Equatorial ionosphere-thermosphere system during geomagnetic storms

2003 ◽  
pp. 185-203 ◽  
Author(s):  
J. Hanumath Sastri ◽  
R. Sridharan ◽  
Tarun Kumar Pant
Keyword(s):  
Geomagnetic Storms ◽  
Equatorial Ionosphere

scholarly journals Role of the magnetospheric and ionospheric currents in the generation of the equatorial scintillations during geomagnetic storms

2004 ◽  
Vol 22 (9) ◽  
pp. 3195-3202 ◽  
Author(s):  
L. Z. Biktash
Keyword(s):  
Solar Wind ◽  
Electric Fields ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Equatorial Ionosphere ◽  
Experimental Investigations ◽  
Polar Regions ◽  
Ionospheric Currents ◽  
Geomagnetic Variations ◽  
Activity Effect

Abstract. The equatorial ionosphere parameters, Kp, Dst, AU and AL indices characterized contribution of different magnetospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the geomagnetic activity effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict near 70% of scintillations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of electron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind - magnetosphere - ionosphere during magnetic storms have progressed greatly. According to present view, the intensity of the electric fields and currents at the polar regions, as well as the magnetospheric ring current intensity, are strongly dependent on the variations of the interplanetary magnetic field. The magnetospheric ring current cannot directly penetrate the equatorial ionosphere and because of this difficulties emerge in explaining its relation to scintillation activity. On the other hand, the equatorial scintillations can be observed in the absence of the magnetospheric ring current. It is shown that in addition to Aarons' criteria for the prediction of the ionospheric scintillations, models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere currents and the solar wind.

Local time dependant response of Indian equatorial ionosphere to the moderate geomagnetic storms

2007 ◽  
Vol 39 (8) ◽  
pp. 1304-1312 ◽  
Author(s):  
S. Tulasi Ram ◽  
P.V.S. Rama Rao ◽  
D.S.V.V.D. Prasad ◽  
K. Niranjan ◽  
R. Sridharan ◽  
...  
Keyword(s):  
Local Time ◽  
Geomagnetic Storms ◽  
Equatorial Ionosphere

Ionospheric dynamic and coupling processes during geomagnetic storms

2020 ◽  
Author(s):  
Chaosong Huang
Keyword(s):  
Electric Fields ◽  
Geomagnetic Storms ◽  
Equatorial Ionosphere ◽  
Ion Composition ◽  
Hemispheric Differences ◽  
Ion Density ◽  
Ion Drift ◽  
Low Latitudes ◽  
Coupling Processes ◽  
Ionospheric Dynamics

<p>Geomagnetic storms cause the largest disturbances in the ionosphere-thermosphere system. We use measurements with satellites and ground based radars to study storm-induced variations in ionospheric plasma drift, ion density, and ion composition at low latitudes. It is found that the storm-time change of ion drift velocity in the equatorial ionosphere can reach 200-300 m/s, the change of ion density can be one or two orders of magnitude, and the change of ion composition can be 50-80%. These extremely large changes in the ionosphere can last for several hours or even a few days during the main and recovery phases of magnetic storms. The longitudinal, latitudinal and hemispheric differences of storm-time ionospheric disturbances are analyzed from measurements of multiple satellites or radar chain. Very long, continuous penetration of interplanetary electric fields to the equatorial ionosphere for 6 or even 14 hours are observed, and the time when disturbance dynamo electric fields become dominant is identified. The interplay of penetration, shielding, and disturbance dynamo electric fields in the storm-time ionosphere will be addressed. Mechanisms responsible for storm-time ionospheric dynamics will be discussed.</p>

The solar wind control of the equatorial ionosphere dynamics during geomagnetic storms

2008 ◽  
Vol 41 (4) ◽  
pp. 562-568 ◽  
Author(s):  
L.Z. Biktash ◽  
T. Maruyama ◽  
K. Nozaki
Keyword(s):  
Solar Wind ◽  
Geomagnetic Storms ◽  
Equatorial Ionosphere

scholarly journals Ionospheric <i>fo</i>F2 anomalies during some intense geomagnetic storms

2005 ◽  
Vol 23 (7) ◽  
pp. 2487-2499 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Geomagnetic Storms ◽  
Early Morning ◽  
Equatorial Ionosphere ◽  
Storm Event ◽  
Ionospheric Disturbances ◽  
High Latitudes ◽  
Negative Effects ◽  
Local Effects ◽  
Positive Effects ◽  
Low Latitudes

Abstract. The global evolutions of foF2 anomalies were examined for three very intense geomagnetic storms, namely the Halloween events of October-November 2003 (Event X, 29–30 October 2003, Dst –401 nT; Event Y, 20–21 November 2003, Dst –472 nT), and the largest Dst storm (Event Z, 13–14 March 1989, Dst –589 nT). For Event X, troughs (negative storms) were clearly seen for high northern and southern latitudes. For northern midlatitudes as well as for low latitudes, there were very strong positive effects on 29 October 2003, followed by negative effects the next day. For Event Y, there were no troughs in NH high latitudes for morning and evening hours but there were troughs for night. For midlatitudes and low latitudes, some longitudes showed strong negative effects in the early morning as expected, but some longitudes showed strong positive effects at noon and in the evening hours. Thus, there were many deviations from the model patterns. The deviations were erratic, indicating considerable local effects superposed on general patterns. A disconcerting feature was the presence of strong positive effects during the 24 h before the storm commencement. Such a feature appears only in the 24 h before the geomagnetic storm commencement but not earlier. If genuine, these could imply a prediction potential with a 24-h antecedence. For Event Z (13–14 March 1989, equinox), all stations (all latitudes and longitudes) showed a very strong "negative storm" in the main phase, and no positive storms anywhere. Keywords. Ionosphere (Equatorial ionosphere – Ionospheric disturbances – Mid-latitude Ionosphere – Polar ionosphere)

scholarly journals Observations of GPS ionospheric scintillations over Wuhan during geomagnetic storms

2006 ◽  
Vol 24 (6) ◽  
pp. 1581-1590 ◽  
Author(s):  
G. Li ◽  
B. Ning ◽  
W. Wan ◽  
B. Zhao
Keyword(s):  
Geomagnetic Storms ◽  
Equatorial Ionosphere ◽  
The Other ◽  
Small Scale ◽  
Plasma Drift ◽  
Equatorial Ionization Anomaly ◽  
Spread F ◽  
Ionospheric Scintillations ◽  
Sporadic E Layer ◽  
Sporadic E

Abstract. During the two geomagnetic storms which occurred on 1 October 2002 and 22 January 2004, the strong ionospheric scintillations of the GPS L1 band were observed at Wuhan station (30.6° N, 114.4° E, 45.8° Dip), which is situated near the northern crest of the equatorial ionosphere anomaly. We found that the intense scintillations were associated with the main phases of the storms and were co-located with the enhancement of the equatorial ionization anomaly (EIA); the co-existence of large- and small-scale irregularities at post-midnight was also found. The results may be relevant regarding the influence of the equatorial ionospheric eastward electric field during geomagnetic storms. On the other hand, GPS L1 band scintillations were not observed during the other two similar storms on 16 July 2003 and 20 November 2003. One of the reasons is probably that the sporadic E layer observed at the storms inhibited the generation of spread F by changing the Pedersen conductivity and suppressing the upward plasma drift.

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