DEPARTMENT 4 : Solar Physics
EIT - Extreme Ultraviolet Imaging Telescope
We are co-investigator for the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliographic Observatory (SoHO).
Special observing campaigns, within the so-called ‘High cadence synoptic EIT program” are lead by the ROB to monitor the coronal heating at work.
Indeed, since the launch of SOHO, valuable observations have been acquired by the EIT telescope with which the two heating mechanisms have been confronted.
The solar atmosphere has puzzled scientists for more than 50 years with its surprisingly high temperature, on the order of a thousand times hotter than the solar surface!
The solar atmosphere is also a very dynamical environment where variations occur on a wide range of spatial and temporal scales.
These dynamics are important for understanding the heating of the solar atmosphere. There are three aspects to this problem:
- Where does the energy needed for heating come from?
- How is this energy transported from the photosphere to the corona?
- And once arrived in the corona, how is it released?
Two popular mechanisms are wave heating and nanoflare heating, which are both investigated in the Department of Solar Physics at the Royal Observatory of Belgium (ROB).
Wave heating
EIT has discovered clear signatures of waves in the corona, which supports the wave heating mechanism.
In the corona several types of waves exist, which combine the effect of the plasma and
the strong magnetic field.
Coronal Moreton or EIT waves are an example of fast magnetosonic waves.
These large wave pulses travel across the whole corona and are associated with flares and coronal mass ejections.
Nanoflare heating
Flares are the most violent manifestations of solar activity, releasing in only a few minutes huge amounts of energy over the entire electromagnetic spectrum.
The most energetic flares, however, are just the tip of the iceberg and progressively more flarelike events are observed for smaller energy releases.
This has lead to the suggestion that perhaps the bulk of the energy required to heat the solar corona is delivered collectively by yet unresolved small flares.
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