The mass cycle between the chromosphere and the corona/solar wind
Abstract
The plasma is not static but flows almost everywhere above the chromosphere. EUV and FUV spectroscopy reveals a lot of information of these mass flows, and thus enhances our understanding of coronal heating and solar wind origin. Through a single Gaussian fit to line profiles, emission lines formed in the transition region (TR) are usually found to exhibit ubiquitous redshifts. While coronal lines show predominant blueshifts in coronal holes (CHs), quiet-Sun (QS) network boundaries and active region (AR) edges. However, careful scrutiny of the line profiles indicates that they are obviously enhanced in the blue wings, suggesting the presence of a secondary high-speed upflow component besides the primary component. Meanwhile, imaging observations of HINODE/SOT and SDO/AIA clearly reveal ubiquitous episodic high-speed outflows in the form of type-II chromospheric spicules and propagating coronal disturbances (PDs). It has been suggested that the secondary component is associated with the type-II spicules and PDs, although further detailed investigations are needed to reach a solid conclusion. Moreover, recent AIA observations reveal slow downflows in cool passbands, which may represent the cooling of the previously heated plasma and should be embedded in TR line profiles. These heating upflows and cooling downflows are natural results of the mass cycling between the chromosphere and corona/solar wind, and their different relative intensities at different temperatures are likely to be responsible for the well-known temperature dependence of TR Doppler shift. So far various double Gaussian fit algorithms and red-blue asymmetry analysis techniques have been applied to coronal line profiles to derive parameters of the upflow component. However, an unambiguous decomposition of different components are still not possible by using data acquired by current spectrographs. The IRIS instrument, with a very small instrumental width and high spectral, temporal and spatial resolutions, might be able to unambiguously decompose different emission components in this continuous mass cycling process.
- Publication:
-
SDO-4: Dynamics and Energetics of the Coupled Solar Atmosphere. The Synergy Between State-of-the-Art Observations and Numerical Simulations
- Pub Date:
- March 2012
- Bibcode:
- 2012decs.confE...9T
- Keywords:
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- SDO;
- SDO-4;
- SDO 4;
- SDO Workshop;
- SDO-4/IRIS/Hinode Workshop;
- Solar Dynamic Observatory