Ch. Katsavrias

Wavelet Analysis on Solar Wind Parameters and Geomagnetic Indices

The geomagnetic activity is the result of the solar wind–magnetosphere interaction. It varies following the basic 11-year solar cycle; yet shorter time-scale variations appear intermittently. We study the quasi-periodic behavior of the characteristics of solar wind (speed, temperature, pressure, density) and the interplanetary magnetic field (Bx, By, Bz, β, Alfvén Mach number) and the variations of the geomagnetic activity indices (DST, AE, Ap and Kp). In the analysis of the corresponding 14 time series, which span four solar cycles (1966 – 2010), we use both a wavelet expansion and the Lomb/Scargle periodograms. Our results verify intermittent periodicities in our time-series data, which correspond to already known solar activity variations on timescales shorter than the sunspot cycle; some of these are shared between the solar wind parameters and geomagnetic indices.

THE MAJOR GEOEFFECTIVE SOLAR ERUPTIONS OF 2012 MARCH 7: COMPREHENSIVE SUN-TO-EARTH ANALYSIS

During the interval 2012 March 7–11 the geospace experienced a barrage of intense space weather phenomena including the second largest geomagnetic storm of solar cycle 24 so far. Significant ultra-low-frequency wave enhancements and relativistic-electron dropouts in the radiation belts, as well as strong energetic-electron injection events in the magnetosphere were observed. These phenomena were ultimately associated with two ultra-fast (>2000 km s) coronal mass ejections (CMEs), linked to two X-class flares launched on early 2012 March 7. Given that both powerful events originated from solar active region NOAA 11429 and their onsets were separated by less than an hour, the analysis of the two events and the determination of solar causes and geospace effects are rather challenging. Using satellite data from a flotilla of solar, heliospheric and magnetospheric missions a synergistic Sun-to-Earth study of diverse observational solar, interplanetary and magnetospheric data sets was performed. It was found that only the second CME was Earth-directed. Using a novel method, we estimated its near-Sun magnetic field at 13 Re to be in the range [0.01, 0.16] G. Steep radial fall-offs of the near-Sun CME magnetic field are required to match the magnetic fields of the corresponding interplanetary CME (ICME) at 1 AU. Perturbed upstream solar-wind conditions, as resulting from the shock associated with the Earth-directed CME, offer a decent description of its kinematics. The magnetospheric compression caused by the arrival at 1 AU of the shock associated with the ICME was a key factor for radiation-belt dynamics.

Nonstorm loss of relativistic electrons in the outer radiation belt

We report observations of electron Phase Space Density (PSD) dropout and evidence that supports the loss mechanism of magnetopause shadowing and outward radial diffusion during a nonstorm period characterized by persistently positive values of the SYM-H index. On 14 April 2013 an electron PSD dropout of 2 orders of magnitude was observed at the nightside magnetosphere by the Van Allen Probes. The magnetopause shadowing was associated with a strong pulse attributed to the arrival of an interplanetary coronal mass ejection. It is shown, for the first time in detail, that significant losses to the magnetosheath may occur even in the absence of significant reconnection and magnetic storm activity. Signatures of substorm injections that penetrate the outer belt and enhance the low-energy electrons were also observed right after the interplanetary pressure pulse. Moreover, particle measurements from THEMIS constellation also show a PSD depletion in the dayside magnetosphere.

The Effect of Helio‐Geomagnetic Activity on the Proceedings in the Emergency Department of Two Greek Hospitals

Study of the solar and geomagnetic activity influence on the emergency proceedings in Greece, for selected months of solar cycle 23 and especially for the year 2005 is presented. We examined the time association between the magnetic storms (Dst geomagnetic index), daily numbers of solar flares and Coronal Mass Ejections (CMEs) with the emergency proceedings. The sample of about 30000 cases from two Greek hospitals (The General Hospital of the town of Lamia and The General Hospital of the town of Veria) analyzed according to diagnoses. The cardiological, neurological, accidents (multitrauma and burns) and oncological patients as well as in partially pathological/surgical patients showed an increase during periods of high helio‐geomagnetic activity. In order to strengthen this result, more data need to be collected and analyzed.

Helio‐Geomagnetic Activity and the Time Distribution of Myocardial Infractions during the Solar Cycle 23 (1997–2007). A Preliminary Study based on a Greek Hospital Data

We present the time distribution of a large number (7798) of Myocardial Infractions (MI) recorded at the General Hospital ‘St. Panteleimon’ of the city of Nikea (in Piraeus, Greece), during time interval 1997–2007. This data set consisted of 5160 NON‐STEACS (non‐ST) and 2638 STEACS (ST) infractions are examined along with the monthly numbers of solar flares and Coronal Mass Ejections (CMEs), solar wind parameters and the geomagnetic activity (Dst geomagnetic index and other). The mean monthly value of ST and non‐ST events is 20 and 40 respectively. The maximum monthly value of non‐ST events (72 and 73) are recorded in October 2002 and January 2003, as well as the one of ST events (32), while solar maximum, recorded in November 2002. This time interval is characterized by magnetic storms from August 2002 peaked in October 2002 and ended in February 2003. It is noticeable that August 2002 corresponds to the solar maximum of CMEs and strong solar flares monthly values. The maximum monthly value of ST events ...

Study Of The Solar Wind Parameters During The 23rd Solar Cycle

In this paper we study the solar wind parameters during the 23rd solar cycle and the possible correlation between them. Those parameters’ data, which are Alfven Mach number, plasma beta, flow speed, proton density and temperature, dynamic pressure, average magnetic field, Bx and By, has been taken from OMNI 2. The first part of this project is about analysis and correlation of the data, using Pearson’s product moment correlation coefficient and Spearman Rank Correlation Coefficient, during the 11 years of the 23rd cycle. The second part is about Wavelet analysis on those parameters during the 21st, 22nd, 23rd solar cycles in comparison with them. We found that each parameter has different behavior in every cycle and certain periodicities that appear constantly.