| Abstract * |
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We present the observational properties of coronal mass ejection (CME) flux ropes near the Sun based on a set of 35 events from solar cycle 24 (2010 to 2017). We derived the CME flux rope properties using the Flux Rope from Eruption Data (FRED) technique (Gopalswamy et al 2018a; Gopalswamy et al 2018c). According to this technique, the geometrical properties are obtained from a flux-rope fit to CMEs and the magnetic properties from the reconnected flux in the source region. In addition, we use the magnetic flux in the dimming region at the eruption site. The geometric properties like radius of the flux rope and aspect ratio are derived from the flux rope fitting. We found that the mean values of the poloidal flux, toroidal flux, axial magnetic field strength and radius of the flux rope are 4.2×10 21 Mx, 7.3×10 20 Mx, 18.8 mG and 4.5 Rs respectively. The reconnected flux exhibits a positive correlation with flare fluence in soft X-rays, peak flare intensity in soft X-rays, CME speed and kinetic energy with correlation coefficients (cc) 0.78, 0.62, 0.48 and 0.54 respectively. We found a moderate positive correlation between magnetic flux in the core dimming regions and the toroidal flux obtained from the Lundquist solution for a force free flux rope (cc = 0.43). Further, we correlate the core dimming flux and CME mass (cc = 0.35). The area of core dimmed region shows a moderate correlation with the radius of the flux rope (cc = 0.4). Thus, we infer that a greater magnetic content (poloidal and toroidal fluxes) indicates a more energetic eruption. We found a good anti correlation between the poloidal and toroidal fluxes with the Dst index for the events associated with interplanetary CMES (ICMEs). We found that as poloidal and toroidal flux increases, Dst index of the geomagnetic storm decreases, suggesting important implications for space weather predictions. |
