# On the Effects of Pickup Ion-driven Waves on the Diffusion Tensor of Low-energy Electrons in the Heliosphere

## Abstract

The effects of Alfvén cyclotron waves generated due to the formation in the outer heliosphere of pickup ions on the transport coefficients of low-energy electrons is investigated here. To this end, parallel mean free path (MFP) expressions are derived from quasilinear theory, employing the damping model of dynamical turbulence. These are then used as inputs for existing expressions for the perpendicular MFP and turbulence-reduced drift coefficient. Using outputs generated by a two-component turbulence transport model, the resulting diffusion coefficients are compared with those derived using a more typically assumed turbulence spectral form, which neglects the effects of pickup ion-generated waves. It is found that the inclusion of pickup ion effects greatly leads to considerable reductions in the parallel and perpendicular MFPs of 1–10 MeV electrons beyond ∼10 au, which are argued to have significant consequences for studies of the transport of these particles.

- Authors:

- Center for Space Research, North-West University, Potchefstroom, 2522 (South Africa)

- Publication Date:

- OSTI Identifier:
- 22654354

- Resource Type:
- Journal Article

- Journal Name:
- Astrophysical Journal Letters

- Additional Journal Information:
- Journal Volume: 849; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 2041-8205

- Country of Publication:
- United States

- Language:
- English

- Subject:
- 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALFVEN WAVES; COMPARATIVE EVALUATIONS; COSMIC RADIATION; CYCLOTRON RADIATION; DIFFUSION; ELECTRONS; HELIOSPHERE; INCLUSIONS; IONS; MEAN FREE PATH; MEV RANGE; QUASILINEAR PROBLEMS; SUN; TRANSPORT THEORY; TURBULENCE

### Citation Formats

```
Engelbrecht, N. Eugene, E-mail: n.eugene.engelbrecht@gmail.com.
```*On the Effects of Pickup Ion-driven Waves on the Diffusion Tensor of Low-energy Electrons in the Heliosphere*. United States: N. p., 2017.
Web. doi:10.3847/2041-8213/AA9372.

```
Engelbrecht, N. Eugene, E-mail: n.eugene.engelbrecht@gmail.com.
```*On the Effects of Pickup Ion-driven Waves on the Diffusion Tensor of Low-energy Electrons in the Heliosphere*. United States. doi:10.3847/2041-8213/AA9372.

```
Engelbrecht, N. Eugene, E-mail: n.eugene.engelbrecht@gmail.com. Wed .
"On the Effects of Pickup Ion-driven Waves on the Diffusion Tensor of Low-energy Electrons in the Heliosphere". United States. doi:10.3847/2041-8213/AA9372.
```

```
@article{osti_22654354,
```

title = {On the Effects of Pickup Ion-driven Waves on the Diffusion Tensor of Low-energy Electrons in the Heliosphere},

author = {Engelbrecht, N. Eugene, E-mail: n.eugene.engelbrecht@gmail.com},

abstractNote = {The effects of Alfvén cyclotron waves generated due to the formation in the outer heliosphere of pickup ions on the transport coefficients of low-energy electrons is investigated here. To this end, parallel mean free path (MFP) expressions are derived from quasilinear theory, employing the damping model of dynamical turbulence. These are then used as inputs for existing expressions for the perpendicular MFP and turbulence-reduced drift coefficient. Using outputs generated by a two-component turbulence transport model, the resulting diffusion coefficients are compared with those derived using a more typically assumed turbulence spectral form, which neglects the effects of pickup ion-generated waves. It is found that the inclusion of pickup ion effects greatly leads to considerable reductions in the parallel and perpendicular MFPs of 1–10 MeV electrons beyond ∼10 au, which are argued to have significant consequences for studies of the transport of these particles.},

doi = {10.3847/2041-8213/AA9372},

journal = {Astrophysical Journal Letters},

issn = {2041-8205},

number = 1,

volume = 849,

place = {United States},

year = {2017},

month = {11}

}