Speaker
L. Kleint
Description
The Mg II h & k lines are useful diagnostics for physical processes in the solar
chromosphere. A long-standing question is how their central reversals in the line
cores disappear and turn into emission during flares. To address this question, we
carried out a joint observational and modeling study of the well-observed X1.0 flare
on 2014 March 29. We analyzed the Mg II h & k spectra observed by IRIS. We then
constructed a multi-threaded flare loop model and used the time-dependent electron
flux inferred from the RHESSI hard X-ray data as the input to the radiative
hydrodynamic code RADYN to simulate the atmospheric response. From the simulation
result, we synthesized the Mg II h & k intensity using the RH code and compared them
with the IRIS observations, where we found a general agreement. In particular, we
successfully produced the single-peaked Mg II h & k line profiles by increasing
electron density in the upper chromosphere within a narrow height range of ≈ 800 km
below the transition region. To our knowledge, this is the first successful attempt
in reproducing such line-profile shapes under flaring conditions. We will discuss the
implications of this result for diagnosing atmospheric dynamics and energy transport
in solar flares.
Author
Fatima Rubio da Costa
(Stanford University)
