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A 17 June 2011 polar jet and its presence in the background solar wind  

Nai-Hwa Chen   Submitted: 2017-02-09 23:29

High-speed jet responses in the polar solar wind are enigmatic. Here we measure a jet response that emanates from the southern polar coronal hole on 17 June 2011 at the extreme speed of over 1200 km s-1. This response was recorded from the Sun-Earth line in Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) and Large Angle and Spectrometric Coronagraph/C2 and both Solar TErrestrial RElations Observatory Extreme Ultraviolet Imager and COR2 coronagraphs when the three spacecraft were situated ~90° from one another. These certify the coronal 3-D location of the response that is associated with an existing solar plume structure and show its high speed to distances of over 14 RS. This jetting is associated with magnetic flux changes in the polar region as measured by the SDO/Helioseismic and Magnetic Imager instrumentation over a period of several hours. The fastest coronal response observed can be tracked to a time near the period of greatest flux changes and to the onset of the brightest flaring in AIA. This high-speed response can be tracked directly as a small patch of outward moving brightness in coronal images as in Yu et al. (2014) where three slower events were followed from the perspective of Earth. This accumulated jet response has the largest mass and energy we have yet seen in 3-D reconstructions from Solar Mass Ejection Imager observations, and its outward motion is certified for the first time using interplanetary scintillation observations. This jet response is surrounded by similar high-speed patches, but these are smoothed out in Ulysses polar measurements, we speculate about how these dynamic activities relate to solar wind acceleration.

Authors: H.-S. Yu, B.V. Jackson, Y.-H. Yang, N.-H. Chen, A. Buffington, P. P. Hick
Projects: Other

Publication Status: publlished
Last Modified: 2017-02-10 11:07
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Undercover EUV Solar Jets Observed by the Interface Region Imaging Spectrograph  

Nai-Hwa Chen   Submitted: 2016-10-26 19:17

It is well-known that extreme ultraviolet emission emitted at the solar surface is absorbed by overlying cool plasma. Especially in active regions dark lanes in EUV images suggest that much of the surface activity is obscured. Simultaneous observations from IRIS, consisting of UV spectra and slit-jaw images give vital information with sub-arcsecond spatial resolution on the dynamics of jets not seen in EUV images. We studied a series of small jets from recently formed bipole pairs beside the trailing spot of active region 11991, which occurred on 2014 March 5 from 15:02:21 UT to 17:04:07 UT. There were collimated outflows with bright roots in the SJI 1400 Å (transition region) and 2796 Å (upper chromosphere) that were mostly not seen in AIA 304 Å (transition region) and AIA 171 Å (lower corona) images. The Si IV spectra show strong blue-wing but no red-wing enhancements in the line profiles of the ejecta for all recurrent jets indicating outward flows without twists. We see two types of Mg II line profiles produced by the jets spires: reversed and non-reversed. Mg II lines remain optically thick but turn into optically thin in the highly Doppler shifted wings.The energy flux contained in each recurrent jet is estimated using a velocity differential emission measure technique which measures the emitting power of the plasma as a function of line-of-sight velocity. We found that all the recurrent jets release similar energy (108 erg cm-2 s-1 ) toward the corona and the downward component is less than 3%.

Authors: N.-H. Chen, D. E. Innes
Projects: None

Publication Status: Accepted for publication in ApJ
Last Modified: 2016-10-27 13:15
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A 17 June 2011 polar jet and its presence in the background solar wind
Undercover EUV Solar Jets Observed by the Interface Region Imaging Spectrograph

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