The role of high frequency oscillations in the penetration of plasma clouds across magnetic boundaries
2005 (English)In: Physics of Plasmas, ISSN 1070-664X, Vol. 12, no 1Article in journal (Refereed) Published
Experiments are reported where a collissionfree plasma cloud penetrates a magnetic barrier by self-polarization. Three closely related effects, all fundamental for the penetration mechanism, are studied quantitatively: (1) anomalous fast magnetic field penetration (two orders of magnitude faster than classical), (2) anomalous fast electron transport (three orders of magnitude faster than classical and two orders of magnitude faster than Bohm diffusion), and (3) the ion energy budget as ions enter the potential structure set up by the self-polarized plasma cloud. It is concluded that all three phenomena are closely related and that they are mediated by highly nonlinear oscillations in the lower hybrid range, driven by a strong diamagnetic current loop which is set up in the plasma in the penetration process. The fast magnetic field penetration occurs as a consequence of the anomalous resistivity caused by the wave field and the fast electron transport across magnetic field lines is caused by the correlation between electric field and density oscillations in the wave field. It is also found that ions do not lose energy in proportion to the potential hill they have to climb, rather they are transported against the dc potential structure by the same correlation that is responsible for the electron transport. The results obtained through direct measurements are compared to particle in cell simulations that reproduce most aspects of the high frequency wave field.
Place, publisher, year, edition, pages
2005. Vol. 12, no 1
hybrid-drift instability, ion-beam propagation, field, transverse, injection, simulations, turbulence, tokamak, beta, gun
IdentifiersURN: urn:nbn:se:kth:diva-14516DOI: 10.1063/1.1812276ISI: 000226864500017ScopusID: 2-s2.0-20444491203OAI: oai:DiVA.org:kth-14516DiVA: diva2:332557
QC 201005252010-08-052010-08-05Bibliographically approved