The “SafeSpace” database of ULF power spectral density and radial diffusion coefficients: dependencies and application to simulations
<p>Radial diffusion has been established as one of the most important mechanisms contributing to both the acceleration and loss of relativistic electrons in the outer radiation belt, as well as to the supply of particles to the inner radiation belt. In the framework of the “SafeSpace” project,...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-06-01
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| Series: | Annales Geophysicae |
| Online Access: | https://angeo.copernicus.org/articles/40/379/2022/angeo-40-379-2022.pdf |
| Summary: | <p>Radial diffusion has been established as one of the most important
mechanisms contributing to both the acceleration and loss of
relativistic electrons in the outer radiation belt, as well as to the
supply of particles to the inner radiation belt. In the framework of
the “SafeSpace” project, we have used 9 years (2011–2019) of multi-point
magnetic and electric field measurements from THEMIS A, D and E
satellites to create a database of radial diffusion coefficients
(<span class="inline-formula"><i>D</i><sub>LL</sub></span>) and ultra-low-frequency (ULF) wave power spectral densities
(PSDs) spanning an <span class="inline-formula"><i>L</i><sup>∗</sup></span> range from 3 to 8. In this work we
investigate the dependence of the <span class="inline-formula"><i>D</i><sub>LL</sub></span> on the various solar wind
parameters, geomagnetic indices and coupling functions, as well as the
L-shell, during the solar cycle 24. Moreover, we discuss the
uncertainties introduced on the estimation of <span class="inline-formula"><i>D</i><sub>LL</sub></span> time series by
the partial azimuthal coverage provided by in situ
measurements. Furthermore, we investigate, via a superposed analysis,
the dependence of the <span class="inline-formula"><i>D</i><sub>LL</sub></span> on solar wind drivers. We show, for the
first time to the best of our knowledge, that the interplanetary coronal mass
ejection (ICME)-driven disturbances accompanied by high solar wind
pressure values combined with intense magnetospheric compression can
produce <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M6" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>D</mi><mi mathvariant="normal">LL</mi><mi mathvariant="normal">B</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="19pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="8c91677e2710d804aad563f1ccb63a3b"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-40-379-2022-ie00001.svg" width="19pt" height="17pt" src="angeo-40-379-2022-ie00001.png"/></svg:svg></span></span> values comparable to or even greater than the
ones of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M7" display="inline" overflow="scroll" dspmath="mathml"><mrow><msubsup><mi>D</mi><mi mathvariant="normal">LL</mi><mi mathvariant="normal">E</mi></msubsup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="19pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="436eaef613984dae2b995cf092da46cf"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="angeo-40-379-2022-ie00002.svg" width="19pt" height="17pt" src="angeo-40-379-2022-ie00002.png"/></svg:svg></span></span>. This feature cannot be captured by
semi-empirical models and introduces a significant energy dependence
on the <span class="inline-formula"><i>D</i><sub>LL</sub></span>. Finally, we show the advantages of using <span class="inline-formula"><i>D</i><sub>LL</sub></span>
time series by means of numerical simulations of relativistic electron
fluxes performed with the Salammbô code and significant deviations in the predictions of several semi-empirical models depending on the level of geomagnetic activity and L-shell.</p> |
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| ISSN: | 0992-7689 1432-0576 |