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1.	Malaspina, David M., et al. (författare) Langmuir wave harmonics due to driven nonlinear currents 2013 Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 118:11, s. 6880-6888 Tidskriftsartikel (refereegranskat)abstract The conversion of Langmuir waves into electromagnetic radiation near the local plasma frequency (f(pe)) and twice the local plasma frequency (2f(pe)) occurs in diverse heliospheric environments including along the path of type III radio bursts, at interplanetary shocks, and in planetary foreshocks. This radiation has the potential to act as a probe of remote plasma conditions, provided that the conversion mechanism is well understood. One candidate conversion mechanism is the antenna radiation of localized Langmuir waves. Antenna radiation near 2f(pe) requires the presence of nonlinear currents at 2f(pe). In this work, properties of these currents are predicted from theory and compared with observations of Langmuir wave electric fields made using the WAVES instrument on the STEREO spacecraft. It is found that the observed frequency structure, polarization, and wave number ratio are consistent with nonlinear current predictions, once electric fields near 2f(pe)consistent with sheath effects are taken into account.

Malaspina, David M., et al. (författare)
Langmuir wave harmonics due to driven nonlinear currents
2013
Ingår i: Journal of Geophysical Research - Space Physics. - 2169-9380 .- 2169-9402. ; 118:11, s. 6880-6888
Tidskriftsartikel (refereegranskat)abstract
- The conversion of Langmuir waves into electromagnetic radiation near the local plasma frequency (f(pe)) and twice the local plasma frequency (2f(pe)) occurs in diverse heliospheric environments including along the path of type III radio bursts, at interplanetary shocks, and in planetary foreshocks. This radiation has the potential to act as a probe of remote plasma conditions, provided that the conversion mechanism is well understood. One candidate conversion mechanism is the antenna radiation of localized Langmuir waves. Antenna radiation near 2f(pe) requires the presence of nonlinear currents at 2f(pe). In this work, properties of these currents are predicted from theory and compared with observations of Langmuir wave electric fields made using the WAVES instrument on the STEREO spacecraft. It is found that the observed frequency structure, polarization, and wave number ratio are consistent with nonlinear current predictions, once electric fields near 2f(pe)consistent with sheath effects are taken into account.

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