AUTHOR=Emmons Daniel J. , Wu Dong L. , Swarnalingam Nimalan , Ali Ashar F. , Ellis Joseph A. , Fitch Kyle E. , Obenberger Kenneth S. 

TITLE=Improved models for estimating sporadic-E intensity from GNSS radio occultation measurements

JOURNAL=Frontiers in Astronomy and Space Sciences

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/astronomy-and-space-sciences/articles/10.3389/fspas.2023.1327979

DOI=10.3389/fspas.2023.1327979

ISSN=2296-987X

ABSTRACT=<p>Several models for estimating sporadic-E intensity from Global Navigation Satellite System (GNSS) radio occultation (RO) observation have previously been developed using a single perturbation or intensity parameter, such as phase-based total electron content (TEC) or the amplitude-based S<sub>4</sub> index. Here, we outline two new models that use a combination of phase and amplitude parameters for the L<sub>1</sub> and L<sub>2</sub> signals. These models show a significant improvement over the baseline models used for comparison. Furthermore, the GNSS-RO parameters are compared with several different ionosonde intensity parameters including the direct foEs and fbEs measurements along with the metallic-ion based fo<inline-formula id="inf1"><mml:math id="m1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="italic">μ</mml:mi></mml:math></inline-formula>Es and fb<inline-formula id="inf2"><mml:math id="m2" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="italic">μ</mml:mi></mml:math></inline-formula>Es parameters which account for the background E-region density. Interestingly, the phase-based <inline-formula id="inf3"><mml:math id="m3" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow><mml:mi mathvariant="italic">σ</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">ϕ</mml:mi></mml:mrow></mml:msub></mml:math></inline-formula> scintillation index shows the strongest correlation to foEs and fbEs while amplitude-based S<sub>4</sub> shows the strongest correlation to fo<inline-formula id="inf4"><mml:math id="m4" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="italic">μ</mml:mi></mml:math></inline-formula>Es and fb<inline-formula id="inf5"><mml:math id="m5" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="italic">μ</mml:mi></mml:math></inline-formula>Es. While the metallic-ion based fo<inline-formula id="inf6"><mml:math id="m6" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="italic">μ</mml:mi></mml:math></inline-formula>Es and fb<inline-formula id="inf7"><mml:math id="m7" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi mathvariant="italic">μ</mml:mi></mml:math></inline-formula>Es parameters are physically ideal for GNSS-RO observations, we show difficulties in practical implementation due to the reliance on a background E-region density estimate using a model such as the International Reference Ionosphere (IRI). Ultimately, we provide two improved sporadic-E intensity models that can be used for future GNSS-RO based studies along with a recommendation to compare against the ionosonde-based foEs parameter.</p>