The Initial Steps for Developing the South American K Index From the Embrace Magnetometer Network

Abstract

ABSTRACT. In this paper we present the first steps given towards the development of the South American K index (Ksa) based on the measurements made by the Embrace Magnetometer Network. We present: (a) a description of the magnetometer and of the network; (b) the procedure used to calibrate the network equipments; (c) the procedure to obtain each station K scale and its corresponding upper limits of ranges for the three-hour-range station K index (thereafter referred as K9 threshold); and (d) some particularities regarding the Quiet Day Curve (QDC) deviation and its long term variation.Keywords: space weather, magnetic index, magnetometer network, aeronomy. RESUMO.No presente artigo, apresentamos os primeiros passos realizados para desenvolvermos oíndice K sul-americano (Ksa) baseado nas medidas feitas pela rede Embrace de magnetômetros. Apresentamos (a) uma descrição do equipamento utilizado, bem como da rede de magnetômetros; (b) o procedimento adotado para calibrar todos os equipamentos individuais da rede; (c) o procedimento para se obter a escala K de cada estação magnética e o seu correspondente limite superior para oíndice K de três horas (doravante denominado limiar K9); e (d) algumas particularidades com respeitoà obtenção da curva do Dia Quieto (QDC) e suas variações de longos períodos.Palavras-chave: clima espacial,índice magnético, rede de magnetômetros, aeronomia.

The Embrace Magnetometer Network for South America: Network Description and Its Qualification

“…Thereafter, we take a mandatory procedure to submit all the magnetic equipment acquired to be part of the Embrace MagNet for a sensitivity matching process against the reference magnetometer. This procedure consists of the following: Burying the sensor of the new magnetometer close (2–3 m) apart to the sensor of the reference fluxgate magnetometer, applying no changes to the factory settings; Collecting data for three consecutive months with both equipment; Selecting the data collected during the five most magnetic quietest days of each month with paying attention that the three‐hourly Kp value never exceeds a value of 3 over the entire day; Averaging the data acquired during the selected 5 days to obtain the mean quiet day curve (QDC; the QDC should be representative for the period of acquisition, avoiding aliasing, outliers, and any other possible interference) as described by Denardini et al () for each geomagnetic component (i.e., H , D , and Z ) of each magnetometer individually; Performing a correlation analysis between the three QDC ( H , D , and Z ) of the reference magnetometer and the three corresponding QDC of the magnetometer under evaluation; Correcting the gain of the measurements of each individual magnetic component of the magnetometer under evaluation, based on the angular parameter derived from the estimated regression equation; Collecting data for one more month; and Repeating steps 3 to 6 to ensure an angular parameter derived from the estimated regression equation lies between 0.98 and 1.02 (i.e., a relative error lower than 2%). …”

“…Selecting the data collected during the five most magnetic quietest days of each month with paying attention that the three-hourly Kp value never exceeds a value of 3 over the entire day; 4. Averaging the data acquired during the selected 5 days to obtain the mean quiet day curve (QDC; the QDC should be representative for the period of acquisition, avoiding aliasing, outliers, and any other possible interference) as described by Denardini et al (2015) for each geomagnetic component (i.e., H, D, and Z) of each magnetometer individually; 5. Performing a correlation analysis between the three QDC (H, D, and Z) of the reference magnetometer and the three corresponding QDC of the magnetometer under evaluation; 6.…”

“…Accordingly, the Brazilian Study and Monitoring of Space Weather (Embrace) Program developed the Embrace Magnetometer Network (Embrace MagNet) to cover most of the eastern South American longitudinal sector (Denardini et al, ). This network fills the gap of magnetic measurements available online in this sector and aims to provide magnetic data to be used as an estimate of the regional disturbance level (Denardini et al, ) caused by the geomagnetic storms (Gonzalez et al, ) driven by the space weather effects, for example, by developing the South American K ( Ksa ) index. Besides, a long‐term scientific goal is to investigate the trends in the magnetic intensity of the South America Magnetic Anomaly and the implication of its presence in the deviation of the magnetic indices used to monitor the solar‐terrestrial relationship associated with space weather, in a framework similar to that proposed by Moro et al ().…”

The Embrace Magnetometer Network for South America: First Scientific Results

“…The third way of obtaining the variation of the H component, which is also suitable for space weather studies, is defining Δ H according to equation : in which t , k , and H ( t ) are the same as defined in equation , while N is the number of magnetic station comprised in the derivation is the daily variation of the horizontal component. QDC( t ) is the daily variation of the monthly averaged horizontal component, acquired during the five quietest days of the month (Denardini et al, ). This method will select the H component considering only external (solar wind) forcing once the local forcing (atmospheric or solar radiation) were removed by subtracting the QDC, which will be addressed in the next section.…”

Effect of a huge crustal conductivity anomaly on the H-component of geomagnetic variations recorded in central South America

“…Geomagnetic data are acquired by commercial fluxgate magnetometers with 1-s sampling rate (for details of magnetometer sensitivity and calibration procedures see Denardini et al 2015). The six stations chosen for this study are shown in Fig.…”