A study of quasi-thermal noise and shot noise in space plasmas

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A study of quasi-thermal noise and shot noise in space plasmas

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dc.contributor.author Martinović, Mihailo
dc.date.accessioned 2017-05-17T17:52:14Z
dc.date.available 2017-05-17T17:52:14Z
dc.date.issued 2016-10-20
dc.identifier.uri http://hdl.handle.net/123456789/4476
dc.description.abstract The quasi-thermal noise spectroscopy is an accurate method of determination of density and temperature in space plasmas. When an electric antenna is immersed into a plasma, it is able to measure electrostatic uctuations caused by the thermal motion of plasma particles. These uctuations are detected as the power spectral density at the antenna terminals, observing a spectrum at frequencies comparable to the electron plasma frequency for both electrons and protons, since the proton signal is strongly Doppler-shifted towards higher frequencies due to the solar wind drift velocity. Beside inducing the uctuating electric eld, some of the electrons are impacting the antenna surface, causing disturbances of the antenna electric potential. The signal caused by this population is directly proportional to the ux of plasma electrons impacting the antenna and is dominant if the antenna has a large surface area. In this work, we use the orbit limited theory to calculate the incoming particle ux for a non-thermal plasma described by velocity distribution function, commonly measured in the solar wind. The increase in the particle collection by cylindrical and spherical objects is quanti ed and presented as a function of the surface electrostatic potential and the fraction of supra-thermal particles. Including these results into the theory has turned out to be absolutely necessary for accurate measurements of the plasma parameters whenever the shot noise is the dominant component in the power spectrum. This is the case for STEREO because the impact noise is overwhelming on this probe, due to the presence of short and thick antennas. The comprehensive study of data on this mission is motivated by the fact that the electron analyzers are malfunctioning since launch and no information on thermal electrons is available. Results obtained are veri ed by comparing with the results from Wind, showing a good match between the values measured by the two spacecraft. Uncertainties of the measurements are determined by the uncertainties of the instruments used and are estimated to be around 40%. The nal outcome of this work will be establishing a database of the electron moments in both STEREO A and B that will be covering the entire duration of the mission. In the second part of the thesis, we use the kinetic approach to expand the theory of the quasi-thermal noise to plasmas where electron-neutral collisions play a dominant role. This technique is able to measure the electron density, temperature and the collision frequency as independent parameters using the wide frequency range both below and above the plasma frequency, if the ratio of the collisional to plasma frequency is not smaller than 0.1. The results presented here have can be potentially applied in laboratory plasmas and unmagnetized ionospheres, while at the ionosphere of Earth their use is limited to low frequencies due to the presence of the magnetic field. en_US
dc.description.provenance Submitted by Slavisha Milisavljevic (slavisha) on 2017-05-17T17:52:14Z No. of bitstreams: 1 MMartinovic_Thesis.pdf: 16421009 bytes, checksum: c04c75cae465146575a361b4e808405a (MD5) en
dc.description.provenance Made available in DSpace on 2017-05-17T17:52:14Z (GMT). No. of bitstreams: 1 MMartinovic_Thesis.pdf: 16421009 bytes, checksum: c04c75cae465146575a361b4e808405a (MD5) Previous issue date: 2016-10-20 en
dc.language.iso en en_US
dc.title A study of quasi-thermal noise and shot noise in space plasmas en_US
mf.subject.area astrophysics en_US
mf.contributor.committee Vinas, Adolfo Figueroa
mf.contributor.committee Lamy, Herve
mf.contributor.committee Purić, Jagoš
mf.contributor.committee Jovanović, Dušan
mf.contributor.committee Sauty, Christophe
mf.contributor.committee Maksimović, Milan
mf.contributor.committee Zaslavsky, Arnaud
mf.contributor.committee Šegan, Stevo
mf.university.faculty Mathematical Faculty en_US
mf.document.pages 102 en_US
mf.document.location Beograd en_US
mf.document.genealogy-project No en_US
mf.university Belgrade University en_US

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