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

Cold (eV) ions of ionospheric origin dominate the number density of most of the volume of the magnetosphere during most of the time. Supersonic flows of cold positive ions are common and can cause a negatively charged wake behind a positively charged spacecraft. The associated induced electric field can be observed and can be used to study the cold ions. We present observations from the Cluster and MMS spacecraft showing how a charged satellite, and also individual charged wire booms of &#160;an electric field instrument, can be used to investigate cold ion populations. Ionospheric ions affect large scales, including the Alfv&#233;n velocity and &#160;thus energy transport with waves and the magnetic reconnection rate. These ions also affect small-scale kinetic plasma physics, including the Hall physics and wave instabilities associated with magnetic reconnection. Concerning large scales, we summarize observations from several spacecraft and show that a typical total outflow rate of ionospheric ions is 1026 ions/s and that many of these ions stay cold also after a long time in the magnetosphere.&#160; Concerning small scales, we show examples of how cold ions modify the Hall physics of thin current sheets, including magnetic reconnection separatrices. On small kinetic scales the cold ions introduce a new length-scale, a gyro radius between the gyro radii of hot (keV) ions and electrons. The Hall currents carried by electrons can be partially cancelled by the cold ions when electrons and the magnetized cold ions ExB drift together. Also, close to a reconnection X-line an additional diffusion region can be formed (regions associated with hot and cold ions, and with electrons, total of three).

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Perpendicular Current Reduction Caused by Cold Ions of Ionospheric Origin in Magnetic Reconnection at the Magnetopause: Particle‐in‐Cell Simulations and Spacecraft Observations

Geophysical Research Letters ◽

10.1029/2018gl079051 ◽

2018 ◽

Vol 45 (19) ◽

pp. 10,033-10,042 ◽

Cited By ~ 4

Author(s):

Sergio Toledo‐Redondo ◽

Jérémy Dargent ◽

Nicolas Aunai ◽

Benoit Lavraud ◽

Mats André ◽

...

Keyword(s):

Magnetic Reconnection ◽

Particle In Cell ◽

Cold Ions ◽

Current Reduction

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Kinetic simulation of asymmetric magnetic reconnection with cold ions

Journal of Geophysical Research Space Physics ◽

10.1002/2016ja023831 ◽

2017 ◽

Vol 122 (5) ◽

pp. 5290-5306 ◽

Cited By ~ 12

Author(s):

J. Dargent ◽

N. Aunai ◽

B. Lavraud ◽

S. Toledo-Redondo ◽

M. A. Shay ◽

...

Keyword(s):

Magnetic Reconnection ◽

Kinetic Simulation ◽

Cold Ions

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Quantification of Cold-Ion Beams in a Magnetic Reconnection Jet

Frontiers in Astronomy and Space Sciences ◽

10.3389/fspas.2021.745264 ◽

2021 ◽

Vol 8 ◽

Author(s):

Yu-Xuan Li ◽

Wen-Ya Li ◽

Bin-Bin Tang ◽

C. Norgren ◽

Jian-Sen He ◽

...

Keyword(s):

Magnetic Reconnection ◽

Plasma Sheet ◽

Ion Beams ◽

Distribution Functions ◽

Diffusion Region ◽

Hot Plasma ◽

Order Of Magnitude ◽

Velocity Distribution Functions ◽

Cold Ions ◽

Field Lines

Cold (few eV) ions of ionospheric origin are widely observed in the lobe region of Earth’s magnetotail and can enter the ion jet region after magnetic reconnection is triggered in the magnetotail. Here, we investigate a magnetotail crossing with cold ions in one tailward and two earthward ion jets observed by the Magnetospheric Multiscale (MMS) constellation of spacecraft. Cold ions co-existing with hot plasma-sheet ions form types of ion velocity distribution functions (VDFs) in the three jets. In one earthward jet, MMS observe cold-ion beams with large velocities parallel to the magnetic fields, and we perform quantitative analysis on the ion VDFs in this jet. The cold ions, together with the hot ions, are reconnection outflow ions and are a minor population in terms of number density inside this jet. The average bulk speed of the cold-ion beams is approximately 38% larger than that of the hot plasma-sheet ions. The cold-ion beams inside the explored jet are about one order of magnitude colder than the hot plasma-sheet ions. These cold-ion beams could be accelerated by the Hall electric field in the cold ion diffusion region and the shrinking magnetic field lines through the Fermi effect.

