Investigation of Unusual Solar Flare Effect on the Global Ionospheric Current System

N. M.N. Annadurai, N. S.A. Hamid, Y. Yamazaki, Akimasa Yoshikawa

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

In this paper, we present our investigation of geomagnetic crochets observed following the X-class solar flare events on 9 August 2011 (X6.9) and 24 September 2011 (X1.4). Both events occurred during geomagnetically quiet times (Kp ≤ 3). The analysis of the geomagnetic crochets near the magnetic equator revealed very different responses in the ionospheric currents between these two events. During the 9 August 2011 event, a reduction of the eastward equatorial electrojet was observed in all daytime stations studied, while the daytime eastward equatorial electrojet was observed to enhance during the 24 September 2011 event. A spherical harmonic analysis was applied to the observations from nearly 160 ground stations at middle and low latitudes to derive the equivalent ionospheric current system for the geomagnetic crochets as well as background solar-quiet (Sq) variations for both events. The equivalent current system of the geomagnetic crochets for the 24 September 2011 event showed a similar pattern with the background Sq current system and thus can be attributed to the enhancement of Sq currents. However, the crochet current system for the 9 August 2011 event revealed a different pattern from the background Sq current system in both Northern and Southern Hemispheres. It is suggested that unusual geomagnetic crochets during the 9 August 2011 event may be dominated by the ionospheric currents at D-region altitudes.

Original languageEnglish
Pages (from-to)8599-8609
Number of pages11
JournalJournal of Geophysical Research: Space Physics
Volume123
Issue number10
DOIs
Publication statusPublished - Oct 1 2018

Fingerprint

D region
ionospheric currents
Harmonic analysis
solar flares
electrojet
harmonic analysis
spherical harmonics
equatorial electrojet
Southern Hemisphere
Northern Hemisphere
daytime
effect
magnetic equator
ground stations
tropical regions
station
stations

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)
  • Palaeontology

Cite this

Investigation of Unusual Solar Flare Effect on the Global Ionospheric Current System. / Annadurai, N. M.N.; Hamid, N. S.A.; Yamazaki, Y.; Yoshikawa, Akimasa.

In: Journal of Geophysical Research: Space Physics, Vol. 123, No. 10, 01.10.2018, p. 8599-8609.

Research output: Contribution to journalArticle

Annadurai, N. M.N. ; Hamid, N. S.A. ; Yamazaki, Y. ; Yoshikawa, Akimasa. / Investigation of Unusual Solar Flare Effect on the Global Ionospheric Current System. In: Journal of Geophysical Research: Space Physics. 2018 ; Vol. 123, No. 10. pp. 8599-8609.
@article{20e2a961628d4f65a111684cf4cead57,
title = "Investigation of Unusual Solar Flare Effect on the Global Ionospheric Current System",
abstract = "In this paper, we present our investigation of geomagnetic crochets observed following the X-class solar flare events on 9 August 2011 (X6.9) and 24 September 2011 (X1.4). Both events occurred during geomagnetically quiet times (Kp ≤ 3). The analysis of the geomagnetic crochets near the magnetic equator revealed very different responses in the ionospheric currents between these two events. During the 9 August 2011 event, a reduction of the eastward equatorial electrojet was observed in all daytime stations studied, while the daytime eastward equatorial electrojet was observed to enhance during the 24 September 2011 event. A spherical harmonic analysis was applied to the observations from nearly 160 ground stations at middle and low latitudes to derive the equivalent ionospheric current system for the geomagnetic crochets as well as background solar-quiet (Sq) variations for both events. The equivalent current system of the geomagnetic crochets for the 24 September 2011 event showed a similar pattern with the background Sq current system and thus can be attributed to the enhancement of Sq currents. However, the crochet current system for the 9 August 2011 event revealed a different pattern from the background Sq current system in both Northern and Southern Hemispheres. It is suggested that unusual geomagnetic crochets during the 9 August 2011 event may be dominated by the ionospheric currents at D-region altitudes.",
author = "Annadurai, {N. M.N.} and Hamid, {N. S.A.} and Y. Yamazaki and Akimasa Yoshikawa",
year = "2018",
month = "10",
day = "1",
doi = "10.1029/2018JA025601",
language = "English",
volume = "123",
pages = "8599--8609",
journal = "Journal of Geophysical Research",
issn = "0148-0227",
number = "10",

}

TY - JOUR

T1 - Investigation of Unusual Solar Flare Effect on the Global Ionospheric Current System

AU - Annadurai, N. M.N.

AU - Hamid, N. S.A.

AU - Yamazaki, Y.

AU - Yoshikawa, Akimasa

PY - 2018/10/1

Y1 - 2018/10/1

N2 - In this paper, we present our investigation of geomagnetic crochets observed following the X-class solar flare events on 9 August 2011 (X6.9) and 24 September 2011 (X1.4). Both events occurred during geomagnetically quiet times (Kp ≤ 3). The analysis of the geomagnetic crochets near the magnetic equator revealed very different responses in the ionospheric currents between these two events. During the 9 August 2011 event, a reduction of the eastward equatorial electrojet was observed in all daytime stations studied, while the daytime eastward equatorial electrojet was observed to enhance during the 24 September 2011 event. A spherical harmonic analysis was applied to the observations from nearly 160 ground stations at middle and low latitudes to derive the equivalent ionospheric current system for the geomagnetic crochets as well as background solar-quiet (Sq) variations for both events. The equivalent current system of the geomagnetic crochets for the 24 September 2011 event showed a similar pattern with the background Sq current system and thus can be attributed to the enhancement of Sq currents. However, the crochet current system for the 9 August 2011 event revealed a different pattern from the background Sq current system in both Northern and Southern Hemispheres. It is suggested that unusual geomagnetic crochets during the 9 August 2011 event may be dominated by the ionospheric currents at D-region altitudes.

AB - In this paper, we present our investigation of geomagnetic crochets observed following the X-class solar flare events on 9 August 2011 (X6.9) and 24 September 2011 (X1.4). Both events occurred during geomagnetically quiet times (Kp ≤ 3). The analysis of the geomagnetic crochets near the magnetic equator revealed very different responses in the ionospheric currents between these two events. During the 9 August 2011 event, a reduction of the eastward equatorial electrojet was observed in all daytime stations studied, while the daytime eastward equatorial electrojet was observed to enhance during the 24 September 2011 event. A spherical harmonic analysis was applied to the observations from nearly 160 ground stations at middle and low latitudes to derive the equivalent ionospheric current system for the geomagnetic crochets as well as background solar-quiet (Sq) variations for both events. The equivalent current system of the geomagnetic crochets for the 24 September 2011 event showed a similar pattern with the background Sq current system and thus can be attributed to the enhancement of Sq currents. However, the crochet current system for the 9 August 2011 event revealed a different pattern from the background Sq current system in both Northern and Southern Hemispheres. It is suggested that unusual geomagnetic crochets during the 9 August 2011 event may be dominated by the ionospheric currents at D-region altitudes.

UR - http://www.scopus.com/inward/record.url?scp=85054348649&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85054348649&partnerID=8YFLogxK

U2 - 10.1029/2018JA025601

DO - 10.1029/2018JA025601

M3 - Article

VL - 123

SP - 8599

EP - 8609

JO - Journal of Geophysical Research

JF - Journal of Geophysical Research

SN - 0148-0227

IS - 10

ER -