The coupling process between solar wind-magnetosphere-ionosphere is an important physical 14 mechanism for the delineating concept of the magnetosphere-ionosphere system. In this work, we have studied the polar cap potential (PCV) and merging electric field (E m ) during three different supersubstorm (SSS) events. We have also studied the roles of polar cap index and auroral electrojet (AE) indices to observe polar cap activity during SSSs. To substantiate results, wavelet transform and cross-correlation techniques are used. We checked the cross correlation of PCV with AE, SYM-H, B z , X, Y, and E y individually. Positive good correlation of PCV with AE and SYM-H is obtained. Observing and obtaining these results, PCV shows the significant effects during geomagnetic activity (SSSs) generated by geoeffective solar wind parameters.

A dominant process by which energy and momentum are transported from the magnetosphere to the ionosphere is known as field‐aligned current (FAC). It is enhanced during magnetic reconnection and explosive energy release at a substorm. In this paper, we studied FAC, interplanetary electric field component (Ey), interplanetary magnetic field component (Bz), and northward (x) and eastward (y) components of geomagnetic field during three events of supersubstorm occurred on 24 November 2001, 21 January 2005, and 24 August 2005. Large‐scale FAC, supposed to be produced during supersubstorm (SSS), has potentiality to cause blackout on Earth. We examined temporal variations of the x and y components of high‐latitude geomagnetic field during SSS, which is attributed to the FACs. We shall report the characteristics of high‐latitude northward and eastward components of geomagnetic field variation during the growth phase of SSS by the implementation of discrete wavelet transform (DWT) and cross‐correlation analysis. Among three examples of SSS events, the highest peak value of FAC was estimated to be ~19 μAm−2. This is shore up with the prediction made by Parks (1991) and Stasiewicz et al. (1998) that the FACs may vary from a few tens to several hundred μAm−2. Although this peak value of FACs for SSS event is much higher than the average FACs associated with regular substorms or magnetic storms, it is expedient and can be expect for SSS events which might be due to very high density solar wind plasma parcels (PPs) triggering the SSS events. In all events, during growth phase, the FAC increases to extremely high level and the geomagnetic northward component decreases to extremely low level. This represents a strong positive correlation between FAC and geomagnetic northward component. The DWT analysis accounts that the highest amplitude of the wavelet coefficients indicates singularities present in FAC during SSS event. But the amplitude of squared wavelet coefficient is found to be different from each other, which might be due to the solar wind PPs of different density triggering the SSS events. The cross‐correlation analysis suggests that the perturbation on geomagnetic northward component at high latitude during SSS strongly correlates with the fluctuation pattern of FAC density. Hence, the FAC is the primary sources for the eastward‐westward magnetic field perturbations at high latitude.

<p>The polar cap potential (PCV) has long been considered as a key parameter for describing the state of the magnetosphere/ionosphere system. The relationship between the solar wind parameters and the PCV is important to understand the coupling process between solar wind-magnetosphere-ionosphere. In this work, we have estimated PCV and merging electric field (Em) during two different high intensity long duration continuous auroral activity (HILDCAA) events. For each event, we examine the solar wind parameters, magnitude of interplanetary magnetic field (IMF), interplanetary electric field (IEF), PCV, Em and geomagnetic indices (i.e., SYM-H, geomagnetic auroral electrojet (AE) index, polar cap index (PCI) and auroral electrojet index lower (AL), respectively). We also study the role of PCI and AL indices to monitor polar cap (PC) activity during HILDCAAs. In order to verify their role, we use wavelet transform and cross-correlation techniques. For the three events studied here, the results obtained from continuous wavelet transform (CWT) and discrete wavelet transform (DWT) are different, however the effect of HILDCAA can be easily identified. We also observe the cross-correlation of PCI and PCV with AL, SYM-H, Bz component of the IMF and Ey component of the IEF individually. Both PCI and PCV show very good correlation with AL and SYM-H indices during the events. Observing these results, it can be suggested that PCI and AL indices play a significant role to monitor geomagnetic activity generated by geoeffective solar wind parameters.</p><p>Journal of Nepal Physical Society Vol.3(1) 2015: 6-17</p>

Polar cap potential (PCV) is an important parameter used for determining what kind of interaction takes place between solar wind and magnetosphere. Highly energetic particles from Sun driven by solar wind constantly bombard with Earth's magnetosphere–ionosphere system that results into a phenomenon like auroras, and major geomagnetic disturbances. Solar wind electron deposition determines the magnitude of field‐aligned current (FAC) and ultimately leads to PCV variation. Several studies found that increase in magnitude of IMF‐Bz causes an electric field of cross magnetosphere to increase, and it leads to increase in magnitude of ionospheric cross‐polar cap potential (PCV). Moreover, PCV was found to be a linear function of Vsw. In this research, we aim to study how field‐aligned current (FAC), for example, region 1 current and PCV, is related during different forms of geomagnetic disturbances. In all events, FAC and PCV are found to have corresponding fluctuations—especially at times of significant variation of IMF‐Bz (negative Bz interval) following the linearity of equation suggested by Moon in Moon (2012, https://doi.org/10.5140/JASS.2012.29.3.259). We found one‐to‐one correspondence between FAC and PCV. We did CWT analysis and found that FAC and PCV have more or less same spectral behaviors for each event considered. The cross‐correlation analysis shows a high and positive correlation between FAC and PCV at 0‐min time lag for all geomagnetic activity. The CWT analysis clearly supports the result of cross correlation between FAC and PCV. We found that FAC and Vsw, FAC‐B, and FAC and AE are also positively correlated with high‐correlation coefficient at lag 0 min for all geomagnetic storm. However, FAC‐Bz, FAC‐By, and FAC‐SYM (H) have varying correlation in different events. For a particular storm and substorm, the parameters Bz and By may not necessarily be varied with FAC in regular sequence but IMF (B) always show positive correlation with FAC for all geomagnetic activity. This paper presents a clear relation between FAC and PCV. This result will help to identify some of the outstanding issues in determining the causal mechanism of PCV variation, a crucial thing to understanding the coupling between the solar wind and M‐I system.

Solar eclipse is a phenomenon that has a direct influence on the Earth's ionosphere • The measure of the decrease in vertical value of total electron content during the eclipse hours are correlated with the partial and complete obscuration of solar radiation • The scale of the reduction is closely associated with the eclipse magnitude