S. Toledo-Redondo

Currents and associated electron scattering and bouncing near the diffusion region at Earth's magnetopause

Based on high-resolution measurements from NASAs Magnetospheric Multiscale mission, we present the dynamics of electrons associated with current systems observed near the diffusion region of magnetic reconnection at Earths magnetopause. Using pitch angle distributions (PAD) and magnetic curvature analysis, we demonstrate the occurrence of electron scattering in the curved magnetic field of the diffusion region down to energies of 20 eV. We show that scattering occurs closer to the current sheet as the electron energy decreases. The scattering of inflowing electrons, associated with field-aligned electrostatic potentials and Hall currents, produces a new population of scattered electrons with broader PAD which bounce back and forth in the exhaust. Except at the center of the diffusion region the two populations are collocated and appear to behave adiabatically: the inflowing electron PAD focuses inward (toward lower magnetic field), while the bouncing population PAD gradually peaks at 90° away from the center (where it mirrors owing to higher magnetic field and probable field-aligned potentials).

Lower hybrid waves in the ion diffusion and magnetospheric inflow regions

The role and properties of lower hybrid waves in the ion diffusion region and magnetospheric inflow region of asymmetric reconnection are investigated using the Magnetospheric Multiscale (MMS) miss ...

Kinetic evidence of magnetic reconnection due to Kelvin-Helmholtz waves

The Kelvin-Helmholtz (KH) instability at the Earths magnetopause is predominantly excited during northward interplanetary magnetic field (IMF). Magnetic reconnection due to KH waves has been suggested as one of the mechanisms to transfer solar wind plasma into the magnetosphere. We investigate KH waves observed at the magnetopause by the Magnetospheric Multiscale (MMS) mission; in particular, we study the trailing edges of KH waves with Alfvenic ion jets. We observe gradual mixing of magnetospheric and magnetosheath ions at the boundary layer. The magnetospheric electrons with energy up to 80 keV are observed on the magnetosheath side of the jets, which indicates that they escape into the magnetosheath through reconnected magnetic field lines. At the same time, the low-energy (below 100 eV) magnetosheath electrons enter the magnetosphere and are heated in the field-aligned direction at the high-density edge of the jets. Our observations provide unambiguous kinetic evidence for ongoing reconnection due to KH waves.

Magnetic reconnection and modification of the Hall physics due to cold ions at the magnetopause.

Observations by the four Magnetospheric Multiscale spacecraft are used to investigate the Hall physics of a magnetopause magnetic reconnection separatrix layer. Inside this layer of currents and st ...

Cold ion demagnetization near the X‐line of magnetic reconnection

Although the effects of magnetic reconnection in magnetospheres can be observed at planetary scales, reconnection is initiated at electron scales in a plasma. Surrounding the electron diffusion reg ...

Kinetic simulation of asymmetric magnetic reconnection with cold ions

At the dayside magnetopause, the magnetosphere often contains a cold ion population of ionospheric origin. This population is not always detectable by particle instruments due to its low energy, despite having an important contribution to the total ion density and therefore an impact on key plasma processes such as magnetic reconnection. The exact role and implications of this low temperature population are still not well known, and has not been adressed with numerical simulation before. We present 2D fully kinetic simulations of asymmetric magnetic reconnection with and without a cold ion population on the magnetospheric side of the magnetopause, but sharing the same total density, temperature and magnetic field profiles. The comparison of the simulations suggests that cold ions directly impact signatures recently suggested as a good marker of the X-line region: the Larmor electric field. Our simulations reveal that this electric field, initially present all along the magnetospheric separatrix, is related to the bounce of magnetosheath ions at the magnetopause magnetic field reversal through Speiser-like orbits. Once reconnection widens the current sheet away from the X-line, the bouncing stops and the electric field signature remains solely confined near the X-line. When cold ions are present, however, their very low temperature enables them to E × B drift in the electric field structure. If their density is large enough compared to other ions, their contribution to the momentum equation is capable of maintaining the signature away from the X-line. This effect must be taken into account when analyzing in situ spacecraft measurements.

Full 3-D TLM simulations of the Earth-ionosphere cavity : Effect of conductivity on the Schumann resonances

Schumann resonances can be found in planetary atmospheres, inside the cavity formed by the conducting surface of the planet and the lower ionosphere. They are a powerful tool to investigate both th ...

Three‐scale structure of diffusion region in the presence of cold ions

Kinetic simulations and spacecraft observations typically display the two-scale structure of collisionless diffusion region (DR), with electron and ion demagnetization scales governing the spatial ...

Energy budget and mechanisms of cold ion heating in asymmetric magnetic reconnection

Cold ions (few tens of eV) of ionospheric origin are commonly observed on the magnetospheric side of the Earths dayside magnetopause. As a result, they can participate in magnetic reconnection, ch ...

Cold Ionospheric Ions in the Magnetic Reconnection Outflow Region

Magnetosheath plasma usually determines properties of asymmetric magnetic reconnection at the subsolar region of Earths magnetopause. However, cold plasma that originated from the ionosphere can a ...