J. W. MacDougall

Western University

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P. T. Jayachandran

University of New Brunswick

W. K. Hocking

Western University

A. H. Manson

University of Saskatchewan

I. S. Batista

National Institute for Space Research

C. E. Meek

University of Saskatchewan

M. A. Abdu

National Institute for Space Research

K. Igarashi

Tokyo University of Marine Science and Technology

P. Prikryl

University of New Brunswick

S. C. Mushini

University of Calgary

T. Thayaparan

Defence Research and Development Canada

Cooperative Institutions

University of Michigan–Ann Arbor

University of California, Berkeley

School of International Relations

University of Saskatchewan

National Institute for Space Research

Western University

Harvard University

Cornell University

Stanford University

Massachusetts Institute of Technology

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Effects of the major geomagnetic storms of October 2003 on the equatorial and low‐latitude F region in two longitudinal sectors

Journal of Geophysical Research Atmospheres (2005)

Y. Sahai P. R. Fagundes F. Becker‐Guedes M.J.A. Bolzan J. R. Abalde

The intense modifications in the ionosphere‐thermosphere system in the equatorial and low‐latitude regions associated with the dynamic and electrodynamic coupling from high to low latitudes and chemical changes during geomagnetic storms are important space weather issues. In the second half of October 2003, the intense solar activity resulted in one intense and two major geomagnetic storms on 29 and 30 October. In this paper we present and discuss the ionospheric sounding observations carried out from Palmas and São José dos Campos, Brazil (the Brazilian sector), and Ho Chi Minh City, Vietnam, and Okinawa, Japan (the East Asian sector), during these storms. The two sectors are separated by about 12 hours in local time (so while one sector is in daytime, the other one is in nighttime) and provide valuable information related to the storm‐time longitudinal differences. Copious storm‐time changes were observed in both sectors. It should be pointed out that the two longitudinal sectors investigated in the present study clearly show the global nature of the storm‐time effects. However, the responses to the storm‐time effects are also associated with the local time in the two sectors. The present investigations show that there are both similarities and differences in the storm‐time response in the two sectors. During the storm main phases, with sharp decreases of the Dst index, both sectors showed (dusk or dawn periods) fast uplifting of the F layer associated with magnetospheric electric field penetration. Although in the East Asian sector, Ho Chi Minh City and Okinawa are located fairly close in longitude, with only 2 hour difference in local lime, on occasions the storm‐time responses have been very different. Some differences in the latitudinal response of the F region were also observed in the two sectors. Both positive and negative storm phases have been observed at all the four stations. A comparison of the ionospheric parameters obtained from the TIMEGCM model runs and the observed ionospheric parameters at the four stations shows a reasonable agreement during the quiet periods. During the geomagnetic disturbance period, when there were sharp decreases in Dst , some of the observed rapid uplifts of the F region peak heights are not reproduced by the model results. Also, sometimes the model foF2 results differ considerably from the observed foF2 variations. The period investigated represents an extreme storm situation for validation of the model and points to ways in which the model might be improved in the future.

Low latitude

Local time

10.1029/2004ja010999

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Citations (74)

Sources for Traveling Ionospheric Disturbances

AGU Fall Meeting Abstracts (2009)

J. W. MacDougall P. T. Jayachandran

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Ionospheric Anomalies in the Polar Cap and at Mid-Latitudes Revealed by Digital Ionosondes and GPS Receivers

AGUSM (2009)

Dimitry Pokhotelov Thayyil Jayachandran J. W. MacDougall Cathryn N. Mitchell

Polar cap

Middle latitudes

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Ionospheric response to the corotating interaction region–driven geomagnetic storm of October 2002

Journal of Geophysical Research Atmospheres (2009)

Dimitry Pokhotelov Cathryn N. Mitchell P. T. Jayachandran J. W. MacDougall M. H. Denton

Unlike the geomagnetic storms produced by coronal mass ejections (CMEs), the storms generated by corotating interaction regions (CIRs) are not manifested by dramatic enhancements of the ring current. The CIR‐driven storms are however capable of producing other phenomena typical for the magnetic storms such as relativistic particle acceleration, enhanced magnetospheric convection and ionospheric heating. This paper examines ionospheric plasma anomalies produced by a CIR‐driven storm in the middle‐ and high‐latitude ionosphere with a specific focus on the polar cap region. The moderate magnetic storm which took place on 14–17 October 2002 has been used as an example of the CIR‐driven event. Four‐dimensional tomographic reconstructions of the ionospheric plasma density using measurements of the total electron content along ray paths of GPS signals allow us to reveal the large‐scale structure of storm‐induced ionospheric anomalies. The tomographic reconstructions are compared with the data obtained by digital ionosonde located at Eureka station near the geomagnetic north pole. The morphology and dynamics of the observed ionospheric anomalies is compared qualitatively to the ionospheric anomalies produced by major CME‐driven storms. It is demonstrated that the CIR‐driven storm of October 2002 was able to produce ionospheric anomalies comparable to those produced by CME‐driven storms of much greater Dst magnitude. This study represents an important step in linking the tomographic GPS reconstructions with the data from ground‐based network of digital ionosondes.

