تقرير
Suprathermal Ion Energy spectra and Anisotropies near the Heliospheric Current Sheet crossing observed by the Parker Solar Probe during Encounter 7
| العنوان: | Suprathermal Ion Energy spectra and Anisotropies near the Heliospheric Current Sheet crossing observed by the Parker Solar Probe during Encounter 7 |
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| المؤلفون: | Desai, M. I., Mitchell, D. G., McComas, D. J., Drake, J. F., Phan, T., Szalay, J. R., Roelof, E. C., Giacalone, J., Hill, M. E., Christian, E. R., Schwadron, N. A., McNutt Jr., R. L., Wiedenbeck, M. E., Joyce, C., Cohen, C. M. S., Davis, A. J., Krimigis, S. M., Leske, R. A., Matthaeus, W. H., Malandraki, O., Mewaldt, R. A., Labrador, A., Stone, E. C., Bale, S. D., Verniero, J., Rahmati, A., Whittlesey, P., Livi, R., Larson, D., Pulupa, M., MacDowall, R. J., Niehof, J. T., Kasper, J. C., Horbury, T. S. |
| سنة النشر: | 2021 |
| المجموعة: | Astrophysics Physics (Other) |
| مصطلحات موضوعية: | Astrophysics - Solar and Stellar Astrophysics, Physics - Space Physics |
| الوصف: | We present observations of >10-100 keV/nucleon suprathermal (ST) H, He, O, and Fe ions associated with crossings of the heliospheric current sheet (HCS) at radial distances <0.1 au from the Sun. Our key findings are: 1) very few heavy ions are detected during the 1st full crossing, the heavy ion intensities are reduced during the 2nd partial crossing and peak just after the 2nd crossing; 2) ion arrival times exhibit no velocity dispersion; 3) He pitch-angle distributions track the magnetic field polarity reversal and show up to ~10:1 anti-sunward, field-aligned flows and beams closer to the HCS that become nearly isotropic further from the HCS; 4) the He spectrum steepens either side of the HCS and the He, O, and Fe spectra exhibit power-laws of the form ~E^4-6; and 5) maximum energies EX increase with the ion's charge-to-mass (Q/M) ratio as EX/EH proportional to [(QX/MX)]^alpha where alpha~0.65-0.76, assuming that the average Q-states are similar to those measured in gradual and impulsive solar energetic particle events at 1 au. The absence of velocity dispersion in combination with strong field-aligned anisotropies closer to the HCS appears to rule out solar flares and near-sun coronal mass ejection-driven shocks. These new observations present challenges not only for mechanisms that employ direct parallel electric fields and organize maximum energies according to E/Q, but also for local diffusive and magnetic reconnection-driven acceleration models. Re-evaluation of our current understanding of the production and transport of energetic ions is necessary to understand this near-solar, current-sheet-associated population of ST ions. Comment: 4 Figures, 2 Tables |
| نوع الوثيقة: | Working Paper |
| DOI: | 10.3847/1538-4357/ac4961 |
| URL الوصول: | http://arxiv.org/abs/2111.00954 |
| رقم الأكسشن: | edsarx.2111.00954 |
| قاعدة البيانات: | arXiv |
| DOI: | 10.3847/1538-4357/ac4961 |
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