A laboratory model for the Parker spiral and magnetized stellar winds

Abstract

Many rotating stars have magnetic fields that interact with the winds they produce. The Sun is no exception. The interaction between the Sun’s magnetic field and the solar wind gives rise to the heliospheric magnetic field—a spiralling magnetic structure, known as the Parker spiral, which pervades the Solar System. This magnetic field is critical for governing plasma processes that source the solar wind. Here, we report the creation of a laboratory model of the Parker spiral system based on a rapidly rotating plasma magnetosphere and the measurement of its global structure and dynamic behaviour. This laboratory system exhibits regions where the plasma flows evolve in a similar manner to many magnetized stellar winds. We observe the advection of the magnetic field into an Archimedean spiral and the ejection of quasi-periodic plasma blobs into the stellar outflow, which mimics the observed plasmoids that fuel the slow solar wind. This process involves magnetic reconnection and can be modelled numerically by the inclusion of two-fluid effects in the simulation. The Parker spiral system mimicked in the laboratory can be used for studying solar wind dynamics in a complementary fashion to conventional space missions such as NASA’s Parker Solar Probe mission.

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Fig. 1: A laboratory recipe for creating a Parker spiral and stellar wind.
Fig. 2: Magnetospheric evolution exhibits two distinct phases.
Fig. 3: Measured and simulated 3D magnetic fields result in a Parker spiral.
Fig. 4: Measured rotation approaches the Alfvén speed along the current sheet.
Fig. 5: Plasmoid ejection occurs in both the experiment and Hall-MHD simulation.

Data availability

Raw data were generated at the Big Red Ball facility at the Wisconsin Plasma Physics Laboratory. Derived data supporting the findings of this study are available from the corresponding author upon reasonable request.

Code availability

Information about the NIMROD code, including publications and licensing policies, is available at https://nimrodteam.org. Code produced for analysing data at the Big Red Ball Facility is available from the corresponding author upon reasonable request.

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Acknowledgements

The present work was supported by the NASA Earth and Space Sciences–Heliophysics Division Fellowship. The facility was constructed with support from the National Science Foundation and is now operated as a Department of Energy National User Facility.

Author information

E.E.P. designed and built the linear Hall probe array, mach and triple probes, executed the experiments and data acquisition, performed all the data analysis and NIMROD simulations and wrote the majority of the text. D.A.E. constructed the magnet, electrode system and capacitor bank trigger circuit and was a partner in running the experiments. D.A.E., M.C., R.W. and E.E.P. constructed the capacitor banks. J.W. designed and constructed motorized probe stages and maintained the vacuum system. C.R.S., K.J.B. and M.B. were instrumental in making modifications to the NIMROD code to be applicable to this experiment and aided in interpreting the simulation results. K.F. and K.J.M. contributed to the compiling of NIMROD. J.M., K.F., J.O. and D.A.E. contributed to construction of the control software and interpreting the data. C.B.F. and J.E. contributed to the interpretation of data and simulations as well as to the writing and editing of the manuscript. C.B.F. is the principal investigator and director of WiPPL, and provided the overall leadership for this project.

Correspondence to Ethan E. Peterson.

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The authors declare no competing interests.

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Peer review information: Nature Physics thanks R. Paul Drake, Nicola Fox and Kristopher Klein for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Information on the Supplementary Videos.

Supplementary Video 1

Visible light emission captures both broadband and coherent fluctuations.

Supplementary Video 2

Experimental measurements reveal reconnection and plasmoid ejection.

Supplementary Video 3

Hall-MHD simulation reveals plasmoids with similar frequency to the experiment.

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