Helium is the second most abundant element in the universe after hydrogen. But scientists are not sure how much is actually in the Sun’s atmosphere, where it is difficult to measure. Knowing the amount of helium in the solar wind is important for understanding the origin and acceleration of solar energy – a constant stream of charged particles from the Sun.
In 2009, NASA Launched a solid rocket probe to measure helium in the expanding solar atmosphere – the first time we have collected a complete global map. Results have recently been published Nature astronomy, Helping us better understand our space environment.
Earlier, when measuring the proportion of helium in the solar wind when it reached the Earth, observations have found much lower ratios than expected. Scientists suspect that the missing helium has been left behind in the sun’s outermost atmospheric layer – the corona – or perhaps a deeper layer. Find out how this happens is important to understand how solar wind accelerates.
To measure the amount of atmospheric helium and hydrogen, NASA’s helium resonance scattering in the corona and heliosphere, or Herschel, the sounding rocket took images of the solar corona. Was an international collaboration with Herschel, led by the Naval Research Lab in Washington, DC Osservatorio Astrofisico di Torino In italy and Institute D’strophistic Spatial in France.
Herschel’s observations showed that helium was not evenly distributed around the corona. There was almost no helium in the equatorial region, while areas in the middle latitudes had the highest. Comparison of images from ESA / NASA’s Solar and Heliospheric Observatory (SOHO), Scientists were able to show abundance at mid latitudes with the opening of the Sun’s magnetic field lines into the solar system.
This suggests that the ratio of hydrogen to helium is strongly associated with the magnetic field and the speed of the solar wind in the corona. The equatorial regions, which had low helium abundance measurements, corresponded to measurements from the solar wind near the Earth. This indicates that the solar atmosphere is more dynamic than scientists think.
The HERSCHEL sounding rocket probe connects to a body working to understand the origin of the slow component of the solar body. Herschel remotely examines the fundamental structure of the region where the solar wind accelerates, which can be analyzed by in situ measurements of the internal solar system, such as the Parker Solar Probe. While the sun’s heat is sufficient to allow the lightest element – ionized hydrogen protons – to escape the sun in the form of supersonic air, other physics should help in the acceleration of heavier elements such as helium. Thus, understanding the instantaneous abundance in the Sun’s atmosphere, provides additional information as we try to learn the full story of how solar wind accelerates.
In the future, scientists plan to make more observations to explain the difference in abundance. Two new instruments on ESA / NASA’s Solar Orbiter – Métis and EUI are capable of making similar global abundance measurements and will help provide new information about helium ratios in the corona.
Reference: John D. “Global Helium Abundance Measurements in the Solar Corona” by Moses, Esther Antousi, Jeffrey Newmark, Frederick Aucherre, Silvano Fineschi, Marco Romoli, Daniele Telloni, Giusepp Massone, Luca Jangrilli, Mauro Focardi, Federico Landini. , Guglielmo Rossi, Andrea M. Malvezzi, Denis Wang, Jean-Christophe Leclesch, Jean-Pierre Mallick, Frédéric Roussel, Lucia Abo, Aurelin Canou, Nicolas Barbe, Chloe Guenneau, John M. Lamming, James P. Lemon Wuelser, John L. Kohl and Lawrence D. Gardner, 27 July 2020, Nature astronomy.
DOI: 10.1038 / s41550-020-1156-6