The rapid rise of plasma temperature up to 1-2 MK from the solar photosphere towards the corona is still an unresolved problem in solar physics. It is clear that the mechanical energy of sub-photospheric motions is transported somehow into the upper solar atmosphere, where it may be dissipated leading to the heating of the ambient plasma. A possible scenario of energy transport is that the convective motions and solar global oscillations may excite magnetohydrodynamic (MHD) waves in the photosphere, which may then propagate through the chromosphere carrying relevant energy into the corona.
Here we propose (i) observing and tracking MHD waves from photosphere to chromosphere in magnetic bright points representing the QS and pores (or small sunspots) representing ARs; (ii) Next, by means of magneto-seismology of bright points and pores, we will determine not just the nature of these important features (potential or not) but will also construct for the first time their 3D magnetic map.
Magnetic bright points (MBPs) and pores are of the order of kG localised concentrations of magnetic flux that show up as bright features in H_alpha. Pores are often associated with plage. A considerable portion of the chromospheric radiation comes from these MBPs in the QS, while the emission associated with pores or small signposts is even more dominant in ARs. These abundant and intense features were long reported and can be considered an analogue to larger sunspots, the feet of complex, well developed ARs. High resolution images have revealed that the diameter of MBPs are ~ 1Mm in H_alpha, while pores may be slightly larger (few Mm). Beside the morphological and dynamic studies, there are early observationalreports on oscillatory phenomena both in bright points or pores. However, only a limited number of studies have addressed bright point or pore oscillations with recent high-resolution ground and space-based observations. It is strongly anticipated that signatures of the energy transport by MHD waves through the chromosphere may be detectable in the oscillatory dynamics of QS MBPs and AR pores.
A comprehensive novel observational study of waves and oscillations in MBPs and pores, to the best of our knowledge, is still lacking. An observational campaign could clarify very important details of (i) the degree of magnetic wave coupling from the photosphere to corona; (ii) topological 3D magnetic connectivity; and (iii) efficiency of wave energy dissipation. We plan to use existing Hinode & TRACE sequences, in addition to acquiring high-cadence ROSA & IBIS data (weather permitting).
Primary Objectives: The primary objective of this proposal is not only to study the dynamic activity in the lower solar atmosphere (i.e., identify the driver at photospheric levels) but to trace that activity to the TR and corona. Our observing setup will allow us to search for waves and oscillations in QS MBPs and AR pores, and use these waves by means of magneto-seismology to construct 3D magnetic mapping. Our ROSA/IBIS setup will allow us to (i)identify oscillatory power in velocity and/or intensity with frequencies above 2-3 mHz, thus confirming the existence of Alfvenic waves in MBPs; we expect to detect and discover Alfven waves in AR pores; (ii) perform simultaneous spectro-polarimetry of MBPs and pores which will allow us to link the oscillatory signatures in velocity and intensity (if any), with the magnetic field topology and field strength within the MBP and pore waveguide; (iii) estimate the energy flux that can be transmitted by the detected Alfven waves and oscillations. With XRT and EIS, we will acquire images and spectral data to enable a determination of the flow, temperatures and electron density structure in the upper atmosphere. SOT will provide magnetograms in Na D I, Ca II K and if possible H alpha line center and wing emission. TRACE will provide high-cadence observations with the 171 A filter. |
|