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We compare plasma measurements in the solar wind between the Magnetospheric MultiScale Mission's (MMS) Fast Plasma Investigation (FPI) and those obtained near the Earth‐Sun L1 Lagrangian point from OMNI. FPI is an instrument designed to investigate plasma processes such as magnetic reconnection, acceleration, and turbulence. Since 2017, MMS supports solar wind campaigns where the plasma can have a higher Mach number, a cooler temperature, and a narrower beam compared with the MMS primary regions of interest. With FPI's firmware now optimized for these campaigns, the comparison with OMNI aids the interpretation of solar wind measurements. From these comparisons, we can make suggestions for both fast and burst‐survey telemetry modes. From fast mode intervals, we find first, that the FPI ion density can be lower than the OMNI proton density. However, the FPI electron density agrees well with the OMNI proton density. Second, due to the solar wind's cooler proton temperature and narrow‐angle, the FPI ion temperature is overestimated. Thus, using the OMNI proton temperature is suggested for plasma parameters such as the ion β, the ratio of ion thermal to magnetic pressure. Third, the FPI ion velocity is well‐estimated when compared with the OMNI proton velocity. In burst mode, the ion density and temperature have similar characteristics but to a lesser degree. Spin effects observed in all these plasma moments in burst mode intervals are reduced with the methods discussed in this paper. The results are summarized in a table that includes linear fit parameters and their defined errors. Key Points: Plasma measurements in the solar wind from Magnetospheric MultiScale Mission's Fast Plasma Investigation (FPI) are compared with the OMNI solar wind databaseThe electron density and ion velocity show good agreement with OMNI's proton density and velocity respectivelyThe FPI ion density is underestimated and FPI ion temperature is overestimated when compared to OMNI [ABSTRACT FROM AUTHOR]

We present observations of mirror mode structures in the dawn-side magnetosphere from the Magnetospheric Multiscale Mission. The observations were made during a period of relatively stable northward interplanetary magnetic field conditions. We observed magnetic troughs only with reductions of up to 90% in the magnitude of the local magnetic field. The structures were closely aligned with the local magnetic field and had sizes perpendicular to the magnetic field of the order of 1Re and ion densities up to twice that of the surrounding regions. We used ion, magnetic field, and electric field data to examine the plasma conditions inside and outside of these structures to investigate the stability and evolution of the structures and estimate the magnitude of changes in the ion distributions. Comparing the ion bulk properties to theoretical predictions, we concluded that variations in the parameters with trough depth were due to the spacecraft traversing them at different locations along their length. Our calculations of heating and cooling of the ions at different pitch angles is consistent with theory. We conclude that these troughs were likely long-lived, bistable structures that originated in the magnetosheath near the nose of the magnetopause and were captured into the magnetosphere by dual-lobe reconnection. [ABSTRACT FROM AUTHOR]

We present observations of mirror mode structures in the dawn‐side magnetosphere from the Magnetospheric Multiscale Mission. The observations were made during a period of relatively stable northward interplanetary magnetic field conditions. We observed magnetic troughs only with reductions of up to 90% in the magnitude of the local magnetic field. The structures were closely aligned with the local magnetic field and had sizes perpendicular to the magnetic field of the order of 1Re and ion densities up to twice that of the surrounding regions. We used ion, magnetic field, and electric field data to examine the plasma conditions inside and outside of these structures to investigate the stability and evolution of the structures and estimate the magnitude of changes in the ion distributions. Comparing the ion bulk properties to theoretical predictions, we concluded that variations in the parameters with trough depth were due to the spacecraft traversing them at different locations along their length. Our calculations of heating and cooling of the ions at different pitch angles is consistent with theory. We conclude that these troughs were likely long‐lived, bistable structures that originated in the magnetosheath near the nose of the magnetopause and were captured into the magnetosphere by dual‐lobe reconnection.Key Points: Mirror mode trough structures were observed in the dawn‐side magnetosphere within the low‐latitude boundaryIon trapping, as well as heating and cooling, was observed within the structures and may explain the stable nature of the structuresReconnection signatures near the structures suggest they were captured from the magnetosheath by dual‐lobe reconnection [ABSTRACT FROM AUTHOR]

We present a new method for determining the main relevant features of the local magnetic field configuration, based entirely on the knowledge of the magnetic field gradient four‐spacecraft measurements. The method, named "magnetic configuration analysis" (MCA), estimates the spatial scales on which the magnetic field varies locally. While it directly derives from the well‐known magnetic directional derivative and magnetic rotational analysis procedures (Shi et al., 2005, htpps://doi.org/10.1029/2005GL022454; Shen et al., 2007, https://doi.org/10.1029/2005JA011584), MCA was specifically designed to address the actual magnetic field geometry. By applying MCA to multispacecraft data from the Magnetospheric Multiscale (MMS) satellites, we perform both case and statistical analyses of local magnetic field shape and dimensionality at very high cadence and small scales. We apply this technique to different near‐Earth environments and define a classification scheme for the type of configuration observed. While our case studies allow us to benchmark the method with those used in past works, our statistical analysis unveils the typical shape of magnetic configurations and their statistical distributions. We show that small‐scale magnetic configurations are generally elongated, displaying forms of cigar and blade shapes, but occasionally being planar in shape like thin pancakes (mostly inside current sheets). Magnetic configurations, however, rarely show isotropy in their magnetic variance. The planar nature of magnetic configurations and, most importantly, their scale lengths strongly depend on the plasma β parameter. Finally, the most invariant direction is statistically aligned with the electric current, reminiscent of the importance of electromagnetic forces in shaping the local magnetic configuration. Key Points: We define and use a four‐spacecraft method on MMS data to study the magnetic field configuration at small scales in near Earth regionsCase studies demonstrate the ability of the method to measure local magnetic configuration, benchmarking the method on previous studiesStatistically, low plasma betas are correlated with large length scales and slightly more frequent planar shapes in magnetic configurations [ABSTRACT FROM AUTHOR]