Abstract

Exactly three years ago, in November 2018, the NASA Parker Solar Probe (PSP) mission went through its first perihelion at 35 solar radii (Rs), well inside the orbit of Mercury, corresponding then to our closest approach to Sun ever achieved before. Since then, PSP has orbited 9 times around our star, heading now for a 10th perihelion later this month, and its closest approaches have gradually reached 15Rs, meaning less than 1/10th of the Sun-Earth distance, measuring then properties of the solar wind plasma very close to its solar sources for the first time. One of the most unexpected and intriguing finding of the first phase of the mission is the in-situ observation of ubiquitous short-living magnetic field polarity reversals associated with distinct jet-like speed enhancements in the solar wind flow. These local folds in the interplanetary magnetic field, previously know as “switchbacks”, have been already observed before in the solar wind, especially in plasma coming from the polar regions of the Sun, however their persistence, cadence and morphology in the near-Sun is both new and unexpected. Moreover, they are embedded in wind coming from more equatorial Sun’s regions, like the streamer and low-latitude small coronal holes. In this talk, I will review some of the main PSP first results, discussing in particular the detection of switchbacks and presenting their main properties. Different models for the generation of these plasma features recently proposed in the solar wind community will be discussed, ranging from interchange reconnection in the Solar atmosphere to generation by spherical expansion in the interplanetary space. I will also show how the presence of these magnetic features, as well as their large scale modulation that is particularly apparent in the flow closer to the Sun, can offer a way to probe their source regions directly, revealing signatures of super-granulation and perhaps also granulation.