On the 1/ f Spectrum in the Solar Wind and Its Connection with Magnetic Compressibility

Research paper by L. Matteini, D. Stansby, T. S. Horbury, C. H. K. Chen

Indexed on: 21 Dec '18Published on: 18 Dec '18Published in: The astrophysical journal. Letters


We discuss properties of Alfvénic fluctuations with large amplitude in plasmas characterized by low magnetic field compression. We note that in such systems power laws cannot develop with arbitrarily steep slopes at large scales, i.e., when ##IMG## [http://ej.iop.org/images/2041-8205/869/2/L32/apjlaaf573ieqn1.gif] {$ \delta {\boldsymbol{B}} $} becomes of the order of the background field ##IMG## [http://ej.iop.org/images/2041-8205/869/2/L32/apjlaaf573ieqn2.gif] {$ {\boldsymbol{B}} $} . In such systems there is a scale l 0 at which the spectrum has to break due to the condition of weak compressibility. A very good example of this dynamics is offered by solar wind fluctuations in Alfvénic fast streams, characterized by the property of constant field magnitude. We show here that the distribution of ##IMG## [http://ej.iop.org/images/2041-8205/869/2/L32/apjlaa...] {$\delta B= \delta {\boldsymbol{B}} $}