scholarly journals Multiple transpolar auroral arcs reveal insight about coupling processes in the Earth’s magnetotail

2020 ◽  
Vol 117 (28) ◽  
pp. 16193-16198
Author(s):  
Qing-He Zhang ◽  
Yong-Liang Zhang ◽  
Chi Wang ◽  
Michael Lockwood ◽  
Hui-Gen Yang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Three Dimensional ◽  
Formation Mechanisms ◽  
Solar Wind Flow ◽  
High Latitude Ionosphere ◽  
Magnetospheric Boundary ◽  
Energy And Momentum ◽  
Magnetosphere Plasma ◽  
Auroral Arcs ◽  
Coupling Processes

A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high-latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. The formation and evolution of TPA offers clues about processes transferring energy and momentum from the solar wind to the magnetosphere and ionosphere during a northward IMF. However, their formation mechanisms remain poorly understood and controversial. We report a mechanism identified from multiple-instrument observations of unusually bright, multiple TPAs and simulations from a high-resolution three-dimensional (3D) global MagnetoHydroDynamics (MHD) model. The observations and simulations show an excellent agreement and reveal that these multiple TPAs are generated by precipitating energetic magnetospheric electrons within field-aligned current (FAC) sheets. These FAC sheets are generated by multiple-flow shear sheets in both the magnetospheric boundary produced by Kelvin–Helmholtz instability between supersonic solar wind flow and magnetosphere plasma, and the plasma sheet generated by the interactions between the enhanced earthward plasma flows from the distant tail (less than −100 RE) and the enhanced tailward flows from the near tail (about −20 RE). The study offers insight into the complex solar wind-magnetosphere-ionosphere coupling processes under a northward IMF condition, and it challenges existing paradigms of the dynamics of the Earth’s magnetosphere.

Multiple transpolar auroral arcs reveal new insight about coupling processes in the Earth’s magnetotail

2021 ◽  
Author(s):  
Qing-He Zhang ◽  
Yong-Liang Zhang ◽  
Chi Wang ◽  
Michael Lockwood ◽  
Hui-Gen Yang ◽  
...  
Keyword(s):  
Solar Wind ◽  
Three Dimensional ◽  
Formation Mechanisms ◽  
The Earth ◽  
Solar Wind Flow ◽  
High Latitude Ionosphere ◽  
Energy And Momentum ◽  
Magnetosphere Plasma ◽  
Auroral Arcs ◽  
Coupling Processes

<p><strong>A distinct class of aurora, called transpolar auroral arc (TPA) (in some cases called “theta” aurora), appears in the extremely high latitude ionosphere of the Earth when interplanetary magnetic field (IMF) is northward. The formation and evolution of TPA offers clues about processes transferring energy and momentum from the solar wind to the magnetosphere and ionosphere during a northward IMF. However, their formation mechanisms remain poorly understood and controversial. We report a new mechanism identified from multiple-instrument observations of unusually bright, multiple TPAs and simulations from a high-resolution three-dimensional global MagnetoHydroDynamics (MHD) model. The observations and simulations show an excellent agreement and reveal that these multiple TPAs are generated by precipitating energetic magnetospheric electrons within field-aligned current (FAC) sheets. These FAC sheets are generated by multiple flow shear sheets in both the magnetospheric boundary produced by Kelvin-Helmholtz instability between super-sonic solar wind flow and magnetosphere plasma, and the plasma sheet generated by the interactions between the enhanced earthward plasma flows from the distant tail (less than -100 R<sub>E</sub>) and the enhanced tailward flows from the near tail (about -20 R<sub>E</sub>). The study offers a new insight into the complex solar wind-magnetosphere-ionosphere coupling processes under a northward IMF condition, and it challenges existing paradigms of the dynamics of the Earth’s magnetosphere.</strong></p>

scholarly journals Solar wind flow near a reconnection site at the dayside magnetopause: development of an existing three-dimensional model

2007 ◽  
Vol 73 (2) ◽  
pp. 145-151 ◽  
Author(s):  
LARS G. WESTERBERG ◽  
H.O. ÅKERSTEDT
Keyword(s):  
Solar Wind ◽  
Three Dimensional ◽  
Wind Flow ◽  
Arbitrary Orientation ◽  
Plasma Velocity ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Dayside Magnetopause ◽  
Solar Wind Flow ◽  
Reconnection Site

Abstract.An improvement of an existing three-dimensional analytical model describing the solar wind flow near a reconnection site at the dayside magnetopause is reported. Introducing an arbitrary orientation of the reconnection line, general solutions for the plasma velocity and magnetic field during the transition of the magnetopause are presented, together with the development of the magnetopause transition layer away from the reconnection site.