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The Micro‐Macro Coupling of Mass‐Loading in Symmetric Magnetic Reconnection with Cold Ions

Geophysical Research Letters ◽

10.1029/2020gl090690 ◽

2021 ◽

Author(s):

Susanne F. Spinnangr ◽

Michael Hesse ◽

Paul Tenfjord ◽

Cecilia Norgren ◽

Hå kon M. Kolstø ◽

...

Keyword(s):

Magnetic Reconnection ◽

Mass Loading ◽

Cold Ions

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Acceleration of cold ions at separatrices of symmetric collisionless magnetic reconnection

10.5194/egusphere-egu2020-18886 ◽

2020 ◽

Author(s):

Evgeny Gordeev ◽

Andrey Divin ◽

Ivan Zaitsev ◽

Vladimir Semenov ◽

Yuri Khotyaintsev ◽

...

Keyword(s):

Electric Field ◽

Magnetic Reconnection ◽

Electric Fields ◽

Electrostatic Potential ◽

Potential Drop ◽

Local Electron ◽

One Dimensional ◽

Particle In Cell ◽

Background Population ◽

Cold Ions

Separatrices of magnetic reconnection host intense perpendicular Hall electric fields produced by decoupling of ion and electron components and associated with the in-plane electrostatic potential drop between inflow and outflow regions. The width of these structures is several local electron inertial lengths, which is small enough to demagnetize ions as they cross the layer. We investigate temperature dependence of ion acceleration at separatrices by means of 2D Particle-in-Cell (PIC) simulations of magnetic reconnection with only cold or hot ion background population. The separatrix Hall electric field is balanced by the inertia term in cold background simulations, the effect indicative of the quasi-steady local perpendicular acceleration. The electric field introduces a cross-field beam of unmagnetized particles which makes the temperature strongly non-gyrotropic and susceptible to sub-ion scale instabilities. This acceleration mechanism nearly vanishes for hot ion background simulations. Particle-in-cell simulations are complemented by one-dimensional test particle calculations, which show that the hot ion particles experience scattering in energies after crossing the accelerating layer, whereas cold ions are uniformly energized up to the energies comparable to the electrostatic potential drop between the inflow and outflow regions.

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Modification of the Hall physics in magnetic reconnection due to cold ions at the Earth's magnetopause

Geophysical Research Letters ◽

10.1002/2015gl065129 ◽

2015 ◽

Vol 42 (15) ◽

pp. 6146-6154 ◽

Cited By ~ 31

Author(s):

S. Toledo-Redondo ◽

A. Vaivads ◽

M. André ◽

Yu. V. Khotyaintsev

Keyword(s):

Magnetic Reconnection ◽

Cold Ions

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A large rotating structure around AB Doradus A at VLBI scale

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009785 ◽

2019 ◽

Vol 15 (S354) ◽

pp. 189-194

Author(s):

J. B. Climent ◽

J. C. Guirado ◽

R. Azulay ◽

J. M. Marcaide

Keyword(s):

Magnetic Reconnection ◽

Main Sequence ◽

Complex Structure ◽

Main Sequence Star ◽

Polar Cap ◽

Vlbi Observations ◽

Rotating Structure ◽

Source Structure ◽

Expected Position

AbstractWe report the results of three VLBI observations of the pre-main-sequence star AB Doradus A at 8.4 GHz. With almost three years between consecutive observations, we found a complex structure at the expected position of this star for all epochs. Maps at epochs 2007 and 2010 show a double core-halo morphology while the 2013 map reveals three emission peaks with separations between 5 and 18 stellar radii. Furthermore, all maps show a clear variation of the source structure within the observing time. We consider a number of hypothesis in order to explain such observations, mainly: magnetic reconnection in loops on the polar cap, a more general loop scenario and a close companion to AB Dor A.

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