Abstract
The effect of solar flare, sudden commencement of magnetic storm and of the disturbances ring current on the equatorial electrojet in the Eastern Brazil region, where the ground magnetic declination is as large as \(20^{^{\circ }}\hbox {W}\) is studied based on geomagnetic data with one minute resolution from Bacabal during November–December 1990. It is shown that the mean diurnal vector of the horizontal field was aligned along \(2{^{\circ }}\hbox {E}\) of north at Huancayo and \(30{^{\circ }}\hbox {W}\) of north at Bacabal during the month of December 1990. Number of solar flares that occurred on 30 December 1990 indicated the direction of solar flare related \(\Delta H\) vector to be aligned along \(5{^{\circ }}\hbox {E}\) of north at Huancayo and \(28{^{\circ }}\hbox {W}\) of north at Bacabal. This is expected as the solar flare effects are due to the enhanced conductivity in the ionosphere. The SC at 2230 UT on 26 November 1990 produced a positive impulse in \(\Delta X\) and negative impulse in \(\Delta Y\) at Bacabal with \(\Delta H\) vector aligned along \(27{^{\circ }}\hbox {W}\) of north. At Huancayo the \(\Delta H\) vector associated with SC is aligned along \(8{^{\circ }}\hbox {E}\) of north, few degrees east to the alignment of the diurnal vector of H. The magnetic storm that followed the SC had a minimum Dst index of –150 nT. The corresponding storm time disturbance in \(\Delta X\) at Huancayo as well as at Bacabal were about –250 nT but \(\Delta Y\) at Bacabal was about +70 nT and very small at Huancayo, that give the alignment of the H vector due to ring current about \(16{^{\circ }}\hbox {W}\) of north at Bacabal and almost along N–S at Huancayo. Thus alignment of the \(\Delta H\) vector due to ring current at Bacabal is \(14{^{\circ }}\hbox {E}\) of the mean direction of \(\Delta H\) vector during December 1990. This is consistent with the direction of ring current dependent on the dipole declination at the ring current altitude which is about \(5{^{\circ }}\hbox {W}\) of north over Bacabal and the deviation of declination due to the ring current during disturbed period given by the angle (\(\psi \)-D).
Similar content being viewed by others
References
Araki T 1977 Global structure of geomagnetic sudden commencements; Planet Space Sci. 25 373–384.
Araki T, Keika K, Kamei T, Yang H and Alex S 2006 Nighttime enhancement of the amplitude of geomagnetic sudden commencements and its dependence on IMF Bz; Earth Planets Space 58 45–50.
Chandra H and Rastogi R G 1997 Geomagnetic storm effects on zonal and meridional equatorial electrojet currents;J. Geophys. Res. 102 11,611–11,617.
Chapman S 1919 The solar and lunar diurnal variation of earth’s magnetic field; Phil. Trans. Roy. Soc. London A 218 118p.
Chapman S 1961 Regular motions in the ionosphere: Electric and magnetic relationships; Bull. Am. Meteorol. Soc. 42 85–100.
Clauer C R, Alexeev I I, Balenkaya E S and Baker J B 2001 Special features of the September 24–27 1998 storm during high solar wind dynamic pressure and northward interplanetary magnetic field; J. Geophys. Res. 106 25,695–25,771.
Forbush S E and Casaverde M 1961 The equatorial electrojet in Peru; Carnegie Inst Washington, Publication No. 620.
Fukushima N 1966 Declination changes of SC, its local time and seasonal dependence at Kakioka, Japan; J. Geomagn. Geoelectr. 18 99–112.
James M E, Rastogi R G and Winch D E 2004 Magnetic disturbance effect on geomagnetic field at low latitudes; Indian J. Radio Space Phys. 33 88–94.
McNish A G 1937 Terrestrial magnetic and ionospheric effects associated with light chromospheric eruptions; Terr. Magn. Atmos. Electr. 42 109–129.
Matsushita S and Maeda H 1965 On the geomagnetic solar quiet daily variation field during the IGY; J. Geophys. Res. 70 2535–2558.
Olson W P 1970 Contributions of nonionospheric currents to the quiet daily magnetic variations at earth’s surface;J. Geophys. Res. 75 7244–7249.
Oshio M, Fukushima N and Nagata T 1967 Solar flare effects on geomagnetic field; Rep. Ionos. Space Res. Japan 21 77–114.
Parkinson W D 1971 An analysis of the geomagnetic diurnal variations during the International Geophysical Year; Gerlands Beitr. Geophysik Leipzig 80 199–232.
Riggoti A, Chanlaun F H, Trivedi N B and Padilha A L 1999 Characteristics of the equatorial electrojet determined from an array of magnetometers in N. N-E Brazil; Earth Planet Space 51 115–128.
Rastogi R G 2001a Solar flare effects in geomagnetic field at Indian stations – Part 1: Trivandrum, the center of equatorial electrojet; Indian J. Radio Space Phys. 30 1–6.
Rastogi R G 2001b Solar flare effects in geomagnetic field at Indian stations – Part II: Annamalainagar, near the edge of electrojet; Indian J. Radio Space Phys. 30 7–14.
Rastogi R G, Winch D E and James M E 2001 Longitudinal effects in geomagnetic disturbances at mid-latitudes; Earth Planet. Space 53 969–979.
Rastogi R G 2003 Effect of solar disturbances on the geomagnetic H, Y and Z fields in American equatorial electrojet stations 1. Solar flare effects; J. Indian Geophys. Union 7 43–51.
Rastogi R G and Trivedi N B 2009 Asymmetries in the equatorial electrojet around N–E Brazil sector; Ann. Geophys. 27 1233–1249.
Rastogi R G, Chandra H and Yumoto K 2010 Equatorial electrojet in East Brazil; J. Earth Syst. Sci. 119 497–505.
Rastogi R G, Chandra H, Rahul Shah,Trivedi N B and Fontes S L 2013 A comparison of equatorial electrojet in Peru and East Brazil; Open Atmos. Sci. J. 7 29–36.
Russel C T, Ginskey M and Patrinec S M 1994 Sudden impulses at low latitude stations: Steady state response for northward interplanetary magnetic field; J. Geophys. Res. 99 253–261.
Sarabhai V and Nair K N 1971 Morphology of the geomagnetic field variations and a study of the interplanetary magnetic field fluctuations in relation to the daily variation of the geomagnetic field at low latitudes; Cosmic Electrodyn. 2 3–21.
Acknowledgements
The solar flare data were downloaded from SPIDR website. Thanks are due to Physical Research Laboratory, Ahmedabad for facilities provided for the analysis. RGR was the recipient of the senior scientist grant from Indian National Science Academy, New Delhi. Thanks are also to Rahul Shah for technical assistance during the investigations.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Rastogi, R.G., Janardhan, P., Chandra, H. et al. Effect of solar flare on the equatorial electrojet in eastern Brazil region. J Earth Syst Sci 126, 51 (2017). https://doi.org/10.1007/s12040-017-0837-8
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/s12040-017-0837-8