Speaker
Description
AU-scale magnetic structures in the interstellar medium (ISM) — particularly current sheets formed at magnetic-field reversals — are predicted to strongly influence cosmic-ray transport, yet direct observations at these scales have remained inaccessible. Traditional Faraday rotation measure (RM) techniques lack the sub-parsec resolution required and are contaminated by ionospheric systematics.
We present a new method that exploits interstellar scintillation to resolve AU-scale magnetic geometry. By applying phase retrieval to isolate birefringence-induced polarization between proximal scattered ray paths, we perform differential RM measurements that isolate the magnetic signal of AU-scale foreground structures — circumventing ionospheric contamination by over two orders of magnitude in RM precision.
Applying this method to archival VLBI observations of PSR B0834+06, we identify two ray paths grazing opposite sides of a foreground current sheet with AU-scale transverse thickness. We measure a branch-to-branch RM offset of $(−9.4±3.3)×10^{−3} \text{ rad m}^{-2}$ (2.8$\sigma$), implying a magnetic-field reversal of $|\Delta\langle B_\parallel\rangle|\simeq 4.4±2.1 \,\mu \text G$. This result provides the first suggestive observational evidence for AU-scale magnetic-field reversal in the diffuse ISM, with direct implications for cosmic-ray transport and pulsar timing array experiments.
| Participate the oral/poster presentation award competition | No |
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