38 research outputs found

    Magnetic nulls and super-radial expansion in the solar corona

    Get PDF
    Magnetic fields in the sun's outer atmosphere -- the corona -- control both solar-wind acceleration and the dynamics of solar eruptions. We present the first clear observational evidence of coronal magnetic nulls in off-limb linearly polarized observations of pseudostreamers, taken by the Coronal Multichannel Polarimeter (CoMP) telescope. These nulls represent regions where magnetic reconnection is likely to act as a catalyst for solar activity. CoMP linear-polarization observations also provide an independent, coronal proxy for magnetic expansion into the solar wind, a quantity often used to parameterize and predict the solar wind speed at Earth. We introduce a new method for explicitly calculating expansion factors from CoMP coronal linear-polarization observations, which does not require photospheric extrapolations. We conclude that linearly-polarized light is a powerful new diagnostic of critical coronal magnetic topologies and the expanding magnetic flux tubes that channel the solar wind

    Mapping the magnetic field in the solar corona through magnetoseismology

    Get PDF
    Magnetoseismology, a technique of magnetic field diagnostics based on observations of magnetohydrodynamic (MHD) waves, has been widely used to estimate the field strengths of oscillating structures in the solar corona. However, previously magnetoseismology was mostly applied to occasionally occurring oscillation events, providing an estimate of only the average field strength or one-dimensional distribution of field strength along an oscillating structure. This restriction could be eliminated if we apply magnetoseismology to the pervasive propagating transverse MHD waves discovered with the Coronal Multi-channel Polarimeter (CoMP). Using several CoMP observations of the Fe XIII 1074.7 nm and 1079.8 nm spectral lines, we obtained maps of the plasma density and wave phase speed in the corona, which allow us to map both the strength and direction of the coronal magnetic field in the plane of sky. We also examined distributions of the electron density and magnetic field strength, and compared their variations with height in the quiet Sun and active regions. Such measurements could provide critical information to advance our understanding of the Sun’s magnetism and the magnetic coupling of the whole solar atmosphere
    corecore