Temperature and density structure of a recurring active region jet

Abstract

We present a study of a recurring jet observed on October 31, 2011 by SDO/AIA, Hinode/XRT and Hinode/EIS. We discuss the physical parameters of the jet such as density, differential emission measure, peak temperature, velocity and filling factor obtained using imaging and spectroscopic observations. A differential emission measure (DEM) analysis was performed at the region of the jet-spire and the footpoint using EIS observations and also by combining AIA and XRT observations. The DEM curves were used to create synthetic spectra with the CHIANTI atomic database. The plasma along the line-of-sight in the jet-spire and jet-footpoint was found to be peak at 2.0 MK. We calculated electron densities using the Fe XII (λ186/λ195) line ratio in the region of the spire (N e = 7.6×10 10 cm −3 ) and the footpoint (1.1×10 11 cm −3 ). The plane-of-sky velocity of the jet is found to be 524 km/s. The resulting EIS DEM values are in good agreement with those obtained from AIA-XRT. There is no indication of high temperatures, such as emission from Fe XVII (λ254.87) (log T [K] = 6.75) seen in the jet-spire. In case of the jet-footpoint, synthetic spectra predict weak contributions from Ca XVII (λ192.85) and Fe XVII (λ254.87). With further investigation, we confirmed emission from the Fe XVIII (λ93.932 Å) line in the AIA 94 Å channel in the region of the footpoint. We also found good agreement between the estimated and predicted Fe XVIII count rates. A study of the temporal evolution of the jet-footpoint and the presence of high-temperature emission from the Fe XVIII (log T [K] = 6.85) line leads us to conclude that the hot component in the jet-footpoint was present initially that the jet had cooled down by the time EIS observed it.

Study of the spatial association between an active region jet and a nonthermal type III radio burst

“…The EM analysis confirms that the hot plasma of temperature 5-8 MK was present at the footpoint region and also showed the presence of Fe xviii 93.93 Å emission, whereas the spire was at a low temperature of 2 MK. The spire temperature was found to be in good agreement with the temperatures obtained in other studies of AR jets (Mulay et al 2016(Mulay et al , 2017. The electron number densities in the spire and footpoint were found to be an order of magnitude lower compared to the densities measured for other jets studied by Mulay et al (2016Mulay et al ( , 2017Mulay et al ( , 2018.…”

Flare-related Recurring Active Region Jets: Evidence for Very Hot Plasma

“…The nonthermal velocities obtained from the Fe xxiv show good agreement with those obtained by Doschek et al (2015) in their individual study of M-class flare which showed surge like plasma ejection. The electron number density values obtained in the footpoint region of jet 1 and 2 were found to be lower than the values obtained for the jet studied in Mulay, Del Zanna, and Mason (2017b) and Doschek et al (2015), but show good agreement with the values obtained for the jet studied in Mulay et al (2016). The superhot plasma of 27 (25) MK was confirmed by FERMI during the rise (peak) phase of jet 1 whereas; peak temperature of 29 MK was measured at jet 2.…”

“…The densities obtained in the footpoint region of jet 1 and 2 using Fe xiv density diagnostics were found to be lower than the values obtained by Mulay, Del Zanna, and Mason (2017b) and Chifor et al (2008) using Fe xii density diagnostics except for one slit position (slit 19 for Fe xiv for AR jet 2) where the densities show good agreement. The densities show good agreement with the values obtained by Mulay et al (2016) which were lower limits to the densities.…”

“…The temperature structure of AR jets has been studied using imaging observations from the Atmospheric Imaging Assembly (AIA) (Chen, Ip, and Innes, 2013;Mulay et al, 2016;Mulay, Del Zanna, and Mason, 2017a), spectroscopic observation from the EUV Imaging Spectrometer (EIS) on board Hinode (Madjarska, 2011;Mulay, Del Zanna, and Mason, 2017b), the Interface Region Imaging Spectrograph (IRIS) (Mulay, Del Zanna, and Mason, 2017a) and RHESSI (Glesener, Krucker, and Lin, 2012). Making use of AIA observations in the DEM analysis, Chen, Ip, and Innes (2013) reported a temperature of 7 MK whereas Liu et al (2016) reported even higher temperature of 16 MK in a jet and suggested the possibility of nanoflares occurring at the footpoint region of the jet.…”

“…Making use of AIA observations in the DEM analysis, Chen, Ip, and Innes (2013) reported a temperature of 7 MK whereas Liu et al (2016) reported even higher temperature of 16 MK in a jet and suggested the possibility of nanoflares occurring at the footpoint region of the jet. Mulay, Del Zanna, and Mason (2017b) pointed out that there is always an uncertainty associated with temperature estimation using only imaging observations (such as AIA) in the DEM analysis. This is due to the lack of constraints on the low and high temperature part of the DEM solution.…”