High‐density magnetospheric He + at the dayside magnetopause and its effect on magnetic reconnection

<p>Dayside magnetic reconnection at the magnetopause, which is a major driver of space weather, is studied for the first time in a three-dimensional (3D) realistic setup using the Vlasiator hybrid-Vlasov kinetic model. A noon&#8211;midnight meridional plane simulation is extended in the dawn&#8211;dusk direction to cover 7 Earth radii. The southward interplanetary magnetic field causes magnetic reconnection to occur at the subsolar magnetopause. Perturbations arising from kinetic instabilities in the magnetosheath appear to modulate the reconnection. Its characteristics are consistent with multiple, bursty, and patchy magnetopause reconnection. It is shown that the kinetic behavior of the plasma, as simulated by the model, has consequences on the applicability of methods such as the four-field junction to identify and analyse magnetic reconnection in 3D kinetic simulations.</p>

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Concerning the occurrence pattern of flux transfer events on the dayside magnetopause

Annales Geophysicae ◽

10.5194/angeo-27-895-2009 ◽

2009 ◽

Vol 27 (2) ◽

pp. 895-903 ◽

Cited By ~ 7

Author(s):

D. G. Sibeck

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Magnetic Reconnection ◽

Interplanetary Magnetic Field ◽

Flux Transfer Events ◽

Dayside Magnetopause ◽

Two Factors ◽

Flux Transfer ◽

Occurrence Pattern ◽

The Magnetic Field

Abstract. We present an analytical model for the magnetic field perturbations associated with flux transfer events (FTEs) on the dayside magnetopause as a function of the shear between the magnetosheath and magnetospheric magnetic fields and the ratio of their strengths. We assume that the events are produced by component reconnection along subsolar reconnection lines with tilts that depend upon the orientation of the interplanetary magnetic field (IMF), and show that the amplitudes of the perturbations generated during southward IMF greatly exceed those during northward IMF. As a result, even if the distributions of magnetic reconnection burst durations/event dimensions are identical during periods of northward and southward IMF orientation, events occurring for southward IMF orientations must predominate in surveys of dayside events. Two factors may restore the balance between events occurring for northward and southward IMF orientations on the flanks of the magnetosphere. Events generated on the dayside magnetopause during periods of southward IMF move poleward, while those generated during periods of northward IMF slip dawnward or duskward towards the flanks. Due to differing event and magnetospheric magnetic field orientations, events that produce weak signatures on the dayside magnetopause during intervals of northward IMF orientation may produce strong signatures on the flanks.

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A case study of dayside reconnection under extremely low solar wind density conditions

Annales Geophysicae ◽

10.5194/angeo-26-3571-2008 ◽

2008 ◽

Vol 26 (11) ◽

pp. 3571-3583

Author(s):

R. Maggiolo ◽

J. A. Sauvaud ◽

I. Dandouras ◽

E. Luceck ◽

H. Rème

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Reconnection ◽

High Speed ◽

Radial Distance ◽

Plasma Jets ◽

Solar Wind Density ◽

Ion Distribution ◽

Dayside Magnetopause ◽

Field Lines

Abstract. From 15 February 2004, 20:00 UT to 18 February 2004, 01:00 UT, the solar wind density dropped to extremely low values (about 0.35 cm−3). On 17 February, between 17:45 UT and 18:10 UT, the CLUSTER spacecraft cross the dayside magnetopause several times at a large radial distance of about 16 RE. During each of these crossings, the spacecraft detect high speed plasma jets in the dayside magnetopause and boundary layer. These observations are made during a period of southward and dawnward Interplanetary Magnetic Field (IMF). The magnetic shear across the local magnetopause is ~90° and the magnetosheath beta is very low (~0.15). We evidence the presence of a magnetic field of a few nT along the magnetopause normal. We also show that the plasma jets, accelerated up to 600 km/s, satisfy the tangential stress balance. These findings strongly suggest that the accelerated jets are due to magnetic reconnection between interplanetary and terrestrial magnetic field lines northward of the satellites. This is confirmed by the analysis of the ion distribution function that exhibits the presence of D shaped distributions and of a reflected ion population as predicted by theory. A quantitative analysis of the reflected ion population reveals that the reconnection process lasts about 30 min in a reconnection site located at a very large distance of several tens RE from the Cluster spacecraft. We also estimate the magnetopause motion and thickness during this event. This paper gives the first experimental study of magnetic reconnection during such rare periods of very low solar wind density. The results are discussed in the frame of magnetospheric response to extremely low solar wind density conditions.

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Dependence of magnetopause reconnection events on interplanetary parameters

10.5194/egusphere-egu2020-5163 ◽

2020 ◽

Author(s):

Walter Gonzalez ◽

Daiki Koga

Keyword(s):

