Dartmouth Events

Physics & Astronomy Colloquium - Professor Stuart D. Bale, UC Berkeley

Title: "Interchange magnetic reconnection is the source of the fast solar wind"

Friday, May 26, 2023
3:30pm – 4:30pm
Wilder 104 and Zoom
Intended Audience(s): Public
Categories: Arts and Sciences, Lectures & Seminars

Abstract: The fast solar wind that fills the heliosphere originates from deepwithin regions of open magnetic field on the Sun called ‘coronal holes’.The energy source responsible for accelerating the plasma is widelydebated; however, there is evidence that it is ultimately magnetic innature, with candidate mechanisms including wave heating andinterchange reconnection. The coronal magnetic field near the solarsurface is structured on scales associated with ‘supergranulation’convection cells, whereby descending flows create intense fields. Theenergy density in these ‘network’ magnetic field bundles is a candidateenergy source for the wind. Here we report measurements of fast solarwind streams from the NASA Parker Solar Probe (PSP) spacecraft that providestrong evidence for the interchange reconnection mechanism. We show thatthe supergranulation structure at the coronal base remains imprinted inthe near-Sun solar wind, resulting in asymmetric patches of magnetic‘switchbacks’ and bursty wind streams with power-law-like energeticion spectra to beyond 100 keV. Computer simulations of interchangereconnection support key features of the observations, including the ionspectra. Important characteristics of interchange reconnection in thelow corona are inferred from the data, including that the reconnectionis collisionless and that the energy release rate is sufficient to powerthe fast wind. In this scenario, magnetic reconnection is continuous andthe wind is driven by both the resulting plasma pressure and the radialAlfvénic flow bursts

Hosted by Professor James LaBelle

Please click the link below to join the webinar:
Email physics.department@dartmouth.edu for passcode


For more information, contact:
Tressena Manning

Events are free and open to the public unless otherwise noted.