Why is Suns atmosphere hotter than its surface? Solar nanoflares?

Why Suns atmosphere hotter surface Solar nanoflaresOne of the many puzzles of the Sun is why is the solar surface much colder than its out atmospheres?

The Suns surface is around 5000 degrees centigrade yet some of its out atmosphere layers can be over a million degrees.

Is Suns atmosphere hotter than its surface due to Solar nanoflares?

Solar nanoflares are going to be investigated by NASA's Nuclear Spectroscopic Telescope Array (Nustar) spacecraft.

Because of its very high sensitivity, Nustar could solve some long-standing puzzles, such as whether "nanoflares" exist.
These proposed smaller versions of the Sun's giant flares could help explain why its outer atmosphere is many times hotter than its surface - a decades-old question.
"Nustar will give us a unique look at the Sun, from the deepest to the highest parts of its atmosphere," said Prof Smith, a solar physicist at University of California, Santa Cruz.
Sun's sizzling X-rays photographed from space

Sun has relatively cold interior?

Sunspots on the surface of the sun, as deep as we can see into the sun, are not just black and dark, Sunspots are also 'cold' or cooler than its atmosphere. Sunspots are around 4000 degrees C.

Solar nanoflares, cold Sunspots and other puzzles about the Sun may or may not be answered by the Nustar mission. But although science will not expect many surprises it will be surprising if they do not get any.

Electric Universe theory debunked evidence?

The Electric Universe theory (EU theory) has one of its main ideas that the sun is electric and not nuclear. Science laughs at the idea and says that all evidence shows the sun is nuclear and not electric.

An electromagnetic sun may help explain why the Suns surface and interior on visual and experimental data (not theoretical models) is hotter on its outer layers than its inner layers.

Will the NASA's Nustar provide enough evidence to debunk the EU theory? Or is it just how you interpret the evidence?