High-frequency torsional Alfvén waves as an energy source for coronal heating

Area of Science:

• Solar Astrophysics
• Heliophysics
• Plasma Physics

Background:

• The Sun's hot atmosphere and solar wind acceleration remain key unresolved problems in solar astrophysics.
• Magnetohydrodynamic (MHD) modes and magnetic energy dissipation are implicated in solar atmospheric heating and mass cycling, but direct evidence is debated.

Purpose of the Study:

• To provide direct observational evidence for the mechanisms driving solar atmospheric heating and solar wind acceleration.
• To investigate the role of torsional motions in the solar chromosphere.

Main Methods:

• Utilized ground-based 1-meter Swedish Solar Telescope (SST) with CRISP spectropolarimeter.
• Conducted observations in the Hα 6562.8 Å spectral line.
• Analyzed data from a quiet-Sun field-of-view (60" × 60") on June 10, 2014.
• Employed stringent numerical modeling to interpret observations.

Main Results:

• First detection of ubiquitous high-frequency (~12-42 mHz) torsional motions in thin, spicular-type chromospheric structures.
• Observed numerous oscillating magnetic flux tubes, consistent with torsional Alfvén waves driven by high-frequency sources.
• Quantified significant energy flux (~10⁵ W m⁻²) in the chromosphere and substantial energy transfer (~10³ W m⁻²) to the corona after partial reflection.

Conclusions:

• Oscillating flux tubes are substantial sources of Alfvén wave generation in the solar chromosphere.
• These waves provide sufficient Poynting flux to heat the corona and originate the supersonic solar wind.
• The findings offer direct evidence supporting Alfvénic wave heating and solar wind acceleration theories.