pyrfu.pyrf.st_diff module#
- pyrfu.pyrf.st_diff.st_diff(r_mms, b_mms, lmn)[source]#
Computes velocity of the structure using spatio-temporal derivative method [13] [14] as
\[V_{str}^{LMN} = -d_t B^{LMN}\left [\nabla^{LMN} B^{LMN}\right]^T \left [ S^{LMN} \right ]^{-1}\]where \(B^{LMN}\), \(\nabla^{LMN}B^{LMN}\), \(S^{LMN}\) and \(V_{str}^{LMN}\) are namely the magnetic field, its gradient, its rotation rate tensor and the velocity of the structure in the LMN coordinates system.
- Parameters:
r_mms (list of xarray.DataArray) – Spacecraft positions.
b_mms (list of xarray.DataArray) – Background magnetic field.
lmn (ndarray) – Structure coordinates system.
- Returns:
v_str – Velocity of the structure in its coordinates system.
- Return type:
References
[13]Shi, Q. Q., Shen, C., Pu, Z. Y., Dunlop, M. W., Zong, Q. G., Zhang, H., et al. (2005), Dimensional analysis of observed structures using multipoint magnetic field measurements: Application to Cluster. Geophysical Research Letters, 32, L12105. doi : https://doi.org/10.1029/2005GL022454.
[14]Shi, Q. Q., Shen, C., Dunlop, M. W., Pu, Z. Y., Zong, Q. G., Liu, Z. X., et al. (2006), Motion of observed structures calculated from multi‐point magnetic field measurements: Application to Cluster. Geophysical Research Letters, 33, L08109. doi : https://doi.org/10.1029/2005GL025073.