Topside equatorial ionospheric density and composition during and after extreme solar minimum

• Published in: Journal of Geophysical Research: Space Physics Vol. 116; no. A12
• Main Authors: Klenzing, J., Simões, F., Ivanov, S., Heelis, R. A., Bilitza, D., Pfaff, R., Rowland, D.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-12-2011
• Subjects: Atmospheric sciences; C/NOFS; CINDI; Equator; equatorial ionosphere; Ionosphere; IRI-2007; Solar activity; Solar energy; solar minimum
• ISSN: 0148-0227; 2169-9380; 2156-2202; 2169-9402
• DOI: 10.1029/2011JA017213

During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth's ionosphere‐thermosphere system when compared to previous solar minima. Among these are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the Communication/Navigation Outage Forecast System (C/NOFS) satellite to characterize the shape of the topside ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI‐2007 model. Building on initial results reported by Heelis et al. (2009), here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.
Key Points
The highly contracted ionosphere persists through 2009
IRI‐2007 tends to overestimate O+ and underestimate H+ during extreme solar min
Ion density and composition during 2010 is comparable to previous solar minima