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|Title:||Physical properties of solar polar jets. A statistical study with Hinode XRT data||Authors:||Paraschiv, A. R.
Sterling, A. C.
|Issue Date:||2015||Journal:||ASTRONOMY & ASTROPHYSICS||Number:||579||First Page:||A96||Abstract:||Aims. The target of this work is to investigate the physical nature of polar jets in the solar corona and their possible contribution to coronal heating and solar wind flow based on the analysis of X-ray images acquired by the Hinode XRT telescope. We estimate the different forms of energy associated with many of these small-scale eruptions, in particular the kinetic energy and enthalpy. Methods. Two Hinode XRT campaign datasets focusing on the two polar coronal holes were selected to analyze the physical properties of coronal jets; the analyzed data were acquired using a series of three XRT filters. Typical kinematical properties (e.g., length, thickness, lifetime, ejection rate, and velocity) of 18 jets are evaluated from the observed sequences, thus providing information on their possible contribution to the fast solar wind flux escaping from coronal holes. Electron temperatures and densities of polar-jet plasmas are also estimated using ratios of the intensities observed in different filters. Results. We find that the largest amount of energy eventually provided to the corona is thermal. The energy due to waves may also be significant, but its value is comparatively uncertain. The kinetic energy is lower than thermal energy, while other forms of energy are comparatively low. Lesser and fainter events seem to be hotter, thus the total contribution by polar jets to the coronal heating could have been underestimated so far. The kinetic energy flux is usually around three times smaller than the enthalpy counterpart, implying that this energy is converted into plasma heating more than in plasma acceleration. This result suggests that the majority of polar jets are most likely not escaping from the Sun and that only cooler ejections could possibly have enough kinetic energy to contribute to the total solar wind flow.||Acknowledgments:||A.R.P. would like to thank the INAF-Turin Astrophysical Observatory, the Faculty of Physics of the University of Bucharest, and the Department of Physics of the University of Turin for funding and support of this work. A.C.S. was supported by funding from NASA’s Office of Space Science through the Living With a Star Targeted Research Technology Program. A.C.S. also benefited from discussions held at the International Space Science Institute’s (ISSI, Bern, Switzerland) International Team on Solar Coronal Jets. Hinode is a solar physics science mission of the Japan Aerospace Exploration Agency (JAXA) in collaboration with the United States and the UK.||URI:||http://hdl.handle.net/20.500.12386/23481||URL:||https://www.aanda.org/articles/aa/abs/2015/07/aa25671-15/aa25671-15.html||ISSN:||0004-6361||DOI:||10.1051/0004-6361/201525671||Bibcode ADS:||2015A&A...579A..96P||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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