Shift of the magnetopause reconnection line to the winter hemisphere under southward IMF conditions: Geotail and MMS observations

Kitamura, Naritoshi; Hasegawa, Hiroshi; Saito, Y.; Shinohara, I.; Yokota, Shoichiro; Nagai, T.; Pollock, C. J.; Giles, B. L.; Moore, T. E.; Dorelli, J.; Gershman, D. J.; Avanov, L. A.; Paterson, W. R.; Coffey, V. N.; Chandler, M. O.; Sauvaud, J. A.; Lavraud, B.; Torbert, R. B.; Russell, C. T.; Strangeway, R. J.; Burch, J. L.

doi:10.1002/2016gl069095

Cited by 18 publications

(30 citation statements)

References 39 publications

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“…We note that, in principle, L can be estimated as [ Nakamura et al , ],

L = \frac{(T_{2} - T_{1}) V_{MP}}{V_{in}} \cdot \frac{V_{c1} V_{c2}}{V_{c2} - V_{c1}},

for the electron velocity cutoff, as well as the VFE acting on magnetospheric ions in the magnetosheath boundary layer (MSBL) [ Nakamura et al , , ] and magnetosheath ions in the LLBL [ Kitamura et al , ]. However, as V c1 and V c2 become much larger than the ion velocities, L becomes sensitive to variations in the magnetopause boundary speed V MP and inflow speed V in .…”

Section: Discussionmentioning

confidence: 99%

“…In Figure c, ions accelerated and heated by the reconnection are seen in association with an enhancement of ion velocity in the L direction. The increase in the low‐energy cutoff from 14:59:30 to 15:01:15 UT in the ion energy spectrum is due to the velocity filter effect (VFE) [ Nakamura et al , ] applying to ions originating from the magnetosheath in the Lower Latitude Boundary Layer (LLBL) [e.g., Kitamura et al , ]. Cold ions were also detected between 14:59:55 and 15:01:15 UT, as they were accelerated by the reconnection into the energy range detected by ESA [ McFadden et al , ].…”

Section: The 22 November 2011 Eventmentioning

confidence: 99%

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Waves in the innermost open boundary layer formed by dayside magnetopause reconnection

et al. 2017

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We present two Time History of Events and Macroscale Interactions during Substorms observations of whistler mode and electrostatic wave events in the innermost open boundary layer (IOBL), formed by dayside magnetopause reconnection. The IOBL is identified by high‐speed electrons from the magnetosheath on the magnetospheric side of the ion outflow from the reconnection site. Quasi‐parallel whistler mode waves propagating toward the reconnection region are observed, along with a partial shortage of magnetospheric electrons moving away from the reconnection region. Calculation of wave linear growth rates shows that the waves can be excited by the perpendicular electron temperature anisotropy that develops due to the partial shortage of field‐aligned magnetospheric electrons. Electrostatic waves close to the lower hybrid resonance frequency are observed in the IOBL in the second event, which occurred during the main phase of a magnetospheric storm. Magnetospheric electrons are almost completely lost in the event, except at pitch angles close to 90°, yet whistler mode waves are not observed. An electron beam from the magnetosheath and counterstreaming cold electrons originating from the plasmaspheric plume are observed in association with the electrostatic waves. Growth rate calculations show that the waves are likely to be ion acoustic waves excited via couplings between the flowing cold electrons and background cold ions. We suggest that differences in solar wind conditions and magnetic reconnection characteristics may control the shapes of the electron velocity distribution functions and the resulting plasma wave properties in the IOBL.

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“…We note that, in principle, L can be estimated as [ Nakamura et al , ],

L = \frac{(T_{2} - T_{1}) V_{MP}}{V_{in}} \cdot \frac{V_{c1} V_{c2}}{V_{c2} - V_{c1}},

Section: Discussionmentioning

confidence: 99%

Section: The 22 November 2011 Eventmentioning

confidence: 99%

Waves in the innermost open boundary layer formed by dayside magnetopause reconnection

et al. 2017

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“…When the dipole tilt angle is positive, the North Pole tilts toward the Sun, so the northern hemisphere is summer and the southern hemisphere is winter. The X-line location under finite dipole tilt was investigated in some modeling studies (e.g., Komar et al, 2015;Park et al, 2006;Russell et al, 2003) and observational studies (e.g., Kitamura et al, 2016;Trattner et al, 2012;Trenchi et al, 2008;Zhu et al, 2015), which suggested that the X-line shifts toward the winter hemisphere. Trenchi et al (2008) conducted a statistical analysis of the X-line location, based on 13 months of Double Star TC 1 observations on the dayside low-latitude magnetopause.…”

