Influence of Solar Wind Dynamic Pressure on Distribution of Whistler Mode Waves Based on Van Allen Probe Observations

Abstract

In this study, the effect of solar wind dynamic pressure (PSW) on the global distribution of whistler mode waves (including chorus and hiss waves) while the absence of substorm activity is investigated using the data originating from the Van Allen Probes for nearly 5 years. After the effect of substorm activity is excluded, our statistical results indicate that the hiss and chorus waves exhibit different characteristics with the increase of PSW. The amplitudes of chorus waves increase on the dayside with the PSW strengthen, which can be explained through the local enhanced electron temperature anisotropy and more intense emission for the chorus in the inner magnetosphere. Interestingly, the amplitudes of hiss wave are reduced with the increase of PSW. The weakness of hiss waves can be attributed to electrons at high L‐shells which drift out of the magnetosphere on the dayside when the magnetopause's position decreases. It can significantly result in a reduced chorus inside the magnetopause that will evolve into hiss waves. In addition, the upper and lower cutoff frequencies of hiss waves will increase. This new finding is critical for understanding the generation and evolution of whistler mode waves and its responses to the intensity of PSW.

Prompt responses of magnetospheric whistler-mode waves to solar wind dynamic pressure pulses

“…In contrast, plasmaspheric hiss mainly disappeared/weakened on the dayside and intensified on the nightside, which cannot be explained solely by the variations of source chorus. Such different dependences of chorus and plasmaspheric hiss on the solar wind dynamic pressure have also been reported recently by Tang et al (2023). Through simple ray tracing modeling, Yue et al (2017) found that a more stretched magnetic field configuration on the nightside caused by shock compression favors the entry of chorus waves with more fieldaligned wave normal into the plasmasphere, which are generally the majority of observed chorus waves in the equatorial region (Burton and Holzer, 1974;Goldstein and Tsurutani, 1984;Santolík et al, 2014a;Santolík et al, 2014b;Hartley et al, 2019).…”

Statistical Properties of Whistler-mode Waves in the Dayside Terrestrial Space: MMS Observations

“…under Different P sw Levels Solar wind dynamic pressure, P sw , is known to be an important parameter impacting the transmission of energy within the magnetosphere and the configuration of its magnetic field. To quantitatively assess the impact of P sw on whistlermode waves in dayside terrestrial space, we first sort the P sw into three levels based on the variations in solar wind dynamic pressure (Tang et al 2023): (a) weak: P sw 1.5 nPa; (b) moderate: 1.5 nPa <P sw < 3 nPa; and (c) strong: P sw 3 nPa.…”