Looking for definitions

stunner5000pt

(not sure if this is the appropriate forum)
of astronomical terms
for our 'physics of the space environment' class we do not have a textbook... as such looking definitions is hard because we have to formulate or own from teh notes and it may be wrong...

ANyway i was wondering if these definition were correct
the italics denote that i am not sure about them

Explain what it is meant, using equations where appropirate

Sunspot number - a quantity that measures the number and size of sunspots on the sun

photodetachment - ejection of electron from a negative ion upon photoexcitiation.

Chromosphere - Thin layer of solar atmosphere just above the photosphere 10,000 km deep and below the corona. The temperature increases from 6000 C at the bottom to 20 000 C at the the top.

Interplanetary magnetic Field - Solar magnetic field embedded in solar wind and considered to be frozen in by virtue of the highly conductive solar wind plasma. It extends throughout the solar system and is thus interplanetary

Jean's Criterion - A relatively dense cloud will collapse if its own thermal energy does not balance its own gravitaitional potential energy

Optical Depth - measure of the transparency defined as a fraction of radiation that is scattered between a point and observer. (Do i have to state its insignificance in the beer lambert law?)