TY - JOUR
T1 - Observation of an MHD Alfvén vortex in the slow solar wind
AU - Roberts, O. W.
AU - Li, X.
AU - Alexandrova, O.
AU - Li, B.
N1 - Publisher Copyright:
©2016. American Geophysical Union. All Rights Reserved.
PY - 2016/6/15
Y1 - 2016/6/15
N2 - In the solar wind, magnetic field power spectra usually show several power laws. In this paper, magnetic field data from the Cluster mission during an undisturbed interval of slow solar wind are analyzed at 0.28 Hz, near the spectral break point between the ion inertial and dissipation/dispersion ranges. Assuming Taylor's frozen-in condition, it corresponds to a proton kinetic scale of kvA/Ωp∼0.38, where vA and Ωp are the Alfvén speed and proton angular gyrofrequency, respectively. Data show that the Cluster spacecraft passed through a series of wave packets. A strong isolated wave packet is found to be in accordance with the four Cluster satellites crossing an Alfvén vortex, a nonlinear solution to the incompressible MHD equations. A strong agreement is seen between the data from four satellites and a model vortex with a radius of the order of 40 times the local proton gyroradii. The polarization at different spacecraft is compared and is found to agree with the vortex model, whereas it cannot be explained solely by the linear plane wave approach.
AB - In the solar wind, magnetic field power spectra usually show several power laws. In this paper, magnetic field data from the Cluster mission during an undisturbed interval of slow solar wind are analyzed at 0.28 Hz, near the spectral break point between the ion inertial and dissipation/dispersion ranges. Assuming Taylor's frozen-in condition, it corresponds to a proton kinetic scale of kvA/Ωp∼0.38, where vA and Ωp are the Alfvén speed and proton angular gyrofrequency, respectively. Data show that the Cluster spacecraft passed through a series of wave packets. A strong isolated wave packet is found to be in accordance with the four Cluster satellites crossing an Alfvén vortex, a nonlinear solution to the incompressible MHD equations. A strong agreement is seen between the data from four satellites and a model vortex with a radius of the order of 40 times the local proton gyroradii. The polarization at different spacecraft is compared and is found to agree with the vortex model, whereas it cannot be explained solely by the linear plane wave approach.
UR - http://www.scopus.com/inward/record.url?scp=84965130489&partnerID=8YFLogxK
U2 - 10.1002/2015JA022248
DO - 10.1002/2015JA022248
M3 - Article
AN - SCOPUS:84965130489
SN - 2169-9380
VL - 121
SP - 3870
EP - 3881
JO - Journal of Geophysical Research: Space Physics
JF - Journal of Geophysical Research: Space Physics
IS - 5
ER -