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confidence: 99%

Seasonal and Solar Wind Control of the Reconnection Line Location on the Earth's Dayside Magnetopause

et al. 2018

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We investigate the average location of magnetic reconnection on the Earth's dayside magnetopause, based on spatial distributions of northward and southward reconnection jets observed by the THEMIS spacecraft at the near‐noon (10–14 magnetic local time) magnetopause. A total of 711 reconnection jets were identified by applying the Walén relation, the tangential stress balance relation to be satisfied for a reconnected (rotational discontinuity) magnetopause, to magnetopause crossings identified from 10 years of THEMIS observations. The directions and positions of jets indicate that during southward interplanetary magnetic field (IMF) conditions, the dayside X‐line location shifts from the subsolar point toward the winter hemisphere by about 6 Earth radii under the largest tilt of the geomagnetic dipole axis. The X‐line location also shifts northward (southward) by at most 2.5 Earth radii when the IMF is predominantly radial and its x component is positive (negative). The dipole tilt effect on the shift of the X‐line location becomes smaller for higher solar wind Alfvén Mach numbers. The dipole tilt effect being larger than the IMF Bx effect suggests that the X‐line location has a seasonal dependence. Since models and theory show that the reconnection rate away from the subsolar magnetopause is lower than that at the subsolar magnetopause, the dipole tilt dependence of the X‐line location suggests that the efficiency of solar wind energy transfer into the magnetosphere may decrease under larger dipole tilt; this may partially account for seasonal variations of geomagnetic activity, which is known to decrease under larger dipole tilts.

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“…The fact that the return beam form the ionosphere actually disappeared makes a much closer final distance to the component reconnection X‐line more likely. In another study for the GEM kinetic challenge effort, analyzing the same event, Kitamura et al (2016) estimated the distance to the extended X‐line crossing the dayside magnetopause to be about 2 R E based on MMS and Geotail observations. Given the uncertainties in calculating the distance of the reconnection site from the low‐velocity cutoff method, the estimated distances are not inconsistent with the estimation from Kitamura et al (2016), and both results agree with the location of the X‐line being northward of MMS.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…This study is a contribution to the “Geospace Environment Modelling (GEM) dayside kinetic challenge.” This challenge brings together various satellite observations, simulations, and models to study and compare their results for a single, preselected magnetopause crossing event. For this challenge, an interval was selected with steady solar wind and southward IMF conditions that occurred during an MMS magnetopause crossing on 18 November 2015, previously analyzed in Kitamura et al (2016). The study presented here focuses primarily on the observations from the MMS Hot Plasma Composition Analyzer (HPCA) instruments and uses observations from other instruments on MMS and from solar wind monitors for context.…”

Section: Introductionmentioning

confidence: 99%

The 18 November 2015 Magnetopause Crossing: The GEM Dayside Kinetic Challenge Event Observed by MMS/HPCA

et al. 2020

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At Earth's dayside magnetopause, the fundamental process known as magnetic reconnection is responsible for connecting geomagnetic field lines to interplanetary magnetic field lines and converting magnetic energy into particle energy and heat. As part of a coordinated analysis effort by the Geospace Environment Modeling (GEM) community to determine the reconnection location and other aspects of reconnection, a magnetopause crossing by the Magnetospheric Multiscale (MMS) mission on 18 November 2015 was selected. The crossing occurred during stable solar wind and dominantly southward interplanetary magnetic field conditions. The MMS satellites were located close to the subsolar region and observed southward accelerated ion jets during encounters with the magnetopause boundary layers, indicating the presence of an active X‐line north of the satellites. Using proton distributions from the Hot Plasma Composition Analyzer (HPCA) instruments, the distance from the spacecraft to the reconnection site was initially determined to be between 5 to 7 RE. A slight rotation of the interplanetary magnetic field caused a change of the magnetic topology at the magnetopause. This topology change produced conditions which are known to change the location of the X‐line. After the change, the location of the component reconnection line was estimated to be less than 4 RE, but most likely was much closer to the observing satellites.

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Shift of the magnetopause reconnection line to the winter hemisphere under southward IMF conditions: Geotail and MMS observations

Cited by 18 publications

References 39 publications

Waves in the innermost open boundary layer formed by dayside magnetopause reconnection

Waves in the innermost open boundary layer formed by dayside magnetopause reconnection

Seasonal and Solar Wind Control of the Reconnection Line Location on the Earth's Dayside Magnetopause

The 18 November 2015 Magnetopause Crossing: The GEM Dayside Kinetic Challenge Event Observed by MMS/HPCA

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