A model of the magnetosheath magnetic field during magnetic clouds

Turc, Lucile; Fontaine, Dominique; Savoini, Philippe; Kilpua, Emilia

doi:10.5194/angeo-32-157-2014

Cited by 17 publications

(50 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These variations are related to the configuration, quasi-parallel or quasiperpendicular, encountered at the bow shock. In addition, Turc et al (2014) determine the location of anti-parallel fields, that is, favourable to reconnection, along the magnetopause and find patterns very different from that expected from the MC's magnetic field orientation upstream of the shock. For example, an initially northward field during an MC can turn south in a part of the magnetosheath and result in a region of anti-parallel fields near the subsolar point.…”

mentioning

confidence: 98%

“…The magnetic fields at the leading or the trailing edge of the MC are also sometimes invoked to account for the effects observed inside the magnetosphere (Zhang et al, 2004). Some recent studies hint at the pivotal role played by the magnetosheath in the solar-wind-magnetosphere coupling, which is still poorly understood (Šafránková et al, 2009;Lavraud et al, 2013;Turc et al, 2014).…”

mentioning

confidence: 99%

“…A model of the magnetosheath magnetic field designed for MC studies has recently been introduced by Turc et al (2014). In this paper, they investigate the impact of the bow shock's crossing on synthetic flux ropes.…”

mentioning

confidence: 99%

“…For example, an initially northward field during an MC can turn south in a part of the magnetosheath and result in a region of anti-parallel fields near the subsolar point. Therefore, Turc et al (2014) suggest that the impact of an MC on the magnetosphere can be strongly modified by the processes occurring at the shock and inside the magnetosheath.…”

mentioning

confidence: 99%

“…The aim is to investigate whether the magnetic structure of MCs is modified across the bow shock and in the magnetosheath, and to quantitatively compare the spacecraft observations to the predictions of the magnetosheath model developed by Turc et al (2014). We have selected four typical MC events during which one or several spacecraft are located inside the Earth's magnetosheath, at least for several hours during the MC's passage.…”

mentioning

confidence: 99%

See 4 more Smart Citations

Magnetic clouds' structure in the magnetosheath as observed by Cluster and Geotail: four case studies

et al. 2014

Self Cite

View full text Add to dashboard Cite

Abstract. Magnetic clouds (MCs) are large-scale magnetic flux ropes ejected from the Sun into the interplanetary space. They play a central role in solar-terrestrial relations as they can efficiently drive magnetic activity in the near-Earth environment. Their impact on the Earth's magnetosphere is often attributed to the presence of southward magnetic fields inside the MC, as observed in the upstream solar wind. However, when they arrive in the vicinity of the Earth, MCs first encounter the bow shock, which is expected to modify their properties, including their magnetic field strength and direction. If these changes are significant, they can in turn affect the interaction of the MC with the magnetosphere. In this paper, we use data from the Cluster and Geotail spacecraft inside the magnetosheath and from the Advanced Composition Explorer (ACE) upstream of the Earth's environment to investigate the impact of the bow shock's crossing on the magnetic structure of MCs. Through four example MCs, we show that the evolution of the MC's structure from the solar wind to the magnetosheath differs largely from one event to another. The smooth rotation of the MC can either be preserved inside the magnetosheath, be modified, i.e. the magnetic field still rotates slowly but at different angles, or even disappear. The alteration of the magnetic field orientation across the bow shock can vary with time during the MC's passage and with the location inside the magnetosheath. We examine the conditions encountered at the bow shock from direct observations, when Cluster or Geotail cross it, or indirectly by applying a magnetosheath model. We obtain a good agreement between the observed and modelled magnetic field direction and shock configuration, which varies from quasiperpendicular to quasi-parallel in our study. We find that the variations in the angle between the magnetic fields in the solar wind and in the magnetosheath are anti-correlated with the variations in the shock obliquity. When the shock is in a quasi-parallel regime, the magnetic field direction varies significantly from the solar wind to the magnetosheath. In such cases, the magnetic field reaching the magnetopause cannot be approximated by the upstream magnetic field. Therefore, it is important to take into account the conditions at the bow shock when estimating the impact of an MC with the Earth's environment because these conditions are crucial in determining the magnetosheath magnetic field, which then interacts with the magnetosphere.

show abstract

mentioning

confidence: 98%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Magnetic clouds' structure in the magnetosheath as observed by Cluster and Geotail: four case studies

et al. 2014

Self Cite

View full text Add to dashboard Cite

show abstract

3D hybrid simulations of the interaction of a magnetic cloud with a bow shock

et al. 2015

Self Cite

View full text Add to dashboard Cite

In this paper, we investigate the interaction of a magnetic cloud (MC) with a planetary bow shock using hybrid simulations. It is the first time to our knowledge that this interaction is studied using kinetic simulations which include self‐consistently both the ion foreshock and the shock wave dynamics. We show that when the shock is in a quasi‐perpendicular configuration, the MC's magnetic structure in the magnetosheath remains similar to that in the solar wind, whereas it is strongly altered downstream of a quasi‐parallel shock. The latter can result in a reversal of the magnetic field north‐south component in some parts of the magnetosheath. We also investigate how the MC affects in turn the outer parts of the planetary environment, i.e., from the foreshock to the magnetopause. We find the following: (i) The decrease of the Alfvén Mach number at the MC's arrival causes an attenuation of the foreshock region because of the weakening of the bow shock. (ii) The foreshock moves along the bow shock's surface, following the rotation of the MC's magnetic field. (iii) Owing to the low plasma beta, asymmetric flows arise inside the magnetosheath, due to the magnetic tension force which accelerates the particles in some parts of the magnetosheath and slows them down in others. (iv) The quasi‐parallel region forms a depression in the shock's surface. Other deformations of the magnetopause and the bow shock are also highlighted. All these effects can contribute to significantly modify the solar wind/magnetosphere coupling during MC events.

show abstract

Cone angle control of the interaction of magnetic clouds with the Earth's bow shock

Turc

Escoubet

Fontaine

et al. 2016

Geophysical Research Letters

Self Cite

View full text Add to dashboard Cite

We study the interaction of magnetic clouds (MCs) with the near‐Earth environment. Recent works suggest that the bow shock crossing may modify significantly the magnetic structure of an MC, and thus its ability to drive geomagnetic storms. This change is largely controlled by the bow shock configuration, which depends on the upstream interplanetary magnetic field (IMF) orientation. From the distribution of the magnetic field orientation in 152 Earth‐impacting MCs, we determine for the first time the typical shock configuration during MC events. We find that 56% (6.3%) of the time, the subsolar bow shock configuration is exclusively quasi‐perpendicular (quasi‐parallel). The rest of the time, both configurations coexist. Furthermore, using a subset of 63 MCs observed simultaneously in the solar wind and in the dayside magnetosheath, we determine the magnitude of the magnetic field alteration, how it depends on the shock configuration, and how it relates to the IMF cone angle.

show abstract

A model of the magnetosheath magnetic field during magnetic clouds

Cited by 17 publications

References 42 publications

Magnetic clouds' structure in the magnetosheath as observed by Cluster and Geotail: four case studies

Magnetic clouds' structure in the magnetosheath as observed by Cluster and Geotail: four case studies

3D hybrid simulations of the interaction of a magnetic cloud with a bow shock

Cone angle control of the interaction of magnetic clouds with the Earth's bow shock

Contact Info

Product

Resources

About