H-CMEs and solar wind plasma disturbances in relation to intense geomagnetic storms during the period of 2014-2017

We have studied intense geomagnetic storms magnitude (≤-100nT) observed between 2014 and 2017 with coronal mass ejections, hard X-ray solar flaresand disturbances in solar wind plasma parameters. We have observed that majority of the of intense geomagnetic storms, associated Hard X-Ray solar flares. It is observed that all the intense geomagnetic storms are Hard X-Ray solar flares of different categories. The association rates X-Class, M-Class, C-Class and B-Class X-ray solar flare are:X-Class -9.0%, M-Class-54.54%, C-Class -18.18%, B-Class -18.18% respectively. Intense geomagnetic storms which are associated with halo and partial halo coronal mass ejection (CMEs) are related to hard X-ray solar flares of different categories. It is also observed that these intense geomagnetic are associated with disturbances in solar wind plasma parameters. Positive correlation with correlation coefficient 0.71 has been found between the magnitude of intense geomagnetic storms and the peak value of associated disturbances in interplanetary magnetic fields (IMFB), 0.49between the magnitude of intense geomagnetic storms and the peak value of associated disturbances in southward component in interplanetary magnetic fields (IMF Bz), 0.79between the magnitude of intense geomagnetic storms and the peak value of associated disturbances in solar wind plasma pressure (SWP) . We have concluded that coronal mass ejections associated with hard X-ray solar flare are mainly responsible to cause intense geomagnetic storms.


