The Incompressible Magnetohydrodynamic Energy Cascade Rate Upstream of Mars: Effects of the Total Energy and the Cross-Helicity on Solar Wind Turbulence
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arXiv
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| Natura: | Preprint |
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2024
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| author | Romanelli, Norberto Andres, Nahuel DiBraccio, Gina Verniero, Jaye Gruesbeck, Jacob Szabo, Adam Espley, Jared Halekas, Jasper |
| author_facet | Romanelli, Norberto Andres, Nahuel DiBraccio, Gina Verniero, Jaye Gruesbeck, Jacob Szabo, Adam Espley, Jared Halekas, Jasper |
| contents | Solar wind turbulence is a dynamical phenomenon that evolves with heliocentric distance. Orbiting Mars since September 2014, Mars Atmosphere and Volatile EvolutioN (MAVEN) offers a unique opportunity to explore some of its main properties beyond ~1.38 au. Here, we analyze solar wind turbulence upstream of Mars's bow shock, utilizing more than five years of magnetic field and plasma measurements. This analysis is based on two complementary methodologies: 1) the computation of magnetohydrodynamic (MHD) invariants characterizing incompressible fluctuations; 2) the estimation of the incompressible energy cascade rate at MHD scales (i.e., $\langle\varepsilon^{T}\rangle_{MHD}$). Our results show the solar wind incompressible fluctuations are primarily in a magnetically dominated regime, with the component travelling away from the Sun having a higher median pseudo-energy. Moreover, turbulent fluctuations have a total energy per mass of up to ~300 km2 s-2, a range smaller than reported at 1 au. For these conditions, we determine the probability distribution function of $\langle\varepsilon^{T}\rangle_{MHD}$ ranges mainly between ~-1x10-16 and ~1x10-16 J m-3 s-1, with a median equal to -1.8x10-18 J m-3 s-1, suggesting back-transfer of energy. Our results also suggest that $|\langle\varepsilon^{T}\rangle_{MHD}|$ is correlated with the total energy per mass of fluctuations and that the median of $\langle\varepsilon^{T}\rangle_{MHD}$ does not vary significantly with the cross-helicity. We find, however, that the medians of the inward and outward pseudo-energy cascade rates vary with the solar wind cross-helicity. Finally, we discuss these results and their implications for future studies that can provide further insight into the factors affecting solar wind energy transfer rate. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2406_18349 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The Incompressible Magnetohydrodynamic Energy Cascade Rate Upstream of Mars: Effects of the Total Energy and the Cross-Helicity on Solar Wind Turbulence Romanelli, Norberto Andres, Nahuel DiBraccio, Gina Verniero, Jaye Gruesbeck, Jacob Szabo, Adam Espley, Jared Halekas, Jasper Solar and Stellar Astrophysics Earth and Planetary Astrophysics Space Physics Solar wind turbulence is a dynamical phenomenon that evolves with heliocentric distance. Orbiting Mars since September 2014, Mars Atmosphere and Volatile EvolutioN (MAVEN) offers a unique opportunity to explore some of its main properties beyond ~1.38 au. Here, we analyze solar wind turbulence upstream of Mars's bow shock, utilizing more than five years of magnetic field and plasma measurements. This analysis is based on two complementary methodologies: 1) the computation of magnetohydrodynamic (MHD) invariants characterizing incompressible fluctuations; 2) the estimation of the incompressible energy cascade rate at MHD scales (i.e., $\langle\varepsilon^{T}\rangle_{MHD}$). Our results show the solar wind incompressible fluctuations are primarily in a magnetically dominated regime, with the component travelling away from the Sun having a higher median pseudo-energy. Moreover, turbulent fluctuations have a total energy per mass of up to ~300 km2 s-2, a range smaller than reported at 1 au. For these conditions, we determine the probability distribution function of $\langle\varepsilon^{T}\rangle_{MHD}$ ranges mainly between ~-1x10-16 and ~1x10-16 J m-3 s-1, with a median equal to -1.8x10-18 J m-3 s-1, suggesting back-transfer of energy. Our results also suggest that $|\langle\varepsilon^{T}\rangle_{MHD}|$ is correlated with the total energy per mass of fluctuations and that the median of $\langle\varepsilon^{T}\rangle_{MHD}$ does not vary significantly with the cross-helicity. We find, however, that the medians of the inward and outward pseudo-energy cascade rates vary with the solar wind cross-helicity. Finally, we discuss these results and their implications for future studies that can provide further insight into the factors affecting solar wind energy transfer rate. |
| title | The Incompressible Magnetohydrodynamic Energy Cascade Rate Upstream of Mars: Effects of the Total Energy and the Cross-Helicity on Solar Wind Turbulence |
| topic | Solar and Stellar Astrophysics Earth and Planetary Astrophysics Space Physics |
| url | https://arxiv.org/abs/2406.18349 |