it would still be affecting the outflows. In that regard, the measurement of the magnetic field at the stellar surface, which is still missing, combined with a full MHD treatment are required to better understand and constrain the events occurring in OH 231.8+4.2.\
bibliography:
- 'OH231.bib'
date: 'Accepted 2020 May 18. Received 2020 May 16; in original form 2020 April 13 '
title: 'ALMA reveals the coherence of the magnetic field geometry in OH 231.8+4.2'
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magnetic fields — polarization — stars: AGB and post-AGB — ISM: jets and outflows ISM: individual: OH231.8+4.2

Introduction
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The detection of magnetic fields in evolved low and intermediate–mass stars ($\sim$0.8–8 M), such as AGB and post-AGB stars (pAGBs), pre-planetary (pPNe) and planetary nebulae (PNe), has generated great interest over the last decade. The main reason lies in our desire to understand the role magnetic fields could play in the dramatic departures from spherical symmetry occurring during the transition from the AGB to the PNe evolutionary phases [@Sahai2007; @Sahai2011].\
Observations, detections and measurements of the field topology and strength have been performed using different methods: (spectro)polarimetry of various maser species (e.g. @Vlemmings2008 [@Ferreira2013; @GOMEZ2016; @Vlemmings2017]), measurement of circular polarization (Stokes [*V*]{}) in stellar 