9th National Level Science Symposium. February 14, 2016
Organized by Christ College, Rajkot
SPACE WEATHER EVENTS WITH HALO CORONAL MASS EJECTION IN 23RD AND 24TH SOLAR CYCLE
Kunjal Dave 1, Miral Bhatt 2, R. M. Jadhav 3*
1,2
Research Scholar, C. U. Shah University, Wadhwan, Surendranagar, 363030, Gujarat
Assistant Professor, Gujarat College of Arts and Science College, Ahmedabad, 380006, Gujarat
*Corresponding author: shivswaraj@gmail.com
3
ABSTRACT: The effects of solar storms like solar flare, coronal mass ejection (CME), solar
bursts etc. have been found to have major effects in recent decades, on terrestrial magnetic field.
The earth’s magnetosphere is affected by halo coronal mass ejection in various ways one such
way has been disturbing satellite electronics besides effects on technological society. We report
the properties of halo coronal mass ejection observed by CDAW Data Center Solar Physics
Laboratory (Code 671) Heliophysics Science Division NASA / Goddard Space Flight Center
Greenbelt Maryland USA. Comparison between solar events occurred in last two (23rd and 24th)
solar cycles is done to understand solar terrestrial relations. Various spacecraft data for solar
events, interplanetary medium are used and ground based magnetic field measurements were
used to correlate. Some conclusions from the study are presented here. Several correlation
studies have been done in this study which includes plotting CME linear speed, ambient solar
wind speed, sunspot number etc vs. Magnetic storm index. The study suggests that for a big
magnetic storm (less than 100 nT) to occur very high initial linear speed is not necessary
however reasonably high speed is required. Ambient solar wind speed is also an important
parameter.
Keywords: Coronal Mass Ejection, Dst index, geomagnetic storms
1. INTRODUCTION
Coronal mass ejections (CMEs) are found to be the primary source of transient interplanetary (IP) disturbances
such as magnetic clouds, ejecta and shock waves [1]. The CMEs originating on the solar disk and quickly expanding to a projected size larger than the occulting disk of coronagraphs are known as a halo CME because
they appears to surround the occulting disk (fully or partially) [2, 3]. In recent decades, effects of solar storms
like solar flare, coronal mass ejection (CME), solar bursts etc. have been found to have major effects on terrestrial magnetic field. In recent times, use of geostationary satellites has been increasing manifold in communication and other purposes. These satellites are placed in geostationary orbits where changes in magnetic field may
affect their operation. Such changes have been affecting humankind as well. In present times, use of communication satellite is abundant and study of events that may affect its working is important. Such study had been
done in various ways like theoretical modelling, statistical forecasting, real-time tracking of events etc is being
done to estimate possible effects and precautionary steps that may be taken to prevent damage. We report the
properties of halo coronal mass ejection observed by CDAW Data Center Solar physics Laboratory (Code 671)
Heliophysics Science Division NASA / Goddard Space Flight Center Greenbelt Maryland USA.
2. DATA ANALYSIS
Coronal Mass Ejection linear speed is obtained from Coronagraph images taken using LASCO/C2 onboard
SOHO spacecraft. It is derived from height vs time plot. We have taken only full halo CMEs which are earth
directed. This was done to ensure considering geo-effective CMEs. Magnetic storm is characterized by many
parameters however Dst is the most available and important parameter. Geomagnetic storms (Dst magnitude
<-50nT) occurred during year 1996 to 2013, we have classified geomagnetic storms with respect to their Dst
magnitude in four categories according to Loewe and Prolss [4,5], a geomagnetic storm can be weak (Dst >
-50nT), moderate (-100nT < Dst ≤ -50nT), intense (Dst ≤ -100nT), and severe (Dst ≤ -200 nT). So, we
took data from World data centre – 2 which provides Final as well as provisional data. It is a combination of
values taken at many ground station magnetometers across the world. Yearly Plot of Linear speed vs. Dst index
for last two solar cycles is plotted and shown in figure 1 below.
3. RESULTS AND DISCUSSION
We have plotted linear speed of Coronal Mass Ejection versus minimum Dst index occurrence in next 3-4 days.
The 11-year Solar Cycle has been studied for a very long time sunspot data is known to possibly data back to the
ancient Chinese astronomers however the sun-earth connection is relatively new [4].
9th National Level Science Symposium. February 14, 2016
Organized by Christ College, Rajkot
We have plotted this considering all CMEs in a year from 1996 onwards for solar cycle 23 and 24. The
graphs shows relatively high slope of the linear fit during solar minimum years (1996, 1997, 1998, 1999, 2001,
2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2013) fig 1 and 2. This means linear speeds were more
correlated with geomagnetic storms at the earth. However, when the solar activity started increasing the slope
found to be decreased indicating less correlation and during solar maximum (2000, 2002, 2012) the slope was
lowest fig 1 and 2. This would mean that even with high CME velocities, geomagnetic storms could not be produced for many cases. This would also mean that during high solar activity other parameters play bigger role in
producing storm at other.
4. CONCLUSION
There is less correlation between solar and terrestrial parameters during solar maximum. During solar minimum
years CME speed and Dst index are better correlated. There was a period when there was no correlation between
the two during transition period of solar minimum to maximum.
ACKNOWLEDGEMENT
I thank C U Shah University and Gujarat Arts and Science College for providing administrative and infrastructural
facilities for doing this work.
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