Comments on "Long‐Term Variations of Exospheric Temperature Inferred From foF1 Observations: A Comparison to ISR Ti Trend Estimates" by Perrone and Mikhailov. Issue 5 (18th May 2018)

• Record Type: Journal Article
• Authors: Zhang, Shun‐Rong; Holt, John M.; Erickson, Philip J.; Goncharenko, Larisa P.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 5(2018)
• Page Start: 4467
• Page End: 4473
• Publication Date: 2018-05-18
• Subjects: long‐term trends -- incoherent scatter radar -- exosphere temperature -- ionospheric foF1; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2017JA024948
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Perrone and Mikhailov (2017, https://doi.org/10.1002/2017JA024193 ) and Mikhailov et al. (2017, https://doi.org/10.1002/2017JA023909 ) have recently examined thermospheric and ionospheric long‐term trends using a data set of four thermospheric parameters (Te x, [O], [N2 ], and [O2 ]) and solar EUV flux. These data were derived from one single ionospheric parameter, foF1, using a nonlinear fitting procedure involving a photochemical model for the F1 peak. The F1 peak is assumed at the transition height h t with the linear recombination for atomic oxygen ions being equal to the quadratic recombination for molecular ions. This procedure has a number of obvious problems that are not addressed or not sufficiently justified. The potentially large ambiguities and biases in derived parameters make them unsuitable for precise quantitative ionospheric and thermospheric long‐term trend studies. Furthermore, we assert that Perrone and Mikhailov (2017, https://doi.org/10.1002/2017JA024193 ) conclusions regarding incoherent scatter radar (ISR) ion temperature analysis for long‐term trend studies are incorrect and in particular are based on a misunderstanding of the nature of the incoherent scatter radar measurement process. Large ISR data sets remain a consistent and statistically robust method for determining long term secular plasma temperature trends. Plain Language Summary: We comment on several studies on thermospheric and ionospheric long‐term trends using a data set of four thermospheric parameters (Tex, [O], [N2], and [O2]) and solar EUV flux. These data were derived from one single ionospheric parameter, foF1, using a nonlinear fitting procedure involving a photochemical model. We point out a number of obvious problems of the procedure and question the validity of the data sets for any meaningful long‐term trend studies. In addition, we assert that Perrone and Mikhailov (2017, https://doi.org/10.1002/2017JA024193 ) conclusions regarding incoherent scatter radar (ISR) ion temperature analysis for long‐term trend studies are incorrect and in particular are based on a misunderstanding of the nature of the incoherent scatter radar measurement process; large ISR data sets remain a consistent and statistically robust method for determining long‐term secular plasma temperature trends. Key Points: Determination of Tex, [O], [N2 ], [O2 ], and EUV flux from a single ionospheric parameter foF1 is not possible without significant ambiguity Such derivations are very problematic for long‐term trend studies Large ISR data sets remain a consistent and statistically robust method for determining long‐term secular plasma temperature trends