Wavelet Spectral

Analysis of the ENIGMA Magnetometer Array Time Series and Solar Wind

Conditions around the Strongest Magnetic Storms of Solar Cycle


Boutsi, Z. (1,2), Balasis, G.


(1) Institute for

Astronomy, Astrophysics, Space Applications and Remote Sensing,

National Observatory of Athens, Greece, (2) Section of Astrophysics,

Astronomy and Mechanics, Department of Physics, National and

Kapodistrian University of Athens, Greece


Magnetic storms are undoubtedly among the

most important phenomena in space physics and also a central subject

of space weather. The HellENIc GeoMagnetic Array (ENIGMA) is a network

of 4 ground-based magnetometer stations in the areas of Thessaly,

Central Greece, Peloponnese and Crete in Greece that provides

measurements for the study of geomagnetic pulsations, resulting from

the solar wind - magnetosphere coupling. ENIGMA magnetometer array

enables effective remote sensing of geospace dynamics and the study of

space weather effects on the ground (i.e. Geomagnetically Induced

Currents - GIC). ENIGMA contributes data to SuperMAG, a worldwide

collaboration of organizations and national agencies that currently

operate approximately 500 ground-based magnetometers. Here we study

the Earth’s magnetic field time variations measured by ENIGMA for

2015, when the three strongest magnetic storms of solar cycle 24

occurred in March, June and December, along with the corresponding

solar wind parameters and geomagnetic activity indices. We apply

spectral analysis techniques based on wavelet transforms and calculate

the Hurst exponent of these time series. Our results show the

existence of two different patterns: (i) a pattern associated with the

intense magnetic storms, which is characterized by higher Hurst

values; (ii) a pattern associated with the quiet-time magnetosphere,

which is characterized by lower Hurst values.