Exploring effects in tippers at island geomagnetic observatories due to realistic depth- and time-varying oceanic electrical conductivity

Earth, Planets and Space

Table 1 Information on the geomagnetic observatories used in this study

Code	Name	\(\text{lat}^{\text{GG}}\)	\(\text{lon}^{\text{GG}}\)	\(\text{lat}^{\text{GM}}\)	\(\text{lon}^{\text{GM}}\)	Time interval used for tippers’ estimation
API	Apia	\(-13.81\)	\(-171.78\)	\(-15.05\)	263.35	\(01/01/2016 - 31/12/2017\)
ASC	Ascension Island	\(-7.95\)	\(-14.38\)	\(-2.77\)	57.48	\(01/01/2014 - 31/12/2015\)
CKI	Cocos-Keeling Islands	\(-12.10\)	96.84	\(-21.56\)	168.92	\(01/01/2017 - 31/12/2018\)
GAN	Gan	0.69	73.15	\(-8.64\)	145.33	\(01/01/2016 - 31/12/2017\)
GUA	Guam	13.59	144.87	5.8	216.51	\(01/01/2017 - 31/12/2018\)
HON	Honolulu	20.32	\(-158\)	21.65	270.85	\(01/01/2015 - 31/12/2016\)
IPM	Easter Island	\(-27.2\)	\(-109.42\)	\(-19.17\)	325.61	\(01/01/2013 - 31/12/2015\)
PPT	Pamatai	\(-17.57\)	\(-149.58\)	\(-15.05\)	285.79	\(01/01/2015 - 31/12/2016\)
SHE	St. Helena*	\(-15.90\)	\(-5.75\)	11.78	64.24	\(01/01/2015 - 31/12/2015\)
SMA	Santa Maria/Azores*	36.99	\(-25.13\)	43.21	53.57	\(01/05/2018 - 31/09/2019\)
TDC	Tristan da Cunha	\(-37.07\)	\(-12.31\)	\(-31.70\)	54.76	\(01/01/2013 - 31/12/2014\)

From left to right: IAGA code, observatory name, geographic and geomagnetic latitude and longitude, and time interval used to estimate tippers. Observatories with an asterisk (*) are, as of date, not participating in INTERMAGNET and data are available from GFZ Potsdam. Geomagnetic coordinates were calculated using the IGRF-12 model, epoch 2015