Radially Full Reflection of Fast Magnetosonic Waves Near the Cut‐Off Frequency

Abstract

Fast magnetosonic (MS) waves have been found to propagate mainly in the radial direction inside the plasmasphere. One main topic about the radial propagation of MS waves is whether they would propagate down to the ground or be reflected at some regions. Since WKB assumption might become invalid near the reflection point (if the reflection happens), an analytic approach has been utilized to investigate the propagation behavior of MS waves in this study. It is found that as MS waves propagate inward into the Earth, they might reach the cut‐off regions when their frequencies become close to the cut‐off frequency. Moreover, as demonstrated by our theoretical model, the behavior of MS waves around these regions can be described by the Airy's equation. Our results find that MS waves would be fully reflected near the cut‐off point, since only evanescent waves are allowed in the cut‐off regions.

Duct Effect of Magnetic Structures on Whistler Waves

“…The total reflection at $${q}_{j}(x)=0$$ in the x direction can be described by the Airy equation and its analytical solutions, as has been demonstrated by Yu et al. (2021). Other couplings can also occur between $$\pm {q}_{1}$$ and $$\pm {q}_{2}$$, even when not connected.…”

Modeling the Propagation of Fast Magnetosonic Waves and Their Conversion to Electromagnetic Ion Cyclotron Waves at Low L Shells

“…MS waves can propagate both radially and azimuthally (e.g., Chen & Thorne, 2012;Hanzelka et al, 2022;Kasahara et al, 1994;Němec et al, 2013;Santolík et al, 2016;, and across the plasmapause into the plasmasphere when excited outside of the plasmasphere (e.g., Liu et al, 2018;Min et al, 2019;Xiao, Zhou, et al, 2015). MS waves can further propagate to extremely low L shells ( 𝐴𝐴 𝐴𝐴 𝐴 2.0 ) (e.g., Miyoshi et al, 2019;Yu et al, 2021;Zhang et al, 2021) with some even reaching the topside ionosphere observed by DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) (e.g.,…”

“…MS waves can propagate both radially and azimuthally (e.g., Chen & Thorne, 2012; Hanzelka et al., 2022; Kasahara et al., 1994; Němec et al., 2013; Santolík et al., 2016; Xiao, Zhou, et al., 2012), and across the plasmapause into the plasmasphere when excited outside of the plasmasphere (e.g., Liu et al., 2018; Min et al., 2019; Xiao, Zhou, et al., 2015). MS waves can further propagate to extremely low L shells ($$L< 2.0$$) (e.g., Miyoshi et al., 2019; Yu et al., 2021; Zhang et al., 2021) with some even reaching the topside ionosphere observed by DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) (e.g., Hanzelka et al., 2022; Němec et al., 2016; Santolík et al., 2016). Geomagnetic field strength increases as MS waves propagate toward the Earth and the effects of heavy ions on the propagation start becoming important when the wave frequency becomes lower than the local proton cyclotron frequency.…”

“…Geomagnetic field strength increases as MS waves propagate toward the Earth and the effects of heavy ions on the propagation start becoming important when the wave frequency becomes lower than the local proton cyclotron frequency. MS waves may go through polarization reversal during inward propagation (e.g., Santolík et al., 2016) and then reflect away from the Earth (e.g., Gurnett & Burns, 1968; Yu et al., 2021).…”

Effects of Cold Plasma on the Mode Conversion From Fast Magnetosonic Wave to Electromagnetic Ion Cyclotron Wave in the Inner Plasmasphere

“…MS waves usually propagate as whistler mode with very large normal angles (e.g., Boardsen et al., 2016; Russell et al., 1970; Stix, 1992) and both radial and azimuthal propagation (e.g., Chen & Thorne, 2012; Hanzelka et al., 2022; Liu et al., 2018; Min et al., 2019; Santolík et al., 2016; Xiao et al., 2012b, 2015b) may be affected by the gradient of electron density. The effects of ions become of significance when MS waves propagate to the location where the frequency is around or below the local proton cyclotron frequency (e.g., Miyoshi et al., 2019; Santolík et al., 2016; Yu et al., 2021). EMIC waves usually propagate along the magnetic field line to higher latitudes after excitation near the equatorial region (e.g., Loto'aniu et al., 2005; Zhang et al., 2014; Q. H. Zhou et al., 2013).…”