First Results of the Chromospheric LAyer Spectro-Polarimeter (CLASP2)

Advanced high-spatial and temporal resolution observations revealed that the solar chromosphere is highly dynamic and that it plays an important role on the transport of energy to the corona. Therefore, there is growing demand to obtain quantitative information on the magnetic field in the upper chromosphere and transition region. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), launched on 2015 September 3, opened up a new window in this research field; for the first time, it successfully detected the linear polarization produced by scattering process in the hydrogen Lyman-α (121.57 nm) and Si III resonance (120.6 nm) lines and identified the operation of the Hanle effect (i.e., the modification of the scattering polarization due to the presence of magnetic field in the upper chromosphere and the transition region). Following the success of CLASP, a second sounding rocket experiment, called the Chromospheric LAyer SpectroPolarimeter (CLASP2), was launched on April 11 2019 after refitting the CLASP instrument. CLASP2 carried out full spectro-polarimeteric observations in the Mg II h & k lines, which are also UV spectral lines of great interest for exploring the magnetic fields of the upper solar chromosphere. One of the advantages of these spectral lines is that the circular polarization induced by the Zeeman effect is measurable, in addition to the linear polarization caused by scattering processes. This facilitates the determination of both the strength and direction of the magnetic fields via the Hanle and Zeeman effects. In order to facilitate the detection of circular polarization, a plage region as well as a quiet Sun near the limb were observed during a total observing time of 6 minutes. In this presentation, we present the CLASP2 instrument, the measured polarization profiles in the Mg II h & k lines and our preliminary findings.