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The unprecedented solar magnetic field map created by the CLASP2 space experiment



CLASP2 observes the solar magnetic field in the active area

Artistic visualization of the solar magnetic field in the active area observed through CLASP2. Image source: SMM (IAC) Gabriel Pérez Díaz

Every day the space telescope will provide spectacular images of solar activity. However, their instruments turned a blind eye to the main driving force: the magnetic field in the outer layer of the sun’s atmosphere would cause explosions that sometimes affect the earth. The extraordinary observation of the solar ultraviolet polarization through the CLASP2 mission makes it possible to map the magnetic field of the entire solar atmosphere from the photosphere to the extremely hot corona.The survey was published in the magazine today Scientific progressThis research was conducted by an international team in charge of suborbital experiments, which included several scientists from the POLMAG team of the Institute of Aeronautics and Astronautics of Canaria (IAC).

The chromosphere is a very important area of ​​the solar atmosphere. It is located between the relatively thin and cool light layer (with a temperature of several thousand degrees) and the hotter and extended corona (with a temperature of more than one million degrees). Thousands of kilometers. Although the temperature of the chromosphere layer is about a hundred times lower than that of the corona, the density of the chromosphere layer is much higher, so more energy is required to maintain it. In addition, the mechanical energy required to heat the corona needs to pass through the chromosphere, making it a key interface area for solving many key problems in solar and stellar physics. One of the current scientific challenges is to understand the origin of the violent activities of the sun’s atmosphere, which in some cases disturbs the Earth’s magnetosphere and has serious consequences for our current technological world.

Sun activity area observed by CLASP2 and Hinode at the same time

The red image obtained with NASA’s SDO telescope shows the active area observed by both CLASP2 and Hinode. The green line on the left panel indicates the slit position of the CLASP2 spectrometer. At each point on the slit, CLASP2 measures the intensity of the various chromatic sphere lines of the solar ultraviolet spectrum (top right) and the wavelength changes of circular polarization (bottom right). At the same time, the space telescope Hinode measured the circular polarization of the photosphere in the visible spectrum. This circular polarization signal is generated by the magnetic field of different heights in the solar atmosphere, and the researchers can determine the change in the magnetic field from the photosphere to the bottom of the corona. Image source: NAOJ, IAC, NASA/MSFC, IAS

“If we cannot determine the magnetic field of the chromosphere, especially in its outer layer, plasma Javier Trujillo Bueno, CSIC professor of IAC and chief scientist of the IAC POLMAG group, said: “The temperature is about 10,000 degrees, and the magnetic force dominates the structure and dynamics of the plasma.” The theory conducted by the group funded by the European Research Council Advanced Research Studies have shown that this goal can be achieved by observing the polarization produced by various physical mechanisms in the radiation emitted by the sun’s neutral hydrogen and ionized magnesium atoms. Chromosphere layer.

Since the earth’s atmosphere strongly absorbs solar ultraviolet radiation, it must be observed at an altitude of more than 100 kilometers.To this end, an international consortium was established by NASA The Marshall Space Flight Center (NASA/MSFC), the National Astronomical Observatory of Japan (NAOJ), the French Institute of Space Astrophysics (IAS) and the Canaria Institute of Astronomy (IAC) in Spain. The international team designed a series of space experiments that were selected through competitive calls in the NASA sounding rocket program. These space experiments are called CLASP, “Atmospheric Lyman-Alpha Spectrometer” (CLASP1, launched on September 3, 2015) and “Atmospheric Spectrometer” (CLASP2, launched on April 11, 2019). Both experiments achieved great success, and the National Aeronautics and Space Administration (NASA) awarded the International Team a “Group Achievement Honor Award” in recognition of him.

Longitudinal component of the magnetic field

The longitudinal component (Gauss) of the magnetic field at each point along the spatial direction indicated by the green line in the left picture of Figure 1. The strongest and weakest magnetic field magnetization area (up to 1250 Gauss) is found in the photosphere (green curve) It is separated by other areas of weak magnetization (10 Gauss). When moving horizontally in the photosphere, this significant change in magnetic field intensity decreases at the height corresponding to the lower chromosphere layer (blue symbol), and is in the middle layer (black symbol) and outside the chromosphere layer. The layer (red symbol) is smaller. These results confirm and prove that in such an active area of ​​the solar atmosphere, the force lines of the magnetic field expand and fill the entire chromosphere before reaching the bottom of the corona. Image source: NAOJ, IAC, NASA/MSFC, IAS

The research paper was recently published in a famous journal Scientific progress Based on a small part of the unprecedented data obtained by CLASP2. The team analyzed the intensity and circular polarization of the ultraviolet rays emitted by the solar atmospheric active region within the spectral range containing the h and k lines of Mg II (ionized magnesium) of about 2800 angstroms (see Figure 1). In this spectral region, there are also two spectral lines produced by Mn I (neutral manganese) atoms.

