Abstract
The high temperatures and strong magnetic fields of the solar corona form streams of solar wind that expand through the Solar System into interstellar space. At 09:33 UT on 28 April 2021 Parker Solar Probe entered the magnetized atmosphere of the Sun 13million km above the photosphere, crossing below the Alfvén critical surface for five hours into plasma in casual contact with the Sun with an Alfvén Mach number of 0.79 and magnetic pressure dominating both ion and electron pressure. The spectrum of turbulence below the Alfvén critical surface is reported. Magnetic mapping suggests the region was a steady flow emerging on rapidly expanding coronal magnetic field lines lying above a pseudostreamer. The sub-Alfvénic nature of the flow may be due to suppressed magnetic reconnection at the base of the pseudostreamer, as evidenced by unusually low densities in this region and the magnetic mapping.
Highlights
BWX Technologies, Inc., Washington, DC 20001, USA and Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
The high temperatures and strong magnetic fields of the solar corona form streams of solar wind that expand through the Solar System into interstellar space
At 09:33 UT on 28 April 2021 Parker Solar Probe entered the magnetized atmosphere of the Sun 13 million km above the photosphere, crossing below the Alfven critical surface for five hours into plasma in casual contact with the Sun with an Alfven Mach number of 0.79 and magnetic pressure dominating both ion and electron pressure
Summary
Climate and Space Sciences and Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA. Space Sciences Laboratory at University of California, Berkeley, California, USA. Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Surrey RH5 6NT, United Kingdom. Physics Department, University of California, Berkeley, California 94720-7300, USA and Space Sciences Laboratory at University of California, Berkeley, California 94720-7300, USA. LESIA, Observatoire de Paris, Universite PSL, CNRS, Sorbonne Universite, Universite de Paris, 5 place Jules Janssen, 92195 Meudon, France. Laboratory for Atmospheric and Space Physics, University of Colorado Boulder, Boulder, Colorado 80303, USA. Heliospheric Physics Laboratory, NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771, USA
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