Skip to content

Supported variables and data reducers

Markus Battarbee edited this page Mar 2, 2022 · 7 revisions

Reading variables from .vlsv files

Analysator supports reading multiple different types of variables:

  • MPIgrid variables
  • FSgrid variables
  • variables directly available in the data files
  • variables generated via receipes from the data file variables (named, somewhat incorrectly, datareducers)

Vlasiator variable naming scheme

In Vlasiator versions before V5, variables were always saved on the DCCRG/MPI/Vlasov grid, and as such, only a single naming scheme was required. With the introduction of Vlasiator V5, variables could also be saved on the FSgrid. When the new ionosphere will be implemented, that can also be saved to on its own grid. To differentiate between the different grids, a naming scheme was introduced where a prefix defines the grid type:

  • No prefix: old pre-V5 data
  • prefix vg_: Vlasov/MPI/DCCRG grid
  • prefix fg_: fieldsolver/FSgrid
  • prefix ig_: ionosphere grid

Multipop naming (version 4 onwards)

Some variables are directly connected to a given particle species, with the variable name having a particle species prefix. For example: ´proton/rho´ or proton/vg_rho for V4 and V5 outputs respectively. Note that multipop outputs are always on the Vlasov grid, but still have the vg_ prefix after the particle species name. Some variable such as rho and blocks which are directly connected to particle species are availabe without the population identifier in datafiles from version 3 and earlier.

Vlasiator variable correspondences

The below tables list variable names used in different versions of Vlasiator proper (updated: 3.6.2021). A blank entry in a corresponding column indicates this variable is not available. Some debugging variables such as field derivatives have been omitted from the table.

FSgrid variables Corresponding Vlasov grid variable in older versions
fg_b B
fg_b_background background_B
fg_b_perturbed perturbed_B
fg_b_vol B_vol
fg_e E
fg_e_hall_?? EXHALL_???_???
fg_e_vol E_vol
fg_rhom Rhom
fg_rhoq Rhoq
fg_v V
fg_pressure Pressure
fg_maxdt_fieldsolver max_fields_dt
fg_rank FSgrid_rank
fg_amr_level
fg_boundarytype FSgrid_boundaryType
fg_boundarylayer Boundary_layer
V5 Vlasov grid variables Older Vlasov grid variables
vg_rhom Rhom
vg_rhoq Rhoq
vg_v V
vg_pressure Pressure
Blocks
vg_b_vol B_vol
 vg_b_background_vol BGB_vol
vg_b_perturbed_vol PERB_vol
E
vg_e_vol E_vol
vg_e_gradpe EGRADPE
vg_f_saved fSaved
vg_maxdt_acceleration max_v_dt
vg_maxdt_translation max_r_dt
vg_rank MPI_rank
vg_loadbalance_weight LB_weight
vg_boundarytype Boundary_type
vg_boundarylayer Boundary_layer
Per-population variables Older per-population variables Older pre-multipop variables
populations/vg_rho populations/rho
populations/vg_v populations/V
populations/vg_rho_thermal populations/RhoNonBackstream
populations/vg_rho_nonthermal populations/RhoBackstream
populations/vg_v_thermal populations/VNonBackstream
populations/vg_v_nonthermal populations/VBackstream
populations/vg_effectivesparsitythreshold populations/EffectiveSparsityThreshold
populations/vg_rho_loss_adjust populations/rho_loss_adjust
populations/vg_energydensity populations/EnergyDensity
populations/vg_precipitationdifferentialflux populations/PrecipitationDiffFlux
populations/vg_maxdt_acceleration populations/MaxVdt
populations/vg_maxdt_translation populations/MaxRdt
populations/vg_blocks populations/Blocks
populations/vg_acceleration_subcycles populations/acc_subcycles
populations/vg_ptensor_diagonal populations/PTensorDiagonal
populations/vg_ptensor_offdiagonal populations/PTensorOffDiagonal
populations/vg_ptensor_nonthermal_diagonal populations/PTensorBackstreamDiagonal
populations/vg_ptensor_nonthermal_offdiagonal populations/PTensorBackstreamOffDiagonal
populations/vg_ptensor_thermal_diagonal populations/PTensorNonBackstreamDiagonal
populations/vg_ptensor_thermal_offdiagonal populations/PTensorNonBackstreamOffDiagonal

Analysator datareducers

Post-processed derived variables (called somewhat mistakenly datareducers) are available in analysator. One limitation is that in current versions of analysator (as of March 2022) all datareducers require Vlasov grid variables as they work with CellID lists. Also, datareducers do not support spatial or temporal derivatives. However, both use of FSgrid variables and spatial and temporal derivatives in plotting routines is possible via expressions and external functions as called by plot_colormap and other such plotting routines (see also plot_helpers.py).

