Are trends in total electron content (TEC) really positive?

0394691 - ÚFA 2014 RIV US eng J - Journal Article
Laštovička, Jan
Are trends in total electron content (TEC) really positive?
Journal of Geophysical Research-Space Physics. Roč. 118, č. 6 (2013), s. 3831-3835. ISSN 2169-9380. E-ISSN 2169-9402
R&D Projects: GA ČR GAP209/10/1792
Institutional support: RVO:68378289
Keywords : Long-term trends * total electron content
Subject RIV: DG - Athmosphere Sciences, Meteorology
Impact factor: 3.440, year: 2013
http://onlinelibrary.wiley.com/doi/10.1002/jgra.50261/abstract

The total electron content (TEC) is a primary ionospheric parameter as it can be studied globally using signals of GNSS satellites. Lean et al. (2011, JGR) in the first study of long-term trends in TEC found positive trends for the period 1995–2010 based on TEC derived from global GPS observations. However, the positive trends seem to be inconsistent with both observed and modeled trends in foF2. Here we try to shed light on this puzzle using historical Faraday rotation TEC measurements and foF2 data over the period 1995–2010. We use data from European area where Lean et al. (2011) report remarkably stronger than average positive trend of TEC. These data suggest no trend of TEC in this region in the past but also almost no trend of foF2 over 1995–2010 compared with a negative trend in solar cycles 21 and 22. This means that the trends for 1995–2010 are more positive than trends for the period 1976–1996 and that the trends for 1995–2010 are not representative for the previous period. The magnitude of trends for 1995–2010 is to some extent uncertain due to the uncertain level of the solar EUV flux in the deep solar minimum in 2008 and 2009.
Permanent Link: http://hdl.handle.net/11104/0222881