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Bioelectromagnetism

 

magnetosphere (Southwood, 1974). IBI is the time in milliseconds between consecutive heartbeats. Total

power is a measure of all the HRV bands combined, and therefore is a measure of the overall HRV from

all physiological sources, although it is highly afected by the VLF power. Space weather and environ­

mental measures were obtained from three sources, comprising nine measures. Te solar wind speed,

Kp index, Ap index, number of sunspots, F10.7 index, and the geomagnetic polar cap index (PCN) were

downloaded from NASA Goddard Space Flight Center’s Space Physics Data Facility as part of the Omni

2 data set (Alabdulgader et al., 2018). Here, the F10.7 index is a “solar radio fux” at 10.7 cm (2,800 MHz)

(Tapping, 1987). Tat is a measure of the solar fux unit (sfu) frequency at a wavelength of 10.7 cm, near

the peak of the observed solar radio emission. F10.7 is ofen expressed in sfu (1 sfu = 10⁻²² W/m²Hz). It

represents a measure of difuse, nonradiative coronal plasma heating. It is an excellent indicator of over­

all solar activity levels and correlates well with solar UV emissions. GCR counts were downloaded from

Finland’s University of Oulu’s Sodankyla Geophysical Observatory’s website (Alabdulgader et al., 2018).

Power in the time-varying MF in two frequency bands, SR Power, 3.5–36 Hz and ULF power, 2 mHz to

3.5 Hz were obtained from a recording site located in Boulder Creek, California (Alabdulgader et al.,

2018).

In agreement with previous studies (Crooker et al., 1977; Richardson et al., 1996; Mathie and Mann,

2000), solar wind speed was highly correlated with Kp and Ap indexes, and ULF power was negatively

correlated with GCR counts. As expected, the solar radio fux (F10.7) was also highly correlated with the

number of sunspots. Te SR power was negatively and highly correlated with GCR counts. ULF power

was positively correlated with solar wind speed, Kp, Ap, and PCN indexes. Te correlations among the

HRV variables were as expected and in agreement with other studies with the exception of HF power,

where correlations to IBI, Total power, and VLF power were all higher than seen in individual 24-hour

recordings. Tus, this study revealed that these HRV measures were correlated with solar and geomag­

netic variables and daily autonomic nervous system activity responds to changes in geomagnetic and

solar activity during the period of normal undisturbed activity (Alabdulgader et al., 2018). An increase

in GCRs, solar radio fux, and SR power was all associated with increased HRV and parasympathetic

activity (Alabdulgader et al., 2018).

It is clear that a major driver of changes and disturbances in the GMF environment are the Sun and

solar wind (Crooker et al., 1977; McPherron, 2005). Consistent with these fndings, the solar wind speed

was highly correlated with Kp, Ap, and the PCN, all of which refect MF disturbances. It was also found

that ULF power, which is related to MF-line resonances, was positively correlated with solar wind speed,

and indices of feld disturbance were negatively correlated with GCR counts, which is consistent with

the well-known inverse action of solar and geomagnetic activity and GCR counts at the Earth’s surface

(Richardson et al., 1996).

Regarding HRV responses, IBIs have an inverted relationship to HR where larger IBIs equated to a

lower HR. HR and IBIs are an ideal indicator of changes in the relative balance between parasympa­

thetic and sympathetic activity and how the autonomic system responds and adapts to various types of

stressors or challenges (McCraty and Shafer, 2015). If an environmental variable is negatively correlated

with IBIs, it indicates that HR increases with increases in that variable, which suggests a physiological

stress reaction occurred. On the other hand, a positive correlation with IBIs indicates a lower HR. Tere

were robust positive correlations between IBIs and SRs, and to a lesser degree with GCRs.

Te positive correlation found between HF power and solar radio fux indicates an enhancement of

parasympathetic nervous system activity during the period of increased solar radio fux. Tis was of

particular interest because a previous study with 1,643 participants in 51 countries found that the solar

radio fux index was positively correlated with reduced fatigue, improved positive afect, and mental

clarity while increases in solar wind speed had the opposite efects (McCraty et al., 2012). Te potential

benefcial efects of the solar radio fux were also observed in several studies that looked at death rates

from various causes which found a strong and inverse relationship between the F10.7 and death rates

(Stoupel et al., 2006, 2011). Te solar radio fux may be an important mediator of the anticipatory reac­

tions observed by Tchijevsky (1971), which can occur several days before increases in the solar wind