Proton transport model in the ionosphere. 2. Influence of magnetic mirroring and collisions on the angular redistribution in a proton beam

Galand, M.; Lilensten, J.; Kofman, W.; Lummerzheim, D.

doi:10.1007/s005850050698

Cited by 14 publications

(43 citation statements)

References 29 publications

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“…Because the computational burden of the Monte-Carlo method is only weakly dependent on the number of processes in the simulation, previous studies have included many interactions present in the upper atmosphere (i.e., Kozelov, 1993;Bisikalo et al, 1995;Synnes et al, 1998;for transport model cf. De Michelis &Orsini, 1997, andGaland et al, 1998). However, since many or most of the cross sections of upper atmosphere interactions are unknown or not well defined, including such reactions may actually increase the uncertainty of the Monte Carlo approach.…”

Section: Limitations In Stochastic and Other Methodsmentioning

confidence: 99%

“…The general consensus is that scattering becomes negligible for energetic particles (>1 keV) and follows the extreme forward scattering approximation (Bazell et al, 2010;Galand et al, 1997Galand et al, , 1998. Unfortunately, the scattering cross sections involved in upper atmospheric interactions are poorly known (Bisikalo et al, 1995;Fang et al, 2004;Galand et al, 1998;Gérard et al, 2000;Kozelov, 1993;Solomon, 2001). The Monte Carlo method requires numerical approximations for all the interactions included in the simulations.…”

Section: Limitations In Stochastic and Other Methodsmentioning

confidence: 99%

“…However, it is reasonable to question whether this approach captures the average energy loss calculated by the stochastic method. Appendix C1 describes a random tau parametric Galand et al (1997Galand et al ( , 1998 Galand and Richmond (1999) Gérard et al…”

Section: Deterministic Instead Of Stochastic Path Intervalsmentioning

confidence: 99%

“…The first simplified field, the spatially uniform and vertical field (Galand et al, 1997(Galand et al, , 1998Synnes et al, 1998, and references therein;Fang et al, 2004), has the property that the ion pitch angle does not change as the ion spirals down the field line, thus excluding ion mirroring. Under this assumption, the properties of precipitating ions do not change with altitude.…”

Section: 1002/2017ja024016mentioning

confidence: 99%

“…Due to the vertical field lines, the contribution of ENAs to ion beam spreading remains symmetrical. Ion precipitation is affected by beam spreading and a Journal of Geophysical Research: Space Physics 10.1002/2017JA024016 Galand et al (1997Galand et al ( , 1998 Galand and Richmond (1999) Gérard et al…”

Section: 1002/2017ja024016mentioning

confidence: 99%

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Low‐Altitude Emission of Energetic Neutral Atoms: Multiple Interactions and Energy Loss

et al. 2017

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Low‐altitude emissions (LAEs) are the energetic neutral atom (ENA) signature of ring current ions precipitating along the magnetic field to an altitude of 200–800 km. This altitude region is considered to be “optically thick” because ring current ions undergo multiple charge changing interactions (MCCIs) with Earth's dense oxygen exosphere. While each interaction involves an energy loss of ~36 eV, no prior study has determined the accumulated energy lost by 1–100 keV H+ emerging as LAEs. We have developed a 2‐D model with a geomagnetic dipole that captures the net effects in energy loss and pitch angle evolution as a result of MCCIs without the computational requirements of a full Monte Carlo simulation. Dependent on the amount of latitudinal migration, the energy loss is greater than 20% for ions below 60 keV for equatorward moving particles (30 keV for poleward). Since the ENA travels ballistically across a geomagnetic dipole, upon reionization, ion velocity along the local field increases (antiparallel in the northern hemisphere). Redirecting the particle upward through MCCIs is most effective during poleward ENA motion. The net effect is to redirect precipitating ions (below 2,500 km) to eventually emerge from the optically thick region either as an ion or ENA. Precipitation is a joint ion‐neutral process, affecting both the energy and pitch angle distribution through the transverse motion of ENA segments in a converging field. For particles that enter the MCCI regime, the energy loss and evolution of the pitch angle distribution must be considered within a realistic magnetic field.

