for calibrating the EIS data using IDL routine EIS\_PREP available in the SSW. We fitted the EIS spectral line profiles with Gaussian function using EIS\_AUTO\_FIT. Spatial offset between EIS images obtained from different wavelengths were corrected with respect to image obtained from  195.12 [Å]{} spectral line.

![image](fig4.eps){width="80.00000%"}

Figure \[fig:context\_loc\] shows the locations of the ARTBs in IRIS-SJIs recorded at 1330 [Å]{} and 1400 [Å]{}, XRT Be-thin filter image, AIA 171 [Å]{} and 193 [Å]{} images. Corresponding line-of-sight (LOS) magnetic field map obtained from HMI is plotted in the bottom right panel. A and B in the bottom left panel locates the two ARTBs that appear simultaneously. Both the ARTBs appeared and peaked at the same time in different passbands of IRIS and AIA. Intensity contours corresponding to the ARTBs obtained from AIA 171 [Å]{} at its peak are over-plotted on the HMI LOS magnetic map. The region covered by these contours show the presence of a strong gradient in the magnetic field underneath ARTBs as compared to its surroundings. At point A, the average strength of LOS magnetic field is about $-400$ G, which is surrounded by an average magnetic field strength of $-50$ G. Point B, shows strong gradient 