Evaluating Single Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 2. Magnetic Flux Rope Signature Selection Effects

Smith, A. W.; Jackman, C. M.; Frohmaier, C.; Fear, R. C.; Slavin, J. A.; Coxon, J. C.

doi:10.1029/2018ja025959

Cited by 9 publications

(16 citation statements)

References 53 publications

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“…For our simulations the vertical extent of the electric field region is from z 1 ¼ 4.1 km (just above HAWC) to z 2 ¼ 8 km. While we did not observe the thunderstorm structure for these events, recent observations at HAWC using the broadband RF interferometric mapping and polarization (BIMAP) instrument [40] have located cloud-to-ground lightning initiation at 8 km altitude, or ≈4 km above HAWC.…”

Section: Mos Modelcontrasting

confidence: 91%

“…(1) impulsive rate spikes, or "noise bursts," with durations of a few ms, coincident with and proportional in both duration and intensity to the RF power generated by nearby lightning discharges as characterized by the co-located BIMAP instrument [40], (2) fast rise and exponential-like cecay (FRED) events, consisting of certain PMT rates jumping to very high rates (near or at the saturation rate) within 100 ms, and then decaying over variable time scales from minutes to hours.…”

Section: Hawc Datamentioning

confidence: 99%

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Combining Cherenkov and scintillation detector observations with simulations to deduce the nature of high-energy radiation excesses during thunderstorms

et al. 2019

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We present co-observations of three strong count-rate enhancements associated with thunderstorms observed over 17 April 2015 to 23 September 2015 by the High Altitude Water Cherenkov (HAWC) array, and a suite of small scintillation detectors comprising the Gamma-ray Observations During Overhead Thunderstorms (GODOT) instrument. Because the HAWC array is most sensitive to ionizing radiation at high energies (> 100 MeV), and the small scintillation detectors are most sensitive to ionizing radiation at low energies (3-20 MeV), we investigate using the ratio of these detector counting rates variations to infer spectral characteristics of these enhancements, and understand the physics behind these thunderstorm accelerator mechanisms. We consider two extreme mechanisms that can produce these enhancements: a point source of relativistic runaway electron avalanches (RREA), and modification of the background cosmic-ray spectrum (MOS) from an electric field profile that is everywhere below the RREA threshold. We simulate the responses of HAWC and the GODOT 12.7 cm × ⊘12.7 cm NaI(Tl) scintillator and show that their ratio can discern between the two models, and that the observed thunderstorm rate enhancements are incompatible with the spectra from a point source of RREA, but consistent with our model of MOS for thunderstorm potentials within the range of −250 to 250 MV.

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Section: Mos Modelcontrasting

confidence: 91%

Section: Hawc Datamentioning

confidence: 99%

Combining Cherenkov and scintillation detector observations with simulations to deduce the nature of high-energy radiation excesses during thunderstorms

et al. 2019

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“…As a first approximation, the neutral line is considered to generate a single flux rope moving planetward and a single flux rope moving tailward, with azimuthal widths provided by the extent of the neutral line. If the neutral line and spacecraft are spatially coincident (along the Y MSM axis) then the neutral line is considered to be “detected.” Selection effects, that is, those that would cause the flux rope to not be identified even when encountering the spacecraft, are considered in a companion paper (Smith, Jackman, Frohmaier, et al, ). With this setup the number of flux ropes generated either side of the stationary neutral line is equal, supported by the approximately equal numbers of planetward and tailward moving flux ropes observed by recent surveys (DiBraccio et al, ; Smith et al, ).…”

Section: The Modelmentioning

confidence: 99%

“…The Monte Carlo technique presented in this study has been developed with reference to Mercury's magnetotail but would be applicable to other planetary environments (e.g., other magnetotails or even perhaps magnetopauses) with some adaptation. The inherent biases that are created by placing selection criteria on the required magnetic field signatures are investigated in a companion paper (Smith, Jackman, Frohmaier, et al, ).…”

