Characterization of the energy‐dependent response of riometer absorption

Kellerman, Adam; Shprits, Y. Y.; Makarevich, R. A.; Spanswick, E.; Donovan, E.; Reeves, G. D.

doi:10.1002/2014ja020027

Cited by 16 publications

(24 citation statements)

References 77 publications

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“…It is therefore possible that the lower energies being precipitated from the injection are contributing to 10.1029/2018JA025588 Journal of Geophysical Research: Space Physics the diffuse aurora, which may also explain the correlation between the two signatures. We point out, however, that although Kellerman et al (2015) showed 10-keV electrons may affect riometer signals, the 40-to 60-keV population was much more likely to affect the riometer signature. In either case, the fluctuations we see at RANK may indeed be due to particle precipitation caused by the narrow, earthward-traveling DFBs embedded in bursty bulk flows that we observe as an equatorwardmoving streamer in the RANK ASI.…”

Section: Riometer Absorption With Asi Countsmentioning

confidence: 67%

“…In fact, Sivadas et al (2017) showed that 10to 100-keV fluxes are enhanced over discrete aurora. That said, Kellerman et al (2015) showed that energies as low as 10 keV can affect riometer absorption, so we cannot rule out the possibility of overlapping populations. It is therefore possible that the lower energies being precipitated from the injection are contributing to 10.1029/2018JA025588 Journal of Geophysical Research: Space Physics the diffuse aurora, which may also explain the correlation between the two signatures.…”

Section: Riometer Absorption With Asi Countsmentioning

confidence: 96%

“…Precipitating energetic electrons (~≥30 keV) can reach the D region of the atmosphere where collision frequencies are high enough to affect ionization rates and attenuate high‐frequency radio waves as they pass through the ionosphere. Previous studies have shown that if flux conditions for strong pitch angle scattering are met, meaning, that the Kennel‐Petschek limit is exceeded (Kennel & Petschek, ), integrated electron flux >30 keV is correlated with riometer absorption observed at the spacecraft's magnetic foot point (Baker et al, ; Beharrell et al, ; Clilverd et al, ; Kellerman et al, ; Spanswick et al, ). Spanswick et al () determined that if the riometer absorption ramps up and peaks within 3 min, the signature is correlated with a dispersionless injection in space.…”

Section: Observationsmentioning

confidence: 99%

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Utilizing the Heliophysics/Geospace System Observatory to Understand Particle Injections: Their Scale Sizes and Propagation Directions

et al. 2019

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The injection region's formation, scale size, and propagation direction have been debated throughout the years, with new questions arising with increased plasma sheet observations by missions like Cluster and THEMIS. How do temporally and spatially small‐scale injections relate to the larger injections historically observed at geosynchronous orbit? How to account for opposing propagation directions—earthward, tailward, and azimuthal—observed by different studies? To address these questions, we used a combination of multisatellite and ground‐based observations to knit together a cohesive story explaining injection formation, propagation, and differing spatial scales and timescales. We used a case study to put statistics into context. First, fast earthward flows with embedded small‐scale dipolarizing flux bundles transport both magnetic flux and energetic particles earthward, resulting in minutes‐long injection signatures. Next, a large‐scale injection propagates azimuthally and poleward/tailward, observed in situ as enhanced flux and on the ground in the riometer signal. The large‐scale dipolarization propagates in a similar direction and speed as the large‐scale electron injection. We suggest small‐scale injections result from earthward‐propagating, small‐scale dipolarizing flux bundles, which rapidly contribute to the large‐scale dipolarization. We suggest the large‐scale dipolarization is the source of the large‐scale electron injection region, such that as dipolarization expands, so does the injection. The >90‐keV ion flux increased and decreased with the plasma flow, which died at the satellites as global dipolarization engulfed them. We suggest the ion injection region at these energies in the plasma sheet is better organized by the plasma flow.

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Section: Riometer Absorption With Asi Countsmentioning

confidence: 67%

Section: Riometer Absorption With Asi Countsmentioning

confidence: 96%

Section: Observationsmentioning

confidence: 99%

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Utilizing the Heliophysics/Geospace System Observatory to Understand Particle Injections: Their Scale Sizes and Propagation Directions

et al. 2019

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“…It has been long recognized that energetic particles at geosynchronous Earth orbit (GEO) are modulated by solar wind forcing (e.g., Paulikas and Blake 1979;Baker et al 1979Baker et al , 1986Baker et al , 1990Blake et al 1997;Reeves 1998;Mathie and Mann 2001;O'Brien et al 2001;Li, 2001Li, , 2004Li et al 2005Li et al , 2011Lyatsky andKhazanov 2008a, 2008b;Borovsky and Denton 2009;Boynton et al 2013;Simms et al 2016;Kellerman et al 2015). Paulikas and Blake (1979), for example, analyzed energetic electron data from ATS-1, ATS-5 and ATS-6 spacecraft and found a pronounced positive correlation between the electron fluxes and solar wind speed.…”

Section: Solar Wind Driversmentioning

confidence: 99%

“…The mechanism behind the riometer principle involves enhanced electron density produced in the D region ionosphere, causing increased electron collision rates with sufficient frequency to attenuate HF radio waves transiting the atmosphere. Riometers can be used in event and statistical studies (e.g., Baker et al 1981;Spanswick et al 2007) and can also be used in infer temporal evolution of population fluxes from the overlying magnetosphere (Kellerman et al 2015). Riometer technology has evolved from simpler wide beam systems to analog and now digital beam forming, wide frequency capture imaging systems, with the latter providing much better measurement precision and/or much higher spatial resolution for temporal and spatial precipitation loss studies (e.g., Honary et al 2011).…”

Section: Loss Mechanismsmentioning

confidence: 99%

Space Weather Effects in the Earth’s Radiation Belts

et al. 2017

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The first major scientific discovery of the Space Age was that the Earth is enshrouded in toroids, or belts, of very high-energy magnetically trapped charged particles. Early observations of the radiation environment clearly indicated that the Van Allen belts could be delineated into an inner zone dominated by high-energy protons and an outer zone dominated by high-energy electrons. The energy distribution, spatial extent and particle species makeup of the Van Allen belts has been subsequently explored by several space missions. Recent observations by the NASA dual-spacecraft Van Allen Probes mission have revealed many novel properties of the radiation belts, especially for electrons at highly relativistic and ultra-relativistic kinetic energies. In this review we summarize the space weather impacts of the radiation belts. We demonstrate that many remarkable features of energetic particle changes are driven by strong solar and solar wind forcings. Recent comprehensive data show broadly and in many ways how high energy particles are accelerated, transported, and lost in the magnetosphere due to interplanetary shock wave interactions, coronal mass ejection impacts, and high-speed solar wind streams. We also discuss how radiation belt particles are intimately tied to other parts of the geospace system through atmosphere, ionosphere, and plasmasphere coupling. The new data have in many ways rewritten the textbooks about the radiation belts as a key space weather threat to human technological systems.

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