In this case study we investigate the source region of whistler-mode chorus located close to the geomagnetic equator at a radial distance of 4. 4 Earth radii. We use measurements from the four Cluster spacecraft at separations of less than a few hundreds of km. recorded during the geomagnetic storm of 18 April 2002. https://www.sahmbuffy.com/product-category/led-g4-dimmable/