Browsing by Author "Janardhan, P."

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    Solar wind flow angle and geoeffectiveness of corotating interaction regions: First results
    (American Geophysical Union, 2017-05-04) Rout, Diptiranjan; Chakrabarty, D.; Janardhan, P.; Sekar, R.; Maniya, Vrunda; Pandey, Kuldeep
    A total of 43 Corotating Interaction Region (CIR)‐induced geomagnetic storms during the unusually deep solar minimum of solar cycle 23 (2006–2010) were identified using a superposed epoch analysis technique. Of these 43 events, detailed cross‐spectrum analyses, between the variations in the Z component of the interplanetary magnetic field (IMF Bz) and the equatorial electrojet (EEJ) strength, were performed for 22 events when the daytime EEJ strengths from Jicamarca were available. The analyses revealed that the ∼30 and ∼60 min periodic components in IMF Bz were causally related to the EEJ strength subject to the average solar wind flow being radial to within 6° at L1 during the interval for which EEJ strengths were considered. This investigation elicits the important role of average solar wind azimuthal flow angle in determining the geoeffectiveness of CIR events.
    Palabras clave:Corotating interaction regionGeoeffectiveness of CIRSolar wind flow angle
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    Spread-F during the magnetic storm of 22 January 2004 at low latitudes: Effect of IMF-Bz in relation to local sunset time
    (Springer Verlag, 2014-08) Rastogi, R. G.; Chandra, H.; Janardhan, P.; Lan Hoang, Thai; Condori, Louis; Pant, T. K.; Prasad, D. S. V. V. D.; Reinisch, B.
    The paper describes the results of spread-F at low latitude stations around the world during the magnetic storm starting at 0130 UT on 22 January 2004. The storm can be divided into two phases, first phase up to 1000 UT when interplanetary magnetic field IMF-Bz was highly fluctuating around a small positive value and the second phase after a sudden large southward turning of IMF-Bz at 1030 UT. The first phase produced strong spread-F at Jicamarca, Sao Luis, and Ascension Island and caused complete inhibition of spread-F at Thumba and Waltair in India. It generated weak spread-F at Ho Chi Minh City in Vietnam and strong spread-F at Hainan and Chung Li. The strong spread-F at Hainan and Chung Li were caused by the positive IMF-Bz during the first phase of the storm and not by the negative pulse of IMF-Bz at 1000 UT.
    Palabras clave:Equatorial ionosphereSpace weatherGeomagnetic storm