Nonlinear dependence of ionospheric F2 layer critical frequency on solar activity in southern latitudes during solar cycle 23

Seema, C. S.; Prince, P. R.

doi:10.1016/j.asr.2018.05.031

Cited by 3 publications

(5 citation statements)

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“…P is a global index while dNmF2∕dP is seasonal dependent and localized. It is worth mentioning that the hysteresis is local time dependent (e.g., see Seema & Prince, 2018). The bias' contribution to hysteresis evaluation, as demonstrated in Figure 4, will also have opposite sign for stations located in the Northern and Southern Hemispheres (Figure 5c).…”

Section: Discussionmentioning

confidence: 95%

“…In fact, similar methods have been employed in previous studies (e.g., Bremer, 2008;Bremer et al, 2012;Danilov, 2015;Seema & Prince, 2018) to investigate the hysteresis or trends for each month separately. It also affects the extraction of long-term trends if using the regression approach based on the biased NmF2-P relation.…”

Section: Discussionmentioning

confidence: 99%

“…Our results indicate that the monthly method is expected to give a more accurate

N m F 2

‐

P

relation, which will benefit the modeling of solar influence and therefore the evaluation of hysteresis and trends. In fact, similar methods have been employed in previous studies (e.g., Bremer, ; Bremer et al, ; Danilov, ; Seema & Prince, ) to investigate the hysteresis or trends for each month separately. However, prior to this paper, the bias of the yearly average method and its influence on the analysis of the ionospheric hysteresis and trends have not been fully recognized.…”

Section: Discussionmentioning

confidence: 99%

“…The bias' contribution to hysteresis evaluation, as demonstrated in Figure 4, will also have opposite sign for stations located in the Northern and Southern Hemispheres (Figure 5c). It is worth mentioning that the hysteresis is local time dependent (e.g., see Seema & Prince, 2018). In the above analysis we choose 14-hr local time to represent the daytime situation.…”

Section: Discussionmentioning

confidence: 99%

“…The quasi‐linear relation is also facing challenge from the hysteresis phenomenon, that is, the same solar input produces different ionization in the rising and declining phase of solar cycle. It is defined as positive hysteresis if more ionization is produced in the declining phase (Huang, ; Kane, ; Naismith & Smith, ; Naismith et al, ; Ortiz de Adler & Elias, ; Ozguc et al, ; Rao & Rao, ; Seema & Prince, ).…”

Section: Introductionmentioning

confidence: 99%

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The Use of Monthly Mean Average for Investigating the Presence of Hysteresis and Long‐Term Trends in Ionospheric NmF2

et al. 2020

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Yearly averaging is a basic preprocessing of ionospheric data to smooth out the short-term, cyclic variations in the observations. However, we find that the use of yearly (running) average method probably leads to a biased evaluated relation between the ionospheric parameters (e.g., F2 peak electron density, NmF2) and the solar extreme ultraviolet (EUV) irradiance. The bias is essentially related to the annual/seasonal variations of the ionosphere, which means that the ionospheric sensitivity to the solar EUV irradiance varies with season and the same solar input can produce different ionization levels in different months/seasons. The yearly method simply averages the observations of different seasons, leading to a biased yearly NmF2-EUV relation, which will further affect the estimation of the ionospheric hysteresis (different NmF2-EUV relation in the solar rising and declining phase). Also, the extraction of long-term trends in the ionosphere will be more uncertain if using a regression approach based on the biased NmF2-EUV relation. In conclusion, we suggest to do the analysis month by month (using monthly average method) to properly deal with the annual/seasonal variations of the ionosphere, and to obtain accurate estimation of the hysteresis and long-term trends. Though both the yearly and monthly methods were used in precedent works, the bias introduced by the yearly average method has not been fully recognized prior to this study.

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Section: Discussionmentioning

confidence: 95%