On the Close Correspondence Between Storm Time ULF Wave Power and the POES VLF Chorus Wave Amplitude Proxy

Dimitrakoudis, Stavros; Mann, I. R.

doi:10.1029/2018gl081317

Cited by 3 publications

(3 citation statements)

References 53 publications

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“…There is a secondary enhancement of the ULF wave power later in the day, contemporaneous with the timing of the chorus wave activity observed by ERG. This behavior is similar to that observed by Dimitrakoudis and Mann (2019) where they reported a close correspondence between the timing of the enhanced chorus and ULF wave power across multiple events and locations. Interestingly, previous studies have shown that high amplitude ULF waves may modulate whistler wave growth (e.g., Shang et al., 2021; Watt et al., 2011).…”

Section: Resultssupporting

confidence: 90%

Rapid Acceleration Bursts in the Van Allen Radiation Belt

Olifer,

Morley,

Ozeke

et al. 2024

JGR Space Physics

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The fast Van Allen radiation belt electron dynamics during geomagnetic storms have not yet been fully explained, in part due to limitations of standard satellite missions in both orbit and the number of spacecraft. Here we overcome these limitations using measurements from the Global Positioning System (GPS) constellation during an acceleration event on 26 August 2018. We show that the acceleration of relativistic electrons occurs in two distinct bursts, each dominated by a different acceleration mechanism. The first burst enhances the radiation belt electrons by four orders of magnitude in 2 hr and is consistent with ULF‐wave radial diffusion. The second burst is likely caused by the local acceleration and delivers an order‐of‐magnitude increase in 20 min. This work demonstrates how distributed, operational measurements can be used to resolve phenomena not observable with previous capabilities, and that rapid energization of the radiation belt can occur much faster than previously reported.

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Section: Resultssupporting

confidence: 90%

Rapid Acceleration Bursts in the Van Allen Radiation Belt

Olifer,

Morley,

Ozeke

et al. 2024

JGR Space Physics

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“…For example, Li et al (2015) noted such an observational relationship, suggesting that the chorus waves were the causal agent explaining the relativistic electron acceleration. However, as noted in subsequent work by Dimitrakoudis and Mann (2019), those same intense radiation belt enhancement events can be equally distinguished based on the observed ULF wave power, with electron acceleration events also occurring in association with intense ULF waves. Overall, our results imply a potential further complication when trying to identify causality in acceleration pathways.…”

Section: Discussionmentioning

confidence: 69%

A Natural Limit to the Spectral Hardness of Worst Case Electron Radiation in the Terrestrial Van Allen Belt

et al. 2022

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The flux of relativistic electrons in the terrestrial Van Allen radiation belt can vary by orders of magnitude during a geomagnetic storm. The response is typically assumed to be controlled by an often delicate balance between acceleration and loss processes. Here we analyze all 133 magnetic storms from the NASA Van Allen Probes era. We show how the belts demonstrate a repeatable response which limits not only the worst case flux, but also controls and delivers a limit to the severity of the spectral hardness, consistent with the theory of Kennel and Petschek first developed over 50 years ago. When this theory is extended to relativistic energies, the observed electron flux is seen to reach a naturally limited worst case with a clear energy dependence. Here we show how the Kennel‐Petschek theory can explain the evolution and hardening of the electron spectrum during geomagnetic storms. It also introduces an energy‐dependent maximum flux limit. This limit is never reached during the Van Allen Probes era at energies above 2.6 MeV, meanwhile, it is reached within hours at lower energies (∼100 keV) in almost every storm. No current radiation belt models include this effect; without it, they cannot accurately predict the consequent radiation dynamics. Overall, our results demonstrate how this creates a remarkable absolute natural limit to both the spectral hardness and the severity of extreme electron space radiation.

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“…The same applies for EBR, IZN, SFS, and FIN maximum GICx index values. A possible explanation could be that these values are linked to magnetospheric ULF pulsations of the Pc5 range ( f = 2 − 7 mHz); and indeed, as we can see in Figure S8 in Supporting Information , where we have plotted the integrated ULF power per UT hour in that frequency range for four of our magnetometers (calculated as in Dimitrakoudis & Mann (2019)), there is a spike of ULF wave activity at that time, that is, at 16:00 to 17:00 UT.…”

Section: Resultsmentioning

confidence: 70%

Investigation of the Geomagnetically Induced Current Index Levels in the Mediterranean Region During the Strongest Magnetic Storms of Solar Cycle 24

et al. 2023

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Geomagnetically induced currents (GICs) constitute an integral part of space weather research and are a subject of ever‐growing attention for countries located in the low and middle latitudes. A series of recent studies highlights the importance of considering GIC risks for the Mediterranean region. Here, we exploit data from the HellENIc GeoMagnetic Array, which is deployed in Greece, complemented by magnetic observatories in the Mediterranean region (Italy, France, Spain, Algeria, and Turkey), to calculate values of the GIC index, that is, a proxy of the geoelectric field calculated entirely from geomagnetic field variations. We perform our analysis for the most intense magnetic storms (Dst < −150 nT) of solar cycle 24. Our results show that GIC index increases are well correlated with storm sudden commencements. However, the GIC indices do not exceed “low” activity levels despite the increases in their values, at all magnetic stations/observatories under study during the selected storm events.

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On the Close Correspondence Between Storm Time ULF Wave Power and the POES VLF Chorus Wave Amplitude Proxy

Cited by 3 publications

References 53 publications

Rapid Acceleration Bursts in the Van Allen Radiation Belt

Rapid Acceleration Bursts in the Van Allen Radiation Belt

A Natural Limit to the Spectral Hardness of Worst Case Electron Radiation in the Terrestrial Van Allen Belt

Investigation of the Geomagnetically Induced Current Index Levels in the Mediterranean Region During the Strongest Magnetic Storms of Solar Cycle 24

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