified. One reason why the reconnection process is still not completely understood, is the fact that reconnection has to be investigated over macroscopic as well as microscopic scale lengths. We combine a macroscopic MHD approach with a kinetic one. Latter, by using a PIC simulation with open boundaries. Thus, we can implement investigations on length scales of the order of the ion and electron inertial length and investigate the influence of the Hall term, turbulent, inertial and non-gyrotropic electron pressure tensor terms as well as the role of instabilities on the generation of the reconnection electric field. With this project, we are the first to face the challenge of verifying current reconstruction methods. Firstly, we develop a new method to reconstruct the reconnection rate, the reconnected flux, as well as the location where reconnection is initiated and compare our results with those obtained from previous methods. In a second step, we simulate reconnection in the Earth`s magnetotail under realistic conditions, which can not be implemented in analytical models. This allows us to determine the application domain of our analytical reconstruction method, to adapt and improve it and take kinetic effects into account. Finally, we apply our method to reconnection events observed in-situ by spacecrafts at the Earth`s magnetopause and in the magnetotail. In this frame, we can capitalize on the large Cluster-separation in the year 2005 and beyond, to determine and compare reconnection parameters from satellites at different positions. An important point in this case is the implementation of data from the THEMIS-mission. This work will be done in cooperation with the University of St. Petersburg, the University of New Hampshire, the Mullard Space Science Laboratory in Surrey, U.K., the University of Tokyo, as well as further international partners. This cooperation exists over many years. The results, obtained by this work, will be published in renowned international scientific journals, as the "Journal of Geophysical Research", "Annales Geophysicae", or "Planetary and Space Science". The working group of Prof. Biernat has extensive experience in the field of magnetic reconnection and solar-terrestrial relations, and the Magnetotail group of the Space Research Institute in Graz is strongly involved in the Cluster- and THEMIS-missions.