What is the weather like at the LOFAR core?

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Members of the LOFAR cosmic ray key science project (RU Nijmegen and Groningen), with the helpful support from Menno Norden and Klaas Stuurwold (ASTRON), have installed a weather station at the concentrator node, close to the LOFAR superterp. As cosmic rays generate "air showers" of secundary particles in the atmosphere, the atmospheric conditions are important factors for the understanding of the data.

Especially interesting is the measurement of the atmospheric electric field, which allows an independent confirmation of thunderstorms detected with LOFAR. Also, solar activity can be detected, as happened already during the first days of operations (see inset).

Data will be taken at intervals of a minute, and will also be made available to other interested users of LOFAR. These measurements will help to define good observing conditions for the various LOFAR programs, and support the study of the performance of hardware as function of environmental conditions.