Ionosonde

Space Weather

10.1029/2009ja014216

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Citations (19)

Comparison of plasma flow velocities determined by the ionosonde Doppler drift technique, SuperDARN radars, and patch motion

Radio Science (1995)

I. F. Grant J. W. MacDougall J. M. Ruohoniemi W. A. Bristow G. J. Sofko

We compare measurements of polar cap ionospheric plasma flow over Resolute Bay, Canada, made by a digital ionosonde using the Doppler drift technique with simultaneous measurements at the same location made by the first operational pair of SuperDARN HF radars. During the 3‐hour comparison interval the flow varied widely in direction and from 100 to 600 m/s in speed. The two measurement techniques show very good agreement for both the speed and direction of flow for nearly all of the samples in the interval. The difference between the velocities determined by the two techniques has a scatter of about ±35° in direction and ±30% in speed, with no systematic difference above the level of the scatter. The few samples which strongly disagreed were usually associated with strong spatial structure in the flow pattern measured by SuperDARN in the vicinity of the comparison point. The drift speed measured by the ionosonde was independently verified by observing the time taken for polar cap F layer ionization patches to drift between ionosondes sited at Eureka and Resolute Bay. These results confirm that the speed and direction of the polar cap ionospheric convection can be reliably monitored by the ionosonde Doppler drift technique.

Ionosonde

Ionogram

Ionospheric sounding

10.1029/95rs00831

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Citations (94)

Central polar cap convection response to short duration southward Interplanetary Magnetic Field

Annales Geophysicae (2000)

P. T. Jayachandran J. W. MacDougall

Abstract. Central polar cap convection changes associated with southward turnings of the Interplanetary Magnetic Field (IMF) are studied using a chain of Canadian Advanced Digital Ionosondes (CADI) in the northern polar cap. A study of 32 short duration (~1 h) southward IMF transition events found a three stage response: (1) initial response to a southward transition is near simultaneous for the entire polar cap; (2) the peak of the convection speed (attributed to the maximum merging electric field) propagates poleward from the ionospheric footprint of the merging region; and (3) if the change in IMF is rapid enough, then a step in convection appears to start at the cusp and then propagates antisunward over the polar cap with the velocity of the maximum convection. On the nightside, a substorm onset is observed at about the time when the step increase in convection (associated with the rapid transition of IMF) arrives at the polar cap boundary.Key words: Ionosphere (plasma convection; polar ionosphere) - Magnetospheric physics (solar wind - magnetosphere interaction)

Substorm

10.1007/s00585-000-0887-z

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Citations (14)

Distributions of the irregularities which produce ionospheric scintillations

Journal of Atmospheric and Terrestrial Physics (1981)

J. W. MacDougall

10.1016/0021-9169(81)90093-3

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Citations (16)

Polar cap influx

Annales Geophysicae (2005)

J. W. MacDougall P. T. Jayachandran

Abstract. This study uses digital ionosonde data from a cusp latitude station (Cambridge Bay, 77° CGM lat.) to study the convection into the polar cap. Days when the IMF magnetic field was relatively steady were used. On many days it was possible to distinguish an interval near noon MLT when the ionosonde data had a different character from that at earlier and later times. Based on our data, and other published measurements, we used the interval 10:00-13:00 MLT as the cusp interval and calculated the convection into the polar cap in this interval. The integrated convection accounted for only ~1/3 of the open polar cap flux. If the convection through the prenoon/postnoon regions on either side of the cusp was calculated the remaining 2/3 of the flux could be accounted for. The characteristics of the prenoon/postnoon regions were different from the cusp region, and we attribute this to transient flank merging versus more steady frontside merging for the cusp. Keywords. Ionosphere (Plasma convection) Magnetospheric physics (Polar cap phenomenon)

Ionosonde

Noon

10.5194/angeo-23-1755-2005

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Effects of a "day-time" substorm on the ionosphere and radio propagation

cosp (2008)

Donat Blagoveshchenskiy J. W. MacDougall Aleksei Kalishin

Substorm

Universal Time

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A top to bottom evaluation of IRI 2007 within the polar cap

Journal of Geophysical Research Space Physics (2014)

David R. Themens P. T. Jayachandran M. J. Nicolls J. W. MacDougall

Abstract Monthly median values of ionospheric peak height (hmF 2 ) and density (NmF 2 ), derived from ionosonde measurements at four Canadian High Arctic Ionospheric Network (CHAIN) stations situated within the polar cap and Auroral Oval, are used to evaluate the performance of the International Reference Ionosphere (IRI) 2007 empirical ionospheric model during the recent solar minimum between 2008 and 2010. This analysis demonstrates notable differences between IRI and ionosonde NmF 2 diurnal and seasonal behavior over the entire period studied, where good agreement is found during summer periods but otherwise errors in excess of 50% were prevalent, particularly during equinox periods. hmF 2 is found to be marginally overestimated during winter and equinox nighttime, while also being underestimated during summer and equinox daytime by in excess of 25%. These errors are shown to be related to significant mismodeling of the M(3000)F 2 propagation factor. The ionospheric bottomside thickness parameter (B0) is also evaluated using ionosonde measurements. It is found that both of the IRI's internal B0 models significantly misrepresent both seasonal and diurnal variations in bottomside thickness when compared to ionosonde observations, where errors at times exceed 40%. A comparison is also presented between IRI and Resolute (74.75N, 265.00E) Advanced Modular Incoherent Scatter Radar (AMISR)‐derived topside thickness. It is found in this comparison that the IRI is capable of modeling ionospheric topside thickness exceptionally well during winter and summer periods but fails to represent significant diurnal variability during the equinoxes and seasonal variations.

Polar cap

10.1002/2014ja020052

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Citations (62)