Bug fixes:

• Re-added ToroidalHaloField and LogarithmicSpiralField models. Note, that the class name was also corrected in spelling: TorroidalHaloField --> ToroidalHaloField
• Synchronized signature of ParticleSplitting constructor

New features:

• New candidate property tagOrigin to trace back which source or which interaction created the candidate
• New interface for massdistributions given on a Grid1f
• Grids can be restricted to the volume without repetition (clipVolume parameter)
• SourceFeature to sample the source position from a given massdistribution
• EBL model from Saldana-Lopez et al. 2021
• New module CandidateSplitting for better statistics at high energies for e.g. diffusive shock acceleration
• New advection fields for modeling diffusive shock acceleration at 1D planar, oblique and spherical shocks

Interface changes:

• Weight column in hdf-Output is now called "W", which is the same as for TextOutput.

Features that are deprecated and will be removed after this release

• ObserverPoint will be renamed into Observer1D.
• AMRMagneticField - underlying library (saga) is no longer supported.

Removed features

• External extensions DINT and Eleca, which can be replaced with the
  EM*-modules combined with the thinning option for reasonable computation
  times.

New plugins and resources linked on the webpages:

• FieldlineIntegrator
• grplinst
• monopole
• ROOTOutputPlugin

CRPropa 3.2

Bug fixes:

• Fix of reflective boundary condition for scalar- and vectorgrids
  that showed asymmetry and discontinuities (See issue [#361]).
• Fix in EMTripletPairProduction
• Fix of the data files of the Hackstein EGMF models as well as the
  corresponding example notebook.
• Fix of axis normalization of getRotated in Vector3.h.
• Fix of secondary spectra in electromagnetic interactions
  (EM*-modules), issue [#334] and pull request [#15] in crpropa-data.
• Fix weight inheritance for secondary particles; they are created with
  their parents weights as initial weights now.

New features:

• Add modules for first and second order Fermi acceleration
• Make custom photon fields available in the PhotoPionProduction module.
• Add tricubic- and nearest neighbour interpolation routines for scalar-
  and vectorgrids.
• Add the new PolarizedSingleModeMagneticField class for polarized/
  helical single mode magnetic field models.
• Add a source feature for targeted emission, following the
  von-Mises-Fisher distribution
• Updates in SNR and pulsar source distributions

Interface changes:

• Plane wave and grid turbulence models use same parameter convention now

Features that are deprecated and will be removed after this release

• External extensions DINT and Eleca, which can be replaced with the
  EM*-modules combined with the thinning option for reasonable computation
  times.

New plugins and resources linked on the webpages:

• Updated version of the CLUES EGMF models

Bug fixes:

• Re-add URB that was temporarily not available in the (unreleased) master branch. [#315]
• Turbulent fields generated on a grid were limited up to 2048 grid-size due to an integer overflow (i.e. 2048^3 index > signed int); solved by replacing int with size_t

New features:

• New model for the radio background added: Nitu et al. 2021 measurements (see pull request #315)
• New model for the radio background added: Fixsen et al. 2011 (ARCADE-2) measurements.
• Weighted sampling thinning of electromagnetic processes (EMPairProduction, EMInverseComptonScattering, EMDoublePairProduction, EMTripletPairProduction) (see pull request #281 )
• Planck JF12b variant of the JF12Field. See arXiv:1601.00546. Thanks to Mikhail Zotov for contributing (see pull request #273 )
• ParticleCollector can provide Candidates directly to ModuleList::run
• Basic file versioning of the data archive in CMakeLists.txt
• Python docstrings are generated automatically from doxygen documentation (see pull request #301)
• New method to discard particles with minimum energy below a given threshold, depending on the type of particle (see pull request #289)
• Photon field classes replaced the photon field enumerator, consequently, the new photon fields implementation follows the same logic as of the other modules making it is easier to introduce custom ones (see pull request #286 )
• New class-based interface for turbulent fields introduced
• New turbulence modules implemented: (see pull request #287)
  • GridTurbulence (with the bendover scale) which should in general be used instead of initTurbulence (before, it was implemented as initTurbulenceWithBendover);
  • SimpleGridTurbulence which provides the exact field as initTurbulence;
  • HelicalGridTurbulence which provides the exact field as initHelicalTurbulence
  • PlaneWaveTurbulence a new algorithm based on Giacalone & Jokipii, 1999 and Tautz & Dosch, 2013.
• New CMake option: BUILD_DOC for building Doxygen & Sphinx docs

Interface change:

• ParticleCollector::getAll() -> ParticleCollector::getContainer()
• Photon fields are no longer items of the PhotonField enumerator but independent classes that share the same interface, so instead of CMB one should use CMB(), instead of IRB_Kneiske04 - IRB_Kneiske04(), etc.
• initTurbulenceWithBendover() removed (as it was just briefly present in the code) and replaced with GridTurbulence

Features that are deprecated and will be removed after this release:

• Turbulence-related functions: initTurbulence, turbulentCorrelationLength, initHelicalTurbulence

Bug fixes:

• Fix of (#254): Redshift evolution in PhotoPionProduction
  The reshift evolution was always handled with simple scaling and never with
  the more accurate 2 dimensional interpolation.

