3-D mesoscale MHD simulations of magnetospheric cusp-like configurations: cusp diamagnetic cavities and boundary structure

Adamson, E.; Otto, A.; Nykyri, K.

doi:10.5194/angeo-30-325-2012

Cited by 13 publications

(22 citation statements)

References 51 publications

(82 reference statements)

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“…However the total pressure is still lower than outside of the cavity (i). Reduced magnetic pressure, balanced by the increased thermal pressure is a typical signature of the diamagnetic cusp cavities created by reconnection in MHD (Adamson et al, ). Here the plasma pressure calculation does not include the high‐energy particles, which is why the plasma pressure does not balance the magnetic pressure.…”

Section: Resultsmentioning

confidence: 99%

“…Figure 6 shows the plasma and field properties of the dayside magnetosphere at 09:24 UT from high-resolution MHD global simulation results, with the MMS1 location projected in each plane as well as the cartoon of the expected DMC locations based on the maximum shear of the draped IMF field around the geomagnetic field in the vicinity of the cusps. The DMCs are directly generated by reconnection in maximum magnetic shear regions in a similar manner described by Nykyri, Otto, Adamson, Dougal, and Mumme (2011) and Adamson et al (2011Adamson et al ( , 2012. These cavities are indicated by a strongly enhanced plasma beta (color scale is saturated at beta = 38 in order to better see the northern hemisphere DMC in the same plane) tailward of the MMS at x = 5 R E (panel a) in the expected regions in Southern (region iv in panels b and g) and Northern Hemispheres (region iv in panels c and h).…”

Section: Mms Observationsmentioning

confidence: 94%

“…The DMCs, characterized by extended regions of decreased magnetic field and high plasma beta surrounding the high‐altitude cusp funnel, are mainly formed by magnetic reconnection between the IMF and Earth's magnetic field surrounding the magnetospheric cusps (Adamson et al, , ; Nykyri, Otto, Adamson, Dougal, & Mumme, ; Nykyri, Otto, Adamson, & Tjulin, ; Zhang et al, ). Cusps are a funnel‐like, basic topological features of the magnetosphere, and were first predicted by Chapman and Ferraro () using the image dipole model.…”

Section: Introductionmentioning

confidence: 99%

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First MMS Observation of Energetic Particles Trapped in High‐Latitude Magnetic Field Depressions

Nykyri

Chu

et al. 2019

JGR Space Physics

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We present a case study of the Magnetospheric Multiscale (MMS) observations of the Southern Hemispheric dayside magnetospheric boundaries under southward interplanetary magnetic field direction with strong By component. During this event MMS encountered several magnetic field depressions characterized by enhanced plasma beta and high fluxes of high‐energy electrons and ions at the dusk sector of the southern cusp region that resemble previous Cluster and Polar observations of cusp diamagnetic cavities. Based on the expected maximum magnetic shear model and magnetohydrodynamic simulations, we show that for the present event the diamagnetic cavity‐like structures were formed in an unusual location. Analysis of the composition measurements of ion velocity distribution functions and magnetohydrodynamics simulations show clear evidence of the creation of a new kind of magnetic bottle structures by component reconnection occurring at lower latitudes. We propose that the high‐energy particles trapped in these cavities can sometimes end up in the loss cone and leak out, providing a likely explanation for recent high‐energy particle leakage events observed in the magnetosheath.

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Section: Resultsmentioning

confidence: 99%

Section: Mms Observationsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

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First MMS Observation of Energetic Particles Trapped in High‐Latitude Magnetic Field Depressions

Nykyri

Chu

et al. 2019

JGR Space Physics

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“…However, the differing spacecraft velocities at high altitudes (∼10 R E ) affect the observations; Clusters larger velocity (than Polar) results in a smoothing effect of the observed diamagnetic depression, and therefore, it is only measured during enhanced (>2 nPa) solar wind dynamic pressures [Nykyri et al, 2011b]. Modeling by Adamson et al [2011Adamson et al [ , 2012 showed that the location and size of the cusp diamagnetic depression is strongly dependent on the IMF orientation, and that it is mainly structured by reconnection processes.…”

Section: 1002/2016ja023738mentioning

confidence: 99%

Diamagnetic depression observations at Saturn's magnetospheric cusp by the Cassini spacecraft

et al. 2017

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The magnetospheric cusp is a region where shocked solar wind plasma can enter a planetary magnetosphere, after magnetic reconnection has occurred at the dayside magnetopause or in the lobes. The dense plasma that enters the high‐latitude magnetosphere creates diamagnetic effects whereby a depression is observed in the magnetic field. We present observations of the cusp events at Saturn's magnetosphere where these diamagnetic depressions are found. The data are subtracted from a magnetic field model, and the calculated magnetic pressure deficits are compared to the particle pressures. A high plasma pressure layer in the magnetosphere adjacent to the cusp is discovered to also depress the magnetic field, outside of the cusp. This layer is observed to contain energetic He++ (up to ∼100 keV) from the solar wind as well as heavy water group ions (W+) originating from the moon Enceladus. We also find a modest correlation of diamagnetic depression strength to solar wind dynamic pressure and velocity; however, unlike at Earth, there is no correlation found with He++ counts.

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“…The diamagnetic cavity in the high‐latitude cusp region is also thought to be a possible source of energetic ions in the dayside magnetosphere and near‐Earth plasma sheet [e.g., Chen and Fritz , ; Fritz et al , ; Fritz et al , ]. The diamagnetic cavity is a region with enhanced plasma pressure and decreased magnetic field strengths formed by the magnetic reconnection in the high‐latitude magnetopause [e.g., Nykyri et al , , Adamson et al ., ]. This region is able to trap charged particles.…”

Section: Introductionmentioning

confidence: 99%

IMF dependence of energetic oxygen and hydrogen ion distributions in the near‐Earth magnetosphere

et al. 2017

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Energetic ion distributions in the near‐Earth plasma sheet can provide important information for understanding the entry of ions into the magnetosphere and their transportation, acceleration, and losses in the near‐Earth region. In this study, 11 years of energetic proton and oxygen observations (> ~274 keV) from Cluster/Research with Adaptive Particle Imaging Detectors were used to statistically study the energetic ion distributions in the near‐Earth region. The dawn‐dusk asymmetries of the distributions in three different regions (dayside magnetosphere, near‐Earth nightside plasma sheet, and tail plasma sheet) are examined in Northern and Southern Hemispheres. The results show that the energetic ion distributions are influenced by the dawn‐dusk interplanetary magnetic field (IMF) direction. The enhancement of ion intensity largely correlates with the location of the magnetic reconnection at the magnetopause. The results imply that substorm‐related acceleration processes in the magnetotail are not the only source of energetic ions in the dayside and the near‐Earth magnetosphere. Energetic ions delivered through reconnection at the magnetopause significantly affect the energetic ion population in the magnetosphere. We also believe that the influence of the dawn‐dusk IMF direction should not be neglected in models of the particle population in the magnetosphere.

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3-D mesoscale MHD simulations of magnetospheric cusp-like configurations: cusp diamagnetic cavities and boundary structure

Cited by 13 publications

References 51 publications

First MMS Observation of Energetic Particles Trapped in High‐Latitude Magnetic Field Depressions

First MMS Observation of Energetic Particles Trapped in High‐Latitude Magnetic Field Depressions

Diamagnetic depression observations at Saturn's magnetospheric cusp by the Cassini spacecraft

IMF dependence of energetic oxygen and hydrogen ion distributions in the near‐Earth magnetosphere

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