Response of ionospheric disturbance dynamo and electromagnetic induction during geomagnetic storm

During geomagnetic storms, the direct penetration of magnetospheric convection electric field and the ionospheric disturbance dynamo (IDD) take place in the ionosphere. In this paper, we studied variability of IDD and electromagnetic induction (EMI) at different latitudinal sectors during the geomagnetic storms on 7 and 8 September 2002 and 20 and 21 November 2003 with high solar wind speed due to coronal mass ejection. This investigation employs geomagnetic field components (H and Z), the geomagnetic indices (Dst, AL, and AU), solar wind speed (Vx), and interplanetary magnetic field (Bz). It was observed that the H component of geomagnetic field decreases across latitudes, and varies with Vx, Bz, Dst, AL, and AU indices throughout the difference phases of the storm. Our result demonstrated the dominance of the IDD during the nighttime compared to the daytime. This implies that neutral dynamic wind is greater at night than during the day. Higher ratio ΔZ/ΔH is observed at nighttime because of the reduction on the E region conductivity, which allowed F region electric fields to dominate.

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Low frequency geomagnetic field variations at Dome C (Antarctica)

Annales Geophysicae ◽

10.5194/angeo-21-923-2003 ◽

2003 ◽

Vol 21 (4) ◽

pp. 923-932 ◽

Cited By ~ 5

Author(s):

S. Lepidi ◽

L. Cafarella ◽

P. Francia ◽

A. Meloni ◽

P. Palangio ◽

...

Keyword(s):

Solar Wind ◽

Wind Speed ◽

Geomagnetic Field ◽

Solar Wind Speed ◽

Low Frequency ◽

Mhd Waves ◽

Polar Cap ◽

Ionospheric Currents ◽

Terra Nova Bay ◽

Terra Nova

Abstract. We conduct an analysis of the geomagnetic field variations recorded at the new Antarctic station Dome C, located very close to the geomagnetic pole, which has been operating for approximately one month during the 1999–2000 campaign. We also perform a comparison with simultaneous measurements at the Italian Antarctic station Terra Nova Bay, in order to investigate the spatial extension of the phenomena observed at very high latitude. Our results show that between the two stations the daily variation is similar and the fluctuations with f ~ 1 mHz are coherent, provided that in both cases the comparison is made between geographically oriented components, suggesting that ionospheric currents related to the geographic position, more than field-aligned currents, are responsible for the lowest frequency variations; conversely, higher frequency (Pc5) fluctuations are substantially decoupled between the two stations. We also found that at Dome C the fluctuation power in the 0.55–6.7 mHz frequency band is well related with the solar wind speed during the whole day and that at Terra Nova Bay the correlation is also high, except around local geomagnetic noon, when the station approaches the polar cusp. These results indicate that the solar wind speed control of the geomagnetic field fluctuation power is very strict in the polar cap and less important close to the polar cusp.Key words. Magnetospheric physics (MHD waves and instabilities; Polar cap phenomena; Solar wind-magnetosphere interactions)

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A Statistical Study on DH CMEs and Its Geoeffectiveness

ISRN Astronomy and Astrophysics ◽

10.1155/2013/129426 ◽

2013 ◽

Vol 2013 ◽

pp. 1-13 ◽

Cited By ~ 4

Author(s):

V. Vasanth ◽

S. Umapathy

Keyword(s):

Magnetic Field ◽

Solar Wind ◽

Wind Speed ◽

Field Component ◽

Geomagnetic Storms ◽

Solar Wind Speed ◽

Type Ii ◽

Dst Index ◽

Long Duration ◽

Type Ii Bursts

A detailed investigation on geoeffectiveness of CMEs associated with DH-type-II bursts observed during 1997–2008 is presented. The collected sample events are divided into two groups based on their association with CMEs related to geomagnetic storms Dst ≤−50 nT, namely, (i) geoeffective events and (ii) nongeoeffective events. We found that the geoeffective events have high starting frequency, low ending frequency, long duration, wider bandwidth, energetic flares, and CMEs than nongeoeffective events. The geoeffective events are found to have intense geomagnetic storm with mean Dst index (−150 nT). There exists good correlation between the properties of CMEs and flares for geoeffective events, while no clear correlation exists for nongeoeffective events. There exists a weak correlation for geoeffective events between (i) CME speed and Dst index (R=-0.51) and good correlation between (i) CME speed and solar wind speed (R=0.60), (ii) Dst index and solar wind speed (R=-0.64), and (iii) Dst index and southward magnetic field component (Bz) (R=0.80). From our study we conclude that the intense and long duration southward magnetic field component (Bz) and fast solar wind speed are responsible for geomagnetic storms, and the geomagnetic storms weakly depend on CME speed. About 22% (50/230) of the DH-type-II bursts are associated with geomagnetic storms. Therefore the DH-type-II bursts associated with energetic flares and CMEs are good indicator of geomagnetic storms.

