What mechanisms do astronomers believe is responsible for making the Sun's outer atmosphere so much hotter than its photosphere?

magneto hydrodynamic( MHD) waves

Explanation:

The surface of the Sun transmits magneto hydrodynamic( MHD) waves to its atmosphere. These waves carry energy from the sun's surface to its atmosphere ( Corona) and heat up the atmosphere to such extent that its temperature rises to many time than that of the surface temperature of the Sun.

where’s the list ? the question is incomplete

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =