Secondary Magnetic Reconnection at Earth’s Flank Magnetopause

We report local secondary magnetic reconnection at Earth’s flank magnetopause by using the Magnetospheric Multiscale observations. This reconnection is found at the magnetopause boundary with a large magnetic shear between closed magnetospheric field lines and the open field lines generated by the primary magnetopause reconnection at large scales. Evidence of this secondary reconnection are presented, which include a secondary ion jet and the encounter of the electron diffusion region. Thus the observed secondary reconnection indicates a cross-scale process from a global scale to an electron scale. As the aurora brightening is also observed at the morning ionosphere, the present secondary reconnection suggests a new pathway for the entry of the solar wind into geospace, providing an important modification to the classic Dungey cycle.

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Magnetic Curvature Analysis on Reconnection Related Structures at Earth’s Magnetopause

10.5194/egusphere-egu2020-3764 ◽

2020 ◽

Author(s):

Yi Qi ◽

Christopher T. Russell ◽

Robert J. Strangeway ◽

Yingdong Jia ◽

Roy B. Torbert ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Reconnection ◽

Solar Wind Plasma ◽

Radius Of Curvature ◽

Plasma Properties ◽

Magnetospheric Multiscale ◽

Reconnection Site ◽

Field Lines ◽

The Magnetic Field

<p>Magnetic reconnection is a mechanism that allows rapid and explosive energy transfer from the magnetic field to the plasma. The magnetopause is the interface between the shocked solar wind plasma and Earth&#8217;s magnetosphere. Reconnection enables the transport of momentum from the solar wind into Earth&#8217;s magnetosphere. Because of its importance in this regard, magnetic reconnection has been extensively studied in the past and is the primary goal of the ongoing Magnetospheric Multiscale (MMS) mission. During magnetic reconnection, the originally anti-parallel fields annihilate and reconnect in a thinned current sheet. In the vicinity of a reconnection site, a prominently increased curvature of the magnetic field (and smaller radius of curvature) marks the region where the particles start to deviate from their regular gyro-motion and become available for energy conversion. Before MMS, there were no closely separated multi-spacecraft missions capable of resolving these micro-scale curvature features, nor examining particle dynamics with sufficiently fast cadence.</p><p>In this study, we use measurements from the four MMS spacecraft to determine the curvature of the field lines and the plasma properties near the reconnection site. We use this method to study FTEs (flux ropes) on the magnetopause, and the interaction between co-existing FTEs. Our study not only improves our understanding of magnetic reconnection, but also resolves the relationship between FTEs and structures on the magnetopause.</p>

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Electron-only Reconnection in an Ion-scale Current Sheet at the Magnetopause

The Astrophysical Journal ◽

10.3847/1538-4357/ac2668 ◽

2021 ◽

Vol 922 (1) ◽

pp. 54

Author(s):

S. Y. Huang ◽

Q. Y. Xiong ◽

L. F. Song ◽

J. Nan ◽

Z. G. Yuan ◽

...

Keyword(s):

Magnetic Field ◽

Standard Model ◽

Magnetic Reconnection ◽

Current Sheet ◽

Diffusion Region ◽

Ion Outflow ◽

Magnetospheric Multiscale ◽

The Standard Model ◽

Field Lines ◽

Reconnection Model

Abstract In the standard model of magnetic reconnection, both ions and electrons couple to the newly reconnected magnetic field lines and are ejected away from the reconnection diffusion region in the form of bidirectional burst ion/electron jets. Recent observations propose a new model: electron-only magnetic reconnection without ion coupling in an electron-scale current sheet. Based on the data from the Magnetospheric Multiscale (MMS) mission, we observe a long-extension inner electron diffusion region (EDR) at least 40 d i away from the X-line at the Earth’s magnetopause, implying that the extension of EDR is much longer than the prediction of the theory and simulations. This inner EDR is embedded in an ion-scale current sheet (the width of ∼4 d i, d i is ion inertial length). However, such ongoing magnetic reconnection was not accompanied with burst ion outflow, implying the presence of electron-only reconnection in an ion-scale current sheet. Our observations present a new challenge for understanding the model of standard magnetic reconnection and the electron-only reconnection model in an electron-scale current sheet.

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The Location of Magnetic Reconnection at Earth’s Magnetopause

Space Science Reviews ◽

10.1007/s11214-021-00817-8 ◽

2021 ◽

Vol 217 (3) ◽

Author(s):

K. J. Trattner ◽

S. M. Petrinec ◽

S. A. Fuselier

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Reconnection ◽

Ion Beams ◽

Review Article ◽

Observational Evidence ◽

Magnetic Shear ◽

General Direction ◽

Shear Model ◽

Wide Range

AbstractOne of the major questions about magnetic reconnection is how specific solar wind and interplanetary magnetic field conditions influence where reconnection occurs at the Earth’s magnetopause. There are two reconnection scenarios discussed in the literature: a) anti-parallel reconnection and b) component reconnection. Early spacecraft observations were limited to the detection of accelerated ion beams in the magnetopause boundary layer to determine the general direction of the reconnection X-line location with respect to the spacecraft. An improved view of the reconnection location at the magnetopause evolved from ionospheric emissions observed by polar-orbiting imagers. These observations and the observations of accelerated ion beams revealed that both scenarios occur at the magnetopause. Improved methodology using the time-of-flight effect of precipitating ions in the cusp regions and the cutoff velocity of the precipitating and mirroring ion populations was used to pinpoint magnetopause reconnection locations for a wide range of solar wind conditions. The results from these methodologies have been used to construct an empirical reconnection X-line model known as the Maximum Magnetic Shear model. Since this model’s inception, several tests have confirmed its validity and have resulted in modifications to the model for certain solar wind conditions. This review article summarizes the observational evidence for the location of magnetic reconnection at the Earth’s magnetopause, emphasizing the properties and efficacy of the Maximum Magnetic Shear Model.

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Magnetic reconnection at the heliospheric current sheet and the formation of closed magnetic field lines in the solar wind

Geophysical Research Letters ◽

10.1029/2006gl027188 ◽

2006 ◽

Vol 33 (17) ◽

Cited By ~ 36

Author(s):

J.T. Gosling ◽

D.J. McComas ◽

R.M. Skoug ◽

C.W. Smith

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Magnetic Reconnection ◽

Current Sheet ◽

Heliospheric Current Sheet ◽

Field Lines

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The cusp: a window for particle exchange between the radiation belt and the solar wind

Annales Geophysicae ◽

10.5194/angeo-24-3131-2006 ◽

2006 ◽

Vol 24 (11) ◽

pp. 3131-3137 ◽

Cited By ~ 4

Author(s):

X.-Z. Zhou ◽

T. A. Fritz ◽

Q.-G. Zong ◽

Z. Y. Pu ◽

Y.-Q. Hao ◽

...

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Open Field ◽

Test Particle ◽

Radiation Belt ◽

Magnetospheric Convection ◽

Cusp Region ◽

Particle Simulations ◽

Particle Exchange ◽

Field Lines

Abstract. The study focuses on a single particle dynamics in the cusp region. The topology of the cusp region in terms of magnetic field iso-B contours has been studied using the Tsyganenko 96 model (T96) as an example, to show the importance of an off-equatorial minimum on particle trapping. We carry out test particle simulations to demonstrate the bounce and drift motion. The "cusp trapping limit" concept is introduced to reflect the particle motion in the high latitude magnetospheric region. The spatial distribution of the "cusp trapping limit" shows that only those particles with near 90° pitch-angles can be trapped and drift around the cusp. Those with smaller pitch angles may be partly trapped in the iso-B contours, however, they will eventually escape along one of the magnetic field lines. There exist both open field lines and closed ones within the same drift orbit, indicating two possible destinations of these particles: those particles being lost along open field lines will be connected to the surface of the magnetopause and the solar wind, while those along closed ones will enter the equatorial radiation belt. Thus, it is believed that the cusp region can provide a window for particle exchange between these two regions. Some of the factors, such as dipole tilt angle, magnetospheric convection, IMF and the Birkeland current system, may influence the cusp's trapping capability and therefore affect the particle exchanging mechanism. Their roles are examined by both the analysis of cusp magnetic topology and test particle simulations.

