We propose to investigate and constrain two of the prominent scenarios to explain qpps, 1) the successive magnetic reconnection loop arcade and 2) the most feasible locations of density…

The Smithsonian Institution, through its Smithsonian Astrophysical Observatory (SAO) division, has been awarded a $322,332.00 grant by the National Aeronautics and Space Administration (NASA) to investigate two scenarios that could explain quasi-periodic pulsations (QPPs) in solar flare emissions. The research will involve running simulations using the HYDRAD field-aligned hydrodynamics code to model successive magnetic reconnection loop arcades and the effects of density perturbations predicted by magnetohydrodynamic (MHD) theory. The goal is to determine the observable signatures that can distinguish between these potential causes of QPPs in the impulsive and gradual phases of solar flares. This work supports NASA's and the National Science Foundation's objectives to understand the origin of the Sun's activity and characterize fundamental processes within the heliosphere. The contract does not have a set-aside designation, and no subcontractors are mentioned.

We propose to investigate and constrain two of the prominent scenarios to explain qpps, 1) the successive magnetic reconnection loop arcade and 2) the most feasible locations of density perturbations suggested by MHD theory. We will examine the first possibility using an arcade model of a solar flare, where each loop is successively energized to determine how this drives qpps. In the second case, we will constrain density perturbations from the predictions of MHD in order to determine where and how mass is added to field lines, which we will inject into the flaring loops. In order to perform this work, we will run simulations with the hydrad field-aligned hydrodynamics code, which solves the equations describing the conservation of mass, momentum, and energy for a two-fluid plasma constrained to magnetic flux tube. IT includes detailed physics from the chromosphere through the corona, for a coronal loop of arbitrary length, cross-sectional area expansion, and gravity profile. IT solves for a full loop, allowing for asymmetric profiles, and importantly makes use of adaptive mesh refinement, ensuring that the transition region and shocks are properly spatially resolved. The code includes functions for heating due to electron beams, alfv NIC wave dissipation, and thermal heating of any specified properties. Hydrad importantly includes the effect of non-equilibrium ionization, allowing for accurate determination of ionization states which is crucial to accurate calculation of radiative losses and forward modeled spectral lines. We will simulate many loops, project them onto locations in the solar atmosphere consistent with a few specific observed flares, and synthesize the temporal, spatial and spectral emission. We will compare these synthetic observables to measurements from goes XRS, ESP, SDO AIA, rhessi and minxss when available to constrain the imposed timing, heating duration, and geometry of the successive reconnecting loops, and refine the locations of the density perturbations. These simulations will be used to predict what observable signatures can discriminate between the potential causes of qpps. In summary, the goal of this proposal is to understand the qpps in solar flare emission, in both the impulsive and gradual phase, and determine whether IT can be explained by successive arcade reconnection or MHD perturbations. These results will then be used to provide a list of observables that future instrumentation must be able to achieve to eliminate the remaining competing models. This work addresses two of the fundamental science goals of the 2013-2022 decadal survey in solar and space physics: to determine the origins of the sun s activity and predict the variations in the space environment and to discover and characterize the fundamental processes that occur both within the heliosphere and throughout the universe.