Counterintuitive Particle Confinement in a Helical Force-Free Plasma
The force-free magnetic field solution formed in a high-aspect ratio cylinder is a non-axisymmetric (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>m</mi><mo>=</mo><mn>1&...
Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-05-01
|
| Series: | Plasma |
| Subjects: | |
| Online Access: | https://www.mdpi.com/2571-6182/8/2/20 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1849425520650878976 |
|---|---|
| author | Adam D. Light Hariharan Srinivasulu Christopher J. Hansen Michael R. Brown |
| author_facet | Adam D. Light Hariharan Srinivasulu Christopher J. Hansen Michael R. Brown |
| author_sort | Adam D. Light |
| collection | DOAJ |
| description | The force-free magnetic field solution formed in a high-aspect ratio cylinder is a non-axisymmetric (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>m</mi><mo>=</mo><mn>1</mn></mrow></semantics></math></inline-formula>), closed magnetic structure that can be produced in laboratory experiments. Force-free equilibria can have strong field gradients that break the usual adiabatic invariants associated with particle motion, and gyroradii at measured conditions can be large relative to the gradient scale lengths of the magnetic field. Individual particle motion is largely unexplored in force-free systems without axisymmetry, and it is unclear how the large gradients influence confinement. To understand more about how particles remain confined in these configurations, we simulate a thermal distribution of protons moving in a high-aspect-ratio force-free magnetic field using a Boris stepper. The particle loss is logarithmic in time, which suggests trapping and/or periodic orbits. Many particles do remain confined in particular regions of the field, analogous to trapped particles in other magnetic configurations. Some closed flux surfaces can be identified, but particle orbits are not necessarily described by these surfaces. We show examples of orbits that remain on well-defined surfaces and discuss the statistical properties of confined and escaping particles. |
| format | Article |
| id | doaj-art-2ea4aecec6f344dc92a54cdfdd1d2195 |
| institution | Kabale University |
| issn | 2571-6182 |
| language | English |
| publishDate | 2025-05-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Plasma |
| spelling | doaj-art-2ea4aecec6f344dc92a54cdfdd1d21952025-08-20T03:29:44ZengMDPI AGPlasma2571-61822025-05-01822010.3390/plasma8020020Counterintuitive Particle Confinement in a Helical Force-Free PlasmaAdam D. Light0Hariharan Srinivasulu1Christopher J. Hansen2Michael R. Brown3Physics, Colorado College, 14 E Cache la Poudre Street, Colorado Springs, CO 80903, USAPhysics and Astronomy, Swarthmore College, 500 College Ave, Swarthmore, PA 19081, USAApplied Physics & Applied Mathematics, Columbia University, 500 W 120th St, New York, NY 10027, USAPhysics and Astronomy, Swarthmore College, 500 College Ave, Swarthmore, PA 19081, USAThe force-free magnetic field solution formed in a high-aspect ratio cylinder is a non-axisymmetric (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>m</mi><mo>=</mo><mn>1</mn></mrow></semantics></math></inline-formula>), closed magnetic structure that can be produced in laboratory experiments. Force-free equilibria can have strong field gradients that break the usual adiabatic invariants associated with particle motion, and gyroradii at measured conditions can be large relative to the gradient scale lengths of the magnetic field. Individual particle motion is largely unexplored in force-free systems without axisymmetry, and it is unclear how the large gradients influence confinement. To understand more about how particles remain confined in these configurations, we simulate a thermal distribution of protons moving in a high-aspect-ratio force-free magnetic field using a Boris stepper. The particle loss is logarithmic in time, which suggests trapping and/or periodic orbits. Many particles do remain confined in particular regions of the field, analogous to trapped particles in other magnetic configurations. Some closed flux surfaces can be identified, but particle orbits are not necessarily described by these surfaces. We show examples of orbits that remain on well-defined surfaces and discuss the statistical properties of confined and escaping particles.https://www.mdpi.com/2571-6182/8/2/20force-freeparticle orbitsmagnetized plasma |
| spellingShingle | Adam D. Light Hariharan Srinivasulu Christopher J. Hansen Michael R. Brown Counterintuitive Particle Confinement in a Helical Force-Free Plasma Plasma force-free particle orbits magnetized plasma |
| title | Counterintuitive Particle Confinement in a Helical Force-Free Plasma |
| title_full | Counterintuitive Particle Confinement in a Helical Force-Free Plasma |
| title_fullStr | Counterintuitive Particle Confinement in a Helical Force-Free Plasma |
| title_full_unstemmed | Counterintuitive Particle Confinement in a Helical Force-Free Plasma |
| title_short | Counterintuitive Particle Confinement in a Helical Force-Free Plasma |
| title_sort | counterintuitive particle confinement in a helical force free plasma |
| topic | force-free particle orbits magnetized plasma |
| url | https://www.mdpi.com/2571-6182/8/2/20 |
| work_keys_str_mv | AT adamdlight counterintuitiveparticleconfinementinahelicalforcefreeplasma AT hariharansrinivasulu counterintuitiveparticleconfinementinahelicalforcefreeplasma AT christopherjhansen counterintuitiveparticleconfinementinahelicalforcefreeplasma AT michaelrbrown counterintuitiveparticleconfinementinahelicalforcefreeplasma |