pyrfu.pyrf.dynamic_press#

pyrfu.pyrf.dynamic_press(n_s: DataArray, v_xyz: DataArray, specie: str | None = 'ions') → DataArray[source]#

Computes dynamic pressure.

\[P_{dyn} = n_s m_s |\mathbf{V}_s|^2\]

The bulk velocity is resampled to the times of the number density if they differ.

Parameters:

  • n_s (DataArray) – Time series of the number density of the specie [cm^{-3}].

  • v_xyz (DataArray) – Time series of the bulk velocity of the specie [km/s].

  • specie (str, Optional) – Specie ‘ions’ (protons) or ‘electrons’. Default ‘ions’.

Returns:

Time series of the dynamic pressure of the specie [nPa].

Return type:

DataArray

Examples

>>> from pyrfu import mms, pyrf

Time interval

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

Spacecraft index

>>> mms_id = 1

Load ion bulk velocity and remove spintone

>>> v_xyz_i = mms.get_data("vi_gse_fpi_fast_l2", tint, mms_id)
>>> st_xyz_i = mms.get_data("sti_gse_fpi_fast_l2", tint, mms_id)
>>> v_xyz_i = v_xyz_i - st_xyz_i

Ion number density

>>> n_i = mms.get_data("ni_fpi_fast_l2", tint, mms_id)

Compute dynamic pressure

>>> p = pyrf.dynamic_press(n_i, v_xyz_i, specie="ions")