A comparison of ionospheric O+/light‐ion transition height derived from ion‐composition measurements and the topside ion density profiles over equatorial latitudes

A comparative investigation is made, for the first time, of direct (ion‐composition measurements) and indirect (from topside ion density profiles) methods to determine the O+/light‐ion transition height over equatorial latitudes. The transition height determined from the ion‐composition follows similar latitudinal and local time variations as the underlying Equatorial Ionization Anomaly (EIA) in the F‐region ionosphere. The north‐south hemispheric asymmetries in the transition height from ion composition are consistent with the summer‐to‐winter interhemispheric neutral wind patterns. On the other hand, the transition height derived from ion density profiles is chiefly influenced by changes in the scale height (shape) due to vertical E × B drift at the equator and steep vertical ion density gradients in topside ionosphere. As a result, the transition height derived from topside profiles are systematically lower and exhibit inconsistent latitudinal and local time variations when compared to direct ion‐composition measurements at equatorial latitudes.

[1]  Ying-Hwa Kuo,et al.  Artificial plasma cave in the low‐latitude ionosphere results from the radio occultation inversion of the FORMOSAT‐3/COSMIC , 2010 .

[2]  Xinan Yue,et al.  Error analysis of Abel retrieved electron density profiles from radio occultation measurements , 2010 .

[3]  L. McKinnell,et al.  Topside ionospheric effective scale heights (HT) derived with ROCSAT-1 and ground-based ionosonde observations at equatorial and midlatitude stations , 2009 .

[4]  R. Heelis,et al.  Behavior of the O+/H+ transition height during the extreme solar minimum of 2008 , 2009 .

[5]  Libo Liu,et al.  Topside ionospheric scale heights retrieved from Constellation Observing System for Meteorology, Ionosphere, and Climate radio occultation measurements , 2008 .

[6]  T. Fang,et al.  Motions of the equatorial ionization anomaly crests imaged by FORMOSAT‐3/COSMIC , 2007 .

[7]  Ying-Hwa Kuo,et al.  Comparison of COSMIC ionospheric measurements with ground-based observations and model predictions : Preliminary results , 2007 .

[8]  J. Grebowsky,et al.  Technique for determining midlatitude O+/H+ transition heights from topside ionograms , 2006 .

[9]  S. Pulinets,et al.  Improvements of the International Reference Ionosphere model for the topside electron density profile , 2006 .

[10]  D. Bilitza,et al.  Modeling the F2 Topside and Plasmasphere for IRI , 2005 .

[11]  P. Marinov,et al.  Analytical expression of O+H+ ion transition surface for use in IRI , 1994 .

[12]  R. Heelis,et al.  Ion composition of the topside equatorial ionosphere during solar minimum , 1992 .

[13]  J. Titheridge.  Ion transition heights from topside electron density profiles , 1976 .

[14]  Pencho Marinov,et al.  Topside sounder model of scale height and transition height characteristics of the ionosphere , 2007 .

[15]  Pencho Marinov,et al.  Model of topside ionosphere scale height based on topside sounder data , 2006 .

[16]  Pencho Marinov,et al.  Empirical model of O+–H+ transition height based on topside sounder data , 2004 .