Inconspicuous Solar Polar Coronal X-ray Jets as the Source of Conspicuous Hinode/EUV Imaging Spectrometer (EIS) Doppler Outflows

TL;DR

This study reveals that faint, inconspicuous solar polar X-ray jets are likely common sources of coronal outflows and may significantly contribute to solar wind and magnetic switchbacks, despite their subtle appearance in imaging data.

Contribution

The paper demonstrates that faint X-ray jets, previously overlooked, are consistent with known jet properties and could be more prevalent than recognized, impacting solar wind models.

Findings

All five events are consistent with faint coronal X-ray jets.

Events originate from minifilament eruptions with velocities of 19-46 km/s.

Faint jets may be more numerous and influential in solar wind dynamics.

Abstract

We examine in greater detail five events previously identified as being sources of strong transient coronal outflows in a solar polar region in Hinode/EUV Imaging Spectrometer (EIS) Doppler data. Although relatively compact or faint and inconspicuous in Hinode/Soft X-ray Telescope (XRT) soft-X-ray (SXR) images and in Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) EUV images, we find that all of these events are consistent with being faint coronal X-ray jets. The evidence for this is that the events result from eruption of minifilaments of projected sizes spanning 5000 -- 14,000 km and with erupting velocities spanning 19 -- 46 km/s, which are in the range of values observed in cases of confirmed X-ray polar coronal hole jets. In SXR images, and in some EUV images, all five events show base brightenings, and faint indications of a jet spire that (in four of five cases where determinable) moves away from the brightest base brightening; these properties are common to more obvious X-ray jets. For a comparatively low-latitude event, the minifilament erupts from near (<~few arcsec) a location of near-eruption-time opposite-polarity magnetic-flux-patch convergence, which again is consistent with many observed coronal jets. Thus, although too faint to be identified as jets a priori, otherwise all five events are identical to typical coronal jets. This suggests that jets may be more numerous than recognized in previous studies, and might contribute substantially to solar wind outflow, and to the population of magnetic switchbacks observed in Parker Solar Probe (PSP) data.