Details

Autor(en) / Beteiligte

• Li, J. D.
• Harid, V.
• Spasojevic, M.
• Gołkowski, M.
• Inan, U. S.

Titel

Preferential amplification of rising versus falling frequency whistler mode signals

Ist Teil von

• Geophysical research letters, 2015-01, Vol.42 (2), p.207-214

Ort / Verlag

Washington: Blackwell Publishing Ltd

Erscheinungsjahr

2015

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Analysis of ground‐based ELF/VLF observations of injected whistler mode waves from the 1986 Siple Station experiment demonstrates the preferential magnetospheric amplification of rising over descending frequency‐time ramps. From examining conjugate region receptions of ±1 kHz/s frequency‐time ramps, we find that rising ramps generate an average total power 1.9 times higher than that of falling frequency ramps when both are observed during a transmission. And in 17% of receptions, only rising ramps are observed above the noise floor. Furthermore, the amplification ratio inversely correlates with the noise and total signal power. Using a narrowband Vlasov‐Maxwell numerical simulation, we explore the preferential amplification due to differences in linear growth rate as a function of frequency, relative to the frequency which maximizes the linear growth rate for a given anisotropy, and in nonlinear phase trapping. These results contribute to the understanding of magnetospheric wave amplification and the preference for structured rising elements in chorus. Key Points Rising frequency ramps amplify on average 1.9 times more than falling frequency ramps The linear growth rate as function of frequency controls initial amplification Higher initial growth leads to earlier onset, longer duration nonlinear growth