12.1 Available Constants and Units

There are many constants and units available within FLASH3, see Table 12.1 and Table 12.2. Should the user wish to add additional constants or units to a particular setup, the routine PhysicalConstants_init should be overridden and the new constants added within the directory of the setup.

Table 12.1: Available Physical Constants

String Constant	Description
Newton	Gravitational constant G
speed of light	Speed of light
Planck	Planck's constant
electron charge	charge of an electron
electron mass	mass of an electron
proton mass	Mass of a proton
fine-structure	fine-structure constant
Avogadro	Avogadro's Mole Fraction
Boltzmann	Boltzmann's constant
ideal gas constant	ideal gas constant
Wien	Wien displacement law constant
Stefan-Boltzmann	Stefan-Boltzman constant
pi	Pi
e	e
Euler	Euler-Mascheroni constant

Table 12.2: Available Units for Conversion of Physical Constants

Base unit	String Constant	Value in CGS units	Description
length	cm	1.0	centimeter
time	s	1.0	second
temperature	K	1.0	degree Kelvin
mass	g	1.0	gram
charge	esu	1.0	ESU charge
length	m	1.0E2	meter
length	km	1.0E5	kilometer
length	pc	3.0856775807E18	parsec
length	kpc	3.0856775807E21	kiloparsec
length	Mpc	3.0856775807E24	megaparsec
length	Gpc	3.0856775807E27	gigaparsec
length	Rsun	6.96E10	solar radius
length	AU	1.49597870662E13	astronomical unit
time	yr	3.15569252E7	year
time	Myr	3.15569252E13	megayear
time	Gyr	3.15569252E16	gigayear
mass	kg	1.0E3	kilogram
mass	Msun	1.9889225E33	solar mass
mass	amu	1.660538782E-24	atomic mass unit
charge	C	2.99792458E9	Coulomb
Cosmology-friendly units using $H_0 = 100$ km/s/Mpc:
length	LFLY	3.0856775807E24	1 Mpc
time	TFLY	2.05759E17	$\frac{2}{3H_0}$
mass	MFLY	9.8847E45	5.23e12 Msun