Introduction
The geo-spheric atmosphere is highly exaggerated by the solar active regions accompanying solar features and interplanetary parameters such as solar flare (SFs), active prominences disappearing filaments (APDFs), coronal holes, coronal mass ejections (CMEs), radio bursts, interplanetary shocks and turbulences in solar wind plasma parameters. The active regions and related major classes of solar activity tend to track the sunspot number during the cycle, including-radio burst, calcium plages, solar flares, filaments, and coronal mass ejections (CMEs) (Webb and Howard (1994). This activity is transmitted to earth through the solar corona and its expansion into the heliosphere as the solar wind. Among all these solar features radio bursts, solar flares, and coronal mass ejections are the most energetic solar events in the heliosphere and are widely recognized as being responsible for the production of large disturbances in the solar wind, transient interplanetary shocks, and geomagnetic disturbances in geomagnetic field of the magnetosphere. From the result of the investigation, it has now been clear that geomagnetic perturbations in the magnetosphere are produced by helio-spheric magnetic fields and solar wind plasma streams related to the active regions, disappearing filaments and prominences, solar flares, evolving active regions, and coronal holes (CH), helio-spheric current sheet, (HCS). It is generally believed that long intervals of enhanced southward interplanetary magnetic field (IMF) and the high solar wind speed are the primary causes of intense geomagnetic disturbances in the geomagnetic field of the magnetosphere and that the solar sources of such geoeffective solar wind structures are usually CMEs (Webb et al. 2001). However, not all Earth-directed CMEs can produce geomagnetic storms in the magnetosphere. The properties of the earth-directed CMEs, such as the internal structure of the magnetic field, may determine whether or not a geomagnetic storm subsequently occurs (Burton et al. 1975, Cane et al.2000. From the results of the past three decades, it is confirmed that CMEs are large-scale magnetized plasma structures originating from closed magnetic field regions the sun: active regions, filament regions, active region complexes, and trans equatorial interconnecting regions ) and drive solar wind (SW) disturbances in terms of the magnetic field, speed and density, which in turn cause magnetic disturbance in the magnetosphere (Zhang, et al 2003). It has been established by now that geomagnetic storms occur when the southward component of interplanetary magnetic field eld (IMF), Bz, impinges upon the Earth's magnetosphere and reconnects (Gopalswamy, 2002). Several statistical observational studies have been done to investigate the properties of solar flares and/or CMEs. By focusing on flare occurrence, Bobra & Couvidat (2015) showed that a few parameters (total unsigned current helicity, total magnitude of Lorentz force, and total photo-spheric magnetic free energy density) are more relevant to the occurrence of solar flares than other parameters (mean photo-spheric magnetic free energy and mean current helicity). Zhang & Liu (2015) indicated that the rise time of the soft-X-ray flux of a flare is approximately half of the decay time, and the rise and decay times increase with variations in the peak flux of the soft X-ray. Regarding CMEs,  investigated the frequency distributions in the energy of solar flares and found that the power law indices of the frequency distributions for flares without CMEs are steeper than those for flares with CMEs. According to Toriumi et al. (2017), if the area of flare ribbons normalized by the sunspot area is large, solar flares tend to be accompanied by CMEs. Another important observational characteristic of solar flares is the shape of the magnetic field lines in the corona. Since the plasmas in the corona are frozen to the magnetic field lines, the loop-like structure, which can be seen through soft X-ray or extreme ultraviolet (EUV) observations, reflects the structure of the magnetic field lines. Verma et al, (2009) have studied geomagnetic storms Dst < -50nT observed during the period of 1997-2006, with halo and partial halo coronal mass ejections associated with X-ray solar flares of different categories and concluded that they have concluded that majority of the observed geomagnetic storms are found that halo and partial halo CMEs associated with X ray solar flares are most potential candidates for production of geomagnetic storms. Michalek, G.et al (2006) have concluded that halo coronal mass ejections (HCMEs) originating from regions close to the centre of the sun are likely to be geoeffective. They have showed that, only fast halo CMEs (with space velocities higher than ~1000 km/s) and originating from the Western Hemisphere close to the solar centre could cause intense geomagnetic storms. Gopalswamy (2009) has studied the role of halo and partial halo CMEs in producing geomagnetic storms. He has reviewed the results obtained by previous investigators and concluded that the generation of geomagnetic storms rates can be readily explained by the different definition of halo CMEs used by different authors. Partial halos are less energetic and generally originate far from the disk centre, so most of them behave similar to the non-geo-effective CMEs and hence most of the partial halo CMEs may not produce geomagnetic storms. He has inferred that halo CMEs originating close to the disk centre or very much effective in producing geomagnetic storms. Since coronal plasmas are heated to 10-20 MK during solar flares, the characteristics of solar flares are often identified through X-ray observations (e.g., Benz 2017 and references therein). The magnitude of a solar flare is usually defined by the peak flux of the soft-X-ray measured by the Geostationary Operational Environmental Satellite (GOES) and classified into several classes (A, B, C, M, and X). In this investigation, we have studied intense geomagnetic storms magnitude (≤-100nT) observed between 2014 and 2017 with coronal mass ejections, hard X-ray solar flares and disturbances in solar wind plasma parameters. In this study, we use the linear CME speeds to further explore their geomagnetic activity. One obvious reason to use this parameter is that fast CMEs are very often associated with strong geomagnetic storms (Gopalswamy, 2010). This paper is organized as follows. The observations and data selection are described in Section 2, and the analysis is explained in Section 3. Section 4 presents the results and final conclusion in Section 5.

Data Selection and Observations
Table1-Instance geo-magnetic storms and associated disturbances in solar wind plasma parameters for the period of 2014-2017. In table 1 investigation of hourly Dst indices of geomagnetic field have been used over the period 2014 through 2017 to determine onset time, maximum depression time, the magnitude of intense geomagnetic storms. This data has been taken from the NSSDC Omni web data system (http;//omniweb.gsfc.nasa.gov/form/dxi.html)). Which has been created in late 1994 for enhanced access to the near-earth solar wind, magnetic field, and plasma data of Omni data set, which consists of one-hour resolution near the earth, solar wind magnetic field and plasma data, energetic proton fluxes and geomagnetic and solar activity indices? To determine disturbances in solar wind plasma parameters, hourly data of solar wind plasma pressure and interplanetary magnetic field, the southward component of interplanetary magnetic fields has been used and these data have also been taken from Omni web data (http;//omniweb.gsfc.nasa.gov/form/dxi.html).

