CAESAR Consultancy, 35 Millington Road, Cambridge CB3 9HW, UKThis special issue is devoted to scientific and educationalissues concerning “Solar, heliospheric and external geophys-ical effects on the Earth’s environment”. Traditionally therehas been a divide between scientific papers and those papersdedicated to educational aspects regarding a scientific sub-ject. As a consequence, papers are in general published injournals dedicated to one or the other type – “scientific oreducational”. The aim of this special issue is to show thatscientific and educational papers can complement each otherwell when published together, offering the reader an interdis-ciplinary approach to the subject matter being covered.The papers collected in this special issue are based both onpresentations given at the EGU06 session ST5.8 “Solar, he-liospheric and external geophysical effects on ecosystems”,as well as on work performed under the umbrella of the four-year Coupling of Atmospheric Layers (CAL) research train-ing network project. CAL was funded by the European Com-mission within the Marie Curie Actions to study unansweredquestions relating to transient luminous events (TLEs), suchas sprites, and their effects on the atmosphere. More specif-ically, CAL concerned thunderstorms, electrical and spaceradiation effects in the stratosphere, mesosphere and lowerthermosphere. The research was also aimed at studying therelation of TLEs to various aspects of the atmospheric sys-tem, and thus the Earth’s climate. CAL consisted of ten sci-entific work-packages as well as one dedicated to the CALtraining program and one to the CAL outreach program.The editorial team listed below would like to thank “Ad-vances in Geosciences” for agreeing to publish this specialissue. We thank all the authors of the papers submitted fortheir motivation and enthusiasm. Finally, special thanks go tothe manuscript reviewers for their precious time and impor-tant feed-back, the result being very successful papers which,we trust, will interest the community.Correspondence to: N. B. Crosby(norma.crosby@oma.be)This special issue is dedicated to the CAL project whichended on 31 October 2006, where not only science was em-phasized, but so also were training and outreach activities.N. B. Crosby and M. J. RycroftSpecial Volume EditorsOutline– Crosby, N. B. and Rycroft, M. J.: Solar, heliosphericand external geophysical effects on the Earth’s environ-ment: Scientific and educational initiatives [Editorialintroduction to special volume]– Chanrion, O., Crosby, N. B., Arnone, E., Boberg, F.,Van der Velde, O., Odzimek, A., Mika, A., Enell, C.-F., Berg, P., Ignaccolo, M., Steiner, R., Laursen, S., andNeubert, T.: The EuroSprite2005 Observational Cam-paign: an example of training and outreach opportuni-ties for CAL young scientists– Bennett, A. J. and Harrison, R. G.: A simple atmo-spheric electrical instrument for educational use– Harrison, R. G. and Bennett, A. G.: Multi-station syn-thesis of early twentieth century surface atmosphericelectricity measurements for upper tropospheric prop-erties– Arnone, E., Berg, P., Arnold, N. F., Christiansen, B., andThejll, P.: Impact of regional stratopause ozone pertur-bations on global climate compared to equivalent uni-formly distributed forcing– Kovaltsov, G. A. and Usoskin, I. G.: Regional cosmicray induced ionization and geomagnetic field changes– Kasatkina, E. A., Shumilov, O. I., and Krapiec, M.: Onperiodicities in long term climatic variations near 68