Harmonic waves and sheath rectification in type III solar radio bursts
2014 (English)In: J GEOPHYS RES-SPACE, ISSN 2169-9380, Vol. 119, no 2, 723-741 p.Article in journal (Refereed) Published
In type III solar radio bursts and planetary foreshocks, Langmuir waves are produced by electron beams and converted partially to radio waves by linear and nonlinear processes. Lower amplitude second harmonic electric fields are observed simultaneously during the most intense Langmuir wave events in type III source regions. The electric fields at the harmonic frequencies can arise from various mechanisms, such as radio wave emission by either coalescence or antenna mechanisms, nonlinear currents, harmonics of Langmuir waves, electron trapping in Langmuir wave potentials, and Langmuir wave rectification at the sheath surrounding the spacecraft, or they can result from instrumental harmonics. In this paper the relative powers and electric field vectors of Langmuir waves and the harmonic fields are compared for multiple events. The structure of the harmonic field is shown to be determined by the Langmuir waveform, but the harmonic field direction is typically closely aligned with the solar wind flow. The magnitude, structure, and orientation of the harmonic fields is used to determine which processes are responsible. It is shown that the dominant process generating the observed harmonic fields is Langmuir wave rectification at the sheath surrounding the spacecraft. Key Points <list list-type="bulleted"> <list-item id="jgra50855-li-0001">Intense Langmuir waves and harmonic fields are observed simultaneously <list-item id="jgra50855-li-0002">Harmonic fields are primarily produced by sheath rectification <list-item id="jgra50855-li-0003">Some evidence for nonlinear currents is found
Place, publisher, year, edition, pages
2014. Vol. 119, no 2, 723-741 p.
radio bursts, Langmuir waves, harmonic waves
Fusion, Plasma and Space Physics
IdentifiersURN: urn:nbn:se:uu:diva-227210DOI: 10.1002/2013JA019317ISI: 000333041000007OAI: oai:DiVA.org:uu-227210DiVA: diva2:729643