First-ever clear images of nanojets

IRIS eyes Nanojets.

Nanojets are bright, thin lights perpendicular to the solar atmosphere’s magnetic structures, called the corona. They are considered as a “smoking gun,” key evidence of the presence of nanoflares.

Nanoflares are small explosions on the Sun—but they are difficult to spot. They are very fast and tiny, meaning they are hard to pick out against the bright surface of the Sun.

Each nanojet is believed to be initiated by a magnetic reconnection process where twisted magnetic fields explosively realign. One reconnection can set off another reconnection, creating an avalanche of nanojets in the corona of the Sun, a process that could create the energy that is heating the corona.

A new study reported the first-ever clear images of nanojets in a process that reveals one of the potential coronal heating candidates: nanoflares.

Through this study, scientists aimed to understand why the Sun’s atmosphere is hotter than the surface. They wanted to differentiate between a host of theories about what causes this heating.

For this, they turn to NASA’s Interface Region Imaging Spectrograph (IRIS) mission. IRIS was finely tuned with a high-resolution imager to zoom in on specific hard-to-see events on the Sun.

The visualization gives us a full view of the Sun before zooming into IRIS’s up-close view of the nanojets, which briefly light up in the magnetic loops.

IRIS accumulates its high-resolution pictures by zeroing in on a small portion of the Sun at once. Observing specific events is a combination of educated guesswork and taking a gander at the perfect spot at the perfect time.

Once the nanojets were identified against the backdrop of the coronal rain, researchers coordinated with NASA’s Solar Dynamics Observatory (SDO) and the Hinode observatory, a partnership among the Japan Aerospace Exploration Agency, ESA (European Space Agency), and NASA to get a complete view of the Sun, and confirm whether they were detecting nanojets, and assess their effects on the corona.

The researchers combined the many observations with advanced simulations to recreate the events they saw on the Sun. The models showed that the nanojets were a telltale signature of magnetic reconnection and nanoflares, contributing to coronal heating in the simulations.

Further studies are required to establish the frequency of nanojets and nanoflares all over the Sun, and how much energy they contribute to heating the solar corona.

Journal Reference:
  1. Antolin, P., Pagano, P., Testa, P. et al. Reconnection nanojets in the solar corona. Nat Astron (2020). DOI: 10.1038/s41550-020-1199-8

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