DETERMINATION OF CORONAL MASS EJECTION PHYSICAL PARAMETERS FROM A COMBINATION OF POLARIZED VISIBLE LIGHT AND UV Ly alpha OBSERVATIONS

作者：Susino R; Bemporad A

来源：Astrophysical Journal, 2016, 830(2): 58.

DOI：10.3847/0004-637X/830/2/58

<jats:title>ABSTRACT</jats:title>
<jats:p>Visible-light observations of Coronal Mass Ejections (CMEs) performed with coronagraphs and heliospheric imagers (in primis on board the <jats:italic>Solar and Heliospheric Observatory</jats:italic> and <jats:italic>STEREO</jats:italic> missions) have offered the best way to study the kinematics and geometrical structure of these fundamental events so far. Nevertheless, it has been widely demonstrated that only combination of multi-wavelength data (including X-ray spectra, EUV images, EUV-UV spectra, and radio dynamic spectra) can provide complete information on the plasma temperature and density distributions, non-thermal motions, magnetic fields, and other physical parameters, for both CMEs and CME-related phenomena. In this work, we analyze three CMEs by combining simultaneous data acquired in the polarized visible light by the LASCO-C2 coronagraph and in the UV <jats:sc>H</jats:sc> <jats:sc>i</jats:sc> Ly<jats:italic>α</jats:italic> line (1216 Å) by the UVCS spectrometer, in order to estimate the CME plasma electron density (using the polarization-ratio technique to infer the 3D structure of the CME) and temperature (from the comparison between the expected and measured Ly<jats:italic>α</jats:italic> intensities) along the UVCS field of view. This analysis is primarily aimed at testing the diagnostic methods that will be applied to coronagraphic observations of CMEs delivered by the Metis instrument on board the next ESA-Solar Orbiter mission. We find that CME cores are usually associated with cooler plasma (<jats:inline-formula>
<jats:tex-math>
<?CDATA $T\sim {10}^{6}$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa36f2ieqn1.gif" xlink:type="simple" />
</jats:inline-formula> K), and that a significant increase of the electron temperatures is observed from the core to the front of the CME (where <jats:inline-formula>
<jats:tex-math>
<?CDATA $T\gt {10}^{6.3}$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaa36f2ieqn2.gif" xlink:type="simple" />
</jats:inline-formula> K), which seems to be correlated, in all cases, with the morphological structure of the CME as derived from visible-light images.</jats:p>

• 出版日期2016-10-20