The 1920 paper “Ionization in the Solar Chromosphere” by M. Saha, published in the Philosophical Magazine, is a seminal work where Saha applied his newly developed theory of thermal ionization to explain the composition of the solar chromosphere. The paper demonstrated that the high-level chromospheric spectrum is primarily composed of ionized atoms of elements like calcium, barium, and strontium. This theory linked the spectral classes of stars to their temperatures and provided a physical basis for the classification of stellar spectra, which was a major advancement in astrophysics. [1, 2, 3, 4]
Key Aspects of the Paper
- The Saha Ionization Equation: This equation, derived from combining quantum and statistical mechanics, relates the ionization state of a gas to its temperature and pressure. [2, 4]
- Application to the Sun: Saha applied this theory to the solar chromosphere, showing that the ionization of elements like calcium and barium explains the observed spectral lines in that region. [1]
- Composition of the Chromosphere: The paper concluded that the high-level solar chromosphere is predominantly composed of ionized atoms of various elements, including calcium, barium, strontium, scandium, titanium, and iron. [1]
- Impact on Stellar Spectra: The work provided a physical theory for understanding stellar spectra, allowing astronomers to accurately determine stellar temperatures based on their spectral classes. [2, 5]
Significance
This 1920 paper and the accompanying theory established Meghnad Saha as a pioneer in the field of thermal ionization. His work revolutionized the understanding of stellar atmospheres by providing a quantitative framework for interpreting their spectra. [2, 3, 5, 6]
[1] https://www.degruyter.com/document/doi/10.4159/harvard.9780674366688.c42/pdf
[2] https://en.wikipedia.org/wiki/Meghnad_Saha
[3] https://link.springer.com/10.1007/978-1-4419-9917-7_1209
[4] https://en.wikipedia.org/wiki/Saha_ionization_equation
[5] https://royalsocietypublishing.org/doi/10.1098/rspa.1940.0041
[6] https://www.observerbd.com/news.php?id=25186
M. Saha, “Ionization in the solar chromosphere,” Philosophical Magazine,
1920.
Hypersonic Plasma Sheath Effects on RF Links:
A Lightweight Physics-Informed Model with
Band-Wise Attenuation and Usable Windows
Benjamin J. Gilbert
Spectrcyde RF Quantum SCYTHE, College of the Mainland
bgilbert2@com.edu
ORCID: https://orcid.org/0009-0006-2298-6538
Abstract—We present a compact, physics-informed model of
plasma-sheath formation around hypersonic vehicles and its
impact on RF communication and radar links. The model couples
a standard-atmosphere profile with simplified Saha ionization,
Chapman–Enskog collision rates, and shock-stand-off scaling (Fay–
Riddell; Hayes–Probstein) to estimate electron density, plasma
frequency, collision frequency, sheath thickness, and band-wise
attenuation. We summarize blackout regimes and suggest usable
RF windows above the local plasma frequency. The code runs in
milliseconds and auto-generates figures/tables for reproducible
builds.
Index Terms—Hypersonic, Plasma sheath, Communication
blackout, Plasma frequency, RF attenuation, Saha ionization,
Chapman–Enskog
REFERENCES
[1] U.S. Committee on Extension to the Standard Atmosphere, “U.s. standard
atmosphere, 1976,” National Oceanic and Atmospheric Administration,
Tech. Rep., 1976.
[2] M. Saha, “Ionization in the solar chromosphere,” Philosophical Magazine,
1920.
[3] S. Chapman and T. G. Cowling, The Mathematical Theory of Non-Uniform
Gases, 3rd ed. Cambridge Univ. Press, 1970.
[4] J. A. Fay and F. R. Riddell, “Theory of stagnation point heat transfer in
dissociated air,” Journal of the Aeronautical Sciences, 1958.