Can coronal hole spicules reach coronal temperatures?

Abstract

Aims. The present study aims to provide observational evidence of whether coronal hole spicules reach coronal temperatures. Methods. We combine multi-instrument co-observations obtained with the SUMER/SoHO and with the EIS/SOT/XRT/Hinode. Results. The analysed three large spicules were found to be comprised of numerous thin spicules that rise, rotate, and descend simultaneously forming a bush-like feature. Their rotation resembles the untwisting of a large flux rope. They show velocities ranging from 50 to 250 km s −1 . We clearly associated the red-and blue-shifted emissions in transition region lines not only with rotating but also with rising and descending plasmas. Our main result is that these spicules although very large and dynamic, are not present in the spectral lines formed at temperatures above 300 000 K.Conclusions. In this paper we present the analysis of three Ca ii H large spicules that are composed of numerous dynamic thin spicules but appear as macrospicules in lower resolution EUV images. We found no coronal counterpart of these and smaller spicules. We believe that the identification of phenomena that have very different origins as macrospicules is due to the interpretation of the transition region emission, and especially the He ii emission, wherein both chromospheric large spicules and coronal X-ray jets are present. We suggest that the recent observation of spicules in the coronal AIA/SDO 171 Å and 211 Å channels probably comes from the existence of transition region emission there.

Magnetohydrodynamic waves and their stability status in solar spicules

“…However, spicules can be considered as Alfvén wave resonant cavities (Hollweg 1981;Leroy 1981) and as Matsumoto & Shibata (2010) claim, the waves of the period around 100−500 s can transport a large amount of wave energy to the corona. In all cases, the question of whether large coronal spicules can reach coronal temperatures remains open -for a discussion from an observational point of view we refer to Madjarska et al (2011).…”

Chromospheric jets around the edges of sunspots

“…A number of other studies have also shown that down flows are associated with higher TR temperatures (T ∼ 0.6−1.0 MK) A&A 543, A6 (2012) and high speed up-flows are seen at coronal temperatures (T > 1 MK), e.g. Marsch et al (2004Marsch et al ( , 2008, Bryans et al (2010), , Kamio et al (2011).…”

Two-fluid Numerical Simulations of Solar Spicules

“…They are best seen at the solar limb in strong chromospheric and transition-region (TR) spectral lines such as Hα, Ca ii H & K, Mg ii H & K, C ii and Si iv lines (e.g., Roberts 1945;Matsuno & Hirayama 1988;Nishikawa 1988;Suematsu et al 1995;De Pontieu et al 2007b;Suematsu et al 2008;Sterling et al 2010;Madjarska et al 2011;Pereira et al 2012;Tsiropoula et al 2012;Skogsrud et al 2014Skogsrud et al , 2015Pereira et al 2014;Rouppe van der Voort et al 2015;Pereira et al 2016;Beck et al 2016). Spicule observations have been carried out for about 130 years since they were first reported in 1877 (Secchi 1887).…”