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Section: Limitations In Stochastic and Other Methodsmentioning

confidence: 99%

Section: Limitations In Stochastic and Other Methodsmentioning

confidence: 99%

Section: Deterministic Instead Of Stochastic Path Intervalsmentioning

confidence: 99%

Section: 1002/2017ja024016mentioning

confidence: 99%

Section: 1002/2017ja024016mentioning

confidence: 99%

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Low‐Altitude Emission of Energetic Neutral Atoms: Multiple Interactions and Energy Loss

et al. 2017

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Statistical correlation of low‐altitude ENA emissions with geomagnetic activity from IMAGE/MENA observations

et al. 2016

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Plasma sheet particles transported Earthward during times of active magnetospheric convection can interact with exospheric/thermospheric neutrals through charge exchange. The resulting Energetic Neutral Atoms (ENAs) are free to leave the influence of the magnetosphere and can be remotely detected. ENAs associated with low‐altitude (300–800 km) ion precipitation in the high‐latitude atmosphere/ionosphere are termed low‐altitude emissions (LAEs). Remotely observed LAEs are highly nonisotropic in velocity space such that the pitch angle distribution at the time of charge exchange is near 90°. The Geomagnetic Emission Cone of LAEs can be mapped spatially, showing where proton energy is deposited during times of varying geomagnetic activity. In this study we present a statistical look at the correlation between LAE flux (intensity and location) and geomagnetic activity. The LAE data are from the MENA imager on the IMAGE satellite over the declining phase of solar cycle 23 (2000–2005). The SYM‐H, AE, and Kp indices are used to describe geomagnetic activity. The goal of the study is to evaluate properties of LAEs in ENA images and determine if those images can be used to infer properties of ion precipitation. Results indicate a general positive correlation to LAE flux for all three indices, with the SYM‐H showing the greatest sensitivity. The magnetic local time distribution of LAEs is centered about midnight and spreads with increasing activity. The invariant latitude for all indices has a slightly negative correlation. The combined results indicate LAE behavior similar to that of ion precipitation.

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Analytical estimate for low‐altitude ENA emissivity

et al. 2016

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We formulate the first analytical model for energetic neutral atom (ENA) emissivity that partially corrects for the global viewing geometry dependence of low‐altitude emissions (LAEs) observed by Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS). The emissivity correction requires the pitch angle distribution (PAD) and geophysical location of low‐altitude ENAs. To estimate PAD, we create an energy‐dependent analytical model, based on a Monte Carlo simulation. We account for energy binning by integrating model PAD over each energy bin. We account for finite angular pixels by computing emissivity as an integral over the pitch angle range sampled by the pixel. We investigate location uncertainty in TWINS pixels by performing nine variations of the emissivity calculation. Using TWINS 2 ENA imaging data from 1131 to 1145 UT on 6 April 2010, we derive emissivity‐corrected ion fluxes for two angular pixel sizes: 4° and 1°. To evaluate the method, we compare TWINS‐derived ion fluxes to simultaneous in situ data from the National Oceanic and Atmospheric Administration (NOAA) 17 satellite. The TWINS‐NOAA agreement for emissivity‐corrected flux is improved by up to a factor of 7, compared to uncorrected flux. The highest 1° pixel fluxes are a factor of 2 higher than for 4° pixels, consistent with pixel‐derived fluxes that are artificially low because subpixel structures are smoothed out, and indicating a possible slight advantage to oversampling the instrument‐measured LAE signal. Both TWINS and NOAA ion fluxes decrease westward of 2000 magnetic local time. The TWINS‐NOAA comparison indicates that the global ion precipitation oval comprises multiple smaller‐scale (3–5° of latitude) structures.

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Proton transport model in the ionosphere. 2. Influence of magnetic mirroring and collisions on the angular redistribution in a proton beam

Cited by 14 publications

References 29 publications

Low‐Altitude Emission of Energetic Neutral Atoms: Multiple Interactions and Energy Loss

Low‐Altitude Emission of Energetic Neutral Atoms: Multiple Interactions and Energy Loss

Statistical correlation of low‐altitude ENA emissions with geomagnetic activity from IMAGE/MENA observations

Analytical estimate for low‐altitude ENA emissivity

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