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>

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.

scholarly journals Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

2000 ◽  
Vol 18 (4) ◽  
pp. 461-477 ◽  
Author(s):  
A. A. Namgaladze ◽  
M. Förster ◽  
R. Y. Yurik
Keyword(s):  
Numerical Model ◽  
Geomagnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Atmospheric Composition ◽  
Reference Level ◽  
Quiet Time ◽  
Ionospheric Storm ◽  
Low Latitudes ◽  
Composition Changes

Abstract. Current theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric field disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at fixed height under day-light conditions.Key words: Atmospheric composition and structure (thermosphere · composition and chemistry) · Ionosphere (ionosphere · atmosphere interactions; modelling and forecasting)

scholarly journals Role of neutral wind and storm time electric fields inferred from the storm time ionization distribution at low latitudes: in-situ measurements by Indian satellite SROSS-C2

2005 ◽  
Vol 23 (10) ◽  
pp. 3289-3299 ◽  
Author(s):  
P. Subrahmanyam ◽  
A. R. Jain ◽  
L. Singh ◽  
S. C. Garg
Keyword(s):  
Geomagnetic Storm ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Activity Period ◽  
High Solar Activity ◽  
Satellite Network ◽  
Neutral Winds ◽  
Weather Events ◽  
Low Latitudes ◽  
Time Changes

Abstract. Recently, there has been a renewal of interest in the study of the effects of solar weather events on the ionization redistribution and irregularity generation. The observed changes at low and equatorial latitudes are rather complex and are noted to be a function of location, the time of the storm onset and its intensity, and various other characteristics of the geomagnetic storms triggered by solar weather events. At these latitudes, the effects of geomagnetic storms are basically due to (a) direct penetration of the magnetospheric electric fields to low latitudes, (b) development of disturbance dynamo, (c) changes in atmospheric neutral winds at ionospheric level and (d) changes in neutral composition triggered by the storm time atmospheric heating. In the present study an attempt is made to further understand some of the observed storm time effects in terms of storm time changes in zonal electric fields and meridional neutral winds. For this purpose, observations made by the Retarding Potential Analyzer (RPA) payload on board the Indian satellite SROSS-C2 are examined for four prominent geomagnetic storm events that occurred during the high solar activity period of 1997-2000. Available simultaneous observations, from the GPS satellite network, are also used. The daytime passes of SROSS-C2 have been selected to examine the redistribution of ionization in the equatorial ionization anomaly (EIA) region. In general, EIA is observed to be weakened 12-24 h after the main phase onset (MPO) of the storm. The storm time behaviour inferred by SROSS-C2 and the GPS satellite network during the geomagnetic storm of 13 November 1998, for which simultaneous observations are available, is found to be consistent. Storm time changes in the delay of received GPS signals are noted to be ~1-3 m, which is a significant component of the total delay observed on a quiet day. An attempt is made to identify and delineate the effects of a) meridional neutral winds, b) the development of the ring currents and c) the disturbance dynamo electric fields on the low latitude ionization distribution. The weakening of the EIA is noted to be primarily due to the decrease in the eastward electric fields driving the equatorial fountain during the daytime. The meridional neutral winds are also noted to play an important role in redistribution of ionization in the EIA region. The present results demonstrate that storm time latitudinal distribution of ionization in this region can be better understood by taking into account the meridional winds in addition to E×B drifts.

scholarly journals Ionospheric storms at geophysically-equivalent sites – Part 1: Storm-time patterns for sub-auroral ionospheres

2009 ◽  
Vol 27 (4) ◽  
pp. 1679-1694 ◽  
Author(s):  
M. Mendillo ◽  
C. Narvaez
Keyword(s):  
Solar Cycle ◽  
Northern Hemisphere ◽  
Electric Fields ◽  
Geomagnetic Storms ◽  
Hemispheric Differences ◽  
Solar Cycles ◽  
Plasma Dynamics ◽  
Storm Effects ◽  
Typical Morphology ◽  
Minimum Solar Activity

