Solar wind plasma interaction with Gerasimovich lunar magnetic anomaly

Abstract

We present the results of the first local hybrid simulations (particle ions and fluid electrons) for the solar wind plasma interaction with realistic lunar crustal fields. We use a three‐dimensional hybrid model of plasma and an empirical model of the Gerasimovich magnetic anomaly based on Lunar Prospector observations. We examine the effects of low and high solar wind dynamic pressures on this interaction when the Gerasimovich magnetic anomaly is located at nearly 20∘ solar zenith angle. We find that for low solar wind dynamic pressure, the crustal fields mostly deflect the solar wind plasma, form a plasma void at very close distances to the Moon (below 20 km above the surface), and reflect nearly 5% of the solar wind in charged form. In contrast, during high solar wind dynamic pressure, the crustal fields are more compressed, the solar wind is less deflected, and the lunar surface is less shielded from impinging solar wind flux, but the solar wind ion reflection is more locally intensified (up to 25%) compared to low dynamic pressures. The difference is associated with an electrostatic potential that forms over the Gerasimovich magnetic anomaly as well as the effects of solar wind plasma on the crustal fields during low and high dynamic pressures. Finally, we show that an antimoonward Hall electric field is the dominant electric field for ∼3 km altitude and higher, and an ambipolar electric field has a noticeable contribution to the electric field at close distances (<3 km) to the Moon.

The statistical mechanics of solar wind hydroxylation at the Moon, within lunar magnetic anomalies, and at Phobos

“…These swirls are associated with lunar magnetic anomalies, and it was suggested therein that the change in OH content was connected to the magnetic deflection of solar wind inflow into the region. Specifically, the magnetized regions within the swirls that possessed the lower OH content were found to have higher albedo and overlying horizontally directed magnetic fields that have been shown to retard incoming solar wind flow—both reducing the solar wind influx and reducing the ion energy by over 80% [ Fatemi et al ., ; Zimmerman et al ., ; Poppe et al ., ]. Regions with open field lines pointing vertically out to into the solar wind allowing ions to directly access the surface, and such regions appear similar in the visible and NIR to the nonmagnetic terrain.…”

“…For the magnetic anomalies, the solar wind ions have lost energy due to the retarding ambipolar and Hall E fields [Fatemi et al, 2015;Zimmerman et al, 2015;Poppe et al, 2016]-leading to shallower penetration into the regolith. In essence, we run both statistical mechanics and Monte Carlo modeling in the case of a less potent solar wind of lower overall flux and energy.…”

3d Pic Simulations of Collisionless Shocks at Lunar Magnetic Anomalies and Their Role in Forming Lunar Swirls

“…The computational investigation into mini-magnetospheres has become an area of considerable interest. A number of papers on hybrid (Bamford et al 2008;Gargaté et al 2008;Kallio et al 2012;Poppe et al 2012) and particle-in-cell (PIC) (Kallio et al 2012;Bamford et al 2013aBamford et al , 2013bBamford et al , 2015Deca et al 2014Deca et al , 2015Jarvinen et al 2014;Cruz et al 2015Cruz et al , 2016Dyadechkin et al 2015;Fatemi et al 2015) simulations have been authored, following from previous magnetohydrodynamic (MHD) simulations (Harnett & Winglee 2002Kurata et al 2005). Here we perform fully self-consistent PIC simulations in 2D and 3D, with a realistic proton-to-electron mass ratio.…”

On the confinement of lunar induced magnetic fields

“…We present the results after our simulations reached a steady state (t = 80 s). For more details about our model, see Holmström et al [2012] and Fatemi et al [2015].…”