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 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.

(Non)-radial propagation of the solar wind flow

2020 ◽  
Author(s):  
Zdeněk Němeček ◽  
Tereza Ďurovcová ◽  
Jana Šafránková ◽  
Jiří Šimůnek ◽  
John D. Richardson ◽  
...  
Keyword(s):  
Solar Wind ◽  
Radial Velocity ◽  
Orbital Motion ◽  
Wind Flow ◽  
The Sun ◽  
Mars Express ◽  
The Earth ◽  
Solar Wind Flow ◽  
Magnetospheric Tail ◽  
Radial Propagation

<p>The solar wind aberration due to non-radial velocity components and the Earth orbital motion is important for the overall magnetosphere geometry because the magnetospheric tail is aligned with the solar wind flow. This paper investigates an evolution of non-radial components of the solar wind flow along the path from the Sun to 6 AU. A comparison of observations at 1 AU and closer to or further from the Sun based on measurements of many spacecraft at different locations in the heliosphere (Wind, ACE, Spektr-R, THEMIS B and C, Helios 1 and 2, Mars-Express, Voyager 1 and 2) shows that (i) the average values of non-radial components vary with the distance from the Sun and (ii) they differ according to solar wind streams.</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 Occurrence rate of magnetic holes between 0.72 and 1 AU: comparative study of Cluster and VEX data

2011 ◽  
Vol 29 (5) ◽  
pp. 717-722 ◽  
Author(s):  
O. A. Amariutei ◽  
S. N. Walker ◽  
T. L. Zhang
Keyword(s):  
Solar Wind ◽  
Occurrence Rate ◽  
Wind Flow ◽  
The Sun ◽  
Common Features ◽  
The Earth ◽  
Magnetic Field Magnitude ◽  
Solar Wind Flow ◽  
Stable Plasma ◽  
The Magnetic Field

Abstract. Localised depressions in the magnetic field magnitude, or magnetic holes, are common features in many regions of solar system plasma. Two distinct mechanisms for their generation have been proposed. The first proposed that the structures are generated locally, close to the point of observation. The alternative has been proposed by Russell et al. (2008), who suggest that the observed magnetic holes represent nonlinear mirror structures that can be carried by the solar wind over vast distances of mirror stable plasma. According to Russell et al. (2008), magnetic holes are created in the vicinity of the sun and are convected by the solar wind outward. Periods of Cluster 1 and VEX data when both spacecraft were connected by the solar wind flow have been considered in this study, in order to determine the evolution of the magnetic holes occurrence rate. The comparison of the magnetic holes occurrence near the Venus and the Earth supports the Russell et al. (2008) premise that they are generated closer to the Sun most likely somewhere within the orbit of Mercury.

scholarly journals Multispacecraft observations of the terrestrial bow shock and magnetopause during extreme solar wind disturbances

2012 ◽  
Vol 30 (12) ◽  
pp. 1675-1692 ◽  
Author(s):  
M. Tátrallyay ◽  
G. Erdös ◽  
Z. Németh ◽  
M. I. Verigin ◽  
S. Vennerstrom
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Bow Shock ◽  
Shock Model ◽  
Reasonable Accuracy ◽  
The Earth ◽  
Shock Models ◽  
Solar Wind Flow ◽  
D Model ◽  
Good Agreement

Abstract. Three events are discussed from the declining phase of the last solar cycle when the magnetopause and/or the bow shock were observed unusually close to the Earth due to major interplanetary disturbances. The observed extreme locations of the discontinuities are compared with the predictions of three magnetopause and four bow shock models which describe them in considerably different ways using statistical methods based on observations. A new 2-D magnetopause model is introduced (based on Verigin et al., 2009) which takes into account the pressure of the compressed magnetosheath field raised by the interplanetary magnetic field (IMF) component transverse to the solar wind flow. The observed magnetopause crossings could be predicted with a reasonable accuracy (0.1–0.2 RE) by one of the presented models at least. For geosynchronous magnetopause crossings observed by the GOES satellites, (1) the new model provided the best predictions when the IMF was extremely large having a large negative Bz component, and (2) the predictions of the model of Shue et al. (1998) agreed best with the observations when the solar wind dynamic pressure was extremely large. The magnetopause crossings close to the cusp observed by the Cluster spacecraft were best predicted by the 3-D model of Lin et al. (2010). The applied empirical bow shock models and the 3-D semi-empiric bow shock model combined with magnetohydrodynamic (MHD) solution proved to be insufficient for predicting the observed unusual bow shock locations during large interplanetary disturbances. The results of a global 3-D MHD model were in good agreement with the Cluster observations on 17 January 2005, but they did not predict the bow shock crossings on 31 October 2003.

Unusual location of the geotail magnetopause at lunar distance: ARTEMIS observation

2020 ◽  
Author(s):  
Wensai Shang ◽  
Binbin Tang ◽  
Quanqi Shi ◽  
Anmin Tian ◽  
Xiaoyan Zhou ◽  
...  
Keyword(s):  
Solar Wind ◽  
Velocity Vector ◽  
Solar Wind Velocity ◽  
Full Moon ◽  
Interplanetary Shock ◽  
Time Intervals ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
The Earth ◽  
Solar Wind Flow

<p>The Earth’s magnetopause is highly variable in location and shape, and is modulated by solar wind conditions. On 8 March 2012, the ARTEMIS probes were located near the tail current sheet when an interplanetary shock arrived under northward interplanetary magnetic field (IMF) conditions, and recorded an abrupt tail compression at ~(-60, 0, -5) R<sub>E</sub> in Geocentric Solar Ecliptic (GSE) coordinate in the deep magnetotail. Approximately 10 minutes later, the probes crossed the magnetopause many times within an hour after the oblique interplanetary shock passed by. The solar wind velocity vector downstream from the shock was not directed along the Sun-Earth line, but had a significant Y component. We propose that the compressed tail was pushed aside by the appreciable solar wind flow in the Y direction. Using a virtual spacecraft in a global magnetohydrodynamic (MHD) simulation, we reproduce the sequence of magnetopause crossings in the X-Y plane observed by ARTEMIS probes under oblique shock conditions, demonstrating that the compressed magnetopause is sharply deflected at lunar distances in response to the shock and solar wind V<sub>Y</sub> effects. The results of the two different global MHD simulations show that the shocked magnetotail at lunar distances is mainly controlled by the solar wind direction with a timescale of about a quarter hour, which appears to be consistent with the windsock effect. The results also provide some references for investigating interactions between the solar wind/magnetosheath and lunar nearside surface during full moon time intervals, which should not happen in general.</p>

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