The difference in the group refractive index is significant when (X) approaches 1, i.e., near the reflection level.
The Doppler shift caused by the advection mechanism can be interpreted as caused by the movement of the reflection level with velocity v, which is calculated using the simple formula: Delta f = - 2ffrac{v}{c}.
In Fig. 2c, the value of ( {n}_X^2 ) has a zero before the reflection point of the O-mode waves (z = 184.3 km, the black circle shown in the figure), indicating that the X-mode waves do not usually reach the reflection level of the O-mode waves.
The cusp signature in ionograms is ascribed to the increased propagation delay in a thin slab of plasma just below the reflection level ((Xapprox 1)) when the electron density gradient is reduced (or the thickness of this slab increases) at the density ledge (Maruyama et al. 2016a) formed by an acoustic wave.
The Doppler sounding with continuous high-frequency (HF) radio waves detects the periodic fluctuation of phase length associated with the electron density perturbation near the reflection level (Yuen et al. 1969; Wolcott et al. 1984; Tanaka et al. 1984; Artru et al. 2004; Chum et al. 2012, 2016).
Thus, the international solution to assessing reflection levels among medical students is not found, but the evidence-based discussions hopefully continue with underlying positive – as well as – negative findings.
Future research might investigate which kinds of questions can be asked to challenge students towards reflection levels slightly above the level on which they perform and examine the effectiveness of challenging students towards higher reflection levels.
Reflection is a phenomenon that changes dynamically during discussions, when participants move on different reflection levels (Ojala & Venninen, 2011).
And, linked to that, do students who receive feedback comments, (1) tailored to their reflection levels, (2) formulated as questions to lift them to slightly higher reflection levels, and (3) formulated in a positive tone, improve their reflective writing?
It is shown that based on Rindel's approximation one may determine some substantial information about sound reflection from the panels i.e. the value of upper limit frequency as well as the relative sound reflection level.