The up-to-date list of datareducers can always be found in pyVlsv/reduction.py

List of datareducers for Vlasiator versions 1...4. Note: If several populations exist for a v4 multipop run, temperature reducers are incorrect. If the value is available directly instead of as a datareducer, that name is listed instead in parathentheses. If it is available through multipop datareducers, it is shown with "mpop".

v5 datareducer v1...4 datareducer explanation
(vg_v) v velocity
vg_vms vms magnetosonic speed
vg_vs vs sound speed
vg_va va Alfvén speed
vg_ma ma Alfvén Mach number
vg_mms mms magnetosonic Mach number
vg_di di Ion inertial length
vg_v_parallel vparallel V parallel to B
vg_v_perpendicular vperpendicular V perpendicular to B
"mpop" vparallelbackstream non-thermal proton V, parallel to B
"mpop" vperpendicularbackstream non-thermal proton V, perpendicular to B
"mpop" vparallelnonbackstream thermal proton V, parallel to B
"mpop" vperpendicularnonbackstream thermal proton V, perpendicular to B
vg_e_parallel eparallel E component parallel to B
vg_e_perpendicular eperpendicular E component perpendicular to B
vg_pdyn pdyn dynamic pressure
vg_pdynx pdynx dynamic pressure from only x-directional velocity
vg_poynting poynting Poynting vector
n/a firstadiabatic mean first adiabatic invariant
 vg_egradpe_parallel n/a Electric field electron pressure gradient term parallel to B
 vg_egradpe_perpendicular n/a Electric field electron pressure gradient term perpendicular to B
 vg_restart_v restart_v estimate V from a restart file
 vg_restart_rho restart_rho estimate particle number density from a restart file
 vg_restart_rhom restart_rhom estimate mass density from a restart file
 vg_restart_rhoq restart_rhoq estimate charge density from a restart file

List of per-population datareducers for Vlasiator versions 4 and 5. For these multipop datareducers, replace pop with required population name. If pop/ is omitted, a sum over per-population values is provided.

