Preface Recent advances in equatorial, low- and mid-latitude aeronomy This special issue of the Journal of Atmospheric and Solar– Terrestrial Physics on “Recent Advances in Equatorial, Low- and Mid-latitude Aeronomy” contains selected papers presented at the 13th International Symposium on Equatorial Aeronomy (ISEA13). This symposium is the latest in a long series of ISEAs, which was started in 1962 soon after the Jicamarca Radio Observatory (JRO) began its operation near Lima, Peru. The first ISEA was held in Huaychulo, Peru; and since then the symposium has been held every 3–5 years at different locations around the globe, bringing together scientists from all over the world, who are interested in the low- and mid-latitude atmosphere and ionosphere, and their coupling to other latitudes and altitudes. The ISEAs have become important events for researchers working in this field, as it offers them an opportunity to share their most recent results and discuss new techniques and possibilities for future coordinated campaigns and experiments. Fifty years after the first ISEA, the 13th symposium in the series returned to Peru. ISEA13 was held in Paracas, Peru, during March 12–16, 2012 and many of the participants joined in the celebration of another important event: the 50th Anniversary of the JRO, which has over the years played a key role in advancing our knowledge in the field of equatorial aeronomy. The celebration program included a detailed tour of the facilities at JRO guided by JRO scientists, technicians, and frequent users. The main sponsors of ISEA13 were the US National Science Foundation (NSF), the US Air Force Office of Scientific Research (AFOSR) and the Southern Office of Aerospace Research and Development (SOARD), Scientific Committee On Solar–Terrestrial Physics (SCOSTEP) and Climate And Weather of the Sun–Earth System (CAWSES), the International Association of Geomagnetism and Aeronomy (IAGA), the International Union of Radio Science (URSI), and the Consejo Nacional De Ciencia Y Tecno- logía del Perú (CONCYTEC). In addition, ISEA13 received support from private companies in Peru. Most of the support received was utilized to support the participation of young scientists and researchers from developing countries. ISEA13 was attended by 150 participants from 23 countries and included 25 students. During the 5 days of the symposium, 120 oral talks were presented and 95 posters were displayed during two poster sessions. The oral and poster presentations covered a wide range of topics, which were divided into eight broad areas: (1) Irregularity Physics; (2) E and F region coupling (low- and mid- latitude coupling); (3) wave propagation between low/middle atmosphere and ionosphere; (4) plasma–neutral coupling; (5) low- and mid-latitude aeronomy and electrodynamics; (6) iono- spheric storms and space weather effects at low- and mid-latitudes; (7) new techniques, experiments, campaigns, and results; and (8) future trends and challenges. Some of these topics have attracted a great deal of attention over the years, but continue to pose challenges to our understanding of them. Irregularity Physics is one such area, where for instance, in the case of the much-studied equatorial plasma bubbles, the conditions that influence their development, including the seeding of the plasma instability process in the equatorial F region, continue to be of current interest. New in-situ measurements around the bubble region have also been reported. In the equatorial E region, electrojet irregularities have been studied for many years, but the non-linear nature of large-scale waves in the electrojet remained unresolved. Besides these outstanding issues, rare daytime F-region irregularities and some aspects of mid-latitude irregularities were also discussed in the symposium. Variability of the quiettime low-latitude iono- sphere was a major theme in ISEA13, with several presentations on the effects of sudden stratospheric warming as well as the effects of lunar tides on the low-latitude ionosphere. Observations and modeling of thermospheric variability was the topic of several papers, while some presentations dealt specifically with phenom- ena such as the occurrence of equatorial F3 layer and the midnight temperature maximum. An entirely new development since the last ISEA, which was held in 2008, was the attention paid to special features of plasma-neutral coupling during the recent deep solar minimum. Modulation of equatorial and low-latitude electrody- namics by promptly penetrating magnetospheric electric fields during magnetically active periods and the role played by local conditions in this process, were some of the topics covered that are important from the point of view of space weather. The 22 papers included in this special issue are representative of the diverse nature of topics related to equatorial, low- and mid- latitude aeronomy that were addressed in ISEA13. The Guest Editors wish to thank all the authors and the reviewers for their painstaking efforts, which made possible the realization of this special issue. The Guest Editors would also like to gratefully acknowledge the constant support and cooperation extended by Ms. Kreeti Saravanan, the JASTP Special Issue Manager, in our editorial work. List of ISEA13 special issue reviewers Abdu Mangalathayil Ali Akmaev Rashid Alken Patrick Anderson David Archana Bhattacharyya Aveiro Henrique Balan Nanan Batista Inez Bhatt Asti Candido Claudia Nicoli Choudhary Rajkumar Clemesha Barclay Cosgrove Russell Cueva Richardo Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jastp Journal of Atmospheric and Solar-Terrestrial Physics 1364-6826/$ - see front matter & 2013 Published by Elsevier Ltd. http://dx.doi.org/10.1016/j.jastp.2013.08.017 Journal of Atmospheric and Solar-Terrestrial Physics 103 (2013) 1–2