Section: Introductionmentioning

confidence: 99%

Evaluating Single‐Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 1. Spatial Distributions of the Neutral Line

et al. 2018

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A simple Monte Carlo model is presented that considers the effects of spacecraft orbital sampling on the inferred distribution of magnetic flux ropes, generated through magnetic reconnection in the magnetotail current sheet. When generalized, the model allows the determination of the number of orbits required to constrain the underlying population of structures: It is able to quantify this as a function of the physical parameters of the structures (e.g., azimuthal extent and probability of generation). The model is shown adapted to the Hermean magnetotail, where the outputs are compared to the results of a recent survey. This comparison suggests that the center of Mercury's neutral line is located dawnward of midnight by 0 3 and that the flux ropes are most likely to be wide azimuthally (∼50% of the width of the Hermean tail). The downtail location of the neutral line is not self‐consistent or in agreement with previous (independent) studies unless dissipation terms are included planetward of the reconnection site; potential physical explanations are discussed. In the future the model could be adapted to other environments, for example, the dayside magnetopause or other planetary magnetotails.

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“…The magnetic flux loading‐unloading process in Mercury's magnetosphere, that is, the magnetospheric substorm, has a time scale of only 2 to 3 min (Imber & Slavin, 2017; Slavin et al, 2010; Sun et al, 2015), which is caused by the low solar wind Alfvén Mach number (Slavin & Holzer, 1979; Scurry et al, 1994) and the small magnetosphere (Siscoe et al, 1975). The low solar wind Alfvén Mach number also produces many magnetic reconnection‐generated structures in the magnetosphere, including flux transfer events near the magnetopause (Russell & Walker, 1985; Slavin et al, 2009), flux ropes (DiBraccio, Slavin, Imber, et al, 2015; Slavin et al, 2012; Sun et al, 2016; Smith et al, 2018; Zhao et al, 2019), and dipolarization fronts in the magnetotail plasma sheet (Sundberg et al, 2012; Sun et al, 2016, 2018). These magnetic structures at Mercury resemble those at Earth, but they contain strong kinetic features.…”

Section: Introductionmentioning

confidence: 99%

Proton Properties in Mercury's Magnetotail: A Statistical Study

Zhao

Zong

Slavin

et al. 2020

Geophysical Research Letters

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This study investigates the properties of protons in the magnetotail plasma sheet of Mercury. By superposing 5-year measurements from the MESSENGER spacecraft, we obtain the average energy spectrum of protons in the plasma sheet, which can be fitted nicely by the Gaussian-Kappa model. The proton density, pressure, and energy spectral index are found to be higher on the dawnside than on the duskside. The proton temperature shows a clearly outward radial gradient. The field-aligned density profile indicates that the protons in the outer plasma sheet move adiabatically. The pitch angle distribution reveals the reflected fluxes to be always less than the incident fluxes and indicates the loss of protons due to their impact on the planetary surface. Plain Language Summary Mercury has a miniature magnetosphere subject to intense solar wind forcing. This magnetosphere, among the smallest in the solar system, resembles the Earth's in many key respects. It is also an analog for other small and outside-driven magnetospheres, such as Ganymede's inside Jupiter's magnetosphere. Mercury does not have a significant atmosphere but a tenuous exosphere. Therefore, Mercury's magnetospheric ions are thought to come predominately from the solar wind, and only about 10% of the ions are of planetary origin. This study presents a statistical picture of the protons in Mercury's magnetotail plasma sheet measured by the Fast Imaging Plasma Spectrometer (FIPS) onboard MESSENGER spacecraft. Many parameters are obtained through a best fit procedure with a Gaussian-Kappa distribution. The proton number density, proton pressure, and spectral index show clear dawn-dusk asymmetric features. The results also suggest that the motion of the protons is adiabatic in the outer plasma sheet and non-adiabatic in the central plasma sheet. Furthermore, the loss feature of the protons is also revealed by their asymmetric pitch angle distributions.

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Evaluating Single Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 2. Magnetic Flux Rope Signature Selection Effects

Cited by 9 publications

References 53 publications

Combining Cherenkov and scintillation detector observations with simulations to deduce the nature of high-energy radiation excesses during thunderstorms

Combining Cherenkov and scintillation detector observations with simulations to deduce the nature of high-energy radiation excesses during thunderstorms

Evaluating Single‐Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 1. Spatial Distributions of the Neutral Line

Proton Properties in Mercury's Magnetotail: A Statistical Study

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