ANS	Autonomic nervous system
EEG	Electroencephalogram
HRV	Heart rate variability
HF	High frequency
LF	low frequency
LF/HF ratio	low frequency divided by high frequency power
VLF	very low frequency
SNDNi	SDNN index
TP	Total power
IBI	Inter-beat-interval
ULF	Ultra low frequency
Environmental related measures
Pc	pulsations continuous
Pi	pulsations irregular
SR	Schumann resonance
SRP	Schumann resonance power
SWS	Solar wind speed
PC(N)	index polar cap north
CR	Cosmic rays
TMFV	Total magnetic field variance
CME	coronal mass ejection