Magnetic reconnection at Neptune's magnetopause

Masters, A.

doi:10.1002/2014ja020744

Cited by 23 publications

(33 citation statements)

References 57 publications

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“…The calculated potentials are lower than the upper limit at Earth, ~200 kV (Kivelson & Ridley, ), and the reconnection voltages at the outer planets, Uranus and Neptune, which have been estimated to be ~40 and ~35 kV (Masters, , ). These, however, are upper values that might not be observed due to ionospheric saturation effects.…”

Section: Discussionmentioning

confidence: 70%

Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

et al. 2017

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We analyze 94 traversals of Mercury's southern magnetospheric plasma mantle using data from the MESSENGER spacecraft. The mean and median proton number densities in the mantle are 1.5 and 1.3 cm−3, respectively. For sodium number density these values are 0.004 and 0.002 cm−3. Moderately higher densities are observed on the magnetospheric dusk side. The mantle supplies up to 1.5 × 108 cm−2 s−1 and 0.8 × 108 cm−2 s−1 of proton and sodium flux to the plasma sheet, respectively. We estimate the cross‐electric magnetospheric potential from each observation and find a mean of ~19 kV (standard deviation of 16 kV) and a median of ~13 kV. This is an important result as it is lower than previous estimations and shows that Mercury's magnetosphere is at times not as highly driven by the solar wind as previously thought. Our values are comparable to the estimations for the ice giant planets, Uranus and Neptune, but lower than Earth. The estimated potentials do have a very large range of values (1–74 kV), showing that Mercury's magnetosphere is highly dynamic. A correlation of the potential is found to the interplanetary magnetic field (IMF) magnitude, supporting evidence that dayside magnetic reconnection can occur at all shear angles at Mercury. But we also see that Mercury has an Earth‐like magnetospheric response, favoring −BZ IMF orientation. We find evidence that −BX orientations in the IMF favor the southern cusp and southern mantle. This is in agreement with telescopic observations of exospheric emission, but in disagreement with modeling.

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Section: Discussionmentioning

confidence: 70%

Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

et al. 2017

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“…Reconnection at Neptune has been studied before by Desch et al [], Selesnick [], Huddleston et al [], and Masters [], using either models or remote observations. Early studies focus on purely antiparallel reconnection [e.g., Selesnick , ] as the only form of reconnection: now it is well understood that reconnection can still occur for smaller magnetic shear angles [e.g., Paschmann et al , ; Eastwood et al , ].…”

Section: Simulation Resultsmentioning

confidence: 99%

Global MHD simulations of Neptune's magnetosphere

et al. 2016

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A global magnetohydrodynamic (MHD) simulation has been performed in order to investigate the outer boundaries of Neptune's magnetosphere at the time of Voyager 2's flyby in 1989 and to better understand the dynamics of magnetospheres formed by highly inclined planetary dipoles. Using the MHD code Gorgon, we have implemented a precessing dipole to mimic Neptune's tilted magnetic field and rotation axes. By using the solar wind parameters measured by Voyager 2, the simulation is verified by finding good agreement with Voyager 2 magnetometer observations. Overall, there is a large‐scale reconfiguration of magnetic topology and plasma distribution. During the “pole‐on” magnetospheric configuration, there only exists one tail current sheet, contained between a rarefied lobe region which extends outward from the dayside cusp, and a lobe region attached to the nightside cusp. It is found that the tail current always closes to the magnetopause current system, rather than closing in on itself, as suggested by other models. The bow shock position and shape is found to be dependent on Neptune's daily rotation, with maximum standoff being during the pole‐on case. Reconnection is found on the magnetopause but is highly modulated by the interplanetary magnetic field (IMF) and time of day, turning “off” and “on” when the magnetic shear between the IMF and planetary fields is large enough. The simulation shows that the most likely location for reconnection to occur during Voyager 2's flyby was far from the spacecraft trajectory, which may explain the relative lack of associated signatures in the observations.

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“…We use an analytical modeling approach that has recently been applied to Uranus and Neptune [ Masters , , ], which is heavily based on past studies of reconnection at Earth's magnetopause [e.g., Cooling et al , ; Petrinec et al , ]. To avoid reproduction of material, here we give an overview of the approach, describe how the model has been adapted for the case of Saturn, and explain how Cassini observations are used for model calibration.…”

Section: Modeling Conditions At Saturn's Magnetopausementioning

confidence: 99%

The dayside reconnection voltage applied to Saturn's magnetosphere

Masters

2015

Geophysical Research Letters

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The ability of magnetic reconnection between interplanetary and planetary magnetic fields to drive a planetary magnetosphere can be quantified as the resulting voltage applied to the system. We present analytical model predictions of the dayside reconnection voltage at Saturn, a planet where solar wind driving has been the subject of debate. Model‐predicted voltages are in reasonable agreement with adapted terrestrial coupling function estimates, as well as voltages inferred from auroral observations. The voltage is most sensitive to the interplanetary magnetic field (IMF). Combining the model with Cassini IMF observations suggests that the voltage is rarely high enough to compete with internal driving of Saturn's outer magnetosphere. The long‐term average dayside (and nightside) voltage is ~40 kV. We point out that the distribution of IMF strength at Saturn is not bimodal, despite the compression‐rarefaction structure of the local heliosphere when the Cassini observations were made.

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Magnetic reconnection at Neptune's magnetopause

Cited by 23 publications

References 57 publications

Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

Mercury's Solar Wind Interaction as Characterized by Magnetospheric Plasma Mantle Observations With MESSENGER

Global MHD simulations of Neptune's magnetosphere

The dayside reconnection voltage applied to Saturn's magnetosphere

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