Multi-space craft radio observation tracks magnetic fields in the heliosphere
An overview of the Type III bursts observed by the four spacecraft. (a) Dynamic spectrum. (b) Time profile at four frequencies of intensity scaled to 1 Au. (c) Intensity peaks and directional fitting from panel (b). (d) Maximum length of fitted strength. The symbol indicates the location of the Heliosphere spacecraft. Credits: Clarkson, DL, and others 2025
Solar flares accelerate energy electrons that escape into interplanetary space, directed by Parker’s helical magnetic field, and are responsible for generating interplanetary III solar radio bursts. With multiple spacecrafts orbiting around the sun, we are in a unique position to observe the propagation of radio emissions through the Heliosphere from multiple perspectives.
Recent research by Daniel L. Clarkson et al. show that magnetic fields not only direct emitted electrons, but also direct radio waves through anisotropic scattering from density irregularities in magnetized plasma in interplanetary space.
To study this effect over long distances of the Heliosphere, researchers used observations of 20-inch bursts of approximately 0.9-0.2 MHz from Parker solar probes, solar orbiters, stereo A, wind spacecraft distributed around the sun.
To reproduce the observations, simulations are carried out to follow radio waves. This study has been published in the journal Science Reports.
Simulations show that radio waves are directed by heliosphere magnetic fields via anisotropic scattering.
Pole plots of time-averaged simulated photon propagation in the heliosphere of (a) basic emitters (blue stars) and (b) harmonic emitters (green stars). The colored histogram shows photon positions with the average wave vector at a particular location indicated by the black arrows. The inset shows approximate directionality at significantly lower scattering velocity. Credits: Clarkson, DL, and others 2025
Assuming that the magnetic field leads only to emit electrons, the paper concludes that the directional pattern in multi-space craft observations cannot be explained without invoking the steeper curvature of Parker’s spirals while the radiation is weakly scattered.
Thus, the emitted radio waves are guided along the interplanetary field due to anisotropic scattering, affecting the radiation received by observers spatially separated around the Sun.
The eastward deviation of the Type III radio burst intensity (increasing distance) with Type III radio burst intensity allows the magnetic field to be traced to a distance greater than the distance of the emitter path, providing a powerful diagnostic tool for space weather research and a potentially wide-ranging diagnosis of the magnetic field structures of different celestial material environments where the radio source is embedded.
Details: Daniel L. Clarkson et al, Tracking Heliosphere Magnetic Fields via Anisotropic Radiowave Scattering, Scientific Report (2025). doi:10.1038/s41598-025-95270-w
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Quote: Multi-space craft radio observation tracks the heliosphere magnetic field obtained from April 26, 2025 from https://news/2025-04-multi–multi-pacecraft-radio-heliosphere-magnetic.html (April 25, 2025)
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