New features:

• New source feature SourceLambertDistributionOnSphere
  Simplifies simulations of scenarios with an initially isotropic and homogeneous
  distribution of cosmic rays on a sphere, e.g. for investigation of propagation
  of extagalactic cosmic rays in the Milky Way (see issue #246 and pull
  request #247)
• For PhotoPionProduction now a two dimensional interpolation of the redshift
  evolution is available (see pull request #255)
• A new break condition MinimumChargeNumber is added (see pull request #256)
• Vector3 now has index based access to its components. This improves
  interoperability with third party libraries, in particular with numpy arrays.
  (see pull request #262)
• Random seeds can be accessed from python (see pull request #263)
• New galactic magnetic field model by Terral & Ferriere (2017) (see pull request #258)
• Reimplementation of SOPHIA's photon field sampling used in
  PhotoPionProduction in c++, leading to a factor 2-3 speed up of the
  module (see pull request #260).
• Introducing a method, sophiaEvent(onProton, Eprimary, Ephoton), to
  directly call SOPHIA's event generator from python (see pull request #260).

Bug fixes:

• Fixed issue with secondaries in the PhotoPionProduction potentially relevant for primary energies above approx. 10**21 eV (See issue [#225]).
• Fix of azimuthal component of ArchimedeanSpiral Field (See commit 1f79e2c). Thanks to Leander Schlegel for reporting and providing a patch.

New features:

• The PropagatorBP implements the Boris-Push algorithm as as alternative to the Cash-Karp integrator PropagatorCK. Thanks to Patrick Reichherzer for this contribution.
• A basic geometry system was added to e.g. restrict modules to a spatial region.
• Candidates now have weights.
• User can define custom candidate properties identified with a string (slow but sometimes handy).
• Random seeds can be stored in output files. Please note that perfect reproducibility of simulations is still not guaranteed when using multi cores.
• The 'ParticleCollector' allows in-memory storage of Candidates for collective-processing during a simulation.
• The SDE solver supports advection and adiabatic cooling.
• A selection of models for mass distributions in our Galaxy as first step of the development of a hadron-hadron interaction module was added. Thanks to Julien Dörner for implementing these models.
• Source distributions following the Galactic pulsar distribution and the Galactic SNR distributions are available.
• Turbulent magnetic fields can now be optionally helical (initHelicalTurbulence) or obey the homogeneous turbulence theory requirement (initTurbulenceWithBendover).
• Modified JF12 Galactic magnetic field model with a truly solenoidal disk spiral field and a smooth X field with parabolic field lines according to Kleimann et al. (arXiv:1809.07528). Thanks to Timo Schorlepp for sharing this code.

Features that are deprecated and will be removed after this release:

• PhotonOutput1D is obsolete as the functionality is provided by the regular output modules (See #211).
• Future releases will use C++11 features. Outdated compilers will not be supported anymore.

New plugins and resources linked on the webpages:

• ROOTOutput. This code has been moved from CRPropa to a plugin and is no longer maintained by us. If you want to maintain this code, please contact us.
• Data for the constrained 'Hackstein' models of the local Universe using initial conditions from the CLUES project. Thanks to Stefan Hackstein for sharing.

• Integration of EM interactions for with cosmic background radiation (EBL, CMB, radio) for cosmic ray photons and electrons with E > 10 GeV:
  • Photons: pair production, double pair production
  • Electrons: triplet pair production, inverse Compton scattering, synchrotron radiation
• Extended photon production channels
  • Photodisintegration, elastic scattering, nuclear decay, synchrotron radiation
• Diffusion module for efficient propagation in the diffusive regime
  • Stochastic differential equations are used to solve the Fokker-Planck transport equation
  • Anisotropic diffusion tensor with respect to the magnetic field line are possible

The corresponding JCAP reference is JCAP05(2016)038 (http:https://dx.doi.org/10.1088/1475-7516/2016/05/038).
The preprint on arXiv can be found at http:https://arxiv.org/abs/1603.07142