Recent studies of particle acceleration in the heliosphere have revealed a new mechanism that can locally energizeparticles up to several MeV nucleon–1. Stream–stream interactions, as well as the heliospheric current sheet(CS)—stream interactions, lead to formation of large magnetic cavities, bordered by strong CSs, which in turn producesecondary CSs and dynamical small-scale magnetic islands(SMIs)of∼0.01 au or less owing to magneticreconnection. It has been shown that particle acceleration or reacceleration occurs via stochastic magneticreconnection in dynamical SMIs confined inside magnetic cavities observed at 1 au. The study links the occurrenceof CSs and SMIs with characteristics of intermittent turbulence and observations of energetic particles of keV–MeV nucleon–1energies at∼5.3 au. We analyze selected samples of different plasmas observed byUlyssesduringa widely discussed event, which was characterized by a series of high-speed streams of various origins thatinteracted beyond Earth’s orbit in 2005 January. The interactions formed complex conglomerates of mergedinterplanetary coronal mass ejections, stream/corotating interaction regions, and magnetic cavities. We studyproperties of turbulence and associated structures of various scales. We confirm the importance of intermittentturbulence and magnetic reconnection in modulating solar energetic particleflux and even local particleacceleration. Coherent structures, including CSs and SMIs, play a significant role in the development of secondarystochastic particle acceleration, which changes the observed energetic particleflux time–intensity profiles andincreases thefinal energy level to which energetic particles can be accelerated in the solar wind
Current Sheets, Magnetic Islands, and Associated Particle Acceleration in the Solar Wind as Observed by Ulysses near the Ecliptic Plane
Greco A.;Pezzi O.;Servidio S.;
2019-01-01
Abstract
Recent studies of particle acceleration in the heliosphere have revealed a new mechanism that can locally energizeparticles up to several MeV nucleon–1. Stream–stream interactions, as well as the heliospheric current sheet(CS)—stream interactions, lead to formation of large magnetic cavities, bordered by strong CSs, which in turn producesecondary CSs and dynamical small-scale magnetic islands(SMIs)of∼0.01 au or less owing to magneticreconnection. It has been shown that particle acceleration or reacceleration occurs via stochastic magneticreconnection in dynamical SMIs confined inside magnetic cavities observed at 1 au. The study links the occurrenceof CSs and SMIs with characteristics of intermittent turbulence and observations of energetic particles of keV–MeV nucleon–1energies at∼5.3 au. We analyze selected samples of different plasmas observed byUlyssesduringa widely discussed event, which was characterized by a series of high-speed streams of various origins thatinteracted beyond Earth’s orbit in 2005 January. The interactions formed complex conglomerates of mergedinterplanetary coronal mass ejections, stream/corotating interaction regions, and magnetic cavities. We studyproperties of turbulence and associated structures of various scales. We confirm the importance of intermittentturbulence and magnetic reconnection in modulating solar energetic particleflux and even local particleacceleration. Coherent structures, including CSs and SMIs, play a significant role in the development of secondarystochastic particle acceleration, which changes the observed energetic particleflux time–intensity profiles andincreases thefinal energy level to which energetic particles can be accelerated in the solar windI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