v5 datareducer v4 datareducer explanation
pop/vg_rhom pop/rhom mass density
pop/vg_rhoq pop/rhoq charge density
pop/vg_pdyn pop/pdyn dynamic pressure
pop/vg_pdynx pop/pdynx dynamic pressure from only x-directional velocity
--------------------- -------------------- --------------------
pop/vg_v_parallel pop/vparallel V parallel to B
pop/vg_v_perpendicular pop/vperpendicular V perpendicular to B
pop/vg_v_parallel_nonthermal pop/vparallelbackstream non-thermal V, parallel to B
pop/vg_v_perpendicular_nonthermal pop/vperpendicularbackstream non-thermal V, perpendicular to B
pop/vg_v_parallel_thermal pop/vparallelnonbackstream thermal V, parallel to B
pop/vg_v_perpendicular_thermal pop/vperpendicularnonbackstream thermal V, perpendicular to B
--------------------- -------------------- --------------------
pop/vg_thermalvelocity pop/thermalvelocity estimate of thermal velocity
pop/vg_larmor pop/larmor estimate of representative Larmor radius
pop/vg_firstadiabatic pop/firstadiabatic estimate of first adiabatic invariant (old!)
pop/vg_gyroperiod pop/gyroperiod gyroperiod
pop/vg_plasmaperiod pop/plasmaperiod plasma period
pop/vg_precipitationintegralenergyflux n/a Integral energy flux of precipitating particles, estimate (several energy channels)
pop/vg_precipitationmeanenergy n/a Mean energy of channel for precipitating particle fluxes
--------------------- -------------------- --------------------
pop/vg_pressure pop/pressure pressure
pop/vg_ptensor pop/ptensor pressure tensor
pop/vg_ptensor_rotated pop/ptensorrotated pressure tensor, rotated to align with B
pop/vg_p_parallel pop/pparallel pressure, parallel to B
pop/vg_p_perpendicular pop/pperpendicular pressure, perpendicular to B
pop/vg_p_anisotropy pop/pperpoverpar ratio of perpendicular pressure to parallel pressure
--------------------- -------------------- --------------------
pop/vg_p_nonthermal pop/pbackstream pressure due to non-thermal particles
pop/vg_ptensor_nonthermal pop/ptensorbackstream pressure tensor due to non-thermal particles
pop/vg_ptensor_rotated_nonthermal pop/ptensorrotatedbackstream pressure tensor due to non-thermal particles, rotated to align with B
pop/vg_p_parallel_nonthermal pop/pparallelbackstream pressure component due to non-thermal particles, parallel to B
pop/vg_p_perpendicular_nonthermal pop/pperpendicularbackstream pressure component due to non-thermal particles, perpendicular to B
pop/vg_p_anisotropy_nonthermal pop/pperpoverparbackstream ratio of perpendicular pressure to parallel pressure for non-thermal particles
--------------------- -------------------- --------------------
pop/vg_p_thermal pop/pnonbackstream pressure due to thermal particles
pop/vg_ptensor_thermal pop/ptensornonbackstream pressure tensor due to thermal particles
pop/vg_ptensor_rotated_thermal pop/ptensorrotatednonbackstream pressure tensor due to thermal particles, rotated to align with B
pop/vg_p_parallel_thermal pop/pparallelnonbackstream pressure component due to thermal particles, parallel to B
pop/vg_p_perpendicular_thermal pop/pperpendicularnonbackstream pressure component due to thermal particles, perpendicular to B
pop/vg_p_anisotropy_thermal pop/pperpoverparnonbackstream ratio of perpendicular pressure to parallel pressure for thermal particles
--------------------- -------------------- --------------------
pop/vg_temperature pop/temperature temperature
pop/vg_ttensor pop/ttensor temperature tensor
pop/vg_ttensor_rotated pop/ttensorrotated temperature tensor, rotated to align with B
pop/vg_t_parallel pop/tparallel temperature, parallel to B
pop/vg_t_perpendicular pop/tperpendicular temperature, perpendicular to B
--------------------- -------------------- --------------------
pop/vg_t_nonthermal pop/tbackstream temperature of non-thermal particles
pop/vg_ttensor_nonthermal pop/ttensorbackstream temperature tensor of non-thermal particles
pop/vg_ttensor_rotated_nonthermal pop/ttensorrotatedbackstream temperature tensor of non-thermal particles, rotated to align with B
pop/vg_t_parallel_nonthermal pop/tparallelbackstream temperature component of non-thermal particles, parallel to B
pop/vg_t_perpendicular_nonthermal pop/tperpendicularbackstream temperature component of non-thermal particles, perpendicular to B
pop/vg_t_thermal pop/tnonbackstream temperature of thermal particles
--------------------- -------------------- --------------------
"pop/vg_ttensor_thermal pop/ttensornonbackstream temperature tensor of thermal particles
pop/vg_ttensor_rotated_thermal pop/ttensorrotatednonbackstream temperature temperature tensor of thermal particles, rotated to align with B
pop/vg_t_parallel_thermal pop/tparallelnonbackstream temperature component of thermal particles, parallel to B
pop/vg_t_perpendicular_thermal pop/tperpendicularnonbackstream temperature component of thermal particles, perpendicular to B
--------------------- -------------------- --------------------
pop/vg_t_anisotropy pop/tperpoverpar ratio of perpendicular temperature to parallel temperature
pop/vg_t_anisotropy_nonthermal pop/tperpoverparbackstream ratio of perpendicular temperature to parallel temperature for non-thermal particles
pop/vg_t_anisotropy_thermal pop/tperpoverparnonbackstream ratio of perpendicular temperature to parallel temperature for thermal particles
--------------------- -------------------- --------------------
pop/vg_agyrotropy pop/agyrotropy agyrotropy (according to Swisdak 2016)
pop/vg_agyrotropy_nonthermal pop/agyrotropybackstream agyrotropy for non-thermal particles
pop/vg_agyrotropy_thermal pop/agyrotropynonbackstream agyrotropy for thermal particles
--------------------- -------------------- --------------------
pop/vg_beta pop/beta plasma beta
pop/vg_beta_parallel pop/betaparallel plasma beta, component parallel to B
pop/vg_beta_perpendicular pop/betaperpendicular plasma beta, component perpendicular to B
pop/vg_beta_anisotropy pop/betaperpoverpar ratio of perpendicular beta to parallel beta
pop/vg_beta_anisotropy_nonthermal pop/betaperpoverparbackstream ratio of perpendicular beta to parallel beta for non-thermal particles
pop/vg_beta_anisotropy_thermal pop/betaperpoverparnonbackstream ratio of perpendicular beta to parallel beta for thermal particles
--------------------- -------------------- --------------------