Analysis
This study uses statistical method association and correlation for data analysis of the observed intense geomagnetic storms with disturbances in solar wind plasma parameters. Statistical method correlation has been used to see how the magnitude of intense geomagnetic storms is correlated with disturbances in solar wind plasma parameters. Table and Figure 1,2 it is observed that all the intense geomagnetic storms are associated with disturbances in the southward component of interplanetary magnetic fields (IMF Bz) with lowest peak value -11.2 nT to highest peak value -26.3 nT and lowest magnitude -5.4 nT to highest magnitude -23.5 nT. Most of the intense geomagnetic storms of higher magnitudes are associated with relatively higher peak value disturbances in IMF Bz. The trend line of scatter plot between the magnitude of intense geomagnetic storms and the peak value of IMF Bz given in Figure 1 and magnitude of intense geomagnetic storms and magnitude of disturbances in IMF Bz given in Figure 2 shows a strong positive correlation. A large positive correlation with correlation coefficient 0.49 between peak values of disturbances in IMF Bz and magnitude of intense geomagnetic storms and between the magnitude of disturbances in IMF Bz and magnitude of intense geomagnetic storms have been obtained by statistical methods. Figure 3 shows that all the intense geomagnetic storms are associated with disturbances in interplanetary magnetic fields (IMFB) with the lowest peak value 13.9 nT, and highest peak value 31.5nT and lowest magnitude 11.5 nT and highest magnitude 23.7 nT. It is also seen that the disturbances in IMFB following the onset time of intense geomagnetic storms. The trend line of the scatter plot between the magnitude of intense geomagnetic storms and the peak value of IMFB ( Figure 3) and magnitude of intense geomagnetic storms and magnitude of disturbances in IMFB given in Figure 3 shows a strong positive correlation. positive correlation with correlation coefficient 0. 71 has been determined between magnitude of intense geomagnetic storms peak value of associated disturbances in interplanetary magnetic fields (IMFB) and magnitude of intense geomagnetic storms have been by statistical methods. 3-From the data analysis of intense geomagnetic storms and associated disturbances in solar wind plasma pressure observed during the period of 2014-2017. In figure 4 it is determined that all the all the intense geomagnetic storms are associated with disturbances in solar wind plasma pressure. Positive correlation with correlation coefficient 0.79has been determined between magnitude of intense geomagnetic storms peak value of associated disturbances in solar wind plasma pressure.

Results
Our analysis showed that all analyzed data sets have significant relationships with each other. This study based on the comparison of instance geomagnetic storms magnitude (≤-100nT) observed between 2014 and 2017 with coronal mass ejections (CMEs), hard X-ray solar flares and disturbances in solar wind plasma parameters (IMFB, IMF Bz).We summarize the main findings of this study as follows: We have observed that the data analysis of intense geomagnetic storms, associated Hard X-Ray solar flares in figure 5. It is observed that all the intense geomagnetic storms are Hard X-Ray solar flares of different categories. The association rates X-Class, M-Class, C-Class and B-Class X-ray solar flare are: X-Class -9.0%, M-Class-54.54%, C-Class -18.18%, B-Class -18.18% respectively. Intense geomagnetic storms which are associated with halo and partial halo coronal mass ejection (CMEs) are related to hard X-ray solar flares of different categories. Further it is also observed that these intense geomagnetic are associated with disturbances in solar wind plasma parameters. Positive correlation with correlation coefficient 0.71 has been found between the magnitude of intense geomagnetic storms and the peak value of associated disturbances in interplanetary magnetic fields (IMFB). Positive correlation with correlation 0.49 has been determined between the magnitude of intense geomagnetic storms and the peak value of associated disturbances in southward component in interplanetary magnetic fields (IMF Bz). Positive correlation with correlation 0.79 has been determined between the magnitude of intense geomagnetic storms and the peak value of associated disturbances in solar wind plasma pressure (SWP).

Conclusions
We performed statistical analyses to compare the dependence among the parameters of solar flares existence, flare class, duration, decay time, rise time, CME speeds, and CME type, based on two analyses: linear-correlation analysis method and graphical representation method. Our statistical analysis concluded that coronal mass ejections (CMEs) associated with hard X-ray solar flares are mainly responsible to generate intense geomagnetic storms.

Conflict of Interest
In this manuscript the authors declare that there is no conflict of interest.