Cold and hot spicules observed with ALMA, IRIS and AIA/SDO

We succeeded in observing two large spicules with the Atacama Large Millimeter/submillimeter Array (ALMA), the Interface Region Imaging Spectrograph explorer (IRIS), and the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory, simultaneously. One is a spicule seen in the IRIS Mg II slit-jaw images and AIA 304 A images (MgII/304A spicule). The other one is a spicule seen in the 100 GHz images obtained with ALMA (100 GHz spicule).

Although the 100 GHz spicule in the early phase overlapped with the MgII/304A spicule, we cannot find any remarkable enhancement caused by the 100 GHz spicule in the IRIS Mg II and AIA 304 A images. Moreover, there is no overlapped region between the 100 GHz spicule and Mg II/304A spicule in the late phase. It would suggest that the spicules are individual events and do not have a physical relationship.

We estimated two optical depths of the 100 GHz spicule. One is calculated from the observed brightness temperature, and the other one is estimated with an emission model and the assumed temperature and density. As a result of comparing them, the temperature and density of the 100 GHz spicule are 4000 – 8000 K and ~2.2×10^10 cm-3. The estimated values can explain the absorbing structure that is the counterpart of the 100 GHz spicule in the 193A images.