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Study of solar flares associated with Geoeffective CMEs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921318001072 ◽

2018 ◽

Vol 13 (S340) ◽

pp. 163-164

Author(s):

Veena Choithani ◽

Rajmal Jain ◽

Duggirala Pallamraju

Keyword(s):

Solar Wind ◽

Wind Speed ◽

Solar Flare ◽

Coronal Mass Ejections ◽

Solar Flares ◽

Geomagnetic Storms ◽

Solar Wind Speed ◽

Dst Index ◽

In The Beginning ◽

The Imf

AbstractWe study 30 solar flare events associated with coronal mass ejections (CMEs) that produced geomagnetic storms as measured in Dst index. Our study reveals that the magnitude of Dst index is significantly associated with maximum solar wind speed, peak of Bz component of the IMF and the product of peak Bz and solar wind speed (minimum and maximum). From our investigations, it can be inferred that CMEs travel with higher speed in the beginning and their speed reduces as they reach L1 location.

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A superposed epoch analysis of geomagnetic storms

Annales Geophysicae ◽

10.1007/s00585-994-0612-4 ◽

1994 ◽

Vol 12 (7) ◽

pp. 612-624 ◽

Cited By ~ 41

Author(s):

J. R. Taylor ◽

M. Lester ◽

T. K. Yeoman

Keyword(s):

Solar Wind ◽

Wind Speed ◽

High Speed ◽

Geomagnetic Storms ◽

Solar Wind Speed ◽

Magnetic Activity ◽

Wind Pressure ◽

Superposed Epoch Analysis ◽

Controlling Parameter ◽

Epoch Analysis

Abstract. A superposed epoch analysis of geomagnetic storms has been undertaken. The storms are categorised via their intensity (as defined by the Dst index). Storms have also been classified here as either storm sudden commencements (SSCs) or storm gradual commencements (SGCs, that is all storms which did not begin with a sudden commencement). The prevailing solar wind conditions defined by the parameters solar wind speed (vsw), density (ρsw) and pressure (Psw) and the total field and the components of the interplanetary magnetic field (IMF) during the storms in each category have been investigated by a superposed epoch analysis. The southward component of the IMF, appears to be the controlling parameter for the generation of small SGCs (-100 nT< minimum Dst ≤ -50 nT for ≥ 4 h), but for SSCs of the same intensity solar wind pressure is dominant. However, for large SSCs (minimum Dst ≤ -100 nT for ≥ 4 h) the solar wind speed is the controlling parameter. It is also demonstrated that for larger storms magnetic activity is not solely driven by the accumulation of substorm activity, but substantial energy is directly input via the dayside. Furthermore, there is evidence that SSCs are caused by the passage of a coronal mass ejection, whereas SGCs result from the passage of a high speed/ slow speed coronal stream interface. Storms are also grouped by the sign of Bz during the first hour epoch after the onset. The sign of Bz at t = +1 h is the dominant sign of the Bz for ~24 h before the onset. The total energy released during storms for which Bz was initially positive is, however, of the same order as for storms where Bz was initially negative.

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Geomagnetic field H, Z, and electromagnetic induction features of coronal mass ejections in association with geomagnetic storm at African longitudes

Canadian Journal of Physics ◽

10.1139/cjp-2017-0460 ◽

2018 ◽

Vol 96 (6) ◽

pp. 654-663

Author(s):

E.O. Falayi ◽

J.O. Adepitan ◽

O.A. Oyebanjo

Keyword(s):

Electric Fields ◽

Geomagnetic Field ◽

Electromagnetic Induction ◽

Geomagnetic Disturbance ◽

Wavelet Spectrum ◽

Magnetospheric Convection ◽

Cycle 24 ◽

Electric Fields And Currents ◽

Minimum Disturbance ◽

Derivatives Of

The largest geomagnetic disturbance caused by a coronal mass ejection (CME) of solar cycle 24 recorded on both 17 March and 22 June 2015 with minimum disturbance storm time values of −223 and −195 nT, respectively, was investigated. This study examines the effect of CME on Earth’s geomagnetic field, which includes the time derivatives of horizontal (H) and vertical (Z) components of the geomagnetic field and the rate of induction ΔZ/ΔH at African longitudes (AAE, MBO, HBK, HER, and TAM). The results demonstrated enhancement of dH/dt and dZ/dt in the daytime over the equatorial zone (AAE and MBO) and mid-latitudes (TAM, HER, and HBK) on 17 March 2015. Nighttime enhancement was observed on 22 June 2015 over the equatorial zones and mid-latitudes. Wavelet spectrum approach is used to investigate ΔZ/ΔH variation observed at AAE, MBO, HBK, HER, and TAM. The CME may have influence on time derivatives of geomagnetic field H, Z, and electromagnetic induction at the African longitudes, which may be associated with perturbations in electric fields and currents in the equatorial and low-latitude magnetic field linked with the changes in magnetospheric convection.

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