Radial Evolution of Sunward Strahl Electrons in the Inner Heliosphere

0536256 - ÚFA 2021 RIV NL eng J - Článek v odborném periodiku
Macneil, A.R. - Owens, M.J. - Lockwood, M. - Štverák, Štěpán - Owen, C. J.
Radial Evolution of Sunward Strahl Electrons in the Inner Heliosphere.
Solar Physics. Roč. 295, č. 2 (2020), č. článku 16. ISSN 0038-0938. E-ISSN 1573-093X
Institucionální podpora: RVO:68378289
Klíčová slova: Magnetic fields * interplanetary * Magnetic reconnection * Solar wind * observational signatures
Obor OECD: Astronomy (including astrophysics,space science)
Impakt faktor: 2.671, rok: 2020
Způsob publikování: Open access
https://doi.org/10.1007/s11207-019-1579-3

The heliospheric magnetic field (HMF) exhibits local inversions, in which the field apparently ´bends back´ upon itself. Candidate mechanisms to produce these inversions include various configurations of upstream interchange reconnection: either in the heliosphere, or in the corona where the solar wind is formed. Explaining the source of these inversions, and how they evolve in time and space, is thus an important step towards explaining the origins of the solar wind. Inverted heliospheric magnetic field lines can be identified by the anomalous sunward (i.e. inward) streaming of the typically anti-sunward propagating, field-aligned (or anti-aligned), beam of electrons known as the ´strahl´. We test if the pitch angle distribution (PAD) properties of sunward-propagating strahl are different from those of outward strahl. We perform a statistical study of strahl observed by the Helios spacecraft, over heliocentric distances spanning approximate to 0.3 - 1 AU. We find that sunward strahl PADs are broader and less intense than their outward directed counterparts: particularly at distances 0.3 - 0.75 AU. This is consistent with sunward strahl being subject to additional, path-length dependent, scattering in comparison to outward strahl. We conclude that the longer and more variable path from the Sun to the spacecraft, along inverted magnetic field, leads to this additional scattering. The results also suggest that the relative importance of scattering along this additional path length drops off with heliocentric distance. These results can be explained by a relatively simple, constant-rate, scattering process.
Trvalý link: http://hdl.handle.net/11104/0314070