Introduction
*************
The rapid rise of plasma temperature in the solar atmosphere is still an unresolved problem in plasma-astrophysics. 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. The heating process(es) take(s) place both in active regions (AR) and in the quiet Sun (QS), whatever the latter means. It is likely that a combination of different heating processes operate in ARs and QS, however, it is not at all understood whether the nature of these heating processes is the same or not in the various plasma regions. A feasible common 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 comprehensive tracking MHD waves from photosphere to chromosphere in localised magnetic waveguides with emphases on the magnetic signatures of these waves; (ii) Next, we determine the actual identity and nature of the detected MHD waves (slow, fast, Alfven; kink, sausage; surface, body; etc.); (iii) By means of novel magneto-seismology we will determine not just the morphology of these localised MHD waveguides (potential or not) but will also construct their 3D magnetic mapping and attempt to determine their heating contribution through spatio-magneto seismology.
We plan to carry out these studies in localised magnetic structures called magnetic bright points (MBPs) and small pores. 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 sunspots 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 observational reports on oscillatory phenomena both in MBPs or pores. However, only a limited number of studies have addressed MBP or pore oscillations with recent high-resolution ground and space-based observations. Reports on magnetic oscillations of MBPs or pores are even more limited.
From MHD wave theory perspectives it is strongly anticipated that signatures of the energy transport by magnetic waves through the chromosphere may be detectable in the oscillatory dynamics of QS MBPs and AR pores both in Doppler and Stokes data.
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 about the (i) identity and (ii) degree of magnetic wave coupling from the photosphere to upper chromosphere; (iii) topological 3D magnetic connectivity; and (iv) efficiency of MHD wave energy transport (and dissipation). We plan to use 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 magnetic activity to the TR and corona. Our observing setup will allow us to search for simultaneous magnetic (full Stokes) and Doppler signatures of MHD 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 full Stokes parameters, velocity and/or intensity with frequencies above 2-3 mHz, thus confirming the existence of a range of magnetic waves (longitudinal, kink or Alfven) waves in lower solar atmospheric localised magnetic structures; we expect to detect and discover Alfven waves in AR pores in Stokes parameters!; (ii) perform simultaneous spectro-polarimetry of MBPs and pores which will allow us to link the oscillatory signatures in Stokes, velocity and intensity (if any), with the magnetic field topology and field strength within the localised (MBP, pore) waveguide; (iii) estimate the kinetic and magnetic energy flux that can be transmitted by the detected MHD 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 atmosphere.
Unprecedented high spatial resolution observation with SOT Spectro-Polarimeter (SP) aboard Hinode will provide magnetograms in Na D I, Ca II K and if possible H alpha line center and wing emission. SOT will observe the photosphere with SP (6301/6302 A) and with NFI magnetograms (5250.2 A). SP has a very skinny field of view to perform very high cadence of about a 1 min or even less, and Shutter-less NFI magnetograms provide wide-field context Stokes IQUV images at the blue wing with time cadence of about 30 sec. TRACE will provide high-cadence observations with the 171 A filter. |
|