Details

Autor(en) / Beteiligte

• Xia, Zhiyang
• Chen, Lunjin
• Horne, Richard B.
• Liu, Xu
• He, Jiabei
• Bortnik, Jacob

Titel

On the Wave‐Normal Distribution of Lightning‐Generated Whistlers and Their Propagation Modes

Ist Teil von

• Journal of geophysical research. Space physics, 2024-04, Vol.129 (4), p.n/a

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2024

Link zum Volltext

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• Observations from Van Allen Probes are analyzed to obtain the statistical wave normal distribution of lightning‐generated whistlers (LGWs). An automatic algorithm is developed to identify burst mode waveform data with LGW signals and analyze the wave polarization information for these LGW signals. The spatial distribution of the LGW occurrence and the probabilities of different propagation types demonstrate that most LGWs can be observed in the low L‐shell region (L < 3), where the dominant propagation type is oblique outward. Parallel propagation dominates in the high L‐shell region, but the LGW occurrence is very small. Additionally, a small group of oblique but inwardly propagating LGWs are observed at low altitudes (<0.2RE). A ray tracing simulation is performed not only to confirm predominant oblique and outward wave vectors in the vast region of the plasmasphere but also to verify the existence of these inward propagating LGW signals at low altitudes near the topside ionosphere. Plain Language Summary A fraction of broadband electromagnetic emissions produced by lightning strikes in the Earth's atmosphere can propagate through the ionosphere into the magnetosphere as lightning‐generated whistlers (LGWs). The LGW plays an important role in the electron scattering of the radiation belts, the efficiency of which highly depends on their wave normal angles and thus the propagation modes of the LGWs. In this study, we develop an algorithm to identify the burst mode waveform data from Van Allen Probes' observations that capture the LGW signals. Using these identified waveforms, we statistically study the wave normal distribution for LGWs in the inner magnetosphere. The results indicate that most LGWs are observed in the low altitude region (<2RE, RE is the Earth's radius) with an oblique, radially outward wave normal. In the high altitude region (∼3RE), parallel wave normals dominate, and in the very low altitude region (<0.2RE), the oblique inward wave normal exists. A ray tracing simulation is performed to confirm the dominant oblique wave normal of LGWs and the existence of inward wave normals caused by the great plasma density gradient in the very low altitude region. The results lead to our systematic understanding of LGWs and advance the predictive capability of radiation belts. Key Points Most lightning‐generated whistlers exhibit oblique and outward wave normal angles in the region of L < 3 In the very low altitude (<0.2RE) region, oblique and inward propagation modes of LGWs exist A ray tracing simulation confirms the dominant outward propagation and the existence of inward propagation