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Dynamical critical scaling of electric field fluctuations in the greater cusp and magnetotail implied by HF radar observations of F-region Doppler velocity

Annales Geophysicae ◽

10.5194/angeo-24-689-2006 ◽

2006 ◽

Vol 24 (2) ◽

pp. 689-705 ◽

Cited By ~ 17

Author(s):

M. L. Parkinson

Keyword(s):

Solar Wind ◽

Open Field ◽

Electric Fields ◽

Spectral Width ◽

Hf Radar ◽

Doppler Velocity ◽

Closed Field ◽

Scaling Exponent ◽

Central Plasma ◽

Field Lines

Abstract. Akasofu's solar wind ε parameter describes the coupling of solar wind energy to the magnetosphere and ionosphere. Analysis of fluctuations in ε using model independent scaling techniques including the peaks of probability density functions (PDFs) and generalised structure function (GSF) analysis show the fluctuations were self-affine (mono-fractal, single exponent scaling) over 9 octaves of time scale from ~46 s to ~9.1 h. However, the peak scaling exponent α0 was a function of the fluctuation bin size, so caution is required when comparing the exponents for different data sets sampled in different ways. The same generic scaling techniques revealed the organisation and functional form of concurrent fluctuations in azimuthal magnetospheric electric fields implied by SuperDARN HF radar measurements of line-of-sight Doppler velocity, vLOS, made in the high-latitude austral ionosphere. The PDFs of vLOS fluctuation were calculated for time scales between 1 min and 256 min, and were sorted into noon sector results obtained with the Halley radar, and midnight sector results obtained with the TIGER radar. The PDFs were further sorted according to the orientation of the interplanetary magnetic field, as well as ionospheric regions of high and low Doppler spectral width. High spectral widths tend to occur at higher latitude, mostly on open field lines but also on closed field lines just equatorward of the open-closed boundary, whereas low spectral widths are concentrated on closed field lines deeper inside the magnetosphere. The vLOS fluctuations were most self-affine (i.e. like the solar wind ε parameter) on the high spectral width field lines in the noon sector ionosphere (i.e. the greater cusp), but suggested multi-fractal behaviour on closed field lines in the midnight sector (i.e. the central plasma sheet). Long tails in the PDFs imply that "microbursts" in ionospheric convection occur far more frequently, especially on open field lines, than can be captured using the effective Nyquist frequency and volume resolution of SuperDARN radars.

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THE DEPENDENCE OF MAGNETIC RECONNECTION ON PLASMA β AND MAGNETIC SHEAR: EVIDENCE FROM SOLAR WIND OBSERVATIONS

The Astrophysical Journal ◽

10.1088/2041-8205/719/2/l199 ◽

2010 ◽

Vol 719 (2) ◽

pp. L199-L203 ◽

Cited By ~ 91

Author(s):

T. D. Phan ◽

J. T. Gosling ◽

G. Paschmann ◽

C. Pasma ◽

J. F. Drake ◽

...

Keyword(s):

Solar Wind ◽

Magnetic Reconnection ◽

Magnetic Shear

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COUNTERSTREAMING SOLAR WIND HALO ELECTRON EVENTS ON OPEN FIELD LINES?

Solar Wind Seven ◽

10.1016/b978-0-08-042049-3.50129-0 ◽

1992 ◽

pp. 619-622 ◽

Cited By ~ 11

Author(s):

J.T. Gosling ◽

D.J. McComas ◽

J.L. Phillips

Keyword(s):

Solar Wind ◽

Open Field ◽

Field Lines

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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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