Preferential Heating of Protons over Electrons from Coherent Structures during the First Perihelion of the Parker Solar Probe

Abstract

The solar wind undergoes significant heating as it propagates away from the Sun; the exact mechanisms responsible for this heating remain unclear. Using data from the first perihelion of the Parker Solar Probe mission, we examine the properties of proton and electron heating occurring within magnetic coherent structures identified by means of the Partial Variance of Increments (PVI) method. Statistically, regions of space with strong gradients in the magnetic field, PVI ≥ 1, are associated with strongly enhanced proton but only slightly elevated electron temperatures. Our analysis indicates a heating mechanism in the nascent solar wind environment facilitated by a nonlinear turbulent cascade that preferentially heats protons over electrons.

Proton and Electron Temperatures in the Solar Wind and Their Correlations with the Solar Wind Speed

“…In addition to the wave-particle interaction, other effects, such as intermittency (e.g., Osman et al 2012) and stochastic heating (e.g., Chandran et al 2010), may also contribute to the differential heating process. Sioulas et al (2022a), using PSP measurements, have shown that protons can gain more energy from intermittent structures than electrons. The stochastic heating is positively correlated with the turbulence strength (Vech et al 2017) and is shown to be significant throughout the inner heliosphere (Martinović et al 2019(Martinović et al , 2020, contributing to the perpendicular temperature of ions.…”

Kinetic‐Scale Current Sheets in the Solar Wind at 5 AU

“…The high‐resolution magnetic field measurements aboard modern spacecraft missions demonstrated that CSs are much more abundant and statistically thinner than reported early on (Artemyev, Angelopoulos, & Vasko, 2019; Lotekar et al., 2022; Perri et al., 2012; Podesta, 2017; Vasko et al., 2021, 2022; Vasquez et al., 2007; Wang et al., 2024). The CSs were also shown to substantially contribute into magnetic field spectra of solar wind turbulence (Borovsky & Burkholder, 2020; Borovsky & Podesta, 2015) and potentially cause plasma heating (Osman et al., 2012; Qudsi et al., 2020; Sioulas et al., 2022; Wu et al., 2013) and particle acceleration (Zhao et al., 2018, 2019). There are several comprehensive analyses of solar wind CSs at 0.2 and 1 AU, but only few analyses of similar structures at the distances well beyond 1 AU.…”

Exploring Turbulence from the Sun to the Local Interstellar Medium

“…Many aspects of how the cascade operates in the kinetic regime are unknown, especially in the outer heliosphere. Debated topics include the preferential ion heating vs the electron heating and temperature anisotropy [18,12,104,117,125]; specific phenomenology dominating in the kinetic regimes; role of turbulence in driving ion beams [122,121] and kinetic microinstabilities [16]; role of ICWs [8], and PUI-driven instabilities [52,112].…”