Evidence of H<sup>+</sup>‐Band EMIC Waves in the Inner Radiation Belt Observed by Van Allen Probes During Magnetic Storms

He, Zhaohai; Xu, Jiyao; Wang, Chi; Dai, Lei; Ni, Binbin; Roth, I.

doi:10.1029/2022ja031088

Cited by 2 publications

(3 citation statements)

References 47 publications

(81 reference statements)

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“…The lower limit L* = 3.25 of the EMIC diffusion model is imposed by the limitations of the instruments used (Ross et al, 2020). He et al (2023) present evidence for EMIC waves in the inner radiation belt during storms, so EMIC wave power may be missed at lower L*. If this is the case, then the actual loss timescales for energies above 1 MeV at L* < 3.25 during active periods may be faster than those presented here.…”

Section: Discussionmentioning

confidence: 60%

“…For 2.6 MeV electrons in Figure 2 there is a local peak in the loss timescales around L* = 3.5 for the two lowest activity levels that is not present in the data. The EMIC diffusion coefficients employed here are only defined for L* > 3.25, but He et al (2023) present evidence for EMIC waves in the inner radiation belt, so EMIC wave power may be missed at lower L*. Alternatively, as this peak is present at low levels of activity it is unlikely to be due to chorus, but may be due to underestimating hiss, either because the hiss model does not include low frequency hiss (Ni et al, 2014) or does not account fully for variations in the wave-normal angle (Hartley et al, 2018).…”

Section: Electron Loss Timescalesmentioning

confidence: 99%

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A New Model of Electron Pitch Angle Distributions and Loss Timescales in the Earth's Radiation Belts

Glauert,

Atkinson,

Ross

et al. 2024

JGR Space Physics

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As the number of satellites on orbit grows it is increasingly important to understand their operating environment. Physics‐based models can simulate the behavior of the Earth's radiation belts by solving a Fokker‐Planck equation. Three‐dimensional models use diffusion coefficients to represent the interactions between electromagnetic waves and the electrons. One‐dimensional radial diffusion models neglect the effects of energy diffusion and represent the losses due to the waves with a loss timescale. Both approaches may use pitch angle distributions (PADs) to create boundary conditions, to map observations from low to high equatorial pitch angles and to calculate phase‐space density from observations. We present a comprehensive set of consistent PADs and loss timescales for 2 ≤ L* ≤ 7, 100 keV ≤ E ≤ 5 MeV and all levels of geomagnetic activity determined by the Kp index. These are calculated from drift‐averaged diffusion coefficients that represent all the VLF waves that typically interact with radiation belt electrons and show good agreement with data. The contribution of individual waves is demonstrated; magnetosonic waves have little effect on loss timescales when lightning‐generated whistlers are present, and chorus waves contribute to loss even in low levels of geomagnetic activity. The PADs vary in shape depending on the dominant waves. When chorus is dominant the distributions have little activity dependence, unlike the corresponding loss timescales. Distributions peaked near 90° are formed by plasmaspheric hiss for L* ≤ 3 and E < 1 MeV, and by EMIC waves for L* > 3 and E > 1 MeV. When hiss dominates, increasing activity broadens the distribution but when EMIC waves dominate increasing activity narrows the distribution.

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Section: Discussionmentioning

confidence: 60%

Section: Electron Loss Timescalesmentioning

confidence: 99%

A New Model of Electron Pitch Angle Distributions and Loss Timescales in the Earth's Radiation Belts

Glauert,

Atkinson,

Ross

et al. 2024

JGR Space Physics

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“…This spatially close development occurred due to the unusually strong equatorward movement of the plasmapause. During the main phase of the storm, characterized by a long‐duration SYM‐H minimum, high‐energy protons in the inner radiation belt can become depleted but then regain their original state immediately in the recovery phase (Xu et al., 2019; He et al., 2023). The exact mechanisms behind this quick drop in high‐energy proton flux are still unknown, but nonadiabatic processes are suspected.…”

Section: Discussionmentioning

confidence: 99%

Uncovering the Drivers of Responsive Ionospheric Dynamics to Severe Space Weather Conditions: A Coordinated Multi‐Instrumental Approach

Calabia,

Imtiaz,

Altadill

et al. 2024

JGR Space Physics

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Space‐weather conditions can often have a detrimental impact on satellite communications and limited experimental data has made it challenging to understand the complex processes that occur in the upper atmosphere. To overcome this challenge, we utilized a coordinated multi‐instrumental dataset consisting of GNSS airglow remote sensing, ionosonde, magnetometer, and in‐situ satellite data to investigate plasma depletions. We present a case study focused on the geomagnetic storm that occurred on 27 February 2014. During the storm, GNSS positioning errors exceeded undisturbed levels by at least 2 times, and ionospheric corrections reached amplitudes of up to ±20 m at the Rabat station. We identified 3 large depletions that were most likely generated by sudden vertical ionospheric drifts that began at approximately 17:00 UTC at sunset in Morocco and the southern regions of Spain. These drifts reached ∼500 m/s and lasted until 22:00 UTC. The observed depletions propagated to the northeast, as seen through ionosonde echoes and ground‐based airglow images. Satellite limb‐images revealed an ionospheric uplift of about 100 km due to the storm, consistent with ionosondes in Spain. The observed local anomalies may be influenced by variations in equatorial electric current flows, which are correlated with fluctuations in ground‐based magnetometer data. These variations are likely a result of the effects of the inner radiation belt on the development of plasma bubbles in the African longitude sector. Sudden enhancements in upward E × B drift caused ionospheric uplift to higher altitudes, enhancing the “fountain effect” and shifting the Equatorial Ionospheric Anomaly crests to higher latitudes.

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Evidence of H⁺‐Band EMIC Waves in the Inner Radiation Belt Observed by Van Allen Probes During Magnetic Storms

Cited by 2 publications

References 47 publications

A New Model of Electron Pitch Angle Distributions and Loss Timescales in the Earth's Radiation Belts

A New Model of Electron Pitch Angle Distributions and Loss Timescales in the Earth's Radiation Belts

Uncovering the Drivers of Responsive Ionospheric Dynamics to Severe Space Weather Conditions: A Coordinated Multi‐Instrumental Approach

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Evidence of H+‐Band EMIC Waves in the Inner Radiation Belt Observed by Van Allen Probes During Magnetic Storms

Cited by 2 publications

References 47 publications

A New Model of Electron Pitch Angle Distributions and Loss Timescales in the Earth's Radiation Belts

A New Model of Electron Pitch Angle Distributions and Loss Timescales in the Earth's Radiation Belts

Uncovering the Drivers of Responsive Ionospheric Dynamics to Severe Space Weather Conditions: A Coordinated Multi‐Instrumental Approach

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Product

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Evidence of H⁺‐Band EMIC Waves in the Inner Radiation Belt Observed by Van Allen Probes During Magnetic Storms