Solar Wind ◽

Mach Number ◽

Electric Field ◽

Magnetic Reconnection ◽

Flow Direction ◽

Time History ◽

Normal Vector ◽

Dayside Magnetopause ◽

Energy And Momentum ◽

Magnetopause Reconnection

<p>Magnetic reconnection permits topological rearrangements of the interplanetary and magnetospheric magnetic fields and the entry of solar wind mass, energy, and momentum into the magnetosphere. Thus, magnetic reconnection is a key issue to understand space weather. However, it hasnot been fully understood yet under which interplanetary/magnetosheath conditions magnetic reconnection takes place more effectively at the dayside magnetopause. For this purpose,&#160; in the present study 25 dayside magnetopause reconnection events are investigated using the Time History of Events and Macroscale Interactions during Substorms ( THEMIS ) spacecraft &#160;observations. It was found, (1) that the reconnection electric field is proportional to the interplanetary electric field, (2) that the reconnection electric field is inversely proportional to the solar wind-Alfv&#233;n Mach number, &#160;(3) that thereconnection outflow speed is proportional to the solar wind Alfv&#233;n speed, and (4) that the reconnection outflow speed is&#160; inversely proportional to the magnetosheath plasma beta. Finally, it is shown that the range of magnetic shear angles for which magnetic reconnection should occur is restricted to large shears as the magnetosheath flow direction becomes more perpendicular to the direction of the local magnetopause normal vector. Since these results refer to fairly typical solar wind-Alfv&#233;n Mach number condition, they may not apply to more extreme cases.</p>

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On the location of dayside magnetic reconnection during an interval of duskward oriented IMF

Annales Geophysicae ◽

10.5194/angeo-25-219-2007 ◽

2007 ◽

Vol 25 (1) ◽

pp. 219-238 ◽

Cited By ~ 15

Author(s):

J. A. Wild ◽

S. E. Milan ◽

J. A. Davies ◽

M. W. Dunlop ◽

D. M. Wright ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Reconnection ◽

Local Magnetic Field ◽

High Latitudes ◽

Reconnection Rate ◽

Flux Tubes ◽

Dayside Magnetopause ◽

Line Passing ◽

Open Flux

Abstract. We present space- and ground-based observations of the signatures of magnetic reconnection during an interval of duskward-oriented interplanetary magnetic field on 25 March 2004. In situ field and plasma measurements are drawn from the Double Star and Cluster satellites during traversals of the pre-noon sector dayside magnetopause at low and high latitudes, respectively. These reveal the typical signatures of flux transfer events (FTEs), namely bipolar perturbations in the magnetic field component normal to the local magnetopause, enhancements in the local magnetic field strength and mixing of magnetospheric and magnetosheath plasmas. Further evidence of magnetic reconnection is inferred from the ground-based signatures of pulsed ionospheric flow observed over an extended interval. In order to ascertain the location of the reconnection site responsible for the FTEs, a simple model of open flux tube motion over the surface of the magnetopause is employed. A comparison of the modelled and observed motion of open flux tubes (i.e. FTEs) and plasma flow in the magnetopause boundary layer indicates that the FTEs observed at both low and high latitudes were consistence with the existence of a tilted X-line passing through the sub-solar region, as suggested by the component reconnection paradigm. While a high latitude X-line (as predicted by the anti-parallel description of reconnection) may have been present, we find it unlikely that it could have been responsible for the FTEs observed in the pre-noon sector under the observed IMF conditions. Finally, we note that throughout the interval, the magnetosphere was bathed in ULF oscillations within the solar wind electric field. While no one-to-one correspondence with the pulsed reconnection rate suggested by the ground-based observation of pulsed ionospheric flow has been demonstrated, we note that similar periodicity oscillations were observed throughout the solar wind-magnetosphere-ionosphere system. These findings are consistent with previously proposed mechanisms of solar wind modulation of the dayside reconnection rate.

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Review of Mercury’s dynamic magnetosphere: Post-MESSENGER era and comparative magnetospheres

Science China Earth Sciences ◽

10.1007/s11430-021-9828-0 ◽

2021 ◽

Author(s):

Weijie Sun ◽

Ryan M. Dewey ◽

Sae Aizawa ◽

Jia Huang ◽

James A. Slavin ◽

...

Keyword(s):

Magnetic Reconnection ◽

Review Paper ◽

Transfer Event ◽

Magnetic Structures ◽

Open Questions ◽

Dayside Magnetopause ◽

The Future ◽

Spacecraft Mission ◽

Joint Mission ◽

Particle Energization

AbstractThis review paper summarizes the research of Mercury’s magnetosphere in the Post-MESSENGER era and compares its dynamics to those in other planetary magnetospheres, especially to those in Earth’s magnetosphere. This review starts by introducing the planet Mercury, including its interplanetary environment, magnetosphere, exosphere, and conducting core. The frequent and intense magnetic reconnection on the dayside magnetopause, which is represented by the flux transfer event “shower”, is reviewed on how they depend on magnetosheath plasma β and magnetic shear angle across the magnetopause, following by how it contributes to the flux circulation and magnetosphere-surface-exosphere coupling. In the next, Mercury’s magnetosphere under extreme solar events, including the core induction and the reconnection erosion on the dayside magnetosphere, the responses of the nightside magnetosphere, are reviewed. Then, the dawn-dusk properties of the plasma sheet, including the features of the ions, the structure of the current sheet, and the dynamics of magnetic reconnection, are summarized. The last topic is devoted to the particle energization in Mercury’s magnetosphere, which includes the energization of the Kelvin-Helmholtz waves on the magnetopause boundaries, reconnection-generated magnetic structures, and the cross-tail electric field. In each chapter, the last section discusses the open questions related to each topic, which can be considered by the simulations and the future spacecraft mission. We end this paper by summarizing the future BepiColombo opportunities, which is a joint mission of ESA and JAXA and is en route to Mercury.

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