New datasets from

South American equatorial magnetic observatories

Soares, G. B. (1), Matzka, J. (2), Lilienkamp, H. (2,3),

Rosales, D. (4) and Pinheiro, K. (1)

(1) Geophysics Department, Observatório

Nacional, 20921-400 Rio de Janeiro, Brazil. (2) GFZ German Research

Centre for Geosciences, 14473 Potsdam, Germany. (3) Institute of Earth

and Environmental Sciences, University of Potsdam, Germany. (4)

Instituto Geofísico Del Perú, Huancayo Geomagnetic Observatory,



Here we describe two geomagnetic time series

from the South American magnetic observatories Huancayo (HUA, Peru)

and Tatuoca (TTB, Brazil) that are affected by both the equatorial

electrojet (due to their proximity to the magnetic equator) and the

South Atlantic Magnetic Anomaly. We have filled in gaps and removed

errors in the hourly values from HUA for 1922 to 2001 and we recovered

and calibrated minute mean data from TTB for 2008 to 2016.

The HUA dataset consists of horizontal, declination and vertical

components (H, D and Z) hourly mean values, obtained from two

different sources: the World Data Center (WDC) Kyoto and recently

digitized handwritten tables (DHT) with data that were previously

unavailable. The DHT data fills considerable gaps in the WDC data for

the 1960ies, 1970ies and 1980ies. These two subsets partially overlap

in the 1960ies. Here, we provide a final combined WDC-DHT dataset for

HUA from 1922 (installation of HUA) to 2001, as HUA became a member of

INTERMAGNET (International Real-time Magnetic Observatory Network) in

2002. We have processed all three components of WDC and DHT data,

correcting typos, spikes and jumps and combined them into one dataset.

Furthermore, we also describe the DHT digitisation process and our

criteria to decide between the WDC and DHT sets in the overlap


While HUA is an equatorial magnetic station since its installation,

TTB only became an equatorial station in the last decade. This is due

to the strong secular variation of the vertical component in the

Brazilian sector that leads to a significant movement of the magnetic

equator. Thus, only part of TTB 61 years time series (installed in

1957) is a record of the equatorial electrojet. Here we present the

2008-2016 dataset, as the magnetic equator crossed TTB location in

March 2013. This dataset contains calibrated minute means and derived

hourly mean values of X, Y and Z components. We will report the steps

and criteria adopted during the data processing, and present two

different data subsets according to the observed noise level.

Our motivation for this work is to provide the data to WDC for

Geomagnetism (Edinburgh) and to GFZ Data Service.