Spherical Bessel y
From specialfunctionswiki
The spherical Bessel function of the second kind is $$y_{\nu}(z)=\sqrt{\dfrac{\pi}{2z}} Y_{\nu+\frac{1}{2}}(z),$$ where $Y_{\nu}$ denotes the Bessel function of the second kind.
Domain coloring of $y_0$.
Properties
Relationship between spherical Bessel y and cosine
References
Spherical Bessel $y_{\nu}$