MMS Observations of Plasma Heating Associated With FTE Growth

Akhavan‐Tafti, Mojtaba; Slavin, J. A.; Sun, W.; Le, G.; Gershman, D. J.

doi:10.1029/2019gl084843

Cited by 29 publications

(41 citation statements)

References 94 publications

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“…The ion temperature shows an enhancement inside the FTE for both the parallel and perpendicular components, whereas the electron temperature parallel to the magnetic field exhibits an increase in the core region and decrease in the edges. Akhavan-Tafti et al (2019) show that particles are cooled at the trailing edge due to a relaxing field topology, which is consistent with the observation presented in this work.…”

Section: Fte Structure and Motionsupporting

confidence: 93%

Flux Transfer Event With an Electron‐Scale Substructure Observed by the Magnetospheric Multiscale Mission

et al. 2020

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On 12 November 2015 the Magnetospheric Multiscale (MMS) spacecraft traversed the magnetopause from the magnetosphere to the magnetosheath encountering evidence of magnetic reconnection and a tiny flux transfer event (FTE) on the magnetosheath side of the magnetopause boundary layer. The FTE exhibited a large negative-positive bipolar variation in the normal magnetic field component (B N), an enhanced (negative) north-south component direction (B L), and a variation in the third component B M resembling a "W" shape with negative values close to the edges and positive values near the center. Using the tetrahedron formation, we estimate that the FTE moved southward and duskward with a speed of V FTE = 324 km/s. The FTE size in the transverse direction is 518 km, which corresponds to 4.42 ion gyroradii. We identify an internal layer where the electron bulk flow velocity exhibits different behaviors at each of the four spacecraft and the current density was more intense at two spacecraft. Within the FTE's core region, the ion bulk flow behavior was similar for all four spacecraft. Using the velocity obtained from timing analysis, we estimate a dimension of this core region to be 181.4 km, which corresponds to 1.5 ion gyroradii. It is evident that the internal region is not large enough to affect the ion behavior but can do so for electrons. We conclude that the FTE's core is an electron-scale substructure.

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Section: Fte Structure and Motionsupporting

confidence: 93%

Flux Transfer Event With an Electron‐Scale Substructure Observed by the Magnetospheric Multiscale Mission

et al. 2020

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“…This can be described as an equation for the rate of kinetic energy (W) gain of particles in the guiding center limit where the first adiabatic invariant is conserved (Drake et al, 2019): -Tafti et al, 2019b). Betatron acceleration would normally cause the enhancements of perpendicular pitch angles (i.e.…”

Section: Plasma Acceleration Inside Ftesmentioning

confidence: 99%

Flux Transfer Events at a Reconnection‐Suppressed Magnetopause: Cassini Observations at Saturn

et al. 2021

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“…Signatures of dayside magnetic flux erosion, that is, magnetic reconnection, and tailward flux transport were observed during the SSC phase. In particular, during the encounter with the ICME 2 sheath region, the MMS spacecraft detected reconnected magnetic flux at the magnetopause transported tailward as bundles of “open” magnetic flux tubes with a flux rope‐like geometry, known as flux transfer events (FTEs) (e.g., Akhavan‐Tafti, Slavin, Eastwood, et al, 2019; Akhavan‐Tafti, Slavin, Sun, et al, 2019; Akhavan‐Tafti et al, 2020; Russell & Elphic, 1979). Figure 7a shows the close‐up view of the magnetic signatures inside and surrounding the FTE in the turbulent magnetosheath behind the quasi‐parallel bow shock (e.g., Pollock et al, 2018).…”

Section: Storm‐time Flux Transportmentioning

confidence: 99%

Cross‐Scale Quantification of Storm‐Time Dayside Magnetospheric Magnetic Flux Content

et al. 2020

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A clear understanding of storm-time magnetospheric dynamics is essential for a reliable storm forecasting capability. The dayside magnetospheric response to an interplanetary coronal mass ejection (ICME; dynamic pressure P dyn > 20 nPa and storm-time index SYM-H < −150 nT) is investigated using in situ OMNI, Geotail, Cluster, MMS, GOES, Van Allen Probes, and THEMIS measurements. The dayside magnetic flux content is directly quantified from in situ magnetic field measurements at different radial distances. The arrival of the ICME, consisting of shock and sheath regions preceding a magnetic cloud, initiated a storm sudden commencement (SSC) phase (SYM-H~+50 nT). At SSC, the magnetopause standoff distance was compressed earthward at ICME shock encounter at an average rate~−10.8 Earth radii per hour for~10 min, resulting in a rapid 40% reduction in the magnetospheric volume. The "closed" magnetic flux content remained constant at 170 ± 30 kWb inside the compressed dayside magnetosphere, even in the presence of dayside reconnection, as evident by an outsized flux transfer event containing 160 MWb. During the storm main and recovery phases, the magnetosphere expanded. The dayside magnetic flux did not remain constant within the expanding magnetosphere (110 ± 30 kWb), resulting in a 35% reduction in pre-storm flux content during the magnetic cloud encounter. At that stage, the magnetospheric magnetic flux was eroded resulting in a weakened dayside magnetospheric field strength at radial distances R ≥ 5 R E. It is concluded that the inadequate replenishment of the eroded dayside magnetospheric flux during the magnetosphere expansion phase is due to a time lag in storm-time Dungey cycle. Plain Language Summary A clear understanding of Earth's magnetospheric dynamics is essential for a reliable space weather forecasting capability. To achieve this, we take advantage of the Heliophysics System Observatory's (HSO) multitude of in situ observations in order to, for the first time, quantify the amount of magnetic flux stored in the dayside magnetosphere. The stored magnetic flux shields our ground-based and space-borne assets from adverse space weather events. We examine the dayside magnetic flux content during an encounter with an interplanetary coronal mass ejection (ICME). ICME is a large-scale bundle of magnetic flux and charged particles originating from the Sun. Upon arrival, the ICME which occupied nearly one third of the space between the Sun and Earth forced the dayside magnetosphere to rapidly shrink down to geosynchronous orbit where most communications and weather satellites are located. Though the dayside magnetosphere significantly shrunk, its magnetic flux content remained constant. It was only when the dayside magnetosphere started to expand that the dayside magnetospheric flux content gradually reduced by 35%. It is concluded that, during large ICME encounters, the rate at which dayside magnetic flux is transported to the magnetotail is faster than the rate at which magnetic flux is recycled, via a process kno...

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MMS Observations of Plasma Heating Associated With FTE Growth

Cited by 29 publications

References 94 publications

Flux Transfer Event With an Electron‐Scale Substructure Observed by the Magnetospheric Multiscale Mission

Flux Transfer Event With an Electron‐Scale Substructure Observed by the Magnetospheric Multiscale Mission

Flux Transfer Events at a Reconnection‐Suppressed Magnetopause: Cassini Observations at Saturn

Cross‐Scale Quantification of Storm‐Time Dayside Magnetospheric Magnetic Flux Content

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