Recent ionospheric observations relating to solar-wind-magnetosphere coupling

1989 ◽  
Vol 328 (1598) ◽  
pp. 93-105 ◽  
Keyword(s):  
Solar Wind ◽  
Interplanetary Medium ◽  
Spatial Scales ◽  
Driving Mechanism ◽  
Reconnection Rate ◽  
Dayside Magnetopause ◽  
Solar Wind Flow ◽  
High Latitude Ionosphere ◽  
Low Altitude ◽  
Statistical Surveys

Simultaneous observations in the high-latitude ionosphere and in the near-Earth interplanetary medium have revealed the control exerted by the interplanetary magnetic field and the solar wind flow on field-perpendicular convection of plasma in both the ionosphere and the magnetosphere. Previous studies, using statistical surveys of data from both low-altitude polar-orbiting satellites and ground-based radars and magnetometers, have established that magnetic reconnection at the dayside magnetopause is the dominant driving mechanism for convection. More recently, ground-based data and global auroral images of higher temporal resolution have been obtained and used to study the response of the ionospheric flows to changes in the interplanetary medium. These observations show that ionospheric convection responds rapidly (within a few minutes) to both increases and decreases in the reconnection rate over a range of spatial scales, as well as revealing transient enhancements which are also thought to be related to magnetopause phenomena. Such results emphasize the potential of ground-based radars and other remotesensing instruments for studies of the Earth’s interaction with the interplanetary medium.

scholarly journals Reflection-driven magnetohydrodynamic turbulence in the solar atmosphere and solar wind

2019 ◽  
Vol 85 (4) ◽  
Author(s):  
Benjamin D. G. Chandran ◽  
Jean C. Perez
Keyword(s):  
Solar Wind ◽  
Heating Rate ◽  
Three Dimensional ◽  
Power Spectra ◽  
Inertial Range ◽  
Magnetic Flux Tube ◽  
Analytic Model ◽  
Mhd Turbulence ◽  
Background Magnetic Field ◽  
Turbulent Heating

We present three-dimensional direct numerical simulations and an analytic model of reflection-driven magnetohydrodynamic (MHD) turbulence in the solar wind. Our simulations describe transverse, non-compressive MHD fluctuations within a narrow magnetic flux tube that extends from the photosphere, through the chromosphere and corona and out to a heliocentric distance  $r$ of 21 solar radii  $(R_{\odot })$ . We launch outward-propagating ‘ $\boldsymbol{z}^{+}$ fluctuations’ into the simulation domain by imposing a randomly evolving photospheric velocity field. As these fluctuations propagate away from the Sun, they undergo partial reflection, producing inward-propagating ‘ $\boldsymbol{z}^{-}$ fluctuations’. Counter-propagating fluctuations subsequently interact, causing fluctuation energy to cascade to small scales and dissipate. Our analytic model incorporates dynamic alignment, allows for strongly or weakly turbulent nonlinear interactions and divides the $\boldsymbol{z}^{+}$ fluctuations into two populations with different characteristic radial correlation lengths. The inertial-range power spectra of $\boldsymbol{z}^{+}$ and $\boldsymbol{z}^{-}$ fluctuations in our simulations evolve toward a $k_{\bot }^{-3/2}$ scaling at $r>10R_{\odot }$ , where $k_{\bot }$ is the wave-vector component perpendicular to the background magnetic field. In two of our simulations, the $\boldsymbol{z}^{+}$ power spectra are much flatter between the coronal base and $r\simeq 4R_{\odot }$ . We argue that these spectral scalings are caused by: (i) high-pass filtering in the upper chromosphere; (ii) the anomalous coherence of inertial-range $\boldsymbol{z}^{-}$ fluctuations in a reference frame propagating outwards with the $\boldsymbol{z}^{+}$ fluctuations; and (iii) the change in the sign of the radial derivative of the Alfvén speed at $r=r_{\text{m}}\simeq 1.7R_{\odot }$ , which disrupts this anomalous coherence between $r=r_{\text{m}}$ and $r\simeq 2r_{\text{m}}$ . At $r>1.3R_{\odot }$ , the turbulent heating rate in our simulations is comparable to the turbulent heating rate in a previously developed solar-wind model that agreed with a number of observational constraints, consistent with the hypothesis that MHD turbulence accounts for much of the heating of the fast solar wind.

scholarly journals Three-dimensional MHD modeling of the solar wind structures associated with 13 December 2006 coronal mass ejection

2009 ◽  
Vol 114 (A10) ◽  
pp. n/a-n/a ◽  
Author(s):  
R. Kataoka ◽  
T. Ebisuzaki ◽  
K. Kusano ◽  
D. Shiota ◽  
S. Inoue ◽  
...  
Keyword(s):  
Solar Wind ◽  
Coronal Mass Ejection ◽  
Three Dimensional ◽  
Mhd Modeling ◽  
Mass Ejection
Sign in / Sign up

Export Citation Format

Share Document