Abstract. The systematic study of ionospheric storms has been conducted primarily with groundbased data from the Northern Hemisphere. Significant progress has been made in defining typical morphology patterns at all latitudes; mechanisms have been identified and tested via modeling. At higher mid-latitudes (sites that are typically sub-auroral during non-storm conditions), the processes that change significantly during storms can be of comparable magnitudes, but with different time constants. These include ionospheric plasma dynamics from the penetration of magnetospheric electric fields, enhancements to thermospheric winds due to auroral and Joule heating inputs, disturbance dynamo electrodynamics driven by such winds, and thermospheric composition changes due to the changed circulation patterns. The ~12° tilt of the geomagnetic field axis causes significant longitude effects in all of these processes in the Northern Hemisphere. A complementary series of longitude effects would be expected to occur in the Southern Hemisphere. In this paper we begin a series of studies to investigate the longitudinal-hemispheric similarities and differences in the response of the ionosphere's peak electron density to geomagnetic storms. The ionosonde stations at Wallops Island (VA) and Hobart (Tasmania) have comparable geographic and geomagnetic latitudes for sub-auroral locations, are situated at longitudes close to that of the dipole tilt, and thus serve as our candidate station-pair choice for studies of ionospheric storms at geophysically-comparable locations. They have an excellent record of observations of the ionospheric penetration frequency (foF2) spanning several solar cycles, and thus are suitable for long-term studies. During solar cycle #20 (1964–1976), 206 geomagnetic storms occurred that had Ap≥30 or Kp≥5 for at least one day of the storm. Our analysis of average storm-time perturbations (percent deviations from the monthly means) showed a remarkable agreement at both sites under a variety of conditions. Yet, small differences do appear, and in systematic ways. We attempt to relate these to stresses imposed over a few days of a storm that mimic longer term morphology patterns occurring over seasonal and solar cycle time spans. Storm effects versus season point to possible mechanisms having hemispheric differences (as opposed to simply seasonal differences) in how solar wind energy is transmitted through the magnetosphere into the thermosphere-ionosphere system. Storm effects versus the strength of a geomagnetic storm may, similarly, be related to patterns seen during years of maximum versus minimum solar activity.

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)

Solar cycle effects on the electric fields in the equatorial ionosphere

1977 ◽  
Vol 82 (32) ◽  
pp. 5257-5261 ◽  
Author(s):  
R. F. Woodman ◽  
R. G. Rastogi ◽  
C. Calderon
Keyword(s):  
Solar Cycle ◽  
Electric Fields ◽  
Equatorial Ionosphere

scholarly journals RF-Carpets that Compress Ions to High Density Beams

2015 ◽  
Vol 21 (S4) ◽  
pp. 84-89
Author(s):  
H. Wollnik ◽  
F. Arai ◽  
Y. Ito ◽  
P. Schury ◽  
M. Wada
Keyword(s):  
Phase Space ◽  
Electric Field ◽  
Electric Fields ◽  
Ion Beams ◽  
High Density ◽  
Ion Density ◽  
Field Lines

AbstractIons that are moved by electric fields in gases follow quite exactly the electric field lines since these ions have substantially lost their kinetic energies in collisions with gas atoms or molecules and so carry no momenta. Shaping the electric fields appropriately the phase space such ion beams occupy can be reduced and correspondingly the ion density of beams be increased.

scholarly journals Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

2002 ◽  
Vol 20 (12) ◽  
pp. 1977-1985 ◽  
Author(s):  
R. Sridharan ◽  
C. V. Devasia ◽  
N. Jyoti ◽  
Diwakar Tiwari ◽  
K. S. Viswanathan ◽  
...  
Keyword(s):  
Electric Fields ◽  
Solar Eclipse ◽  
Equatorial Ionosphere ◽  
Hf Radar ◽  
F Region ◽  
Large Enhancement ◽  
Temporal Structures ◽  
E Region ◽  
Field Lines ◽  
Electric Fields And Currents

Abstract. The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N), India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i) the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii) significant increase in h' F immediately following the eclipse and (iii) distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F) rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities)

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