Ion leakage at dayside magnetopause in case of high and low magnetic shears

Abstract

The nature of energetic ions in the magnetosheath of the Earth is studied using the data of the Time History of Events and Macroscale Interactions during Substorms mission. Three intervals of the multiple crossings of the magnetopause during northward orientation of the interplanetary magnetic field and quiet geomagnetic conditions were selected to illustrate the behavior of ion distribution functions near the subsolar region in case of high and low magnetic shears. For all analyzed events, the velocity and thickness of the magnetopause was estimated using the simultaneous measurements in two satellites. The ion spectra in the magnetosphere and magnetosheath were fitted by kappa and bi‐kappa distributions, respectively. It was found that during high shear events the energetic part of the ion spectra is practically identical inside and outside the magnetopause. On the other side, for low shear events the energetic fluxes of ions in the magnetosheath are lower. We argue that in case of high magnetic shear, the magnetopause becomes transparent when the ion Larmor radii is comparable or larger than the thickness of the magnetopause. It may explain coincidence of the energetic part of spectra inside and outside the magnetosphere. We discuss the reason for the changes of spectra at low magnetic shear.

Ion Kappa Distribution Parameters in the Magnetosphere of the Earth at Geocentric Distances Smaller Than 20 RE During Quiet Geomagnetic Conditions

“…The use of three kappa parameters instead of the two parameters of the Maxwell approximation permits to improve the description of magnetospheric instabilities (Navarro et al., 2015; Vinas et al., 2015; Yoon, 2014; Yoon et al., 2012), processes of acceleration for auroral electrons (Antonova & Ermakova, 2008; Olsson & Janhunen, 1998), and the formation of large‐scale auroral structures (Antonova et al., 2003). It helps to analyze the processes involved in the field line dipolarization (Runov et al., 2015), the ion penetration through the magnetopause (Kirpichev et al., 2017), and many other processes. The kappa model can help in the calculation of plasma pressure when the ion spectra are measured only in a limited energy range, and the contribution of the power law tails can be significant.…”

“…through the magnetopause (Kirpichev et al, 2017), and many other processes. The kappa model can help in the calculation of plasma pressure when the ion spectra are measured only in a limited energy range, and the contribution of the power law tails can be significant.…”

Ion and Electron κ Distribution Functions Along the Plasma Sheet

“…Indeed, the Tsallis formalism, which appeared as consequence of using nonadditive entropies, has the distribution function as the main element of the theory (Milovanov & Zelenyi, 2000;Tsallis, 1988Tsallis, , 2009. They have been successfully used, both observationally and theoretically (e.g., Navarro et al, 2015;Pierrard & Meyer-Vernet, 2017;Viñas et al, 2015;Yoon & Livadiotis, 2017), to describe particle distribution functions for velocity or energy (PEDF) 10.1029/2018GL078631 in a number of plasma environments, from the Earth's and other planets magnetospheres (Benson et al, 2013;Kirpichev et al, 2017;Viñas et al, 2005) to solar radio bursts (Cairns et al, 2017). They behave similar to the Maxwellian case for low and central energies but include a power law regime that operates toward higher energies, with a slope determined by the index.…”

Reviews in astronomy and space sciences

“…Moreover, typically, the description of the SW and MSH plasma and magnetic field is based on validity of the frozen-in hypothesis, which may be violated for low-speed plasma in the MSH (see Antonova et al, 2012 and references therein). Suggested mechanisms of plasma penetration through the magnetopause include finite gyroradius scattering, diffusion, wave-induced diffusion, impulsive penetration, and magnetic reconnection (Sibeck et al, 1999;Kirpichev et al, 2017;Fuselier, 2021). However, the presence of small-scale variations in the MSH favors additional ways for plasma transport across the magnetopause ; therefore, they can affect the magnetosphere processes.…”