On the transition from Slow to Fast Wind as Observed in Composition Observations
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arXiv
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| Auteurs principaux: | , , , |
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| Format: | Preprint |
| Publié: |
2024
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| _version_ | 1866910834963251200 |
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| author | Alterman, B. L. Rivera, Y. J. Lepri, S. T. Raines, R. M. |
| author_facet | Alterman, B. L. Rivera, Y. J. Lepri, S. T. Raines, R. M. |
| contents | The solar wind is typically categorized as fast and slow based on the measured speed ($v_\mathrm{sw}$). The separation between these two regimes is often set between 400 and 600 km/s without a rigorous definition. Observations of the solar wind's kinetic signatures, chemical makeup, charge state properties, and Alfvénicity suggest that such a two-state model may be insufficiently nuanced to capture the relationship between the solar wind and its solar sources. We test this two-state fast/slow solar wind paradigm with heavy ion abundances (X/H) and characterize how the transition between fast and slow wind states impacts heavy ion in the solar wind. We show that (1) the speed at which heavy ion abundances indicate a change between fast and slow solar wind as a function of speed is slower than the speed indicated by the helium abundance; (2) this speed is independent of heavy ion mass and charge state; (3) the abundance at which heavy ions indicate the transition between fast and slow wind is consistent with prior observations of fast wind abundances; (4) and there may be a mass or charge-state dependent fractionation process present in fast wind heavy ion abundances. We infer that (1) identifying slow solar wind as having a speed $v_\mathrm{sw} \lesssim$ 400 km/s may mix solar wind from polar and equatorial sources; (2) He may be impacted by the acceleration necessary for the solar wind to reach the asymptotic fast, non-transient values observed at 1 AU; and (3) heavy ions are fractionated in the fast wind by a yet-to-be-determined mechanism. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2411_18984 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | On the transition from Slow to Fast Wind as Observed in Composition Observations Alterman, B. L. Rivera, Y. J. Lepri, S. T. Raines, R. M. Solar and Stellar Astrophysics Space Physics The solar wind is typically categorized as fast and slow based on the measured speed ($v_\mathrm{sw}$). The separation between these two regimes is often set between 400 and 600 km/s without a rigorous definition. Observations of the solar wind's kinetic signatures, chemical makeup, charge state properties, and Alfvénicity suggest that such a two-state model may be insufficiently nuanced to capture the relationship between the solar wind and its solar sources. We test this two-state fast/slow solar wind paradigm with heavy ion abundances (X/H) and characterize how the transition between fast and slow wind states impacts heavy ion in the solar wind. We show that (1) the speed at which heavy ion abundances indicate a change between fast and slow solar wind as a function of speed is slower than the speed indicated by the helium abundance; (2) this speed is independent of heavy ion mass and charge state; (3) the abundance at which heavy ions indicate the transition between fast and slow wind is consistent with prior observations of fast wind abundances; (4) and there may be a mass or charge-state dependent fractionation process present in fast wind heavy ion abundances. We infer that (1) identifying slow solar wind as having a speed $v_\mathrm{sw} \lesssim$ 400 km/s may mix solar wind from polar and equatorial sources; (2) He may be impacted by the acceleration necessary for the solar wind to reach the asymptotic fast, non-transient values observed at 1 AU; and (3) heavy ions are fractionated in the fast wind by a yet-to-be-determined mechanism. |
| title | On the transition from Slow to Fast Wind as Observed in Composition Observations |
| topic | Solar and Stellar Astrophysics Space Physics |
| url | https://arxiv.org/abs/2411.18984 |