SO/PHI and the first autonomously obtained magnetic map of the Sun

Instituto de Astrofísica de Andalucía (IAA-CSIC)
  • SO/PHI, co-developed by the Instituto de Astrofísica de Andalucía, has obtained the first magnetic map of the Sun surface with no human intervention, directly from space
  • The results were included among the first publicly released data obtained by the mission Solar Orbiter developed by ESA in collaboration with NASA


The Solar Orbiter mission, developed by the European Space Agency (ESA) with the participation of NASA, took off towards its orbit around the Sun on February 9th, 2020. The mission was designed to observe the Sun from an unprecedented perspective to study the solar physics and the influence of the Sun in the interplanetary medium.

Some months before the launch the experiment had already obtained its first scientific results, which were to be presented in an open press conference. Among them is the first magnetic map of the Sun obtained from space without any direct human intervention, and which was sent towards Planet Earth by the SO/PHI instrument, co-developed by the Instituto de Astrofísica de Andalucía (IAA-CSIC).

Map of the solar magnetic field, obtained by SO/PHI.

The mission was to extend until November 2021, in which the orbital plane will be elevated in order to acess higher latitutes and which will allow to obtain the first high-quality view of the magnetic field of the poles. During the initial cruise phase, pointed out José Carlos del Toro Iniesta, researcher at IAA-CSIC co-leading the SO/PHI instrument development: “the instruments onboard the ship have not been inactive during the trip: they have been completing the initial setup stage, in which the activity has been focusing on testing that all the complex measurement systems are functioning correctly and, in case of observing any deviations, to find measures to solve or mitigate them”.

The Solar Orbiter orbit around the Sun was planned to have a minimum distance closer to the Sun than that of Mercury and outside of the ecliptic, the plane of Earth's orbit around the Sun. This disposition would provide for a unique perspective and observe the poles of the Sun. Its instruments, moreover, woult then be able to take both local and remote measurements, which in turn would make possible to provide the first complete view both of Solar physics as that of the Heliosphere.

Solar Orbiter is the first space mission with Spanish leadership in two instruments: the EPD instrument, a detector of energetic particles that is led by the University of Alcalá (Spain) and the University of Kiel (Germany), and the magnetograph PHI, led by the Max Planck institute of Solar System Research (Göttingen, Germany) and IAA-CSIC of Granada.


SO/PHI: When science is done on-flight

SO/PHI (which stands for Solar Orbiter/Polarimetric and Helioseismic Imager) is a generator of polarimetric and heliosismological images whose main objective resides on performing a precise cartography of the magnetic solar field. This field is responsible for virtually all major phenomena one can observe at/from the Sun, such as sunspots, solar storms or solar wind (the continuous flux of electrically charged particles emanating from the Sun, traversing interplanetary space). An objective of SO/PHI is also to measure the speed of plasma in the photosphere, the most internal layer of the solar atmosphere and from where solar winds arise.

SO/PHI was built by an international consortium (45 % German, 42 % Spanish, 10 % French). The Spanish section of the consortium developed, among other systems, the Full Disk Telescope (FDT), with the participation of the National Institute of Aerospace Technology (INTA), the Universidad Politécnica de Madrid, the University of Valencia, the University of Barcelona and the Instituto de Astrofísica de Canarias, a SOMMa member like IAA-CSIC.

Figure showing several of the maps obtained using the SO/PHI instrument and its technical features and sub-components.

The figure above shows some of the results made available by SO/PHI. The first row displays a detail of the Sun taken with the high-resolution telescope SO/PHI (left box). Next, it shows the mapped magnetic solar field obtained with the high-resolution telescope (middle box), where the green and brown colours represent the two polarities (North and South) of the magnetic field. The right box of the same row shows the solar surface velocity map (right box), in which the areas in red indicate descending movements, while those in blue indicate ascending solar plasma.

The lower row shows an image of the Sun with the full-disk telescope of SO/PHI (left box), followed by a map of the magnetic solar field (middle box) and a map of velocities obtained by the same telescope (right box). “The second row of images of SO/PHI shows the Sun completely both in terms of light intensity as of circular polarization. The Sun is during a period of low activity and no visible structures are observed in the intensity image, but one can observe magnetic structures on the surface of the circular polarization map. For the obtention of the first row of images a high-resolution telescope was used, which allows for more details and allows, from the one side, to clearly distinguish the solar granulation (bubbles of solar gas) and, from the other, provides the first autonomously obtained magnetogram made in space”, indicated José Carlos del Toro Iniesta.

The feature of instrument autonomy is one of the singularities of SO/PHI, made possible by its electronic inverter, the first one in its category developed to date. Instead of sending the original data to Earth, the device allows to perform the science on-board: it transforms the measurements in maps of solar physics magnitudes, erases the first ones to free memory and sends the resulting outcomes towards the operations centre. “Normally, such a map is obtained by a tedious process involving fifty computers on Earth, taking a considerable time”, concludes Toro Iniesta. The results were included in the first data release of the ESA Solar Orbiter mission, in collaboration with NASA.


Image credits:

Frontpage picture of a sunspot is in the public domain and was downloaded from Wikimedia Commons.

All solar maps by SOLAR ORBITER/ PHI/ ESA/ NASA were kindly provided by IAA-CSIC and re-used with permission.

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