pyrfu.pyrf.calc_dng module#

pyrfu.pyrf.calc_dng.calc_dng(p_xyz: DataArray) → DataArray[source]#

Computes Aunai’s agyrotropy coefficient.

Aunai’s agyrotropy is [15]

\[D_{ng} = \frac{\sqrt{8 (P_{12}^2 + P_{13}^2 + P_{23}^2)}} {P_\parallel + 2 P_\perp}\]
Parameters:

p_xyz (DataArray) – Time series of the pressure tensor

Returns:

Time series of the agyrotropy coefficient of the specie.

Return type:

DataArray

Raises:

  • TypeError – If input is not a xarray.DataArray.

  • ValueError – If input is not a time series of a tensor (n_time, 3, 3).

References

[15]

Aunai, N., M. Hesse, and M. Kuznetsova (2013), Electron nongyrotropy in the context of collisionless magnetic reconnection, Phys. Plasmas, 20(6), 092903, doi: https://doi.org/10.1063/1.4820953.

Examples

>>> from pyrfu import mms, pyrf

Time interval

>>> tint = ["2019-09-14T07:54:00.000","2019-09-14T08:11:00.000"]

Spacecraft index

>>> ic = 1

Load magnetic field and electron pressure tensor

>>> b_xyz = mms.get_data("b_gse_fgm_srvy_l2", tint, 1)
>>> p_xyz_e = mms.get_data("pe_gse_fpi_fast_l2", tint, 1)

Rotate electron pressure tensor to field aligned coordinates

>>> p_fac_e_pp = mms.rotate_tensor(p_xyz_e, "fac", b_xyz, "pp")

Compute agyrotropy coefficient

>>> d_ng_e = pyrf.calc_dng(p_fac_e_pp)