AGU regularly has several open editor searches going on. You can find the announcements here.
Right now there is one of relevance to our field: Editor in Chief of Reviews of Geophysics. The ad for this post is about halfway down. Yes, after ~8 years, Mark Moldwin is stepping down from this position. The search committee is formed (no, I am not on it) and they are actively pursuing potential candidates for this job. The application deadline is May 31, so you still have ~2 weeks to put together a compelling letter of interest about why you want the job and would be a good EiC for that journal.
Reviews of Geophysics is entirely by invitation only and, as the name implies, the portfolio is entirely comprised review articles. Note that JGR Space Physics occasionally publishes topical review articles, like this one or this one, written last year for the MTSSP special sections. There is an important difference between the reviews in the two journals. The reviews in JGR Space Physics are written for experts in the field, while the reviews in RoG are written for everyone in AGU. The level of detail and use of jargon is different, or at least should be. RoG only publishes a couple papers per month and spans the entirety of the AGU discipline breadth, so the number of space physics papers is perhaps one or two a year. Being its EiC will definitely stretch you beyond your normal scientific boundaries. Also, RoG‘s Journal Impact Factor has been above 10 for quite a few years running, now; it is the top AGU journal in this metric. So, the search committee is looking for a rather special and dedicated leader to take over this post.
Mark is quite willing to talk about his experience as EiC of Reviews of Geophysics, so if you have any questions about it, then please contact him directly. If you have general questions about editing an AGU journal, then feel free to contact me. To submit your application, follow the directions in the link above.