The circular polarization observed by CLASP2 comes from a physical mechanism called the Zeeman effect, through which the radiation emitted by atoms under the action of a magnetic field is polarized. The circular polarization signal of the magnesium (Mg II) wire is sensitive to the magnetic field in the middle and outer regions of the solar chromosphere, while the circular polarization signal of the manganese (Mn I) wire responds to the deepest magnetic field. One of the scientists of the POLMAG group and the international group A Tanausúdel Pino Alemán explained.

When observing at CLASP2, Hinode The space telescope points to the same active area on the solar disk simultaneously. Andrés Asensio Ramos, another IAC researcher involved in the project, pointed out: “By the polarization observed in the neutral iron (Fe I) spectral lines in the visible range of the spectrum, information about the magnetic field of the optical layer can be obtained.” The team also used the IRIS space telescope to conduct simultaneous observations, measuring the intensity of ultraviolet light with a higher spatial resolution (IRIS is not designed to measure polarization).

The team research led by Dr. Ryohko Ishikawa (NAOJ) and Dr. Javier Trujillo Bueno (IAC), for the first time mapped the magnetic field of CLASP2 in the active region observed in the entire atmosphere from the photosphere to the atmosphere. The bottom of the corona (see Figure 2). Ernest Alsina Ballester, an international team researcher, commented: “This mapping of the magnetic field at various heights in the solar atmosphere has great scientific significance because it will help us Decipher the magnetic coupling between different regions of the sun’s atmosphere.” His first postdoctoral fellow in Switzerland had just joined IAC.

The results obtained confirm and prove that in these regions of the solar atmosphere, the lines of force of the magnetic field expand and fill the entire chromosphere before reaching the bottom of the corona. Another important result of this research is that the magnetic field intensity of the outer layer of the chromosphere is closely related to the radiation intensity at the center of the magnesium wire and the electron pressure in the same layer, thereby revealing the magnetic source of heating. In the outer region of the solar atmosphere.

The CLASP1 and CLASP2 space experiments represent a milestone in astrophysics. It is the first observation of relatively weakly polarized signals generated by various physical mechanisms in the solar ultraviolet spectrum. Such observations surprisingly confirmed the previous theoretical predictions, thus verifying the quantum theory of the production and transfer of polarized radiation used by these scientists in studying the magnetic field of the solar chromosphere.

The international team has just received good news that NASA has selected their most recent proposal for a new space experiment next year, which will allow them to map the magnetic field on a larger solar disk. “Of course, the systematic observation of solar ultraviolet radiation intensity and polarization will require a space telescope equipped with CLASP instruments, because the few minutes of observation time allowed for suborbital flight experiments are not enough,” Javier clarified. Trujillo Bueno. The team firmly believes that due to the achievements of CLASP1 and CLASP2, such space telescopes will soon become a reality, and the physical interpretation of their spectropolarized observations will enable people to better understand the magnetic activity of the sun and other outer layers. star.

Reference: “from the photosphere to the corona of the Sun’s magnetic field mapping of the bottom”, author: Ryoko Ishikawa, Javier Trujillo Bueno, Ta Nusuo del Pino Aleman, Takemoto · Tetsuo Okamoto, David McKenzie, Frederick O’Cher, Rapin Cano, Dong Xu Song, Masaki Yoshida, Laurel A. Luca Belluzzi, Jiri Stepan ), Andrés Asensio Ramos (Andrés Asensio Ramos), Matt Carlsson (Mats Carlsson) and Jorrit Leenaarts (Jorrit Leenaarts), February 19, 2021, Scientific progress.
DOI: 10.1126/sciadv.abe8406

The main researcher of CLASP2 space experiment:

  • David McKenzie (NASA/MSFC, USA)
  • Ryoko Ishikawa (NAOJ, Japan)
  • Frédéric Auchère (IAS, France)
  • Javier Trujillo Bueno (IAC, Spain)

IAC scientists participating in CLASP2:

  • Ernest Alcina Ballest (IAC)
  • Andres Asensio Ramos (IAC)
  • German Pine Tanausú (IAC)
  • Javier Trujillo Bueno (IAC)

CLASP2 is an international collaboration consisting of the Marshall Space Flight Center of the National Aeronautics and Space Administration (NASA) (USA), the National Astronomical Observatory of Japan (Tokyo, Japan), and the Institute of Astronomy of Canarias (IAC, Tenerife, Spain) And the Spanish Institute of Space Research (IAS), France). Other members are Istituto Ricerche Solari Locarno (Switzerland), Institute of Astronomy of the Academy of Sciences of the Czech Republic, Lockheed Martin Laboratory of Solar Energy and Astrophysics (USA), Stockholm University (Sweden) and Rosseland Center for Solar Physics (Norway).

IAC’s participation in CLASP2 activities was funded from the European Research Council (ERC) under the European Union’s Horizon 2020 Research and Innovation Program (Advanced Grant Agreement No. 742265).




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